The Complete Guide to

WIRING Updated 8th Edition

Current with 2020 —2023 Electrical Codes

© 2021 Quarto Publishing Group USA Inc. Library of Congress Cataloging-in-Publication Data Available

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ISBN: 978-0-7603-7151-0

Digital edition published in 2021

eISBN: 978-0-7603-7152-7

Black + Decker: The Complete Guide to Wiring, 8th Edition

Created by: The Editors of Cool Springs Press, in cooperation with BLACK+DECKER. BLACK+DECKER and the BLACK+DECKER logo are
trademarks of The Black & Decker Corporation and are used under license. All rights reserved.

NOTICE TO READERS
For safety, use caution, care, and good judgment when following the procedures described in this book. The publisher and
BLACK+DECKER cannot assume responsibility for any damage to property or injury to persons as a result of misuse of the
information provided.
The techniques shown in this book are general techniques for various applications. In some instances, additional
techniques not shown in this book may be required. Always follow manufacturers’ instructions included with products,
since deviating from the directions may void warranties. The projects in this book vary widely as to skill levels required:
some may not be appropriate for all do-it-yourselfers, and some may require professional help.
Consult your local building department for information on building permits, codes, and other laws as they apply to
your project.
The Complete Guide 9
to Wiring 8th Edition

Introduction 7

WORKING SAFELY WITH WIRING 9

How Electricity Works 10 16 20

Glossary of Electrical Terms 14

Understanding Electrical Circuits 16
Grounding & Polarization 18
Home Wiring Tools 20
Wiring Safety 22
25

WIRE, CABLE & CONDUIT 25

Wire & Cable 26
NM Cable 34
Conduit 42

55 85
BOXES & PANELS 49
Electrical Boxes 50
Installing Boxes 56
Electrical Panels 64

SWITCHES 73 101
Wall Switches 74
Types of Wall Switches 76
Specialty Switches 84
Testing Switches 88

RECEPTACLES 93
Types of Receptacles 94
Receptacle Wiring 100
GFCI Receptacles 104
Testing Receptacles 108
 104 113

PRELIMINARY WORK 111

Planning Your Project 112
Highlights of the National Electrical Code 118
136
Room by Room Wiring 134

CIRCUIT MAPS 149

Common Household Circuits 150

COMMON WIRING PROJECTS 167

2-WIRE CABLE 150 171
GFCI & AFCI Breakers 168
Surge-Protective Devices 172
Service Panels 174
Grounding & Bonding a Wiring System 182
Subpanels 188
120/240-Volt Dryer Receptacles 192 200
120/240-Volt Range Receptacles 193
Dryer and Range Cords 194
Adding an Outdoor Receptacle 198
Ceilings Lights 202
Recessed Ceiling Lights 206
Track Lights 210 218

Undercabinet Lights 214

Vanity Lights 218
Low-Voltage Cable Lights 220
Hardwired Smoke & CO Alarms 224
Landscape Lights 226
241
Doorbells 230
Wireless Switches 234
Baseboard Heaters 238
Wall Heaters 242
Underfloor Radiant Heat Systems 244
Ceiling Fans 250 244
Remote-Control Ceiling Fan Retrofit 254
Bathroom Exhaust Fans 258
Range Hoods 262
Backup Power Supply 266
Installing a Transfer Switch 272
Outbuildings 278 262
Motion-Sensing Floodlights 286

REPAIR PROJECTS 291

Repairing Light Fixtures 292
Repairing Chandeliers 296
Repairing Ceiling Fans 298 266 289

Repairing Fluorescent Lights 302

Replacing Plugs & Cords 308
Replacing a Lamp Socket 312

COMMON WIRING PROBLEMS & SOLUTIONS 315

291
Service Panels & Grounding 316
Cables & Wires 319
Boxes 323
Cords 326
Receptacles & Switches 328
Light Fixtures 331

Conversions 332
Resources 333
Index 333
Introduction
T his newly updated, 8th edition of BLACK+DECKER The Complete Photo Guide to
Wiring is a comprehensive, user-friendly guide to home wiring projects big and small.
It teaches you everything you need to know to safely complete the most common electrical
upgrades, from installing a new smart switch to roughing in cables and boxes to wiring a
room addition. You do not need to be an expert to tackle these kinds of projects, but you do
need to have the right knowledge. This book is updated to the 2020 edition of the National
Electrical Code (NEC), the primary industry reference behind local code requirements.
When you obtain a permit for your project (this is typically required for anything beyond
simple swap-outs, like replacing an old switch or fixture), your work will be examined by an
inspector to ensure it satisfies the local electrical code. Consult the local code authority for
all details pertaining to your project. Local codes always supersede national codes.

Here are a few of the key updates in the 2020 NEC Emergency Disconnect
that are likely to affect home wiring projects: Outdoor emergency disconnects are required
for home services in new construction, homes
GFCI Receptacles undergoing renovation, and all service replacements.
Ground-fault circuit-interrupter (GFCI) protection is An exterior disconnect is an important safety feature
required for all 125-volt through 250-volt receptacles that allows emergency crews to shut off the power
in select areas. Previous versions of the NEC safely before entering the home. Disconnects
required GFCI protection only for 125-volt, 15- and can include main circuit breakers within outdoor-
20-ampere receptacles. With the 2020 change, GFCI accessible service panels, or they may be disconnect
protection is required for 240-volt dryer receptacles switches in their own outdoor enclosures (typically
as well as 240-volt range receptacles in kitchens (if installed near the utility meter). Disconnects must
the range receptacle is within 6 feet of a sink). be clearly labeled with wording that is specific to the
disconnect type.
Surge Protection
Surge protection is required for new and
replacement service equipment (such as a home’s
main service panel or breaker box). Approved surge-
protective devices (SPD) are designed to protect
the entire household system from electrical surges.
Surge protection is intended to minimize damage
to electronics, motors, and other devices and
equipment that are sensitive to electrical surges.

INTRODUCTION 7
Working Safely
with Wiring

T he only way you can possibly manage home

wiring projects safely is to understand how
electricity works and how it is delivered from the
street to the outlets in your home. The most essential
quality to appreciate about electricity is that the
typical amount that flows through the wires in your
home can be fatal if you contact it directly. Sources
estimate that there are about 45,000 electrical fires
each year causing 440 deaths, 1,250 injuries, and
1.3 billion dollars in property damage. Home wiring
can be a very satisfying task for do‑it‑yourselfers,
but if you don’t know what you’re doing or are in any
way uncomfortable with the idea of working around
electricity, do not attempt it. This chapter explains
the fundamental principles behind the electrical
circuits that run through our homes. It also includes
some basic tips for working safely with wiring, and it
introduces you to the essential tools you’ll need for
the job. The beginner should consider it mandatory
reading. Even if you have a good grasp of electrical
principles, take some time to review the material. A
refresher course is always useful.

In this chapter:
• How Electricity Works
• Glossary of Electrical Terms
• Understanding Electrical Circuits
• Grounding & Polarization
• Home Wiring Tools
• Wiring Safety

WORKING SAFELY WITH WIRING 9

 Faucet

Water flows
under pressure

How Electricity Works

Water supply pipe

A household electrical system can be compared

with a home’s plumbing system. Electrical
current flows in wires in much the same way that
Drain pipe
water flows inside pipes. Both electricity and water
enter the home, are distributed throughout the house,
do their “work,” and exit.
In plumbing, water first flows through the pressurized
water supply system. In electricity, current first flows
along hot wires. Current flowing along hot wires also is
pressurized. Electrical pressure is called voltage. Water returns
Large supply pipes can carry a greater volume of under no pressure
water than small pipes. Likewise, large electrical wires
carry more current than small wires. This electrical Water and electricity both flow. The main difference is that
current‑carrying capacity of wires is called ampacity. you can see water (and touching water isn’t likely to kill you).
Water is made available for use through the faucets, Like electricity, water enters a fixture under high pressure and
exits under no pressure.
spigots, and showerheads in a home. Electricity is made
available through receptacles, switches, and fixtures.
Water finally leaves the home through a drain when everything is functioning as intended. Do not
system, which is not pressurized. Similarly, electrical assume, however, that the neutral is at zero volts.
current flows back through neutral wires. The current Several defects can put voltage on the neutral, so treat
in neutral wires is not pressurized and is at zero volts, the neutral as a hot wire until demonstrated otherwise.

White (neutral) wire Current returns under no pressure

Switch

Light fixture

Current flows under pressure

Black (hot) wire

10 THE COMPLETE GUIDE TO WIRING

The Delivery System
Electricity that enters the home is produced by large from the two 120‑volt wires may be combined
power plants. Power plants are located in all parts of at the service panel to supply electricity to large
the country and generate electricity with generators 240‑volt appliances such as clothes dryers or electric
that are turned by water, wind, or steam. From these water heaters.
plants electricity enters large “step‑up” transformers Incoming electricity passes through a meter that
that increase voltage to half a million volts or more. measures electricity consumption. Electricity then
Electricity flows at these high voltages and enters the service panel, where it is distributed to
travels through high‑voltage transmission wires to circuits that run throughout the house. The service
communities that can be hundreds of miles from the panel also contains circuit breakers or fuses that shut
power plants. “Step‑down” transformers located at off power to the individual circuits in the event of
substations then reduce the voltage for distribution a short circuit or an overload. Certain high‑current
along street wires. On utility power poles, smaller appliances, such as microwave ovens, are usually
transformers further reduce the voltage to ordinary plugged into their own individual circuits to
120‑volt electricity for household use. prevent overloads.
Wires carrying electricity to a house either run Voltage ratings determined by power companies
underground or are strung overhead and attached and manufacturers have changed over the years.
to a piece of conduit called a service mast. Most These changes do not affect the performance of
homes built after 1950 have three wires running to new devices connected to older wiring. For making
the service head: two power wires, each carrying electrical calculations, use a rating of 120 volts or
120 volts, and a grounded neutral wire. Electricity 240 volts for your circuits.

Power plants supply electricity to Substations are located near the Electrical transformers reduce the
thousands of homes and businesses. communities they serve. A typical high-voltage electricity that flows
Step-up transformers increase the substation takes electricity from through wires along neighborhood
voltage produced at the plant. high-voltage transmission wires streets. A utility pole transformer—or
and reduces it for distribution ground transformer—reduces voltage
along street wires. from 10,000 volts to the normal
120-volt electricity used in households.

WORKING SAFELY WITH WIRING 11

 Parts of the Electrical System

Current flows to
the home from the
utility service

The service mast (metal conduit) and the weatherhead create The meter measures the amount of electricity consumed. It is
the entry point for electricity into your home. The mast is usually attached to the side of the house and connects to the
supplied with three wires, two of which (the insulated wires) service mast. The electric meter belongs to your local power
each carry 120 volts and originate at the nearest transformer. utility company. If you suspect the meter is not functioning
In some areas, electricity enters from below ground as a properly, contact the power company.
lateral instead of the overhead drop shown above.

Surges in current flow to grounding rod Current flows back to neutral at service mast

A grounding wire connects the electrical system to the earth Light fixtures attach directly to a household electrical system.
through a metal grounding rod driven next to the house or They are usually controlled with wall switches.
through another type of grounding electrode.

12 THE COMPLETE GUIDE TO WIRING

The main service panel, or “breaker box,” distributes power to Electrical boxes enclose wire connections. According to the
individual circuits. A circuit breaker protects each circuit from National Electrical Code, all wire splices and connections
short circuits and overloads. Circuit breakers also are used to must be contained entirely in a covered plastic or metal
shut off power to individual circuits while repairs are made. electrical box. This box must be accessible for inspection and
Older homes may have fuses instead of circuit breakers. for service.

Switches control electricity passing through hot circuit wires. Receptacles, sometimes called outlets, provide plug-in access
Switches can be wired to control light fixtures, ceiling fans, to electricity. A 120-volt, 15-amp or 20-amp receptacle with
appliances, and receptacles. a grounding hole is the most typical receptacle in wiring
systems installed after 1965. Most receptacles have two
plug-in locations and are called duplex receptacles.

WORKING SAFELY WITH WIRING 13

 GLOSSARY OF ELECTRICAL TERMS
Ampere (or amp): Refers to the rate at which electrical Neutral wire: A wire that returns current at zero voltage to
current flows to a light, tool, or appliance. the source of electrical power. Usually covered with white or
light gray insulation. Also called the grounded wire.
Armored cable: An assembly of insulated wires enclosed in
a flexible, interlocked metallic armor. Abbreviated “AC.” Nonmetallic sheathed cable: NM cable consists of two or
more insulated conductors and, in most cases, a bare
Box: A device used to contain wiring connections. ground wire housed in a durable PVC casing.
Cable: Two or more wires that are grouped together and Outlet: A place where electricity is taken for use. A
protected by a covering or sheath. receptacle is a common type of outlet. A box for a ceiling
Circuit: A continuous loop of electrical current flowing fan is another type of outlet.
along wires. Overload: A demand for more current than the circuit wires
Circuit breaker: A safety device that interrupts an electrical or electrical device was designed to carry. This should
cause a circuit breaker to trip or a fuse to blow.
circuit in the event of an overload or short circuit.
Pigtail: A short wire used to connect two or more wires to a
Conductor: Any material that allows electrical current
single screw terminal.
to flow through it. Copper wire is an especially
good conductor. Polarized receptacle: A receptacle designed to keep hot
current flowing along black or red wires and neutral current
Conduit: A metal or plastic pipe used to protect wires.
flowing along white or gray wires.
Continuity: An uninterrupted electrical pathway through a
Power: The work performed by electricity for a period of
circuit or electrical fixture.
time. Use of power makes heat, motion, or light.
Current: The flow of electricity along a conductor. Receptacle: A device that provides plug-in access
Duplex receptacle: A receptacle that provides connections to electricity.
for two plugs. Romex: A brand name of plastic-sheathed electrical cable
Flexible metal conduit (FMC): Hollow, coiled steel or that is commonly used for indoor wiring. Commonly known
aluminum tubing that may be filled with wires (similar to as nonmetallic, or NM, cable.
armored cable, but AC is prewired). Screw terminal: A place where a wire connects to a
Fuse: A safety device, usually found in older homes, receptacle, switch, or fixture.
that interrupts electrical circuits during an overload or Service panel: A metal box usually near the site where
short circuit. electricity enters the house. In the service panel, electrical
current is split into individual circuits. In residences the service
Greenfield: A brand name for an early type of flexible metal
panel has a circuit breaker or a fuse to protect each circuit.
conduit. The current term is flexible metal conduit. Note:
flexible metal conduit is different from armored cable. Short circuit: An accidental and improper contact between
two current-carrying wires or between a current-carrying
Grounded wire: See neutral wire.
wire and a grounding conductor.
Grounding wire: A wire used in an electrical circuit to conduct
Switch: A device that controls electricity passing through
current to the service panel in the event of a ground fault. hot circuit wires. Used to turn lights and appliances on
The grounding wire often is a bare copper wire or a green and off.
insulated wire.
UL: Formerly known as Underwriters Laboratories, this
Hot wire: Any wire that carries voltage. In an electrical organization tests electrical devices and manufactured
circuit, the hot wire usually is covered with black or products for safety.
red insulation.
Voltage (or volts): A measurement of electricity in terms
Insulator: Any material, such as plastic or rubber, that of pressure.
resists the flow of electrical current. Insulating materials
Wattage (or watts): A measurement of electrical power in
protect wires and cables.
terms of total work performed. Watts can be calculated by
Junction box: See box. multiplying the voltage times the amperage.
Meter: A device used to measure the amount of electrical Wire connector: A device used to connect two or more
power being used. wires together. Also called a wire nut.

14 THE COMPLETE GUIDE TO WIRING

 Weatherhead prevents moisture from entering the house

Service mast creates an anchor point for service wires

Service wires supply electricity to the house from the utility company’s power lines

Chandelier

Switch loop

Wall switch
Separate 120-volt circuit for microwave oven

Receptacles GFCI receptacles

Separate 240-volt
circuit for water heater

Electric meter measures the

amount of electricity consumed
and displays the measurement
inside a glass dome Service panel distributes
electrical power into circuits

Separate 120/240-volt
circuit for clothes dryer
Grounding wire to
metal grounding rod

Grounding rod must be at least

8 feet long and is driven into
the ground outside the house Bonding wire to
metal water pipe

Jumper wire is used to bypass

the water meter and ensures an
uninterrupted bonding pathway

WORKING SAFELY WITH WIRING 15

 ANATOMY OF
A CIRCUIT
Understanding
Electrical Circuits Service panel

Service hot wires

A n electrical circuit is a continuous loop.

Household circuits carry electricity from the
main service panel, throughout the house, and
Service neutral wire
Main circuit breaker

back to the main service panel. Several switches,

receptacles, light fixtures, or appliances may be
connected to a single circuit.
Current enters a circuit loop on hot wires and
returns along neutral wires. These wires are color
coded for easy identification. Hot wires are black
or red, and neutral wires are white or light gray. For
safety, all modern circuits include a bare copper
or green insulated grounding wire. The grounding
wire conducts current in the event of a ground
fault (see page 168) and helps reduce the chance of
severe electrical shock. The service panel also has a
bonding wire connected to a metal water pipe and
a grounding wire connected to a metal grounding Branch circuit breaker
rod, buried underground, or to another type of
grounding electrode.
If a circuit carries too much current, it can
overload. A fuse or a circuit breaker protects each
circuit in case of overloads.
Current returns to the service panel along a
neutral circuit wire. Current then leaves the house
on a large neutral service wire that returns it to the
utility transformer.

16 THE COMPLETE GUIDE TO WIRING

 Light switch Light switch

Service panel
Common Common
terminal terminal

hot wires

rcuit breaker

Circuit wires

White neutral wire

Grounding wire

Hot wire
Light fixture

circuit breaker

Grounding screw Grounding screw

Grounding wire

Receptacle
Receptacle

WORKING SAFELY WITH WIRING 17

 Grounding & Polarization

E lectricity always seeks to return to its source

and complete a continuous circuit. Contrary
to popular belief, electricity will take all available
water and gas pipes are the most common examples.
A metal water and gas pipe could become energized
by coming in contact with a damaged electrical wire.
return paths to its source, not just the path of lowest Metal gas pipe could become energized by a ground
resistance. In a household wiring system, this return fault in a gas appliance such as a furnace.
path is provided by white neutral wires that return Bonding is a very important safety system. A
current to the main service panel. From the service person could receive a fatal shock if he or she touches
panel, current returns along the uninsulated neutral energized metal that is improperly bonded, because
service wire to a power pole transformer. that person becomes electricity’s return path to
You will see the terms grounding and bonding used its source. Bonding is also a fire safety system that
in this and other books about electricity. These terms reduces the chance of electrical fires.
are often misunderstood. You should understand the Grounding connects the home’s electrical system
difference to safely work on electrical circuits. to the earth. Grounding’s primary purpose is to help
Bonding connects the noncurrent-carrying metal stabilize voltage fluctuations caused by lightning and
parts of the electrical system, such as metal boxes and other problems in the electrical grid. Grounding also
metal conduit, in a continuous low-resistance path provides a secondary return path for electricity in
back to the main service panel. If this metal becomes case there is a problem in the normal return path.
energized (a ground fault), current travels on the Grounding is accomplished by connecting a wire
bonded metal and quickly increases to an amount between the main service panel and a grounding
that trips the circuit breaker or blows the fuse. The electrode. The most common grounding electrode is
dead circuit alerts people to a problem. a buried copper-coated steel rod. Other grounding
Other metal that could become energized also electrodes include reinforcing steel in the footing,
must be bonded to the home’s electrical system. Metal called a ufer ground.

Current
Service panel Black hot wire returns to
Grounding wire
transformer
White
neutral
wire

Grounding
screw

Grounding wire

Loose hot wire

Grounding wire to Grounding wire to
grounding rods
grounding rods
8 ft. Small amount 8 ft.
6 ft. minimum trickles to rods 6 ft. minimum

18 THE COMPLETE GUIDE TO WIRING

 Grounding of the home electrical system is however, that deterioration of this older cable may
accomplished by connecting the household electrical decrease its effectiveness as a bonding conductor.
system to the metal water service pipe, if any, between Modern cable includes a green insulated or bare
your house and the street and to another grounding copper wire that serves as the bonding path. This
electrode such as metal grounding electrodes that are bonding wire is connected to all three‑slot receptacles
buried in the earth. and metal boxes to provide a continuous pathway for
After 1920 most American homes included any ground‑fault current. By plugging a three‑prong
receptacles that accepted polarized plugs. The plug into a grounded three‑slot receptacle, people are
two‑slot polarized plug and receptacle was designed protected from ground faults that occur in appliances,
to keep hot current flowing along black or red tools, or other electric devices.
wires and neutral current flowing along white or Use a receptacle adapter to plug three‑prong
gray wires. plugs into two‑slot receptacles, but use it only if the
The metal jacket around armored cable and receptacle connects to a grounding wire or grounded
flexible metal conduit, widely installed in homes electrical box. Adapters have short grounding wires or
during the 1940s, provided a bonding path. When wire loops that attach to the receptacle’s coverplate
connected to metal junction boxes, it provided mounting screw. The mounting screw connects the
a metal pathway back to the service panel. Note, adapter to the grounded metal electrical box.

Modern NM (nonmetallic) cable, Armored cable has a flexible metal jacket Polarized receptacles have a long slot
found in most wiring systems installed and contains hot and neutral wires. and a short slot. Used with a polarized
after about 1965, contains a bare It may contain a grounding wire or it plug, the polarized receptacle keeps
copper wire that provides bonding for may use the metal jacket to provide the electrical current directed for safety.
receptacle and switch boxes. grounding path. Flexible metal conduit
(not shown) is sold empty.

Tamper‑resistent three‑slot receptacles A receptacle adapter allows three-prong Double‑insulated tools have
are required by code for new plugs to be inserted into two-slot nonconductive plastic bodies to
homes and when replacing existing receptacles. The adapter should be prevent shocks caused by ground
receptacles. They are usually used only with receptacles mounted in a faults. Because of these features,
connected to a standard two-wire cable bonded metal box, and the grounding loop double-insulated tools can be used
with ground. or wire of the adapter must be attached to safely with ungrounded receptacles.
the coverplate mounting screw.

WORKING SAFELY WITH WIRING 19

 Home Wiring Tools

T o complete the wiring projects shown in this book,

you need a few specialty electrical tools as well
as a collection of basic hand tools. As with any tool
The materials used for electrical wiring have
changed dramatically in the last 20 years, making
it much easier for homeowners to do their own
purchase, invest in quality products when you buy tools electrical work. The following pages show how
for electrical work. Keep your tools clean, and sharpen to work with the following components for
or replace any cutting tools that have dull edges. your projects.
A F
C

D
B

K J I H G

Hand tools you’ll need for home wiring projects include a stud finder/laser level (A) for locating framing members and aligning
electrical boxes; tape measure (B); a cable ripper (C) for scoring NM sheathing; standard (D) and Phillips (E) screwdrivers; a
utility knife (F); side cutters (G) for cutting wires; channel-type pliers (H) for general gripping and crimping; linesman pliers (I)
that combine side cutter and gripping jaws; needlenose pliers (J); wire strippers (K) for removing insulation from conductors.

20 THE COMPLETE GUIDE TO WIRING

Use a tool belt to keep frequently used tools within easy A fish tape is useful for installing cables in finished wall
reach. Electrical tapes in a variety of colors are used for cavities and for pulling wires through conduit. Lubrication
marking wires and for attaching cables to a fish tape. products reduce friction and make it easier to pull cables
and wires.

Diagnostic tools for home wiring use include a noncontact voltage tester (A) to safely check wires for current and confirm that
circuits are dead; a plug-in tester (B) to check receptacles for correct polarity, grounding, and circuit protection; a multimeter
(C) to measure AC/DC voltage, AC/DC current, resistance, capacitance, frequency, and duty cycle (model shown is an auto-
ranging digital multimeter with clamp-on jaws that measure through sheathing and wire insulation).

WORKING SAFELY WITH WIRING 21

 Wiring Safety

S afety should be the primary concern of

anyone working with electricity. Although
most household electrical repairs are simple and
make sure the power is off by testing for power with a
voltage tester.

straightforward, always use caution and good TIP: Test a live circuit with the voltage tester to
judgment when working with electrical wiring or verify that it is working before you rely on it.
devices. Common sense can prevent accidents. Restore power only when the repair or
The basic rule of electrical safety is always turn off replacement project is complete.
power to the area or device you are working on. At the Follow the safety tips shown on these pages. Never
main service panel or at the subpanel (as applicable), attempt an electrical project beyond your skill or
shut off the circuit breaker or remove the fuse that confidence level.
controls the circuit you are servicing. Then check to

Shut power OFF at the main service panel or subpanel where Create a circuit index and affix it to the inside of the door to
the circuit originates before beginning any work. your main service panel. Update it as needed.

Confirm power is OFF

by testing at the outlet,
switch, or fixture with a
voltage tester.

Use only UL‑approved electrical parts or devices. These devices

have been tested for safety by Underwriters Laboratories.

22 THE COMPLETE GUIDE TO WIRING

Wear rubber‑soled shoes while working on electrical projects. Use fiberglass or wood ladders when making routine
On damp floors, stand on a rubber mat or dry wooden boards. household repairs near the service mast.

Extension cords are for temporary use only. Cords must be Breakers and fuses must be compatible with the panel
rated for the intended usage. manufacturer and match the circuit capacity.

Never alter the prongs of a plug to fit a receptacle. If possible, Do not penetrate walls or ceilings without first shutting off
install a new grounded receptacle. electrical power to the circuits that may be hidden.

WORKING SAFELY WITH WIRING 23

Wire, Cable
& Conduit

W ire, cable, and conduit comprise the electrical

infrastructure in your home. Selecting the
appropriate size and type and handling it correctly
is absolutely necessary to a successful wiring project
that will pass inspection.
Copper or aluminum wires are the primary
conductors of electricity in any home. The electricity
itself travels on the outer surfaces of the wire, so
insulation is added to the wires to protect against
shock and fires. The insulated wires are frequently
grouped together and enclosed in sheathing
according to gauge and function. Multiple wires
enclosed in sheathing form a cable. In some cases,
the wires are enclosed in metal or plastic tubes
known as conduit. Conduits and tubing (also known
as raceways) are used primarily in situations where
the cables or wires are exposed, such as in open
garage walls.
This chapter introduces some of the many
varieties of wire, cable, and conduit used in home
construction and explains which types to use where.
It also will demonstrate the essential skills used to run
new cable, install conduit, strip sheathing, make wire
connections, and more.

In this chapter:
• Wire & Cable
• NM Cable
• Conduit

WIRE, CABLE & CONDUIT 25

 wire, which does not need insulation. The insulation
is color coded (see chart, below left) to identify the
wire as a hot wire, a neutral wire, or a grounding wire.
New cable sheathing is also color coded to indicate
the size of the wires inside. White means #14 wire,
yellow means #12 wire, and orange means #10 wire.
In most wiring systems installed after 1965, the
Wire & Cable wires and cables are insulated with PVC. This type of
insulation is very durable and can last as long as the
house itself.

W ires (known as conductors) are made of copper

or aluminum in most houses. Copper is a better
conductor of electricity and is used in most houses.
Before about 1965, wires and cables were insulated
with rubber or cloth. Rubber and cloth insulation
has a life expectancy of about 25 to 30 years. Old
Copper-coated aluminum wires may be found in a insulation that is cracked or damaged can be reinforced
few houses built in the early 1970s, but this wire is temporarily by wrapping the wire with plastic electrical
uncommon. “Tin”-coated copper wires may be found tape. However, old wiring with cracked or damaged
in houses built in the 1940s and 1950s. insulation should be inspected by a qualified electrician
A group of two or more wires enclosed in a metal, to make sure it is safe.
rubber, cloth, or plastic sheathing is called a cable Wires must be large enough for the amperage
(see photo, opposite page). The sheathing protects rating of the circuit (see chart, below right). A wire
the wires from damage and protects people from that is too small can become dangerously hot. Wire
electrical shock. Conduit also protects wires, but it is sizes are categorized according to the American Wire
not considered a cable. Gauge (AWG) system. To check the size of a wire, use
Individual wires are covered with rubber or plastic the wire stripper openings of a combination tool (see
insulation. An exception is a bare copper grounding page 30) as a guide.

WIRE COLOR CHART WIRE SIZE CHART

WIRE COLOR FUNCTION WIRE GAUGE WIRE CAPACITY & USE

White or gray Neutral wire carrying current #6 55 amps, 240 volts; central air
at zero voltage conditioner, electric furnace

#8 40 amps, 240 volts; electric range,

Black Hot wire carrying current at central air conditioner
full voltage
#10 30 amps, 240 volts; window air
Red Hot wire carrying current at conditioner, clothes dryer
full voltage
#12 20 amps, 120 volts; light fixtures,
receptacles, microwave oven
White, Hot wire carrying current at
black markings full voltage #14 15 amps, 120 volts; light
fixtures, receptacles
Green Serves as a
bonding pathway #16 Light‑duty
extension cords

Bare copper Serves as a #18 Thermostats, doorbells,

bonding pathway to 22 security systems

Individual wires are color-coded to identify their function. In Wire sizes (shown actual size) are categorized by the American
some circuit installations, the white wire serves as a hot wire Wire Gauge system. The larger the wire size, the smaller the
that carries voltage. If so, this white wire may be labeled with AWG number. The ampacities in this table are for copper wires
black tape or paint to identify it as a hot wire. in NM cable. The ampacity for the same wire in conduit is
usually more. The ampacity for aluminum wire is less.

26 THE COMPLETE GUIDE TO WIRING

 Knob and tube wiring, so called because of the shape
of its porcelain insulating brackets, was common
before 1940. Wires are covered with a layer of
rubberized cloth, but have no additional protection.

Armored cable (AC) has been around since the 1920s. Early versions
had no grounding function, but existed solely to protect the wires that
were threaded into it. Later armored cable products either had ground
wire twisted in with the flexible metal cover or relied on the metal cover
itself for connecting to ground.

Metal conduit has been used for over 100 years to protect wires from
damage. Metal conduit may be used as the equipment grounding conductor
if the electrical continuity is maintained. Modern conduit and tubing (a
thinner material) is made from metal and plastic.

NM (nonmetallic) cable was developed around 1930. The first version had
fabric sheathing that degrades over time and had no ground wire.

Modern versions of NM cable with a hard

PVC jacket, or sheathing, came onto the
market in the 1960s.

UF (underground feeder) cable

has wires embedded in a
solid‑core plastic vinyl sheathing
and includes a bare copper
grounding wire. It is designed for
installations in damp conditions,
such as buried circuits.

WIRE, CABLE & CONDUIT 27

 Coaxial cable is used to connect cable television and data
jacks. It is available in lengths up to 25 ft. with preattached
F‑connectors (A). Or you can buy bulk cable (B) in any length.

A
NM (nonmetallic) sheathed cable should be used
for most indoor wiring projects in dry locations. NM
cable is available in a wide range of wire sizes and in
either “2‑wire with ground” or “3‑wire with ground”
types. NM cable is sold in rolls that contain from 25 B
to 250 ft. of cable. THHN/THWN wire can be used in all conduit
applications. Each wire, purchased individually, is
covered with a color‑coded thermoplastic insulating
jacket. Make sure the wire you buy has the THHN/
THWN rating. Other wire types are less resistant to
heat and moisture than THHN/THWN wire.

Service entrance cable (SE) is used between

the electric utility’s service wires and the home’s main
electrical panel. It can also be used for kitchen ranges and
other 50‑amp or 60‑amp appliances that require 8‑gauge
or larger wire. It is similar to NM cable, but each individual Cat 5 (Category 5) cable is used mostly for information and data
conducting wire is made from stranded copper or aluminum networks. The cable contains four pairs of twisted copper wire
wires. SE cable is available in both 2‑wire and 3‑wire types. with color‑coded insulation. Category 6 and Category 7 are
also available and allow faster data transmission.

Telephone cable is used to connect telephone outlets.

UF (Underground Feeder) cable is used for wiring in Your phone company may recommend four‑wire cable
damp locations, such as in an outdoor circuit, and for (shown below) or eight‑wire cable, sometimes called
buried installations. It has a white or gray solid‑core four‑pair. Eight‑wire cable has extra wires that are left
vinyl sheathing that protects the wires inside. It also unattached. These extra wires allow for future expansion
can be used indoors wherever NM cable is allowed. of the system.

NM Sheathing Colors
The PVC sheathing for NM cable is coded by color so
wiring inspectors can tell what the capacity of the cable is
at a glance.

• Black = 6 or 8 AWG conductors

• Orange = 10 AWG conductors

• Yellow = 12 AWG conductors

• White = 14 AWG conductors

• Gray = UF cable (see photo above)

28 THE COMPLETE GUIDE TO WIRING

Reading NM Reading Unsheathed,
(Nonmetallic) Cable Individual Wire
Maximum voltage rating
(600 volts)
Wire material
Number of Cable type
(nonmetallic) Paper
insulated wires

Maximum voltage rating

Wire gauge Wire gauge Corrosion resistance code
(600 volts)

NM cable is labeled with the number of insulated wires Unsheathed, individual wires are used for conduit and
it contains. The bare grounding wire is not counted. For raceway installations. Wire insulation is coded with letters to
example, a cable marked 14/2 G (or 14/2 WITH GROUND) indicate resistance to moisture, heat, and gas or oil. Code
contains two insulated 14-gauge wires, plus a bare copper requires certain letter combinations for certain applications.
grounding wire. Cable marked 14/3 WITH GROUND has T indicates thermoplastic insulation. H stands for heat
three 14-gauge wires plus a grounding wire. NM cable also resistance, and two Hs indicate high resistance (up to 194°F).
is stamped with a maximum voltage rating, as determined by W denotes wire suitable for wet locations. Wire coded with an
Underwriters Laboratories (UL). N is impervious to damage from oil or gas.

Minimum: two 14‑gauge wires Minimum: two Minimum: two

16‑gauge wires 18‑gauge wires
Maximum: four 12‑gauge Maximum: four Maximum: two
(or three 10‑gauge) wires 14‑gauge wires 14‑gauge wires

Use wire connectors (nuts) rated for the wires you are connecting. Wire connectors are color-coded by size, but the coding
scheme varies according to manufacturer. The wire connectors shown above come from one major manufacturer. To ensure
safe connections, each connector is rated for both minimum and maximum wire capacity. These connectors can be used to
connect both conducting wires and grounding wires. Green wire connectors are used only for grounding wires.

TIPS FOR WORKING WITH WIRE

WIRE GAUGE AMPACITY MAXIMUM WATTAGE LOAD Wire ampacity is a measurement of
how much current a wire can carry
14‑gauge 15 amps 1,440 watts (120 volts) safely. Ampacity varies by the size
of the wires. When installing a new
12‑gauge 20 amps 1,920 watts (120 volts) circuit, choose wire with an ampacity
3,840 watts (240 volts) rating matching the circuit size. For
dedicated appliance circuits, check
10‑gauge 30 amps 2,880 watts (120 volts) the wattage rating of the appliance
5,760 watts (240 volts) and make sure it does not exceed
the maximum wattage load of the
circuit. The ampacities in this table
8‑gauge 40 amps 7,680 watts (240 volts)
are for copper wires in NM cable. The
ampacity for the same wire in conduit
6‑gauge 55 amps 10,560 watts (240 volts) is usually more. The ampacity for
aluminum wire is less.

WIRE, CABLE & CONDUIT 29

 How to Strip NM Sheathing & Insulation

1 2 3
Cutting
point

Measure and mark the cable 8" to 10" Grip the cable tightly with one hand, Peel back the plastic sheathing
from the end. Slide the cable ripper and pull the cable ripper toward the and the paper wrapping from the
onto the cable, and squeeze tool firmly end of the cable to cut open the individual wires.
to force the cutting point through the plastic sheathing.
plastic sheathing.

4 5 6

Cutting
jaws Wire
stripper
openings

Cut away the excess plastic sheathing Cut individual wires as needed using the Strip insulation for each wire using the
and paper wrapping using the cutting cutting jaws of the combination tool. stripper openings. Choose the opening
jaws of a combination tool. Leave a minimum of 3" of wire running that matches the gauge of the wire,
past the edge of the box. and take care not to nick or scratch the
ends of the wires.

30 THE COMPLETE GUIDE TO WIRING

 How to Connect Wires to Screw Terminals

1 2 3

Strip about 3⁄4" of insulation from each Form a C-shaped loop in the end of each Hook each wire around the screw
wire using a combination tool. Choose wire using a needlenose pliers or the terminal so it forms a clockwise loop.
the stripper opening that matches the hole of the correct gauge in a pair of Tighten the screw firmly. Insulation
gauge of the wire, and then clamp wire strippers. The wire should have no should just touch head of screw. Never
the wire in the tool. Pull the wire firmly scratches or nicks. place the ends of two wires under a
to remove plastic insulation. single screw terminal. Instead use a
pigtail wire (see page 33).

CABLE STAPLES PUSH-IN CONNECTORS

A
B
C
D
E

Use plastic cable staples to fasten cables. Choose Push-in connectors are a relatively new product for
staples sized to match the cables. Stack-It® staples (A) joining wires. Instead of twisting the bare wire ends
hold up to four 2-wire cables; ¾" staples (B) for 12/2, together, you strip off about ¾" of insulation and insert
12/3, and all 10-gauge cables; ½" staples (C) for 14/2, each into a hole in the connector. The connectors come
14/3, or 12/2 cables; coaxial staples (D) for anchoring with two to six holes sized for various gauge wires.
television and data cables; bell wire staples (E) for These connectors are perfect for inexperienced DIYers,
attaching telephone cables. because they do not pull apart like a sloppy twisted
connection can.

WIRE, CABLE & CONDUIT 31

 How to Join Wires with a Wire Connector

1 2

Ensure power is off and test for power. Grasp the wires to be Twist a wire connector over the ends of the wires. Make
joined in the jaws of a pair of linesman’s pliers. The ends of sure the connector is the right size (see page 29).
the wires should be flush and they should be parallel and Hand-twist the connector as far onto the wires as you can.
touching. Rotate the pliers clockwise two or three turns to There should be no bare wire exposed beneath the collar of
twist the wire ends together. the connector.

OPTION: Reinforce the joint by wrapping it with OPTION: Strip ¾" of insulation off the ends of the wires to
electrician’s tape. By code, you cannot bind the wire be joined, and insert each wire into a push-in connector.
joint with tape only, but it can be used as insurance. Few Gently tug on each wire to make sure it is secure.
professional electricians use tape for purposes other than
tagging wires for identification.

32 THE COMPLETE GUIDE TO WIRING

 How to Pigtail Wires

1 2

Cut a 6" length from a piece of insulated wire the same gauge Join one end of the pigtail to the wires that will share the
and color as the wires it will be joining. Strip ¾" of insulation connection using a wire nut.
from each end of the insulated wire.

NOTE: Pigtailing is done mainly to avoid connecting multiple

wires to one terminal, which is a code violation.
3

ALTERNATIVE: If you are pigtailing to a grounding screw

or grounding clip in a metal box, you may find it easier to
attach one end of the wire to the grounding screw before Connect the pigtail to the appropriate terminal on the
you attach the other end to the other wires. receptacle or switch. Fold the wires neatly and press the
fitting into the box.

WIRE, CABLE & CONDUIT 33

 NM Cable

N on metallic (NM) cable is used for most indoor

wiring projects except those requiring conduit
and those in damp areas such as against concrete or
masonry walls with dirt on the other side. Cut and install
the cable after all electrical boxes have been mounted.
Refer to your wiring plan to make sure each length of
cable is correct for the circuit size and configuration.
Cable runs are difficult to measure exactly, so leave
plenty of extra cable when cutting each length. Cable
splices inside walls are not allowed by code. When
inserting cables into a circuit breaker panel, make
sure the power is shut off.
After all cables are installed and all the ground
wires spliced, call your electrical inspector to arrange Pulling cables through studs is easier
for the rough-in inspection. Do not install wallboard if you drill smooth, straight holes
at the same height. Prevent kinks
or attach light fixtures and other devices until
by straightening the cable before
this inspection is done. Check with your building pulling it through the studs. Use
inspector before using NM cable. Some areas, such plastic grommets to protect cables
as the Chicago area, do not allow NM cable. on steel studs (inset).

This framing member chart shows the

FRAMING MEMBER MAXIMUM HOLE SIZE MAXIMUM NOTCH SIZE maximum sizes for holes and notches
2 × 4 loadbearing stud 17⁄16" diameter ⁄8" deep
7 that can be cut into studs and joists
when running cables. When boring
2 × 4 non‑loadbearing stud 2 ⁄8" diameter
1
17⁄16" deep holes, there must be at least 5⁄8" of
2 × 6 loadbearing stud 23⁄16" diameter 13⁄8" deep wood between the edge of a stud and
the hole and at least 2" between the
2 × 6 non‑loadbearing stud 35⁄16" diameter 23⁄16" deep
edge of a joist and the hole. Joists can
2 × 6 joists 1 ⁄16" diameter
13 15
⁄16" deep be notched only in the end third of the
2 × 8 joists 2 ⁄2" diameter
1
1 ⁄4" deep
1 overall span; never in the middle third
of the joist. If 1¼" clearance cannot
2 × 10 joists 3 ⁄16" diameter
1
19⁄16" deep possibly be maintained, you may be
2 × 12 joists 33⁄4" diameter 17⁄8" deep able to satisfy code by installing a metal
nail plate over the point of penetration
in the stud or joist. Different rules apply
to wood I-joists, metal-plate-connected
TOOLS & MATERIALS trusses, engineered beams, and beams
assembled from lumber. In general,
you may not drill and notch trusses
Drill and bits Needlenose pliers Cable staples Wire connectors
and assembled beams. Manufacturers
Tape measure Hammer Masking tape Eye and ear of I-joists and engineered beams have
Cable ripper Fish tape Electrical tape protection limits about the size and location
of holes.
Combination tool NM cable Grounding
Screwdrivers Cable clamps pigtails

34 THE COMPLETE GUIDE TO WIRING

 How to Install NM Cable

1 2

Drill 5⁄8" holes in framing members for the cable runs. This is Where cables will turn corners (step 6, page 36), drill
done easily with a right-angle drill, available at rental centers. intersecting holes in adjoining faces of studs. Measure and
The edge of the hole must be set back at least 1¼" from cut all cables, allowing 2 ft. extra at ends entering the breaker
the front face of the framing member, or the cable must be panel and 1 foot for ends entering the electrical box.
protected with a metal plate (page 116).

Locknut
1
⁄4" minimum

Cable clamp

3 4
Shut off power to the circuit breaker panel. Use a cable ripper Open a knockout in the circuit breaker panel using a hammer
to strip the cable, leaving at least ¼" of sheathing to enter the and screwdriver. Insert a cable clamp into the knockout, and
circuit breaker panel. Clip away the excess sheathing. secure it with a locknut. Insert the cable through the clamp so
that at least ¼" of sheathing extends inside the circuit breaker
panel. Tighten the mounting screws on the clamp so the
cable is gripped securely but not so tightly that the sheathing
is crushed. (continued)

WIRE, CABLE & CONDUIT 35

 5

Cutaway view

12”
12" or less

6
Anchor the cable to the center of a framing member within At corners, form a slight L-shaped bend in the end of the
12" of the circuit breaker panel using a cable staple. Stack-It® cable and insert it into one hole. Retrieve the cable through
staples work well where two or more cables must be anchored the other hole using needlenose pliers (inset).
to the same side of a stud. Run the cable to the first electrical
box. Where the cable runs along the sides of framing members,
anchor it with cable staples no more than 4 ft. 6" apart.

7
1
⁄ 4"

8"

1
⁄ 4"

¼"

Staple the cable to a framing member within 8" from where VARIATION: Different types of boxes have different
the sheathing ends in the box. Hold the cable taut against the clamping devices. Make sure cable sheathing extends
front of the box, and mark a point on the sheathing ¼" past ¼" past the edge of the clamp to ensure that the cable is
the box edge. Remove sheathing from the marked line to the secure and that the wire won’t be damaged by the edges
end using a cable ripper, and clip away excess sheathing with of the clamp. Clamp cable inside all boxes except single
a combination tool. Insert the cable through the knockout in gang (2¼ × 4") boxes.
the box.

36 THE COMPLETE GUIDE TO WIRING

 6"
3"

8 9
As each cable is installed in a box, clip back each wire so that at Strip ¾" of insulation from each circuit wire in the box using a
least 3" of workable wire extends past the front edge of the box. combination tool. Take care not to nick the copper.

10 11
Continue the circuit by running cable between each pair of At metal boxes and recessed fixtures, open knockouts, and
electrical boxes, leaving an extra 1 ft. of cable at each end. attach cables with cable clamps. From inside the fixture,
strip away all but ¼" of sheathing. Clip back wires so there
is 8" of workable length, and then strip ¾" of insulation from
each wire. (continued)

WIRE, CABLE & CONDUIT 37

 Pigtail

12 13
For a surface-mounted fixture such as a baseboard heater or At each recessed fixture and metal electrical box, connect one
fluorescent light fixture, staple the cable to a stud near the end of a grounding pigtail to the box using a grounding clip
fixture location, leaving plenty of excess cable. Mark the floor attached to the frame (shown above) or a green grounding
so the cable will be easy to find after the walls are finished. screw. A grounding pigtail is not needed for plastic boxes.

Clamps

14 15
At each electrical box and recessed Label the cables entering each box to indicate their destinations. In boxes with
fixture, join grounding wires together complex wiring configurations, also tag the individual wires to make final hookups
with a wire connector. If the box has easier. After all cables are installed, your rough-in work is ready to be reviewed by
internal clamps, tighten the clamps over the electrical inspector.
the cables.

38 THE COMPLETE GUIDE TO WIRING

 How to Run NM Cable Inside a Finished Wall

1 2 3 Attic

Soil stack Attic

Top plate

Cutaway
view

Bottom
Walls
plate

Bottom plate
Drill bit
extender

Cutaway
Top plate
view Basement

From the unfinished space below the From the unfinished space above the Extend a fish tape down through the top
finished wall, look for a reference point, finished wall, find the top of the stud plate, twisting the tape until it reaches
such as a soil stack, plumbing pipes, cavity by measuring from the same the bottom of the stud cavity. From the
or electrical cables, that indicates the fixed reference point used in step 1. unfinished space below the wall, use
location of the wall above. Choose Drill a 1" hole down through the top a piece of stiff wire with a hook on one
a location for the new cable that does plate and into the stud cavity using a end to retrieve the fish tape through the
not interfere with existing utilities. Drill a drill bit extender. drilled hole in the bottom plate.
1" hole up into the stud cavity.

4 5 6

Cutaway
view

Trim back 2" of sheathing from the end Bend the wires against the cable, and From above the finished wall, pull
of the NM cable, and then insert the then use electrical tape to bind them steadily on the fish tape to draw the
wires through the loop at the tip of the tightly. Apply cable-pulling lubricant to cable up through the stud cavity. This
fish tape. the taped end of the fish tape. job will be easier if you have a helper
feed the cable from below as you pull.

WIRE, CABLE & CONDUIT 39

 Tips for Running Cable Inside Finished Walls
Second story

Fish tape

Hole cut in wall

Bottom plate Fish tape

Cable will be pulled from
upstairs wall to downstairs wall

Joist cavity

Cable will be pulled

Joist cavity along joist cavity
from upstairs wall to
Top plate
downstairs wall

Hole cut in wall

To basement

First story Cutaway view Cutaway view

If there is no access space above and below a wall, cut openings in the finished walls to run a cable. This often occurs in
two-story homes when a cable is extended from an upstairs wall to a downstairs wall. Cut small openings in the wall near the top
and bottom plates, then drill an angled 1" hole through each plate. Extend a fish tape into the joist cavity between the walls and
use it to pull the cable from one wall to the next. If the walls line up one over the other (left), you can retrieve the fish tape using
a piece of stiff wire. If walls do not line up (right), use a second fish tape. After running the cable, repair the holes in the walls
with patching plaster or drywall scraps and taping compound.

Cutaway view

If you don’t have a fish tape, use a length of sturdy string and a lead weight or heavy Use a flexible drill bit, also called a
washer. Drop the line into the stud cavity from above, and then use a piece of stiff bell-hanger’s bit, to bore holes through
wire to hook the line from below. framing in finished walls.

40 THE COMPLETE GUIDE TO WIRING

 How to Install NM Cable in Finished Ceilings
If you don’t have access to a ceiling from above,
New fixture location
you can run cable for a new ceiling fixture from an
existing receptacle in the room up the wall and into
the ceiling without disturbing much of the ceiling.
Nail guard
Be sure not to tap into a restricted circuit such as
the kitchen countertop and bathroom receptacles.
To begin, run cable from the receptacle to the stud
cavity that aligns with the ceiling joists on which you
want to install a fixture. Be sure to plan a location for New switch location
the new switch. Remove short strips of drywall from
the wall and ceiling. Make a notch in the top plates. Existing
receptacle
Use a fish tape to pull the new cable up through the
wall cavity and the notch in top plates. Next use
the fish tape to pull the cable through the ceiling to
the fixture hole. When you are finished pulling the Access holes shown larger
cable, protect the notch with metal nail guards. After than necessary for clarity
having your work inspected, replace the drywall and
install the fixture and switch.

Fish a cable from the existing receptacle

location up to the notch at the top of
the wall. Protect the notch with a metal
nail stop.

Plan a route for running cable between

electrical boxes (see illustration above).
Remove drywall on the wall and ceiling
surface. Where cable must cross
3
framing members, cut a small access
opening in the wall and ceiling surface; Fish the cable through the ceiling to the
then cut a notch into the framing with a location of the new ceiling fixture. Install
wood chisel. nail guards over the notches.

WIRE, CABLE & CONDUIT 41

 Electrical Bonding
of Metal Conduit

Conduit Grounding screw

Pigtail
Pigtail

A ll individual wires (such as THHN/THWN) must

be installed in conduit or in thinner material called
tubing. Cables and wires that are subject to physical
damage must be installed in conduit or some types of
tubing to protect them. Whether a location is subject
Grounding
to physical damage depends on the judgment of the clip
electrical inspector. Cables that are exposed and are
within the reach of an adult and most cables installed
outside are often considered subject to physical Install a green insulated grounding wire for any circuit
damage. Other exposed locations may also qualify. that runs through metal conduit. Although code allows
The interior of conduit and tubing installed outside the metal conduit to serve as the grounding conductor,
most electricians install a green insulated wire as a
is considered a wet area. Don’t install NM cable inside
more dependable means of grounding the system. The
conduit installed outdoors. Use UF cable instead or pull grounding wires must be connected to metal boxes
individual wires rated for wet area use. Conduit and with a pigtail and grounding screw (left) or grounding
tubing installed outdoors must be rated for exterior use. clip (right).

Sweep forms a gradual 90° Elbow fitting (conduit body) is used

bend for ease in wire pulling. in tight corners or for long conduit
runs. The cover can be removed to
pull long lengths of wire.

Compression fittings
are used in outdoor
IMC installations,
where a rain‑tight
connection is needed.

Screw‑in connectors or setscrew

connectors are used to connect flexible
metal conduit.
Single‑hole & double‑hole pipe straps
hold conduit in place against walls.
Conduit should be supported within
3 ft. of each electrical box and fitting
and every 10 ft. thereafter. Nail straps are
driven into wooden
Flexible metal conduit (or liquid‑tight flexible conduit) in ½" and ¾" sizes is used where rigid conduit framing members to
is difficult to install. It often is used to connect permanently wired appliances, such as a water heater. anchor conduit.

42 THE COMPLETE GUIDE TO WIRING

Metal Conduit Fill Capacity Plastic Conduit

EMT
A

IMC
B

Rigid metal
conduit C

EMT (electrical metallic conduit) is EMT ½" in diameter can hold up to Plastic PVC conduit and tubing are
lightweight and easy to install. IMC twelve 14-gauge or nine 12-gauge allowed by many local codes. It is
(intermediate metallic conduit) has THHN/THWN wires (A), five 10-gauge assembled with solvent glue and
thicker galvanized walls and is a good wires (B), or three 8-gauge wires (C). PVC fittings that resemble those for
choice for exposed outdoor use. Rigid Use ¾" conduit for greater fill capacity. metal conduit. When wiring with PVC
metal conduit provides the greatest conduit and tubing, always run a green
protection for wires, but it is more grounding wire. Use material approved
expensive and requires threaded for use in electrical applications. Do not
fittings. EMT is the preferred metal use PVC plumbing pipes.
material for home use.

EMT is available in 10‑ft.

lengths and in ½", ¾", and 1¼"
diameters. EMT is used primarily Offset fitting connects an indoor
for exposed indoor installations. Setscrew coupling connects metal electrical box to a conduit
lengths of indoor metal conduit. anchored flush against a wall.

IMC is rated for outdoor LB conduit fitting is

use but can also be used used in outdoor
indoors. It is connected conduit installations.
with watertight fittings. It has watertight
It is available in 10‑ft. threaded fittings and
lengths and in ½" to a removable cover.
4" diameters.

WIRE, CABLE & CONDUIT 43

 Working with Conduit

EMT IMC PVC Flexible conduit

Conduit types used most in homes are EMT (electrical metallic tubing), IMC (intermediate metallic conduit), PVC (rigid
nonmetallic conduit), and flexible metal conduit. The most common diameters are ½" and ¾", but larger sizes are stocked
at most building centers.

RNC
(PVC)
fitting
LB

LB
PVC
offset

Access pull elbow

Nonmetallic conduit fittings typically are solvent welded to Liquid-tight flexible conduit (LFC) is used in outdoor
nonmetallic conduit, as opposed to metal conduit, which can applications, especially around pools and water features, at
be threaded and screwed into threaded fittings or attached irrigation controllers, and in air-conditioning condensers.
with setscrews or compression fittings.

44 THE COMPLETE GUIDE TO WIRING

 How to Make Nonmetallic Conduit Connections

2
Cut the rigid nonmetallic conduit (PVC) to length with a Deburr the cut edges with a utility knife or fine sandpaper
fine-tooth saw, such as a hacksaw. For larger diameter (1½" such as emery paper. Wipe the cut ends with a dry rag. Also
and above), use a power miter saw with a fine-tooth or plastic wipe the coupling or fitting to clean it.
cutting blade.

