INDUSTRIAL ELECTRICAL SYSTEM

MODULE 2

RESIDENTIAL AND COMMERCIAL ELECTRICAL

SYSTEMS

ANSHUL SHEKHAR
BCE BHAGALPUR
 Topics to be covered
Types of residential and commercial wiring systems, general
rules and guidelines for installation, load calculation and sizing
of wire, rating of main switch, distribution board and
protection devices, earthing system calculations, requirements
of commercial installation, deciding lighting scheme and
number of lamps, earthing of commercial installation, selection
and sizing of components.
 Electrical Wiring
A process of connecting various accessories for
distribution of electrical energy from supplier’s meter
board to home appliances such as lamps, fans and other
domestic appliances is known as Electrical Wiring.

The wiring system selected will depend to a large

extent on the types of service required.
Factors Affecting the Selection of Wiring

1. Durability

2. Safety

3. Appearance

4. Cost

5. Accessibility

6. Maintenance Cost
 System of Internal Wiring
1. Cleat wiring
2. Casing and capping wiring
3. Batten wiring
a) CTS or TRS or PVC sheath wiring
b) Lead sheathed or metal sheathed wiring
4. Conduit wiring
a) Surface or open Conduit type
b) Concealed or underground type Conduit
 Cleat Wiring
In this system of wiring, cables are supported and gripped
between porcelain cleats and above the wall or roof.

The main part is base, which is grooved to accommodate the

cables, the other part is the cap which is put over the base
Cleats are either of porcelain, plastic or wood and are placed
above the wall or roof, at an interval of 30 to 60 cm.

The cables recommended for this type of wiring are VIR

cables (Vulcanized Indian Rubber) or PVC cables and any
other approved insulated cables.
Advantages
1. It is the cheapest system.
2. Installation and dismantling is easy.
3. Less skilled persons are required.
4. Inspection is easy.
5. Alterations and additions are easy.
Disadvantages
1. It is purely temporary wiring system.
2. Appearance is not good.
3. Cables are exposed to atmosphere and there is a possibility of
mechanical injury.
4. This system should not be used in damp places other wise
insulation gets damaged.
 Casing and Capping Wiring
It consists of rectangular blocks made from seasoned and knots
free wood , Now a days PVC is also used for manufacturing.

The casing has usually two (or three) shaped grooves, into
which the VIR or PVC cables are laid in such a way that the
opposite polarity cables are laid in different grooves.

The casing is covered by means of a rectangular strip of the

same width as that of casing known as capping and is screwed
to it.

This system of wiring is suitable for low voltage installations.

Casing & Capping Wiring
Components
Advantages
1. It provides good insulation as conductors are apart.
2. It provides good mechanical strength.
3. Easy to inspect by opening the capping.
Disadvantages
1. It is costly system if we use seasoned knot free wood.
2. There is every risk of fire.
3. The labor cost is more because it requires skilled carpenters.
4. This system can not be used in damp places.
Batten Wiring: CTS or TRS or PVC Sheath Wiring
T.R.S: Tough Rubber Sheath & C.T.S: Cab Tyre Sheath

In this type of wiring system, wire sheathed in tough

rubber are used which are quite flexible.

They are clipped on wooden battens with brass or tin clips

(spaced at an interval of 10 cm) and fixed on walls or ceiling
by flat head screws.

The width of the batten depends upon the number and size of
cables to be carried by it.

CTS cables are sufficiently chemical proof, water proof, steam

proof and hence suitable for damped location also.

This system is suitable for low voltage installations.

