UNIT 2 FIRE SAFETY

Mechanism of fire spread in building and prevention – Fire

safety standards – Concepts in fire protection – Firefighting
installation and requirements - Heat sensitive detectors –
Smoke detectors –Automatic water sprinkler system- Foam
systems.
The Fire Triangle

AIR or
OXYGEN Fire or combustion will continue as long
as these three factors (heat, oxygen(or
air) and a combustible substance (or
fuel)are present. Removal of one of
FIRE
them leads to the collapse of the
FUEL
HEAT (Combus triangle and the combustion process
tible
material) stops.

There are three (3) components required for combustion to occur:

 Fuel – To vaporize and burn
 Oxygen – To combine with fuel vapor
Heat – To raise the temperature of the fuel vapor to its ignition
temperature
There are two important factors to remember in preventing and extinguishing
a fire:
 If any of the three components are missing, then a fire cannot start.
 If any of the three components are removed, then the fire will go out.

Fire Safety
Fire spread depends on the principal methods of heat transfer: conduction, convection,
radiation and direct burning.

Fire Safety
Building Hazards:
Fire can spread rapidly through a building,
causing major structural failure of
roofs and walls. Depending on a building's
design, fires can travel horizontally
and vertically. Listed below are examples of
how fire can travel throughout a
building:

Horizontal Travel
• Doorways
• Hallways
• Ceiling spaces •The building's structural materials will determine its
• Floor spaces ability to withstand a fire.
• Utility openings •Structural framing of wood is considered to have a
• Conveyor shafts limited resistance to fire.
Vertical Travel •Steel members are subject to significant structural
• Stairways decreases at low fire temperatures unless they are
• Elevator shafts protected by enclosures or treated with fire-resistive
• Material shafts chemical coatings.
• Utility openings
• Conveyor shafts
Fire Safety
 Smoothering-Removal of oxygen from
the scene of fire is called as Smoothering.
by using CO2,DCP (Dry Chemical Powder-
breaks down the chemical reaction within
the fire and suppresses the flames almost
immediately) fire extinguisher.
Sometimes combustible material can
be removed such as by shutting off
gas valves or fuel flows.
 Cooling-Removal of heat from the
scene of fire is called as cooling by
water, foam extinguisher

 Starvation-Removal of fuel from the

scene of fire is called as Starvation
by cutting fuel supply

 Chain breaking- Brake the chain

by DCP,blanketing

Fire Safety
NATIONAL BUILDING CODE (PART 4) – FIRE AND LIFE SAFETY
As a major development, BIS has published NBC (Part 4) Fire Protection which includes comprehensive
recommendation of minimum standards of fire protection. It specifies the demarcation of fire zones, restrictions on
construction of buildings in each fire zone, classification of buildings based on occupancy, types of building construction
according to fire resistance of the structural and non-structural components and other restrictions and requirements
necessary to minimize danger to life from fire, smoke, fumes or panic before the building can be evacuated. The Code
recognizes that safety of life is more than a matter of means of exits and accordingly deals with various matters which are
considered essential to the safety of life.
As per NBC,High Rise Building - A building 15 m or above in height (irrespective of its
occupancy). Additional Fire Protection Requirements for High Rise Buildings – 15 Metre in height
or above
CONSTRUCTION
All materials of constructions in load bearing elements, stairways and corridors and facades shall be non-combustible.
LIFTS
Walls of lift enclosures shall have a fire rating of 2 h; lifts shafts shall have a vent at the top of area not less than 0.2 sq.m.
FIRE LIFTS
To enable fire services personnel to reach the upper floors with the minimum delay, one fire lift per 1200 sq.m of floor
area shall be provided and shall be available for the exclusive use of the firemen in an emergency.

BASEMENTS
Each basement shall be separately ventilated. Vents with cross-sectional area (aggregate) not less than 2.5 percent of the
floor area spread evenly round the perimeter of the basement shall be provided in the form of grills, or breakable stall
board lights or pavement lights or by way of shafts.