4
Apply a coat of PVC cement to the end of the conduit and to Insert the conduit into the fitting or coupling and twist it a
the inside walls of the coupling (inset). Wear latex gloves to quarter turn to help spread the cement. Allow the joint to set
protect your hands. The cement should be applied past the undisturbed for 10 minutes.
point on the conduit where it enters the fitting or coupling.

WIRE, CABLE & CONDUIT 45

 How to Install Conduit & Wires on a Concrete Wall
Drill pilot holes with a masonry bit, Open one knockout for each length of
then mount the box against the wall conduit that will be attached to the box.
with masonry anchors, or use masonry Attach an offset fitting to each knockout
anchors and panhead screws. using a locknut.

2 3

1 Offset
fitting
Measure from the floor to position
electrical boxes on the wall, and mark
location for mounting screws. Boxes for
receptacles in an unfinished basement
or other damp areas are mounted
at least 2 ft. from the floor. Laundry
receptacles usually are mounted at 48".

4 5 6

Measure the first length of conduit and Anchor the conduit against the wall Make conduit bends by attaching a
cut it with a hacksaw. Remove any with pipe straps and masonry anchors. sweep fitting using a setscrew fitting or
rough inside edges with a pipe reamer Conduit should be anchored within compression fitting. Continue attaching
or a round file. Attach the conduit 3 ft. of each box and fitting and every additional lengths. You can also use a
to the offset fitting on the box, and 10 ft. thereafter. conduit bender (inset) to make your
tighten the setscrew. own sweeps and bends.

46 THE COMPLETE GUIDE TO WIRING

Use an elbow fitting in conduit runs that At the panel, turn the power off and Unwind the fish tape and extend it
have many bends or in runs that require then remove the cover and test for through the conduit from the circuit
very long wires. The cover on the elbow power. Open a knockout in the panel, breaker panel outward. Remove the
fitting can be removed to make it easier attach a setscrew fitting, and install the cover on an elbow fitting when extending
to extend a fish tape and pull wires. last length of conduit. the fish tape around tight corners.

7 8 9

Retrieve the wires through the conduit

by pulling on the fish tape with
steady pressure.

NOTE: Use extreme care when using

a metal fish tape inside a circuit
breaker panel, even when the power is
turned off.

11

10 12
Trim back 2" of outer insulation from the Clip off the taped ends of the wires.
end of the wires, and then insert the Leave at least 2 ft. of wire at the service
wires through the loop at the tip of the panel and 3" extending beyond the
fish tape. front edges at each electrical box.

WIRE, CABLE & CONDUIT 47

Boxes & Panels

A ll wiring connections must be housed within

a box that is accessible. The box may be as
simple as a small handy box for making a splice or
as complex as a 200‑amp main service panel. It is
typically rectangular, square, round, or octagonal, but
be aware that the boxes are shaped as they are for
specific reasons, so make sure you are using the right
one for the job.
Installing a box that is too small is an extremely
common wiring mistake that is easy to understand:
small boxes cost less. But they are not one‑size fits all.
The smallest common boxes, called handy boxes, may
be used only for a single device (such as a switch or
receptacle) with no more than three conductors. Be
sure to refer to a box fill chart (see page 50) to learn
which size and shape box is required for your job.
Electrical panels function like other electrical
boxes insofar as they house connections, but they also
house breakers or fuses and other parts that transmit
power from the service entry to the individual
circuits. Subpanels are smaller electrical panels that
perform the same function but are supplied by the
main service panel so they can distribute power into
multiple circuits in a remote location.

In this chapter:
• Electrical Boxes
• Installing Boxes
• Electrical Panels

BOXES & PANELS 49

 ELECTRICAL BOX FILL CHART
BOX SIZE MAXIMUM NUMBER OF CONDUCTORS
AND SHAPE PERMITTED (SEE NOTES BELOW)
WIRE SIZE 8 AWG 10 AWG 12 AWG 14 AWG
JUNCTION BOXES

Electrical Boxes 4 × 1¼" R or O

4 × 1½" R or 0
5
5
5
6
5
6
6
7
4 × 2 ⁄8" R or O
1
7 8 9 10
4 × 1¼" S 6 7 8 9

T he National Electrical Code requires that wire

connections and cable splices be contained inside
an approved metal or plastic box. The box shields
4 × 1½" S
4 × 21⁄8" S
7
10
8
12
9
13
10
15
4 ⁄16 × 1¼" S
11
8 10 11 12
framing members and other flammable materials
from electrical sparks and protects people from 4 ⁄16 × 1½" S
11
9 11 13 14
being shocked. 4 ⁄16 × 2 ⁄8" S
11 1
14 16 18 21
Electrical boxes come in several shapes. DEVICE BOXES
Rectangular and square boxes are used for switches 3 × 2 × 1½" 2 3 3 3
and receptacles. Rectangular (2 × 3") boxes are used
3 × 2 × 2" 3 4 4 5
for single switches or duplex receptacles. Square
3 × 2 × 2¼" 3 4 4 5
(4 × 4") boxes are used any time it is convenient for
two switches or receptacles to be wired, or “ganged,” 3 × 2 × 2½" 4 5 5 6

in one box. Octagonal electrical boxes contain wire 3 × 2 × 2¾" 4 5 6 7

connections for ceiling fixtures. 3 × 2 × 3½" 6 7 8 9
Electrical boxes are available in different depths. A 4 × 2 ⁄8 × 1½"
1
3 4 4 5
box must be deep enough so a switch or receptacle can 4 × 21⁄8 × 17⁄8" 4 5 5 6
be removed or installed easily without crimping and
4 × 2 ⁄8 × 2 ⁄8"
1 1
4 5 6 7
damaging the circuit wires. The box must also be large
enough to safely dissipate the heat from wires, switches, NOTES:
and receptacles. This is an important fire safety rule. • R = Round; O = Octagonal; S = Square or rectangular
• Each hot or neutral wire entering the box is counted
as one conductor.
• Grounding wires are counted as one conductor in
Correct
total—do not count each one individually.
• Raceway fittings and external cable clamps do not
count. Internal cable connectors and straps count
as either half or one conductor, depending on type.
• Devices (switches and receptacles mainly) each
count as two conductors.
Overfilled
• When calculating total conductors, any nonwire
components should be assigned the gauge of the
largest wire in the box.
• For wire gauges not shown here, contact your local
electrical inspections office.

Replace an undersized box with a larger box using the

Octagonal boxes usually contain wire connections for ceiling Electrical Box Fill Chart (above) as a guide. In addition
fixtures. Because the ceiling fixture attaches directly to the to the maximum box fill allowed by the chart, the area of
box, the box should be anchored firmly to a framing member. all wires, taps, and splices should not exceed 75 percent
A properly installed octagonal box should support a ceiling
fixture weighing up to 50 pounds. Any box must be covered
of the box area. The NEC also says that all electrical
with a tightly fitting cover plate, and the box must not have boxes must remain accessible. Never cover an electrical
open knockouts. Do not overfill the box (inset). box with drywall, paneling, or wallcoverings.

50 THE COMPLETE GUIDE TO WIRING

Common Electrical Boxes

Metal braces

Detachable side Adapter cover

Rectangular boxes are used with wall Square 4" × 4" boxes are large enough Braced octagonal boxes fit between
switches and duplex receptacles. for most wiring applications. They are ceiling joists. The metal braces extend
Single‑size rectangular boxes (shown used for cable splices and ganged to fit any joist spacing and are nailed or
above) may have detachable sides that receptacles or switches. To install one screwed to framing members.
allow them to be ganged together to switch or receptacle in a square box,
form double‑size boxes. use an adapter cover.

Foam gasket

Outdoor boxes have sealed seams Old work boxes can be installed to Plastic boxes are common in new
and foam gaskets to guard a switch replace older boxes or to allow you construction. The box may include
or receptacle against moisture. to add new additional receptacles preattached nails for anchoring it to
Corrosion‑resistant coatings protect all and switches. One type (above) has framing members. Wall switches must
metal parts. Code‑compliant models built‑in clamps that tighten against the have grounding screws if installed in
include a watertight hood that protects backside of the drywall and hold the plastic boxes.
even when the outlet is in use. box in place.

BOXES & PANELS 51

 D

3½"-deep plastic boxes with preattached mounting nails are used for any wiring project protected by finished walls. Common
styles include single‑gang (A), double‑gang (B), and triple‑gang (C). Double‑gang and triple‑gang boxes require internal cable
clamps. Metal boxes (D) should be used for exposed indoor wiring, such as conduit installations in an unfinished basement.
Metal boxes also can be used for wiring that will be covered by finished walls. Plastic retrofit boxes (E) are used when a new
switch or receptacle must fit inside a finished wall. Use internal cable clamps.

B
C

D
F
E

Additional electrical boxes include cast aluminum box (A) for use with outdoor fixtures, including receptacles that are wired
through metal conduit (these must have in‑use covers if they house receptacles); old work ceiling box (B) used for light fixtures;
light‑duty ceiling fan box (C) with brace that spans ceiling joists; heavy‑duty retrofit ceiling fan box (D) designed for retrofit; PVC
box (E) for use with PVC conduit in indoor or outdoor setting; vapor‑proof ceiling box with foam gasket (F).

52 THE COMPLETE GUIDE TO WIRING

 BOX SPECIFICATIONS

High-quality nonmetallic boxes are rigid and don’t contort Boxes larger than 2 × 4" and all retrofit boxes must have
easily. A variety of adapter plates are available, including internal cable clamps. After installing cables in the box,
junction box cover plate (A), single‑gang (B), double‑gang tighten the cable clamps over the cables so they are
(C), and light fixture (D). Adapter plates come in several gripped firmly, but not so tightly that the cable sheathing
thicknesses to match different wall constructions. is crushed.

Grounding screw

Pigtail

A B C

Metal boxes must be bonded to the circuit grounding Cables entering a metal box must be clamped. A variety of
system. Connect the circuit grounding wires to the box clamps are available, including plastic clamps (A, C) and
with a green insulated pigtail wire and wire connector (as threaded metal clamps (B).
shown) or with a grounding clip (page 42).

BOXES & PANELS 53

 Nonmetallic Boxes
Nonmetallic electrical boxes have taken over much
of the do‑it‑yourself market. Most are sold prefitted
with installation hardware—from metal wings to
10d common nails attached at the perfect angle
for a nail‑in box. The bulk of the nonmetallic boxes
sold today are inexpensive blue PVC. You can also
purchase heavier‑duty fiberglass or thermoset
plastic models that provide a nonmetallic option
for installing heavier fixtures such as ceiling fans
and chandeliers.
In addition to cost and availability, nonmetallic
boxes hold a big advantage over metal boxes in that
their resistance to conducting electricity will prevent
a sparking short circuit if a hot wire contacts the
box. Nonmetallic boxes generally are not approved Low cost is the primary reason that plastic PVC nail‑in boxes
for exposed areas, where they may be susceptible are so popular. Not only are they inexpensive, but they also
feature built‑in cable clamps. The standard plastic nail‑in box
to damage. Their lack of rigidity also allows them to
is prefitted with a pair of 10d common nails for attaching to
compress or distort, which can reduce the interior exposed wall studs.
capacity beyond code minimums or make outlets
difficult to attach.

B
A

Nonmetallic boxes for home use include a single‑gang, double‑gang, triple gang, and quad boxes (A); thermoset and fiberglass
boxes for heavier duty (B); and round fixture boxes (C) for ceiling installation (nail‑in and with integral metal bracket).

54 THE COMPLETE GUIDE TO WIRING

Working with Nonmetallic Boxes

Tab C

Nail-in boxes (A) are prefitted with 10d

nails that are attached perpendicular to
the face of single‑gang boxes and at an
inward angle for better gripping power
Do not break off the tabs that cover cable entry holes in plastic boxes. These are on larger boxes. Side‑mount boxes (B)
not knockouts as you would find in metal boxes. In single‑gang boxes (right), the feature a nailing plate that is attached
pressure from the tab is sufficient to secure the cable as long as it enters with to the front of the stud to automatically
sheathing intact and is stapled to the framing no more than 8" from the box. On create the correct setback; adjustable
larger boxes (left), you will find traditional knockouts intended to be used with side‑mount boxes (C) are installed
plastic cable clamps that resemble metal cable clamps. Use these for heavier‑gauge the same way but can be moved
cable and cable with more than three wires. on the bracket.

Ribs

Integral ribs cast into many nonmetallic boxes are used to

Distortion can occur in nonmetallic boxes when nails or other register the box against the wall studs so the front edges
fasteners are overdriven or installed at improper angles, or of the box will be flush with the wall surface after drywall is
when the semiflexible boxes are compressed into improperly installed. Most are set for ½" drywall, but if your wall material
sized or shaped openings. This can reduce the box capacity will be a different thickness, or if you are going to install
and prevent devices and faceplates from fitting. something like a mirror on the wall, you may be able to find
a box with corresponding ribs. Otherwise, use a piece of the
wallcovering material as a reference.

BOXES & PANELS 55

 Installing Boxes

I nstall electrical boxes for receptacles, switches, and

fixtures only after your wiring project plan has been
approved by your inspector. Use your wiring plan as
a guide, and follow all applicable height and spacing
guidelines when laying out box positions.
Always use the deepest electrical boxes that
are practical for your installation. Using deep
boxes ensures that you will meet code regulations
regarding box volume and makes it easier to make the
wire connections.
Some electrical fixtures, such as recessed light
fixtures, electric heaters, and exhaust fans, have
built‑in wire connection boxes. Install the frames for
these fixtures at the same time you are installing the
other electrical boxes. The box heights recommended
Electrical boxes in adjacent rooms should be positioned close
on the following pages are for most situations. Box together when they share a common wall and are controlled
heights for Americans with Disabilities Act (ADA) by the same circuit. This simplifies the cable installations and
compliance are different. also reduces the amount of cable needed.

Fixtures That Do Not Need Electrical Boxes

Wire connection box

Recessed fixtures that fit inside wall cavities have built‑in wire connection boxes and require no additional electrical boxes.
Common recessed fixtures include electric blower‑heaters (left), bathroom exhaust fans (right), and recessed light fixtures.
Install the frames for these fixtures at the same time you are installing the other electrical boxes along the circuit. Surface‑
mounted fixtures such as electric baseboard heaters (pages 238–242) and undercabinet fluorescent lights (pages 214–217)
also have built‑in wire connection boxes. These fixtures are not installed until it is time to make the final hookups.

56 THE COMPLETE GUIDE TO WIRING

 How to Install Electrical Boxes for Receptacles

1 2
1
⁄ 2"

Mark the location of each box on studs. Standard receptacle Position each box against a stud so the front face will be flush
boxes should be centered 12" above floor level. GFCI with the finished wall. For example, if you will be installing ½"
receptacle boxes in a bathroom should be mounted so they drywall, position the box so it extends ½" past the face of the
will be about 10" above the finished countertop. stud, plus the thickness of any additional material, such as tile
or a mirror. Anchor the box by driving the mounting nails into
the stud.

3 4 5

Adapter
plate

If installing square boxes, attach the Open one knockout for each cable that Break off any sharp edges that might
adapter plates before positioning the will enter the box using a hammer and damage vinyl cable sheathing by
boxes. Use adapter plates that match screwdriver. Always introduce the new rotating a screwdriver in the knockout.
the thickness of the finished wall. cable through the knockout that is
Anchor the box by driving the mounting farthest way from the wall stud.
nails into the stud.

BOXES & PANELS 57

 How to Install Boxes for Light Fixtures

1 Mounting bracket

Wallboard
Internal clamp

2 Cutaway view
Brace bar

Position the light fixture box for a vanity To position a light fixture between joists, attach an electrical box to an adjustable
light above the frame opening for a brace bar. Nail the ends of the brace bar to joists so the face of the box will be flush
mirror or medicine cabinet. Place the with the finished ceiling surface. Slide the box along the brace bar to the desired
box for a ceiling light fixture in the center position, and then tighten the mounting screws. Use internal cable clamps when
of the room or as desired. Position each using a box with a brace bar.
box against a framing member so the
front face will be flush with the finished NOTE: For ceiling fans and heavy fixtures, use a metal box and a heavy-duty brace
wall or ceiling, and then anchor the bar rated for heavy loads (inset photo).
box by driving the mounting nails into
the framing.

How to Install Boxes for Switches

1 2
Cross block

48"

46"

Install switch boxes at accessible locations, usually on the To install a switch box between studs, first install a cross block
latch side of a door, with the center of the box 48" from the between studs, with the top edge 46" above the floor. Position
floor. The box for a thermostat is mounted at 48" to 60". the box on the cross block so the front face will be flush
Position each box against the side of a stud so the front face with the finished wall, and drive the mounting nails into the
will be flush with the finished wall, and drive the mounting cross block.
nails into the stud.

58 THE COMPLETE GUIDE TO WIRING

 How to Locate Electrical Boxes

72"

45" 45"
45"

12"

12"
6"

Heights of electrical boxes vary depending on use. In the kitchen shown here, boxes above the countertop are 45" above the floor,
in the center of 18" backsplashes that extend from the countertop to the cabinets. All boxes for wall switches also are installed
at this height. The center of the box for the microwave receptacle is 72" off the floor. The centers of the boxes for the range and
food disposer receptacles are 12" off the floor, but the center of the box for the dishwasher receptacle is 6" off the floor.

Typical Wallcovering Thickness

1
⁄ 2" 7
⁄ 8" 3
⁄ 4" 5
⁄ 8"

A B C D

Consider the thickness of finished walls when mounting electrical boxes against framing members. Code requires that the front face
of boxes be flush with the finished wall surface, so how you install boxes will vary depending on the type of wall finish that will be
used. For example, if the walls will be finished with ½" drywall (A), attach the boxes so the front faces extend ½" past the front of
the framing members. With ceramic tile and drywall or cementboard (B), extend the boxes 7⁄8" past the framing members. With
¼" Corian® over drywall (C), boxes should extend ¾"; and with drywall and laminate (D), boxes should extend 5⁄8".

BOXES & PANELS 59

 Ceiling Boxes
Shown cutaway

Joist
Brace

A heavy-duty brace is required for

Ceiling boxes for lights are generally round or octagonal in anchoring boxes that will support
shape to fit typical lamp mounting plates. The easiest way to heavy chandeliers and ceiling
install one is by nailing the brace to open ceiling joists from fans. A remodeling brace such as
above. If the ceiling is insulated, pull the insulation away the one seen here is designed to
from the box if the fixture you’re installing is not rated IC for install through a small cutout in
insulation contact. the ceiling (inset photo).

How to Install a Junction Box

1 2
Splices outside of a box
are a code violation.

Knockout

Turn off power to circuit wires at the main service panel. Test Open one knockout for each cable that will enter the box using
for power. Carefully remove any tape or wire connectors from a hammer and screwdriver. Any unopened knockouts should
the exposed splice. Disconnect the wires. remain sealed.

60 THE COMPLETE GUIDE TO WIRING

 3 4 5

Locknut

Cable clamp

Cable sheathing

Anchor the electrical box to a wooden Thread each cable end through a Insert the cables into the electrical
framing member using screws or nails. cable clamp. Tighten the clamp with a box, and screw a locknut onto each
screwdriver. See if there is any slack in cable clamp.
the cables so you can gain a little extra
cable to work with.

Locknut

Grounding screw

Lugs

Cover plate

6 7 8
Tighten the locknuts by pushing against Use wire connectors to reconnect Carefully tuck the wires into the box,
the lugs with the blade of a screwdriver. the wires. Pigtail the copper grounding and attach the cover plate. Turn on the
wires to the green grounding screw in power to the circuit at the main service
the back of the box (required only for panel. Make sure the box remains
metal boxes). accessible and is not concealed by
wall or ceiling finishes.

BOXES & PANELS 61

 A pop‑in box typically has wings, tabs, or brackets
that are drawn tight against the wall surface on the
Installing Pop‑In wall cavity side, holding the box in place. It can be
made either of metal or plastic.
(Old Work) Retrofit Boxes
Attaching an electrical box to a wall stud during new A
construction is relatively easy (pages 54 to 57). The task
B
becomes complicated, however, when you’re working
in finished walls during remodeling or repair. In most D
cases, it’s best to use an electronic stud finder, make a
large cutout in the wall, and attach a new box directly
to a framing member or bracing (and then replace and
refinish the wall materials). But there are occasions
when this isn’t possible or practical and you just need
to retrofit an electrical box without making a large hole
in the wall. You also may find that an older switch or
receptacle box is too shallow to accommodate a new
dimmer or GFCI safely. These situations call for a pop‑in
retrofit box (sometimes called an “old work” box).

E C
TOOLS & MATERIALS
Pop-in boxes for remodeling come in a variety of styles.
Screwdriver Wallboard saw For walls, they include plastic retrofit boxes with flip‑out
Pencil Template (if provided) wings (A), metal or plastic boxes with compression tabs or
brackets (B), metal retrofit boxes with folding wings (C), and
String Plastic or metal pop‑in box metal boxes with bendable brackets, also known as F‑straps
Electrical tape Eye protection or Madison clips, (D). For ceilings, plastic fixture boxes with
flip‑out wings (E) are available.

How to Replace an Electrical Box

1 2

To install a dimmer switch or GFCI receptacle, you may have to Bind the cable ends together and attach string in case they fall
replace an old, overcrowded box. Shut off power and remove into the wall cavity when the old box is removed. Disconnect
the old switch or receptacle. Identify the location of nails the cable clamps and slide the old box out. Install a new
holding the box to the framing member and cut the nails with pop‑in box (see opposite).
a hacksaw or reciprocating saw with a metal blade inserted
between the box and the stud.

62 THE COMPLETE GUIDE TO WIRING

 How to Install a Pop‑In Box

1 2 3

Use a template to trace a cutout for Puncture the drywall with the tip of a Pull NM cable through a knockout in
the box at the intended location. If no drywall saw or by drilling a small hole the box (no cable clamp is required
template is provided, press the pop‑in inside the lines, and make the cutout with a plastic box; just be sure not to
box against the wall surface and trace for the box. break the pressure tab that holds the
its front edges (but not the tabs on the cable in place).
top and bottom).

4
Bracket arms

Flip-out wings

Inside tab

Bracket arms

VARIATION: Feed cable into the new

box and secure it in the opening
after clamping the cables. With
this pop‑in box, bracket arms are
Back of wall inserted at the sides of the box
(top) and then bent around the
Insert the box into the cutout so the front flanges are flush against the wall surface. front edges to secure the box in
Tighten the screws that cause the flip‑out wings to pivot (right) until the box is held the opening (bottom).
firmly in place. Connect the switch or receptacle that the box will house.

BOXES & PANELS 63

 Electrical Panels 200-Amp Service Panel

E very home has a main panel that distributes

electrical current to the individual circuits.
The main panel may be found in the basement,
garage, utility area, or on an exterior wall and can be
identified by its metal cabinet. Before making any
repair to your electrical system, you must shut off
power to the correct circuit at the main panel or at
the subpanel where the circuit begins. Every circuit in
every panel should be labeled (see page 22) so circuits
can be identified easily.
Panels vary in appearance, depending on the age
of the system. Very old wiring may operate on 30‑amp
service that has only two circuits. New homes can
have up to 400‑amp service with 30 or more circuits.
You can usually find the size of the service by reading
the amperage rating printed on the main fuse block or
main circuit breakers.
Regardless of age, all panels have circuit breakers
or fuses (see pages 66–69) that protect each circuit
from overloads. In general, older service panels use
fuses, while newer panels use circuit breakers.
In addition to the main panel, your electrical
system may have one or more subpanels that protect
some of the circuits in the home. A subpanel has its
own circuit breakers or fuses.
The subpanel resembles the main service panel
but is usually smaller. It may be located near the main
panel, or it may be found near the areas served by
the new circuits. Garages and basements that have
been updated often have their own subpanels. If your
home has subpanels, make sure that their circuits are
indexed correctly.
When handling fuses or circuit breakers, make
sure the area around the panel is dry. Never remove
the protective cover on the panel. After turning off The main panel is the heart of your wiring system. As our
demand for household energy has increased, the panels
a circuit to make electrical repairs, remember to have also grown in capacity. Today, a 200‑amp panel is
always test the circuit for power before touching often installed in new construction. Many homebuilders are
any wires. installing dual 200‑amp panels in larger houses.

64 THE COMPLETE GUIDE TO WIRING

 A circuit breaker panel providing
100-Amp Service Panel
Main circuit breaker 100 amps or more of current is
Protective (dead front) cover common in wiring systems installed
during the 1960s and later. A circuit
breaker panel is housed in a gray
metal cabinet that contains two rows
of individual circuit breakers. You can
often determine service size by reading
the amperage rating of the main circuit
breakers. In systems rated 200 amps
and below, the main breaker is often
located in the main panel, but it may be
in a separate cabinet located elsewhere.

Larger new homes may have 300‑ or

400‑amp service. These systems may
have a single 300‑ or 400‑amp panel or
two 150‑ or 200‑amp panels.

100-amp service is now the minimum

standard for all new housing. It is
adequate for a medium‑sized house
with no more than three major electric
appliances. However, larger houses
with more electrical appliances require
a service panel that provides 150 amps
Panel index or more.
Circuit breaker
To shut off power to individual circuits
in a circuit breaker panel, flip the lever
on the appropriate circuit breaker to the
60-Amp Fuse Panel OFF position. To shut off the power to
Main fuse block the entire house, turn the main circuit
Plug fuse breaker(s) to the OFF position.

Some older homes may still have a

60‑amp fuse panel. It usually is housed
in a gray metal cabinet that contains
four individual plug fuses, plus one
or two pull‑out fuse blocks that hold
cartridge fuses. A 60‑amp panel is
considered undersized by current
standards. This type of system should
be upgraded for both convenience
and safety. Insurance companies and
mortgage lenders may require a
complete electrical system upgrade
before issuing a homeowner insurance
policy or approving mortgage financing.

To shut off power to a circuit, carefully

unscrew the plug fuse, touching only
its insulated rim. To shut off power to
the entire house, hold the handle of the
main fuse block and pull sharply to
remove it. Major appliance circuits are
controlled with separate cartridge fuse
Panel index
Protective cover Appliance fuse block blocks. Shut off an appliance circuit by
pulling out its fuse block.

BOXES & PANELS 65

 Circuit Breaker Panels
The circuit breaker panel is the electrical distribution is to connect the wires to new circuit breakers at the
center for your home. It divides the current into panel. Follow basic safety procedures and always shut
branch circuits that are carried throughout the house. off the main circuit breaker and test for power before
Each branch circuit is protected by a circuit breaker touching any parts inside the panel. Never touch the
that protects the wires from dangerous current service wire lugs. If unsure of your own skills, hire
overloads. When installing new circuits, the last step an electrician to make the final circuit connections.

MAIN CIRCUIT BREAKER PANEL

DISTRIBUTES THE POWER
ENTERING THE HOME INTO
BRANCH CIRCUITS.

120-volt
branch Grounding conductor
Service lugs: Never touch
circuits leads to metal grounding
these. They are always
live unless the utility rods driven into the
shuts off the service earth or to other
to the panel. The NEC grounding electrodes.
requires protective covers
(service barriers) on the
two hot service lugs (see
page 119). Two hot service wires
each provide 120 volts of
power to the main circuit
breaker. These wires are
always hot.
Neutral service wire
carries current back to the
power source after it has Grounding bus bar has
passed through the home. terminals for linking
grounding wires to
the main grounding
conductor. It is bonded to
Main circuit breaker the neutral bus bar.
protects the panelboard
from overloads and
disconnects power to all Two hot bus bars run
circuits in the panel. through the center of the
panel, supplying power to
the circuit breakers. Each
Neutral terminal bar has carries 120 volts.
setscrew terminals for
linking all neutral circuit
wires to the neutral
service wire. Subpanel feeder
breaker is a double-pole
breaker. It is wired
Single-pole breaker in the same way as a
connects to one hot 120/240-volt circuit.
bus bar to provide 120
volts to circuit.

120/240-volt
branch circuit
Double-pole breaker
connects to both hot legs
of the bus bar to provide
240 volts.

66 THE COMPLETE GUIDE TO WIRING

(If you have an older electrical service with fuses instead of circuit
breakers, always have an electrician make these final hookups.) SAFETY WARNING
If a circuit breaker panel does not have enough open slots for new Never touch any parts inside a circuit
full‑size circuit breakers, you may be able to install ½‑height (slimline) breaker panel until you have checked
circuit breakers. Otherwise, you will need to install a subpanel. for power (see page 70). Circuit
Before installing any new wiring, evaluate your electrical service breaker panels differ in appearance,
to make sure it provides enough current to support both the existing depending on the manufacturer.
wiring and any new circuits. If your service does not provide enough Never begin work in a circuit breaker
current, you will need to upgrade to a panel with a higher amp rating panel until you understand its layout
and enough extra breaker slots for the new circuits you want to install. and can identify the parts.

CIRCUIT BREAKER SUBPANEL

CAN BE INSTALLED WHEN THE
MAIN CIRCUIT BREAKER PANEL
DOES NOT HAVE ENOUGH SPACE Neutral bus bar has
Grounding bus bar has
TO HOLD CIRCUIT BREAKERS setscrew terminals
setscrew terminals
for linking neutral
FOR NEW CIRCUITS YOU WANT circuit wires to the for connecting circuit
TO INSTALL. neutral feed wire. Single-pole circuit breaker grounding wires. In a
transfers 120 volts of circuit breaker subpanel,
power from one hot bus the grounding bus bar is
bar to the black hot wire in not bonded to the neutral
Two hot bus bar.
a two-wire cable.
feeder wires
supply
120 volts 120-volt
of power to branch circuit
the two hot
bus bars.

Neutral feeder
wire connects
the neutral
bus bar in the
subpanel to
the neutral 120-volt isolated
bus bar in ground circuit
the main
service panel.

240-volt
branch circuit

Feeder cable brings power

Two hot bus bars pass Double-pole breaker wired for 240 volts
from the main circuit breaker
through the center of the transfers power from both hot bus bars to
panel. A 30-amp, 240-volt
service panel, supplying white and black hot wires in a two-wire
subpanel requires a 10/3
power to the individual cable. A 240-volt circuit has no neutral wire
feeder cable controlled
circuit breakers. Each carries connection; the white wire is tagged with
by a 30-amp double-pole
120 volts of power. black tape to identify it as a hot wire.
circuit breaker.

EXERCISE YOUR BREAKERS

Your breakers (including the main) should be “exercised” once a year to ensure proper mechanical function. Simply turn
them off and then back on. A convenient time to perform the exercise is at daylight saving time, when you’ll need to reset
all of your clocks anyway.

BOXES & PANELS 67

 Circuit Breakers & Fuses
Circuit breakers and fuses are safety devices designed 15-amp 20-amp single-pole 30-amp
to protect the electrical system from short circuits single-pole (120-volt) single-pole
and overloads. Circuit breakers and fuses are located (120-volt) (120-volt)

in the main service panel and in subpanels. GFCI

Most panels installed before about 1965 rely on circuit
fuses to protect individual circuits. Screw‑in plug breaker
fuses protect 120‑volt circuits that power lights and
receptacles. Cartridge fuses protect 240‑volt appliance
circuits and the main shutoff of the service panel.
Inside each fuse is a current‑carrying metal alloy
ribbon. If a circuit is overloaded, the metal ribbon
melts and stops the current flow. A fuse must match
the amperage rating of the circuit. Never replace a 40-amp
AFCI circuit
double-pole
fuse with one that has a larger amperage rating. breaker
(240-volt)
In most panels installed after about 1965, circuit
breakers protect individual circuits. Single‑pole circuit Circuit breakers are found in the majority of panels installed
breakers protect 120‑volt circuits, and double‑pole since the 1960s. Single‑pole breakers control 120‑volt
circuits. Double‑pole breakers rated for 20 to 60 amps control
circuit breakers protect 240‑volt circuits. Amperage
240‑volt circuits. Ground‑fault circuit interrupter (GFCI)
ratings for circuit breakers range from 15 to over provides protection from shocks. Arc‑fault circuit interrupter
200 amps. (AFCI) breakers provide protection from fire‑causing arcs for
Each circuit breaker has a permanent metal strip the entire circuit.
that heats up and bends when current passes through
it. If a circuit is overloaded, the metal strip inside the
breaker bends enough to “trip” the switch and stop Cartridge fuses
the flow of power. Many circuit breakers are designed
to trip only two times. After the second trip, a circuit
breaker may not trip when it is supposed to. Consider
replacing a circuit breaker that has tripped twice.
When a fuse blows or a circuit breaker trips, it
may be because there are too many light fixtures and
plug‑in appliances drawing power through the circuit.
Move some of the plug‑in appliances to another
circuit, and then replace the fuse or reset the breaker. If
the fuse blows or the breaker trips again immediately,
there may be a short circuit in the system. Call a
licensed electrician if you suspect a short circuit.

Old-style fuse
boxes can accept “S” type fuse
modern “S” Time-delay
type fuses if you
use an Edison Regular plug fuse Regular plug fuse
Tamperproof fuses
adapter. Be
sure to screw Fuses are used in older panels. Plug fuses usually control
the fuse into the 120‑volt circuits rated for 15, 20, or 30 amps. Tamperproof
adapter first, and plug fuses have threads that fit only matching sockets,
then screw the making it impossible to install a wrong‑sized fuse. Time‑delay
assembly into fuses absorb temporary heavy power loads without blowing.
Edison adapter
the socket. Cartridge fuses control 240‑volt circuits and range from 30 to
100 amps.

68 THE COMPLETE GUIDE TO WIRING

 How to Identify & Replace a Blown Plug Fuse

1 2

Locate the blown fuse at the panel. If the metal ribbon inside is Unscrew the fuse, being careful to touch only the insulated
cleanly melted (left), the circuit was overloaded. If window is rim of the fuse. Replace it with a fuse that has the same
discolored (right), there was a short circuit. amperage rating.

How to Remove, Test & Replace a Cartridge Fuse

2 3
Remove cartridge fuses by gripping the Remove the individual cartridge fuses Test each fuse using a continuity tester.
handle of the fuse block and pulling from the block using a fuse puller. If the tester glows, the fuse is good. If
out sharply. not, install a new fuse with the same
amperage rating.

How to Reset and Test a Circuit Breaker

1 Tripped
circuit 2 3
breaker

Open the service panel and locate Reset the tripped circuit breaker Test AFCI and GFCI circuit breakers by
the tripped breaker. The lever on the by pressing the circuit breaker lever all pushing the TEST button. The breaker
tripped breaker will be either in the OFF the way to the OFF position and then should trip to the OFF position. If
position or in a position between ON pressing it to the ON position. not, the breaker is faulty and must
and OFF. be replaced.

BOXES & PANELS 69

 Connecting Circuit Breakers
The last step in a wiring project is connecting circuits
at the breaker panel. After this is done, the work is
ready for the final inspection.
Circuits are connected at the main panel, if it has
enough open slots, or at a circuit breaker subpanel
(see pages 64–67). When working at a subpanel, make
Setscrew terminals
sure the feeder breaker at the main panel has been
turned off, and test for power (see photo, right) before
Neutral terminal bar
touching any parts in the subpanel.
Make sure the circuit breaker amperage does
not exceed the ampacity of the circuit wires you are
connecting to it. Also be aware that circuit breaker
styles and installation techniques vary according
to manufacturer. Use breakers made by the panel
manufacturer. You should install AFCI circuit breakers for
most 15‑ and 20‑amp, 120‑volt circuits inside the home.
Test for current before touching any parts inside a circuit
breaker panel. With the main breaker turned off but all other
TOOLS & MATERIALS breakers turned on, touch one probe of a neon tester to
the neutral terminal bar, and touch the other probe to each
Screwdriver Circuit tester setscrew on one of the double‑pole breakers (not the main
breaker). If the tester does not light for either setscrew, it is
Hammer Pliers safe to work in the panel.
Pencil Cable clamps
NOTE: Noncontact voltage testers are preferred in most
Combination tool Single‑ and double‑pole situations where you are testing for current because they‘re
Cable ripper AFCI circuit breakers safer. But in some instances, you’ll need a tester with
individual probes to properly check for current.

How to Connect Circuit Breakers

Open a knockout in the side of
the circuit breaker panel using a
screwdriver and hammer. Attach a 3
cable clamp to the knockout.

1 Hold the cable across the front of the

panel near the knockout, and mark the
Shut off the main circuit breaker in the sheathing about ½" inside the edge
main service panel (if you are working of the panel. Strip the cable from the
in a subpanel, shut off the feeder marked line to the end using a cable
breaker in the main panel). Remove ripper. (There should be 18" to 24" of
the panel cover plate, taking care not excess cable.) Insert the cable through
to touch the parts inside the panel. Test the clamp and into the service panel,
for power (photo, above right). and then tighten the clamp.

70 THE COMPLETE GUIDE TO WIRING

 Cable clamp

4 5 6
Bend the bare copper grounding wire For 120-volt circuits, bend the white Strip ½" of insulation from the end of
around the inside edge of the panel circuit wire around the outside of the the black circuit wire. Insert the wire
to an open setscrew terminal on the panel to an open setscrew terminal on into the setscrew terminal on a new
grounding terminal bar. Insert the the neutral terminal bar. Clip away excess single‑pole circuit breaker, and tighten
wire into the opening on the terminal wire, and then strip ½" of insulation the setscrew.
bar, and tighten the setscrew. Fold from the wire using a combination tool.
excess wire around the inside edge Insert the wire into the terminal opening,
of the panel. and tighten the setscrew.

Neutral terminal bar

120-volt circuit

240-volt circuit

7 8 9
Slide one end of the circuit breaker onto For 120/240-volt circuit (top): Connect Remove the appropriate breaker tab
the guide hook, and then press it firmly red and black wires to the double‑pole on the panel cover plate to make
against the bus bar until it snaps into breaker. Connect white wire to the room for the new circuit breaker. A
place. (Breaker installation may vary, neutral terminal bar, and the ground‑ single‑pole breaker requires one tab,
depending on the manufacturer.) Fold ing wire to grounding terminal bar. while a double‑pole breaker requires
excess black wire around the inside For 240‑volt circuits without a neutral two tabs. Reattach the cover plate,
edge of the panel. (bottom), attach white and black wires and label the new circuit on the panel
to the double‑pole breaker, tagging white door index.
wire with black tape. There is no neutral
terminal bar connection on this circuit.

BOXES & PANELS 71

Switches

A mong wiring devices, switches fail with surprising

frequency. If you’ve carefully wired a new circuit
or a fixture and you know you got it right, but when
you turn on the power it doesn’t work, you should
direct your attention to any switches in the line. Even
brand-new switches can fail to function correctly.
This is why most professional electricians will pay
the extra couple of dollars to buy a quality switch out
of the gate. It is also why most of them routinely test
each switch for continuity before installing it (see
pages 88–91).
The most basic switches for home wiring are
single-pole switches, which control only one fixture
and have only two screw (or push-in) terminals (not
counting the grounding screw). Next, three-way
switches and four-way switches have more
installation possibilities and control circuits that are
more complicated to wire. Dimmer switches, isolated
ground switches, and motion-sensor switches are
some of the other switch options.
Use caution when you handle switches. The wires
are usually attached to screw terminals on the sides of
the fitting, which makes them very easy to contact if
you grab the switch. Always shut off the power to the
switch before removing the switch cover plate. Also
shut off the power at the service panel if you will be
working downstream from the switch—never count
on a switch that is open to function as a breaker.

In this chapter:
• Wall Switches
• Types of Wall Switches
• Specialty Switches
• Testing Switches

SWITCHES 73
 specialty switch, make sure it is compatible with the
wiring configuration and size of the switch box.

NOTICE: Two changes in the NEC affect how new

switch wiring should be installed. These changes do
not affect existing switch wiring. The pictures and
instructions in this book about replacing existing

Wall Switches switches show wiring that does not comply with
these new requirements. This is because you will
probably see noncompliant wiring for many years
to come. Pictures and instructions about installing

A n average wall switch is turned on and off more

than 1,000 times each year. Because switches
receive constant use, wire connections can loosen and
new switch wiring show wiring that complies with
these new requirements.
One change requires that a wire with white insulation
switch parts gradually wear out. If a switch no longer should not supply current to a light or a switched
operates smoothly, it must be replaced. receptacle, even when the wire is marked as hot. A black
The methods for replacing a switch vary slightly, or red colored wire should supply current to the outlet. A
depending on the switch type and its location along white colored wire, marked as hot, may supply current to
an electrical circuit. When working on a switch, the switch when wiring 3-way and 4-way switches.
use the photographs on pages 76–87 to identify The other change requires that a neutral wire
your switch type and its wiring configuration. be available at switch boxes. An exception allows
Individual switch styles may vary from manufacturer you to ignore this requirement if the switch box
to manufacturer, but the basic switch types is accessible from above or below, such as from a
are universal. basement, crawlspace, or attic. This new requirement
It is possible to replace most ordinary wall is intended to allow easier installation of devices, such
switches with a specialty switch, such as a timer as intelligent switch controllers, that need power for
switch or an electronic switch. When installing a controller operation.

A typical wall switch has

a movable metal arm that Ground terminal
opens and closes the
electrical circuit. When
the switch is ON, the arm
completes the circuit
and power flows between
the screw terminals and
through the black hot
wire to the light fixture.
When the switch is OFF,
the arm lifts away to
interrupt the circuit, and
no power flows. Switch
problems can occur if
Metal arm
the screw terminals are
not tight or if the metal
arm inside the switch
wears out.
Power out
NOTE: The switch at
Screw terminals
right has had part of
its housing removed
so the interior Power in
workings can be seen.
Switches or fixtures
that are not in original
condition should never Switch housing cut away for clarity
be installed.

74 THE COMPLETE GUIDE TO WIRING

Rotary snap switches are found Push‑button switches were widely Toggle switches were introduced in
in many installations completed used from 1920 until about 1940. the 1930s. This early design has a
between 1900 and 1920. The handle Many switches of this type are still switch mechanism that is mounted in a
is twisted clockwise to turn light on in operation. Reproductions of ceramic housing sealed with a layer of
and off. The switch is enclosed in a this switch type are available for insulating paper.
ceramic housing. restoration projects.

Toggle switches were improved during Mercury switches became common in Electronic motion‑sensor switches have
the 1950s and are now the most the early 1960s. They conduct electrical an infrared eye that senses movement
commonly used type. This switch type current by means of a sealed vial of and automatically turns on lights when
was the first to use a sealed plastic mercury. No longer manufactured for a person enters a room. Motion‑sensor
housing that protects the inner switch home use, old mercury switches are switches can provide added security
mechanism from dust and moisture. considered a hazardous waste. against intruders.

SWITCHES 75
 used in combination with a pair of three-way switches
to control a set of lights from three or more locations.
Identify switch types by counting the screw
terminals. Single-pole switches have two
screw terminals, three-way switches have three screw
terminals, and four-way switches have four. Most
switches include a grounding screw terminal, which is

Types of Wall Switches identified by its green color.

When replacing a switch, choose a new switch
that has the same number of screw terminals as the
old one. The location of the screws on the switch

W all switches are available in three general types.

To reconnect or replace a switch, it is important
to identify its type.
body varies depending on the manufacturer, but these
differences will not affect the switch operation.
Whenever possible, connect switches using the
Single-pole switches are used to control a set of screw terminals rather than push-in fittings. Some
lights from one location. Three-way switches are used specialty switches (pages 84–87) have wire leads
to control a set of lights from two different locations instead of screw terminals. They are connected to
and are always installed in pairs. Four-way switches are circuit wires with wire connectors.

A wall switch is connected to circuit

wires with screw terminals or with
push‑in fittings on the back of the
switch. A switch may have a stamped
strip gauge that indicates how much
insulation must be stripped from the
circuit wires to make the connections.

The switch body is attached to a metal

mounting strap that allows it to be Push‑in fittings
mounted in an electrical box. Several
rating stamps are found on the strap Grounding screw
and on the back of the switch. The
Amperage
abbreviation UL or UND. LAB. INC. & voltage ratings Wire
LIST means that the switch meets the
gauge
safety standards of the Underwriters rating
Laboratories. Switches also are stamped
with maximum voltage and amperage
ratings. Standard wall switches are Screw terminals Wire
rated 15A or 125V. Voltage ratings of strip
110, 120, and 125 are considered to be gauge
identical for purposes of identification.

For standard wall switch installations,

choose a switch that has a wire gauge
Wire compatibilty ratings
rating of #12 or #14. For wire systems
with solid‑core copper wiring, use only
switches marked COPPER, CU, or CO/ Underwriters
Laboratories Wire release
ALR. For aluminum wiring, use only
(UL) approved opening for
switches marked CO/ALR. Note that push‑in fittings
while CO/ALR switches and receptacles
are approved by the National Electrical
Code for use with aluminum wiring, the Mounting screw
Consumer Products Safety Commission
does not recommend using these.
Switches and receptacles marked Mounting strap
AL/CU can no longer be used with Front Back
aluminum wiring, according to the
National Electrical Code.

76 THE COMPLETE GUIDE TO WIRING

 NOTE: Position
of the screw
Single‑Pole Wall Switches Grounding
terminals on
a switch may
screw vary, depending
A single-pole switch is the most common type of wall on manufacturer.
switch. It has ON-OFF markings on the switch lever and is
used to control a set of lights, an appliance, or a receptacle
from a single location. A single-pole switch has two screw
terminals and a grounding screw. When installing a Switch lever Two screw
single-pole switch, check to make sure the ON marking terminals
shows when the switch lever is in the up position.
In a correctly wired single-pole switch, a hot circuit wire
is attached to each screw terminal. However, the color and
number of wires inside the switch box will vary, depending
on the location of the switch along the electrical circuit.
If two cables enter the box, then the switch lies in the
middle of the circuit. In this installation, both of the hot
wires attached to the switch are black.
If only one cable enters the box, then the switch lies
at the end of the circuit. In this installation (sometimes
A single‑pole switch is essentially an interruption in the
called a switch loop), one of the hot wires is black, but the black power supply wire that is opened or closed with the
other hot wire usually is white. A white hot wire should be toggle. Single‑pole switches are the simplest of all home
coded with black tape or paint. wiring switches.

Typical Single‑Pole Switch Installations

Grounding Power out
wires
Power out Grounding wire
Neutral out

Available
Grounding neutral
Neutral in
Power in Power in wire

Two cables enter the box when a switch Old method: One cable enters the box New method: In new switch wiring, the
is located in the middle of a circuit. when a switch is located at the end white wire should not supply current
Each cable has a white and a black of a circuit. In this installation, both of to the switched device and a separate
insulated wire, plus a bare copper the insulated wires are hot. The white neutral wire should be available in the
grounding wire. The black wires are wire should be labeled with black tape switch box.
hot and are connected to the screw or paint to identify it as a hot wire. The
terminals on the switch. The white wires grounding wire is connected to the
are neutral and are joined together with switch grounding screw.
a wire connector. Grounding wires are
pigtailed to the switch.

SWITCHES 77
 Three‑Way Wall Switches
Three-way switches have three screw terminals and
do not have ON-OFF markings. Three-way switches
are always installed in pairs and are used to control a
set of lights from two locations.
One of the screw terminals on a three-way switch
Traveler screw
is darker than the others. This screw is the common terminals
screw terminal. The position of the common screw
terminal on the switch body may vary, depending on
the manufacturer. Before disconnecting a three-way
switch, always label the wire that is connected to the
common screw terminal. It must be reconnected to Common screw
the common screw terminal on the new switch. terminal
The two lighter-colored screw terminals on
a three-way switch are called the traveler screw
terminals. The traveler terminals are interchangeable,
so there is no need to label the wires attached to them. Grounding screw
Because three-way switches are installed in terminals
pairs, it sometimes is difficult to determine which of
the switches is causing a problem. The switch that
receives greater use is more likely to fail, but you may
need to inspect both switches to find the source of
the problem.

Typical Three‑Way Switch Installation

Two cables enter the box: One cable has
Traveler screw terminals Grounding wires Two‑wire cable two wires, plus a bare copper grounding
wire; the other cable has three wires,
plus a ground. The black wire from the
two‑wire cable is connected to the dark
common screw terminal. The red and
black wires from the three‑wire cable
are connected to the traveler screw
terminals. The white neutral wires are
joined together with a wire connector,
and the grounding wires are pigtailed to
the switch grounding terminal.

Common screw terminal Three‑wire cable

78 THE COMPLETE GUIDE TO WIRING

 How to Replace a Three‑Way Wall Switch

1 2

Turn off the power to the switch at the panel, and then remove Test for power by touching the probe of a noncontact voltage
the switch cover plate and mounting screws. Holding the tester to each wire and screw terminal. Tester should not
mounting strap carefully, pull the switch from the box. Be glow. If it does, there is still power entering the box. Return
careful not to touch the bare wires or screw terminals until to the panel, and turn off the correct circuit, then test again
they have been tested for power. for power.

NOTE: If you are installing a new switch circuit, you must

provide a neutral conductor at the switch.

3 4 5

Common screw terminal Common screw terminal

Locate the dark common screw Connect the common wire to the dark Connect the remaining two circuit wires
terminal, and use masking tape to common screw terminal on the switch. to the screw terminals. These wires
label the “common” wire attached to it. On most three‑way switches, the common are interchangeable and can be
Disconnect wires and remove switch. screw terminal is black. Or it may be connected to either screw terminal.
Test the switch for continuity. If it tests labeled with the word COMMON stamped Carefully tuck the wires into the box.
faulty, buy a replacement. Inspect wires on the back of the switch. Reconnect the Remount the switch, and attach the
for nicks and scratches. If necessary, grounding screw, and connect it to the cover plate. Turn on the power at
clip damaged wires and strip them. circuit grounding wires with a pigtail. the panel.

SWITCHES 79
 Four‑Way Wall Switches
Four-way switches have four screw terminals and
do not have ON-OFF markings. Four-way switches
are always installed between a pair of three-way
switches. This switch combination makes it possible Line 1 screw
to control a set of lights from three or more locations. terminals
Four-way switches are common in homes where
large rooms contain multiple living areas, such as a
kitchen opening into a dining room. Switch problems
in a four-way installation can be caused by loose
connections or worn parts in a four-way switch or in
one of the three-way switches (facing page). Line 2 screw
terminals
In a typical installation, there will be a pair of
three-wire cables that enter the box for the four-way
switch. With most switches, the black and red wires
from one cable should be attached to the bottom or
top pair of screw terminals, and the black and red
wires from the other cable should be attached to the NOTE: Position of
the screw terminals
remaining pair of screw terminals. However, not all on a switch may
switches are configured the same way, and wiring vary, depending
configurations in the box may vary, so always study on manufacturer.
the wiring diagram that comes with the switch.

Common Four‑Way Switch Installation

Available
neutral
Grounding wires

Four wires are connected to a four‑way switch. The black and Switch variation: Some four‑way switches have a wiring
red wires from one cable are attached to the top pair of screw guide stamped on the back to help simplify installation. For
terminals, while the black and red wires from the other cable are the switch shown above, one pair of color‑matched circuit
attached to the bottom screw terminals. In new switch wiring, wires will be connected to the screw terminals marked LINE
the white wires are joined and bypass the switch but remain 1, while the other pair of wires will be attached to the screw
available for future use. terminals marked LINE 2.

80 THE COMPLETE GUIDE TO WIRING

 How to Replace a Four‑Way Wall Switch

1 2

Turn off the power to the switch at the panel, and then remove the switch cover plate Disconnect the wires and inspect them
and mounting screws. Holding the mounting strap carefully, pull the switch from for nicks and scratches. If necessary,
the box. Be careful not to touch any bare wires or screw terminals until they have clip damaged wires and strip them.
been tested for power. Test for power by touching each wire and terminal with a Test the switch for continuity (pages
noncontact voltage tester. The tester should not glow. If it does, there is still power 88–91). Buy a replacement if the
entering the box. Return to the panel, and turn off the correct circuit. switch tests faulty.

3 4

Connect two hot wires from one incoming cable to the top set Attach remaining hot wires to the other set of screw terminals.
of screw terminals. Pigtail the grounding wires to the grounding screw. Carefully
tuck the wires inside the switch box, and then remount the
switch and cover plate. Turn on power at the panel.

SWITCHES 81
 Double Switches
A double switch has two switch levers in a single
housing. It is used to control two light fixtures or
appliances from the same switch box.
Tab
In most installations, both halves of the
switch are powered by the same circuit. In these
single-circuit installations, three wires are connected To
fixtures Ground
to the double switch. One wire, called the feed
wire (which is hot), supplies power to both halves
of the switch. The other wires, called the switch
leg, carry power out to the individual light fixtures Feed

or appliances.
In rare installations, each half of the switch Single‑circuit wiring: Three black wires are attached to the
is powered by a separate circuit. In these switch. The black feed wire bringing power into the box is
connected to the side of the switch that has a connecting tab.
separate-circuit installations, four wires are
The wires carrying power out to the light fixtures or appliances
connected to the switch, and the metal connecting are connected to the side of the switch that does not have
tab joining two of the screw terminals is removed (see a connecting tab. The white neutral wires are connected
photo below). together with a wire connector.

Note: Switch must be

UL‑listed and labeled Connecting tab
for use as a multi‑
To fixture
circuit switch.

Tab
removed

Ground

Feed

Separate‑circuit wiring: Four black wires are attached to the switch. Feed wires from Remove the connecting tab on a
the power source are attached to the side of the switch that has a connecting tab, double switch when wired in a
and the connecting tab is removed (photo, right). Wires carrying power from the switch separate‑circuit installation. The tab
to light fixtures or appliances are connected to the side of the switch that does not have can be removed with needlenose pliers
a connecting tab. White neutral wires are connected together with a wire connector. or a screwdriver.

82 THE COMPLETE GUIDE TO WIRING

Pilot‑Light Switches Neutral

Tab
A pilot-light switch has a built-in
bulb that glows when power flows Silver
through the switch to a light fixture or
appliance. Pilot-light switches often
are installed for convenience if a light
To fixture
fixture or appliance cannot be seen
from the switch location. Basement Brass
lights, garage lights, and attic exhaust Grounds
fans frequently are controlled by
pilot-light switches.
A pilot-light switch requires a
neutral wire connection. A switch box
Feed wire
that contains a single two-wire cable
has only hot wires and cannot be
fitted with a pilot-light switch. Pilot‑light switch wiring: Three wires are connected to the switch. One black
wire is the feed wire that brings power into the box. It is connected to the brass
(gold) screw terminal on the side of the switch that does not have a connecting
tab. The white neutral wires are pigtailed to the silver screw terminal. The black
wire carrying power out to a light fixture or appliance is connected to the screw
Switch/Receptacles terminal on the side of the switch that has a connecting tab.