Advantages
1. It’s appearance is good, if carried properly.
2. It’s life is sufficiently long.
3. It can withstand the action of most chemicals such as acids and alkalies.
4. Installation is easy and quick compared to casing capping.
5. It is cheap compared to casing c–apping, metal conduit and lead
sheathed wiring.
Disadvantages
1. This system of wiring is not recommended in situations exposed to sun
and rain, unless preventive steps are taken.
2. Good work man ship is required to make a sound job.
3. Only suitable for voltage below 250V.
Batten Wiring: Lead or Metal Sheathed Wiring
In lead sheathed or metal sheathed wiring the cables used are
insulated wires, TRS or PVC, with metal outer covering of
about 1 mm thick. The metal covering is known as
sheathing and is made of lead-aluminium alloy containing
about 95% of lead.
The metal sheathed cables are
run on wooden batten and
are fixed to it by link clips. The
whole metal sheathing
efficiently earthed as per IS:
732-1983
Advantages
1. It provides protection against mechanical injury.
2. It can be used in damp situations.
3. It can be usedin situations exposed to sun and rain provided
no joint is exposed.
4. It has longer life.
Disadvantages
1. It is costly system of wiring.
2. It is not suitable where chemical (acids and alkalies)
corrosion may occur.
3. In case of insulation damage, the metal sheath become
alive and gives shock.
 Conduit Wiring System
Conduit wiring system consists of either VIR or PVC cables taken
through tubes or pipes and terminated at the outlets or switches /
sockets. The tube or pipe is known as conduit. C onduit wiring
may run over the surface of the walls and ceiling or may be
concealed under masonary work.
Types of Conduits
1. Rigid steel / metal conduit.
2. Rigid PVC / non- metallic conduit.
3. Flexible steel conduit.
4. Flexible PVC /non- metallic conduit.
Surface Conduit Wiring

In this type of wiring system, the wiring components

are laying on the surface of wall/roof. Metallic
conduits (steel) or PVC materials are used for surface
conduits wiring.

The conduit should be laid over the wooden gutties, and

should be fixed to the wall by means of saddles at an interval
of not more than 1.2 m.

All steel conduits should be coated or finished with

galvanized or enameled surface.
Surface Conduit Wiring
Concealed Conduit Wiring

The conduits (metal or PVC) are embedded along walls or

ceiling in plaster at the time of building construction. The
conduits are fixed by means of saddles not more than 60
cm. apart. The VIR or PVC cables are drawn into the
concealed by means of GI wire of size 18 SWG.

PVC conduits are increasingly being used in place of steel

conduits. PVC conduits are less expensive and the labour
time saved may be as much as 25% to 50% compared to
the time taken when installing steel conduits. PVC conduits
are resistant to acids alkalies, oil and moisture.
Concealed Conduit Wiring
Advantages
1. It provides protection against mechanical damage.
2. Metal conduits provides protection against fire due to short
circuit etc.
3. The whole system is water proof.
4. It’s life is long.
5. Replacement of defective wiring is easy.
6. It is shock proof if earthing is done properly.
7. PVC conduit wiring (particularly concealed) is cheap.
8. PVC conduit wiring requires less time.
9 . C oncealed conduit wiring appearance is very good.
Disadvantages
1. PVC conduit does not provide protection against fire.
2. Metal conduit wiring is very costly.
3. Metal conduit wiring requires more time.
4. Metal conduit wiring needs skilled labour.
5. Very hard to find the defects in the wiring.
6. Very complicated to manage additional connection in the
future.
 General Rules for Wiring
The following general rules should be kept in mind while executing
the electrical wiring work:
1. The current rating of the cable/conductor should be slightly greater (at
least 1.5 times) than the load current.
2. Every live wire/line should be protected by a fuse of suitable rating as
per load requirements.
3. Every sub- circuit should be connected with the fuse distribution board.
4. All metal coverings used for the protection of earth must be connected to
earth.
5. No switch or fuse is used in earth or neutral conductor.
6. Every apparatus should be provided with a separate switch.
7. A caution notice (danger plate) should be fixed on high voltage
equipment.
 General Rules for Wiring

8. No additional load should be connected to the existing installation until

it has been satisfied that the installation can safely carry the additional
load.

9. All the switches and starters should be accessible to the operator.

10. Light wiring and power wiring should be kept separately.

11. When the installation has been completed it should be tested before
giving the supply.

12. In 3-phase, 4 – wire installation the load should be distributed almost

equally on all the phases.