2-hour fire rating means that the walls

and ceiling are able to withstand flames
for 2 hours before they fail.
Fire Safety
NATIONAL BUILDING CODE (PART 4) – FIRE AND LIFE SAFETY
SERVICE DUCTS/SHAFTS
Service ducts and shafts shall be enclosed by walls of 2 h and doors of 1 h, fire rating. All such ducts/shafts shall be properly sealed and
fire stopped at all floor levels.

REFUGE AREA
Provisions contained in IS 1644 shall apply for all buildings except multi-family dwellings, refuge area of not less than 15sq.m shall be
provided on the external walls.

ELECTRICAL SERVICES
The electric distribution cables/wiring shall be laid in a separate duct. The duct shall be sealed at every floor with non-combustible
materials having the same fire resistance as that of the duct. Low and medium voltage wiring running in shaft and in false ceiling shall run
in separate conduits;

GAS SUPPLY
Provisions for gas pipe installations, given in codes to be followed.

ILLUMINATION OF MEANS OF EXIT

Staircase and corridor lights shall conform to the requirements of IS 1644. A stand-by generator shall be installed to supply power to
staircase and corridor lighting circuits, fire lifts, the stand-by fire pump, pressurization fans and blowers, smoke extraction and damper
systems in case of failure of normal electric supply.

TRANSFORMERS
It shall conform to the requirements of IS 1646.

AIR-CONDITIONING
The ducting shall be constructed of substantial gauge metal in accordance with good practice IS 9583.

PROVISION OF FIRST-AID FIRE FIGHTING APPLIANCES

The first-aid fire fighting equipment shall be provided on all floors, including basements, lift rooms, etc, in accordance
with relevant Indian Standards in consultation with the Authority. Fire Safety
NATIONAL BUILDING CODE (PART 4) – FIRE AND LIFE SAFETY
FIRE ALARM SYSTEM
All buildings with heights of 15 m or above shall be equipped with manually operated electrical fire alarm (MOEFA) system and
automatic fire alarm system in accordance with IS 2189.

LIGHTNING PROTECTION OF BUILDINGS

The lightning protection for buildings shall be provided as given in Part 8 Building services, Section 2 Electrical installations of NBC.

FIRE CONTROL ROOM

For all buildings 15 m in height or above and apartment buildings with a height of 30 m and above, there shall be a control room on
the entrance floor of the building with communication system (suitable public address system) to aid floors and facilities for receiving
the message from different floors.

COMPARTMENTATION
The building shall be suitably compartmentalized so that fire/smoke remain confined to the area where fire incident has occurred and
does not spread to the remaining part of the building.

MATERIALS FOR INTERIOR DECORATION/FURNISHING

The use of materials which are combustible in nature and may spread toxic fume/gases should not be used for interior
decoration/furnishing, etc.
In the formulation of Indian standards, the approach adopted is as follows:
1)Fire Prevention —Covering aspects of fire prevention pertaining to planning, design and construction of buildings on passive fire
protection measures, also describing the various types of building materials and their fire rating.

2)Life Safety —Covering life safety provisions in the event of fire and similar emergencies, also addressing construction and occupancy
features that are necessary to minimize danger to life from fire, smoke, fumes or panic.

3)Fire Protection — covering the significant appurtenances and their related components and guidelines for selecting the correct type
of equipment and installation meant for fire protection of the building, depending upon the classification and type of the building.

Fire Safety
Fire Safety
NATIONAL BUILDING CODE (PART 4) – FIRE AND LIFE SAFETY
FIRE ZONES
Group A Residential fall under fire Zone No 1.
The purpose is to demarcate the city into different zones based on fire hazard.