A switch/receptacle combines
a grounded receptacle with a
Ground Neutral wires
single-pole wall switch. In a room
that does not have enough wall Silver
receptacles, electrical service can be Tab
improved by replacing a single-pole
switch with a switch/receptacle.
A switch/receptacle requires a
neutral wire connection. A switch
box that contains a single two-wire
To fixture
cable has only hot wires and cannot Brass
be fitted with a switch/receptacle.
Grounds
A switch/receptacle can be
installed in one of two ways. In the
most common installations, the
receptacle is hot even when the
switch is off (photo, right). Feed
In rare installations, a switch/
receptacle is wired so the receptacle
is hot only when the switch is on. Switch/receptacle wiring: Three wires are connected to the switch/receptacle. One
In this installation, the hot wires of the hot wires is the feed wire that brings power into the box. It is connected to
the side of the switch that has a connecting tab. The other hot wire carries power
are reversed, so that the feed wire is
out to the light fixture or appliance. It is connected to the brass screw terminal on
attached to the brass screw terminal the side that does not have a connecting tab. The white neutral wire is pigtailed
on the side of the switch that does not to the silver screw terminal. The grounding wires must be pigtailed to the green
have a connecting tab. grounding screw on the switch/receptacle and to the grounded metal box.

SWITCHES 83
 and they are easy to install. Electronic switches are
durable, and they rarely need replacement.
Most specialty switches have preattached wire
leads instead of screw terminals and are connected to
circuit wires with wire connectors. Some motor-driven
timer switches require a neutral wire connection and
cannot be installed in switch boxes that have only one

Specialty Switches cable with two hot wires. It is precisely due to the rise
in popularity of “smart” switches that the NEC Code
was changed in 2014 to require an available neutral
wire in newly installed switch boxes.

Y our house may have several types of specialty

switches. Dimmer switches (pages 86–87) are
used frequently to control light intensity in dining
If a specialty switch is not operating correctly, you
may be able to test it with a continuity tester. Timer
switches and time-delay switches can be tested for
and recreation areas. Timer switches and time-delay continuity, but dimmer switches cannot be tested.
switches (below) are used to control light fixtures With electronic switches, the manual switch can
and exhaust fans automatically. Electronic switches be tested for continuity, but the automatic features
provide added convenience and home security, cannot be tested.

Countdown timer switch. This rocker‑type switch gives you the Programmable timer switch. A digital or dial‑type timer allows
option to easily program the switch to shut off after a specified you to program the switch to turn on for specific time periods
time: from 5 to 60 minutes. Garage lights or basement lights at designated times of day within a 24‑hour cycle. Security
are good applications: anywhere you want the light to stay on lights, space heaters, towel warmers, and radiant floors are
long enough to allow you to exit, but not to stay on indefinitely. typical applications.
These switches often are used to control exhaust fans.

84 THE COMPLETE GUIDE TO WIRING

Occupancy sensor. Many smart switches incorporate a motion Spring‑wound timer switch. A relatively simple device, this
detector that will switch the lights on if they sense movement timer switch functions exactly like a kitchen timer, employing
in the room and will also shut them off when no movement a hand‑turned dial to and spring mechanism to shut the
is detected for a period of time. The model shown above also switch off in increments up to 15 minutes.
has a dimmer function for further energy savings.

Daylight sensor switch. This switch automatically turns on Smart switches let you control lights from a smart phone or
when light levels drop below a proscribed level. It can also be other compatible device, such as a smart speaker, without
programmed as an occupancy sensor to shut off when the the need for a central hub (a common requirement with early
room is vacant and turn on when the room is entered. smart home systems).

SWITCHES 85
 Dimmer Switches Switch Action Options
A dimmer switch makes it possible to vary the
brightness of a light fixture. Dimmers are often
installed in dining rooms, recreation areas, or
bedrooms. Do not install a dimmer at stairway light
Toggle‑type dimmers
switches unless you install a dimmer at all switches. resemble standard switches.
Any standard single-pole switch can be replaced Toggle dimmers are available
with a dimmer, as long as the switch box is of adequate in both single‑pole and
three‑way designs.
size. Dimmer switches have larger bodies than The model shown supports
standard switches. They also generate a small amount incandescent, fluorescent,
of heat that must dissipate. For these reasons, dimmers and LED dimmable blubs.
should not be installed in undersized electrical boxes
or in boxes that are crowded with circuit wires. Always
follow the manufacturer’s specifications for installation.
In lighting configurations that use three-way
switches (pages 78–79), buy a packaged pair of
three-way dimmers designed to work together.
Dimmer switches are available in several styles (see
photo, right). All types have wire leads instead of screw Dial‑type dimmers are
the most common style.
terminals, and they are connected to circuit wires using
Rotating the dial changes the
wire connectors. Some types have a green grounding light intensity.
lead that should be connected to the grounded metal
box or to the bare copper grounding wires. Until recently,
dimmers were designed to work only with incandescent
lamps. They may not work well, or may not work at all,
with CFL and LED lamps. When replacing incandescent
lamps with CFL and LED lamps, make sure the new
lamps are designed to work with older dimmers. When
replacing dimmers, make sure the new dimmers are
designed to work with CFL and LED lamps.
Slide‑action dimmers have
illuminated faces that make
the switch easy to locate in
TOOLS & MATERIALS the dark.

Screwdriver Needlenose Wire connectors

Circuit tester pliers Masking tape

TIP: AUTOMATIC DIMMERS

An automatic dimmer has
an electronic sensor that Rocker type switches control
dimmable incandescent,
adjusts the light fixture to
fluorescent, LED, or
compensate for the changing halogen bulbs.
levels of natural light. An
automatic dimmer also
can be operated manually.
For another example, see
page 85, lower left.

86 THE COMPLETE GUIDE TO WIRING

 How to Install a Dimmer Switch

1 2

Turn off power to the switch at the panel, and then remove Disconnect the circuit wires and remove the switch. Straighten
the cover plate and mounting screws. Holding the mounting the circuit wires, and clip the ends, leaving about ½" of the
straps carefully, pull the switch from the box. Be careful not bare wire end exposed.
to touch bare wires or screw terminals until they have been
tested for power. In new switch wiring, the white wire should
not supply current to the switched device, and a separate
neutral wire should be available in the switch box.

3 4

Connect the wire leads on the dimmer switch to the A three‑way dimmer has an additional wire lead. This
circuit wires using wire connectors. The switch leads are “common” lead is connected to the common circuit wire.
interchangeable and can be attached to either of the two When replacing a standard three‑way switch with a dimmer,
hot circuit wires. the common circuit wire is attached to the darkest screw
terminal on the old switch. In new switch wiring, the white
wire should not supply current to the switched device, and a
separate neutral wire should be available in the switch box.

SWITCHES 87
 Testing Switches
Clip

A switch that does not work properly may have

worn or broken internal parts. Test switches with
a battery-operated continuity tester. The continuity
Probe

tester detects any break in the metal pathway inside

the switch. Replace the switch if the continuity tester
shows the switch to be faulty.
Never use a continuity tester on wires that might
carry live current. Always shut off the power and
disconnect the switch before testing for continuity.
Some specialty switches, such as dimmers, cannot be
tested for continuity. Electronic switches can be tested
for manual operation using a continuity tester, but the
automatic operation of these switches cannot be tested.

Low‑voltage bulb
How to Test
a Single‑Pole Wall Switch

A continuity tester uses battery‑generated current to test the

Attach the clip of the tester to one of the screw terminals. metal pathways running through switches and other electrical
Touch the tester probe to the other screw terminal. Flip fixtures. Always “test” the tester before use. Touch the tester
the switch lever from ON to OFF. If the switch is good, the clip to the metal probe. The tester should glow. If not, then
tester glows when the lever is ON but not when it’s OFF. the battery or lightbulb is dead and must be replaced.

88 THE COMPLETE GUIDE TO WIRING

 How to Test a Three‑Way Wall Switch

1 Traveler screw terminals 2

Common screw terminal

Attach the tester clip to the dark common screw terminal. Touch Touch the probe to the other traveler screw terminal, and flip
the tester probe to one of the traveler screw terminals, and flip the switch lever back and forth. If the switch is good, the
the switch lever back and forth. If the switch is good, the tester tester will glow only when the switch lever is in the position
should glow when the lever is in one position, but not both. opposite from the positive test in step 1.

How to Test a Four‑Way Wall Switch

1 2

A B
A B A B A B

C D C D C D C D

Test the switch by touching the probe and clip of the continuity If the switch is good, the test will show a total of four
tester to each pair of screw terminals (A‑B, C‑D, A‑D, B‑C, continuous pathways between screw terminals—two
A‑C, B‑D). The test should show continuous pathways pathways for each lever position. If not, then the switch
between the two different pairs of screw terminals. Flip the is faulty and must be replaced. (The arrangement
lever to the opposite position, and repeat the test. It should of the pathways may differ, depending on the switch
show continuous pathways between two different pairs of manufacturer. The photo above shows the three possible
screw terminals. pathway arrangements.)

SWITCHES 89
 How to Test a Pilot‑Light Switch

1 2
Test the pilot light by flipping the switch lever to the ON Test the switch by disconnecting the unit. With the switch lever in
position. Check to see if the light fixture or appliance is the ON position, attach the tester clip to the top screw terminal
working. If the pilot light does not glow even though the on one side of the switch. Touch the tester probe to the top
switch operates the light fixture or appliance, then the pilot screw terminal on the opposite side of the switch. If the switch is
light is defective and the unit must be replaced. good, the tester will glow when switch is ON but not when OFF.

How to Test a Timer Switch

1 2
Attach the tester clip to the red wire lead on the timer switch, Rotate the dial clockwise until the OFF tab passes the arrow
and touch the tester probe to the black hot lead. Rotate the marker. The tester should not glow. If it does, the switch is
timer dial clockwise until the ON tab passes the arrow marker. faulty and must be replaced.
The tester should glow. If it does not, the switch is faulty and
must be replaced.

90 THE COMPLETE GUIDE TO WIRING

 How to Test How to Test How to Test
a Switch/ a Double a Time‑Delay
Receptacle Switch Switch

Attach the tester clip to one of the Test each half of the switch by attaching Attach the tester clip to one of the
top screw terminals. Touch the tester the tester clip to one screw terminal wire leads, and touch the tester probe
probe to the top screw terminal on and touching the probe to the opposite to the other lead. Set the timer for a
the opposite side. Flip the switch lever side. Flip the switch lever from ON to few minutes. If the switch is working
from ON to OFF position. If the switch OFF position. If the switch is good, the correctly, the tester will glow until the
is working correctly, the tester will tester glows when the switch lever is ON time expires.
glow when the switch lever is ON but but not when it’s OFF. Repeat the test with
not when it’s OFF. the remaining pair of screw terminals. If
either half tests faulty, replace the unit.

How to Test Manual Operation of Electronic Switches

2 Manual switch lever

Manual switch lever

Manual
switch
1 lever 3
Automatic switch: Attach the tester clip Programmable switch: Attach the Motion‑sensor switch: Attach the
to a black wire lead, and touch the tester clip to a wire lead, and touch tester clip to a wire lead, and touch
tester probe to the other black lead. the tester probe to the other lead. the tester probe to the other lead.
Flip the manual switch lever from ON Flip the manual switch lever from ON Flip the manual switch lever from ON
to OFF position. If the switch is working to OFF position. If the switch is working to OFF position. If the switch is working
correctly, the tester will glow when the correctly, the tester will glow when the correctly, the tester will glow when the
switch lever is ON but not when it’s OFF. switch lever is ON but not when it’s OFF. switch lever is ON but not when it’s OFF.

SWITCHES 91
Receptacles

W hether you call them outlets, plug-ins, or

receptacles, these important devices represent the
point where the rubber meets the road in your home
wiring system. From the basic 15-amp, 120-volt duplex
receptacle to the burly 50-amp, 240-volt appliance
receptacle, the many receptacles in your home do pretty
much the same thing: transmit power to a load.
Learning the differences among receptacles does
not take long. You need to know the amperage and
voltage, and the number of devices on the circuit
to select the correct receptacle. For circuits with
one receptacle, match the circuit and receptacle
amperage and voltage. A duplex receptacle (with a
space for two plugs) counts as two receptacles. Use
15-amp receptacles on 15-amp circuits with multiple
receptacles. Use either 15- or 20-amp receptacles on
20-amp circuits with multiple receptacles. Twenty-amp
receptacles have the horizontal slot that forms a T with
the large slot. Receptacles for 240-volt service have
unique slot configurations so you can’t accidentally
plug in an appliance that’s not rated for the amperage
in the circuit. Some receptacles provide protection
against dangerous situations such as ground faults
and arc faults tripping themselves off if they detect a
problem. Ground-fault (GFCI) and arc-fault (AFCI)
receptacles are easy to identify by the test and reset
buttons on their faces.
One last bit of information about receptacles: like
switches, they vary quite a bit in quality. Paying the
extra couple of dollars for a well made, durable device
is worth the money.

In this chapter:
• Types of Receptacles
• Receptacle Wiring
• GFCI Receptacles
• Testing Receptacles

RECEPTACLES 93
 Types of Receptacles

S everal different types of receptacles are found in

the typical home. Each has a unique arrangement
of slots that accepts only a certain kind of plug, and
should be rated for 110, 115, 120, or 125 volts. For
purposes of replacement, these ratings are considered
identical. High-voltage receptacles are rated at 220, 240,
each is designed for a specific job. or 250 volts. These ratings are considered identical.
Household receptacles provide two types of voltage: When replacing a receptacle, check the amperage
normal and high. Although voltage ratings have rating of the circuit at the main service panel, and buy
changed slightly over the years, normal receptacles a receptacle with the correct amperage rating.

15 amps, 120 volts. Polarized two‑slot 15 amps, 120 volts. Three‑slot 20 amps, 120 volts. This three‑slot
receptacles are common in homes built grounded receptacles have two grounded receptacle features a special
before 1960. Slots are different sizes to different‑sized slots and a U‑shaped T‑shaped slot. It is installed for use with
accept polarized plugs. hole for grounding, which is required in large appliances or portable tools that
all new wiring installations. require 20 amps of current.

15 amps, 240 volts. This receptacle 30 amps, 120/240 volts. This grounded 50 amps, 120/240 volts. This new
is used primarily for window air receptacle is used for clothes dryers. grounded receptacle is used for ranges.
conditioners. It is available as a single It provides high‑voltage current for The high voltage powers heating coils,
unit or as half of a duplex receptacle, heating coils and 120 volts to run lights and the 120‑volts run clocks and lights.
with the other half wired for 120 volts. and timers.

94 THE COMPLETE GUIDE TO WIRING

Older Receptacles
Older receptacles may look different from more modern types, but most will stay in good working order.
Follow these simple guidelines for evaluating or replacing older receptacles:

• Never replace a receptacle with one of a different • If in doubt, contact an electrician.

voltage or higher amperage rating.
• Never alter the prongs of a plug to fit an older
• Do not replace a two-slot receptacle with a three- receptacle. Altering the prongs may remove the
slot receptacle. Replace the two-slot receptacle grounding or polarizing features of the plug.
with a polarized two-slot receptacle or with a
GFCI receptacle.

The earliest receptacles were Unpolarized receptacles have same‑ Surface‑mounted receptacles were
modifications of the screw‑in light‑ length slots. Modern plugs may not fit popular in the 1940s and 1950s for their
bulb. This receptacle was used in the these receptacles. Never modify the ease of installation. Wiring ran behind
early 1900s. prongs of a polarized plug to fit the slots hollowed‑out base moldings. These
of an unpolarized receptacle. receptacles are usually ungrounded.

Ceramic duplex receptacles were Twist‑lock receptacles are designed to This ceramic duplex receptacle has
manufactured in the 1930s. They are be used with plugs that are inserted and a unique hourglass shape. It is rated
polarized but ungrounded, and they are rotated. A small tab on the end of one for 250 volts but only 5 amps and
wired for 120 volts. of the prongs prevents the plug from would not be allowed by today’s
being pulled from the receptacle. electrical codes.

RECEPTACLES 95
 High‑Voltage Receptacles
Grounding wire
High-voltage receptacles provide current to large
appliances such as clothes dryers, ranges, and air
conditioners. The slot configuration of a high-voltage Red hot wire
receptacle (page 94) will not accept a plug rated for
120 volts.
A high-voltage receptacle can be wired in one White neutral wire
of two ways. In one type of high-voltage receptacle,
voltage is brought to the receptacle with two hot
wires, each carrying a maximum of 120 volts. No Black hot wire
white neutral wire is necessary, but a grounding
wire should be attached to the receptacle and to the
receptacle box (if it is metal).
A clothes dryer or range also may require 120 volts
to run lights, timers, and clocks. If so, a white neutral
wire will be attached to the receptacle. The appliance Screw
itself will split the incoming electricity into a 120-volt terminals
circuit and a 240-volt circuit.
When replacing a high-voltage receptacle, it
is important to identify and tag all wires on the
existing receptacle so that the new receptacle will be
A receptacle rated for 120/240 volts has two incoming hot
properly wired. wires, each carrying 120 volts, a white neutral wire, and a
copper grounding wire. Connections are made with setscrew
terminals at the back of the receptacle.

Hard plastic box

Screw terminals
Grounding
wires

Black hot wire Red hot wire

Green ground wire

White hot wire Black hot wire
coded black Screw terminals
for hot White neutral wire
Conduit

One type of receptacle rated for 240 volts has two incoming This surface‑mounted receptacle rated for 240 volts has a hard
hot wires and no neutral wire. A grounding wire is pigtailed to plastic box that can be installed on concrete or block walls.
the receptacle and to the metal receptacle box. Surface‑mounted receptacles are often found in basements
and utility rooms.

96 THE COMPLETE GUIDE TO WIRING

Childproofing
Tamper-resistant (TR) receptacles are now required in all new residential
installations and when replacing an existing 3-slot receptacle. Tamper-
resistant receptacles contain an internal safety device that prevents a child
from inserting an object into the receptacle slots and getting a shock.
For standard existing receptacles, you can make them childproof or
adapt them for special uses by adding receptacle accessories. Before
installing an accessory, be sure to read the manufacturer’s instructions.
Homeowners with small children should add inexpensive caps or
covers to guard against accidental electric shocks.
Plastic caps do not conduct electricity and are virtually impossible
for small children to remove. A receptacle cover attaches directly to the
receptacle and fits over plugs, preventing the cords from being removed.

Tamper‑resistant receptacles are labeled

with "TR" on their faces. Use them for
all new installations and replacements
of 3‑slot receptacles (including GFCI
and AFCI types).

Standard receptacles present a real shock hazard to small children. Fortunately Cover standard receptacles with
there are many products that make receptacles safer without making them childproofing plugs to prevent children
less convenient. from having access to the slots.

RECEPTACLES 97
 Duplex Receptacles
Stamp of approval Push‑in The standard duplex receptacle has two halves for receiving
Long Mounting fitting plugs. Each half has a long (neutral) slot, a short (hot) slot,
(neutral) strap and a U‑shaped grounding hole. The slots fit the wide prong,
slot narrow prong, and grounding prong of a three‑prong plug.
Wire
Short (hot) slot ratings This ensures that the connection between receptacle and
Silver plug will be polarized and grounded for safety.
(neutral) Grounding Wire
screw hole type Wires are attached to the receptacle at screw terminals or
terminals push‑in fittings. A connecting tab between the screw terminals
Connecting allows a variety of different wiring configurations. Receptacles
tab
also include mounting straps for attaching to electrical boxes.
Stamps of approval from testing agencies are found on the
Brass (hot) front and back of the receptacle. Look for the symbol UL or
screw UND. LAB. INC. LIST to make sure the receptacle meets the
terminals strict standards of Underwriters Laboratories.

Voltage The receptacle is marked with ratings for maximum volts

rating and amps. The common receptacle is marked 15A, 125V.
Amperage
Receptacles marked CU or COPPER are used with solid copper
rating
Green wire. Those marked CU‑CLAD ONLY are used with copper‑coated
(grounding) aluminum wire. Only receptacles marked CO/ALR may be used
screw terminal with solid aluminum wiring. Receptacles marked AL/CU no
FRONT BACK longer may be used with aluminum wire, according to code.

AFCI receptacles have integral protection against arc faults The ground‑fault circuit‑interrupter, or GFCI, receptacle is a
and may be required in some remodeling situations where modern safety device. When it detects slight changes in current,
AFCI protection cannot be provided at the panel. it instantly shuts off power. The larger picture shows a modern
GFCI with an alert bulb that lights when the device is tripped.
The older but more familiar style is seen in the inset photo.

98 THE COMPLETE GUIDE TO WIRING

 COMMON RECEPTACLE PROBLEMS
Household receptacles, also called outlets, have no moving parts to wear out and usually last for many years. Most
problems associated with receptacles are actually caused by faulty lamps and appliances or their plugs and cords.
However, the constant plugging in and removal of appliance cords can wear out the metal contacts inside a receptacle.
Any receptacle that does not hold plugs firmly should be replaced. In addition, older receptacles made of hard plastic may
harden and crack with age. They must be replaced when this happens.

A loose wire connection with the receptacle box is another possible problem. A loose connection can spark (called arcing),
trip a circuit breaker, or cause heat to build up in the receptacle box, creating a potential fire hazard.

Wires can come loose for a number of reasons. Everyday vibrations caused by walking across floors, or from nearby
street traffic, may cause a connection to shake loose. In addition, because wires heat and cool with normal use, the ends
of the wires will expand and contract slightly. This movement also may cause the wires to come loose from the screw
terminal connections. Another common cause is wires coming loose from push‑in wire connections.

Not all receptacles are created equally. When replacing, make sure to buy one with the same amp rating as the old one.
Inadvertently installing a 20‑amp receptacle in replacement of a 15‑amp receptacle is a very common error.

PROBLEM REPAIR

Circuit breaker trips repeatedly or fuse burns out immediately 1. Repair or replace worn or damaged lamp or appliance cord.
after being replaced. 2. Move lamps or appliances to other circuits to prevent overloads.
3. Tighten any loose wire connections.
4. Clean dirty or oxidized wire ends.
5. Bad AFCI, especially those from the early 2000s. Replace AFCI.

Lamp or appliance does not work. 1. Make sure the lamp or appliance is plugged in.
2. Replace burned‑out bulbs.
3. Repair or replace a worn or damaged lamp or appliance cord.
4. Tighten any loose wire connections.
5. Clean dirty or oxidized wire ends.
6. Replace any faulty receptacle.

Receptacle does not hold plugs firmly. 1. Repair or replace worn or damaged plugs.
2. Replace the faulty receptacle.

Receptacle is warm to the touch, buzzes, or sparks when plugs 1. Move lamps or appliances to other circuits to prevent overloads.
are inserted or removed. 2. Tighten any loose wire connections.
3. Clean dirty or oxidized wire ends.
4. Replace the faulty receptacle.

RECEPTACLES 99
 Receptacle Wiring White neutral wire

A 120-volt duplex receptacle can be wired to the

electrical system in several ways. The most
common are shown on these pages.
Grounding screw

Brass screw
terminal
Extending a branch circuit or adding a new branch
to install new receptacles, lights, or switches requires Silver Black hot wire
a permit. The electrical inspector may require that screw
you install arc-fault protection on the entire circuit. terminal
Metal receptacle
Check with the electrical inspector before starting box
such projects. Grounding wires
Wiring configurations may vary slightly from
these photographs, depending on the kind of Grounding
screw
receptacles used, the type of cable, or the technique terminal
of the electrician who installed the wiring. To make
dependable repairs or replacements, use masking A single cable entering the box indicates end‑of‑run wiring.
tape and label each wire according to its location on The black hot wire is attached to a brass screw terminal, and
the white neutral wire is connected to a silver screw terminal.
the terminals of the existing receptacle.
If the box is metal, the grounding wire is pigtailed to the
Receptacles are wired as either end-of-run or grounding screws of the receptacle and the box. In a plastic
middle-of-run. These two basic configurations are box, the grounding wire is attached directly to the grounding
easily identified by counting the number of cables screw terminal of the receptacle.
entering the receptacle box. End-of-run wiring has
only one cable, indicating that the circuit ends.
White neutral wires
Middle-of-run wiring has two cables, indicating
that the circuit continues on to other receptacles,
switches, or fixtures.
A split-circuit receptacle is shown on the next
Grounding
page. Each half of a split-circuit receptacle is wired screw
to a separate circuit. This allows two appliances of
Black hot
high current to be plugged into the same receptacle wires
without tripping a breaker or blowing a fuse. This
wiring configuration is similar to a receptacle that
is controlled by a wall switch. Code requires a
switch-controlled receptacle in most rooms that do not Brass
screw
have a built-in light fixture operated by a wall switch. Silver screw
terminals
terminals
Split-circuit and switch-controlled receptacles are Grounding wires
connected to two hot wires, so use caution during
Grounding
repairs or replacements. Make sure the connecting screw
tab between the hot screw terminals is removed. terminal
Two-slot receptacles are common in older homes.
Two cables entering the box indicate middle‑of‑run wiring. Black
There is no grounding wire attached to the receptacle, hot wires are connected to brass screw terminals and white
but the metal box may be grounded with armored neutral wires to silver screw terminals. The grounding wire is
cable or metal conduit. pigtailed to the grounding screws of the receptacle and the box.

100 THE COMPLETE GUIDE TO WIRING

 A split‑circuit receptacle (technically
a multiwire branch circuit) is attached
White neutral wire to a black hot wire, a red hot wire,
a white neutral wire, and a bare
grounding wire. The wiring is similar to
a switch‑controlled receptacle.
The hot wires are attached to the brass
screw terminals, and the connecting
Grounding tab or fin between the brass terminals
screw is removed. The white wire is attached
to a silver screw terminal, and the
Silver screw Brass screw connecting tab on the neutral side
terminal terminal remains intact. The grounding wire
is pigtailed to the grounding screw
terminal of the receptacle and to the
Black hot grounding screw attached to the box.
wire
Note: A receptacle wired like this must
be fed by a double‑pole circuit breaker
Red hot wire (with each hot wire connecting to a
terminal on the breaker) or by two
single‑pole breakers connected with
Grounding wires a handle tie. This ensures that both
Grounding halves of the receptacle are always
screw shut off at the same time, to prevent
terminal accidents.

Single cable entering the box

indicates end‑of‑run wiring

A two‑slot receptacle is often found

in older homes. The black hot wires
Black hot wires are connected to the brass screw
terminals, and the white neutral
wires are pigtailed to a silver screw
terminal.Two‑slot receptacles may be
replaced with three‑slot types, but only
if a means of grounding exists at the
receptacle box. In some municipalities,
Silver screw
you may replace a two‑slot receptacle
terminal
with a GFCI receptacle as long as the
White
receptacle has a label that reads “No
neutral
equipment ground.”
wires

Brass screw
terminal

Two cables entering the box

indicates middle‑of‑run wiring

RECEPTACLES 101
 How to Install a New Receptacle

1 2

Position the new old‑work box on the wall and trace around it. Remove baseboard between the new and existing receptacle.
Consider the location of hidden utilities within the wall before Cut away the drywall about 1" below the baseboard with a
you cut. jigsaw, drywall saw, or utility knife.

3 4

Drill a 5⁄8" hole in the center of each stud along the opening Run the branch cable through the holes from the new location
between the two receptacles. A drill bit extender or a flexible to the existing receptacle. Staple the cable to the stud below
drill bit will allow you a better angle and make drilling the the box. Install a metal nail plate on the front edge of each
holes easier. stud that the cable routes through.

102 THE COMPLETE GUIDE TO WIRING

 New receptacle location

Old receptacle location

5 6
Turn off the power at the panel and test for power. Remove the Thread the new and old cables into an old work box large
old receptacle and its box, and pull the new branch cable up enough to contain the added wires and clamp the cables.
through the hole. Remove sheathing and insulation from both Fit the box into the old hole and attach it.
ends of the new cable.

7 8
Reconnect the old receptacle using pigtails to connect the Pull the cable through another old work box for the new
neutral, hot, and grounding wires from the new branch cable receptacle. Secure the cable and install the box. Connect the
and the old cable. new receptacle to the new branch cable. Insert the receptacle
into the box and attach the receptacle and cover plate
with screws. Patch the opening with drywall. Reattach the
baseboard to the studs.

RECEPTACLES 103
 GFCI Receptacles TOOLS & MATERIALS
Noncontact voltage tester Wire connectors
Screwdriver Masking tape
A ground-fault circuit-interrupter (GFCI) protects
against electrical shock caused by a faulty appliance
or a worn cord or plug. It senses small changes in
current flow and can shut off power in as little as 1⁄40 of
a second. GFCIs can be a circuit breaker and protect
the circuit from the panel. Often, however, they are Neutral wires
receptacles that protect one receptacle and may protect
other receptacles and light fixtures downstream.
GFCIs are now required in bathrooms, kitchens, Grounding
within 6 feet of all sinks, garages, crawl spaces, wires
basements, laundry rooms, and outdoor receptacle Hot wires
locations. Consult your local codes for any requirements
regarding the installation of GFCIs. Most GFCI Receptacle
receptacles use standard screw terminal connections, grounding
but some have wire leads and are attached with wire screw Box
grounding
connectors. Because the body of a GFCI receptacle screw
is larger than a standard receptacle, small, crowded
electrical boxes may need to be replaced with more A GFCI wired for single‑location protection (shown from
spacious boxes. the back) has hot and neutral pigtail wires connected only
to the screw terminals marked LINE. A GFCI connected
Because the GFCI is so sensitive, it is most for single‑location protection may be wired as either an
effective when wired to protect a single location. The end‑of‑run or middle‑of‑run configuration.
more receptacles any one GFCI protects, the more
susceptible it is to “nuisance tripping,” shutting off
power because of tiny, normal fluctuations in current
flow. GFCI receptacles installed in outdoor locations
must be rated for outdoor use and weather resistance
(WR) along with ground fault protection. Neutral wires

Modern GFCI Hot wires

receptacles have
tamper‑resistant
(TR) slots. Look Grounding
for a model that’s wires
Receptacle
rated “WR” grounding
(for weather screw Box
resistance) if grounding
you’ll be installing screw
it outdoors or in a
wet location. A GFCI wired for multiple‑location protection (shown from the
back) has one set of hot and neutral pigtail wires connected to
the LINE pair of screw terminals and the other set connected
to the LOAD pair of screw terminals. A GFCI receptacle
connected for multiple‑location protection may be wired only
as a middle‑of‑run configuration.

104 THE COMPLETE GUIDE TO WIRING

 How to Install a GFCI for Single‑Location Protection

1 2 3

Shut off power to the receptacle at the Remove the cover plate. Loosen Disconnect all wires from the receptacle
panel. Test for power with a noncontact mounting screws, and gently pull the terminals and remove the receptacle.
voltage tester. Be sure to check both receptacle from the box. Do not touch
halves of the receptacle. wires. Confirm power is off with the
voltage tester.

4 5 6

Pigtail all the white neutral wires together, Pigtail the black wires together, and If a grounding wire is available,
and connect the pigtail to the terminal connect them to the terminal marked connect it to the green grounding
marked WHITE LINE on the GFCI (see HOT LINE on the GFCI. screw terminal of the GFCI. Mount
photo on opposite page). the GFCI in the receptacle box, and
reattach the cover plate. Restore
power and test the GFCI according
to the manufacturer’s instructions.
If a grounding wire is not available,
label the receptacle cover plate:
NO EQUIPMENT GROUND.

RECEPTACLES 105
 How to Install a GFCI for Multiple‑Location Protection

1 2 3

Use a map of your house circuits to Turn off power to the correct circuit at Remove the cover plate from the
determine a location for your GFCI. the panel. Test all the receptacles in the receptacle that will be replaced with the
Indicate all receptacles that will be circuit with a noncontact voltage GFCI. Loosen the mounting screws and
protected by the GFCI installation. tester to make sure the power is off. gently pull the receptacle from its box.
Always check both halves of each Take care not to touch any bare wires.
duplex receptacle. Confirm the power is off with a non‑
contact voltage tester.

4 5
When you have found the hot feed wire,
turn off power at the panel. Identify
the feed wire by marking it with
masking tape.

Disconnect all black hot wires. Carefully separate the hot wires
and position them so that the bare ends do not touch anything.
Restore power to the circuit at the panel. Determine which
black wire is the feed wire by testing each black wire with the
voltage tester. The feed wire brings power to the receptacle
from the service panel.

USE CAUTION: This is a live wire test, during which the

power is turned on temporarily.

106 THE COMPLETE GUIDE TO WIRING

 6 7 8

Disconnect the white neutral wires from Disconnect the grounding wire from the Connect the white feed wire to the
the old receptacle. Identify the white grounding screw terminal of the old terminal marked WHITE LINE on the
feed wire and label it with masking receptacle. Remove the old receptacle. GFCI. Connect the black feed wire
tape. The white feed wire will be the to the terminal marked HOT LINE on
one that shares the same cable as the the GFCI.
black feed wire.

9 10 11

Connect the other white neutral wire to Connect the other black hot wire to Carefully tuck all wires into the
the terminal marked WHITE LOAD the terminal marked HOT LOAD receptacle box. Mount the GFCI in
on the GFCI. on the GFCI. Connect the grounding the box and attach the cover plate.
wire to the grounding screw terminal Turn on power to the circuit at the
of the GFCI. panel. Test the GFCI according to the
manufacturer’s instructions.

RECEPTACLES 107
 Testing Receptacles Auto‑ranging
multimeter

F or testing receptacles and other devices for power, grounding, and

polarity, neon circuit testers are inexpensive and easy to use. But they
are less sensitive than auto-ranging multimeters. In some cases, neon
testers won’t detect the presence of lower voltage in a circuit. This can
lead you to believe that a circuit is shut off when it is not—a dangerous
mistake. The small probes on a neon circuit tester also force you to get
too close to live terminals and wires. For a quick check and confirmation,
a neon circuit tester (or a plug-in tester) is adequate. But for the most
reliable readings, buy and learn to use a multimeter.
The best multimeters are auto-ranging models with a digital readout.
Unlike manual multimeters, auto-ranging models do not require you to
preset the voltage range to get an accurate reading. Unlike neon testers,
multimeters may be used for a host of additional diagnostic functions
such as testing fuses, measuring battery voltage, testing internal wiring in
appliances, and checking light fixtures to determine if they’re functional. Metal probes

TOOLS & MATERIALS

Multimeter Noncontact voltage tester Plug‑in tester Screwdriver

How to Use How to Test

a Plug‑In Tester Quickly for Power
Use a plug‑in tester
to test a three‑slot
receptacle. With
the power on, insert the
tester into the suspect
outlet. The face of the
tester has three colored
lights that will light up in
different combinations,
according to the outlet’s
problem. A reference
chart is provided with
the tester, and there
may be a chart on Use a noncontact voltage tester to verify that power is not
the tester itself. These flowing to a receptacle. Using either a no‑touch sensor or a
testers are useful, but probe‑style circuit tester, test the receptacle for current before
they do not test for all you remove the cover plate. Once the plate is removed, double‑
wiring errors. check at the terminals to make sure there is no current.

108 THE COMPLETE GUIDE TO WIRING

 How to Test a Receptacle with a Multimeter

1 2

Set the selector dial for alternating‑current voltage. Plug the Insert each probe into one of the receptacle slots. It does not
black probe lead into the common jack (labeled COM) on the make a difference which probe goes into which slot as long as
multimeter. Plug the red probe lead into the V‑labeled jack. they’re in the same receptacle. If power is present and flowing
normally, you will see a voltage reading on the readout screen.

OPTION: When a receptacle or switch is in the middle of a

circuit, it is difficult to tell which wires are carrying current.
If the multimeter reads 0 or gives a very low reading (less Use a multimeter to check. With power off, remove the
than 1 or 2 volts), power is not present in the receptacle and receptacle and separate the wires. Restore power. Touch
it is safe to remove the cover plate and work on the device one probe to the bare ground or the grounded metal box
(although it’s always a good idea to confirm your reading and touch the other probe to the end of each wire. The
by touching the probes directly to the screw terminals on wire that shows current on the meter is hot.
the receptacles).

RECEPTACLES 109
Preliminary Work

S ome very important parts of any electrical project

occur well before you ever make a box cutout or
strip a wire. In addition to the most elementary tasks
of figuring out what needs to happen and how it’s
done, there are required procedural steps you’ll need
to take as well as some basic household planning.
To form an overview of what you want to
accomplish and how to get it done, you’ll need to
begin by assessing the condition of your wiring system
as it exists. This involves a little investigative work and
a little math. You’ll find plenty of information on both
in this chapter.
Once you’ve made an evaluation of what you
have to work with, it’s time to start the planning in
earnest. Naturally the amount of planning required
depends largely on the scale of the project. If you are
wiring a room addition or an extensive remodel, the
wiring plan should be established and approved well
in advance of the start of the project. In fact, without
an approved wiring plan you will be unable to obtain
a valid building permit. Even for small-scale projects,
such as adding a new light circuit or a new receptacle,
you need a permit, and to get the permit you need a
plan. You typically do not need a permit for simple
one-for-one replacements of devices such as switches
and receptacles, but it still pays to plan. For example,
if you are replacing a light switch, you should plan
ahead and do the job during the daytime to take
advantage of the natural light.

In this chapter:
• Planning Your Project
• Draw a Diagram & Obtain a Permit
• Room-by-Room Wiring

PRELIMINARY WORK 111

 When wiring a remodeled kitchen, it is a good
idea to install circuits for an electric range or cooktop,
even if you do not have these electric appliances.
Installing these circuits now makes it easy to convert
from gas to electric appliances at a later date.
A large wiring project adds a considerable load
to your main electrical service. In about 25 percent
Planning Your Project of all homes, some type of service upgrade is needed
before new wiring can be installed. For example,
some homeowners will need to replace an older
60-amp electrical service with a new service rated
C areful planning of a wiring project ensures you
will have plenty of power for present and future
needs. Whether you are adding circuits in a room
for 100 amps or more. This is a job for a licensed
electrician but it is well worth the investment. In
other cases, the existing main service provides
addition, wiring a remodeled kitchen, or adding an
outdoor circuit, consider all possible ways the space adequate power, but the main circuit breaker panel is
might be used, and plan for enough electrical service too full to hold any new circuit breakers. In this case
to meet peak needs. it is necessary to install a circuit breaker subpanel
For example, when wiring a room addition, to provide room for hooking up added circuits.
remember that the way a room is used can change. Installing a subpanel is a job most homeowners can
In a room used as a spare bedroom, a single do themselves (see pages 189–191).
15-amp circuit provides plenty of power, but if you This chapter gives an easy five-step method for
ever choose to convert the same room to a family determining your electrical needs and planning
recreation space, you will need additional circuits. new circuits.

Five Steps for Planning a Wiring Project

1 2

Examine your main service panel (see page 114). The amp Learn about codes (see pages 115–121). The National
rating of the electrical service and the size of the circuit Electrical Code (NEC), and local electrical codes and building
breaker panel will help you determine if a service upgrade codes, provide guidelines for determining how much power
is needed. and how many circuits your home needs. Your local electrical
inspector can tell you which regulations apply to your job.

112 THE COMPLETE GUIDE TO WIRING

 3

4
Prepare for inspections (see pages 130–131). Remember Evaluate electrical loads (see pages 132–137). New circuits put
that your work must be reviewed by your local electrical an added load on your electrical service. Make sure that the total
inspector. When planning your wiring project, always follow load of the existing wiring and the planned new circuits does not
the inspector’s guidelines for quality workmanship. exceed the service capacity or the capacity of the panel.

5
Draw a wiring diagram and get a permit (see pages 132–133). This wiring plan will help you organize your work.

PRELIMINARY WORK 113

 Examine Your Main Service Panel
The first step in planning a new wiring project is to the main service helps you determine if you need a
look in your main circuit breaker panel and find the service upgrade.
size of the service by reading the amperage rating on Also look for open circuit breaker slots in the
the main circuit breaker. As you plan new circuits panel. The number of open slots will determine if you
and evaluate electrical loads, knowing the size of need to add a circuit breaker subpanel.

Older service panels use fuses instead of circuit breakers.

Have an electrician replace this type of panel with a circuit
breaker panel that provides enough power and enough
open breaker slots for the new circuits you are planning.

Main
circuit
breaker

Find the service size by opening the main service panel and
reading the amp rating printed on the main circuit breaker. This
method works when there is one main circuit breaker or fuse
block. Some houses have multiple services disconnects. In these
cases, contact an electrician to determine your service size. In
most cases, 100-amp service provides enough power to handle
the added loads of projects such as the ones shown in this book.
A service rated for 60 amps or less should be upgraded.

NOTE: In some homes the main circuit breaker is located in

a separate box.

Expandable

Not expandable

Look for open circuit breaker slots in the main circuit breaker panel or in a circuit breaker subpanel, if your home already has one.
You will need one open slot for each 120-volt circuit you plan to install and two slots for each 240-volt circuit. If your main circuit
breaker panel has no open breaker slots, install a subpanel (see pages 189–191) to provide room for connecting new circuits.

114 THE COMPLETE GUIDE TO WIRING

Learn About Codes
To ensure public safety, your community requires that will expect you to understand the local guidelines as
you get a permit to install new wiring and have the well as a few basic NEC requirements.
work reviewed by an inspector. Electrical inspectors The NEC is a set of standards that provides
use the National Electrical Code (NEC) as the primary minimum safety requirements for wiring installations.
authority for evaluating wiring, but they also follow the It is revised every three years. The national code
local building code and electrical code standards. requirements for the projects shown in this book
Most communities use a version of the NEC are explained on the following pages. For more
that is not the most current version. Also, many information, you can find copies of the current NEC,
communities make amendments to the NEC, and as well as a number of excellent handbooks based on
these amendments may affect your work. the NEC, at libraries, bookstores, and online. Many city
As you begin planning new circuits, call or building departments and state authorities publish
visit your local electrical inspector and discuss local code rules and updates online.
the project with him or her. The inspector can In addition to being the final authority of code
tell you which of the code requirements apply to requirements, inspectors are electrical professionals
your job and may give you a packet of information with years of experience. Although they have busy
summarizing these regulations. Later, when you schedules, most inspectors are happy to answer
apply to the inspector for a work permit, he or she questions and help you design well-planned circuits.

Basic Electrical Code Requirements

Switch-controlled light fixture

More than
24"
Dedicated appliance circuit

12 ft. maximum

Electrical code requirements for living areas: Living areas need at least one 15-amp or 20-amp basic lighting/receptacle circuit
for each 600 sq. ft. of living space and should have a dedicated circuit for each type of permanent appliance, such as an air
conditioner or a group of baseboard heaters. Receptacles on basic lighting/receptacle circuits should be spaced no more than
12 ft. apart. Many electricians and electrical inspectors recommend even closer spacing. Any wall more than 24" wide also
needs a receptacle. Every room should have a wall switch at the point of entry to control either a ceiling or wall-mounted light or
plug-in lamp. Kitchens and bathrooms must have a ceiling or wall-mounted light fixture.

PRELIMINARY WORK 115

 Selected NEC Standards & Tips

Measure the living areas of your home,

excluding unconditioned spaces. You will
need a minimum of one basic lighting/
receptacle circuit for every 600 sq. ft. Three-way switches
of living space. The total square footage
also helps you estimate heating and
cooling needs for new room additions.
Stairways must have one or more light fixtures that are capable of lighting all stair
treads and landings, including the top and bottom landings. The light fixture must
be controlled by three-way switches at the top and bottom landings.

5
⁄8" hole

1¼"

Nail
guard

Furring
strip

Cutaway
view

Cables must be protected against damage by nails and screws

Kitchen countertop and all bathroom receptacles must be by at least 1¼" of wood (top). When cables pass through
protected by a ground-fault circuit-interrupter (GFCI). Also, 2" × 2" furring strips (bottom), protect the cables with metal
all outdoor receptacles and receptacles in basements, crawl nail guards. Nail guards also may be used to protect cable that
spaces, and garages must be protected by a GFCI. cannot meet the 1¼" minimum of wood protection standard.

116 THE COMPLETE GUIDE TO WIRING

 Hallways at least 10 ft. long
need at least one receptacle.
All hallways should have a
switch-controlled light fixture.

Walk-in closets and other storage spaces should have at least

one light fixture that is controlled by a wall switch near the
entrance. Prevent fire hazards by positioning the light fixtures
so the outer globes are at least 12" away from all shelf areas.

NOTE: This suggestion is primarily for homeowner

convenience and is not required by most codes.

Metal brace

Cutaway view

A metal brace attached to framing members is required for Label new circuits on an index attached to the circuit breaker
ceiling fans and large light fixtures that are too heavy to panel door. List the rooms and appliances controlled by
be supported by an electrical box. All ceiling fans must be each circuit. Make sure the area around the panel is clean,
installed in a box that is fan-rated. well lighted, and accessible.

PRELIMINARY WORK 117

 Selected NEC Standards & Tips

Light fixtures (luminaires) must be approved for their location. Electrical service to the home must have disconnecting means
For example, in shower and tub areas, light fixtures must located in an accessible outdoor location, and it must be
be rated for damp locations or, if they are subject to shower labeled appropriately. This allows emergency responders to
spray, for wet locations. shut off the power before they enter the home.

Metal electrical boxes must be grounded with a machine GFCI receptacles can be installed on circuits that do not
screw or an approved grounding clip. Machine screws must have a ground wire. In this case, the receptacle face must be
be engaged with at least two threads into the box. Grounding labeled “No Equipment Ground.” The receptacle will provide
screws are sold for this purpose. Drywall and sheet metal GFCI protection but will not have a true ground connection.
screws are not acceptable for grounding. Most GFCI receptacles come with these sticker labels in
the package.

118 THE COMPLETE GUIDE TO WIRING

Selected NEC Standards & Tips

Service lugs

Service lugs in the main service panel must be protected by Transformers for low-voltage lighting systems must remain
approved barriers, sometimes called service barriers. This accessible. A transformer can be installed outdoors, indoors,
applies to any uninsulated, ungrounded conductor terminal or in a garage or outbuilding, depending on its rating. Consult
or busbar in the service disconnect. Barriers are inexpensive, the manufacturer’s instructions for additional installation
removable plastic covers. requirements.

Laundry rooms must have at least one 120-volt, 20-amp, GFCI-protected receptacle on a dedicated circuit, and it must be within
6 feet of any appliance it serves (such as a washing machine or a gas dryer). Electric dryers require a 30-amp (minimum),
120/240-volt, GFCI-protected receptacle on a dedicated four-conductor circuit (contains two hot wires, a neutral, and a ground).
Existing three-conductor receptacle circuits are allowed to remain in use, if permitted by local code.

PRELIMINARY WORK 119

 HIGHLIGHTS OF THE NATIONAL ELECTRICAL CODE
Panels • Connect only a single wire to a single screw
• Maintain a minimum 30" wide by 36" deep of clearance terminal. Use pigtails to join more than one wire to a
in front of the panel. screw terminal.

• Install a surge protective device when installing new

electrical service and when changing or upgrading Switches
electrical service. • Use a switch-controlled receptacle in rooms without a
built-in light fixture operated by a wall switch.
• Install an emergency disconnect device outside of the
house when installing new electrical service and when • Use switches with grounding screws with plastic
changing or upgrading electrical service. electrical boxes.

• Match the amperage rating of the circuit when • Locate all wall switches within easy reach of the room
replacing breakers or fuses. entrance and not behind the door.

• Use handle ties on all 240-volt breakers and on 120-volt • Install a separate receptacle for an electric dryer, as
breakers protecting multiwire branch circuits. applicable. This must be 30-amp (minimum),
240-volt, GFCI protected, and on a dedicated four-
• Close all unused panel openings.
conductor circuit.
• Label each fuse and breaker clearly on the panel.
• Install a neutral wire in switch boxes.
• Use black or red wires to supply power to switched devices.
Electrical Boxes
• Use boxes that are large enough to accommodate the
number of wires and devices in the box.
Receptacles
• Install receptacles on all walls at least 24" long.
• Install all junction boxes so they remain accessible.
• Install receptacles so a 6-foot cord can be plugged in
• Leave no gaps greater than 1⁄8" between wall finish from any point along a wall, or every 12 ft. along a wall.
materials and the front of electrical boxes.
• Include receptacles in any hallway that is 10 feet long
• Place receptacle boxes flush with combustible surfaces. or longer.
• Leave a minimum of 3" of usable cable or wire extending • Use three-slot, grounded receptacles for all 15- or
past the front of the electrical box. 20-amp, 120-volt branch circuits.
• Ground metal electrical boxes with a grounding pigtail. • Install GFCI-protected receptacles in bathrooms,
kitchens, garages, crawl spaces, basements, laundry
Wires & Cables rooms, and outdoors.
• Use wires that are large enough for the amperage rating • Include GFCI protection for dishwashers and
of the circuit (see Wire Size Chart, page 26). sump pumps.
• Drill holes at least 2" from the edges of joists. Do not • Install one 20-amp, 120-volt, GFCI-protected
attach cables to the bottom edge of joists. receptacle for each parking space in a garage.
• Do not run cables diagonally between framing members. • Install at least one 120-volt receptacle in each unfinished
basement area.
• Use nail plates to protect cable that is run through holes
drilled or cut into studs less than 1¼" from the front • Install a 120-volt receptacle within 25 feet from HVAC
edge of a stud. equipment such as furnaces, boilers, and condensers.
• Do not crimp cables sharply.
• Contain spliced wires or connections entirely in a
Light Fixtures
• Use mounting straps that are anchored to the electrical
covered plastic or metal electrical box.
boxes to mount ceiling fixtures.
• Use approved wire connectors to join wires.
• Keep non–IC-rated recessed light fixtures 3" from
• Use staples to fasten cables within 8" of an electrical box insulation and ½" from combustibles.
and every 54" along its run.
• Include at least one switch-operated lighting outlet in every
• Leave a minimum ¼" (maximum 1") of sheathing where habitable room, kitchen, bathroom, basement, hallway,
cables enter an electrical box. stairway, attached garage, and attic and crawlspace area
• Clamp cables and wires to electrical boxes with approved that is used for storage or that contains equipment that
clamps. No clamp is necessary for one-gang plastic requires service. This outlet may be a switched receptacle
boxes if cables are stapled within 8" of the box. in areas other than kitchens and bathrooms.

120 THE COMPLETE GUIDE TO WIRING

• Do not install dimmer switches on interior stair lights Laundry Rooms
unless a dimmer is installed on all switches controlling • Install at least one 20-amp, GFCI-protected
these lights.
receptacle on its own circuit, located within 6 feet of a
washing machine.
AFCI and GFCI Protection
• Install approved conduit for wiring in unfinished rooms.
• Extending a branch circuit or adding a new branch to
install new receptacles, lights, switches, or equipment • Install a separate receptacle for an electric dryer, as
requires a permit. The electrical inspector may require applicable. This must be 30-amp (minimum),
that you install arc-fault protection on the entire circuit 240-volt, GFCI protected, and on a dedicated
and may require that you install GFCI protection where four-conductor circuit.
currently required. Check with the electrical inspector
before starting such projects.
Living, Entertainment, Bedrooms
• Install at least one 15- or 20-amp lighting/receptacle
Kitchens/Dining Rooms circuit for each 600 sq. ft. of living space.
• Install at least two 20-amp small-appliance
receptacle circuits. • Install a dedicated circuit for each permanent
• Install dedicated 15-amp, 120-volt circuits for appliance, such as an air conditioner or group of electric
dishwashers and food disposals (required by many baseboard heaters.
local codes). The dishwasher circuit should be • Use electrical boxes listed and labeled to support
GFCI protected. ceiling fans in locations where ceiling fans are commonly
• Install GFCI protection for all countertop installed.
receptacles; and for receptacles within 6 feet from
• Space receptacles on walls in living and sleeping rooms
the sink. The 6 feet from the sink rule includes all
a maximum of 12 feet apart.
receptacles, such as a refrigerator receptacle, range
receptacle, unused receptacles under the sink, and • Check with your local electrical inspector about
receptacles along walls. requirements for installing smoke and carbon monoxide
• Position receptacles for appliances that will be installed alarms during remodeling.
within cabinets, such as microwaves or food disposals,
according to the manufacturer’s instructions. Outdoors
• Include receptacles at all countertops and work surfaces • Check for underground utilities before digging.
wider than 12".
• Use UF cable or other wiring approved for wet locations
• Space receptacles a maximum of 48" apart above for outdoor wiring.
countertops and closer together in areas where many
• Run cable and wires in approved conduit, as required by
appliances will be used.
local code.
• Locate receptacles on the wall above the countertop not
more than 20" above the countertop. • Install in-use rated weatherproof receptacle covers.
• Do not connect lights to the small-appliance • Bury cables and wires run in conduit at least 18" deep;
receptacle circuits. cable not in conduit must be buried at least 24" deep.
• Use weatherproof electrical boxes with
Bathrooms watertight covers.
• Install a 20-amp circuit only for bathroom receptacles, • Provide GFCI protection for all outdoor receptacles.
or install a 20-amp circuit that serves receptacles and
lighting in only one bathroom and no other rooms.
• Provide GFCI protection for all bathroom receptacles. Stairs/Hallways
• Use three-way switches at the top and bottom on
• Install a dedicated circuit for an exhaust fan with heater
stairways with six risers or more.
or other type of heating appliance, if required.
• Install at least one receptacle not more than 36" from • Include receptacles in any hallway that is 10 feet long
each sink. or longer.
• Ensure light fixtures in tub/shower areas are rated for • Position stairway lights so each step and landing
damp or wet locations, as required. is illuminated.