13. In case of 3-phse, 4-wire system, at the main board, indication should
be done in Red, Yellow and Blue. Neutral should be indicated in black.
 Electrical Installation Rules & Guidelines
Various standards are being followed for low-voltage installations. IS 4648-
1968 “Indian Standard Guide for Electrical Layout in Residential Building”
is one of them.
 Electrical Energy Distribution System
(as per electrical connection)

As per the recommendations of IS, each circuit shall not have more than
800 Watt connected load or more than 10 points which is less. In case of
CFL points where load per point may be less, number of points may be
suitably increased.
Hence, in case of more load or more points to be connected to the supply
system, then it is to be done by having more than one circuit through

(a) Distribution board system

(b) Tree system

 Distribution Board Systems
Most commonly adopted for distribution of electrical energy in a building.
The fuses of various circuits are grouped together on a distribution board,
known as fuse board.
Suitable for connecting two or more than two circuits, each consisting of 10
or less number of lamps is shown in fig.
The two copper strips known as bus bars fixed in a distribution board of
hard wood or metal case are connected to the supply mains through a
double pole iron clad (DPIC) switch so that the installation can be switched
off. A fuse is inserted in the positive or phase pole of each circuit so that
each circuit is connected up through its own particular fuse. The number of
circuits and sub-circuits is decided as per number of points to be wired and
load to be connected to the supply system.
Distribution Board Systems
Distribution Board Systems
 Tree Systems
Another system of distribution of electrical energy in a building is a tree
system. In this system smaller branches are taken from the main branch
as shown in fig and the wiring system resembles a tree. As each branch
is taken off, a fuse is inserted. This system used to be employed in early
days.
Now a days it is no more adopted due to the following drawbacks.
(i) The voltage across all the lamps does not remain the same. Voltage
across last branch will have least voltage due to voltage drop.
(ii) A number of joints are involved in every circuit.
(iii) Fuses are scattered.
(iv) In case of occurrence of faults all the joints have to be located.
Tree Systems
 Methods of Wiring
(as per electrical connection)

There are two methods of electrical wiring

(a) Joint Box or Tee System

(b) Loop-in system

 Joint Box or Tee System
In joint box system the connections to the lamps are made through joints
made in joint box by means of suitable connectors or joint cutouts.
In this method though there is a saving in the quantity of wire or cable
required but the same is offset by the extra cost of joint boxes. The other
disadvantage of tee connection is that number of ‘T’ connections made in
wiring system results in weakness if not properly made.
Now a days the use of this
system is limited to temporary
installations only as its cost is
low.
 Loop-in System
This system is universally used for connections of various lamps or other
appliances in parallel. In this system when a connection is required at a
light or switch, the feed conductor is looped in by bringing it direct to the
terminal and then carrying it forward again to the next point to be fed. The
switch and light feeds are carried round the circuit in a series of loops from
one point to another until the last point on the circuit is reached.

The phase or line conductors

are looped either in switch
board or box and neutrals are
looped either in switch board or
from light or fan. Line or phase
should never be looped from
light or fan
 Loop-in System
Advantages:
Joint boxes are not required.
Identification of fault location is easy.
Disadvantages:
Length of wire required is more and hence losses are more.
Looping-in in lamp holders and switches are little bit more difficult.
 Distribution Board
A distribution board is the main electrical supply system for any commercial
or residential entity. The main cable comes into the distribution board and
then via breakers get distributed in the secondary circuits such as lights and
plugs.
Distribution board is set of MCBs, ELCBs/RCCBs which are installed in a
metal box & is used to distribute electrical power to different loads.
Distribution Board
 Sub Circuits
 After the main switch the supply is taken tothe various load points.

 In the given circuit same circuit contains light, fan and power circuit which

has various drawbacks.

 Dividing the wiring into a number of smaller circuit is called sub- circuit.

 Sub-circuit divided into two parts:

a) Light and fan sub-circuit

b) Power Sub-circuit
 Determination of number of sub-circuits: It is decided as per number of

points to be wired & total load to be connected to the supply system.

In one light & fan circuit the maximum load that can be connected is 800
watts & the maximum number of points which can be wired is 10.

In one power sub-circuit the maximum load that can be connected is 3,000
watts and the number of socket-outlets which can be provided is 2.

 Determination of rating of main switch & distribution box (DB): The

current rating of main switch is decided as per total current of the circuit
to be controlled by it.