Fire Safety
For the purpose of the Code, the types of construction according to
fire resistance shall be classified into four categories, namely
Type 1 Construction The fire resistance ratings for various types of construction for
Type 2 Construction structural and non-structural members shall be as given in Table -1
Type 3 Construction
Type 4 Construction

Fire Safety
NATIONAL BUILDING CODE (PART 4) – FIRE AND LIFE SAFETY

FIRE PROTECTION
Fire Safety
Fire Safety
Fire Safety
Fire Safety
Fire Compartment - A space within a building that is enclosed by fire barrier or fire
resistant walls on all sides, including the top and bottom.
Means of Egress - A continuous way of travel from any point in a building or structure to a
public way, consisting of three separate and distinct parts, that is, exit access, exit and exit
discharge.
Means of Escape - A way out of a building or that does not conform to the strict definition
of that does not conform to the strict definition of ‘means of Egress’but does provide an
alternate way out.

Fire Safety
Fire Safety
Fire Safety
What is a Fire Detection System?

Fire detection systems serve a simple purpose to spot fires early enough to allow
for safe evacuation of personnel and, if possible, for a quick response to put the
fire out.
• With the right fire detection system, the human and equipment costs due to
damage can be significantly reduced.
• Electronic detection systems most commonly work with alarms to immediately
notify those in the vicinity or connected to a monitoring system.
• This provides warning of a fire to building occupants and can provide
information to emergency responders on the location of the fire, speeding the
process to control the fire.
• Other forms of fire detection do not require power, like pneumatic detection
tubing.
• The tubing is installed inside and throughout areas that have a higher risk of
fire.
• When a fire is present, the tubing will burst open at the point of contact,
indicating a fire, and discharge the fire suppression agent.

Fire Safety
https://www.firetrace.com
What is Fire Protection?

A fire protection system aims to protect a building’s occupants while minimizing the
damage associated with fire.

What are the types of fire protection systems?

• Fire protection systems can be categorized as either active or passive.

• Where active systems actively help fight fires with alarms to call in support or
trigger sprinklers to stop a fire before it gets out of control.

• Passive fire protection involves design like walls and structural supports to
minimize flammability and the spread of smoke.

Passive fire protection is a broad umbrella with many underlying tactics. Apart from
preventing the spread of fire, it also helps to maintain a building’s structural
integrity.

Fire Safety
Passive fire protection
Here are some of the most critical elements of a passive fire protection strategy:
Compartmentation
• To stop smoke from passing through these areas, specialists install fire doors, walls,
and cavity barriers.
• Fire protection boards also play a significant role in compartmentalizing a fire by
preventing it from spreading to new areas.
• They’re designed to absorb heat rather than conduct it and don’t shrink when
exposed to high temperatures.
• If a fire breaks out in a certain compartment, the fire integrity and insulation of the
surrounding compartment helps to confine high temperatures and smoke to the
specific area.

Intumescent Paint
• Intumescent paint is applied to steel support beams as another method of protecting
critical support structures from heat and fire damage.
• This special kind of paint will expand in temperatures over 500 degrees Celsius.
• This adds a new protective layer to the steel, minimizing its exposure to heat and
delaying its degradation.
• Intumescent coatings can withstand high heat for up to two hours—which could
mean the difference between a safe evacuation and a tragic disaster. Fire Safety
What is Fire Suppression?

• The sole objective of a fire suppression system is to extinguish or suppress a fire

as quickly as possible.
• A fire suppression system is built to extinguish fires through the application of a
fire suppression agent like water, foam, or chemical agents.
• These systems are commonly designed with components to detect factors like
extreme heat, smoke, or fire to trigger a response.
• Electronic fire detection is attached to an alarm system that will alert you when
the fire has been detected and initiate steps to further suppress the fire.
• In contrast, non-electronic systems will activate and deploy the fire suppression
agent without notification.
• The majority of fire suppression systems will automatically release the
suppression agent to extinguish the fire after the detection and/or alert.
• Alternatively, some fire suppression systems require someone to manually
release a suppressant.