PRELIMINARY WORK 121

 Prepare for Inspections
Electrical inspectors who issue the work permit At the final inspection, inspectors check random
for your wiring project will also visit your home to boxes to make sure the wire connections are correct.
review the work. Make sure to allow time for these If they see good workmanship at the selected boxes,
inspections as you plan the project. For most projects, the inspection will be over quickly. However, if they
inspectors make two visits. spot a problem, inspectors may choose to inspect
The first inspection, called the rough-in, is done every connection.
after the cables are run between the boxes but before Inspectors have busy schedules, so it is a
the insulation, drywall, switches, and fixtures are good idea to arrange for an inspection several days
installed. The second inspection, called the final, is in advance. In addition to basic compliance with
done after the walls and ceilings are finished and all code, inspectors expect your work to meet their
electrical connections are made. own standards for quality. When you apply for a
When preparing for the rough-in inspection, make work permit, make sure you understand what the
sure the area is neat. Sweep up sawdust and clean up inspectors will look for during inspections.
any pieces of scrap wire or cable insulation. Before You cannot put new circuits into use legally until
inspecting the boxes and cables, inspectors will check an inspector approves them at the final inspection. If
to make sure all plumbing and other mechanical work you have planned carefully and done your work well,
is completed. Some electrical inspectors will ask to electrical inspections are routine visits that give you
see your building and plumbing permits. confidence in your own skills.

Inspectors may measure to see that

electrical boxes are mounted at
Cable consistent heights. Height may not
staple be dictated by code, but consistency
Cable is a sign of good workmanship.
8" maximum staple Measured from the center of the boxes,
receptacles in living areas typically
are located 12" above the finished
floor and switches at 48". For special
circumstances, inspectors allow you
to alter these measurements. For
4½ ft. example, you can install switches at 36"
above the floor in a child’s bedroom,
or set receptacles at 24" to make them
more convenient for someone using
48" Cable a wheelchair.
staple
Inspectors will check cables to see that
they are anchored by cable staples
driven within 8" of each box and every
4½ ft. thereafter when they run along
studs. When bending cables, form the
Smooth wire in a smooth curve. Do not crimp
curve cables sharply or install them diagonally
About 20" between framing members. Some
12" inspectors specify that cables running
between receptacle boxes should be
about 20" above the floor.

122 THE COMPLETE GUIDE TO WIRING

 What Inspectors Look For
¼" sheathing, minimum

6" to end of wire

½" wallboard
Finished wall surface

Electrical box faces should extend past the front of framing members so the boxes will be flush with finished walls (left).
Inspectors will check to see that all boxes are large enough for the wires they contain. Cables should be cut and stripped back
so that at least 3" of usable length extends past the front of the box and so that at least ¼" of sheathing reaches into the box
(right). Label all cables to show which circuits they serve: inspectors recognize this as a mark of careful work. The labels also
simplify the final hookups after the drywall is installed.

IS YOUR RECEPTACLE SPACING CORRECT?

6 ft. 3 ft. sliding door 3 ft. fixed door 2 ft. 4 ft.
6 ft.

1 ft.
2 ft. 6 ft.
6 ft. 4 ft.
1 ft.
3 ft. refrigerator

1 ft.
1 ft.
6 ft. Island 3 ft.
5 ft. 6 ft.

2 ft.
1 ft. 6 ft.
Illo 299
CG_Codes Example of receptacle spacing requirements in a typical
06-15-2009
room (above). Measure receptacle spacing distance along 4 ft.
the wall line. Install receptacles along partial height walls
and along balcony guards in lofts and similar areas.
Illo 302 (right).
Example of receptacle spacing in a typical kitchen
CG_Codes 2 ft. 2 ft. 2.5 ft. 1 ft. 4 ft.
06-15-2009

PRELIMINARY WORK 123

 What Inspectors Look For

All wiring splices must be made with approved connectors. Cable sheathing damage indicates the wiring inside (or its
Common types include push-in connectors (left), standard insulation) may be compromised. Damaged portions of cables
wire connectors or “wire nuts” (center), and grounding-type and other wiring must be replaced to ensure safety.
wire connectors for ground wires (right).

Open, unused knockouts on boxes should be covered with New switch installations should include a neutral conductor
knockout plugs to ensure that the box is fully enclosed. in the switch box. Most standard switches do not connect to
neutral wires, but some “smart switches” with wireless control
connect to a neutral because the switches need a small
amount of current to receive wireless signals.

124 THE COMPLETE GUIDE TO WIRING

What Inspectors Look For

Circuits must be properly rated for the area(s) or appliance(s) Closet light fixtures must be fully enclosed (over the bulb) and
they serve as well as for safe capacity. For example, a circuit at least 12 inches from storage areas when the fixtures are
for bathroom receptacles that is rated for less than 20 amps is surface-mounted. Recessed fixtures must be at least 6 inches
an easy red flag during an inspection. from storage areas. Surface-mounted fixtures must be on the
ceiling or on the wall above the door.

Smoke alarms are required in all bedrooms (sleeping rooms) Carbon monoxide (CO) alarms are required in homes with fuel-
and in areas adjoining sleeping rooms. In addition, each fired systems (such as a gas furnace, water heater, or stove)
floor of the home must have at least one alarm, including and in homes with attached garages. Alarms are required
basements and habitable attic areas. Smoke alarms must outside of each sleeping area and inside any bedroom
be interconnected so activation of one alarm triggers all containing a fuel-fired appliance (such as a gas fireplace).
others. Check with the local code authority for specific
installation details.

PRELIMINARY WORK 125

 Evaluate Electrical Loads
Before drawing a plan and applying for a work permit,
make sure your home’s electrical service provides
enough power to handle the added load of the new
circuits. In a safe wiring system, the current drawn
by fixtures and appliances never exceeds the main
service capacity.
To evaluate electrical loads, use the work sheet
on pages 130–131 or whatever evaluation method is
recommended by your electrical inspector. Include
the load for all existing wiring as well as that for
proposed new wiring when making your evaluation.
Most of the light fixtures and plug-in appliances
in your home are evaluated as part of general
allowances for basic lighting/receptacle circuits
and small-appliance circuits. However, appliances
that are permanently installed usually require
their own dedicated circuits. The electrical loads
for these appliances are added in separately when
evaluating wiring.
If your evaluation shows that the load exceeds the
main service capacity, you must have an electrician
upgrade the main service before you can install new
wiring. An electrical service upgrade is a worthwhile
investment that improves the value of your home
and provides plenty of power for present and future
wiring projects.

AMPERAGE
AMPS × VOLTS TOTAL CAPACITY SAFE CAPACITY

15 A × 120 V = 1,800 watts 1,440 watts

20 A × 120 V = 2,400 watts 1,920 watts

25 A × 120 V = 3,000 watts 2,400 watts

30 A × 120 V = 3,600 watts 2,880 watts

20 A × 240 V = 4,800 watts 3,840 watts

30 A × 240 V = 7,200 watts 5,760 watts

Amperage rating can be used to find the wattage of an appliance. Multiply the amperage by the voltage of the circuit.
For example, a 13-amp, 120-volt circular saw is rated for 1,560 watts.

126 THE COMPLETE GUIDE TO WIRING

Calculating Loads

Nameplate

Add 1,500 watts for each small-appliance circuit required by If the nameplate gives the rating in kilowatts, find the watts
the local electrical code. In most communities, three such by multiplying kilowatts times 1,000. If an appliance lists only
circuits are required—two in the kitchen and one for the amps, find watts by multiplying the amps times the voltage—
laundry—for a total of 4,500 watts. No further calculations are either 120 or 240 volts.
needed for appliances that plug into small-appliance or basic
lighting/receptacle circuits.

FIXED DEVICES
Do not connect one or more
fixed devices that in total exceed
50 percent of a multiple outlet
branch circuit’s amperage rating.
Fixed devices do not include
light fixtures. This means that
that all fixed devices (such as
a permanently wired disposal
or hot water circulating pump)
on a multiple outlet branch
circuit may not exceed 7.5 amps
(about 900 watts) on a 15-amp
multiple outlet branch circuit
and may not exceed 10 amps
(about 1,200 watts) on a 20-amp
multiple outlet branch circuit.

Air-conditioning and heating appliances

are not used at the same time, so
figure in only the larger of these two
numbers when evaluating your home’s
electrical load.

PRELIMINARY WORK 127

 Locating Wattage

Nameplate

Wattage rating
Nameplate

Lightbulb wattage ratings are printed Electric water heaters are permanent Food disposers are considered
on the base or top of the bulb. If a appliances that require their own permanent appliances and may require
light fixture has more than one bulb, dedicated 30-amp, 240-volt circuits. their own dedicated 15-amp, 120-volt
remember to add the wattages of all Most water heaters are rated between circuits. Most disposers are rated
the bulbs to find the total wattage of 3,500 and 4,500 watts. If the between 500 and 900 watts.
the fixture. nameplate lists several wattage ratings,
use the one labeled “Total Connected
Wattage” when figuring electrical loads.

Nameplate
Nameplate
Nameplate

Dishwashers installed permanently Electric ranges can be rated for as little Installed microwave ovens are regarded
under a countertop may need dedicated as 3,000 watts or as much as 12,000 as permanent appliances. Add in its
15-amp, 120-volt circuits. Dishwasher watts. They usually require dedicated wattage rating when calculating loads.
ratings are usually between 1,000 and 120/240-volt circuits. Find the exact The nameplate is found on the back of
1,500 watts. Portable dishwashers are wattage rating by reading the nameplate the cabinet or inside the front door. Most
regarded as part of small-appliance found inside the oven door or on the microwave ovens are rated between
circuits and are not added in when back of the unit. 500 and 1,200 watts. A permanently
figuring loads. installed microwave should be on a
dedicated 20-amp, 120-volt circuit.

128 THE COMPLETE GUIDE TO WIRING

 Nameplate

Nameplate
Nameplate

Freezers are appliances that may need Electric clothes dryers are permanent Forced-air furnaces and heat pump air
a dedicated 15- or 20-amp, 120-volt appliances that need dedicated 30-amp, handlers have electric fans and are
circuits. Freezer ratings are usually 120/240-volt circuits. The wattage considered permanent appliances.
between 240 and 480 watts. But rating is printed on the nameplate inside They require dedicated 15-amp,
combination refrigerator-freezers are the dryer door. Use 5,000 watts as a 120-volt circuits. Include the fan
plugged into small-appliance circuits minimum, regardless of the printed rating. wattage rating, printed on a nameplate
and do not need their own dedicated Washing machines and gas-heat clothes inside the control panel, when figuring
circuits. The nameplate for a freezer is dryers with electric tumbler motors do not wattage loads for heating. You should
found inside the door or on the back of need dedicated circuits. They plug into also include the wattage rating for heat
the unit, just below the door seal. the 20-amp small-appliance circuit in the pump backup heating coils.
laundry room.

Nameplate Nameplate

Nameplate

A central air conditioner requires a Window air conditioners may be Electric baseboard heaters that are
dedicated 240-volt circuit. Estimate its considered permanent appliances if permanently installed require a
wattage rating by adding the numbers they are connected to a dedicated dedicated circuit and must be figured
labeled RLA and FLA on the air circuit. Through-wall air conditioners are into the load calculations. Use the
conditioner’s metal plate. Multiply the considered permanent appliances. The maximum wattage rating printed
RLA+FLA by 240. wattage rating, which can range from inside the cover. In general, 240-volt
500 to 2,000 watts, is found on the baseboard-type heaters are rated for
nameplate located inside the front grill. 180 to 250 watts for each linear foot.
Include permanently installed through-
wall air conditioners and window air
conditioners that are connected to a
dedicated circuit in your evaluation.

PRELIMINARY WORK 129

 How to Estimate Electrical Loads—with sample numbers

STEP DESCRIPTION QTY UNITS QTY UNITS LOAD (watts)

1. General lighting and receptacle circuits. Multiply
conditioned living area square footage by 3 watts
watts/
per square foot. Include new and existing areas. 1,500 sq. ft. 3 4,500
Do not include garage and porches. Include sq. ft.
parts of the basement that can be finished.

2. Kitchen and laundry circuits. At least 3 circuits

are required; 2 small-appliance circuits for
the kitchen, dining, and breakfast areas, and
1 laundry circuit. Multiply the number of circuits watts/
3 circuits 1,500 4,500
by 1,500 watts per circuit. The refrigerator is circuit
included in the small-appliance circuits, not in
the fixed appliance circuits. You may add an
additional circuit for the refrigerator, if you wish.

3. Fixed appliance circuits. Add the wattage ratings

on the appliance labels. These appliances are
often on a dedicated circuit. Examples are
listed below.

Range 1 appliance 12,300 watts 12,300

Surface cooking unit 0 appliance watts 0
Microwave oven 0 appliance watts 0
Wall oven 0 appliance watts 0
Disposer 1 appliance 800 watts 800
Built‐in dishwasher 1 appliance 1,200 watts 1,200
Electric clothes dryer 1 appliance 5,000 watts 5,000
Freezer 1 appliance 550 watts 550
Heat pump air handler 0 appliance watts 0
Furnace 0 appliance watts 0
Electric water heater 0 appliance watts 0
Others (e.g., sump pump, well pump,
pool pump)
0 appliance watts 0
Total fixed appliances 19,850
4. Add loads from steps 1, 2, and 3. 28,850
5. Subtract 10,000 watts from Step 4. (10,000)
6. Adjusted load 18,850
7. Calculated load. Multiply the adjusted load
(Step 6) by .40. This adjusts for all appliances 7,540
not operating at the same time.

130 THE COMPLETE GUIDE TO WIRING

STEP DESCRIPTION QTY UNITS QTY UNITS LOAD (watts)
8. Cooling loads. Include all heat pump or air
conditioning condensers. Include all window air
conditioners and through‐wall air conditioners
on dedicated circuits. Do not include window air
conditioners connected to general lighting and
receptacle circuits.

Condenser 1 1 condenser 3,500 watts 3,500

Condenser 2 0 condenser 0 watts 0
Window and through‐wall air conditioners 1 ac 1,100 watts 1,100
Total cooling loads 4,600
9. Heating loads. Examples are listed below. This is
a simplified procedure that will overestimate the
heating loads.

Heat pump condenser 1 0 condenser watts 0

Heat pump condenser 2 0 condenser watts 0
Heat pump strip 1 0 heat strips watts 0
Heat pump strip 2 0 heat strips watts 0
Electric furnace/boiler 1 appliance 1,200 watts 1,200
Electric baseboard heaters 4 heaters 1,350 watts 5,400
Total heating loads 6,600
10. Enter the larger number from Steps 8 and 9. 6,600
11. Add 10,000 watts to the calculated load from
Step 7.
17,540
12. Add Steps 10 and 11. 24,140
13. Divide Step 12 by 240. This is your estimated
service current load in amps.
101
14. Enter your current service amperage. 150
15. Compare the numbers in Steps 13 and 14. If
Step 13 is larger, you may need to upgrade
your electric service. If Step 14 is larger, you are
probably okay with your existing service.

NOTICE: This is a service load calculation for the entire house. This is a simplified procedure that will usually overestimate the
current load. Calculation of the feeder load for a subpanel is different. Contact your local electrical inspector or a licensed
electrician for guidance about more precise load calculations.

PRELIMINARY WORK 131

 Draw a Diagram & Obtain a Permit
Drawing a wiring diagram is the last step in planning a basic understanding of the electrical code and
a circuit installation. A detailed wiring diagram helps fundamental wiring skills. Some inspectors ask these
you get a permit, makes it easy to create a list of questions informally, while others give a short written
materials, and serves as a guide for laying out circuits test. Inspectors may allow you to do some, but not all,
and installing cables and fixtures. Use the circuit of the work. For example, they may ask that all final
maps on pages 148–165 as a guide for planning wiring circuit connections at the circuit breaker panel be
configurations and cable runs. Bring the diagram and made by a licensed electrician, while allowing you to
materials list when you visit electrical inspectors to do all other work.
apply for a permit. A few communities allow you to install wiring
Never install new wiring without following your only when supervised by an electrician. This means
community’s permit and inspection procedure. A you can still install your own wiring but must hire
permit is not expensive, and it ensures that your work an electrician to apply for the work permit and to
will be reviewed by a qualified inspector. If you install check your work before inspectors review it. The
new wiring without the proper permit, an accident or electrician is held responsible for the quality of
fire traced to faulty wiring could cause your insurance the job.
company to discontinue your policy and can hurt the Remember that it is the inspectors’ responsibility
resale value of your home. to help you do a safe and professional job. Feel free to
When electrical inspectors look over your wiring call them with questions about wiring techniques
diagram, they will ask questions to see if you have or materials.

A detailed wiring diagram and a list of materials is required before electrical inspectors will issue a work permit. If blueprints
exist for the space you are remodeling, start your electrical diagram by tracing the wall outlines from the blueprint. Use standard
electrical symbols (next page) to clearly show all the receptacles, switches, light fixtures, and permanent appliances. Make a
copy of the symbol key and attach it to the wiring diagram for the inspector's convenience. Show each cable run, and label its
wire size and circuit amperage.

132 THE COMPLETE GUIDE TO WIRING

 How to Draw a Wiring Plan

1 2

Draw a scaled diagram of the space you will be wiring, Mark the location of all switches, receptacles, light fixtures,
showing walls, doors, windows, plumbing pipes and fixtures, and permanent appliances, using the electrical symbols
and heating and cooling ducts. Find the floor space by shown below. Where you locate these devices along the cable
multiplying room length by width, and indicate this on run determines how they are wired. Use the circuit maps on
the diagram. pages 148–165 as a guide for drawing wiring diagrams.

3 4

Draw in cable runs between devices. Indicate cable size and Identify the wattages for permanent appliances and the type
type and the amperage of the circuits. Use a different-colored and size of each electrical box. On another sheet of paper,
pencil for each circuit. make a detailed list of all materials you will use.

ELECTRICAL SYMBOL KEY (COPY THIS KEY AND ATTACH IT TO YOUR WIRING PLAN)
240-volt Switched Junction box Ceiling fan
receptacle receptacle
Electric door
Isolated ground Weatherproof Ceiling opener
receptacle receptacle pull switch
Low-voltage
Duplex Surface-mounted transformer
receptacle Thermostat light fixture
Television
240-volt Pilot-light Recessed jack
dryer receptacle switch light fixture
Telephone
Singleplex Single-pole Fluorescent outlet
receptacle switch light fixture
Smoke
Fourplex Timer Wall-mounted dectector
receptacle switch light fixture
Vent fan
GFCI duplex Three-way Weatherproof
receptacle switch light fixture

PRELIMINARY WORK 133

 Requirements vary considerably from room to room.
A remodeled bedroom may need only a few added
receptacles, some new light fixtures, and a ceiling fan,
while a major kitchen renovation will likely require
several new circuits if not a complete overhaul of the
room’s wiring.
One of the nice things about electrical systems

Room-by-Room Wiring is that their circuit layout makes them relatively

compartmentalized. This means you can easily
update one room without making major changes
elsewhere, provided your service panel has enough

M ost major home projects involve expansion or capacity for any added circuits. And it makes
upgrading of existing wiring. For example, if you good sense to bring the entire room up to current
are remodeling a room of your house, and the plan standards, whether it’s required or not. Updating a
calls for structural or significant cosmetic changes, it’s room’s wiring and devices not only adds convenience,
probably also an ideal time to bring the wiring up to it also enhances safety. If you remodel your laundry
current standards. And when you pull a permit for the room, for instance, you now must provide GFCI
project, an electrical update will likely be required. protection for all of the receptacles—an important
Updating the wiring for a remodeled space often safety improvement for this often-wet area. And most
includes adding new devices and fixtures (or replacing areas of the house now must have AFCI protection.
old ones) and, in many cases, adding new circuits.

Electrical code requirements cover all aspects of bathroom wiring, including receptacles, lighting, exhaust fans, and heaters.
Most bathrooms need only one or two circuits, but those with jetted tubs or special heating systems will need more. Current
requirements ensure that bathrooms have plenty of power for hair dryers, curling irons, and any other plug-in devices.

134 THE COMPLETE GUIDE TO WIRING

Kitchens
An updated kitchen with the usual suite of electric Placement of countertop receptacles follows the
appliances will often have at least six individual so-called “2-foot, 4-foot” rule: In short, this means
circuits, but many kitchens have eight or more, that receptacles serving countertop areas are spaced
depending on their size and the number of large no more than 4 feet apart, and that no countertop
appliances they have. area (measured along the wall) is more than 2 feet
The most important things to watch out for from a receptacle. Islands and peninsulas also
in a kitchen wiring plan are GFCI protection and need receptacles: one for the first 9 square feet—or
receptacle placement. All receptacles serving fraction thereof—of countertop area, plus one for
countertop areas must be GFCI protected. In every additional 18 square feet or fraction thereof.
addition, any receptacle within 6 feet of a sink There are some exceptions and specific dimension
(measured from the sink’s top inside edge) must have requirements for applying the 2-foot, 4-foot rule, so
GFCI protection. This includes 240-volt receptacles check with the local code authority for details.
for electric ranges and other large plug-in appliances.
Circuits serving dishwashers also must be GFCI-
protected, and all 15- and 20-amp circuits in the
kitchen also must be AFCI-protected.

PRELIMINARY WORK 135

 SINK
DISHWASHER
RANGE

VENT HOOD

KITCHEN/DINING
MICROWAVE

ENTRY

Typical kitchen circuits include

■ Circuits #1 & #2: Small-Appliance Circuits ■ Circuit #3: Lighting

The NEC requires at least two 120-volt, 20-amp circuits One or more 120-volt,15-amp circuit for
feeding receptacles in countertop areas and all wall all kitchen lighting, including overhead
(and floor) receptacles in the kitchen and adjacent pantry (ambient) lighting, task lighting (such
and dining areas. These are commonly called the “small- as undercabinet lights), and accent
appliance” circuits because most of the receptacles feed lighting (pendant fixtures, lighting in
plug-in countertop appliances. Lighting and fixed appliances or above cabinets, etc.). By code, the
may not connect to these circuits. However, receptacles for a room must have at least one light fixture
plug-in clock or ignition on a gas stove may use these circuits. controlled by a wall switch. For large
If the dining and/or pantry areas are large and contain a lot kitchens, it’s a good idea to control
of wall receptacles, it’s a good idea to include a separate general lighting in multiple locations
20-amp circuit for those receptacles. with three-way and four-way switches.
Note: Kitchen lighting can be on
a general lighting circuit serving
other rooms.

136 THE COMPLETE GUIDE TO WIRING

 ■ ■ Circuits #6 & #7: Dishwasher &
Garbage Disposer
The NEC permits supplying a dishwasher
CIRCUITS
and garbage disposer on a single circuit,
1 but the combined wattage rating of both
appliances must not exceed the safe
2
capacity of the circuit. However, many
3 local codes require separate circuits for
4 these fixed appliances.
A dishwasher typically is fed by a
REFRIGERATOR
5 120-volt, 15- or 20-amp circuit, and
6 it must be GFCI protected. A disposer
circuit may be 15-amp or 20-amp, but
7 20-amp is generally recommended,
8 especially when the circuit also feeds
the dishwasher. Disposers are fed by
9 a receptacle installed in the sink base
cabinet, or they can be hardwired
with liquid-tight flexible conduit. They
are typically controlled by a switch
installed on the wall near the sink. If a
disposer receptacle is located inside a
N/DINING cabinet with a door, it does not need
GFCI protection unless it is a duplex
receptacle that is split wired so that one
half of the receptacle is switch controlled
and one half serves the dishwasher; in
this case, GFCI protection is required for
the dishwasher half.

■ Circuit #8: Electric Range,

DINING AREA Cooktop, or Oven
An electric range, oven, or cooktop
requires a dedicated 120/240-volt
circuit with an insulated neutral (see
page 193). For a full-size range, it is
best to install a 50-amp circuit, using
6-AWG copper wire. Freestanding
ranges typically plug into a wall or floor
receptacle, which must be four-slot
(separate neutral and ground wires).
Cooktops and built-in ovens typically
ENTRY are hardwired and may need a 30-, 40-,
or 50-amp circuit, depending on the
appliance wattage and the local code
requirements.

■ Circuit #4: Refrigerator ■ Circuit #9: Range Hood

Refrigerators are permitted by the NEC to plug into a receptacle on one of the small- Range hoods, or kitchen exhaust fans,
appliance circuits (Circuits #1 & #2), but if you’re remodeling the kitchen, it makes vary widely in size and wattage, so it’s
sense to include a dedicated 120-volt, 15- or 20-amp circuit for the refrigerator important to consult the manufacturer’s
(this is required in some areas). If the fridge receptacle is within 6 feet of the sink, recommendations for circuit capacity.
it must be GFCI protected. For plug-in fans, the NEC requires
a dedicated 120-volt circuit; local
■ Circuit # 5: Microwave code may or may not have the same
A portable plug-in microwave can be served by a countertop receptacle (there may requirement for hardwired fans. When
be local restrictions on wattage), but as with the fridge, it’s a good practice to include a dedicated circuit is not required, an
a dedicated 20-amp circuit for the microwave. Full-size microwaves draw 1,000 watts exhaust fan may be served by a kitchen
or more, which can strain a circuit’s capacity when other high-wattage appliances, lighting circuit, provided the circuit
such as toaster ovens or hot-water kettles, are running at the same time. capacity is not exceeded.

PRELIMINARY WORK 137

 Bathrooms
Bathrooms are the second most complex rooms to The second approach makes more sense for
wire (next to kitchens, of course), but they’re much everything else, and it’s better suited for bathrooms
simpler than kitchens. As a bare minimum, the with potentially high demand. For example, in a busy
NEC requires a 120-volt, 20-amp, GFCI-protected bathroom for growing children, there may be multiple
receptacle within 3 feet of each sink as well as a light high-wattage appliances (hair dryers, curling irons,
controlled by a wall switch near the entrance. If the heaters, etc.) running at the same time; that’s a lot
bathroom does not have a window that opens, it of power draw for a single circuit. Separating the
must have an exhaust fan with a capacity of at least receptacles from the other loads in the room leaves
50 cfm (cubic feet per minute). more capacity for the receptacles.
Meeting just these minimum requirements may Finally, there are some special rules for tub and
be suitable for a small powder room or half bath, but shower areas:
not anything bigger. A typical family bathroom may
have two or more circuits, multiple receptacles, several • A light fixture directly above a tub or shower must
lights, a large vent fan, and possibly a heater. A luxury be rated for wet locations if it will be subject to
master bath may have all of that plus towel heaters, shower spray; otherwise, it must be rated for damp
additional vent fans, a dedicated circuit for a whirlpool locations.
tub or a 240-volt circuit feeding a spa heater.
There are some special rules governing what you • The bathing zone—defined as the shower or tub
can put on a bathroom circuit, resulting in two basic area and 3 feet out from and 8 feet above the
approaches to the wiring plan: shower threshold or tub rim—can not have a
paddle fan, hanging lights, track lights, or cord-
1. A single 20-amp circuit feeds everything in a single connected fixtures.
bathroom, including receptacle(s), light(s), and
exhaust fan. This circuit may not be used for any A typical family bathroom might have the
other room. following circuits:

2. One or more 20-amp circuits feeds the receptacles ■ Circuit #1: Receptacles
in one or more bathrooms, but it must be used 120-volt, 20-amp circuit with a GFCI breaker or at least one
GFCI receptacle (wired for multiple-location protection if there
only for bathroom receptacles. In addition, a 15- are additional receptacles; see page 106).
amp or 20-amp lighting circuit feeds lights and
exhaust fans in one or more bathrooms or lighting ■ Circuit #2: Lighting and Ventilation
and/or receptacles in other rooms. 120-volt, 15- or 20-amp circuit for all lighting and a standard
exhaust fan. If the vent fan includes a heater, it may need its
own circuit, but it will surely need to be 20 amp.
The first approach makes sense if you’re wiring a
single bathroom with relatively simple needs, as it can ■ Circuit #3: Heating
be fed with a single home run from the service panel. 120-volt, 20-amp circuit for a small in-wall heater or an
However, if there are any heaters involved—such as exhaust fan with a heater. For a larger heating unit, a 240-volt
an exhaust fan with heat, an in-wall heater, or even a circuit may be required.
heater-type light fixture—additional circuits may be
required.

138 THE COMPLETE GUIDE TO WIRING

 CIRCUITS
1
2
3

SHOWER

IN-WALL
HEATER

PRELIMINARY WORK 139

 Living & Dining Rooms
Living areas—including family rooms, TV rooms, rec • Braced, ceiling-fan-rated box and separate switch
rooms, living rooms, and dining rooms—generally control for a ceiling fan
need lighting and receptacles, and these may or
may not be on the same circuit. Like all rooms in • Dedicated circuits for window air conditioners or
the house, each room in the living area must have a baseboard heaters
switch-controlled light or a switched receptacle ( for
plugging in a lamp that’s controlled by a wall switch • Receptacles closely flanking each window,
at the room’s entrance). Receptacles follow the “6-foot, fireplace, and built-in features
12-foot” rule: Receptacles spaced no more than 12 feet
apart so that no wall space is more than 6 feet from a • Recessed receptacle and data cable boxes for wall-
receptacle. Any wall space 2 feet or longer must have mount TVs
a receptacle.
In addition to these basic standards, there are • Floor receptacles for furniture groupings in room
plenty of easy upgrades that will help make rooms centers
more functional and convenient:
• Lighting outlets for built-in cabinetry
• Full lighting control at all room entrances, with
three-way or four-way switch configurations All circuits in living areas must be AFCI-protected.
Dining rooms treated as living areas must be separate
• Dimmer control for most or all fixed lighting from kitchen areas. Dining areas adjoining kitchens
have special receptacle requirements (see page 136).

CIRCUITS
1 2

WINDOW WINDOW

FIREPLACE

ENTRY

LIGHT AND/OR
CEILING FAN

ENTRY

140 THE COMPLETE GUIDE TO WIRING

 CIRCUITS
1
2

BED

WINDOW

CLOSET LIGHT AND/OR

CELING FAN

Bedrooms
Bedrooms don’t need much to meet code requirements • Add switched lighting at either side of the bed, if
and are typically supplied by one or two circuits. you have established the bed location. Bedside
But as with living and dining areas, bedrooms can switches can control a wall-mounted reading
benefit greatly from additional receptacles and a light on each side of the bed as well as control
thoughtful lighting and switch layout. The minimum the room’s overhead lighting and ceiling fan (as
requirements for bedrooms include a switch- applicable).
controlled overhead light or a switched receptacle,
and standard receptacles following the 6-foot, 12-foot • Install a braced, ceiling-fan-rated box at the room’s
rule. All bedroom circuits must be AFCI-protected center for the overhead light and an optional
and must include a smoke alarm (see page 224). ceiling fan. Include separate switch control for a
Adding more receptacles and switches can make fan.
a bedroom not only more user friendly, but it will
also be more versatile, allowing for arranging (and • Provide switch-controlled lighting in each closet.
rearranging) furniture any way you like. Consider the Lighting is not required in reach-in closets, but it
following upgrades in a bedroom plan: greatly improves usability. The best place for lights
is the wall above the door; this keeps fixtures well
• Include a receptacle about 2 feet from each wall away from storage areas (a code requirement;
corner, on both adjacent walls. This provides a see page 125), and it prevents shadows beneath
convenient place to plug in lamps, electronics, or shelving.
appliances regardless of the furniture arrangement.

PRELIMINARY WORK 141

 Hallways, Stairways & Foyers
Hallways, stairs, foyers, and mudrooms typically are
served by lighting and receptacle circuits (and often
by a single circuit), in addition to service for smoke
alarms and carbon monoxide alarms (see page 224).
Most code requirements are based on the size and/
or layout of the space. As a simple upgrade to code
minimums, you can always include more receptacles
or switches for added convenience and, in the case of
lighting, improved safety.
Hallways have one or more entrances, but all have
at least two ends, and all must have adequate lighting
controlled by one or more wall switches. A hallway
with two entrances should have a three-way switch at
each end. Those with a single entrance need a switch
at the entrance. It’s easy to add a switch based on
convenience. For example, if there are two bedrooms
at one end of a hallway, a switch on the wall between
the bedroom doors provides convenient control for
someone exiting either room. If the hallway is at least
10 feet long, it must have at least one receptacle, but it
can certainly have more.
All stairways need lighting that illuminates all
landings and stair treads (the horizontal part of a
step). If the staircase has at least six risers (the vertical
part of a step), the lighting must be controlled by
a three-way switch at the top and bottom of the
staircase. Receptacles are not required on stairways—
this is not a good place to leave plug-in appliances—
but it adds convenience to include a receptacle on SIDE ENTRY
a wall area near the top and bottom of the stairs, for
plugging in a vacuum cleaner.
Foyers and entryways that are larger than
60 square feet must have a receptacle on any
wall that is at least 3 feet long. The door and any
windows reaching to the floor do not count for this
requirement. For convenience, safety, and aesthetics,
most entryways have an overhead light fixture
illuminating the entire area.
Mudrooms are entry areas that may be considered
foyers, but if they are at least 7 x 10 feet (the
minimum size for habitable space), they may be
considered living areas, so it’s important to check
with the local authority for specific requirements.

142 THE COMPLETE GUIDE TO WIRING

MAIN ENTRY

CIRCUITS
1
2

PRELIMINARY WORK 143

 Laundry Room
Laundry rooms require at least one dedicated 120- work space, such as a counter area for ironing or
volt, 20-amp receptacle circuit plus service from a folding clothes, it’s a good idea to include one or more
separate lighting circuit. The lighting circuit may additional receptacles. All receptacles on the 20-amp
serve other rooms; the receptacle circuit may not. circuit must be GFCI- and AFCI-protected.
Only one 20-amp receptacle is required, and it must If the laundry room contains an electric dryer,
be located within 6 feet of the washing machine. A it needs a 30-amp (minimum), GFCI-protected
gas dryer can also use this receptacle or any others receptacle fed by a four-conductor branch circuit.
on the same circuit. If the room has any storage or

CIRCUITS
1
2
3
DRYER WASHER

DOOR

144 THE COMPLETE GUIDE TO WIRING

 CIRCUITS
WORK 1
BENCH
2

VEHICLE BAY VEHICLE BAY

HOUSE
DOOR

OVERHEAD DOOR

Garages and Basements

NEC requirements for garages apply to attached There are several easy upgrades to the code
garages and detached garages with electrical power. minimum that will make a garage or unfinished
In addition to lighting, a garage needs at least one basement safer and more convenient:
20-amp receptacle on a dedicated circuit. This
receptacle requirement overlaps with the requirement • Additional receptacles for work areas: These
for vehicle bays: Each bay must have one 20-amp should be 20-amp and located at a convenient
receptacle located not more than 51/2 feet above the height for a work bench.
floor. Therefore, a single-car garage needs at least one
20-amp receptacle, a two-car garage needs at least • A ceiling-mounted, GFCI-protected receptacle for
two; a three-car garage needs three, and so on. All each garage door opener.
receptacles in the garage must be GFCI protected.
Unfinished basements have similar minimum • Ample overhead lighting controlled by a switch at
requirements to garages: switched lighting and at each entrance (not counting any vehicle door).
least one receptacle in each unfinished area. Lighting
must illuminate any serviceable equipment, such as a • Task lighting for work areas; this could be on a
furnace or water heater. separate switch or controlled by the main switch
Finished basements are considered living space at the entrance(s).
and thus are subject to all of the rules applied to living
space elsewhere in the house, with one important
difference: All receptacles in the basement must be Note: The garage wall that is shared with the house
GFCI protected, whether the basement is finished is an important fire barrier. Never install electrical
or unfinished. boxes on the interior and garage sides of the wall so
that the boxes are back to back. Instead, make sure
they are in separate stud bays, and offset them by at
least 24 inches to maintain the fire barrier.

PRELIMINARY WORK 145

 Crawlspaces & Attics
Circuit requirements for crawlspaces and unfinished Electrical service for HVAC equipment is specific
attics vary by local code and whether or not the space to the equipment type and model; local code and
houses serviceable equipment, such as a furnace or the equipment manufacturer will determine what
other HVAC appliances. These spaces also tend to is required. As an example, a standard forced-air
be used for long-term storage, especially in homes gas furnace needs a dedicated 15- or 20-amp circuit
without basements. All of this supports the need with an approved means of disconnect. Usually
for adequate and convenient lighting in these this includes a switch on or near the furnace so the
unfinished spaces. furnace power can be easily shut off during repairs.
If serviceable equipment is present, there must In some cases, the circuit’s breaker can serve as
be lighting for all equipment requiring service, and the disconnect.
the lighting circuit must be GFCI protected in a If a crawlspace or attic does not house serviceable
crawlspace. The lighting must be controlled by a equipment, it’s still a good idea to include lighting
switch near the entrance. In addition, there must be for all usable or accessible portions of the space. A
a 15- or 20-amp receptacle located on the same level general lighting circuit with a switch at the entrance
and within 25 feet of the equipment (this also must be to the space will suffice.
GFCI protected in a crawlspace). The receptacle may
not be connected to the load side (downstream) of the
required branch circuit disconnect for the equipment.
CIRCUITS
1 2 3

FURNACE

ENTRANCE

146 THE COMPLETE GUIDE TO WIRING

 CIRCUITS
DECK/PATIO
1
2

REAR
ENTRY

AC
CONDENSER
GARAGE

HOUSE

OVERHEAD
DOOR

FRONT
ENTRY

Outdoors
The minimum requirements for outdoor wiring are In addition to the minimum requirements,
surprisingly simple. Homes need one receptacle at consider a few upgrades for improved safety or
the front of the house and one at the back. Decks, convenience:
balconies, and porches within 4 inches of the house
also need a receptacle. • Receptacle in a convenient location for plugging in
For lighting, each entry door at ground level needs a low-voltage lighting transformer
a light (excluding garage doors for vehicles), as does a
stairway landing that provides entrance to the house. • Switch-controlled receptacle(s) for holiday lights
If there is outdoor air-conditioning equipment,
there must be a 15- or 20-amp receptacle within 25 • Extra wall receptacles and an outlet for a ceiling
feet of the equipment and on the same level as the fan for a covered porch or patio (areas that tend to
equipment. be used as indoor/outdoor spaces)
All outdoor receptacles must be GFCI protected.
The required front and rear receptacles may be no • Lighting above or at the sides of vehicle doors
higher than 61/2 feet above grade, and receptacles
on decks, balconies, or porches may be no more
than 61/2 feet above the walking surface. Outdoor Note: Outdoor light fixtures and receptacles must
receptacles and lighting can be served by circuits be rated outdoor/weather-resistant (WR) type,
serving other areas, such as interior lighting and and receptacles must have an approved cover
receptacle circuits or garage circuits not serving (see page 198).
vehicle bays.

PRELIMINARY WORK 147

 To light To fan

THREE-WIRE CABLE
(NEUTRAL NOT USED)

TWO-WIRE CABLE
TWO-WIRE CABLE
Circuit Maps

T he circuit maps on the following pages show

the most common wiring variations for typical
electrical devices. Most new wiring you install will
match one or more of the maps shown. Find the maps
that match your situation and use them to plan your
circuit layouts.
The 120‑volt circuits shown on the following
pages are wired for 15 amps using 14‑gauge wire and
receptacles rated at 15 amps. If you are installing a
20‑amp circuit, substitute 12‑gauge wires and use
receptacles rated for 15 or 20 amps.
In configurations where a white wire serves as a
hot wire instead of a neutral, both ends of the wire are
coded with black tape to identify it as hot. In addition,
each of the circuit maps shows a box grounding
screw. This grounding screw is required in all metal
boxes, but plastic electrical boxes do not need to
be grounded.
You should remember two recent code
requirements when wiring switches. (1) Provide a
neutral wire at every switch box. This may require
using 3‑wire cable or two 2‑wire cables where you
may have used one 2‑wire cable in the past. (2) Use a
black or red wire to supply power from a 3‑way or a
4‑way switch to a light or switched receptacle.

NOTE: For clarity, all grounding conductors in the

circuit maps are colored green. In practice, the
grounding wires inside sheathed cables usually are
bare copper.

In this chapter:
• Common Household Circuits

CIRCUIT MAPS 149

 Common Household Circuits
1. 120‑Volt Duplex Receptacles
Wired in Sequence
Use this layout to link any number of duplex
receptacles in a basic lighting/receptacle circuit.
The last receptacle in the cable run is connected like
the receptacle shown at the right side of the circuit
map below. All other receptacles are wired like the
receptacle shown on the left side. This configuration
or layout requires two‑wire cables.

2-WIRE CABLE 2-WIRE CABLE

2. GFCI Receptacles
(Single‑Location Protection)
Use this layout when receptacles are within 6 ft. of a
sink or water source, such as those in kitchens and
bathrooms. To prevent nuisance tripping caused by
normal power surges, GFCIs should be connected
only at the line screw terminal so they protect a single
location, not the fixtures on the load side of the circuit.
Requires two‑wire cables. Where a GFCI must protect
other fixtures, use circuit map 3. Remember that
bathroom receptacles should be on a dedicated
20‑amp circuit and that all bathroom receptacles
must be GFCI protected.

150 THE COMPLETE GUIDE TO WIRING

 2-WIRE CABLE 2-WIRE CABLE

LOAD silver LOAD brass

LINE silver LINE brass

3. GFCI Receptacle,
Switch & Light Fixture
(Wired for Multiple‑Location Protection)
In some locations, such as an outdoor circuit, it is
a good idea to connect a GFCI receptacle so it also
provides shock protection to the wires and fixtures
that continue to the end of the circuit. Wires from
the power source are connected to the line screw
terminals; outgoing wires are connected to load
screws. Requires two‑wire cables.

2-WIRE CABLE 2-WIRE CABLE 2-WIRE CABLE

LOAD silver LOAD brass

LINE silver LINE brass

CIRCUIT MAPS 151

 4. Single‑Pole Switch & Light Fixture
(Light Fixture at End of Cable Run)
Use this layout for light fixtures in basic lighting/
receptacle circuits throughout the home. It is often
used as an extension to a series of receptacles (circuit
map 1). Requires two‑wire cables.

2-WIRE CABLE 2-WIRE CABLE

5. Single‑Pole Switch & Light Fixture

(Switch at End of Cable Run)
Use this layout, sometimes called a switch loop, where
it is more practical to locate a switch at the end of
the cable run. In the last length 3‑wire cable is used
to make a hot conductor available in each direction.
Requires two‑wire and three‑wire cables.

2-WIRE CABLE 3-WIRE CABLE

152 THE COMPLETE GUIDE TO WIRING

6. Single‑Pole Switch & Two Light Fixtures
(Switch Between Light Fixtures,
Light at Start of Cable Run)
Use this layout when you need to control two fixtures
from one single‑pole switch and the switch is between
the two lights in the cable run. Power feeds to one
of the lights. Requires two‑wire and three‑wire cables.

2-WIRE CABLE 3-WIRE 2-WIRE

CABLE
CABLE

7. Single‑Pole Switch & Light Fixture,

Duplex Receptacle
(Switch at Start of Cable Run)
Use this layout to continue a circuit past a switched
light fixture to one or more duplex receptacles. To add
multiple receptacles to the circuit, see circuit map 1.
Requires two‑wire and three‑wire cables.

2-WIRE CABLE 3-WIRE CABLE 2-WIRE

CABLE

CIRCUIT MAPS 153

 8. Switch‑Controlled Split Receptacle,
Duplex Receptacle
(Switch at Start of Cable Run)
This layout lets you use a wall switch to control
a lamp plugged into a wall receptacle. This
configuration is required by code for any room that
does not have a switch‑controlled wall or ceiling
fixture. Only the bottom half of the first receptacle
is controlled by the wall switch; the top half of the
receptacle and all additional receptacles on the circuit
are always hot. Requires two‑wire and three‑wire
cables. Some electricians help people identify
switched receptacles by installing them upside down.

2-WIRE
2-WIRE CABLE 3-WIRE CABLE CABLE

Switched half Tab removed

9. Switch‑Controlled Split Receptacle

(Switch at End of Cable Run)
Use this switch loop layout to control a split
receptacle (see circuit map 7) from an end‑of‑run
circuit location. The bottom half of the receptacle
is controlled by the wall switch, while the top half is
always hot. Requires two‑wire and three‑wire cable.
Some electricians help people identify switched
receptacles by installing them upside down.

2-WIRE CABLE 3-WIRE CABLE

Tab removed

Switched half

154 THE COMPLETE GUIDE TO WIRING

10. Switch‑Controlled Split Receptacle,
Duplex Receptacle
(Split Receptacle at Start of Run)
Use this variation of circuit map 7 where it is more
practical to locate a switch‑controlled receptacle at
the start of a cable run. Only the bottom half of the
first receptacle is controlled by the wall switch; the top
half of the receptacle, and all other receptacles on the
circuit, are always hot. Requires two‑wire and three‑
wire cables. Some electricians help people identify
switched receptacles by installing them upside down.

2-WIRE CABLE 3-WIRE

CABLE

Tab removed

Switched half

2-WIRE CABLE

11. Double Receptacle Circuit

with Shared Neutral Wire
(Receptacles Alternate Circuits)
This layout features two 120‑volt circuits wired with
one three‑wire cable connected to a double‑pole
circuit breaker. The black hot wire powers one circuit;
the red wire powers the other. The white wire is
a shared neutral that serves both circuits. When
wired with 12/2 and 12/3 cable and receptacles
rated for 20 amps, this layout can be used for the
two small‑appliance circuits required in a kitchen.
Remember to use a GFCI circuit breaker if you use
this circuit for kitchen countertop receptacles.

Neutral
terminal bar
3-WIRE 3-WIRE 3-WIRE 2-WIRE
CABLE CABLE CABLE CABLE

Terminal bar

CIRCUIT MAPS 155

 12. Double Receptacle
Small‑Appliance Circuit
with GFCIs & Shared Neutral Wire
Use this layout variation of circuit map 10 to wire a
double receptacle circuit when code requires that
some of the receptacles be GFCIs. The GFCIs should
be wired for single‑location protection (see circuit
map 2). Requires three‑wire and two‑wire cables.

12/3 12/3 12/3 12/2

Line
Line Line
brass Line
silver silver
silver
Line Line Line Line
brass brass brass brass

13. Double Receptacle

Small‑Appliance Circuit
with GFCIs & Separate Neutral Wires
If the room layout or local codes do not allow for a
shared neutral wire, use this layout instead. The
GFCIs should be wired for single‑location protection
(see circuit map 2). Requires two‑wire cable.

12/2 12/2 12/2

12/2 12/2 12/2

156 THE COMPLETE GUIDE TO WIRING

14. 120/240‑Volt Range Receptacle
This layout is for a 40‑ or 50‑amp, 120/240‑volt
dedicated appliance circuit wired with 8/3 or 6/3 cable,
as required by code for a large kitchen range. The black
and red circuit wires, connected to a double‑pole circuit
breaker in the circuit breaker panel, each bring 120 volts
of power to the setscrew terminals on the receptacle.
The white circuit wire attached to the neutral bus bar
in the circuit breaker panel is connected to the neutral
setscrew terminal on the receptacle. The receptacle
must be GFCI protected if it is within 6 feet of a sink.

Grounding Neutral bus bar

bus bar

3-WIRE CABLE

15. 240‑Volt Baseboard Heaters,

Thermostat
This layout is typical for a series of 240‑volt baseboard
heaters controlled by a wall thermostat. Except for
the last heater in the circuit, all heaters are wired as
shown below. The last heater is connected to only
one cable. The sizes of the circuit and cables are
determined by finding the total wattage of all heaters.
Requires two‑wire cable.

Coded for hot Coded for hot Baseboard heater

2-WIRE CABLE 2-WIRE

CABLE

Coded for hot 2-WIRE CABLE

From source
To next heater

CIRCUIT MAPS 157

 16. Dedicated 120‑Volt Computer Circuit,
Isolated‑Ground Receptacle
This 15‑amp isolated‑ground circuit provides extra
protection against surges and interference that can
harm electronics. It uses 14/3 cable with the red
wire serving as an extra grounding conductor. The I

red wire is tagged with green tape for identification.

It is connected to the grounding screw on an
isolated‑ground receptacle and runs back to the I

grounding bus bar in the circuit breaker panel without

touching any other house wiring.

Terminal bar Neutral

bus bar

3-WIRE CABLE

Coded
for ground

Silver Brass

Coded
for ground

17. 240‑Volt Appliance

Receptacle
This layout represents a 20‑amp, 240‑volt dedicated
appliance circuit wired with 12/2 cable, as required by
code for a large window air conditioner. Receptacles are
available in both singleplex (shown) and duplex styles.
The black and the white circuit wires connected to a
double‑pole breaker each bring 120 volts of power to
the receptacle (combined, they bring 240 volts). The
white wire is tagged with black tape to indicate it is hot.

Coded for hot

2-WIRE CABLE

Terminal bar Coded for hot

158 THE COMPLETE GUIDE TO WIRING

18. Ganged Single‑Pole Switches
Controlling Separate Light Fixtures
This layout lets you place two switches controlled by
the same 120‑volt circuit in one double‑gang electrical
box. A single‑feed cable provides power to both
switches. A similar layout with two feed cables can be
used to place switches from different circuits in the
same box. Requires two‑wire cable.

2-WIRE CABLE

2-WIRE CABLE 2-WIRE CABLE

19. Ganged Switches Controlling

a Light Fixture and a Vent Fan
This layout lets you place two switches controlled by
the same 120‑volt circuit in one double‑gang electrical
box. A single‑feed cable provides power to both
switches. A standard switch controls the light fixture,
and a time‑delay switch controls the vent fan.

2-WIRE CABLE

2-WIRE
CABLE 2-WIRE
CABLE

CIRCUIT MAPS 159

 20. Three‑Way Switches & Light Fixture
(Fixture Between Switches)
This layout for three‑way switches lets you control a
light fixture from two locations. Each switch has one
common screw terminal and two traveler screws.
Circuit wires attached to the traveler screws run
between the two switches, and hot wires attached to
the common screws bring current from the power
source and carry it to the light fixture. Requires
parallel runs of 2‑wire cable.

2-WIRE CABLE

Traveler
2-WIRE CABLE
2-WIRE CABLE

Common

Coded for hot

Traveler
Common

21. Three‑Way Switches & Light Fixture

(Fixture at Start of Cable Run)
Use this layout variation of circuit map 19 where
it is more convenient to locate the fixture ahead of
the three‑way switches in the cable run. Requires
two‑wire and three‑wire cables.

Traveler
2-WIRE 3-WIRE 2-WIRE CABLE
CABLE CABLE

2-WIRE CABLE

Common
Common

Traveler
Coded for hot

160 THE COMPLETE GUIDE TO WIRING

22. Three‑Way Switches & Light Fixture
(Fixture at End of Cable Run)
This variation of the three‑way switch layout (circuit
map 20) is used where it is more practical to locate
the fixture at the end of the cable run. Requires
two‑wire and three‑wire cables.

2-WIRE CABLE 3-WIRE 2-WIRE CABLE

CABLE

Common Traveler
Common

Traveler
Traveler

23. Three‑Way Switches & Light Fixture

with Duplex Receptacle
Use this layout to add a receptacle to a three‑way
switch configuration (circuit map 21). Requires
two‑wire and parallel runs of two‑wire cables.

2-WIRE CABLE 2-WIRE CABLE

Common
Common

Coded
for hot

2-WIRE
Traveler CABLE
Traveler
2-WIRE 2-WIRE
CABLE CABLE Coded
for hot

CIRCUIT MAPS 161

 24. Three‑Way Switches
& Multiple Light Fixtures
(Fixtures Between Switches)
This is a variation of circuit map 20. Use it to place
multiple light fixtures between two three‑way
switches where power comes in at one of
the switches. Requires two‑ and three‑wire cable.

Coded
for hot
2-WIRE 3-WIRE Common
CABLE CABLE
2-WIRE
CABLE
2-WIRE
CABLE
Common 3-WIRE
CABLE

2-WIRE
CABLE

25. Three‑Way Switches

& Multiple Light Fixtures
(Fixtures at Beginning of Run)
This is a variation of circuit map 21. Use it to place
multiple light fixtures at the beginning of a run
controlled by two three‑way switches. Power comes in
at the first fixture. Requires two‑ and three‑wire cable.

2-WIRE 3-WIRE 3-WIRE 2-WIRE CABLE

CABLE CABLE CABLE

Common
Coded
for hot
Common

2-WIRE CABLE

162 THE COMPLETE GUIDE TO WIRING

26. Four‑Way Switch & Light Fixture
(Fixture at Start of Cable Run)
This layout lets you control a light fixture from three
locations. The end switches are three‑way, and the
middle is four‑way. A pair of three‑wire cables enter
the box of the four‑way switch. The white and red
wires from one cable attach to the top pair of screw
terminals (line 1), and the white and red wires from
the other cable attach to the bottom screw terminals
(line 2). Requires two three‑way switches and one
four‑way switch and two‑wire and three‑wire cables.

2-WIRE 3-WIRE 2-WIRE 2-WIRE

CABLE CABLE CABLE CABLE

Coded
for hot

2-WIRE
CABLE
2-WIRE
CABLE

Coded for hot

27. Four‑Way Switch & Light Fixture

(Fixture at End of Cable Run)
Use this layout variation of circuit map 26 where it is
more practical to locate the fixture at the end of the
cable run. Requires two three‑way switches and one
four‑way switch and two‑wire and three‑wire cables.

2-WIRE CABLE 3-WIRE 3-WIRE 2-WIRE

CABLE CABLE CABLE

Common Common

CIRCUIT MAPS 163

 28. Multiple Four‑Way Switches
Controlling a Light Fixture
This alternate variation of the four‑way switch layout
(circuit map 27) is used where three or more switches
will control a single fixture. The outer switches are
three‑way, and the middle are four‑way. Requires
two three‑way switches and two four‑way switches
and two‑wire and three‑wire cables.

2-WIRE 3-WIRE 3-WIRE 3-WIRE 2-WIRE

CABLE CABLE CABLE CABLE CABLE

Common Common

29. Four‑Way Switches

& Multiple Light Fixtures
This variation of the four‑way switch layout (circuit
map 26) is used where two or more fixtures will be
controlled from multiple locations in a room. Outer
switches are three‑way, and the middle switch is
a four‑way. Requires two three‑way switches and one
four‑way switch and two‑wire and three‑wire cables.