The number of ways and current rating of the DB is decided as per number
of sub-circuits to be connected to it and current of the sub-circuit having
highest current rating.
Single Phase Wiring
Three Phase Wiring
 Load calculation & sizing of wire
 Determination of number of points: Number of fan/light points is
determined as per the measure (length, height and width) of room and the
size/rating of fan/light. Higher the size of the fan (900 mm, 1200 mm, 1400
mm) higher will be delivery of air (in m3/minute) and lesser will be number of
fan required. Similarly, higher rating of light causes lesser number of installation
of light (high rating means high illumination). For determination of number of
socket-outlets, IS 4648-1968 shall be referred.

 Determination of total load: The total load of any premises may be

calculated by adding ratings of each electrical items.
 As per IS 4648-1968

Location No. of 5 Amp Socket-Outlet No. of 15 Amp Socket-Outlet

Bed Room 2 to 3 1

Living Room 2 to 3 2

Kitchen 1 2

Dining Room 2 1

Bathroom 1 1

For AC 0 1

For Refrigerator 0 1
 Rating of commonly used electrical items are

Appliances Ampere Used Watt Used

Laptop <0.5 65 - 100

Mobile phone charger <0.5 <12

Hair straightner <0.5 60 - 100

Fridge 0.65 150

Freezer 0.86 200

Kettle 13 3000

Printer <0.5 50

Hair dryer 10.0 2200

 Rating of commonly used electrical items are

Appliances Ampere Used Watt Used

Satellite TV box <0.5 30

Desk lamp (with 60 W lamp) <0.5 60

Computer monitor <0.5 100

Television 0.5 120

Washing machine 10 2200

Iron 12.5 2800

Microwave 4.5 1000

Vacuum cleaner 9.0 2000

 Calculation of loads

Example: Available loads are

Tube point - 1x40 = 40 watt

Lamp point – 1x100 = 100 watt
Fan point - 1x 60 = 60 watt
5 amp socket – 1x100= 100 watt
Total load in amperes = 300/230 = 1.3 A
Hence, Main switch of 5 Amp rating, 250 volt grade is selected.
 As per IS 4648-1968, recommended level of illumination for different parts of
residential building are as follows. This will help to decide number of lamps
required.
Location Illumination Level (Lux)

Bed Room 300

Living Room 300

Kitchen 200

Dining Room 150

Bathroom 100

Entrance 100

Stair 100

Study Room 300

Garage 70
Determination of size of wires: The wires dimensions are defined in terms
of sq.mm. of cross-section and sizing is determined based on current-
carrying capacity. The conductor used in house wiring (except flexible &
fitting wires) must not be of size less than 1/1.12 mm in copper or 1/1.40
mm (1.5 mm2) in aluminium wire.

• Important factors that determine the selection of cables

 Rated Voltage

 Current Carrying Capacity

 Voltage Drop

 Short circuit Withstand

Cable current rating for copper & aluminium conductors is shown below
The selection of wires, switches, MCB’s, Main MCB, plug tops etc. depends
upon the current to be drawn by load.
Example:
Power : 1500W (AC load)
Voltage : 220 Volt
Current : Power/(Voltage x P.F.) = 1500/ (220 x 0.8) = 8.5 Amp

Therefore, use of items for AC load based upon its current is as under:
Switch : 16A - 220V
Socket : 16A – 220V
Plug Top : 16A – 220V
MCB/SPN : 16A – 220V
PVC wires : 2.5 mm2
 Protective Devices
When a failure occurs on any part of the electrical power system, it must be
quickly detected and disconnected from the system. There are two reason for it.
Firstly, if the fault not cleared quickly , it may cause unnecessary interruption of the
service to the customer. Secondly, rapid disconnection of faulty apparatus limit the
amount of damage to it and prevent the effects of fault from spreading into the
system.

The detection of fault and disconnection of faulty part can be achieved by using
fuses or relays in connection with circuit breakers. A fuse can perform both the
function but for low voltage circuit only. For high voltage circuits, relays and circuit
breakers are employed to serve the desire function for automatic protective gear.