Fire Safety
Fire Safety
Fire Safety
FIRE SAFETY STANDARDS:MICRO LEVEL PASSIVE MEASURES

Areas of passive Fire Protection:

There are four main areas of passive fire protection.

Structural fire protection. Structural fire protection guards essential structural components
(such as structural steel and joint systems) from the effects of fire. This is accomplished
with a fireproofing material (spray-on thin-film intumescent, endothermic materials like
gypsum-based plasters and cementitious products, mineral wool wraps and insulation, and
fireproofing cladding)

Compartmentation. Fire barriers, firewalls, fire partitions, and smoke barriers are all
included in compartmentation. Fire barriers include fire-rated walls, floors, and ceilings
(often made of concrete, combination wood, gypsum, or masonry). These barriers are used
to limit the spread of fire in a building and allow safe egress

Opening protection. Fire doors and windows are installed in an opening of a fire barrier to
maintain its fire resistance.

Fire stopping materials. these materials are used to limit fire spread through penetrations in
a fire barrier.
Fire Safety
Fire Safety
Fire Safety
Fire Safety
https://youtu.be/cVjyDgFrb2g Fire alarm system Fire Safety
Fire Safety
Fire Safety
Fire Safety
Fire Safety
Fire Safety
Fire Safety
Fire Safety
Fire Safety
Fire Safety
Fire Safety
Fire Safety
Fire Safety
Fire Safety
Fire Safety
Fire Safety
Fire Safety
FIRE SAFETY STANDARDS: COMMERCIAL

Fire Safety
FIRE SAFETY STANDARDS: COMMERCIAL

Fire Safety
Single/Three phase supply– Protective devices in electrical
installation – ISI Specifications - Types of wires, Wiring
systems and their choice –Planning electrical wiring for
building interiors – Main and distribution boards- Typical
Electrical layout for interiors.
 There are two kinds of current electricity:
direct current (DC) and alternating current (AC).
With direct current, electrons move in one
direction.
Alternating Current (AC) is a type of electrical
current, in which the direction of the flow of
Power electrons switches back and forth at regular
Triangle intervals or cycles. Current flowing in power lines
and normal household electricity that comes
from a wall outlet is alternating current. The
standard current used in most other parts of the
world it is 50 cycles per second (i.e. a frequency
of 50 Hz.).
Direct current (DC) is electrical current which
flows consistently in one direction. The current
that flows in a flashlight or another appliance
running on batteries is direct current.
One advantage of alternating current is that it is
relatively cheap to change the voltage of the
current.
GENERATOR
It is a machine used to change the mechanical energy into electrical energy. There are
two types of electric energy produced by generators they are DC & AC

DC – Direct Current

Constant current flow rate induced by a

constant voltage
It is not used commonly because of high
current with which it is produced has to
be sent through conductors which has no
transformers and it requires
o Large diameters which are costly
o Power loss in the conductors is tolerated for a Vertical transportation
Usag e Vehicles
short distance HVAC-motors &
It is used in places where compressors
RPM(revolutions per minute ) is properly Electroplating

utilized using DC motors

 It is directly sent to consumers
through thick conductors.
GENERATOR
AC –ALTERNATING CURRENT

It is produced by an ac generator known as alternator.

 In ac circuits the electrons are causing the current to move in one direction,
then in the reverse direction, therefore ,the current changes direction many
times ,that is why it is called alternating current.

 the changes from (+) half cycle to (-) half cycle and back to (+) half cycle
constitutes a full cycle.

 It does not produce RPM & cannot be stored in batteries.

 It can serve consumers over 100 miles apart.

 Today the bulk of electricity used is this.

ELECTRIC CURRENT
An electric current is a flow of electric charge. In
electric circuits this charge is often carried by
moving electrons in a wire. It can also be carried by
ions in an electrolyte, or by both ions and electrons
such as in a plasma.
Electrical current consists of a flow of electrons
along a conductor.