2-WIRE 2-WIRE
2-WIRE 3-WIRE CABLE CABLE
CABLE CABLE

2-WIRE 2-WIRE
3-WIRE CABLE CABLE
CABLE

Coded Coded
for hot for hot

164 THE COMPLETE GUIDE TO WIRING

30. Ceiling Fan/Light Fixture Controlled by Ganged Switches
(Fan at End of Cable Run)
This layout is for a combination ceiling fan/light fixture controlled by a speed‑control switch and dimmer in a
double‑gang switch box. Requires two‑wire and three‑wire cables.

To fan
To light

2-WIRE CABLE 3-WIRE CABLE

31. Ceiling Fan/Light Fixture Controlled by Ganged Switches

(Switches at End of Cable Run)
Use this switch loop layout variation when it is more practical to install the ganged speed control and dimmer
switches for the ceiling fan at the end of the cable run. Requires two‑wire and parallel runs of two‑wire cables.

To light To fan 3-WIRE CABLE

(NEUTRAL
NOT USED)

2-WIRE CABLE 2-WIRE CABLE

CIRCUIT MAPS 165

Common
Wiring Projects

T he instructions that follow show you how to

accomplish the most popular home wiring
projects. Refer to pertinent sections elsewhere in the
book to find background information on tools and
skills needed to get the job done.

In this chapter:
• GFCI & AFCI Breakers • Landscape Lights
• Surge-Protective Devices • Doorbells
• Service Panels • Wireless Switches
• Grounding & Bonding • Baseboard Heaters
a Wiring System • Wall Heaters
• Subpanels • Underfloor Radiant
• 120/240-Volt Heat Systems
Dryer Receptacles • Ceiling Fans
• 120/240-Volt • Remote-Control
Range Receptacles Ceiling Fan Retrofit
• Ceiling Lights • Bathroom Exhaust Fans
• Recessed Ceiling Lights • Range Hoods
• Track Lights • Backup Power Supply
• Undercabinet Lights • Installing a
• Vanity Lights Transfer Switch
• Low-Voltage Cable Lights • Outbuildings
• Hardwired Smoke Alarms • Motion-Sensing
& CO Alarms Floodlights

COMMON WIRING PROJECTS 167

 WHERE ARE AFCI
& GFCI PROTECTION REQUIRED?
Kitchen AFCI & GFCI

Dishwasher AFCI & GFCI

Dining Room AFCI

GFCI & AFCI Breakers Living Room AFCI

Bedrooms AFCI

U nderstanding the difference between GFCI

(ground-fault circuit-interrupter) and AFCI
(arc-fault circuit-interrupter) is tricky for most
Bathrooms

Whirlpool/Jetted Bathtubs
GFCI

GFCI
homeowners. Essentially it comes down to this: Basement GFCI
Arc-fault interrupters keep your house from burning (also AFCI if finished)
down; ground-fault interrupters keep people from
Family Room AFCI
being electrocuted. AFCIs and GFCIs may not be
substituted for each other, and every room in the Den AFCI
house requires one or both types of protection.
The National Electric Code (NEC) requires that Recreation Room AFCI
an AFCI breaker be installed on most branch circuits Library AFCI
that supply outlets or fixtures in newly constructed
homes. The NEC also requires adding AFCI protection Parlor AFCI
to select circuits when you add new circuits and Hallways AFCI
modify or extend existing circuits. Because AFCI
devices protect against faults that commonly lead Closets AFCI
to house fires, they are a prudent precaution in any Laundry Area AFCI & GFCI
home, especially if it has older wiring.
AFCI breakers will not interfere with the Sunroom AFCI
operation of GFCI receptacles, so it is safe to install Garage GFCI
an AFCI breaker on a circuit that contains GFCI
receptacles. Where both AFCI and GFCI protection Outdoors GFCI
are required, the simplest and most protective
Crawl Space (lights & receptacles) GFCI
solution is to install a dual-function GFCI/AFCI
breaker, which provides ground-fault and arc-fault Sump Pump GFCI
protection to the entire circuit.
Swimming Pool & Spa GFCI

GROUND-FAULT CIRCUIT-INTERRUPTERS
A GFCI is an important safety device that disconnects
a circuit or device in the event of a ground fault (when user’s body—a potentially deadly event. A GFCI would
current takes a path other than the neutral back to detect this ground fault and shut off the power before
the panel). One common example demonstrating a the user is badly harmed.
ground-fault risk is the case of the faulty hair dryer: On new construction and when adding or
If a person is using a hair dryer that is not properly extending electrical circuits, GFCI protection is
insulated or protected (most hair dryers today have required for receptacles and equipment in any
their own GFCI protection) and the dryer has an location that might involve moisture, such as by sinks,
internal fault (such as a loose wire), the case of the near kitchen and bath countertops, outdoors, in
dryer can become energized, and that stray electrical basements, and around swimming pools and spas;
current will seek the easiest path to ground. If the see the chart above for specific requirements. In
user touches water or a metal object with their free general, it is a good practice to protect all receptacle
hand, they can create a path to ground (the metal or and fixture locations that could encounter damp or
water), and the fault current can pass through the wet conditions.

168 THE COMPLETE GUIDE TO WIRING

ARC-FAULT CIRCUIT INTERRUPTERS There are two types of arc faults: serial and parallel.
As with a ground fault, an arc fault occurs when A serial, or series, arc fault can occur when there’s a
electrical current follows an unintended path. You’ve small break or gap in series with the electrical load. For
seen an example of minor arching when you unplug example, if a hot wire has a break, an arc fault results
an appliance that is still running, and there’s a small from the electrical current jumping across the gap
spark between the cord prong and the receptacle slot. between the wire ends. A parallel arc fault occurs when
While this arching is relatively harmless, arc faults a hot wire makes contact with another hot wire or a
that occur within house wiring can be very dangerous neutral or ground conductor. A metal staple piercing a
because they create intense heat that can melt wiring cable can make a connection between the hot wire and
insulation and ignite combustible materials, such as another wire inside the cable, resulting in a parallel arc
wood framing. fault. AFCI breakers today are labeled “combination,”

C
B

D
A

Breakers designed for extra protection: 20-amp GFCI (A), 30-amp double-pole GFCI (B), 20-amp combination AFCI (C), and 20-
amp dual-function GFCI/AFCI (D). GFCI and AFCI breakers are identifiable by two features: a white coiled neutral wire (which
connects to the terminal bar in the panel) and a manual test button on the face of the breaker. While today’s GFCI and AFCI
devices include a self-monitoring feature that automatically tests for device failure, it is important to test the breakers manually
(using the test button) as specified by the manufacturer.

COMMON WIRING PROJECTS 169

 meaning they protect against both
serial and parallel arc faults.
How to Install an AFCI, GFCI, or
AFCI protection is required for Dual-Function GFCI/AFCI Breaker
15- and 20-amp, 120-volt circuits
serving most areas of the house,
except for bathrooms, garages,
outdoors, and crawlspaces; see
the chart on page 168 for specific
requirements. The easiest way
to provide AFCI protection for a
circuit is to install an AFCI circuit
breaker. The NEC permits several
alternate methods of providing
AFCI protection, but you should
consult an electrician before using
these alternate methods. You
should use combination AFCI
circuit breakers when installing
new circuits that require AFCI
protection. You should install
either combination AFCI circuit
breakers or AFCI receptacles when
you modify, replace, or extend an
existing circuit that requires AFCI 1
protection.
Locate the breaker for the circuit you’d like to protect. Turn off
DUAL-FUNCTION GFCI/ the main circuit breaker. Remove the cover from the panel,
and test to ensure that power is off (see page 70). Remove
AFCI BREAKERS the breaker you want to replace from the panel. Remove the
Dual-function GFCI/AFCI circuit black wire from the LOAD terminal of the breaker.
breakers provide GFCI and AFCI
protection to an entire circuit from
a single 15- or 20-amp breaker.
Using a dual-function breaker is an
2
easy way to meet the requirement
for rooms that need both GFCI
and AFCI protection, such as
kitchens and basements. Dual-
function breakers should not be
confused with combination AFCI
breakers, which do not provide
GFCI protection. Dual-function is
a GFCI plus a combination AFCI.

TOOLS & MATERIALS

Insulated screwdriver
Voltage tester
Combination tool
AFCI, GFCI, or dual-function GFCI/
AFCI circuit breaker Find the white wire on the circuit you want to protect, and
remove it from the neutral terminal bar.

170 THE COMPLETE GUIDE TO WIRING

r
ker 3 4

Flip the handle of the new AFCI or GFCI breaker to OFF. Connect the new breaker’s coiled white wire to the neutral
Loosen both of the breaker’s terminal screws. Connect the terminal bar on the panel.
black circuit wire to the breaker terminal labeled LOAD
POWER. Connect the white circuit wire to the breaker terminal
labeled PANEL NEUTRAL.

5 6

Make sure all the connections are tight. Snap the new breaker Turn the main breaker on. Turn off and unplug all fixtures and
into the bus bar. appliances on the AFCI or GFCI breaker circuit. Turn the
AFCI or GFCI breaker on. Press the test button. If the breaker
is wired correctly, the breaker trips open. If it doesn’t trip,
check all connections or consult an electrician. Replace the
panel cover.

COMMON WIRING PROJECTS 171

 Surge-Protective
Devices Surge
arrestor
unit

E lectrical surges caused by lighting or utility

malfunctions can destroy or seriously damage
sensitive electronics. Many homes contain tens of
thousands of dollars worth of computers and home
A whole‑house surge arrestor is an
entertainment equipment protected by no more than
inexpensive defense against expensive
a $10 plug-in surge suppressor. While these devices do damage from high-voltage shocks caused
afford a modest level of protection, they are no match for by lightning strikes and power surges.
the voltage a lightning strike will push through a system. Most models install next to the main panel.
And they offer no protection for the wiring itself. Surge-
protective devices (SPD), or whole-house surge arrestors,
provide comprehensive protection for the wiring and
devices attached to it. The NEC now requires surge like standard breakers. Both types provide protection
protection for new and replacement services. for the whole house. Freestanding models are also
Surge-protective devices (SPD) are available in two available with separate protection for phone, data, and
basic types. Type I (SPD I) devices may be installed on cable-television lines—a wise addition if you need to
the utility (line) side of the service equipment (main protect networked computers or cable-TV receivers.
circuit breaker) or may be installed on the load side Whatever style you choose, look for models with the
of the service equipment. Type II (SPD II) devices Underwriters Laboratories 1449 rating and indicator
may be installed only on the load side of the service lights showing that the system is protected. Most
equipment. Do not attempt to install anything on the manufacturers also include a warranty against defect
line side of the service equipment. Leave this work to that covers a certain amount of property damage.
a licensed electrician.
Manufacturers offer units that are housed in
separate boxes (these look like a small subpanel) Cable in from Main circuit Protected tele. out
as well as models that are designed to replace a demarcation jack wires to household jacks

double-pole breaker in the panel itself. These install

Tele. in from
demarcation
TOOLS & MATERIALS jack

Hammer Whole-house surge arrestor

Combination tool Conduit nipple
Screwdrivers and locknuts
Cable ripper Two 15- or 20-amp Surge arrestor
single-pole breakers Protected
Linesman’s pliers Dedicated breakers cable‑TV out to
Coaxial cable for surge arrestor
Circuit tester household jacks
and terminators
Crimping tools A surge arrestor installed at the panel protects all downstream
UTP cable and terminators
connected devices and wires.

172 THE COMPLETE GUIDE TO WIRING

 How to Install a Whole-House Surge Arrestor

1 2

Turn off power at the main breaker. Remove the cover, and Trim the wires as short as possible without making sharp
test to make sure the power is off. Mount the arrestor near bends. Connect the two black wires to two dedicated 15- or
the service panel following the manufacturer’s instructions. 20-amp breakers. Connect the white neutral wire to the
Typically the arrestor mounts on one side of the panel so neutral bar and the green grounding wire to the grounding
its knockout lines up with a lower knockout on the panel. bar. Keep wire lengths as short as possible. Snap the new
Remove the knockout on the panel. Install a conduit nipple breakers into the bus bar. Restore the power and carefully test
on the arrestor, and thread the wires from the arrestor through that the voltage between the two black arrestor leads is 240
the nipple and into the panel. Slip the other end of the nipple volts. Replace the panel cover and the arrestor cover. If the
through the opening in the panel, and tighten the locknut. arrestor has indicator lights, they should glow, showing that
Secure the box to the wall with screws as directed. the system is now protected.

VARIATION: If the arrestor has separate protection for a

cable television circuit, remove the appropriate knockout
LINE bar from the arrestor and run a coaxial cable to the arrestor
from the cable-TV demarcation jack. Connect the coaxial
cable to the ANT-IN terminal on the cable-TV protection
module. Run another coaxial cable from the TV-OUT
terminal to the cable TV junction box or the distribution
panel. Do not overtighten the connections.

TV‑OUT terminal

EQUIPMENT bar

VARIATION: If the arrestor has separate protection for the

telephone circuits, remove the cable that runs from the
phone demarcation jack to the junction box. Then remove
a knockout in the arrestor and route a new UTP cable from
the demarcation jack to the arrestor. Strip insulation
from the wires and connect them to the terminals on
the LINE bar (labeled IN on some models) on the phone
protection module in the arrestor. Run a UTP cable from
the EQUIPMENT bar (labeled OUT on some models) to the
ANT‑IN terminal
junction box. Strip and connect the wires from this cable to
the appropriate terminals in the arrestor and the junction box.

COMMON WIRING PROJECTS 173

 Service Panels

R eplacing an old 60- or 100-amp electrical service panel with a

new 200-amp panel is an ambitious project that requires a lot of
forethought. Upgrading your electrical service panel from 100 amps to
200 amps is an ambitious project that requires a lot of forethought. The
first step is to obtain a permit. When you are ready to begin, you will
need to have your utility company disconnect your house from electrical
service at the transformer that feeds your house. When you schedule
Before
this, talk to your utility company about the size of your service drop or
lateral. That may need to be upgraded too.
Also check with your utility company to make sure you know what
equipment is theirs and what belongs to you. In most cases, the electric
meter and everything on the street side belongs to the power company,
and the meter base and everything on the house side is yours. Be aware
that if you tamper with the sealed meter in any way, you likely will
be fined. Utility companies will not re-energize your system without
approval from your inspecting agency.

Note: The NEC requires outdoor emergency disconnects for home

services in new construction, homes undergoing renovation, and all
service replacements. An exterior disconnect allows emergency crews
to shut off the power. Approved disconnects include
• Service disconnects
• Meter disconnects
• Listed disconnect switches or circuit breakers

Disconnects may be located before or after the meter base and may be
in their own enclosure. They must be clearly labeled. Check with the
local code authority for specific requirements.

After
TOOLS & MATERIALS
Modern homeowners consume more
200-amp service panel Weatherhead Drill/driver
power than our forebears, and it
200-amp bypass meter Service cable Tape is often necessary to upgrade the
base Circuit wires Allen wrench electrical service to keep pace. While
homeowners are not allowed to make
Circuit breakers Plywood backer board Circuit tester the final electrical service connections,
Schedule 80 or RMC Screwdrivers Multimeter removing the old panel and installing
conduit and fittings the new panel and meter base yourself
can save you hundreds or even
thousands of dollars.

174 THE COMPLETE GUIDE TO WIRING

 Service drop cables
Weatherhead

Service mast

RMC conduit

Power meter
Emergency
disconnect Service
Meter base entrance
cables
Power meter
Service
disconnect

Strap
Meter base

Service Conduit
entrance
cables

Service lateral cables

Aboveground service drop. In this common configuration, Underground service lateral. Increasingly, homebuilders
the service cables from the closest transformer (called the are choosing to have power supplied to their new homes
service drop) connect to service entrance wires near the underground instead of an overhead service drop. Running
weatherhead. This connection is called the service point the cables in the ground eliminates problems with power
and is where your property usually begins. The service outages caused by ice accumulation or fallen trees, but
entrance wires from the weatherhead are routed to a power it entails a completely different set of cable and conduit
meter that’s owned by your utility company but is housed in requirements. For the homeowner, however, the differences
a base that’s considered your property. From the meter, the are minimal, because the hookups are identical once the
service entrance wires enter your house through the wall power service reaches the meter.
and are routed to the main service panel, where they are
connected to the main circuit breaker.

COMMON WIRING PROJECTS 175

 LOCATING YOUR NEW PANEL
A
Local codes dictate where the main service panel
may be placed relative to other parts of your
home. Although local codes vary (and always take
precedence), national codes stipulate that a service
panel (or any other distribution panel) may not be B
located near flammable materials, in a bathroom,
clothes closet or other area designated for storage,
above stairway steps, or directly above a workbench D
or other permanent work station or appliance. The
panel also can’t be located in a crawl space. If you are
F
installing a new service entry hookup, there are many C
regulations regarding height of the service drop and
the meter. Contact your local inspections office for
specific regulations.
E

All the equipment you’ll need to upgrade your main panel is

sold at most larger building centers. It includes (A) a new
200-amp panel; (B) a 200-amp bypass meter base (also
Minimum called a socket); (C) individual circuit breakers; (D) new,
78" high THW, THHW, THWN-2. RHW, RHW-2, XHHW 2/0 copper
unobstructed or 4/0 aluminum; (E) 2"-diameter rigid metallic conduit;
access
(F) weatherhead for mast.

Maximum circuit
breaker height 79"
(ideal height 60")

Meter

Shutoff switch
Minimum 36" deep
unobstructed access
Minimum 30" wide
unobstructed access
The main circuit breaker (called the service equipment)
may need to be located outside next to the electric meter
Attach to studs or if your main panel is too far away from the point where the
to ¾" plywood backer service cable enters your house. The maximum distance
allowed varies widely, from as little as 3 ft. to more than 10
ft. Wiring the service cable through the shutoff has the effect
of transforming your main panel into a subpanel, which will
impact how the neutral and ground wires are attached (see
Subpanels, pages 188–191).

176 THE COMPLETE GUIDE TO WIRING

 How to Replace a Main Panel

1 2
Shut off power to the house at the transformer. This must be Label all incoming circuit wires before disconnecting
done by a technician who is certified by your utility company. them. Labels should be written clearly on tape that is
Also have the utility worker remove the old meter from the attached to the cables outside of the existing service panel.
base. It is against the law for a homeowner to break the seal Test the circuits before starting to make sure they are
on the meter. labeled correctly.

3 4
Disconnect incoming circuit wires from breakers, grounding Unscrew the lugs securing the service entry cables at the top
bar, and neutral terminal bar. Also disconnect cable clamps of the panel. For 240-volt service you will find two heavy-
at the knockouts on the panel box. Retract all circuit wires gauge SE cables, probably with black sheathing. Each
from the service panel and coil them up neatly, with the labels cable carries 120 volts of electricity. A neutral service cable,
clearly visible. usually of smaller gauge than the SE cables, will be attached
to the neutral terminal bar. This cable returns current to
the source. (continued)

COMMON WIRING PROJECTS 177

 5 6

Remove the old service panel box. Boxes are rated for a Replace the old panel backer board with a larger board in
maximum current capacity; and if you are upgrading, the the installation area (see sidebar, page 174). A piece of ¾"
components in the old box will be undersized for the new plywood is typical. Make sure the board is well secured to wall
service levels. The new box will have a greater number of framing members.
circuit slots as well.

7 8

Attach the new service panel box to the backer board, making Attach properly sized cable clamps to the box at the knockout
sure that at least two screws are driven through the backer holes. Install one cable per knockout in this type of installation
and into wall studs. Drill clearance holes in the back of the and plan carefully to avoid removing knockouts that you do
box at stud locations if necessary. Use roundhead screws not need to remove (if you do make a mistake, you can fill the
that do not have tapered shanks so the screwhead seats flat knockout hole with a plug).
against the panel.

178 THE COMPLETE GUIDE TO WIRING

 SPLICING IN THE BOX
Some wiring codes allow you to make splices inside the
panel box if the circuit wire is too short. Use the correct
wire cap and wind electrical tape over the conductors
where they enter the cap. If your municipality does
not allow splices in the panel box, you’ll have to rectify
a short cable by splicing it in a junction box before it
reaches the panel and then replacing the cable with a
longer section for the end of the run. Make sure each
circuit line has at least 12" of slack.

9
Attach the white neutral from each circuit cable to the neutral
terminal bar. Most panels have a preinstalled neutral terminal
bar, but in some cases you may need to purchase the bar
separately and attach it to the panel back. The panel should
also have a separate grounding bar that you also may need to
purchase separately. Attach the grounds as well.

Note: For GFCI and AFCI breakers, the neutral circuit wire
connects to the breaker, and the breaker's coiled neutral
lead connects to the neutral terminal bar.

10 11
Attach each hot circuit wire to the terminal on the circuit Create an accurate circuit index and affix it to the inside of the
breaker, and then snap the breaker into an empty slot. When service panel door. List all loads that are on the circuit as well
loading slots, start at the top of the panel and work your way as the amperage. Once you have restored power to the new
downward. It is important that you balance the circuits as you service panel, test out each circuit to make sure you don’t
go to equalize the amperage. For example, do not install all have any surprises. With the main breakers on, shut off all
the 15-amp circuits on one side and all the 20-amp circuits individual circuit breakers, and then flip each one on by itself.
on the other. Walk through your house and test every switch and receptacle
to confirm the loads on that circuit. (continued)

COMMON WIRING PROJECTS 179

 12 13

Install grounding conductors (see pages 182–187). Local Replace the old meter base (have the utility company
codes are very specific about how the grounding and remove the meter when they shut off power to the house,
bonding needs to be accomplished. For example, some step 1). Remove the old meter base, also called a socket,
require multiple rods driven at least 6 ft. apart. Discuss your and install a new base that’s rated for the amperage of your
grounding requirements thoroughly with your inspector or an new power service. Here, a 200-amp bypass meter base is
electrician before making your plan. being installed.

14 15

Update the conduit that runs from your house to the bottom Install new service entrance wires. Each wire carries 120 volts
of the meter base. This should be 2" rigid conduit in good from the meter to the service wire lugs at the top of your
repair. Attach the conduit to the base and wall with the service panel. Also attach the sheathed neutral wire to the
correct fittings. Rigid metal conduit is a good option, but neutral/grounding lug.
Schedule 80 PVC is probably the best choice for housing
the service entrance wires. Note: Refer to the manufacturer specifications for all panel
and meter connections. All terminals must be torqued to
specifications.

180 THE COMPLETE GUIDE TO WIRING

 16 17
Attach the SE wires to the lugs connected to the main Install service entrance wires from the meter to the
breakers at the top of your service entry panel. Do not remove weatherhead, where the connections to the service drop wires
too much insulation on the wires—leaving the wires exposed are made. Only an agent for your public utility company may
is a safety hazard. The neutral service entry wire is attached make the hookup at the weatherhead.
either directly to the neutral terminal bar or to a metal bridge
that is connected to the neutral bonding terminal bar. Install
the green grounding screw provided with the panel.

TALL MAST, SHORT ROOF

18
The service drop must occur at least 10 ft. above
ground level, and as much as 14 ft. in some cases.
Occasionally, this means that you must run the conduit
for the service mast up through the eave of your roof
and seal the roof penetration with a boot.

Service drop Weatherhead

Mast
(conduit)
Boot minimum
18 inches from the
bottom of the drip loop

Have the panel and all connections inspected and approved

by your local building department, and then contact the
public utility company to make the connections at the power
drop. Once you have restored power to the new service
panel, test out each circuit to make sure you don’t have any
surprises. With the main breakers on, shut off all individual
circuit breakers, and then flip each one on by itself. Walk
through your house and test every switch and receptacle to
confirm the loads on that circuit.

COMMON WIRING PROJECTS 181

 Grounding & Bonding
a Wiring System

A ll home electrical systems must be bonded and

grounded according to code standards. This
entails two tasks: the metal water and gas pipes must
be connected electrically to create a continuous low
resistance path back to the main electrical panel; and the
main electrical panel must be grounded to a grounding
electrode such as a ground rod or rods driven into the
earth near the foundation of your house. Although the
piping system is bonded to the ground through your
main electrical service panel, the panel grounding
and the piping bonding are unrelated when it comes
to function. The grounding wire that runs from your
electrical panel to grounding electrode helps even out
voltage increases that often occur because of lightning
and other causes. The wires that bond your metal piping
are preventative, and they only become important in the
unlikely event that an electrical conductor energizes the
pipe. In that case, correct bonding of the piping system
will ensure that the current does not remain in the
system, where it could shock anyone who touches a part
of the system, such as a faucet handle. Bonding is done
relatively efficiently at the water heater, as the gas piping
and water piping are typically located there.
Gas pipe in older homes is usually steel or copper.
The bonding connection point for these pipes can be
at any accessible location, such as at the water heater
or at the gas meter. Gas pipe in some new homes
is a flexible material called corrugated stainless- A pair of 8‑ft.‑long metal ground rods are driven into the earth
steel tubing (CSST). Refer to the manufacturer's next to your house to provide a path to ground for your home
instructions for bonding the CSST. wiring system.

TOOLS & MATERIALS

Hammer ½" drill bit 3 pipe ground clamps Grounding rods
Flat screwdriver A length of ground wire Eye and ear protection 5-lb. maul
Drill Wire staples Work gloves Caulk

182 THE COMPLETE GUIDE TO WIRING

 How to Bond Metallic Piping

1 2

Determine the amperage rating of your electrical service by Run the bonding wire from a point near your water heater to
looking at your main breakers. (If you have an older system an exit point where the wire can be bonded to the grounding
and are unsure about its amperage rating, consult an wire that leads to the exterior grounding electrodes. This is
electrician.) The system amperage (usually 100 or 200 amps) frequently done at the service panel. Run this wire as you
determines the required gauge of the bonding wire you need. would any other cable, leaving approximately 6 to 8 ft. of wire
#6 copper wire is often sufficient for service not exceeding at the water heater. If you are running this wire through the
200 amps. Always confirm the correct gauge with the local ceiling joists, drill a ½" hole as close to the center as possible
electrical inspector. to not weaken the joist. Staple the wire every 2 ft. if running it
parallel to the joists.

3 4

Install pipe ground clamps on each pipe (hot water supply, Route the ground wire through each clamp wire hole and then
cold water supply, gas), roughly 1 foot above the water heater. tighten the clamps onto the wire. Do not cut or splice the
Do not install clamps near a union or elbow because the wire: the same wire should run through all clamps.
tightening of the clamps could break or weaken soldered
joints. Also make sure the pipes are free and clear of any
paint, rust, or any other contaminant that may inhibit a good
clean connection. Do not overtighten the clamps. Use clamps
that are compatible with the pipe so that corrosion will not
occur. Use copper or brass clamps on copper pipe. Use brass
or steel clamps on steel pipe. (continued)

COMMON WIRING PROJECTS 183

 5 6
At the panel, turn off the main breaker. Open the cover by Locate an open hole on your ground and neutral terminal
removing the screws, and set the cover aside. Route the and insert the ground wire. These holes are large enough to
ground wire through a small 3⁄8" hole provided toward the rear of accommodate up to a #4 awg wire, but it may be difficult at
the panel on the top or bottom. You will usually have to knock times. If you’re having trouble pushing the wire in, trim a little
the plug out of this hole by placing a screwdriver on it from the wire off the end and try with a clean cut piece. Secure the set
outside and tapping with a hammer. Make sure the ground wire screw at the lug. Replace the panel cover and turn the main
will not come into contact with the terminal bars in the middle breaker back on.
of the panel or any of the load terminals on the breakers.

Tips for Grounding Service Panels

Neutral bus

Cabinet ground
Neutral bus screw isolated
from neutral bus

Grounding bus

In a subpanel, the grounding terminal should be bonded to Metallic conduit must be physically and electrically connected
the subpanel cabinet. The neutral terminal should not be to panel cabinets. A bonding bushing may be required in
bonded to the subpanel cabinet. some cases, where not all of a knockout is removed.

184 THE COMPLETE GUIDE TO WIRING

Ground Rod Installation

T he ground rod is an essential part of the grounding

system. Its primary function is to create a path to
ground for electrical current, such as lightning, line
Call before you dig! Make sure the area where you
will be installing the ground rods is free and clear
from any underground utilities.
surges, and unintentional contact with high voltage
lines. If you upgrade your electrical service, you likely NOTE: Different municipalities have different
will need to upgrade your grounding wire and rods to requirements for grounding, so be sure to check
meet current code. with the AHJ (Authority Having Jurisdiction) first
before attempting to do this yourself.

TOOLS & MATERIALS

5
⁄8" × 8' ground rods 5-pound maul Screwdriver Wire cutters
Drill 1/4 Copper ground wire (2) brass (acorn) clamp Caulk
5
⁄16" drill bit (size as required by Pliers
local code)
Ladder

How to Install a Grounding Electrode System

1 2

Begin by purchasing two copper‑coated steel ground rods 5/8" Drill a 5/16" hole in the rim joist of your house, as close as
diameter by 8' long. Grounding rods have a driving point on practical to the main service panel to the outside of the house
one end and a striking face on the other end. above the ground level at least 6". (continued)

COMMON WIRING PROJECTS 185

 3 4

About 1 foot from the foundation of the house, pound one Run uninsulated copper ground wire from the ground bus in
ground rod into the earth with a 5-lb. maul. If you encounter a your main service panel through the hole in the rim joist and
rock or other obstruction, you can pound the ground rod at an to the exterior of the house, leaving enough wire to connect
angle as long as it does not exceed 45°. Drive until only 3" or the two ground rods together.
4" of the rod is above ground. Measure at least 6 ft. from the
first ground rod and pound in another one.

5 6

Using a brass clamp commonly referred to as an acorn, Connect the second ground rod with another acorn to the
connect the wire to the first ground rod, pulling the wire taut uncut grounding wire previously pulled through the first
so no slack exists. Continue pulling the wire to reach the acorn. Trim the excess wire.
second grounding rod, creating a continuous connection.

186 THE COMPLETE GUIDE TO WIRING

 7 8

Dig out a few inches around each rod to create clearance Inject caulk into the hole in the rim joist on both the interior
for the 5-lb. maul. Creating a shallow trench beneath the and exterior side.
grounding wire between the rods is also a good idea. Drive
each rod with the maul until the top of the rod is a few inches
below grade.

Tips for Grounding & Bonding

Grounding electrode

Intersystem bonding terminal

Use an intersystem bonding terminal to ground nonelectrical A piece of reinforcing bar encased in a concrete footing is a
systems such as telephone and cable. common grounding electrode in new construction. Called an
ufer, the electrode must be No. 4 or larger rebar and at least
20 ft. long. (Shown prior to pouring concrete.)

COMMON WIRING PROJECTS 187

 Single‑pole
circuit breakers

Subpanels

I nstall circuit breaker subpanels if the main circuit

breaker panel does not have enough open breaker
slots for the new circuits you are planning. Subpanels Before
serve as additional distribution centers for connecting
circuits. They receive power from a double-pole circuit
breaker you install in the main circuit breaker panel.
If the main service panel is so full that there is
no room for the double-pole subpanel breaker, you
Slimline breakers replace
can reconnect some of the existing 120-volt circuits single‑pole breakers
to special slimline breakers (see photo at right). You
may be required to install AFCI breakers for the new
circuits. AFCI breakers are full size breakers. Be sure
to plan for this when estimating the space left in your
existing main service panel and all subpanels.
Plan your subpanel installation carefully, making
sure your electrical service supplies enough power to
support the extra load of the new subpanel circuits.
Assuming your main service is adequate, consider
installing a subpanel that’s a little larger than you
need to provide enough extra amps to meet the
needs of future wiring projects.
Also consider the physical size and the current After

rating of the subpanel, and choose one that has

enough extra slots and current capacity to hold To conserve space in a service panel, you may be able to
circuits you may want to install later. The smallest replace existing single-pole breakers with slimline breakers.
Slimline breakers take up half the space of standard breakers,
panels have room for up to six single-pole breakers (or allowing you to fit two circuits into one single slot on the service
three double-pole breakers), while the largest models panel. In the service panel shown above, four single-pole
can hold 20 single-pole breakers or more. 120-volt breakers were replaced with slimline breakers to
Subpanels often are mounted near the main circuit provide the double opening needed for a 30-amp, 240-volt
breaker panel. Or, for convenience, they can be installed subpanel feeder breaker. Use slimline breakers (if your
municipality allows them) with the same amp rating as the
close to the areas they serve, such as in a new room
standard single-pole breakers you are removing, and make sure
addition. In a finished room, a subpanel can be painted they are approved for use in your panel. If your municipality and
or housed in a decorative cabinet so it is less of a visual panel allow slimline breakers, there may be restrictions on the
distraction—just make sure it’s accessible. quantity and location where they may be installed on the panel.

TOOLS & MATERIALS

Hammer Cable ripper Cable clamps Double-pole circuit breaker
Screwdriver Combination tool Three-wire NM cable Circuit breaker subpanel
Voltage tester Screws Cable staples Slimline circuit breakers

188 THE COMPLETE GUIDE TO WIRING

 Service panel in main building Subpanel in detached building

Neutral Hot

Hot

Neutral
terminal
Ground
bar

Grounding
Neutral terminal bar Grounding terminal bar
terminal
bar Jumpers

Neutral
Electrode Electrode

Wiring diagram for wiring a feeder from the main service panel to a subpanel in a separate building.

How to Install a Subpanel

Subpanels are subject to the same
installation and clearance rules as
service panels. The subpanel can ½"
be mounted to the sides of studs or
to plywood attached between two
studs. The panel shown here extends
½" past the face of studs so it will be
flush with the finished wall surface.
Follow the manufacturer’s installation
specifications.

Open a knockout in the subpanel using Attach a cable clamp to the knockout in
a screwdriver and hammer. Run the the subpanel. Insert the cable into the
feeder cable from the main circuit subpanel, and then anchor it to framing
breaker panel to the subpanel, leaving members within 8" of each panel and
about 2 ft. of excess cable at each end. every 54" thereafter.
See page 40 if you need to run the
cable through finished walls.

(continued)

COMMON WIRING PROJECTS 189

 Main lug

Lug

Hot bus bars

Neutral
terminal bar

Grounding Lug
terminal bar

4 5 6
Strip away outer sheathing from the Strip ½" of insulation from the white Strip away ½" of insulation from the red
feeder cable using a cable ripper. Leave neutral feeder wire, and attach it to and the black feeder wires. Attach one
at least ¼" of sheathing extending into the main lug on the subpanel neutral wire to the main lug on each of the hot
the subpanel. Tighten the cable clamp terminal bar. Connect the grounding terminal bars. Fold excess wire around
screws so the cable is held securely, wire to a setscrew terminal on the the inside edge of the subpanel.
but not so tightly that the wire sheathing grounding terminal bar. Fold excess
is crushed. wire around the inside edge of
the subpanel.

Slimline
breakers

7 8
At the main circuit breaker panel, shut off the main circuit Strip away the outer sheathing from the feeder cable so that
breaker, and then remove the coverplate and test for power at least ¼" of sheathing will reach into the main service
(page 80). If necessary, make room for the double-pole feeder panel. Attach a cable clamp to the cable, and then insert the
breaker by removing single-pole breakers and reconnecting cable into the knockout, and anchor it by threading a locknut
the wires to slimline circuit breakers. Open a knockout for the onto the clamp. Tighten the locknut by driving a screwdriver
feeder cable using a hammer and screwdriver. against the lugs. Tighten the clamp screws so the cable is
held securely, but not so tightly that the cable sheathing
NOTE: Some panels do not allow slimline breakers and some is crushed.
restrict where slimline breakers can be installed. Read the
instructions on the panel cover.

190 THE COMPLETE GUIDE TO WIRING

 9 10
Grounding terminal bar

Neutral terminal bar

Bend the bare copper wire from the feeder cable around Strip away ½" of insulation from the white feeder wire. Attach
the inside edge of the main circuit breaker panel, and the wire to one of the setscrew terminals on the neutral
connect it to one of the setscrew terminals on the grounding terminal bar. Fold excess wire around the inside edge of the
terminal bar. service panel.

Guide hook pivot

11 12 13
Strip ½" of insulation from the red and Hook the end of the feeder circuit If necessary, remove two tabs from
the black feeder wires. Attach one wire breaker over the guide hooks on the the cover plate where the double-pole
to each of the setscrew terminals on the panel, and then push the other end feeder breaker will fit, and then reattach
double-pole feeder breaker. forward until the breaker snaps onto the the cover plate. Label the feeder
hot terminal bars (follow manufacturer’s breaker on the circuit index. Turn the
NOTE: If your subpanel arrived with a directions). Fold excess wire around the main breaker on, but leave the feeder
preinstalled grounding screw in the inside edge of the circuit breaker panel. breaker off until all subpanel circuits
panel back, remove and discard it. have been connected and inspected.

COMMON WIRING PROJECTS 191

 ¾" conduit to circuit 30‑amp, 120/240‑volt
breaker panel receptacle for dryer

4" × 4"
metal box

120/240-Volt
Conduit raceway shown
is used for 120/240V
12‑gauge wires
dryer receptacle and
for a 120‑volt circuit
Dryer Receptacles 10‑gauge wires
120V wall receptacle.

(green, black, white, red)

M ost electric dryers require both 120- and 240-volt

power. If you are installing this type of electric
dryer, you will need to install a 30-amp, 120/240-volt
With a 120/240‑volt installation, the dryer circuit’s
double-pole breaker contacts both 120-volt hot bus bars
in the service panel.

receptacle that feeds from a dedicated 30-amp

double-pole GFCI breaker in your service panel. Verify dryer receptacle box on an unfinished masonry wall,
your dryer’s electrical requirements before wiring a run THNN wire in conduit and secure the box and
new receptacle. conduit with straps and masonry screws. If you are
Begin the installation by identifying a location for mounting the receptacle box in a finished wall, cut a
the dryer receptacle. Run 10/3 NM cable from the hole, fish the cable through, and mount the receptacle
panel to the new receptacle. If you are mounting the in the wall opening.

TOOLS & MATERIALS

Combination tool Hammer 30-amp 120/240-volt 10/3 NM cable
Drill Screwdriver dryer receptacle or 10-gauge THHN/THWN
Circuit tester 30-amp double-pole  Receptacle box Conduit (for masonry walls)
GFCI breaker

How to Install a 120/240-Volt Dryer Receptacle

With the panel main breaker
shut off, connect the dryer
1 2 cable to a dedicated 30-amp
double-pole GFCI breaker.
Connect the ground wire to
the panel grounding terminal
bar. Connect the white
neutral wire to the neutral bar.
Connect the red and the black
wires to the two brass screw
terminals on the breaker.
Connect the coiled white wire
Connect the white neutral wire to the silver neutral screw to the neutral terminal bar.
terminal. Connect each of the black and the red wires Snap the breaker into the bus
to either of the brass screw terminals (the terminals are bar. Attach the panel cover.
interchangeable). Connect the green ground wire to the Restore power to the panel,
receptacle grounding screw. Attach the cover plate. and test the GFCI breaker and
dryer receptacle.

192 THE COMPLETE GUIDE TO WIRING

 Modern range receptacles accept a four-prong plug.
A four-conductor cable, containing three insulated
wires and one ground, is required. The two hot wires
might be black and red (shown below) or black and
black with a red stripe. The neutral wire is generally
120/240-Volt white or gray. The grounding wire is green or bare. The
size used for a kitchen range is usually 6/3 grounded

Range Receptacles NM aluminum or copper cable. The receptacle itself

is generally surface mounted (shown below), though
flush-mounted units are also available.

M any electric ranges require both 120- and Note: If the range receptacle is within 6 feet of a sink,
240-volt power and use a 40- or 50-amp the circuit may need to be GFCI protected. Check the
120/240-volt receptacle that feeds from a dedicated local building department for requirements.
40- or 50-amp breaker in the panel. Breaker amperage
depends on the amount of current the range draws.
Verify requirements before wiring a receptacle.
A range receptacle and breaker installation is TOOLS & MATERIALS
no more complicated than wiring a single-pole Combination tool Range receptacle
breaker and outlet. The main difference is that the
range circuit’s double-pole breaker is designed to Voltage tester 6/3 grounded NM cable
contact both 120-volt bus bars in the service panel. Screwdriver 40- or 50-amp double-pole
Together these two 120-volt circuits serve the range’s Drywall saw circuit breaker
heating elements with 240 volts of power. The range’s Fish tape
electronics utilize the circuit’s 120-volt power.

How to Install a Kitchen Range Receptacle

1 2 3
Turn power off. Identify a location for Wire the receptacle. Connect the bare Wire the cable to a 40- or 50-amp
the surface-mounted range receptacle. copper ground wire to the receptacle breaker. With the main breaker off,
Cut a small hole in the wall. Fish the grounding screw. Connect the white remove the panel cover. Remove a
cable from the service panel into neutral wire to the silver neutral screw knockout from the panel and feed the
the wall opening. Thread the cable terminal. Connect each of the hot cable into the panel. Connect the ground
into a surface-mounted receptacle (black and red) wires to either of the to the grounding terminal bar. Connect
and clamp it. Strip insulation from the brass screw terminals (the terminals are the neutral wire from the cable to the
individual wires. interchangeable). Mount the housing on neutral terminal bar. Connect the red
the wall and attach the cover plate. and the black wires to the two brass
screw terminals on the breaker. Snap it
into the bus bar. Attach the panel cover.
Turn the breakers on and test the circuit.

COMMON WIRING PROJECTS 193

 TOOLS & MATERIALS
Screwdrivers
Nut driver (as needed)
Ground strap (as needed)
UL-listed dryer or range

Dryer and Range Cords appliance cord

Strain-relief fitting

E lectric dryers and ranges typically are sold without power cords. This
can be vexing for consumers, especially if their appliance dealer fails
to advise them to buy a new cord before they leave the store. But this
three-wire receptacles. And that’s
why appliance manufacturers
leave it up to the consumer to
quirk exists for a very good reason. In 1996, the NEC began requiring get the right cord for their home’s
that newly installed dryer and range receptacles must be designed for dryer or range receptacle.
four-wire power cords. Prior to this change, most homes were built with Installing a cord on a new
receptacles for three-wire cords. appliance, or swapping out the
The code change continued trickling down to the local level well into cord on an older appliance, is a
the 2000s, and since dryers and ranges can easily last for 20 or 30 years, very easy job that takes just a few
there are a lot of older appliances and receptacles out there with 3-wire minutes. The important thing is to
configuration. Fortunately, the NEC allows homeowners to use existing properly configure the appliance
for a 3-wire or 4-wire cord, as
needed. On the back of the dryer
or range, there is a terminal block
with three terminals: one neutral
and two hots. There is also a
ground screw that grounds the
metal case of the appliance. A
4-wire, or 4-prong, cord has two
hot wires, a neutral, and a separate
ground wire. A 3-wire, or 3-prong,
cord has two hots and a neutral—
with no ground wire; it uses the
neutral as a ground.
With a 4-wire configuration,
the ground screw is isolated from
the neutral terminal so that the
ground and neutral are separate.
With a 3-wire configuration, the
ground screw is connected to the
neutral with a metal ground strap.
Some appliances have a small wire
(usually with white insulation)
that connects to the ground screw;
this does the same thing as a
metal strap. Once the appliance
configuration is correct for your
cord type, you simply connect
Cords for electric dryers and ranges are sold at appliance outlets and hardware each wire to its respective terminal
and home improvement stores. They come in standard 4- to 6-foot lengths and
(pages 196 and 197 show these
usually include a strain-relief fitting for securing the cord to the appliance. Make
sure any cord you use carries the UL stamp or similar certification to ensure that setups clearly).
it meets industry safety standards.

194 THE COMPLETE GUIDE TO WIRING

4‑prong range cords have red and black hot wires, a white 4‑prong dryer cords have red and black hot wires, a white
neutral wire, and a green ground wire. The hot wires carry neutral wire, and a green ground wire. The hot wires carry
120 volts each and are interchangeable. These cords are 120 volts each and are interchangeable. They are typically
typically rated for 50 amps and plug into a 4-slot NEMA 14- rated for 30 amps. Dryer receptacles are identifiable by their
50 50-amp receptacle. L-shaped neutral slots.

3‑prong dryer cords are flat and do not have color-coded Strain‑relief fittings are simple metal clamps that secure the
wires. The center wire is always neutral. The two outer wires cord to the appliance and protect the cord sheathing from
are hot and carry 120 volts each; they are interchangeable. damage. Strain reliefs for 4-prong cords (top) are rounded;
There is no separate ground wire. These cords typically strain reliefs for 3-prong cords (bottom) are flat. Always use
are rated for 30 amps and must be used with matching an appropriate strain relief for the cord shape.
3-slot receptacles.

COMMON WIRING PROJECTS 195

 1 2
Loosen the screws on the wiring compartment cover on the Remove each cord wire from its terminal on the terminal block
back of the dryer or range, using a screwdriver or nut driver. (and ground screw, as applicable), if you’re replacing an
Remove the cover and set it aside. existing cord. Loosen the screws of the strain-relief fitting and
remove the fitting. Pull the cord out through the hole in the
back panel or bracket.

3 4
Configure the terminals for a 4‑wire cord. Confirm that Connect a 4‑wire cord. Secure the white cord wire under
the ground screw is isolated from the neutral (center) terminal the neutral (center) terminal. Secure the black (hot) and
on the terminal block. If there is a metal strap between the red (hot) cord wires to the two outer terminals, connecting
ground and neutral, remove the strap from the neutral (you only one wire to each terminal (the hot terminals and wires
can leave it attached under the ground screw). If there is are interchangeable). Connect the green ground wire to the
a white or green internal wire connected to the ground screw, ground screw. Make sure all connections are very tight.
move it to the neutral terminal; it will make a harmless
neutral connection.

196 THE COMPLETE GUIDE TO WIRING

 VARIATION: Configure the terminals for a 3‑wire cord. VARIATION: Connect a 3‑wire cord. Secure the
Confirm that the ground screw is connected to the center (neutral) cord wire under the neutral (center)
neutral (center) terminal on the terminal block. terminal. Secure each of the outer cord wires to one
Make this connection with a metal ground strap of the outer (hot) terminals, connecting only one wire
between the ground screw and the neutral terminal. to each terminal (the hot terminals and wires are
Alternatively, if there is a white or green wire interchangeable). Make sure all connections are
extending from inside the appliance, make sure it is very tight.
secured under the ground screw.

Note: If the dryer does not have a ground strap

or wire, you can buy a new ground strap that is
compatible with the dryer model.

5 6
Install the strain relief by fitting the two halves together so Reposition the wiring compartment cover and secure its
they clamp onto the cord. Tighten the clamp screws so the screws. The dryer or range is ready for use.
cord is held securely but the clamp is not so tight that the
cord is deformed.

COMMON WIRING PROJECTS 197

 Adding an Outdoor
Receptacle

O utdoor receptacles can be few and far between.

The NEC requires only one receptacle on the
front and back of the house, and while builders can go
beyond the code requirement and install a few more,
many homes have only the bare minimum. This leaves
you with the chore and inconvenience of rolling out
long extension cords to reach holiday lights, corded Interior receptacles in ground‑floor living areas typically are
about 12 inches above the floor—a convenient height for
lawn tools, or outdoor equipment.
adding a receptacle on the exterior side of the wall.
But adding a receptacle to an exterior wall can
be a surprisingly simple job. Since the interior sides
of many house walls have a receptacle every 12 feet, must be weather-resistant type (indicated by “WR”
at the most, there are plenty of places to tap into a stamped on the receptacle’s face) as well as tamper-
receptacle circuit to power an outdoor receptacle. resistant (indicated by a “TR” stamp).
The easiest way to do this is to go straight out from The outdoor electrical box can be recessed or
the indoor box, extending the circuit to an outdoor surface-mounted, depending on the box type. Surface-
box with a short length of NM cable. mounting requires a hole only for the new cable and
Outdoor receptacles can be 15-amp or 20-amp, clamp. This can greatly simplify the job when you’re
so most indoor receptacle circuits in living areas working with brick or stone siding. A recessed box
are suitable, provided the added receptacle doesn’t installs flush to the wall and needs a hole cut out for
overload the circuit. You cannot tap into a kitchen, the entire box. Recessing the box also means you can’t
bathroom, or laundry room receptacle circuit. Make go directly opposite the indoor box, since the wall
sure the new receptacle has the correct amperage cavity usually is not deep enough to accommodate
rating for the circuit; do not install a 20-amp two boxes back to back. The solution is to offset the
receptacle on a 15-amp circuit. boxes while staying within the same stud cavity.
Also make sure the new receptacle is GFCI Finally, the outdoor box needs a cover that’s
protected, which is required for all outdoor suitable for the location. Boxes that are protected
receptacles. You can accomplish this by simply using from direct exposure to snow and rain, such as from
a GFCI receptacle on the outdoor side. This will a porch or patio roof, can have a cover rated for damp
provide GFCI protection even if the circuit or indoor locations. Boxes that are exposed to moisture must
receptacle are not GFCI protected. The receptacle have an “in-use” cover rated for wet locations.

TOOLS & MATERIALS

Noncontact voltage tester Weatherproof exterior Exterior caulk Fish tape (as needed)
Screwdrivers receptacle box with cover Drill driver Wire strippers
3-foot length of 2-wire Cable clamp Long 1/4-inch drill bit Caulking gun
NM cable Corrosion-resistant screws 1-inch spade bit Wire connectors

198 THE COMPLETE GUIDE TO WIRING

 1 2
Shut off the power to the interior receptacle circuit. Remove Drill through a cable access hole in the box, using a long ¼-
the receptacle’s cover plate and test each receptacle terminal inch drill bit, drilling through the wall cavity and the sheathing
and all wires in the box to confirm the power is off, using a and siding on the exterior side of the wall. Angle the drill bit
noncontact voltage tester. Disconnect the wires and remove as desired, based on where you want to install the exterior
the receptacle. receptacle box.

Note: If the electrical box is small, this is a good time to

replace it with a larger, old work retrofit box (see pages 62
to 63).

3 4
Enlarge the hole on the exterior side of the wall, using a 1-inch Cut a 2‑foot length of 2‑wire NM cable; this must have the
spade bit (or as needed), drilling through the siding and same wire gauge as the cable of the receptacle circuit. Feed
sheathing to make room for the cable clamp. the cable through the hole in the interior box and out through
the exterior hole. If necessary, use a fish tape to pull the cable
Variation: To install a recessed box, trace the outline of the through (see page 40).
box body onto the wall, drill a 3⁄8‑inch hole at each corner
of the outline, then cut along the outline with a jigsaw (see
page 287).

COMMON WIRING PROJECTS 199

 5 6
Secure the cable to the exterior receptacle box with a cable Mount the exterior box to the wall siding, using corrosion-
clamp, leaving about 6 inches of cable extending from the resistant screws. If necessary, drill pilot holes for the screws to
front of the box. prevent splitting the siding.

Note: If the receptacle box is metal, connect two grounding

pigtails to the ground wire in the cable, using wire
connectors. Connect one of the pigtails to the ground screw
on the metal box.

7 8
Remove all but ½ inch of sheathing from the cable inside Install the box cover onto the front of the exterior box,
the box. Strip ¾ inch of insulation from each wire, using following the cover manufacturer’s instructions.
wire strippers. Connect the black (hot) wire to the HOT LINE
(brass) terminal of the GFCI receptacle. Connect the white
(neutral) wire to the WHITE LINE (silver) terminal and connect
the ground wire to the receptacle’s ground screw. Tuck the
wires into the box and mount the receptacle to the box with
the provided screws.

200 THE COMPLETE GUIDE TO WIRING

 9 10
Apply a neat bead of exterior caulk along the entire perimeter Cut a 6‑inch length from the leftover NM cable. Remove the
of the exterior box, creating a watertight seal between the box cable sheathing and strip both ends of the insulated wires to
and the siding. If desired, paint the caulk and box body (not create pigtails (see page 33). Trim the NM cable so it extends
the cover) to match the wall after the caulk cures completely. about 6 inches beyond the front of the interior box and
remove all but ½ inch of the cable sheathing. Connect the
pigtails and original circuit wires to the wires of the new cable,
using wire connectors.

11 12
Connect the pigtail wires to the interior receptacle: black (hot) Reinstall the cover plate on the interior receptacle. Restore
wire to the brass screw terminal, white (neutral) wire to the power to the circuit and test the GFCI for proper operations,
silver terminal, ground wire to the ground screw. Tuck the following the manufacturer’s instructions.
wires into the box and mount the receptacle to the box with
the original screws.

COMMON WIRING PROJECTS 201

 TOOLS & MATERIALS
Replacement light fixture Insulated screwdrivers

Ceiling Lights Wire stripper

Voltage tester
Wire connectors
Eye protection

C eiling fixtures don’t have any moving parts,

and their wiring is very simple, so, other than
changing bulbs, you’re likely to get decades of
fixture with one with separate spot lights, or you
can simply install a new fixture that matches the
room’s décor. Check the weight rating of the box to
trouble-free service from a fixture. This sounds like a which you will attach your fixture. Older boxes may
good thing, but it also means that the fixture probably not handle a heavy fixture. If you are unsure how
won’t fail and give you an excuse to update a room’s much weight the existing box can handle, consider
look with a new one. Fortunately you don’t need an changing the box. New light fixture boxes should
excuse. Upgrading a fixture is easy and can make a handle fixtures up to 50 pounds. Support the fixture
dramatic impact on a room. You can substantially independently from the box if the fixture weighs more
increase the light in a room by replacing a globe-style than 50 pounds.

Installing a new ceiling fixture can

provide more light to a space, not to
mention an aesthetic lift. It’s one of
the easiest upgrades you can do.

202 THE COMPLETE GUIDE TO WIRING

 Shown cutaway

Electrical box
Metal braces

Joist
Hot wire Brace

Grounding wire Wallboard

Neutral wire

Mounting strap

Grounding screw
If the new fixture is much heavier than the original fixture,
it will require additional bracing in the ceiling to support
the electrical box and the fixture. The manufacturer’s
Mounting instructions should specify the size and type of box. If the
screws ceiling is finished and there is no access from above, you can
remove the old box and use an adjustable remodeling brace
appropriate for your fixture (shown). The brace fits into a
small hole in the ceiling (inset). Once the bracing is in place,
Fixture base install a new electrical box specified for the new fixture.