Other protective devices are MCB, MCCB, MPCB, ELCB, RCCB, Relay, Isolator
 General items required as per load
 PVC wires: Generally 4.0 mm2, 2.5 mm2, 1.5 mm2, 1.0 mm2, 0.75

 Distribution Board: 6 Way, 8W, 10W, 12W, 16W

 MCB’s: 6 AMP,10A, 16A, 20A, 25A, 32A, (SP/SPN)

 RCCB or ELCB: 16A, 25A, 32A

 Switches: 6Amp, 16 Amp, 20 Amp

 Sockets: 5 Pin 6 Amp, 6 Pin-16Amp, 20A, 25A, 32A

 2-Way Switch: 6 Amp

 Various loads in rooms

 DP Isolator, etc.
 6A switch is used for all light points, fan points, etc.

 6A, 5-pin socket is used for refrigerator, Iron, washing machine, LED TV,

chimney, exhaust fan, charging mobile, etc.

 16A/20A switch and 16A/20A 6-pin socket is used for geyser point, high

rating washing machine, AC load etc.

 2way switches are used for stair case light control and entry gate

lights.

 All accessories should be of ISI marked, branded bearing good look and as

per choice of owner.

General Requirements of Electrical Installation
1. Layout wiring
2. Conductors
3. Rating of lamp, fan and socket outlet point
4. Reception and distribution of main supply
5. Arrangement of apparatus on switchboards
6. Single phase supply/ Three phase four wire supply
7. Distribution board
8. Sub circuits
9. Service connection
1. Layout Wiring

2. Conductors
4. Reception and distribution of main supply

 At the entry level there should be a circuit breaker or linked switch

on live conductor.

 No break in the neutral wire in the form of switch or fuse

throughout the installation

 All main switches should be either metal clad enclosed or of any

insulated enclosed pattern and should be fixed at close proximity to
the point of entry of supply.
4. Reception and distribution of main supply
5. Arrangement of Apparatus on Switchboards
6. Single Phase Supply

The consumer’s main switch fuse is connected after the meter and feed a
distribution fuse board. It is important to note that fuses should be connected
only in live wire and never in the neutral wire. Similarly all switches installed
on live wire only and never on the neutral wire.
Simple Diagram of Single Phase Installation
Single Phase Installation with a number of sub-distribution boards
having a common main switch fuse
Single Phase Installation with a number of sub-distribution boards each
connected to the mains through a separate fuse
9. Service Connection
 The line bringing electric power from supplier’s low voltage distribution up
to the energy meter installed at the consumer’s premises is called the service
connection.
 The electric supply authority supplies power to the consumers through a low
voltage three phase four wire distribution system called the secondary
distribution system.
 Large consumers supplied at higher voltages through three-wire high voltage
distribution system called the primary distribution system (6.6, 11, 33 kV)
 Service connection may be by mean of underground cables or by mean of
overhead conductors or cables.
Overhead Service Connection
This system is used when the consumer’s premises are more than
45 meter away from the supplier’sdistribution pole.
a) PVC or weather proof cable service line
b) Bare conductor service line
Estimating and Costing of Electrical Installation
• Quantity and specification of material
• Price list
• Labour charges
• Overhead charges
• Contingencies
• Profit purchase system
 Electrical Installations for Residential
building: Estimating and Costing of Material

• Choice of particular type of wiring depending upon a particular

use, financial implication and personal preferences.
• Installation work should be as per Indian Electricity Rules 1956.
• The planning and designing of electrical wiring should be done
before civil work start.
• Layout of electrical wiring prepare in advance and handed over
the civil engineer to make necessary provisions in the building
for electric work.
Example of Estimating and Costing of materials
Installation Plan
Schematic and Wiring Diagram
Electrical Installations for Commercial Building

Electric service and supply

• Supply authority supplies power to the consumer through low
voltage i.e. 415V/240V three phase four wire distribution
• Large consumers are supplied at higher voltage: 6.6, 11, 33 kV
three wire high voltage feeder
 Internal Distribution
• Small residential installation
• Medium Large Installation
• Large Installation
Large Installation