ELECTRIC CIRCUIT
When electricity flows from one point to
another along a closed path (a wire, for
example), the electrons flow
from a point with a negative charge to one with a
positive charge. Any closed path followed by an
electrical
current is called a circuit. Unit -Ampere
SOURCE
Supply Energy to a system
LOAD
Accept Energy from a system
ELECTRIC SUPPLY SYSTEM.

The conveyance of electric power from a power station to consumers’

premises is known as electric supply system. An electric supply system consists
of three principal components.

POWER STATION
THE TRANSMISSION LINES
AND THE DISTRIBUTION
SYSTEM.
Each part can be further sub-
divided into two—
•PRIMARY TRANSMISSION
•SECONDARY TRANSMISSION
•PRIMARY DISTRIBUTION
• SECONDARY DISTRIBUTION.
Transformer-Static power transfer device

A transformer is a passive electrical device that transfers electrical energy from

one electrical circuit to another, or multiple circuits. A varying current in any one
coil of the transformer produces a varying magnetic flux in the transformer's
core, which induces a varying electromotive force across any other coils wound
around the same core.

Transformers are most commonly used for increasing low AC voltages at high
current (a step-up transformer) or decreasing high AC voltages at low current (a
step-down transformer) in electric power applications, and for coupling the
stages of signal-processing circuits. Transformers can also be used for isolation,
where the voltage in equals the voltage out, with separate coils not electrically
bonded to one another.
Types Of Supply:

Single and three phases.

Single phase supply : (phase & neutral) Normally small buildings are
supplied with electricity by two wires, one phase wire and the other
neutral. This gives a voltage for the premises of 230 volts.(between phase
and volt)
-Voltage current (Phase quantity)

Three phases Supply: Four wire(Three Phase Wire and One Neutral)
between any two phases brings around 415 volts. Electric motor are
usually designed for three phase operation.
Voltage current (Line quantity)
The three phase lines and the neutral Single phase Three phase
together give a 3-phase 4-wire supply Voltage drop Voltage stability(load
with a RMS voltage of 240√3 = 415V. balanced)
Current Less Current
consumption more consumption
compare to 3 phase
Losses more (copper Losses less
and conductor loss)
Line voltage is the voltage measured between
any two lines in a three-phase circuit.(Three
phases)
Phase voltage is the voltage measured across a
single component in a three-phase source or
load.(Single phase)
In electric power
distribution,
a busbar (also bus bar) is
a metallic strip or bar,
typically housed inside
switchgear, panel boards,
and busway enclosures
for local high current
power distribution.
Busbars are metal bars
used
to carry large amounts of
current. Often made of
copper or aluminum,
every home electrical
panel has busbars to
distribute ac power to
the rows of circuit
breaker.
The circuit protection device is an electrical device used for
preventing an unnecessary amount of current otherwise a
short circuit.

Different types of Protection Devices

The different types of circuit protection devices examples include
the following. Fuse
Circuit Breaker
Lightning
Arrester

Fuse: In electrical circuits, a fuse is an electrical device used to

protect the circuit from overcurrent. It consists of a metal strip that
liquefies when the flow of current through it is high. Fuses are
essential electrical devices, and there are different types of fuses
available in the market today based on specific voltage and current
ratings, application, response time, and breaking capacity.
The characteristics of fuses like time and current are selected to
give sufficient protection without unnecessary disruption.
 Circuit Breaker
A circuit breaker is one kind of electrical switch used to guard an
electrical circuit against short circuit otherwise an overload which
will cause by excess current supply. The basic function of a circuit
breaker is to stop the flow of current once a fault has occurred. Not
like a fuse, a circuit breaker can be operated either automatically or
manually to restart regular operation.
Circuit breakers are available in different sizes from small devices to large switch gears
which are used to protect low current circuits as well as high voltage circuits.