Tab
Brass screw terminal

Socket (cutaway)

Shade

Lamp

No matter what a ceiling light fixture looks like on the outside, Inexpensive light fixtures have screw terminals mounted
they all attach in basically the same way. An electrical box in the directly to the backside of the fixture plate. Often, as seen
ceiling is fitted with a mounting strap, which holds the fixture in here, they have no grounding terminal. Some codes do not
place. The bare wire from the ceiling typically connects to the allow this type of fixture, but even if your hometown does
mounting strap. The two wires coming from the fixture connect approve them, it is a good idea to replace them with a better
to the black and the white wires from the ceiling. quality, safer fixture that is UL approved.

COMMON WIRING PROJECTS 203

 How to Replace a Ceiling Light

1 2

Shut off power to the ceiling light, and remove the shade or Remove the twist connectors from
diffuser. Loosen the mounting screws and carefully lower the the fixture wires or unscrew the
fixture, supporting it as you work (do not let light fixtures hang screw terminals and remove the
by their electrical wires). Use a voltage tester to make sure no white neutral wire and the black
power is reaching the connections. lead wire (inset).

3 4

Before you install the new fixture, check the ends of the wires Attach a mounting strap to the ceiling fixture box if there is
coming from the ceiling electrical box. They should be clean not one already present. Your new light may come equipped
and free of nicks or scorch marks. If they’re dirty or worn, clip with a strap; otherwise you can find one for purchase at any
off the stripped portion with your combination tool. Then strip hardware store.
away about ¾" of insulation from the end of each wire.

204 THE COMPLETE GUIDE TO WIRING

 5 6

Lift the new fixture up to the ceiling (you may want a helper for With the fixture supported by a ladder or a helper, join
this), and attach the bare copper ground wire from the power the white wire lead and the white fixture wire with a wire
supply cable to the grounding screw or clip on the mounting connector (often supplied with the fixture).
strap. Also attach the ground wire from the fixture to the
screw or clip.

7 8

Connect the black power supply wire to the black fixture wire Position the new fixture mounting plate over the box so the
with a wire connector. mounting screw holes align. Drive the screws until the fixture
is secure against the ceiling.

NOTE: Some fixtures are supported by a threaded rod or

nipple in the center that screws into a female threaded
opening in the mounting strap (inset).

COMMON WIRING PROJECTS 205

 Recessed Ceiling Lights
Rating symbol

R ecessed lights are versatile fixtures suited for a variety of situations.

Fixtures rated for outdoor use can also be installed in roof soffits and
overhangs for accent and security lighting. Recessed fixtures can also be
installed over showers or tubs if they are properly rated for damp or wet
locations, as required by code.
There are recessed lighting cans in all shapes and sizes for almost
every type of ceiling or cabinet. Cans are sold for unfinished ceilings (new
construction) or for finished ceilings (retrofit installation). Cans are also
rated as insulation compatible or for uninsulated ceilings. Be sure to use
the correct one for your ceiling to prevent creating a fire hazard. The 2015
International Residential Code requires that recessed lights installed in
unconditioned spaces (such as attics) be insulation contact (IC) rated, air
tight, and sealed to the drywall.
Rating symbol

TOOLS & MATERIALS Choose the proper type of recessed

light fixture for your project. There are
Recessed-lighting can Voltage tester Hack saw two types of fixtures: those rated for
for new construction Cable ripper Drywall saw installation within insulation (top), and
or remodeling those which must be kept at least 3"
Combination tool NM cable from insulation (bottom). Self-contained
and trim
Pliers Work gloves thermal switches shut off power if
Chalk line the unit gets too hot for its rating. A
Fish tape Eye protection recessed light fixture must be installed
at least ½" from combustible materials.

Recessed ceiling lights often are installed in series to

provide exacting control over the amount and direction of
light. Spacing the canisters in every other ceiling joist bay
is a common practice.

206 THE COMPLETE GUIDE TO WIRING

Recessed Materials

A
C
B

D
E

Recessed ceiling light housings come in many sizes and styles for various purposes and budgets. Some are sold with trim kits
(below) included. Some common types are new construction recessed housing (sold in economical multipacks) (A); airtight
recessed housings (for heated rooms below unheated ceilings) (B); shallow recessed housings (for rooms with 2 × 6 ceiling
joists) (C); small-aperture recessed housing (D); recessed slope ceiling housing (for vaulted ceilings) (E).

B C
A

D E F

Trim kits for recessed ceiling lights may be sold separately. Common types include open trim with reflective baffle (A); eyeball
trim (B); baffle trim (black) (C); shower light trim (D); open trim (E); baffle trim (full reflective) (F).

COMMON WIRING PROJECTS 207

 How to Install Recessed Ceiling Lights

1 2
Mark the location for the light canister. If you are installing Install the housing for the recessed fixture. Housings for
multiple lights, measure out from the wall at the start and new construction (or remodeling installations where the
end of the run, and connect them with a chalkline snapped installation area is fully accessible from either above or below)
parallel to the wall. If the ceiling is finished with a surface have integral hanger bars that you attach to each joist of the
(drywall or plaster), see next page. joist bay.

3 4
Run electric cable from the switch to each canister location. Run the cables into the electrical boxes attached to the
Multiple lights are generally installed in series so there is no canister housings. You’ll need to remove knockouts first and
need to make pigtail connections in the individual boxes. make sure to secure the cable with a wire staple within 8" of
Make sure to leave enough extra cable at each location to the entry point to the box.
feed the wire into the housing and make the connection.

208 THE COMPLETE GUIDE TO WIRING

 5 6

Connect the circuit wires to the fixture wires inside the Attach your trim kit of choice. Normally these are hung with
junction box. Twist the hot circuit wire together with the black torsion spring clips from notches or hooks inside the canister.
fixture wire, as well as the hot circuit wire running to other This should be done after the ceiling is installed and finished
fixtures further downline. Also connect the neutral white for new construction projects. With certain types of trim kits,
wires. Join the ground wires and pigtail them to the grounding such as eyeball trim, you’ll need to install the lightbulb before
screw or clip in the box. Finish the ceiling, as desired. the trim kit.

How to Connect a Recessed Fixture Can

in a Finished Ceiling

1 2 3

Make the hole for the can. Most fixtures Remove a knockout from the electrical Retrofit cans secure themselves in the
will include a template for sizing the box attached to the can. Thread the hole with spring-loaded clips. Install
hole. Fish 14/2 cable from the switch cable into the box; secure it with a the can in the ceiling by depressing the
location to the hole. Pull about 16" cable clamp. Remove sheathing and mounting clips so the can will fit into the
of cable out of the hole for making insulation. Connect the black fixture hole. Insert the can so that its edge is
the connection. wire to the black circuit wire, the white tight to the ceiling. Push the mounting
fixture wire to the white circuit wire, clips back out so they grip the drywall
and then connect the ground wire to and hold the fixture in place. Install the
the grounding screw or grounding wire trim piece.
attached to the box.

COMMON WIRING PROJECTS 209

 Track Lights

T rack lighting offers a beautiful and functional

way to increase the amount of light in a room
or simply to update its look. A variety of fixture and
TOOLS & MATERIALS
Drill/driver and bits Track light heads
lamp options let you control the shape, color, and
intensity of the light. Installing track lighting in place Wire stripper Prewired track
of an existing ceiling-mounted light fixture involves Screwdriver and fittings
basic wiring and hand-tool skills, but the connections Voltage tester Wire connector
are even easier to make than with traditional light Toggle bolts Ceiling box
fixtures. Once installed, the system is very easy to Eye protection
upgrade or expand in the future.

If you currently have a ceiling‑mounted light fixture that is not meeting your lighting needs, it’s simple to replace it with a
track-lighting fixture. With track lighting you can easily change the type and number of lights, their position on the track, and the
direction they aim. These fixtures come in many different styles, including short 3-ft. track systems with just one or two lights up
to 12-ft. systems with five or more lights.

210 THE COMPLETE GUIDE TO WIRING

 How to Install Track Lighting

1 2

Shut off power to the circuit at the service panel. Remove the Test the fixture wires with a voltage tester to make sure the
fixture globe and lightbulbs, then remove the fixture mounting circuit is dead. Support the fixture from below while you
screws. Carefully pull the fixture away from the ceiling without work—never allow a light fixture to hang by its electrical wires
touching any wires. alone. Remove the wire connectors and pull the wires apart.
Remove the old light fixture.

3 4

Attach the mounting strap for the new track light to the old Cut the track section to length, if necessary, using a
ceiling box. If the mounting strap has a hole in the center, hacksaw. Deburr the cut end with a metal file. If you are
thread the circuit wires through the hole before screwing the installing multiple sections of track, assemble the sections
strap to the box. The green or bare copper ground from the with the correct connector fittings (sold separately from
circuit should be attached to the grounding screw or clip on your kit). You can also purchase T-fittings or L-fittings
the strap or box. (inset photo) if you wish to install tracks in either of
these configurations. (continued)

COMMON WIRING PROJECTS 211

 5 6

Position the track section in the mounting saddle on the Insert the bolt from a toggle bolt or molly bolt into each
mounting strap and hold it temporarily in place in the location predrilled screw location and twist the toggle or molly back
where it will be installed. The track section will have predrilled onto the free end. These types of hardware have greater
mounting holes in the back. Draw a marking point on the holding power than anchor sleeves. Drill a 5⁄8"-diameter access
ceiling at each of these locations. If your track does not have hole in the ceiling at each of the mounting hole locations you
predrilled mounting holes, remove it and drill a 3⁄16" hole in the marked on the ceiling in step 5.
back every 16".

7 8

Insert the toggle or molly into the access hole far enough so it Hook up wires from the track’s power supply fitting to the
clears the top of the hole and the wings snap outward. Then circuit wires. Connect black to black and white to white. The
tighten each bolt so the track is snug against the ceiling. If the grounding wire from the power supply fitting can either be
mounting hole happens to fall over a ceiling joist, simply drive pigtailed to the circuit ground wire and connected to the
a drywall screw at that hole location. grounding screw or clip, or it can be twisted together with the
circuit grounding wire at the grounding terminal. Snap the
fitting into the track if you have not already done so.

212 THE COMPLETE GUIDE TO WIRING

 9 10

Dead end

Attach the protective cover that came with your kit to conceal Cap the open ends of the track with a dead end cap fitting.
the ceiling box and the electrical connections. Some covers These also may require a mounting screw. Leaving track ends
simply snap in place; others require a mounting screw. open is a safety violation.

11 12

Insert the light heads into the track by slipping the stem into Arrange the track light heads so their light falls in the manner
the track slot and then twisting it so the electrical contact you choose, and then depress the locking tab on each fixture
points on the head press against the electrified inner rails of to secure it in position. Restore power and test the lights.
the track slot. Tug lightly on the head to make sure it is secure
before releasing it.

COMMON WIRING PROJECTS 213

 the small-appliance receptacle circuits. By cutting an
access hole in the cabinet back, you can tie into the
receptacle box and run cable through the wall behind
the cabinets, up to the upper cabinet location, and
out the wall to supply the fixture that’s mounted to
the underside of the upper cabinet.
You can purchase undercabinet lights that are

Undercabinet Lights controlled by a wall switch, but most products

have an integral on/off switch so you can control
lights individually.
Extending a branch circuit or adding a new branch

H ardwired undercabinet lights illuminate the to install new receptacles, lights, or switches requires
kitchen countertop and sink areas that fall in the a permit. The electrical inspector may require that
shadow of ceiling lights. Most of these light fixtures, you install arc-fault protection on the entire circuit.
which are often called strip lights, utilize LED or Check with the electrical inspector before starting
fluorescent bulbs that are more energy efficient. such projects.
If you are doing a kitchen remodel with all-new
cabinets, run the new light circuit wiring before the
cabinets are installed. For a retrofit, you’ll need to TOOLS & MATERIALS
find an available power source to tie into. Options
for this do not include the dedicated 20-amp small- Voltage tester Undercabinet lighting kit
appliance receptacle circuits that are required in Utility knife 14/2 NM cable
kitchens. The best bet is to run new circuit wire from Drywall saw Wire connectors
a close-by ceiling light switch box, but this will mean Hammer Switch box
cutting into the walls to run cable. Another option is
to locate a receptacle that’s on the opposite side of a Screwdriver Switch
shared wall, preferably next to a location where a base Drill and hole saw Eye protection
cabinet is installed in the kitchen. This room should Jigsaw Hardboard panel adhesive
not be a breakfast room, dining, room, pantry, or Wire stripper
similar area, because these rooms are also served by

Undercabinet lights provide directed task lighting that bring sinks and countertop work surfaces out from the shadows.
Hardwired lights may be controlled either by a wall switch or an onboard on/off switch located on the fixture.

NOTE: Do not supply power for lights from a small‑appliance circuit.

214 THE COMPLETE GUIDE TO WIRING

 How to Install a Hardwired Undercabinet Light

Circuit with extra

capacity

Adjoining room, not

a breakfast or dining
room, or pantry

Kitchen

2
Wall shown cutaway

Look in the adjoining room for a usable power source in Cut a hole in the base cabinet back panel to get access to
the form of a receptacle that has a box located in the wall the wall behind it in roughly the area where you know the
behind your base cabinets. Unlike the small-appliance circuit next-door receptacle to be. Use a keyhole saw or drywall saw
with outlets in your backsplash area, these typically are not and make very shallow cuts until you have positively identified
dedicated circuits (which can’t be expanded). Make sure the locations of the electrical box and cables. Then finish the
that the receptacle’s circuit has enough capacity to support cuts with a jigsaw.
another load. Shut the power to the receptacle off at the main
panel and test for power.

4
Drill an access hole into the kitchen wall for the cable that will Cut a small access hole (4" × 4" or so) in the back panel
feed the undercabinet light. A ½"-diameter hole should be of the base cabinet directly below the undercabinet
about the right size if you are using 12-ga. or 14-ga. sheathed light location.
NM cable. (continued)

COMMON WIRING PROJECTS 215

 5 6

Feed cable into the access hole at the light location until the Feed the cable into a piece of flexible conduit that’s long enough
end reaches the access hole below. Don’t cut the cable yet. to reach between the two access holes in the base cabinets.
Reach into the access hole and feel around for the free cable Attach a connector to each end of the conduit to protect the
end, and then pull it out through the access hole once you’ve cable sheathing from the sharp edges of the cut metal.
found it. Cut the cable, making sure to leave plenty of extra
on both ends. TIP: To make patching the cabinet back easier, drill a new
access hole for the cable near the square access hole.

Protect cable in notch by installing

nail plates, as on page 209.

7 VARIATION: If you are installing more than one

undercabinet light, run cable down from each installation
Hang the conduit with hanger straps attached to the base point as you did for the first light. Mount an electrical
cabinet frame or back panel, drilling holes in the side walls of junction box to the cabinet back near the receptacle
the cabinet where necessary to thread the conduit through. providing the power. Run the power cables from each light
On back panels, use small screws to hang the straps instead through flexible conduit and make connections inside
of brads or nails. Support the conduit near both the entrance the junction box. Be sure to attach the junction box cover
and the exit holes (the conduit should extend past the back once the connections are made.
panels by a couple of inches).

216 THE COMPLETE GUIDE TO WIRING

 8 9

Remove the receptacle from the box you are tying into and Install the undercabinet light. Some models have a
insert the new circuit cable into one of the knockouts using removable diffuser that allows access to the fixture wires,
a cable clamp. Check a wire capacity chart (see page 26) and these should be screwed to the upper cabinet prior
to make sure the box is big enough for the new conductors. to making your wiring hookups. Other models need to be
Replace it with a larger box if necessary. Reinstall the connected to the circuit wires before installation. Check your
receptacle once the connections are made. manufacturer’s instructions.

10 11

Connect wires inside the light fixture according to the light Cut patches of hardboard and fit them over the access
manufacturer’s instructions. Make sure the incoming cable holes, overlapping the edges of the cutouts. Attach the
is stapled just before it enters the light box and that a cable access panels to the cabinet backs with screws or other
clamp is used at the knockout in the box to protect the cable. removable fasteners.
Restore power and test the light.

COMMON WIRING PROJECTS 217

 Vanity Lights

M any bathrooms have a single fixture positioned

above the vanity, but a light source in this
position casts shadows on the face and makes Vanity lights on the
grooming more difficult. Light fixtures on either side sides of the mirror
provide good lighting.
of the mirror is a better arrangement.
For a remodel, mark the mirror location, run cable,
and position boxes before drywall installation. You
can also retrofit by installing new boxes and drawing
power from the existing fixture.
The light sources should be at eye level; 66" is TOOLS & MATERIALS
typical. The size of your mirror and its location on
the wall may affect how far apart you can place the Drywall saw Screwdrivers Nail Plates
sconces, but 36" to 40" apart is a good guideline. Drill Hammer Vanity light
Extending a branch circuit or adding a new branch Combination Electrical boxes fixtures
to install new receptacles, lights, or switches requires tool and braces Wire connectors
a permit. Check with the electrical inspector before Voltage tester NM cable Eye protection
starting such projects.

How to Replace Vanity Lights in a Finished Bathroom

1 2

Turn off the power at the panel. Remove the old fixture from Mark the locations for the fixtures, and install new boxes. Install
the wall, and test to make sure that the power is off. Then the boxes about 66" above the floor and 18" to 20" from the
remove a strip of drywall from around the old fixture to centerline of the mirror (the mounting base of some fixtures
the first studs beyond the approximate location of the new is above or below the bulb, so adjust the height of the bracing
fixtures. Make the opening large enough that you have room accordingly). If the correct location is on or next to a stud, you
to route cable from the existing fixture to the boxes. can attach the box directly to the stud; otherwise you’ll need to
install blocking or use boxes with adjustable braces (shown).

218 THE COMPLETE GUIDE TO WIRING

 3

Nail plates

Open the side knockouts on the electrical box above the vanity. Then drill 5⁄8" holes in the centers of any studs between the old
fixture and the new ones. Run two NM cables from the new boxes for the fixtures to the box above the vanity. Protect the cable
with metal protector plates. Secure the cables with cable clamps, leaving 11" of extra cable for making the connection to the
new fixtures. Remove sheathing, and strip insulation from the ends of the wires.

4 5

Connect the white wires from the new cables to the white wire Install the fixture mounting braces on the boxes. Attach
from the old cable, and connect the black wires from the the fixtures by connecting the black circuit wire to the
new cables to the black wire from the old cable. Connect the black fixture wire and connecting the white circuit wire to
ground wires. Cover all open boxes, and then replace the the white fixture wire. Connect the ground wires. Position
drywall, leaving openings for the fixture and the old box. each fixture over each box, and attach with the mounting
(Cover the old box with a solid junction box cover plate and screws. Restore power and test the circuit.
leave it accessible.)

COMMON WIRING PROJECTS 219

 SUPPLIES YOU WILL NEED

Low‑voltage cable
lighting kit

Low-Voltage Cable Lights

T
Level
his unique fixture system is a mainstay of retail Voltage
and commercial lighting and is now becoming tester
common in homes. Low-voltage cable systems use
two parallel cables to suspend and provide electricity
to fixtures mounted anywhere on the cables. A 12-volt
transformer feeds low-voltage power to the cables.
The system’s ease of installation, flexibility, and Hammer Drill and
drill bits
the wide variety of individual lights available make it
perfect for all kinds of spaces. Low-voltage cable light
systems are ideal for retrofits and for situations where
Screwdrivers
surface-mounted track is undesirable or impossible
to install.

TOOLS & MATERIALS

Hammer Screwdrivers Low-voltage Voltage Tester
Level Drill and bits cable light kit Eye protection

Low‑voltage cable lights are low profile and easy to install, but they provide a surprising amount of light.

220 THE COMPLETE GUIDE TO WIRING

 How to Install Low-Voltage Cable Lighting

CABLE LIGHT KITS

1
Low-voltage cable lights typically are sold in kits that
contain the hanging lights, the low-voltage cable, and a
decorative transformer that can be ceiling mounted or
wall mounted.

Transformer

Cables

Lay out locations for the screw eyes that are used to suspend
the cables, which should be in a parallel line. The path should
lead the cables within a foot of the existing ceiling fixture box
that you are using to provide power.

2 3

Install wall anchors at the appointed locations for the screw Twist the screw eyes into the wall anchor sleeves, taking care
eyes that will suspend the cables. Plastic sleeve anchors are to make sure they are driven in equal amounts and are not
adequate in most cases. Drive the anchors into guide holes overdriven. Install a set of screw eyes the same distance apart
with a hammer. on each facing wall in the installation area. Cut two pieces of
low-voltage cable to span between screw eyes on facing walls.
Recommendations may vary—for the project shown here
the cable is cut 12" shorter than the distance between the
screw eyes. (continued)

COMMON WIRING PROJECTS 221

 4 5

Use the crimping hardware in your kit to form small loops at Attach the transformer crossbar to the electrical box containing
the ends of each cable. Slip the loops over the screw eyes the circuit leads. Shut off the power at the panel and test
on one end, and attach them to turnbuckles at the opposite for power, and then remove the old fixture, if you have not
ends. Slide the turnbuckles over the screw eyes and tighten already done so.
them until the cables are taut.

6 7

Make wiring connections for the transformer inside the Mount the transformer onto the electrical box according to the
electrical box. Make sure the transformer is supported while manufacturer’s instructions. The model shown here has a
you join the wires. Be sure to attach the grounding wires to separate chrome cover that is secured with a setscrew after
the grounding screw or clip in the box. the transformer is mounted to the crossbar.

222 THE COMPLETE GUIDE TO WIRING

 WALL‑MOUNT IT
8
Install the transformer in a wall location if there is a
more convenient power source or if you simply prefer
the appearance of the wall location.

Thread short lengths of cable into the openings on the screw

terminals on the transformer. Tighten the screws until the
pointed probe in each terminal pierces the cable sheathing
and makes contact with the wire inside. Do the same with
the other ends of the jumper cables using the provided
connector hardware.

9 10

Hang the light fixture holders from the cables, tightening the Insert the special low‑voltage bulbs into the fixture holders
screws in the hanger ends until their probes pierce the cable and secure them as instructed (here, we are tightening a
sheathing and make contact. It’s a good idea to hang all of setscrew). Turn on the power and test the lights, adjusting the
the fixtures and arrange them to your liking before you begin angles and directions of the bulbs.
tightening the screws and piercing the sheathing.

COMMON WIRING PROJECTS 223

 TOOLS & MATERIALS
Screwdriver Two- and three-wire
Combination tool 14-gauge NM cable
Fish tape Alarms
Drywall saw Wire connectors

Hardwired Smoke Wall or ceiling outlet boxes

Cable clamps (if boxes are
15-amp single-pole
AFCI breaker
Alarms & CO Alarms not self-clamping) Eye protection

some of each type.

S moke alarms and carbon monoxide (CO) alarms

are an essential safety component of any living
facility. All national fire-protection codes require
Heat alarms may
be installed in
addition to smoke
that new homes have a hardwired smoke alarm in alarms but may
every sleeping room and on every level of a residence, not be substituted
including basements and habitable attics. for them.
Three types of alarms exist that can alert you to Smoke alarms
a fire. Photoelectric alarms are better at detecting have a limited A little known fact about smoke
fires with lots of flames. Ionization alarms are slightly service life of alarms is that manufacturers
better at detecting smoldering fires. Heat alarms recommend periodic maintenance.
about 10 years.
Blowing compressed air into the
detect high temperature created by a fire. You should replace alarm where indicated by the
Many experts recommend installing smoke alarms after manufacturer can reduce the
photoelectric alarms instead of the more common 10 years regardless chance of a false alarm.
ionization alarms, or as an alternative, installing of whether the
alarm sounds when you press the test button. The
test button, especially on older alarms, may only test
A the sounding device, not the smoke detection system.
B
Hardwired alarms operate on your household
electrical current but have battery backups in case of a
power outage. On new homes, all smoke alarms must be
wired in a series so that every alarm sounds regardless of
the fire’s location. When wiring a series of alarms, be sure
to use alarms of the same brand to ensure compatibility.
Always check local codes before starting the job.
Smoke alarms installed on the ceiling should
be at least 4" from the wall. Smoke alarms installed
on the wall should be at least 4" and not more than
12" from the ceiling. As always, read and follow the
manufacturer’s instructions.
D C Smoke alarms and CO alarms are considered such
important safety devices that national codes require
updating these alarms to current code requirements
Smoke alarms and carbon monoxide (CO) alarms are required in during some types of remodeling projects. Enforcement
new construction. Hardwired CO alarms (A) are triggered by the of this requirement varies by jurisdiction, so check with
presence of carbon monoxide gas. Smoke alarms are available your building department before major remodeling.
in photoelectric and ionizing models. In ionizing detectors (B), a Extending a branch circuit or adding a new branch
small amount of current flows in an ionization chamber. When
to install new receptacles, lights, or switches requires
smoke enters the chamber, it interrupts the current, triggering
the alarm. Photoelectric alarms (C) rely on a beam of light, which a permit. The electrical inspector may require that you
when interrupted by smoke triggers an alarm. Heat alarms (D) install arc-fault protection on the entire circuit. Check
sound an alarm when they detect areas of high heat in the room. with the electrical inspector before starting such projects.

224 THE COMPLETE GUIDE TO WIRING

 How to Connect a Series of Hardwired Smoke Alarms
Pull 14/2 NM cable from the panel
into the first ceiling electrical box in
the smoke alarm series. Pull 14/3 NM
cable between the remaining alarm
Two‑wire cable outlet boxes. Use cable clamps to
Three‑wire cable to from service panel secure the cable in each outlet box.
next detector in series
Remove sheathing, and strip insulation
from wires.

2 3

Ensure power is off, and test for power. Wire the first alarm in Wire the remaining alarms in the series by connecting the
the series. Use a wire connector to connect the ground wires. like-colored wires in each outlet box. Always connect the red
Splice the black circuit wire with the alarm’s black lead and traveler wire to the odd-colored (in this case, red) alarm wire.
the black wire going to the next alarm in the series. Splice the This red traveler wire connects all the alarms together so that
white circuit wire with the alarm’s white wire and the white when one alarm sounds, all the alarms sound. If the alarm
(neutral) wire going to the next alarm in the series. Splice the doesn’t have a grounding wire, cap the ground with a wire
red traveler wire with the odd-colored alarm wire (in this case, connector. When all alarms are wired, install and connect the
also a red wire). new 15-amp AFCI breaker.

COMMON WIRING PROJECTS 225

 Landscape Lights

S ome landscape lighting manufacturers pitch their systems as security

products. If you keep the outside of your house well lit, the reasoning
goes, the thieves will turn elsewhere to find easier pickings. It’s possible
Low-voltage lights are
powered by a transformer that
steps 120-volt current down to
that the companies are right about this. But probably the stronger a safe 12 volts. Choosing the
arguments are for improved safety and appearance. location for the transformer is
It can’t be surprising that adding some light to the dark makes going an important part of planning.
places safer. This idea has been around for a long time—a very long time. You have two options: inside the
But the notion that you can improve the look of your house by adding house and outside the house.
some nightlights is more recent. In fact, decorating with exterior lights The outside installation is a little
became widespread only in the last 25 years, when low-voltage landscape easier, but the inside one is a little
lighting showed up. better, especially from a security
standpoint. Also take some time to
review your light placement. Once
you are happy with the plan, drive
a small stake where you want each
light to go.

TOOLS & MATERIALS

Drill/driver & bits
Hammer
Screwdrivers
Hacksaw
Spade
Low-voltage fixture
Wires
Transformer
Stakes
Hacksaw
Eye protection

Low‑voltage lights are safe to install and

use to beautify your outdoor spaces.
Unlike solar landscape lights, they are
powered by household electricity, so
they really can stay on all night if you
wish them to.

226 THE COMPLETE GUIDE TO WIRING

Parts of a Landscape Light System
Landscape lighting can be ordered
in kit form or as individual pieces.
F Kits include a few light heads, some
wire, and a transformer that changes
standard house current into low-voltage
power. If you want half a dozen lights
A
C G along the front walk, for example, then
the kit is a good idea. It’s cheaper,
very easy to install, and will last a long
I time unless the lights get run over by
a lawnmower.
B
D Typical low‑voltage outdoor lighting
systems consist of lens cap (A), lens
cap posts (B), upper reflector (C),
E lens (D), base/stake/cable connector
assembly (contains lower reflector) (E),
H K low-voltage cable (F), lens hood (G),
J
12-volt bulbs (H), cable connector caps
(I), control box containing transformer
and timer (J), and light sensor (K).

How to Modify Landscape Lights for Deck Installation

1 2
Specialty lights can cost a lot more than the standard plastic To install a modified light on a deck, bore a wire-clearance
spike-base lamps. Because of this, many people modify the hole through a deck board. Then feed the low-voltage wire
cheaper units to serve other purposes. To do this, first cut off through this hole, and attach the base to the deck with
the spike-base with a hacksaw. screws. The same technique can be used to install modified
units on planters or railings.

COMMON WIRING PROJECTS 227

 How to Install Low-Voltage Landscape Lights

2 Sensor

1 3
Install the transformer. In a garage, Drill a hole through the wall for the Attach the end of the low‑voltage wire to
mount it on a wall within 24" of a GFCI low-voltage cable and any sensors to the terminals on the transformer. Make
receptacle and at least 12" off the floor. pass through. If a circuit begins in a sure that both strands of wire are held
At an outdoor receptacle on a wall or high-traffic area, protect the cable by tightly by their terminal screws.
a post, mount the transformer on the running it through a short piece of
same post or an adjacent post at least PVC pipe or conduit, and then into the
12" off the ground and not more than shallow trench.
24" from the receptacle.

Note: The transformer must be

accessible

Connector box

4 6
Transformers usually have a simple Many low‑voltage light fixtures are Take apart the connector box and
mechanism that allows you to set times modular, consisting of a spiked base, insert the ends of the fixture wire and
for the lights to come ON and go OFF a riser tube, and a lamp. On these the low-voltage landscape cable into
automatically. Set these times before units, feed the wires and the wire it. Puncture the wire ends with the
hanging the transformer. connector from the light section down connector box leads. Reassemble
through the riser tube and into the base. the connector box.

228 THE COMPLETE GUIDE TO WIRING

 7 8 9
Feed the wire connector back into Assemble the fixture parts that cover Lay out the lights, with the wires
the light base, and attach it to the the bulb, including the lens cap and attached, in the pattern you have
lampholder according to directions. reflector or the cap. chosen. Then cut the sod between
Install the low-voltage lightbulb. fixtures with a spade. Push the blade
at least 6" deep and pry open a slot
Tip: Use LED lightbulbs to save by rocking the blade back and forth.
electricity.

10 11 12
Gently force the cable into the slot Firmly push the light into the slot in the Once the lamp is stabilized, tuck any
formed by the spade; don’t tear the sod. If the lamp doesn’t seat properly, extra wire into the slot using the paint
wire insulation. A paint stick (or a cedar pull it out and cut another slot at a right stick. No part of the wire should be
shingle) is a good tool for this job. Push angle to the first and try again. exposed when you are done with
the wire to the bottom of the slot. the job.

COMMON WIRING PROJECTS 229

 This rating is printed on the face of the transformer.
The location of your doorbell transformer is based on
local custom and the age of your home. It may be near
or attached to the service panel. It may be in the attic,
basement, crawlspace, or garage.
In most modern heating and air-conditioning
systems, the transformer serving the system is inside

Doorbells the furnace cabinet. In older systems, it may be

located near the furnace.
Occasionally a doorbell problem is caused by a
broken low-voltage wire somewhere in the system.

M ost doorbell problems are caused by loose You can test for wire breaks with a battery-operated
wire connections or worn-out switches. multitester. If the test indicates a break, new
Reconnecting loose wires or replacing a switch low-voltage wires must be installed between the
requires only a few minutes. Doorbell problems also transformer and the switches or between the switches
can occur if the chime unit becomes dirty or worn or and chime unit. Replacing low-voltage wires is not a
if the low-voltage transformer burns out. Both parts difficult job, but it can be time-consuming. You may
are easy to replace. Because most doorbells operate choose to have an electrician do this work.
at low voltage, the switches and the chime unit can
be serviced without turning off power to the system.
However, when replacing a transformer, always turn TOOLS & MATERIALS
off the power at the panel.
Continuity tester Rubbing alcohol
Some older houses have other low-voltage
transformers in addition to the doorbell transformer. Screwdriver Replacement doorbell
These transformers control heating and Multimeter switch (if needed)
air-conditioning thermostats or other low-voltage Needlenose pliers Masking tape
systems. When testing and repairing a doorbell system, Replacement chime unit
Cotton swab
it is important to identify the correct transformer. A (if needed)
doorbell transformer has a rating of 24 volts or less.

Circuit wires

Magnetic coil

Electrical box Plungers

(required)

Switch

Transformer
Low‑voltage doorbell
wires
Chimes

A home doorbell system is powered by a transformer that reduces 120-volts to 24 volts or less. Current flows from the
transformer to one or more push-button switches. When pushed, the switch activates a magnetic coil inside the chime unit,
causing a plunger to strike a musical tuning bar.

230 THE COMPLETE GUIDE TO WIRING

 How to Test a Nonfunctional Doorbell System

1 2 3
Remove the mounting screws holding Carefully pull the switch away from Inspect wire connections on the switch.
the doorbell switch to the siding. the wall. If wires are loose, reconnect them to the
screw terminals. Test the doorbell by
pressing the button. If the doorbell still
does not work, disconnect the switch
and test it with a continuity tester.

4 5 6

Transformer

Attach the clip of a continuity tester to Twist the doorbell switch wires together Locate the doorbell transformer. If it’s
one screw terminal and touch the probe temporarily to test the other parts of the not near the service panel, look in the
to the other screw terminal. Press the doorbell system. garage, crawlspace, and attic.
switch button. The tester should glow. If
not, then the switch is faulty and must
be replaced. (continued)

COMMON WIRING PROJECTS 231

 7 8 9

Identify the doorbell transformer by Reattach the cover plate. Inspect Touch the probes of the multimeter
reading its voltage rating. Doorbell the low-voltage wire connections, to the low-voltage screw terminals
transformers have a voltage rating of and reconnect any loose wires using on the transformer. If the transformer is
24 volts or less. Turn off power to the needlenose pliers or a screwdriver. Turn operating properly, the meter will detect
transformer at the panel. Remove the on power to the transformer at the main power within 2 volts of the transformer’s
cover on the electrical box, and test service panel. rating. If not, the transformer is faulty
the wires for power. Reconnect any and must be replaced.
loose wires. Replace taped connections
with wire connectors.

10 11 12

Test the chime unit. Remove the Test that the chime unit is receiving Clean the chime plungers (some
cover plate on the doorbell chime current. Touch probes of a multimeter models) with a cotton swab dipped in
unit. Inspect the low-voltage wire to screw terminals. If the multimeter rubbing alcohol. Reassemble doorbell
connections, and reconnect any detects power within 2 volts of the switches, and then test the system
loose wires. transformer rating, then the unit is by pushing one of the switches. If the
receiving proper current. If it detects doorbell still does not work, then
no power or very low power, there is the chime unit is faulty and must be
a break in the low-voltage wiring, and replaced (see page 233).
new wires must be installed.

232 THE COMPLETE GUIDE TO WIRING

 How to Replace a Doorbell Switch

1 2 3

Remove the doorbell switch mounting Disconnect wires from the switch. Tape Purchase a new doorbell switch,
screws, and carefully pull the switch wires to the wall to prevent them from and connect the wires to the screw
away from the wall. slipping into the wall cavity. terminals on the new switch. (Wires are
interchangeable and can be connected
to either terminal.) Anchor the switch to
the wall.

How to Replace a Doorbell Chime Unit

1 2 3

Turn off power to the doorbell at the Purchase a new chime unit that Connect the low‑voltage wires to the
main panel. Remove the cover plate matches the voltage rating of the old screw terminals on the new chime unit.
from the old chime. Label the low- unit. Thread the low-voltage wires Attach the cover plate, and turn on the
voltage wires FRONT, REAR, or TRANS through the base of the new chime unit. power at the main service panel.
to identify their screw terminal locations. Attach the chime unit to the wall using
Disconnect the wires. Remove the old the mounting screws included with the
chime unit. installation kit.

COMMON WIRING PROJECTS 233

 Wireless Switches

S ometimes a light switch is just in the wrong

place, or it would be more convenient to have two
switches controlling a single fixture. Adding a second
Two other similar types of wireless switch kits
are also available. One allows you to control a
plugged-in lamp or appliance with a remote light
switch the conventional way generally requires hours switch. The second type allows you to control a
of work and big holes in walls. (Electricians call this conventional light fixture remotely, but instead of
a three-way switch installation.) Fortunately wireless replacing the switch, the receiver screws in below
switch kits are available to perform basically the same the lightbulb. This is particularly useful if you want
function for a fraction of the cost and effort. There is to control a pull-chain light from a wall switch.
a bit of real wiring involved here, but it’s not nearly
as complicated as the traditional method of adding a
three-way switch installation.
The kits work by replacing a conventional switch TOOLS & MATERIALS
with a unit that has a built-in radio frequency receiver
that will read a remote device mounted within a 50-foot Voltage tester Wireless switch
radius. The kits come with a remote, battery-powered Screwdrivers transmitter &
switch (it looks like a standard light switch) that you receiver/switch
Wire connectors
can attach to a wall with double-sided tape.

A wireless switch is a two-part

switching system: a wireless switch
with a battery-powered transmitter
can be attached to any wall surface;
an existing switch is then replaced
with a new switch containing a
receiver that is triggered by signals
from the wireless transmitter,
effectively creating a three-way
switch condition.

Wireless switch with transmitter

Switch with wireless receiver

234 THE COMPLETE GUIDE TO WIRING

 WIRELESS SWITCH PRODUCTS

Wireless lamp switch

Wireless wall
switch kit

Wireless
plug‑in switch

Wireless kits are available to let you switch lights on and The remote switch is a wireless transmitter that requires
off remotely in a variety of ways: at the switch, at the plug, a battery. The transmitter switch attaches to the wall with
or at the bulb socket. adhesive tape or velcro strips.

A receiver with a receptacle can be plugged into any A radio‑controlled light fixture can be threaded into the socket
receptacle to give it wireless functionality. The switch is of any existing light fixture so it can be turned on and off with
operated with a remote control transmitter. a remote control device.

COMMON WIRING PROJECTS 235

 How to Install a Wireless Wall Switch

Grounding
wire

2
Identify the lead wire. Carefully separate the power supply
wires (any color but white or green) in the switch box so they
1 are not contacting each other or any other surface. Restore
power and test each lead wire with a noncontact voltage tester
to identify which wire carries the power (the LINE) and which
Get rid of the old switch. Shut off power to the switch circuit, is headed for the fixture the switch controls (the LOAD). Shut
and then disconnect and remove the old switch. power back off, and then label the wires.

3
Connect the LINE wire to the LINE terminal or wire on the
switch. Connect the LOAD wire (or wires) to the LOAD
terminal or wire. The neutral whites (if present) and green
grounding wires should be twisted together with a connector.
The greens should be grounded to the grounding clip or
4
terminal in the box.
Once the wires are firmly connected, you can attach the switch
NOTE: Some switch boxes, such as the one above, are wired to the box. Tuck the new switch and wires neatly back into the
with NM2 cable that has two blacks and a green wire and box. Then drive the two long screws that are attached to
no white. the new switch into the two holes in the electrical box.

236 THE COMPLETE GUIDE TO WIRING

 5 6

Attach the cover plate to the new wireless switch. Turn the Install a new 9‑volt battery (or other type as required) in
power service back on, and test to make sure the switch the box, and connect it to the switch transmitter terminals.
operates normally. Remove the backing from the adhesive pads on the back of
the wireless switch transmitter box.

7 8

Stick the transmitter box to the wall at the desired location. Test the operation of both switches. Each switch should
The box should be no more than 50 ft. from the receiver successfully turn the light fixture on and off. You’ve
switch (see manufacturer’s instructions). The box should be just successfully created a three-way switch installation
at the same height (usually 48") as the other switch boxes. without running any new wires.

COMMON WIRING PROJECTS 237

 Baseboard Heaters

B aseboard heaters are a popular way to provide

additional heating for an existing room or
primary heat to a converted attic or basement.
You can remove existing baseboard and run new cable
in the space behind. Baseboard heaters (and other
heating equipment) get very hot and can ignite nearby
Extending a branch circuit or adding a new branch to combustible materials. Maintain the manufacturer’s
install new receptacles, lights, switches, or equipment recommended distance between the heater and
requires a permit. The electrical inspector may require materials such as curtains, blinds, and wood.
that you install arc-fault protection on the entire
circuit. Check with the electrical inspector before
starting such projects.
Heaters are generally wired on a dedicated 240-volt
TOOLS & MATERIALS
circuit controlled by a thermostat. Several heaters Drill/driver 240-thermostat
can be wired in parallel and controlled by a single (in-heater or in-wall)
Wire stripper
thermostat (see circuit map 15, page 157).
Cable ripper 12/2 NM cable
Baseboard heaters are generally surface-mounted
without boxes, so in a remodeling situation, you only Drywall saw Electrical tape
need to run cables before installing wallboard. Be sure Baseboard heater Basic wiring supplies
to mark cable locations on the floor before installing or heaters
drywall. Retrofit installations are also not difficult.

Baseboard heaters can provide primary or supplemental heat for existing rooms or additions. Install heaters with clear space
between the heater and the floor.

238 THE COMPLETE GUIDE TO WIRING

Baseboard Thermostats
Single‑pole Double‑pole In‑heater Wall‑mount
thermostat thermostat thermostat thermostat

Single‑pole and double‑pole thermostats work in a similar In‑heater and wall‑mount are the two types of baseboard
manner, but double-pole models are safer. The single-pole thermostats you can choose from. If you are installing multiple
model will open the circuit (causing shutoff) in only one leg heaters, a single wall-mount thermostat is more convenient.
of the power service. Double-pole models have two sets of Individual in-heater thermostats give you more zone control,
wires to open both legs, lessening the chance that a person which can result in energy savings.
servicing the heater will contact a live wire.

HOW MUCH HEATER DO YOU NEED?

Here is a simple calculation get a rough idea of the lineal 7. Add 20% if the space above is not well insulated:
feet of baseboard a room requires. For a more accurate
8. Add 10% if ceiling is more than 8 ft. high:
estimate, consult a professional.
9. Total of the baseline wattage plus all additions:
1. Measure the area of the room in square feet
(length × width): 10. Divide this number by 250 (the wattage produced per
2. Multiply the area by 10 to get the baseline minimum foot of standard baseboard heater):
wattage:
11. Round up to a whole number. This is the minimum
3. Add 5% for each newer window or 10% for each older number of feet of heater you need.
window:

4. Add 10% for each exterior wall in the room: NOTE: It is much better to have more feet of heater than
is required than fewer. Having more footage of heater
5. Add 10% for each exterior door:
does not consume more energy; it does allow the heaters
6. Add 10% if the space below is not insulated: to work more efficiently.

PLANNING TIPS FOR BASEBOARD HEATERS

• Baseboard heaters require a dedicated circuit. A 20-amp, 240-volt circuit of 12-gauge copper wire will power up to
16 ft. of heater.

• Do not install a heater beneath a wall receptacle. Cords hanging down from the receptacle are a fire hazard.

• Do not mount heaters directly on the floor. You should maintain at least 1" of clear space between the baseboard
heater and the floor covering.

• Installing heaters directly beneath windows is a good practice.

• Locate wall thermostats on interior walls only, and do not install directly above a heat source.

COMMON WIRING PROJECTS 239

 How to Install a 240-Volt Baseboard Heater

1 2

Clamp
screw

Wire
connection
box

At the heater locations, cut a small hole in the drywall 3" to Remove the cover on the wire connection box. Open a
4" above the floor. Pull 12/2 NM (or the wire gauge specified knockout for each cable that will enter the box, and then
by the heater manufacturer) cables through the first hole: feed the cables through the cable clamps and into the wire
one from the thermostat, the other to the next heater. Pull connection box. Attach the clamps to the wire connection
all the cables for subsequent heaters. Middle-of-run heaters box, and tighten the clamp screws until the cables are
will have two cables, while end-of-run heaters have only one gripped firmly.
cable. (See also circuit map 15, page 157.)

3 To next heater 4
To element

From
thermostat

Grounding
screw

Anchor the heater against wall about 1" off floor by driving Make connections to the heating element if the power wires
flathead screws through the back of the housing and into are coming from a thermostat or another heater controlled
studs. Strip away cable sheathing so at least ½" of sheathing by a thermostat. See the next page for other wiring schemes.
extends into the heater. Strip ¾" of insulation from each wire Connect the white circuit wires to one of the wire leads on
using a combination tool. the heater. Tag white wires with black tape to indicate they
are hot. Connect the black circuit wires to the other wire
lead. Connect a grounding pigtail to the green grounding
screw in the box, and then join all grounding wires with a wire
connector. Reattach the cover.

240 THE COMPLETE GUIDE TO WIRING

One heater with end‑cap thermostat.
Run both power leads (black plus
tagged neutral) into the connection box
at either end of the heater. If installing
a single-pole thermostat, connect one
power lead to one thermostat wire and
connect the other thermostat wire, to
one of the heater leads. Connect the
other hot LINE wire to the other heater
lead. If you are installing a double-pole
thermostat, make connections with
both legs of the power supply.

Multiple heaters. At the first heater, join

both hot wires from the thermostat to
the wires leading to the second heater
in line. Be sure to tag all white neutrals
hot. Twist copper ground wires together
and pigtail them to the grounding
screw in the baseboard heater junction
box. This parallel wiring configuration
ensures that power flow will not be
interrupted to the downstream heaters
if an upstream heater fails.

Wall‑mounted thermostat. If installing

a wall-mounted thermostat, the power
leads should enter the thermostat first
and then be wired to the individual
heaters singly or in series. Hookups at
the heater are made as shown in step
4. Be sure to tag the white neutral as
hot in the thermostat box as well as in
the heater box.

COMMON WIRING PROJECTS 241

 Wall Heaters

I nstalling a wall heater is an easy way to provide

supplemental heat to a converted attic or basement
without expanding an existing HVAC system.
Extending a branch circuit or adding a new branch to Wall heaters are an easy-to-install way to provide
install new receptacles, lights, switches, or equipment supplemental heat. Some models have built-in thermostats,
while others can be controlled by a remote thermostat.
requires a permit. The electrical inspector may require
that you install arc-fault protection on the entire
circuit. Check with the electrical inspector before
starting such projects.
TOOLS & MATERIALS
Wall heaters are easy to install during a remodel Drywall saw Screwdrivers
(most have a separate can assembly that you attach to
Voltage tester 12/2 NM cable
the framing before the drywall is installed). They can
also be retrofitted. Drill Wire connectors
Most models available at home centers use Fish tape Wall heater
120-volt current (shown below), but 240-volt models Combination tool Thermostat (optional)
are also available.

How to Install a 120-Volt Wall Heater in a Finished Wall

1 2

Make an opening in the wall for the heater. Use a stud finder Turn the power off, and test for power. Pull 12/2 NM (or the wire
to locate a stud in the area where you want to install the gauge specified by the heater manufacturer) cable from the
heater. Mark the opening for the heater according to the service panel to the wall opening. If the heater is controlled by
manufacturer’s guidelines so that one side of the heater sits a separate thermostat, pull cable to the thermostat, and then
flush with a stud. Pay attention to clearance requirements. run another cable from the thermostat to the heater location.
Cut the opening with a drywall saw. If the wall is open, install
the heater can before hanging drywall (inset).

242 THE COMPLETE GUIDE TO WIRING

 3 4 5

Disconnect and remove the motor Install the can in the opening. Secure Wire the heater. Connect the black hot
unit from the heater can. Remove a the cable with a clamp, leaving 8" circuit wire to one of the black heater
knockout from the can, and route the to 12" of cable exposed. Attach the leads. Connect the white neutral
cable into the can. can to the framing as directed by circuit wire to the neutral lead. Connect
the manufacturer. the grounds.

Secure the heater unit in the can VARIATION: Connect a thermostat to control a wall heater. Some wall heaters do
as directed by the manufacturer. not use built-in thermostats. Install a thermostat in the heater circuit before the
Reconnect the motor if necessary. wall heater, following the manufacturer’s installation instructions.
Attach the grill and thermostat knob
as directed. Connect the new circuit
breaker at the main panel.

COMMON WIRING PROJECTS 243

 controls the temperature, and a timer turns the
system off automatically.
The system shown in this project includes two
plastic mesh mats, each with its own power lead that
is wired directly to the thermostat. Radiant mats may
be installed over a plywood subfloor, but if you plan
to install floor tile, you should put down a base of

Underfloor Radiant cementboard first, and then install the mats on top of
the cementboard.

Heat Systems
A crucial part of installing this system is to use a
multimeter to perform several resistance checks to
make sure the heating wires have not been damaged
during shipping or installation.

F loor-warming systems require very little energy to Electrical service required for a floor-warming
run and are designed to heat ceramic tile floors system is based on size. A smaller system may
only; they generally are not used as sole heat sources connect to an existing circuit, but this may not be
for rooms. Extending a branch circuit or adding a new a bathroom receptacle circuit, and the system may
branch to install new receptacles, lights, switches, not draw more than 50 percent of the circuit current
or equipment requires a permit. Check with the capacity. A larger system will need a dedicated circuit;
electrical inspector before starting such projects. follow the manufacturer’s instructions. These systems
A typical floor-warming system consists of one should be on a GFCI-protected circuit.
or more thin mats containing electric resistance To order a floor-warming system, contact the
wires that heat up when energized, like an electric manufacturer or dealer (see Resources, page 333).
blanket. The mats are installed beneath the tile and In most cases, you can send them plans and they’ll
are hardwired to a 120-volt GFCI circuit. A thermostat custom-fit a system for your project area.

TOOLS & MATERIALS

Vacuum cleaner
Multimeter
Tape measure
Scissors
Router/rotary tool
Marker
Electric wire fault indicator (optional)
Hot glue gun
Radiant floor mats
12/2 NM cable
Trowel or rubber float
Conduit
Thinset mortar
Thermostat with sensor
Junction box(es)
Tile or stone floorcovering
Drill
Double-sided carpet tape
Cable clamps A radiant floor‑warming system employs electric heating mats that are covered with
floor tile to create a floor that’s cozy underfoot.

244 THE COMPLETE GUIDE TO WIRING

 INSTALLATION TIPS

Thermostat
Timer Dedicated circuit cable

Thermostat sensor wire

Electrical conduit

Power leads

Heating mats

Floor tile

Thinset mortar

Heating mat

Concrete or cementboard underlayment

A floor‑warming system requires a dedicated

GFCI circuit to power and control its heating
mats, thermostat, and timer.

• Each radiant mat must have a direct connection to the • Do not cut heating wire or damage heating
power lead from the thermostat, with the connection wire insulation.
made in a junction box in the wall cavity. Do not install
• The distance between wires in adjoining mats should
mats in series.
equal the distance between wire loops measured center
• Do not install radiant floor mats under shower areas. to center.

• Do not overlap mats or let them touch.

COMMON WIRING PROJECTS 245

 Installing a Radiant Floor-Warming System

Floor‑warming systems must be installed on a circuit with An electric wire fault indicator monitors each floor mat for
adequate amperage and a GFCI breaker. Smaller systems continuity during the installation process. If there is a break
may tie into an existing circuit, but larger ones need a in continuity (for example, if a wire is cut), an alarm sounds.
dedicated circuit. Follow local building and electrical codes If you choose not to use an indicator tool to monitor the mat,
that apply to your project. test for continuity frequently using a multimeter.

How to Install a Radiant Floor-Warming System

1 2
Install electrical boxes to house the thermostat and timer. In Drill access holes in the sole plate for the power leads that
most cases, the box should be located 60" above floor level. are preattached to the mats (they should be over 10 ft. long).
Use a 4"-deep × 4"-wide double-gang box for the thermostat/ The leads should be connected to a supply wire from the
timer control if your kit has an integral model. If your timer thermostat in a junction box located in a wall near the floor
and thermostat are separate, install a separate single box for and below the thermostat box. The access hole for each mat
the timer. should be located directly beneath the knockout for that cable
in the thermostat box. Drill through the sill plate vertically and
horizontally so the holes meet in an L-shape.

246 THE COMPLETE GUIDE TO WIRING

 4
Clean the floor surface thoroughly to get rid of any debris that
could potentially damage the wire mats. A vacuum cleaner
generally does a more effective job than a broom.

5
Test for resistance using a multimeter set to measure
ohms. This is a test you should make frequently during
the installation, along with checking for continuity.
If the resistance is off by more than 10% from the
theoretical resistance listing (see manufacturer’s chart
in installation instructions), contact a technical support
operator for the kit manufacturer. For example, the theoretical
resistance for the 1 × 50 ft. mat seen here is 19, so the ohms
reading should be between 17 and 21.

3
Run conduit from the electrical boxes to the sill plate. The line
for the supply cable should be ¾" conduit. If you are installing
multiple mats, the supply conduit should feed into a junction
box about 6" above the sill plate and then continue into the
6
¾" hole you drilled for the supply leads. The sensor wire
needs only ½" conduit that runs straight from the thermostat Finalize your mat layout plan. Most radiant floor warming
box via the thermostat. Unless you are tapping into an existing mat manufacturers will provide a layout plan for you at the
circuit, the mats should be powered by a dedicated 20-amp time of purchase, or they will give you access to an online
GFCI circuit of 12/2 NM cable run from your main service design tool so you can come up with your own plan. This
panel to the electrical box (this is for 120-volt mats—check is an important step to the success of your project, and the
your instruction manual for specific circuit recommendations). assistance is free. (continued)

COMMON WIRING PROJECTS 247

 7 8

Unroll the radiant mat or mats and allow them to settle. Finalize the mat layout, and then test the resistance again
Arrange the mat or mats according to the plan you created. using a multimeter. Also check for continuity in several
It’s okay to cut the plastic mesh so you can make curves different spots. If there is a problem with any of the mats,
or switchbacks, but do not cut the heating wire under any you should identify it and correct it before proceeding with
circumstances, even to shorten it. the mortar installation.

VARIATION: If your local codes require it, roll the mats

Run the thermostat sensor wire from the electrical box down out of the way, and cut a channel for the sensor and the
the ½" conduit raceway and out the access hole in the sill sensor wires into the floor or floor underlayment. For most
plate. Select the best location for the thermostat sensor, and floor materials, a spiral cutting tool does a quick and neat
mark the location onto the flooring. Also mark the locations of job of this task. Remove any debris.
the wires that connect to and lead from the sensor.

248 THE COMPLETE GUIDE TO WIRING

 11

10
Bond the mats to the floor. If the mats in your system have Cover the floor installation areas with a layer of thinset mortar
adhesive strips, peel off the adhesive backing and roll out that is thick enough to fully encapsulate all the wires and
the mats in the correct position, pressing them against the mats (usually around ¼" in thickness). Check the wires
floor to set the adhesive. If your mats have no adhesive, bind for continuity and resistance regularly, and stop working
them with strips of double-sided carpet tape. The thermostat immediately if there is a drop in resistance or a failure of
sensor and the power supply leads should be attached with continuity. Allow the mortar to dry overnight.
hot glue (inset photo) and run up into their respective holes in
the sill plate if you have not done this already. Test all mats for
resistance and continuity.

13

12 Connect the sensor wire and the power supply lead (from
the junction box) to the thermostat/timer according to the
manufacturer’s directions. Attach the device to the electrical
Connect the power supply leads from the mat or mats to the box, restore power, and test the system to make sure it works.
NM cable coming from the thermostat inside the junction Once you are convinced that it is operating properly, install
box near the sill. Power must be turned off. The power leads floor tiles and repair the wall surfaces.
should be cut so about 8" of wire feeds into the box. Be sure
to use cable clamps to protect the wires. Note: Enclose the junction box with a blank cover. Do not
cover it with drywall; it must remain accessible.

COMMON WIRING PROJECTS 249

 Ceiling Fans

C eiling fans are installed and wired like ceiling

fixtures. They always require heavy-duty bracing
and electrical boxes rated for ceiling fans.
Because ceiling fans generally weigh more than
ceiling lights and the motion of the blade creates
more stress, it is very important that the ceiling box
Most standard ceiling fans work with a wall switch is securely mounted and is rated for ceiling fans.
functioning as master power for the unit. Pull chains Ceiling boxes rated for ceiling fans are marked with
attached to the unit control the fan and lights. In the phrase “For ceiling fan support.” If your existing
these installations, it’s fairly simple to replace an ceiling box is not fan-rated, replace it with one that
existing ceiling fixture with a fan and light. is. And be sure to inspect the manner in which the
If you will be installing a new circuit for the fan, box is mounted to make sure it is strong enough
use three-wire cable so both the light and the motor (see page 252).
can be controlled by wall switches (see circuit maps Installation varies from fan to fan, so be sure to
30 and 31, page 165). follow the manufacturer’s instructions.

TOOLS & MATERIALS

Screwdriver
Combination tool
Pliers or adjustable wrench
Voltage tester
Hammer
Ceiling fan light kit
2 × 4 lumber or adjustable
ceiling fan crossbrace
1½" and 3" coarse-thread screws
Eye protection
Downrod (if needed)

A ceiling fan helps keep living spaces

cooler in the summer and warmer in
the winter. Replacing an overhead light
with a fan/light is an easy project with
big payback.

250 THE COMPLETE GUIDE TO WIRING

Ceiling Fan Types

Hook
Mounting
Mounting bracket bracket

Downrod
Canopy

Canopy

Hanging pin
Motor collar
Mounting screw
Motor

Fan motor

Fan blades

Fan
blade

Switch housing Fan

direction
Pull chain control Light
Bottom cap fixture

Bracket‑mounted ceiling fans are hung directly from a Downrod mounted ceiling fans are supported by a metal rod
mounting bracket that is attached to the ceiling box. that’s hung from the ceiling mounting bracket. The length of
A canopy conceals the motor and the connections. the rod determines the height of the fan. Downrod fans are
used in rooms with ceilings 8 ft. high or higher. You may need
to buy a longer downrod if you have a very high ceiling.

FANS THAT HEAT

The first generation of ceiling fans did one job: they spun
and moved air. As the technology advanced, light kits
were added to replace the light source that is lost when
a fan-only appliance is installed. Now, some ceiling fans
are manufactured with electric heating elements that can
produce up to 5,000 BTU of heat, comparable to a small
space heater. Located in the fan canopy, the ceramic heat
elements direct heat out the vents and force it down to
the living level in the room, along with the heated air that
naturally rises.

Fan-mounted heaters are relatively light duty, so they

generally do not require a dedicated circuit. In most cases,
you can supply power to the heater/fan with any 15-amp
room light circuit that has extra capacity.

COMMON WIRING PROJECTS 251

 Supporting Ceiling Boxes
Shown cutaway

Joist

Brace

Mounting bracket Drywall

Add a wood brace above the ceiling box if you have access Install an adjustable fan brace if the ceiling is closed and you
from above (as in an attic). Cut a 2 × 4 or deeper brace to fit don’t want to remove the drywall. Remove the old light and
and fasten it between the ceiling joists. Drive a couple of deck the electrical box, and then insert the fan brace into the box
screws through the ceiling box and into the brace. If the box opening (inset photo). Twist the brace housing to cause it to
is not fan rated, replace it with one that is. telescope outward. The brace should be centered over the
opening and at the right height so the ceiling box is flush with
the ceiling surface once it is hung from the brace.

Bracket-Mounted Fans

Direct‑mount fan units have a motor housing with a mounting Ball‑and‑socket fan units have a downrod, but instead of
tab that fits directly into a slot on the mounting bracket. Fans threading into the mounting bracket, the downrod has an
with this mounting approach are secure and easy to install attached ball that fits into a hanger “socket” in the mounting
but difficult to adjust. bracket. This installation allows the fan to move in the socket
and find its own level for quiet operation.

252 THE COMPLETE GUIDE TO WIRING

 How to Install Downrod Ceiling Fans

1 2

Canopy

Rod hanger pipe

Shut off the power to the circuit at the panel. Unscrew the Run the wires from the top of the fan motor through the
existing fixture and carefully pull it away from the ceiling. Test canopy and then through the rod hanger pipe. Slide the rod
for power with a voltage tester to confirm the power is off. hanger pipe through the canopy and attach the pipe to the
Disconnect and remove the old fixture. motor collar using the included hanging pin. Tighten the
mounting screws firmly.

3 4

Hanging pin
Light kit
housing

Hang the motor assembly by the hook on the mounting Attach the fan blades with the included hardware. Connect
bracket. Connect the wires according to manufacturer’s the wiring for the fan’s light fixture according to the
directions, using wire connectors to join the fixture wires to manufacturer’s directions. Tuck all wires into the switch
the circuit wires in the box. Gather the wires together and housing, and attach the fixture. Install lightbulbs. Restore
tuck them inside the fan canopy. Lift the canopy and attach it power and test the fan.
to the mounting bracket.

COMMON WIRING PROJECTS 253

 Remote-Control Ceiling Fan Retrofit

C eiling fan remote control switches offer an easy

way of controlling both the lighting and fan
function of your ceiling fan. They are commonly
The remote can save you the need to install another
switch and/or the need to pull another wire to your
ceiling fan. Many different remotes on the market
used when there are only a hot and neutral at the can be used with different manufacturer ceiling
fan location or where the ability to switch two fans, so you are not limited to the brand of fan you
different functions is not present in the wiring. are using.

TOOLS & MATERIALS

Ceiling fan remote kit Screwdrivers Needlenose pliers Voltage tester
Wire connectors Pliers Wire strippers Eye protection

A retrofit remote control kit lets

you take the hassle (and the pull
chains) out of operating just about
any ceiling fan and light.

254 THE COMPLETE GUIDE TO WIRING

 To power source
To power source

To fan

To light Common neutral

Remote control Receiver unit
Antenna

Parts of an aftermarket remote control kit for a ceiling fan usually include the remote control unit (some come with a cradle) and
the receiver unit. Your unit may come with color-coded wire connectors and mounting hardware as well.

From switch
(power source)
Ground

Box

Receiver
Wiring a remote control fan controller is
Antenna
pretty simple. The black and white feed
Common wires from the power source should be
To light connected to the black and white power
To fan input wires coming out the receiver.
The red wire from the receiver should
be connected to the red wire from
the fan light. The white neutral wire
from the fan light should be connected
to the common white wire coming out
of the receiver. The black wire from
the fan should be connected to the
black fan wire from the receiver. The
white neutral wire from the fan should
be connected to the common white
wire coming out of the receiver. The
green ground wire from the power
source should be pigtailed to
the grounding terminal in the
ceiling box.

COMMON WIRING PROJECTS 255

 How to Retrofit a Remote Control to a Ceiling Fan

1 2

Turn your fan on high speed and turn the lights on. Then, at Remove the fan blades, one at a time on opposite sides of one
the main service panel, shut off the power to the circuit that another, so as to not overweight a certain side, which could
supplies your ceiling fan. bend the shaft and create a wobble. There are generally two
vertically installed Phillips head #10 screws that hold the
blade bracket to the motor housing.

3 4
If a light kit was installed on the fan, remove it as well. First, If your fan has a downrod between the motor housing and the
remove the bulbs and any glass diffusers, and then remove ceiling, remove the canopy on the top of the pipe connected
the light kit itself. Usually you’ll find three horizontally installed to the mounting plate on the ceiling. You should find two to
#6 Phillips head screws attached to the pan directly below four horizontally installed #6 screws near the base of the
the motor housing. Unplug the light kit from the fan wires and canopy. Remove the screws, and slide the canopy down to
set aside. expose the wiring.

256 THE COMPLETE GUIDE TO WIRING

 5 6 7

Check all wires with a voltage tester to Disconnect the black, red or blue, Install the receiving unit of the remote
verify there is no power present. and white wires from the electrical fan kit. Connect the black and white
box wires. wires from the receiving unit input to
the black and the white wires coming
from the electrical box in the ceiling. If
a red wire was used originally to feed
the light portion of the fan, cap this wire
with a wire nut and fold it into the box.

Common neutral connection

8 9
Light
connection

Antenna

Fan connection

Connect the output of the receiving unit to the fan’s associated Reinstall the canopy, fan blades, and light kit. Restore power.
wiring: black wire to black wire, white wire to white wire, Install the batteries into the remote control sending unit, and
and blue wire to blue wire (or red to red, or red to blue). If a test to make sure the fan is spinning on all three modes: Low,
downrod was used to hang the fan, place the receiving unit Medium, and High. Test the light switch to verify the light
above the ball and flange portion of the mounting bracket. switch works as well. Disconnect and remove the pullchains.

COMMON WIRING PROJECTS 257

 kit should include an exhaust hose (duct), a vent
tailpiece, and an exterior terminal.
Three common places to terminate the exhaust
are the roof, a soffit, or a sidewall. The instructions in
this book are for a shingle roof covering. You should
have a roofer install the exhaust termination if you
have any other roofing material or if you are not

Bathroom Exhaust Fans comfortable walking on your roof.

A soffit exhaust involves routing the duct to a soffit
(roof overhang) where it is connected to a terminal
that directs the exhaust outside. While soffit exhausts

M ost exhaust fans are installed in the center of the are allowed, they are not recommended, because the
bathroom ceiling or over the toilet area. A fan moisture can be drawn back into the attic through the
installed over the tub or shower area must be rated soffit vents. Check with the exhaust fan manufacturer
for use in wet areas. You can usually wire a fan that for instructions about how to run and terminate the
just has a light fixture into a main bathroom lighting exhaust duct and to determine the required duct
circuit (but not into a dedicated bathroom receptacle diameter and maximum length.
circuit). Units with built‑in heat lamps or blowers To prevent moisture damage, always terminate
require separate circuits. Extending a branch circuit or the exhaust duct outside your home—never into
adding a new branch to install new receptacles, lights, your attic.
switches, or equipment requires a permit. Check with
the electrical inspector before starting such projects.
If the fan you choose doesn’t come with a
TOOLS & MATERIALS
mounting kit, purchase one separately. A mounting Drill NM cable (14/2, 14/3)
Jigsaw Cable clamp
Combination tool Hose clamps
Fan rating (cubic ft.
per minute)
Screwdrivers Pipe insulation
Caulk gun Roofing cement
Sone rating Reciprocating saw Self‑sealing roofing nails
Pry bar Shingles
Check the information label attached to each exhaust Screws Wire connectors
fan unit. The minimum rating is 50 CFM; larger baths
Double‑gang retrofit Switch and timer
may need up to 100 CFM. The sone rating refers to
quietness rated on a scale of 1 to 7; quieter is lower. electrical box Eye protection

Exhaust termination Rafter

Exhaust tailpiece

Duct insulation

Exhaust duct NM cable from

Roof sheathing power source
Ceiling joist

Insulation

Bathroom exhaust fans must be exhausted to the outdoors, either through the roof or through a wall. Three-inch-diameter flexible
duct is not allowed for bathroom exhaust fans. Four-inch-diameter flexible duct is allowed for up to 56 feet without bends for
50 cfm fans. Use fan manufacturer’s installation instructions for duct type and length.

258 THE COMPLETE GUIDE TO WIRING

 How to Install a Bathroom Exhaust Fan

1 2
VARIATION: For fans with heaters or
Position the fan unit against a ceiling Remove the grille from the fan unit, and light fixtures, some manufacturers
joist. Outline the fan onto the then position the unit against the joist recommend using 2× lumber to
ceiling surface. Remove the unit, drill with the edge recessed ¼" from the build dams between the ceiling
pilot holes at the corners of the outline, finished surface of the ceiling (so the joists to keep the insulation at least
and cut out the area with a jigsaw or grille can be flush mounted). Attach the 6" away from the fan unit.
drywall saw. unit to the joist using drywall screws.

3 Switch box location

4

5
Mark and cut an opening for a double- Strip 10" of sheathing from the ends of Strip 10" of sheathing from the end of
gang box on the wall next to the latch the cables, and then feed the cables the cable at the unit, and then attach
side of the bathroom door, and then run into a double-gang retrofit switch box a cable clamp to the cable. Insert the
a 14/3 NM cable from the switch cutout so at least ½" of sheathing extends into cable into the fan unit. From the inside
to the fan unit. Run a 14/2 NM cable the box. Clamp the cables in place. of the unit, screw a locknut onto the
from the power source to the cutout. Tighten the mounting screws until the threaded end of the clamp.
box is secure. (continued)

COMMON WIRING PROJECTS 259

 6 8

Exhaust
termination
flange

Exhaust tailpiece

7
Mark the exit location in the roof next Remove a section of shingles from Attach a hose clamp to the rafter next
to a rafter for the exhaust duct. Drill a around the cutout, leaving the to the roof cutout about 1" below the
pilot hole, and then saw through the roofing paper intact. Remove enough roof sheathing (top). Insert the exhaust
sheathing and roofing material with a shingles to create an exposed area tailpiece into the cutout and through the
reciprocating saw to make the cutout that is at least the size of the exhaust hose clamp, and then tighten the clamp
for the exhaust tailpiece. termination flange. screw (bottom).

9 10
Slide one end of the exhaust duct over the tailpiece, and Apply roofing cement to the bottom of the exhaust termination
slide the other end over the outlet on the fan unit. Slip hose flange, and then slide the termination over the tailpiece. Nail
clamps or straps around each end of the duct, and tighten the termination flange in place with self-sealing roofing nails,
the clamps. Wrap the exhaust duct with pipe insulation. and then patch in shingles around the cover.
Insulation prevents moist air inside the duct from condensing
and dripping down into the fan motor.

260 THE COMPLETE GUIDE TO WIRING

 11 12

Grounding wire

Single‑pole switch (light)

Device (fan) wires

Neutrals

Turn power off and test for power. Make the following wire Connect the light plug to the built-in receptacle on the wire
connections at the fan unit: the black circuit wire from the connection box. Attach the fan grille to the frame using the
timer to the wire lead for the fan motor; the red circuit wire mounting clips included with the fan kit.
from the single-pole switch (see step 14) to the wire lead
for the light fixture in the unit; the white neutral circuit wire NOTE: If you removed the wall and ceiling surfaces for
to the neutral wire lead; the circuit grounding wire to the the installation, install new surfaces before completing
grounding lead on the fan unit. Make all connections with this step.
wire connectors. Attach the cover plate over the unit when
the wiring is completed.

LOAD to fan motor Grounding wires

13 14
Neutrals

LOAD to fan light

CIRCUIT from electrical‑panel

power supply (line side)

Turn power off and test for power. At the switch box, add black pigtail wires to one Tuck the wires into the switch box,
screw terminal on the timer and to one screw terminal on the single-pole switch; and then attach the switch and timer
add a green grounding pigtail to the groundling screw on the switch. Make the to the box. Attach the cover plate and
following wire connections: the black circuit wire from the power source to the black timer dial. Turn on the power.
pigtail wires; the black circuit wire from the exhaust fan to the remaining screw on
the timer; the red circuit wire from the exhaust fan to the remaining screw on the
switch. Join the white wires with a wire connector. Join the grounding wires with a
green wire connector.

COMMON WIRING PROJECTS 261

 TOOLS & MATERIALS
Hammer Range hood
Jigsaw Galvanized sheet metal
Screwdrivers ducts and fittings
Drill/driver & bits Wire connectors

Range Hoods Utility knife

Circular saw
Sheet metal screws
Foil tape
Caulk gun Plastic roof cement
Caulk
R ange hoods do more than just get rid of cooking Exhaust exterior
odors. Their most important job is to reduce the termination Eye protection
amount of water vapor in the air that’s generated by
routine cooking. The pot of water that boils for 30
minutes before you remember to drop in the pasta If the range is on an interior wall, the preferred
adds a lot of water vapor into your house. Usually the route is usually from the top of the hood through the
results are innocent enough. But prolonged periods roof. It’s also possible to put the duct into the attic,
of high moisture can lead to mildew and other molds then across the ceiling (between two rafters or trusses)
that can stain your walls and ceilings and possibly and out through an overhanging soffit. Follow the
make family members sick. hood manufacturer’s instructions about the size and
The hardest part of adding a range hood is length of the duct. A duct that is too long or too small
installing the ductwork between the hood and the will not work well and may be a grease fire hazard.
outside of your house. Always use galvanized steel, Consult the local code and manufacturer's
copper, or stainless-steel ducts. Never use flexible installation requirements. You may need to power the
duct, including flexible metal duct. If the range is hood with a dedicated 20-amp circuit. If your range
located on an outside wall, the best choice is to hood includes a microwave oven, be sure to read the
run the duct from the back of the hood straight installation instructions, preferably before you buy the
through the wall. If you have wood siding, this job is microwave. You may need a different cabinet above
not difficult. But if you have brick or stone, plan on the range. Inspectors may not approve microwaves
spending several hours to cut this hole. that are too close to the range.

A range hood captures steam and airborne food particles and draws them directly out of your house through an exhaust duct.
For slide-in ranges, the hood usually is installed under a short cabinet that contains the ductwork connection.

262 THE COMPLETE GUIDE TO WIRING

Range Hoods

Wall Elbow fitting

Range hood
termination

Sheet
metal
duct

Wood panels
Liner

Cabinet‑mounted range hoods draw steam upward Wall‑mounted range hoods function in the same manner
and out of the house through a wall-mounted or as cabinet mounted, but they are not integrated into the
roof-mounted termination. kitchen cabinet system.

Blower unit

Downdraft exhaust pulls steam downward and exhausts it out Island exhausts hang down from ceiling-mounted ductwork
through a wall exhaust. While leaving the space above the and draw steam and odors up from stovetops that are
stovetop uncluttered, these exhausts are much less efficient installed in kitchen islands. They typically have a very
(in large part because steam naturally rises). contemporary appearance.

COMMON WIRING PROJECTS 263

 How to Install a Range Hood

1 2

Install the sheet metal duct in the wall first, and then cut a hole Make sure the circuit power is turned off at the service panel
in the back of the range hood cabinet and mount the cabinet and test for power. Then join the power cable wires to the lead
over the duct. Cut a hole in the bottom of the cabinet to match wires inside the range hood. Use wire connectors for this job.
the opening on the top of the hood. The range hood often
comes with templates to help you cut holes in the right place.

3 4

Get someone to help lift the range hood into place and hold it Run ductwork from the cabinet to the exhaust exit point. Use
there while you attach it. Drive two screws through both sides two 45° adjustable elbows to join the duct in the wall to the
and into the adjacent cabinets. If the hood is slightly small top of the range hood. Use sheet metal screws and foil tape to
for the opening, slip a shim between the hood and the walls, hold all parts together and keep them from moving. Connect
trying to keep the gaps even. the duct securely to the fan outlet, and connect all sections so
they do not leak. A leaky connection can allow grease-laden
air to collect on the wood and start a fire.

264 THE COMPLETE GUIDE TO WIRING

Exhaust Termination Locations

Wall termination: If the duct comes out through the sidewall Masonry wall termination: You can run ductwork out through
of the house, install a vertical termination hood. Make an exterior wall made of brick or stucco, but it is a lot of work.
sure to seal around the perimeter of the hood with exterior You need to cut an opening in the wall with a masonry saw or
caulk. Don’t locate the termination too close to a window, chip one with a cold chisel, and then attach the termination
or the fumes will circulate back into the home. Comply with hood with masonry nails.
the siding manufacturer's instructions for flashing these
wall terminations.

Soffit termination: If the duct goes through an overhang soffit, Roof termination: For ducts that pass through the roof, cut an
you’ll need a transition fitting to connect the round duct access hole through the roofing and sheathing, and then install
to a short piece of rectangular duct. Once these parts are a weatherproof cap on top of the duct and under the roofing
installed, add a protective grille to keep animals and insects shingles. Make a waterproof seal by caulking the cap with
from getting into the duct. Don’t locate the termination near plastic roof cement. If you don’t have much roofing experience,
a soffit ventilation opening; the fumes and moisture will be consult a roofing manual for some more information on
drawn back into the attic. this step. Have a roofer do this if you have a roof covering other
than shingles or if your roof is steep or high. Also see page 260.

COMMON WIRING PROJECTS 265

 switch. The switch is wired to selected essential circuits
in your house, allowing you to power lights, furnace
blowers, and other loads that can’t easily be run with
an extension cord. But perhaps the most important job
a transfer switch performs is to disconnect the utility
power. If the inactive utility power line is attached to the
service panel, “backfeed” of power from your generator
Backup Power Supply to the utility line can occur when the generator kicks
in. This condition could be fatal to line workers who are
trying to restore power. The potential for backfeed is
the main reason many municipalities insist that only a

I nstalling a backup generator is an invaluable way to

prepare your family for emergencies. The simplest
backup power system is a portable gas-powered
licensed electrician hook up a transfer switch. Most also
require a permit. Using a transfer switch not installed by
a professional may also void the warranty of the switch
generator and an extension cord or two. A big benefit and the generator.
of this approach is that you can run a refrigerator and a Automatic transfer switches turn on the generator
few worklights during a power outage with a generator and switch off the utility supply when they detect a
that can also be transported to remote job sites or on significant drop in line voltage. They may be installed
camping trips when it’s not doing emergency backup with portable generators, provided the generator is
duty. This is also the least expensive way to provide equipped with an electric starter.
some backup power for your home. You can purchase a Large standby generators that resemble central
generator at most home centers and be up and running air conditioners are the top of the line in backup power
in a matter of hours. If you take this approach, it is supply systems. Often fueled by home natural gas lines
critically important that you make certain any loads that offer a bottomless fuel source or in-yard propane
being run by your generator are disconnected from the tanks, standby generators are made in sizes with as
utility power source. much as 20 to 40 kilowatts of output—enough to supply
The next step up is to incorporate a manual transfer all of the power needs of a 5,000-square-foot home.
switch for your portable generator. Transfer switches are NEC requirements for generators include that the
permanently hardwired to your service panel. They are generator receptacles should be GFCI protected. The
mounted on either the interior or the exterior of your generator should be equipped with a means to shut
house between the generator and the service panel. it down in an emergency and render it incapable of
You provide a power feed from the generator into the restarting without a manual reset.

Generators have a range of uses. Large

hardwired models can provide instant
emergency power for a whole house.
Smaller models (below) are convenient
for occasional short-term backup as
well as job sites or camping trips.

266 THE COMPLETE GUIDE TO WIRING

Choosing a Backup Generator

A 2,000‑ to 5,000‑watt gas‑powered generator and a few A permanent transfer switch patches electricity from a large
extension cords can power lamps and an appliance or portable generator through to selected household circuits via
two during shorter-term power outages. Appliances must an inlet at your service panel (inset), allowing you to power
not be connected to household wiring and the generator hardwired fixtures and appliances with the generator.
simultaneously. Never plug a generator into an outlet. Never
operate a generator indoors. Run extension cords through a
garage door.

For full, on‑demand backup service, install a large standby generator wired to an automatic transfer panel. In the event of a
power outage, the household system instantly switches to the generator.

COMMON WIRING PROJECTS 267

 A Typical Backup System

Backup generators supply power to a manual

Portable backup
transfer switch that disconnects the house from
generator
the main service wires and routes power from the
generator through selected household circuits.

Service entry cables

Main
panel
Inlet
box
Manual
transfer
switch

surge of 10,000 watts). If the surge watts aren’t listed,

ask, or check the manual. Some generators can’t
Choosing a Generator develop many more surge watts than run watts; others
can produce twice as much surge as run wattage.
Choosing a generator for your home’s needs requires It’s not necessary to buy a generator large enough to
a few calculations. The chart below gives an estimate match the surge potential of all your circuits (you won’t
of the size of generator typically recommended for a be turning everything on simultaneously), but surge
house of a certain size. You can get a more accurate watts should factor in your purchasing decision. If you
number by adding up the power consumption (the will be operating the generator at or near capacity, it is
watts) of all the circuits or devices to be powered by also a wise practice to stagger startups for appliances.
a generator. It’s also important to keep in mind that, You will need a large amount of gasoline to power a
for most electrical appliances, the amount of power gasoline generator for more than a day or so. Gasoline
required at the moment you flip the ON switch is goes bad over time, so you will need to stock up on
greater than the number of watts required to keep gas before a long outage. Be sure to store gasoline
the device running. For instance, though an air well away from any living space. Portable generators
conditioner may run on 5,400 watts of power, it will powered by propane are available, and may be a better
require a surge of 7,200 watts at startup (the power choice for some. Propane can last in a tank for years.
range required to operate an appliance is usually
SIZE OF HOUSE RECOMMENDED GENERATOR SIZE
listed somewhere on the device itself). These two
(IN SQUARE FEET) (IN KILOWATTS)
numbers are called run watts (or Rated Load Amps,
RLA) and surge watts (or Locked Rotor Amps, LRA). Up to 2,700 5–11
Generators are typically sold according to run watts 2,701–3,700 14–16
(a 5,000-watt generator can sustain 5,000 watts). They 3,701–4,700 20
are also rated for a certain number of surge watts 4,701–7,000 42–47
(a 5,000-watt generator may be able to produce a

268 THE COMPLETE GUIDE TO WIRING

Types of Transfer Switches
When using a cord‑connected switch, consider mounting
an inlet box to the exterior wall. This will allow you
to connect a generator without running
a cord into the house.

Cord‑connected transfer switches (shown above) are hard-

wired to the service panel (in some cases they’re installed
after the service panel and operate only selected circuits).
These switches contain a male receptacle for a power supply
cord connected to the generator. Automatic transfer switches
(not shown) detect voltage drop-off in the main power line
and switch over to the emergency power source.

GENERATOR TIPS

If you’ll need to run sensitive electronics such as A generator that will output 240‑volt service is required
computers or home theater equipment, look for a generator to run most central air conditioners. If your generator has
with power inverter technology that dispenses “clean variable output (120/240), make sure the switch is set to
power” with a stable sine wave pattern. the correct output voltage.

COMMON WIRING PROJECTS 269

 Running & Maintaining a Backup System
Even with a fully automatic standby generator
system fueled by natural gas or propane, you
will need to conduct some regular maintenance
and testing to make sure all systems are ready in
the event of power loss. If you’re depending on a
portable generator and extension cords or a standby
generator with a manual transfer switch, you’ll also
need to know the correct sequence of steps to follow
in a power emergency. Switches and panels also
Pull‑cord starter
need to be tested on a regular basis, as directed in
your owner’s manual. And be sure that all switches
(both interior and exterior) are housed in an Smaller portable generators often use pull cords instead of
approved enclosure box. electric starters.

Anatomy of a Portable Backup Generator

Fuel tank

Built‑in GFCI

Voltage
selector

Built‑in circuit
breaker

AC power
outlets
Start switch

Engine

Oil dipstick

Portable generators use small gasoline engines to generate power. A built-in electronics panel sets current to AC or DC and the
correct voltage. Most models will also include a built-in circuit breaker to protect the generator from damage in the event it is
connected to too many loads. Better models include features such as built-in GFCI protection. Larger portable generators may
also feature electric starter motors and batteries for push-button starts.

270 THE COMPLETE GUIDE TO WIRING

Operating a Manual System During an Outage

Plug the generator in at the inlet Start the generator with the pull cord Flip the manual transfer switch. Begin
box. Make sure the other end of the or electric starter (if your generator turning on loads one at a time by
generator’s outlet cord is plugged into has one). Let the generator run for flipping breakers on, starting with the
the appropriate outlet on the generator several minutes before flipping the ones that power essential equipment.
(120-volt or 120/240-volt AC) and the transfer switch. Do not overload the generator or the
generator is switched to the appropriate switch, and do not run the generator
voltage setting. at or near full capacity for more than
30 minutes at a time.

Maintaining & Operating

an Automatic Standby Generator

If you choose to spend the money and install a

dedicated standby generator of 10,000 watts
or more and operate it through an automatic
transfer switch or panel, you won’t need to lift
a hand when your utility power goes out. The
system kicks in by itself. However, you should
follow the manufacturer’s instructions for testing
the system, changing the oil, and running the
motor periodically.

COMMON WIRING PROJECTS 271

 Installing a
Transfer Switch

A transfer switch is installed

next to the main service panel
to override the normal electrical
service with power from a backup
generator during a power outage.
Manual transfer switches require
an operator to change the power
source, while automatic switches
detect the loss of power, start the A manual transfer switch
backup generator, and switch connects emergency circuits in your main panel to a standby generator.
over to the backup power feed.
Because the amount of electricity
created by a backup generator is
not adequate to power all of the
TOOLS & MATERIALS
electrical circuits in your house, Voltage tester Cable ripper Wire connectors
you’ll need to designate a few (yellow)
Drill/driver Wire strippers
selected circuits to get backup
Screwdrivers Level Standby power
current (see page 272).
generator
Hammer Manual transfer switch
Note: This project requires a Wire cutters Screws
permit and inspection of all work.

One flip of a switch reassigns the power source for each critical circuit so your backup generator can keep your refrigerator,
freezer, and important lights running during a utility power outage.

272 THE COMPLETE GUIDE TO WIRING

 SELECTING BACKUP CIRCUITS
Before you purchase a backup generator, determine which loads you will want to power from your generator in the
event of a power loss. Generally you will want to power your refrigerator, freezer, and maybe a few lights. Add up the
running wattage ratings of the appliances you will power up to determine how large your backup generator needs to
be. Because the startup wattage of many appliances is higher than the running wattage, avoid starting all circuits at
the same time—it can cause an overload situation with your generator. Here are some approximate running wattage
guidelines (see pages 130–131 for more information on calculating electrical loads):

• Refrigerator: 750 watts

• Forced air furnace: 1,100 to 1,500 watts
• Incandescent lights: 60 watts per bulb (CFL and LED lights use less wattage)
• Sump pump: 800 to 1,000 watts
• Well pump: 2,000 to 5,000 watts
• Garage door opener: 550 to 1,100 watts
• Television: 300 watts

Add the wattage values of all the loads you want to power, and multiply the sum by 1.25. This will give you the minimum
wattage your generator must produce. Portable standby generators typically output 5,000 to 7,500 watts. Most larger,
stationary generators can output 10,000 to 20,000 watts (10 to 20 kilowatts).

How to Install a Manual Transfer Switch

Warning:
1 Do not 2
touch these
terminals
(lugs).

Turn off the main power breaker in your electrical service Determine which household circuits are critical for emergency
panel. CAUTION: The service wires and terminals (lugs) usage during a power outage. Typically this will include the
that feed the main breaker remain live even when the main refrigerator, freezer, furnace, and at least one light or small-
breaker is off. appliance circuit. (continued)

COMMON WIRING PROJECTS 273

 3 4
Match your critical circuits with circuit inlet on your prewired Select and remove a knockout at the bottom of the main
transfer switch. Try to balance the load as best you can in service panel box. Make sure to choose a knockout that is
the transfer switch: For example, if your refrigerator is on the sized to match the connector on the flexible conduit coming
leftmost switch circuit, connect your freezer to the circuit from the transfer switch.
farthest to the right. Double-pole (240-volt) circuits will require
two 120-volt circuit connections. Also make sure that 15-amp
and 20-amp circuits are not mismatched with one another.

5 6
Feed the wires from the transfer switch into the knockout hole, Secure the flexible conduit from the switch box to the main
taking care not to damage the insulation. You will note that service panel using a locknut and a bushing where required.
each wire is labeled according to which circuit in the switch
box it feeds.

274 THE COMPLETE GUIDE TO WIRING

 7 8

Attach the transfer switch box to the wall so the closer edge Remove the breaker for the first critical circuit from the main
is about 18" away from the center of the main service panel. service panel box, and disconnect the hot wire lead from the
Use whichever connectors make sense for your wall type. lug on the breaker.

9 10

Locate the red wire for the switch box circuit that corresponds Locate the black wire from the same transfer switch circuit,
to the circuit you’ve disconnected. Attach the red wire to the and twist it together with the old feed wire, using a yellow wire
breaker you’ve just removed, and then reinstall the breaker. connector. Tuck the wires neatly out of the way at the edges of
the box. Proceed to the next circuit, and repeat the process.
(continued)

COMMON WIRING PROJECTS 275

 11 12

If any of your critical circuits are 240‑volt circuits, attach the Once you have made all circuit connections, attach the
red leads from the two transfer switch circuits to the double- white neutral wire from the transfer switch to an opening in
pole breaker. The two circuits originating in the transfer switch the neutral terminal bar of the main service panel.
should be next to one another, and their switches should be
connected with a handle tie. If you have no 240-volt circuits,
you may remove the preattached handle tie and use the
circuits individually.

13 14

Attach the green ground wire from the transfer switch to an Begin testing the transfer switch by making sure all of the
open port on the grounding bar in your main service panel. switches on it are set to the LINE setting. The power should
This should complete the installation of the transfer switch. still be OFF at the main panel breakers.
Replace the cover on the service panel box, and make sure
to fill in the circuit map on your switch box.

276 THE COMPLETE GUIDE TO WIRING

 STANDBY GENERATORS

Make sure your standby generator is operating properly and has been installed professionally. See page 268 for information
on choosing a generator that is sized appropriately for your needs.

15 16
Before turning your generator on, attach the power cord from Flip each circuit switch on the transfer switch box to GEN, one
the generator to the switch box. Never attach or detach a at a time. Try to maintain balance by moving back and forth
generator cord with the generator running. Turn your standby from circuits on the left and right side. Do not turn all circuits
power generator on, and let it run for a minute or two. on at the same time. Observe the onboard wattage meters as
you engage each circuit, and try to keep the wattage levels in
balance. When you have completed testing the switch, turn
the switches back to LINE, and then shut off your generator.

COMMON WIRING PROJECTS 277

 shed, plus the wiring and installation of devices inside
the shed. To add a new breaker and make the final
circuit connections to your home’s main service panel,
see page 174.
First, determine how much current you will
need. For basic electrical needs, such as powering a
standard light fixture and small appliances or power
Outbuildings tools, a 120-volt, 20-amp circuit should be sufficient.
A small workshop may require one or two 120-volt,
20-amp circuits. If you need any 240-volt circuits or

N othing improves the convenience and usefulness more than two 120-volt, 20-amp circuits, you will need
of an outbuilding more than electrifying it. to install at least a 60-amp subpanel with appropriate
Running a new underground circuit from your feeder wires. Installing a subpanel in an outbuilding is
house to an outbuilding lets you add receptacles and similar to installing one inside your home, but there
light fixtures both inside the outbuilding and on its are some important differences.
exterior. If you run power to an outbuilding, you are You may use #12 copper wire for one 120-volt,
required to install at least one receptacle. 20-amp circuit. Use #10 copper wire for two 120-volt,
Adding one or two 120-volt circuits is not 20-amp circuits. Also, if the shed is more than 150 feet
complicated, but every aspect of the project is strictly
away from the house, you may need heavier-gauge
governed by local building codes. Therefore, once
cable to account for voltage drop.
you’ve mapped out the job and have a good idea of
what’s involved, visit your local building department Most importantly, don’t forget to call before you
to discuss your plans and obtain a permit for dig. Have all utility and service lines on your property
the work. marked even before you make serious project plans.
This project demonstrates standard techniques for This is critical for your safety of course, and it may
running a circuit cable from the house exterior to a affect where you can run the circuit cable.

Adding an electrical circuit to an outbuilding such as this greatly expands the activities the building will support and is also a
great benefit for home security.

278 THE COMPLETE GUIDE TO WIRING

 TOOLS & MATERIALS
Spray paint Silicone caulk and caulk gun Utility knife
Trenching shovel (4"-wide blade) Double-gang boxes, metal (2) UF two-wire cable (12 gauge)
4" metal junction box One exterior receptacle box THNN wire (12 gauge)
Metal L-fittings (2) and conduit (with cover) 20-amp GFCI circuit breaker
nipple for conduit One 20-amp weather-resistant Wire strippers
Wood screws receptacle
Pliers
Conduit with watertight threaded One 20-amp receptacle
Screwdrivers
and compression fittings Single-pole switches (2)
Wire connectors
Wrenches Interior ceiling light fixture and metal
Hand tamper
Hacksaw fixture box
Schedule 80 conduit
90° sweeps for conduit (2) Exterior motion-detector fixture and
plastic fixture box Eye protection
Plastic conduit bushings (2)
EMT metal conduit and fittings for
Pipe straps
inside the shed

Ceiling light
Security light

EMT conduit

Switches
Rigid conduit from junction box

L‑body
Weather‑resistant
receptacle
IMC or schedule EMT conduit
80 conduit
IMC or schedule
80 conduit

90° sweep UF cable

90° sweep

A basic outdoor circuit starts with a waterproof fitting at the house wall connected to a junction box inside. The underground
circuit cable—rated UF (underground feeder)—runs in a 12"-deep trench and is protected from exposure at both ends by metal
or PVC conduit. Inside the shed, standard NM cable runs through metal conduit to protect it from damage (not necessary if you
will be adding interior wallcoverings). All receptacles must have GFCI protection; this is provided by a GFCI circuit breaker.

COMMON WIRING PROJECTS 279

 How to Wire an Outbuilding

1 2
Identify the circuit’s exit point at the house and entry point From outside, drill a hole through the exterior wall and the
at the shed and mark them. Mark the path of the trench rim joist at the exit point for the cable (you’ll probably need
between the exit and entry points using spray paint. Make to install a bit extender or an extra-long bit in your drill).
the route as direct as possible. Dig the trench to the depth Make the hole just large enough to accommodate the L-body
required by local code (typically 12" deep for a GFCI- conduit fitting and conduit nipple.
protected circuit) using a narrow trenching shovel.

3 4
Assemble the conduit and junction box fittings that will From outside, seal the hole around the conduit with
penetrate the wall. Here, we attached a 12" piece of ¾" expandable spray foam or caulk, and then attach the free end
PVC conduit and a sweep to a metal junction box with a of the conduit to the back of a waterproof L-body fitting.
compression fitting and then inserted the conduit into the Mount the L-body fitting to the house exterior with the open
hole drilled in the rim joist. The junction box is attached to end facing downward.
the floor joist.

280 THE COMPLETE GUIDE TO WIRING

 5

6
Cut a length of PVC conduit to extend from the L-fitting down Inside the shed, drill a ¾"-diameter hole in the shed wall. On
into the trench using a hacksaw. Deburr the cut edges of the interior of the shed, mount a junction box with a knock-
the conduit. Secure the conduit to the L-fitting, and then out removed to allow the cable to enter through the hole.
attach a 90° sweep to the bottom end of the conduit using On the exterior side directly above the end of the UF trench,
compression fittings. Anchor the conduit to the wall with a mount an exterior-rated receptacle box with cover. The plan
corrosion-resistant pipe strap. (and your plan may differ) is to bring power into the shed
through the hole in the wall behind the exterior receptacle.

8
Run conduit from the exterior box down into the trench. Fasten Run UF cable from the house to the outbuilding. Feed one end
the conduit to the outbuilding with a strap. Add a 90° sweep of the UF circuit cable up through the sweep and conduit and
and bushing, as before. Secure the conduit to the box with an into the L-fitting at the house (the back or side of the fitting
offset fitting. Anchor the conduit with pipe straps, and seal the is removable to facilitate cabling). Run the cable through the
entry hole with caulk. wall and into the junction box, leaving at least 12" of extra
cable at the end. (continued)

COMMON WIRING PROJECTS 281

 9 10
Lay the UF cable into the trench, making sure it is not twisted Inside the outbuilding, install the remaining boxes for the other
and will not contact any sharp objects. Roll out the cable, and switches, receptacles, and lights. With the exception of plastic
then feed the other end of the cable up through the conduit receptacle boxes for exterior exposure, use metal boxes if you
and into the receptacle box in the shed, leaving 12" of slack. will be connecting the boxes with metal conduit.

11 12
Connect the electrical boxes with conduit and fittings. Cut a length of conduit to fit between the coupling and
Inside the outbuilding, you may use inexpensive steel the next box or fitting in the run. If necessary, drill holes
EMT to connect the receptacle, switch, and fixture boxes. for the conduit through the centers of the wall studs. Attach
Once you’ve planned your circuit routes, start by attaching the conduit to the fitting that you attached to the first box.
couplings to all of the boxes.

282 THE COMPLETE GUIDE TO WIRING

 13 14

THNN wire

If you are surface‑mounting the conduit or running it up or Measure to find how much wire you’ll need for each run, and
down next to wall studs, secure it with straps no more than cut pieces of THHN wire that are 1 or 2 feet longer than the
3 ft. apart. Use elbow fittings for 90° turns and setscrew measurements. Before making L-turns with the conduit, feed
couplings for joining straight lengths as needed. Make holes the wire through the first conduit run.
through the wall studs only as large as necessary to feed the
conduit through.

15 16
Feed the other ends of the wires into the next box or fitting in Once you’ve reached the next box in line, coil the ends of
line. It is much easier to feed wire into 45° and 90° elbows the wires and repeat the process with new wire for the next
if they have not been attached to the conduit yet. Continue run. Keep working until all of the wire is run and all of the
feeding wire into the conduit and fitting until you have conduit and fittings are installed and secured. If you are
reached the next box in line. running multiple feed wires into a single box, write the origin
or destination on a piece of masking tape and stick it to each
wire end. (continued)

COMMON WIRING PROJECTS 283

 17
Neutral wires

Hot
wires

Grounding
wires

Receptacle
grounding Box grounding
screw screw

VARIATION: Installing a GFCI breaker for the new circuit at

NOTE: Your code may require an the main service panel is the best way to protect the circuit
in‑use rated receptacle box cover and allows you to use regular receptacles in the building,
(see page 51). but an alternative that is allowed in many areas is to run
the service into a GFCI-protected receptacle and then wire
Make the wiring connections at the receptacles. Connect the the other devices on the circuit in series (see page 152).
receptacles with pigtails, including grounding pigtails for the If you use this approach, only the initial receptacle needs
receptacles and the metal boxes. Install the receptacles and to be a GFCI receptacle; however, the underground circuit
cover plates. cable will need to be at least 24" deep.

18 19

Run service from the last receptacle to the switch box for Install the light fixtures. For this shed, we installed a caged
the light fixture or fixtures. (If you anticipate a lot of load ceiling light inside the shed and a motion-detector security
on the circuit, you should probably run a separate circuit light on the exterior side (see pages 286–289).
for the lights). Twist the white neutral leads and grounding
leads together and cap them. Attach the black wires to the
appropriate switches. Install the switches and cover plate.

284 THE COMPLETE GUIDE TO WIRING

 20 21

Run NM cable from the electrical box in the house at the start At the service panel, feed the NM cable in through a cable
of the new circuit to the main service panel. Use cable staples clamp. Arrange for your final electrical inspection before
if you are running the cable in floor joist cavities. If the cable you install the breaker. Then attach the wires to a new GFCI
is mounted to the bottom of the floor joists or will be exposed, circuit breaker, and install the breaker in an empty slot. Label
run it through conduit. the new circuit on the circuit map.

Turn on the new circuit, and test all

of the receptacles and fixtures. If any of
22 the fixtures or receptacles is not getting
power, check the connections first, and
then test the receptacle or switch for
continuity with a multimeter. Backfill
the trench.

COMMON WIRING PROJECTS 285

 Motion-Sensing Floodlights

M ost houses and garages have floodlights on their

exteriors. You can easily upgrade these fixtures
so that they provide additional security by replacing
A motion‑sensing light fixture provides inexpensive and
effective protection against intruders. It has an infrared eye
that triggers the light fixture when a moving object crosses its
path. Choose a light fixture with a photo cell to prevent the
them with motion-sensing floodlights. Motion- light from turning on in daylight; an adjustable timer to control
sensing floods can be set up to detect motion in a how long the light stays on; and range control to adjust the
specific area—such as a walkway or driveway—and reach of the motion-sensor eye.
then cast light into that area. And there are few things
intruders like less than the spotlight. These lights
typically have timers that allow you to control how
long the light stays on and photosensors that prevent
the light from coming on during the day. Extending
a branch circuit or adding a new branch to install
new receptacles, lights, or switches requires a permit.
Check with the electrical inspector before starting
such projects.

TOOLS & MATERIALS

Voltage tester
Jigsaw
Fish tape
Screwdrivers
Wire cutter
Cable ripper
Wire stripper
An exterior floodlight with a motion
Caulk gun
sensor is an effective security
measure. Keep the motion sensor Motion-sensing floodlight fixture
adjusted to cover only the area you Old work (retrofit) electrical box
wish to secure—if the coverage
area is too large, the light will turn NM cable
on frequently. Wire connectors
Eye protection

286 THE COMPLETE GUIDE TO WIRING

 How to Install a New Exterior Fixture Box

1 2

On the outside of the house, make the cutout for the motion- Estimate the distance between the indoor switch box and
sensor light fixture. Outline the light fixture box on the wall, the outdoor motion-sensor box, and cut a length of NM
drill a pilot hole, and complete the cutout with a wallboard cable about 2 ft. longer than this distance. Use a fish
saw or jigsaw. tape to pull the cable from the switch box to the motion-
sensor box. See page 40 for tips on running cable through
finished walls.

3 4
Mounting screws

Mounting bracket

Retrofit box

Strip about 10" of outer insulation from the end of the cable Insert the box into the cutout opening, and tighten the
using a cable ripper. Open a knockout in the retrofit light mounting screws until the brackets draw the outside flange
fixture box with a screwdriver. Insert the cable into the box so firmly against the siding. Follow the siding manufacturer’s
that at least ¼" of outer sheathing reaches into the box. Apply instructions about flashing this wall pentration.
a heavy bead of silicone or polyurethane caulk to the flange of
the electrical box before attaching it to the wall.

COMMON WIRING PROJECTS 287

 How to Replace a Floodlight with a Motion-Sensor Light

1 2

Turn off power to the old fixture. To remove it, unscrew the Before you touch any wires, use a voltage tester to verify that
mounting screws on the part of the fixture attached to the the circuit is dead. With the light switch turned on, insert the
wall. There will probably be four of them. Carefully pull the tester’s probe into the electrical box and hold the probe within
fixture away from the wall, exposing the wires. Don’t touch ½" of the wires inside to confirm that there is no voltage.
the wires yet. Disconnect the wire connectors, and remove the old fixture.

3 4
Grounding clip

Examine the ends of the three wires coming from the box If the electrical box is nonmetallic and does has a metal
(one white, one black, and one bare copper). They should be grounding clip, connect the circuit ground wire to the clip.
clean and free of corrosion. If the ends are in poor condition, Otherwise, connect the ground wire to the fixture base (if it
clip them off and then strip ¾" of wire insulation with a has a grounding terminal), or connect the ground wire to the
combination tool. fixture’s ground lead, using a wire connector.

288 THE COMPLETE GUIDE TO WIRING

 5 6

Now you can attach the new fixture. Begin by sliding a Next, join the black wire from the box and the single black
rubber or foam gasket (usually provided with the fixture) wire from the fixture with a wire connector. You may see a
over the wires and onto the flange of the electrical box. Set couple of black wires and a red wire already joined on the
the new fixture on top of a ladder or have a helper hold it fixture. You can ignore these in your installation.
while you make the wiring connections. There may be as
many as three white wires coming from the fixture. Join all
white wires, including the feed wire from the house, using
a wire connector.

7 8
Neatly tuck all the wires into the box so they are behind the Test the fixture. You will still be able to turn it on and off with
gasket. Align the holes in the gasket with the holes in the box, the light switch inside. Flip the switch on and pass your hand
and then position the fixture over the gasket so its mounting in front of the motion sensor. The light should come on.
holes are also aligned with the gasket. Press the fixture Adjust the motion sensor to cover the traffic areas, and pivot
against the gasket, and drive the four mounting screws into the light head to illuminate the intended area.
the box. Install exterior-rated floodlights and restore power.

COMMON WIRING PROJECTS 289

Repair Projects

“R epair” and “wiring” are two words you don’t

see together too much anymore. In most cases
of an electrical failure, the repair is to replace the
failed device. But many repairs may be as simple as
reconnecting loose wires or replacing a bad socket.
The electrical items that most frequently require
actual repairs are light fixtures. If you include lamps
and cords in this category, you’ve pretty much covered
it. Most electrical failures result from poorly made
connections in the original installation. Exceptions
are switches, which tend to wear out over time and
require replacement, and ceiling fans. Ceiling fans are
unique in that, like switches, they contain moving
parts—and rapidly moving parts at that. Catching a
switch pull chain on a moving blade is the cause of
many ceiling fan problems, along with blades that
have fallen out of balance and have begun to wobble.
When replacing part of an electrical fixture, the
rule of thumb for finding the replacement part is to
remove the broken part and bring it with you to a
lighting or electrical supply store. Failing that, take
down the make and serial number of the fixture so the
clerk can look up part information for you.

In this chapter:
• Repairing Light Fixtures
• Repairing Chandeliers
• Repairing Ceiling Fans
• Repairing Fluorescent Lights
• Replacing Plugs & Cords
• Replacing a Lamp Socket

REPAIR PROJECTS 291

 Repairing Light Fixtures
Electrical box
Metal braces

L ight fixtures are attached permanently to ceilings or

walls. They include wall‑hung sconces, ceiling‑hung
globe fixtures, recessed light fixtures, and chandeliers.
Hot wire
Most light fixtures are easy to repair using basic tools
and inexpensive parts.
If a light fixture fails, always make sure the Grounding wire
lightbulb is screwed in tightly and is not burned out.
A faulty lightbulb is the most common cause of light Neutral wire
fixture failure. If the light fixture is controlled by a
wall switch, also check the switch as a possible source
Mounting strap
of problems.
Light fixtures can fail because the sockets or
Grounding screw
built‑in switches wear out. Some fixtures have sockets
and switches that can be removed for minor repairs.
These parts are held to the base of the fixture with
mounting screws or clips. Other fixtures have sockets
and switches that are joined permanently to the base.
If this type of fixture fails, purchase and install a new Mounting
light fixture. screws
Damage to light fixtures often occurs because
homeowners install lightbulbs with wattage ratings Fixture base

that are too high. Prevent overheating and light

fixture failures by using only lightbulbs that match the
wattage ratings printed on the fixtures.
Techniques for repairing fluorescent lights are
different from those for incandescent lights. Refer
to pages 302–307 to repair or replace a fluorescent Tab
Brass screw terminal
light fixture.
Socket (cutaway)

TOOLS & MATERIALS

Shade
Circuit tester Combination tool
Screwdriver Replacement parts,
Continuity tester as needed

In a typical incandescent light fixture, a black hot wire is connected to a brass screw
terminal on the socket. Power flows to a small tab at the bottom of the metal socket
and through a metal filament inside the bulb. The power heats the filament and
causes it to glow. The current then flows through the threaded portion of the socket
and through the white neutral wire back to the main service panel.

292 THE COMPLETE GUIDE TO WIRING

 Before 1959,
incandescent light
fixtures (shown
Wood blocking
cutaway) often were
mounted directly
to an electrical box
Electrical box or to plaster lath.
Electrical codes
now require that
Hot wire fixtures be attached
to mounting straps
that are anchored to
the electrical boxes.
Neutral wire If you have a light
fixture attached to
plaster lath, install an
approved electrical
box with a mounting
strap to support
the fixture.

Screw terminals
Mounting screws

PROBLEM REPAIR
Wall‑ or ceiling‑mounted fixture flickers or does not light. 1. Check for faulty lightbulb.
2. Check wall switch and replace, if needed.
3. Check for loose wire connections in electrical box.
4. Test socket and replace, if needed (pages 312–313).
5. Replace light fixture.
Built‑in switch on fixture does not work. 1. Check for faulty lightbulb.
2. Check for loose wire connections on switch.
3. Replace switch.
4. Replace light fixture.
Chandelier flickers or does not light. 1. Check for faulty lightbulb.
2. Check wall switch and replace, if needed.
3. Check for loose wire connections in electrical box.
4. Test sockets and fixture wires and replace, if needed.
Recessed fixture flickers or does not light. 1. Check for faulty lightbulb.
2. Check wall switch and replace, if needed.
3. Check for loose wire connections in electrical box.
4. Test fixture and replace, if needed.
5. Wait a few minutes. If light activates, fixture is overheating.
Remove insulation from around fixture.

REPAIR PROJECTS 293

 How to Remove a Light Fixture & Test a Socket

Grounding screw

1 2
Turn off the power to the light fixture at the main panel. Test for power with a voltage tester. The tester should not
Remove the lightbulb and any shade or globe, then remove glow. If it does, there is still power entering the box. Return to
the mounting screws holding the fixture base and the the panel and turn off power to the correct circuit.
electrical box or mounting strap. Carefully pull the fixture
base away from the box.