MCB(miniature circuit breaker) A miniature circuit breaker is used in new

constructions instead of the older types of
A MCB is a manually or automatically
fuses. • The miniature circuit breaker is
operated electrical switch designed to
designed to protect the house from circuit
protect an electrical circuit from
overload. • Miniature circuit breaker can be
damage caused by overload or short
used with ground fault, or arc fault
circuit. Its basic function is to detect a
mechanisms, because the breakers consist of
fault condition and interrupt current
a system that opens the contacts if a line to
flow
ground fault occurs. • Using miniature circuit
breakers in the lighting system of the house,
because they can deal with the amount of
power needed to light a house, especially if
using specific types of lamps, such as
fluorescent lights.
Lightning Protection of Buildings
Type of Construction
Importance of Structure
The type of construction of the
The lightning hazard to human beings
structure has a large influence upon
within a structure or a building is a very
the extent of protection to be
important factor in deciding how far to go
provided. A steel framed building to
in providing lightning protection. Schools,
some extent is self-protecting and
hospitals, auditoriums, railway stations,
may not generally require additional
etc., are places where a large number of
protection, while brick buildings or
people congregate and, therefore, would in
buildings with thatched roof require
general be structures of greater
greater degree of protection.
importance than small buildings and
houses.

The lightning protection

system protects the facility against a
direct lightning strike. Only adequately
arranged lightning conductors and
components will be able discharge the
lightning current in the event of a
direct lightning strike.
Lightning Protection of Buildings
Air terminations
provide a critical
role in the
lightning
protection
system, capturin
g the fullness of
the lightning
strike current
and channeling
this current
safely to the
conductor
network to
protect buildings
and substations.
 Earthing (grounding)

Earthing or grounding is the process of

transferring the immediate discharge of
electricity directly to
the earth plate, by means of low resistance
electrical cables or wires.
Purpose of earthing:
Earthing is used to protect you from an electric
shock. It does this by providing a path (a protective
conductor) for a fault current to flow to earth. It
also causes the protective device (either a circuit-
breaker or fuse) to switch off the electric current
to the circuit that has the fault.

Ground or earth in a mains (AC power) electrical wiring system is a

conductor that provides a low-impedance path to the earth to prevent
hazardous voltages from appearing on equipment (high voltage spikes).

Neutral is a circuit conductor that normally completes the circuit back to

the source.
 Earthing (grounding)

1. Plate Earthing
2. Pipe Earthing

In this method a copper plate of 60cm x

60cm x 3.18cm or a GI plate of the size
60cm x 60cm x 6.35cm is used for earthing.
The plate is placed vertically down inside
the ground at a depth of 3m and is
embedded in alternate layers of coal and
salt for a thickness of 15 cm.
In addition, water is poured for keeping the
earth electrode resistance value well below
a maximum of 5 ohms. (unit of electrical
resistance) The earth wire is securely bolted
to the earth plate. A cement masonry
chamber is built with a cast iron cover for
easy regular maintenance.
Earthing (grounding)
1. Plate Earthing
2. Pipe Earthing

Earth electrode made of a GI (galvanized) iron

pipe of 38mm in diameter and length of 2m
(depending on the current) To keep the with
12mm holes on the surface is placed upright at a
depth of 2.75m in a permanently wet ground.
value of the earth resistance at the desired level,
the area (15 cms) surrounding the GI pipe is
filled with a mixture of salt and coal. The
efficiency of the earthing system is improved by
pouring water through the funnel periodically.
The GI earth wires of sufficient cross- sectional
area are run through a 12.7mm diameter pipe
(at 60cms below) from the 19mm diameter pipe
and secured tightly at the top.

https://youtu.be/8PTNjw-hQIM -Pipe Earthing

Main Distribution Boards
Power Distribution is a system, consisting of a Main Distribution Board (MDB), Sub Main
Distribution Boards (SMDBs) and Final Distribution Boards, by which the electrical energy is
transmitted via branches to reach the exact end user.
An MDB is a panel or enclosure that houses the fuses, circuit breakers and ground leakage
protection units where the electrical energy, which is used to distribute electrical power to
numerous individual circuits or consumer points, is taken in from the transformer or an
upstream panel. An MDB typically has a single or multiple incoming power sources and
includes main circuit breakers and residual current or earth leakage protection devices. A MDB
is comprised of a free standing enclosure, a bus bar system, MCCB's (high energy requirement
applications such as high-power equipment), metering and support equipment's and required
current transformers. Panels are assembled in a systematic manner such as incomer section
and outgoing section.