Metal tab

3 4
Disconnect the light fixture base by loosening the screw Adjust the metal tab at the bottom of the fixture socket by
terminals. If the fixture has wire leads instead of prying it up slightly with a small screwdriver. This adjustment
screw terminals, remove the light fixture base by unscrewing will improve the contact between the socket and the lightbulb.
the wire connectors.

Metal tab Neutral screw terminal

5 6

Hot screw terminal

Threaded portion of socket

Test the socket (shown cutaway) by attaching the clip of Attach the tester clip to the neutral screw terminal (or white
a continuity tester to the hot screw terminal (or black wire wire lead), and touch the probe to the threaded portion of
lead) and touching probe of the tester to the metal tab in the the socket. The tester should glow. If not, the socket is faulty
bottom of the socket. The tester should glow. If not, the socket and must be replaced. If the socket is permanently attached,
is faulty and must be replaced. replace the fixture.

294 THE COMPLETE GUIDE TO WIRING

 How to Replace a Socket

1 2

Remove the old light fixture. Remove the socket from the Purchase an identical replacement socket. Connect the white
fixture. The socket may be held by a screw, clip, or retaining wire to the silver screw terminal on the socket, and connect
ring. Disconnect wires attached to the socket. the black wire to the brass screw terminal. Attach the socket
to the fixture base, and reinstall the fixture.

How to Test & Replace a Built‑In Light Switch

Retaining ring

Switch
leads

1 2
Remove the light fixture. Unscrew the retaining ring holding Label the wires connected to the switch leads. Disconnect the
the switch. switch leads, and remove the switch.

3 4
Test the switch by attaching the clip of the continuity tester If the switch is faulty, purchase and install a duplicate switch.
to one of the switch leads and holding the tester probe to the Remount the light fixture, and turn on the power at
other lead. Operate the switch control. If the switch is good, the the main service panel.
tester will glow when the switch is in one position but not both.

REPAIR PROJECTS 295

 Support chains
Cover plate can be
lowered to provide
access
Fixture wires
through chain
to base
Socket wires run
Repairing Chandeliers through chandelier
arms to the sockets
Base
Arms

R epairing a chandelier requires special care.

Because chandeliers are heavy, it is a good idea
to work with a helper when removing a chandelier.
Support the fixture to prevent its weight from pulling
against the wires.
Chandeliers have two fixture wires that are
threaded through the support chain from the electrical Globe
box to the hollow base of the chandelier. The socket Cap can be removed
wires connect to the fixture wires inside this base.
Fixture wires are identified as hot and neutral. If you have a new chandelier, it may have a
Look closely for raised ribs on one of the wires. This grounding wire that runs through the support chain to
is the marked neutral wire that is connected to the the electrical box. If this wire is present, make sure it is
white circuit wire and white socket wire. The other connected to the grounding wires in the electrical box.
fixture wire is smooth or unmarked; it is hot and is
connected to the black wires.

How to Repair a Chandelier

Mounting
Mounting strap bolt
1 2 Mounting
strap

Cover plate
Threaded
nipple

Bolt cap nut

Retaining
nut

MOUNTING VARIATION: Some

chandeliers are supported only by
Label any lights that are not working Unscrew the retaining nut, and lower
the cover plate that is bolted to the
using masking tape. Turn off power the decorative coverplate away from the
electrical box mounting strap. These
to the fixture at the panel. Remove electrical box. Most chandeliers
types do not have a threaded nipple.
lightbulbs and all shades or globes. are supported by a threaded nipple
attached to a mounting strap.

296 THE COMPLETE GUIDE TO WIRING

 Grounding Circuit wires Threaded
screw nipple

Marked fixture wire

Unmarked fixture wire

3 4
Test for power with a voltage tester. The tester should not Disconnect fixture wires by removing the wire connectors.
glow. If it does, turn off power to the correct circuit at the Unscrew the threaded nipple and carefully place the
panel. chandelier on a flat surface.

Fixture wires

Socket wires

Cap

5 6
Remove the cap from the bottom of the chandelier, exposing Test the socket by attaching the clip of the continuity tester to
the wire connections inside the hollow base. Disconnect the the black socket wire and touching the probe to the tab in the
socket wires and fixture wires. socket. Repeat with the socket threads and the white socket
wire. If the tester does not glow, the socket must be replaced.

Socket wires Fixture wires

Chandelier arm

7 8
Remove a faulty socket by loosening any mounting screws or Test each fixture wire by attaching the clip of the continuity
clips and pulling the socket and socket wires out of the fixture tester to one end of the wire and touching the probe to other
arm. Purchase and install a new chandelier socket, threading end. If the tester does not glow, the wire must be replaced.
the socket wires through the fixture arm. Install new wires, if needed, then reassemble and rehang
the chandelier.

REPAIR PROJECTS 297

 Repairing Ceiling Fans

C eiling fans contain rapidly moving parts, making

them more susceptible to trouble than many
other electrical fixtures. Installation is a relatively Ceiling fans are subject to a great deal of vibration and
stress, so it’s not uncommon for switches and motors to fail.
simple matter, but repairing a ceiling fan can be
Minimize wear and tear by making sure blades are in balance
very frustrating. The most common problems you’ll so the fan doesn’t wobble.
encounter are balance and noise issues and switch
failure, usually precipitated by the pull chain breaking.
In most cases, both problems can be corrected TOOLS & MATERIALS
without removing the fan from the ceiling. But if you
have difficulty on ladders or simply don’t care to work Screwdriver Replacement switch
overhead, consider removing the fan when replacing Combination tool Voltage tester
the switch.

How to Troubleshoot Blade Wobble

OPTION: Fan blade wobble also may

be corrected using small weights
that are affixed to the tops of the
blades. For an easy DIY fix, you can
use electrical tape and washer and
1 2 some trial and error. You can also
purchase fan blade weight kits for a
couple of dollars. These kits include
Start by checking and tightening all If wobble persists, try switching around clips for marking the position of the
hardware used to attach the blades to two of the blades. Often this is all it weights as you relocate them as well
the mounting arms and the mounting takes to get the fan back into balance. as self‑adhesive weights that can be
arms to the motor. Hardware tends to If a blade is damaged or warped, stuck to the blade once you have
loosen over time, and this is frequently replace it. found the sweet spot.
the cause of wobble.

298 THE COMPLETE GUIDE TO WIRING

 How to Fix a Loose Wire Connection

2
A leading cause of fan failure is loose wire connections. To Once the canopy is lowered, you’ll see black, white, green,
inspect these connections, first shut off the power to the fan. copper, and possibly blue wires. Hold a voltage tester within
Remove the fan blades to gain access, and then remove the ½" of these wires with the wall switch that controls the fan in
canopy that covers the ceiling box and fan mounting bracket. the ON position. The black and blue wires should cause the
Most canopies are secured with screws on the outside shell. tester to beep if power is present.
Have a helper hold the fan body while you remove the screws
so it won’t fall.

4
When you have confirmed that there is no power, check all the
Shut off power to the fan’s circuit in the service
wire connections to make certain each is tight and making
panel, and test the wires by touching a voltage
good contact. You may be able to see that a connection has
tester to each one. If the tester beeps or lights up,
come apart and needs to be remade. But even if you see one
then the circuit is still live and is not safe to work
bad connection, check them all by gently tugging on the wire
on. When the tester does not beep or light up, the
connectors. If the wires pull out of the wire connector or the
circuit is dead and may be worked upon.
connection feels loose, unscrew the wire connector from the
wires. Turn the power back on and see if the problem has
been solved.

REPAIR PROJECTS 299

 How to Replace a Ceiling Fan Pull‑Chain Switch

1 2
Turn off the power at the panel. Use a screwdriver to remove Test the wires by touching a voltage tester to each one. If the
the three to four screws that secure the bottom cap on the fan tester beeps or lights up, then the circuit is still live and is not
switch housing. Lower the cap to expose the wires that supply safe to work on. When the tester does not beep or light up,
power to the pull‑chain switch. the circuit is dead and may be worked upon.

Switch

3 4
Locate the switch unit (the part that the pull chain used to be Attach a small piece of tape to each wire that enters the
attached to if it broke off); it’s probably made of plastic. You’ll switch, and write an identifying number on the tape. Start
need to replace the whole switch. Fan switches are connected at one side of the switch, and label the wires in the order
with three to eight wires, depending on the number of they’re attached.
speed settings.

300 THE COMPLETE GUIDE TO WIRING

 BUYER’S TIP
Here’s how to buy a new
switch. Bring the old switch to
the hardware store or home
center, and find an identical
new switch—one with the same
number and color of wires. It
should also attach to the fan
motor wires in the same way
(slots or screw terminals or
with integral wires and wire
connectors) and attach to the
fan in the same way. If you are
unable to locate an identical
switch, find the owner’s manual
for your ceiling fan and contact
5 the manufacturer. Or, find the
brand and model number of the
fan and order a switch from a
Disconnect the old switch wires, in most cases by cutting the wires off as close to ceiling fan dealer or electronics
the old switch as possible. Unscrew the retaining nut that secures the switch to the supply store.
switch housing.

6 7

Connect the new switch using the same wiring configuration

as on the old model. To make connections, first use a wire
stripper to strip ¾" of insulation from the ends of each of the
Remove the switch. There may be one or two
wires coming from the fan motor (the ones you cut in Step 5).
screws that hold it in place or it may be secured
Attach the wires to the new switch in the same order and
to the outside of the fan with a small knurled nut,
configuraion as they were attached to the old switch. Secure
which you can loosen with needle‑nose pliers.
the new switch in the housing, and make sure all wires are
Purchase an identical new switch.
tucked neatly inside. Reattach the bottom cap. Restore
power to the fan. Test all the fan’s speeds to make sure all
the connections are good.

REPAIR PROJECTS 301

 Repairing Fluorescent Lights
F luorescent lights are relatively trouble free and
use less energy than incandescent lights. A typical
fluorescent tube lasts about three years and produces
them. Fluorescent tubes contain a small amount
of hazardous mercury. Check with your local
environmental control agency or health department
two to four times as much light per watt as a standard for disposal guidelines.
incandescent lightbulb. Fluorescent light fixtures also can malfunction
The most frequent problem with a fluorescent if the sockets are cracked or worn. Inexpensive
light fixture is a worn‑out tube. If a fluorescent light replacement sockets are available at any hardware
fixture begins to flicker or does not light fully, remove store and can be installed in a few minutes.
and examine the tube. If the tube has bent or broken If a fixture does not work even after the tube and
pins or black discoloration near the ends, replace sockets have been serviced, the ballast probably
it. Light gray discoloration is normal in working is defective. Faulty ballasts may leak a black, oily
fluorescent tubes. When replacing an old tube, substance and can cause a fluorescent light fixture
read the wattage rating and the color temperature to make a loud humming sound. Although ballasts
rating printed on the tube, and buy a new tube with can be replaced, always check prices before buying
matching ratings. The color temperature rating a new ballast. It may be cheaper to purchase
is a measure of the color of the light produced by and install a new fluorescent fixture rather
the tube. Most people prefer a “warm” light in the than to replace the ballast in an old fluorescent
2,700K range. Never dispose of old tubes by breaking light fixture.

Ballast

Sockets

Cover plate

Pins

Fluorescent tubes

Diffuser

A fluorescent light works by directing electrical current through a special gas‑filled tube that glows when energized. A white
translucent diffuser protects the fluorescent tube and softens the light. A cover plate protects a special transformer, called a
ballast. The ballast regulates the flow of 120‑volt household current to the sockets. The sockets transfer power to metal pins that
extend into the tube.

302 THE COMPLETE GUIDE TO WIRING

 PROBLEM REPAIR

Tube flickers or lights partially. 1. Rotate tube to make sure it is seated properly in the sockets.
2. Replace tube and the starter (where present) if tube is discolored
or if pins are bent or broken.
3. Replace the ballast if replacement cost is reasonable.
Otherwise replace the entire fixture.

Tube does not light. 1. Check wall switch and replace, if needed.
2. Rotate the tube to make sure it is seated properly in sockets.
3. Replace tube and the starter (where present) if tube is discolored
or if pins are bent or broken.
4. Replace sockets if they are chipped or if tube does not seat properly.
5. Replace the ballast or the entire fixture.

Noticeable black substance around ballast. Replace ballast if replacement cost is reasonable.
Otherwise replace the entire fixture.

Fixture hums. Replace ballast if replacement cost is reasonable.

Otherwise replace the entire fixture.

TOOLS & MATERIALS

Screwdriver
Ratchet wrench
Combination tool
Voltage tester
Replacement tubes
Starters or ballast
(if needed)
Replacement fluorescent light
fixture (if needed)

Older fluorescent lights may have a

small cylindrical device, called a starter,
located near one of the sockets. When a
tube begins to flicker, replace both the
tube and the starter. Turn off the power,
and then remove the starter by pushing
it slightly and turning it counterclock‑
wise. Install a replacement that matches
the old starter.

REPAIR PROJECTS 303

 How to Replace a Fluorescent Tube

1 2

Turn off power to the light fixture at the switch. Remove the Remove the fluorescent tube by rotating it ¼ turn in either
diffuser to expose the fluorescent tube. direction and sliding the tube out of the sockets. Inspect the
pins at the end of the tube. Tubes with bent or broken pins
should be replaced.

3 4
Inspect the ends of the fluorescent tube for discoloration. The Install a new tube with the same wattage rating as the old tube.
new tube in good working order (top) shows no discoloration. Insert the tube so that pins slide fully into sockets, and then
The normal, working tube (middle) may have gray color. A twist tube ¼ turn in either direction until it is locked securely.
worn‑out tube (bottom) shows black discoloration. Reattach the diffuser, and turn on the power at the switch.

304 THE COMPLETE GUIDE TO WIRING

 How to Replace a Socket

1 2

Turn off the power at the service panel. Remove the diffuser, Remove the faulty socket from the fixture housing. Some
fluorescent tube, and the cover plate. Test for power with a sockets slide out, while others must be unscrewed.
voltage tester. If the tester glows, return to the panel and turn
off the correct circuit.

3 4

Disconnect wires attached to the socket. For push‑in fittings Purchase and install a new socket. If the socket has
(above), remove the wires by inserting a small screwdriver preattached wire leads, connect the leads to the ballast wires
into the release openings. Some sockets have screw terminal using wire connectors. Replace the cover plate and then the
connections, while others have preattached wires that must fluorescent tube, making sure that it seats properly. Replace
be cut before the socket can be removed. the diffuser. Restore power to the fixture at the panel and test.

REPAIR PROJECTS 305

 How to Replace a Ballast

1 2 3
Turn off the power at the service Remove the sockets from the fixture Disconnect the wires attached to the
panel, and then remove the diffuser, housing by sliding them out or by sockets by pushing a small screwdriver
fluorescent tube, and cover plate. removing the mounting screws and into the release openings (above), by
Test for power using a voltage tester. lifting the sockets out. loosening the screw terminals, or by
cutting wires to within 2" of sockets.

4 5 6
Remove the old ballast using a ratchet Install a new ballast that has the same Attach the ballast wires to the socket
wrench or screwdriver. Make sure to ratings as the old ballast. wires using wire connectors, screw
support the ballast so it does not fall. terminal connections, or push‑in
fittings. Reinstall the cover plate,
fluorescent tube, and diffuser. Turn on
power to the light fixture at the panel.

306 THE COMPLETE GUIDE TO WIRING

 How to Replace a Fluorescent Light Fixture

1 2 Cable clamp 3

Turn off power to the light fixture at Disconnect the insulated circuit wires Unscrew the fixture from the wall or
the panel. Remove the diffuser, tube, and the bare copper grounding wire ceiling and carefully remove it. Make
and cover plate. Test for power using a from the light fixture. Loosen the cable sure to support the fixture so it does
circuit tester. clamp holding the circuit wires. not fall.

4 5 6

Position the new fixture, threading the Connect the circuit wires to the fixture Attach the fixture cover plate, and then
circuit wires through the knockout wires using wire connectors. Follow the install the fluorescent tubes and attach
opening in the back of the fixture. wiring diagram included with the new the diffuser. Turn on power to the fixture
Screw the fixture in place so it is firmly fixture. Tighten the cable clamp holding at the panel and test.
anchored to framing members. the circuit wires.

REPAIR PROJECTS 307

 Faceplate

Grounded
round‑cord
Round‑cord plug
plug

Replacing Plugs & Cords

Flat‑cord plug

R eplace an electrical plug whenever you notice

bent or loose prongs, a cracked or damaged
casing, or a missing insulating faceplate. A damaged
Quick‑connect plug

plug poses a shock and fire hazard.

Replacement plugs are available in different
styles to match common appliance cords. Always
choose a replacement that is similar to the original Polarized
plug. Flat‑cord and quick‑connect plugs are used plug
with light‑duty appliances, such as lamps and radios. Underwriter’s knot
Round‑cord plugs are used with larger appliances,
including those that have three‑prong grounding plugs.
Some tools and appliances use polarized plugs.
A polarized plug has one wide (neutral) prong and
one narrow (hot) prong, corresponding to the neutral TOOLS & MATERIALS
and hot slots found in a standard receptacle.
If there is room in the plug body, tie the individual Combination tool Screwdriver
wires in an underwriter’s knot to secure the plug to Needlenose pliers Replacement plug
the cord (see photo, opposite page, top).

How to Install a Quick‑Connect Plug

Casing 1 2 3

Ridged half

Core

Wide prong

Squeeze the prongs of the new Feed unstripped wire through the rear of When replacing a polarized plug, make
quick‑connect plug together slightly, the plug casing. Spread the prongs, and sure that the ridged half of the cord
and pull the plug core from the casing. then insert the wire into the opening lines up with the wider (neutral) prong
Cut the old plug from the flat‑cord wire in the rear of the core. Squeeze the of the plug.
with a combination tool, leaving a clean prongs together; spikes inside the core
cut end. penetrate the cord. Slide the casing
over the core until it snaps into place.

308 THE COMPLETE GUIDE TO WIRING

 How to Replace a Round‑Cord Plug

1 2

Underwriter’s knot

Cut off the round cord near the old plug using a combination Tie an underwriter’s knot with the black and the white wires.
tool. Remove the insulating faceplate on the new plug and Make sure the knot is located close to the edge of the
feed the cord through the rear of the plug. Strip about 3" of stripped outer insulation. Pull the cord so that the knot slides
outer insulation from the round cord. Strip ¾" insulation from into the plug body.
the individual wires.

3 4

Hook the end of the black wire clockwise around the brass Tighten the screws securely, making sure the copper wires do
screw and the white wire around the silver screw. On a not touch each other. Replace the insulating faceplate.
three‑prong plug, attach the third wire to the grounding screw.
If necessary, excess grounding wire can be cut away.

How to Replace a Flat‑Cord Plug

Casing cover
1 2

Cut the old plug from cord using a combination tool. Pull apart Hook the ends of the wires clockwise around the screw
the two halves of the flat cord so that about 2" of wire are terminals, and tighten the screw terminals securely.
separated. Strip ¾" insulation from each half. Remove the Reassemble the plug casing. Some plugs may have an
casing cover on the new plug. insulating faceplate that must be installed.

REPAIR PROJECTS 309

 How to Replace a Lamp Cord

1 2
With the lamp unplugged, the shade off, and the bulb out, Under the outer shell there is a cardboard insulating sleeve.
you can remove the socket. Squeeze the outer shell of the Pull this off and you’ll reveal the socket attached to the end of
socket just above the base, and pull the shell out of the base. the cord.
The shell is often marked “Press” at some point along its
perimeter. Press there and then pull.

3 4
With the shell and insulation set aside, pull the socket away Remove the old cord from the lamp by grasping the cord near
from the lamp (it will still be connected to the cord). Unscrew the base and pulling the cord through the lamp.
the two screws to completely disconnect the socket from the
cord. Set the socket aside with its shell (you’ll need them to
reassemble the lamp).

310 THE COMPLETE GUIDE TO WIRING

 5 6
Bring your damaged cord to a hardware store or home center Carefully separate the two halves of the cord. If the halves
and purchase a similar cord set. (A cord set is simply a won’t pull apart, you can carefully make a cut in the middle
replacement cord with a plug already attached.) Snake the with a knife. Strip away about ¾" of insulation from the end of
end of the cord up from the base of the lamp through the top each wire.
so that about 3" of cord is visible above the top.

Outer sleeve

Insulating sleeve

7 8
Connect the ends of the new cord to the two screws on the Set the socket on the base. Make sure the switch isn’t blocked
side of the socket (one of which will be silver in color, the by the harp—the part that holds the shade on some lamps.
other brass colored). The neutral wire of the cord will have Slide the cardboard insulating sleeve over the socket so the
ribbing or markings along its length; wrap that wire clockwise sleeve’s notch aligns with the switch. Now slide the outer
around the silver (neutral) screw, and tighten the screw. sleeve over the socket, aligning the notch with the switch. It
The other half of the cord will be smooth; wrap it around the should snap into the base securely. Screw in a lightbulb, plug
copper (hot) screw, and tighten the screw. Tie the two wires the lamp in, and test it.
into an underwriter’s knot (page 309) as applicable.

REPAIR PROJECTS 311

 Replacing a Lamp Socket

N ext to the cord plug, the most common source

of trouble in a lamp is a worn lightbulb socket.
When a lamp socket assembly fails, the problem
is usually with the socket‑switch unit, although
replacement sockets may include other parts you do
not need.
Lamp failure is not always caused by a bad socket.
You can avoid unnecessary repairs by checking
the lamp cord, plug, and lightbulb before replacing
the socket.

TOOLS & MATERIALS

Replacement socket
Continuity tester
Screwdriver

Socket‑mounted switch types are usually interchangeable:

choose a replacement you prefer. Clockwise from top left:
twist knob, remote switch, pull chain, push lever.

TIP
When replacing a lamp socket, you can improve a
standard ON‑OFF lamp by installing a three‑way socket.

312 THE COMPLETE GUIDE TO WIRING

 How to Repair or Replace a Lamp Socket

Outer shell
1 3
Contact tab

Insulating sleeve
2
Unplug the lamp. Remove the shade, Squeeze the outer shell of the socket Check for loose wire connections on
lightbulb, and harp (shade bracket). near the “Press” marking, and lift it the screw terminals. Refasten any loose
Scrape the contact tab clean with a small off. On older lamps, the socket may be connections, and then reassemble the
screwdriver. Pry the contact tab up slightly held by screws found at the base of the lamp, and test. If connections are not
if flattened inside the socket. Replace the screw socket. Slip off the cardboard loose, remove the wires, lift out the
bulb, plug in the lamp, and test. If the insulating sleeve. If the sleeve is socket, and continue with the next step.
lamp does not work, unplug, remove the damaged, replace the entire socket.
bulb, and continue with the next step.

Tester probe
5 Harp

Exposed wire

Tester
clip
Silver Outer
shell Insulating
screw
sleeve

Ridged Smooth Cap

4 insulation insulation
6
Test for lamp cord problems with a If cord and plug are functional, then Slide the insulating sleeve and outer
continuity tester. Place the clip of the choose a replacement socket marked shell over the socket so that the
tester on one prong of the plug. Touch with the same amp and volt ratings as socket and screw terminals are fully
the probe to one exposed wire, and then the old socket. One half of flat‑cord covered and the switch fits into the
to the other wire. Repeat the test with lamp wire is covered by insulation that is sleeve slot. Press the socket assembly
the other prong of the plug. If the tester ridged or marked: attach this wire to the down into the cap until the socket locks
fails to light for either prong, then replace silver (neutral) screw terminal. Connect into place. Replace the harp, lightbulb,
the cord and plug. Retest the lamp. the other wire to the brass (hot) screw. and shade.

REPAIR PROJECTS 313

Common Wiring
Problems &
Solutions

A n electrical inspector visiting your home might

identify a number of situations that are not up
to code. These situations may not be immediate
problems. In fact, it is possible that the wiring in your
home has remained trouble-free for many years.
Nevertheless, any wiring or device that is not up
to code carries the potential for problems, often at
risk to your home and your family. In addition, you
may have trouble selling your home if it is not wired
according to accepted methods.
While this book cannot possibly identify all
potential wiring problems in your house, we have
identified some of the most common wiring defects
here and will show you how to correct them. If you
have questions regarding your home wiring system,
consult an electrician or the local building department.

In this chapter:
• Service Panels & Grounding
• Cables & Wires
• Boxes
• Cords
• Receptacles & Switches
• Light Fixtures

COMMON WIRING PROBLEMS & SOLUTIONS 315

 Service Panels & Grounding

Problem: Rust stains are found inside the main service panel. Solution: Have an electrician examine the service mast,
This problem occurs because water seeps into the service weather head, service entrance cables, and the main panel.
head outside the house and drips down into the service panel. If the panel or service wires have been damaged, a new
electrical service must be installed.

Problem: This problem is actually a very old and very Solution: Remove the penny and replace the fuse. Have a
dangerous solution. A penny or a knockout behind a fuse licensed electrician examine the panel and circuit wiring.
effectively bypasses the fuse, preventing an overloaded circuit If the fuse has been bypassed for years, wiring may be
from blowing the fuse. This is very dangerous and can lead to dangerously compromised, and the circuit may need to be
overheated wiring. replaced. In addition, if you have the old Edison fuse socket,
replace it with a new S‑type fuse socket. This eliminates the
related problem of installing the wrong‑size fuse in the panel.

Problem: Two wires connected to one single‑pole breaker is Solution: If there is room in the panel, install a separate
a sign of an overcrowded panel and also a dangerous code breaker for the extra wire. If the panel is overcrowded, have
violation unless the breaker is approved for such a connection. an electrician upgrade the panel or install a subpanel.

316 THE COMPLETE GUIDE TO WIRING

Problem: Too much bare wire exposed at the breaker Problem: There is no handle tie (or there is an improper
connection. This presents a short‑circuit hazard. handle tie) on breaker pair controlling a 240‑volt circuit.
Solution: With power off, trim the feed wire so no more than Solution: Install a handle tie approved by the circuit
½" of bare wire is exposed, and then reconnect. breaker manufacturer.

Problem: Conductor too small for breaker size. The #14 Problem: There is more than one neutral in a buss terminal.
copper wires seen here are rated for 15‑amp circuits. The Sharing slots is fine for grounding wires, but each neutral wire
30‑amp breaker allows too much current in the wires and should have its own terminal. Solution: Remove one of the
could cause a fire. Solution: Replace the wires with wires wires and find an open neutral terminal for it.
approved for the circuit breaker size.

COMMON WIRING PROBLEMS & SOLUTIONS 317

 Problem: Arc‑fault protection (AFCI) circuit breakers may fail, Problem: GFCI circuit breakers may fail, especially if they are
especially if they are tripped with some frequency. Solution: tripped with some frequency. Solution: Test each breaker as
Test each breaker as recommended by the manufacturer by recommended by the manufacturer by depressing the “Test”
depressing the “Test” button. If the breaker is functioning button. If the breaker is functioning correctly, it will trip when
correctly, it will trip when the button is pushed. the button is pushed.

Correct

Problem: There is a missing cable clamp at panel box. Problem: The shared hot terminal on the breaker is not wired
All NM cable entering a service panel (or any other box) correctly. The example above is correct: the conductors should
needs protection from sharp edges that can cut sheathing. be positioned on opposite sides of the terminal and held
Solution: Disconnect the cable in the box, and retract and securely in the separate grooves by the terminal screw.
reinstall it with a cable clamp.

318 THE COMPLETE GUIDE TO WIRING

Cables & Wires

Problem: Cable running across joists or studs is attached to Solution: Protect cable by drilling holes in framing members
the edge of framing members. Electrical codes forbid this type at least 2" from exposed edges and threading the cable
of installation in exposed areas such as unfinished basements through the holes.
and crawl spaces.

Problem: Cable running along joists or studs hangs loosely. Solution: Anchor the cable to the side of the framing members at
Loose cables can be pulled accidentally, causing damage least 1¼" from the edge using plastic staples. NM cable should
to wires. be stapled every 4½ ft. and within 8" of each electrical box.

Cable shown cutaway

Problem: Cable threaded through studs or joists lies close to Solution: Install metal nail guards to protect cable from
the edge of the framing members. NM cable (shown cutaway) damage. Nail guards are available at hardware stores and
can be damaged easily if nails or screws are driven into the home centers.
framing members during remodeling projects.

COMMON WIRING PROBLEMS & SOLUTIONS 319

 Problem: Unclamped cable enters a metal electrical box. Solution: Anchor the cable to the electrical box with a
Edges of the knockout can rub against the cable sheathing cable clamp. Several types of cable clamps are available at
and damage the wires. hardware stores and home centers.

NOTE: With smaller plastic boxes, clamps are not required

if cables are anchored to framing members within 8" of
the box.

Problem: Cables are spliced outside an electrical box. Exposed Solution: Bring installation up to code by enclosing the
splices can spark and create a risk of shock or fire. splice inside a metal or plastic electrical box. Make sure the
box is large enough to accommodate the number of wires
it contains.

320 THE COMPLETE GUIDE TO WIRING

Problem: Standard cable staples are not rated for more than Solution: Secure multiple cables with an approved cable
one cable; cables should not be stacked under a single stacker device. These can hold up to four cables and are
staple. Stapling cables side by side usually violates the 1¼‑ fastened with a single nail or screw. Install a cable stacker
inch minimum setback from the framing edge. within 12 inches of the box.

COMMON WIRING PROBLEMS & SOLUTIONS 321

 Pigtail

Problem: Two or more wires are attached to a single‑screw Solution: Disconnect the wires from the screw terminal, and
terminal. This type of connection is seen in older wiring but is then join them to a short length of wire (called a pigtail) using
now prohibited by the NEC. a wire connector. Connect the other end of the pigtail to the
screw terminal.

Exposed wire

Problem: Bare wire extends past a screw terminal. Exposed Solution: Clip the wire and reconnect it to the screw terminal.
wire can cause a short circuit if it touches the metal box or In a proper connection, the bare wire wraps completely
another circuit wire. around the screw terminal, and the plastic insulation just
touches the screw head.

Problem: Wires are connected with electrical tape. Electrical Solution: Replace electrical tape with wire connectors. You
tape was used frequently in older installations, but it can may need to clip away a small portion of the wire so the bare
deteriorate over time, leaving bare wires exposed inside the end will be covered completely by the connector.
electrical box.

322 THE COMPLETE GUIDE TO WIRING

Problem: Nicks and scratches in bare wires interfere with the Solution: Clip away damaged portion of wire, restrip about ¾"
flow of current. This can cause the wires to overheat. of insulation, and reconnect the wire to the screw terminal.

Boxes

Problem: Insulation on wires is cracked or damaged. If Solution: Wrap damaged insulation temporarily with plastic
damaged insulation exposes bare wire, a short circuit can electrical tape. Damaged circuit wires should be replaced by
occur, posing a shock hazard and fire risk. an electrician. (continued)

COMMON WIRING PROBLEMS & SOLUTIONS 323

 Problem: Open electrical boxes create a fire hazard if a short Solution: Cover an open metal box with a solid metal cover
circuit causes sparks (arcing) inside the box. plate. Cover an open plastic box with a plastic cover plate.
Cover plates are available at any hardware store. Electrical
boxes must remain accessible and cannot be sealed inside
ceilings or walls.

Problem: Short wires are difficult to handle. The NEC requires Solution: Lengthen circuit wires by connecting them to short
that each wire in an electrical box have at least 3" of workable pigtail wires using wire connectors. Pigtails can be cut from
length from the front of the box. scrap wire but should be the same gauge and color as the
circuit wires and at least 3" long.

Problem: A recessed electrical box is hazardous, especially Solution: Add an extension ring to bring the face of the
if the wall or ceiling surface is made from a flammable electrical box flush with the surface. Extension rings come in
material, such as wood paneling. The NEC prohibits this type several sizes and are available at hardware stores.
of installation.

324 THE COMPLETE GUIDE TO WIRING

Problem: Open electrical boxes create a fire hazard if a short Solution: Vacuum the electrical box clean using a narrow
circuit causes sparks (dust and dirt in an electrical box nozzle attachment. Make sure power to the box is turned off
can cause hazardous high‑resistance short circuits). When at the panel before vacuuming.
making routine electrical repairs, always check the electrical
boxes for dust and dirt buildup.

Problem: A crowded electrical box (shown cutaway) Solution: Replace the electrical box with a deeper
makes electrical repairs difficult. This type of installation is electrical box.
prohibited, because the heat in the box can damage the wire
or device and cause a fire.

Problem: A light fixture is installed without an electrical box. Solution: Install an approved electrical box to enclose the wire
This installation exposes the wiring connections and provides connections and support the light fixture.
no support for the light fixture.

COMMON WIRING PROBLEMS & SOLUTIONS 325

 Cords

Problem: A lamp or appliance cord runs underneath a rug. Solution: Reposition the lamp or appliance so that the cord is
Foot traffic can wear off insulation, creating a short circuit that visible. Replace worn cords.
can cause fire or shock.

Problem: An older electric dryer or range has a three‑prong Solution: Replace the three‑prong cord with a new, UL‑listed
cord that does not fit the four‑slot receptacle in the house. four‑prong cord that is properly rated for the appliance. See
pages 192 to 193 for dryer/range cord installation.

326 THE COMPLETE GUIDE TO WIRING

Problem: A lamp or appliance plug is cracked, or an electrical Solution: Cut away damaged portions of wire, and install
cord is frayed near the plug. Worn cords and plugs create a a new plug (see pages 308–309). Replacement plugs are
fire and shock hazard. available at appliance stores and home centers.

Problem: An extension cord is too small for the power load Solution: Use an extension cord with wattage and amperage
drawn by a tool or appliance. Undersized extension cords ratings that meet or exceed the rating of the tool or appliance.
can overheat, melting the insulation and leaving bare Extension cords are for temporary use only. Never use an
wires exposed. extension cord for a permanent installation.

COMMON WIRING PROBLEMS & SOLUTIONS 327

 Receptacles & Switches

Problem: Octopus receptacle attachments used Solution: Use a multireceptacle power strip with built‑in
permanently can overload a circuit and cause overheating of overload protection. This is for temporary use only. If the need
the receptacle. for extra receptacles is frequent, upgrade the wiring system.

Problem: Scorch marks near screw terminals indicate that Solution: If the insulation is damaged, cut the wires back
electrical arcing has occurred. Arcing usually is caused by to intact insulation. Otherwise, clean the wires with fine grit
loose wire connections. sandpaper or steel wool. Replace the receptacle. Make sure
wires are connected securely to screw terminals.

Problem: Two‑slot receptacle in outdoor installation is Solution: Replace the old receptacle with a weather‑resistant
hazardous because it has no grounding slot. In case of a short GFCI receptacle to provide protection against ground faults. If
circuit, a person plugging in a cord becomes a conductor for the receptacle is exposed to the elements, be sure to include
current to follow to ground. a cover rated for wet locations.

328 THE COMPLETE GUIDE TO WIRING

Problem: White neutral wires are connected to a switch. Solution: Connect the black hot wires to the switch, and join
Although the switch appears to work correctly in this the white wires together with a wire connector.
installation, it is dangerous because the light fixture carries
voltage when the switch is off.

Problem: White neutral wires are connected to the brass Solution: Reverse the wire connections so that the black
screw terminals on the receptacle, and black hot wires hot wires are attached to brass screw terminals and white
are attached to silver screw terminals. This installation is neutral wires are attached to silver screw terminals. Live
hazardous because live voltage flows into the long neutral slot voltage now flows into the short slot on the receptacle.
on the receptacle.

COMMON WIRING PROBLEMS & SOLUTIONS 329

 Problem: Three-prong appliance plugs do not fit a two-slot Solution: Install a three-slot grounded receptacle if a means of
receptacle. Three-prong plug adapters do not provide a grounding exists at the box. If no ground is present, install a
ground unless the receptacle is grounded to a grounded GFCI receptacle to provide ground-fault protection.
metal box and the metal loop on the adapter is secured under
the cover plate screw. Note: This improves safety but does not provide a true
ground. Attach a “No Equipment Ground” sticker to the
receptacle cover plate if no ground is present.

Problem: A receptacle is loose and/or pushes in when you Solution: Install receptacle spacers behind the ears of the
plug in a cord, due to a slightly recessed box. receptacle so the receptacle mounts securely to the box.
Spacers are inexpensive and are designed for this purpose.

Note: If the box is recessed more than 1/4 inch from the wall
surface, install a box extension ring instead of shims (see
page 324).

330 THE COMPLETE GUIDE TO WIRING

Light Fixtures

Problem: Ceiling insulation must be held back from a Solution: Replace the fixture with an ICAT-rated model, which
recessed light fixture that is not rated for insulation contact can be covered with insulation and is also airtight (AT) to
(IC), creating a sizable hole in the ceiling’s thermal barrier. prevent conditioned room air from leaking into the attic. This
upgrade saves energy and helps to prevent ice dams (caused
by excessive heat in the attic).

Problem: Lamps and other light fixtures with high-wattage Solution: Replace high-wattage incandescent bulbs with
incandescent lightbulbs exceeding the fixture’s maximum LED bulbs with comparable light output (measured in
wattage rating can damage the fixture wiring and scorch the lumens). A 17.5-watt LED bulb has the same light output
cardboard socket sleeve. (1,600 lumens) of a 100-watt incandescent bulb and
produces much less heat.

COMMON WIRING PROBLEMS & SOLUTIONS 331

 Conversions
METRIC EQUIVALENT
Inches (in.) ⁄64
1
⁄32
1 1
⁄25 ⁄16
1
⁄8
1
⁄4
1
⁄8
3 2
⁄5 ⁄2
1 5
⁄8 3
⁄4 ⁄8
7
1 2 3 4 5 6 7 8 9 10 11 12 36 39.4
Feet (ft.) 1 3 31⁄12
Yards (yd.) 1 11⁄12
Millimeters (mm) 0.40 0.79 1 1.59 3.18 6.35 9.53 10 12.7 15.9 19.1 22.2 25.4 50.8 76.2 101.6 127 152 178 203 229 254 279 305 914 1,000
Centimeters (cm) 0.95 1 1.27 1.59 1.91 2.22 2.54 5.08 7.62 10.16 12.7 15.2 17.8 20.3 22.9 25.4 27.9 30.5 91.4 100
Meters (m) .30 .91 1.00

CONVERTING MEASUREMENTS
TO CONVERT: TO: MULTIPLY BY: TO CONVERT: TO: MULTIPLY BY:
Inches Millimeters 25.4 Millimeters Inches 0.039
Inches Centimeters 2.54 Centimeters Inches 0.394
Feet Meters 0.305 Meters Feet 3.28
Yards Meters 0.914 Meters Yards 1.09
Miles Kilometers 1.609 Kilometers Miles 0.621
Square inches Square centimeters 6.45 Square centimeters Square inches 0.155
Square feet Square meters 0.093 Square meters Square feet 10.8
Square yards Square meters 0.836 Square meters Square yards 1.2
Cubic inches Cubic centimeters 16.4 Cubic centimeters Cubic inches 0.061
Cubic feet Cubic meters 0.0283 Cubic meters Cubic feet 35.3
Cubic yards Cubic meters 0.765 Cubic meters Cubic yards 1.31
Pints (U.S.) Liters 0.473 (lmp. 0.568) Liters Pints (U.S.) 2.114 (lmp. 1.76)
Quarts (U.S.) Liters 0.946 (lmp. 1.136) Liters Quarts (U.S.) 1.057 (lmp. 0.88)
Gallons (U.S.) Liters 3.785 (lmp. 4.546) Liters Gallons (U.S.) 0.264 (lmp. 0.22)
Ounces Grams 28.4 Grams Ounces 0.035
Pounds Kilograms 0.454 Kilograms Pounds 2.2
Tons Metric tons 0.907 Metric tons Tons 1.1

CONVERTING TEMPERATURES FAHRENHEIT CELSIUS

Convert degrees Fahrenheit (F) to degrees Celsius (C) by following this simple
formula: Subtract 32 from the Fahrenheit temperature reading. Then mulitply that 55° 25°
number by 5⁄9. For example, 77°F ‑ 32 = 45. 45 × 5⁄9 = 25°C. 50° 20°
45° 15°
To convert degrees Celsius to degrees Fahrenheit, multiply the Celsius temperature
40° 10°
reading by 9⁄5 or 1.8, then add 32. For example, 25°C × 9⁄5 = 45. 45 + 32 = 77°F.
35° 5°
30° FREEZING 0°
25° −5°
20° −10°
15° −15°
10° −20°
5° −25°
0° −30°

332 THE COMPLETE GUIDE TO WIRING

Resources Photo Credits Index
Black & Decker p. 177 photo © Mike Clarke / A
Portable power tools and more www.istock.com aboveground service drops, 175, 181
www.blackanddecker.com p. 202 photo © George Peters / AFCI receptacles
www.istock.com about, 98, 168–169
Broan‑NuTone, LLC
p. 206 photo courtesy of Broan NuTone code requirements for, 121
Vent fans
p. 218 photo (top right) courtesy of common problems with, 318
www.broan‑nutone.com
Kohler installing, 170–171
Generac Power Systems p. 220 photo courtesy of Ikea air conditioners, 127, 129, 158
Standby generators p. 250 photo © George Peters / alarms, smoke and CO, 125, 224–225
and switches www.istock.com ampacity (of wires), 10, 26, 29
www.generac.com p. 251 photo © David Ross / amperage, 126
www.istock.com ampere (amp), defined, 14
Honda Power Equipment/
p. 263 (top right) photo © appliances, 156, 158, 192–197
American Honda Motor
Steve Harmon / istock.com, (lower armored cable, 14, 19, 27
Company, Inc.
right) photo courtesy of SieMatic attics, wiring overview for, 146
Standby generators
p. 266 photo © Jeff Chevrier /
www.hondapowerequipment.
com
www.istock.com B
p. 267 photos (top right & lower) backup power supplies
Kohler courtesy of Generac Power about, 266
Standby generators Systems, Inc. choosing, 267–268
www.kohlergenerators.com p. 278 photo courtesy of Cabin Fever, running and maintaining, 270–271
featuring McMaster Carr vapor‑tight transfer switches for, 269, 272–277
Pass & Seymour Legrand
light fixtures ballast, replacing, 306
Home automation products
www.legrand.us/pass‑and‑ baseboard heaters, 129, 157, 238–241
seymour basements, wiring overview for, 145
bathrooms
Red Wing Shoes Co. code requirements for, 116, 121
Work shoes and boots exhaust fans in, 258–261
shown throughout book vanity lights, 218–219
www.redwingshoes.com wiring overview for, 138–139
Unistrut Metal Framing bedrooms
Solar panel mounts code requirements for, 121
www.unistrut.us smoke alarms in, 125
wiring overview for, 141
Westinghouse bell‑hanger’s big, 40, 319–323
Ceiling fans, decorative bonding, 182–184, 187
lighting, solar outdoor lighting, boxes. See electrical boxes; junction
& other lighting fixtures boxes
and bulbs
www.westinghouse.com C
cable lights, low‑voltage, 220–223
cable ripper, 20
cable staples, 31
cables
about, 26
code requirements for, 116, 120
defined, 14

RESOURCES/PHOTO CREDITS/INDEX 333

 problems & solutions for, 319–321 cords replacing, 62
sheathing damage, 124 for dryers and ranges, 194–197, 326 specifications for, 53
types of, 27–28 problems & solutions for, 326–327 wallcovering thickness and, 59
carbon monoxide (CO) alarms, 125, repairing, 308–311 electrical loads
224–225 countdown timer switch, 84 calculating, 127
cartridge fuses, 69 crawlspaces, wiring overview for, 146 estimating, 130–131
Cat 5 cable, 28 current, defined, 14 evaluating, 113, 126
ceiling boxes, 60 electrical panels. See main service
ceiling fans D panels; service panels
about, 250 daylight sensor switch, 85 electrical symbol key, 133
installing, 253 delivery system, 11 electrical system
layouts for, 165 diagnostic tools, 21 diagram of, 15
remote‑control, 254–257 dimmer switches, 85–86 parts of, 12–13
repairing, 298–301 dining rooms terminology for, 14
support for, 117, 252 code requirements for, 121 electrical transformers, 11
types of, 251 wiring overview for, 140 electrician’s tape, 32
ceiling lights dishwashers, 128 electricity, how it works, 10
about, 202–203 doorbells electronic motion‑sensor switches, 75
recessed, 206–209 about, 230 emergency disconnect, 7
replacing, 204–205 replacing, 233 exhaust fans, 258–261
chandeliers, repairing, 296–297 testing nonfunctional, 231–232 extension cords, 267, 327
channel‑type pliers, 20 double switches, 82, 91
childproofing, 97 double‑insulated tools, 19 F
circuit breaker panels, 65–67 duplex receptacles fans. See ceiling fans; exhaust fans
circuit breakers about, 98 fish tape, 21
about, 68 defined, 14 fixed devices, 127
connecting, 70–71 layouts for, 150, 152–153, 161 flat‑cord plugs, 309
defined, 14 flexible metal conduit (FMC), defined,
resetting and testing, 69 E 14
circuit maps, 149–165 Edison adapters, 68 floodlights, motion‑sensing, 286–289
circuits Edison fuses, 316 fluorescent lights, repairing, 302–307
defined, 14 electric baseboard heaters, 129, 157, food disposers, 128
rating for, 125 239–241 forced‑air furnaces, wattage of, 129
understanding, 16–17 electric ranges four‑way wall switches, 80–81, 89
closets cords for, 194–197 foyers, wiring overview for, 142–143
code requirements for, 117 hoods for, 262–265 freezers, 129
lighting in, 125 receptacles for, 193 fuses
clothes dryers, 129, 192, 194–197 wattage for, 128 about, 68
coaxial cable, 28 wiring layouts for, 157 defined, 14
code requirements, 112, 115–121 electrical bonding of metal conduit, 42 identifying and replacing blown, 69
compatibility, 23 electrical boxes replacing cartridge, 69
computer circuits, 158 about, 50
conductor, defined, 14 ceiling boxes, 60 G
conduits code requirements for, 120 garages, wiring overview for, 145
about, 42–43 common, 51–52 gas pipes, bonding, 182–184
defined, 14 defined, 14 generators. See backup power supplies
electrical bonding of metal, 42 in electrical system, 13 GFCI receptacles
installing on concrete walls, 46–47 fill chart, 50 about, 98, 104, 168, 170
nonmetallic conduit connections, 45 installing, 56–63 code requirements for, 118, 121
types of, 42–43 installing for light fixtures, 58 common problems with, 318
working with, 44 installing for switches, 58 installing, 170–171
connections installing junction boxes, 60–61 installing for multiple‑location
checking, 322–323 installing pop‑in retrofit, 62–63 protection, 106–107
fixing loose, 299 knockouts on, 124 installing for single‑location
connectors, push‑in, 31 locating, 59 protection, 105
continuity, defined, 14 nonmetallic, 54–55 layouts for, 150–151, 156
conversions, 332 problems & solutions for, 323–325 updates regarding, 7

334 THE COMPLETE GUIDE TO WIRING

Greenfield, 14 linesman pliers, 20 P
ground rod installation, 185–187 living rooms permits, 113, 132
grounded wire, defined, 14 code requirements for, 121 pigtail wires, 14, 33
grounding, 18–19, 118, 182, 184 wiring overview for, 140 pilot‑light switches, 83, 90
grounding electrode system, installing, low‑voltage cable lights, 220–223 plastic conduit, 43
185–187 pliers, 20
grounding wires, 12, 14 M plug‑in testers, 109
main service panels plugs, repairing, 308–311
H about, 64 polarization, 18–19
hallways code requirements for, 119, 120 polarized receptacles, 14, 19
code requirements for, 117, 121 in electrical system, 13 pop‑in retrofit boxes, 62–63
wiring overview for, 142–143 examining, 112, 114 power, defined, 14
hand tools, 20 replacing, 177–181 power plants, 11
heat pumps, 129 See also service panels programmable timer switch, 84, 91
heating appliances/systems, 127, 129, mercury switches, 75 project planning
238–249. See also thermostats metal conduit, 27, 43 about, 112
hot wire, defined, 14 meters, 12, 14 steps for, 112–113
metric conversions, 332 push‑button switches, 75
I microwave ovens, 128 push‑in connectors, 31
inspections, 113, 122–125 motion‑sensing floodlights, 286–289
installing, AFCI, 170–171 motion‑sensor switches, 91 Q
insulator, defined, 14 multimeters, 109 quick‑connect plugs, 308
isolated‑ground receptacle, 158
N R
J National Electrical Code (NEC), 112, radiant heat systems, 244–245
junction boxes, 60–61. See also 115–121 range hoods, 262–265
electrical boxes needlenose pliers, 20 receptacles (outlets)
neutral conductors, 124 adapters for, 19
K neutral wire AFCI, 121, 168–169
kitchens defined, 14 childproofing, 97
code requirements for, 116, 121 separate, 156 code requirements for, 116–118, 120
wiring overview for, 135–137 shared, 156 common problems with, 99
knob and tube wiring, 27 nonmetallic conduit connections, 45 defined, 14
nonmetallic sheathed cable duplex, 98
L about, 19, 27–28, 34 in electrical system, 13
lamp cords, 310–311 colors of, 28 high‑voltage, 96
lamp sockets, repairing, 312–313 installing, 35–38 installing electrical boxes for, 57
landscape lights, 226–229 installing in finished ceilings, 41 installing GFCI, 105–107
laser level, 20 reading, 29 installing new, 102–103
laundry rooms running inside finished wall, 39–40 isolated‑ground, 158
code requirements for, 119, 121 stripping, 30 layouts for, 161
wiring overview for, 144 nonmetallic sheathed cable, defined, older, 95
light fixtures 14 outdoors, 198–201
ceiling, 202–209 polarized, 14, 19
code requirements for, 118, 120–121 O problems & solutions for, 328–330
in electrical system, 12 occupancy sensors, 85 spacing for, 123
installing electrical boxes for, 58 octagonal boxes, 50–51 split, 154–155
landscape lights, 226–229 outbuildings, 278–285 switch/receptacles, 83, 91
layouts for, 151–153, 159–164 outdoors testing, 108–109
motion‑sensing floodlights, 286–289 code requirements for, 121 types of, 14, 94
problems & solutions for, 331 installing fixture box, 287 wired in sequence, 150
repairing, 292–295 landscape lights, 226–229 wiring for, 100–101
replacing for fluorescent lights, 307 receptacles (outlets), 198–201 See also GFCI receptacles
track lights, 210–213 wiring overview for, 147 recessed ceiling lights, 206–209
undercabinet lights, 214–217 outlets. See receptacles (outlets) remote‑control ceiling fans, 254–257
vanity lights, 218–219 overload, defined, 14 repair projects
lightbulbs, 128 ceiling fans, 298–301

INDEX 335
 chandeliers, 296–297 stud finders, 20 U
fluorescent lights, 302–307 S‑type fuses, 316 UF (underground feeder) cable, 27–28
lamp sockets, 312–313 subpanels, 188–191 UL, 14
light fixtures, 292–295 substations, 11 undercabinet lights, installing,
plugs and cords, 308–311 surge protection, 7, 172–173 214–217
Romex, 14 switches underfloor radiant heat systems,
room‑by‑room wiring about, 74–75 244–245
about, 134 action options for, 86 underground service lateral, 175
attics, 146 code requirements for, 120 utility knives, 20
basements, 145 defined, 14
bathrooms, 138–139 dimmer, 85–86 V
bedrooms, 141 double, 82 vanity lights, 218–219
crawlspaces, 146 in electrical system, 13 voltage (volts), defined, 14
dining rooms, 140 four‑way wall, 80–81, 163–164
foyers, 142–143 ganged, 159, 165 W
garages, 145 installing electrical boxes for, 58 wall heaters, 242–243
hallways, 142–143 layouts for, 151–154, 159–165 wall switches
kitchens, 135–137 neutral conductors for, 124 about, 74
laundry rooms, 144 pilot‑light, 83 double, 82
living rooms, 140 problems & solutions for, 328–329 four‑way, 80–81
outdoors, 147 repairing pull‑chain, 300–301 single‑pole, 77
stairs, 142–143 replacing built‑in, 295 three‑way, 78–79
rotary snap switches, 75 single‑pole wall, 77 types of, 75–76
round‑cord plugs, 309 specialty, 84–85 water flow, 11
testing, 88–90 water heaters, 11, 128, 182–183
S three‑way wall, 78–79, 160–162 water pipes, bonding, 182–184
safety, 9–23 time‑delay, 91 wattage (watts)
screw terminals timer, 84–85, 90 defined, 14
connecting wire to, 31 types of, 75–76 locating, 128–129
defined, 14 wall, 74–81 whole‑house surge arrestors, 172–173
screwdrivers, 20 wireless, 234–237 wire
service entrance cable (SE), 28 switch/receptacles, 83, 91 about, 26
service lugs, 119 code requirements for, 120
service mast, 12 T color chart for, 26
service panels tamper‑resistant three‑slot connecting to screw terminals, 31
about, 64–65 receptacles, 19, 97 installing on concrete walls, 46–47
defined, 14 tape measure, 20 joining with wire connector, 32
grounding, 184 telephone cable, 28 pigtail, 33
installing, 174–181, 189–191 thermostats, 157, 239. See also reading unsheathed, 29
locating, 176 heating appliances/systems size chart for, 26
problems & solutions for, 316–318 THHN/THWN wire, 28 splices in, 124
replacing, 177–181 three‑way wall switches, 78–79, 89 tips for working with, 29
See also main service panels time‑delay switches, 91 wire connectors
short circuit, defined, 14 timer switches, 84–85, 90 defined, 14
side cutters, 20 toggle switches, 75 joining wires with, 32
single‑pole wall switches, 77, 88 tools wire strippers, 20
smart switches, 85 double‑insulated, 19 wireless switches, 234–237
smoke alarms, 125, 224–225 overview of, 20–21 wiring plans/diagrams
sockets track lights, installing, 210–213 drawing, 113, 132–133
replacing, 295 transfer switches electrical symbol key for, 133
replacing for fluorescent lights, 305 installing, 272–277 room‑by‑room, 134–147
replacing lamp, 312–313 types of, 269 wiring problems & solutions, 319–323
testing, 294 transformers, 119, 220–223
stairs
code requirements for, 116, 121
wiring overview for, 142–143
strain relief fittings, 195

336 THE COMPLETE GUIDE TO WIRING