Sub-Main Distribution Boards

The MDB then feeds SMDBs, which is installed generally at the point where a large distribution
cable terminates and several smaller sub-circuits start. These are the switchboards that
although similar construction, are larger than a final distribution board circuit. The boards are
installed midway through the power distribution system, at the point in a large distribution
cable ends, and several smaller starting sub-circuits.
Final Distribution Boards
The Sub-Main Distribution Boards feeds the Final Distribution Board, which then feeds
electrical energy to the end user.
Distribution board
Distribution board (also known as panel board
or breaker panel) is a component of an
electricity supply system which divides an
electrical power feed into subsidiary circuits,
while providing a protective fuse or circuit
breaker for each circuit in a common
enclosure.

Domestic Supply
 ELECTRICAL IS CODES
S.NO STANDARDS KEY AREAS
1. IS:732 - 1989 Code of practice for electrical wiring
installations.

2. IS:8061 - 1976 Code of practice for design, installation and

maintenance of service lines upto and
including 650V.

3. IS:2309 - 1989 Code of practice for the protection and

allied structures against lightning.
4. IS:3043 - 1987 Code of practice for earthing.

5. IS:694 - 1990 PVC Insulated cables for working voltages

upto and including 1100 V.

6. IS:3480 - 1966 Flexible steel conduits for electrical wiring.

7. IS: 5216(Part-1)- Guide for safety procedures and practices

1982 in electrical work.

8. IS:8828 - 1978 Miniature air break circuit breakers for

voltages not exceeding 1000 volt.
 Wiring is the network of wires used in an electrical system, device, or circuit.

There are mainly 6 types of wires are:

 vulcanised Indian rubber wire (V.I.R)
 tough rubber sheathed wire (T.R.S)
 poly vinyl chloride wire (P.V.C.)
 Lead alloy sheathed wire
 weather proof wire
 Flexible wire
Vulcanised Indian rubber wire (V.I.R)
A VIR wire mainly consist of a tinned conductor
having rubber coating. Tinning of conductor
prevents the sticking of rubber to the
conductor. Thickness of rubber mainly depends
on the operating voltage to which wired is
designed. A cotton bradding is done over the
rubber insulations to protect the conductor
against the moisture. Finally the wire is finished
with was for cleanliness. In current context we
are using these type of wires since better
quality available in market in cheaper cost
 (or) cab tyre sheathed (CTS) cables.
T.R.S (Tough Rubber Sheathed wires)

This type of wire is modification of VIR wire. It

consist of the ordinary rubber coated
conductors with an additional sheath of tough
rubber. This layer provides better protection
against moisture and wear and tear and also it
provides an extra insulation. These wires are
generally available in single conductor or three
conductor.
PVC (Poly vinyl Chloride) wires
This is the most commonly used wire for
wiring purpose.Conductor is insulated by
PVC material. Properties: Moisture proof,
Tough, Durable, Chemically inert. But it
softens at high temperature therefore not
suitable for connection to heating
appliances.
Lead Alloy Sheathed wires
The ordinary wires can be used only at dry
places, but for damp places these wires are
covered with lead sheaths. The layer of lead
covering is very thin like 0.12cm thick .These
wires provides little mechanical protections
to the wires.
Weather proof wire
These types of wires are
used outdoor i.e. providing
a service connection from
overhead line to the
building etc. In this type of
wire the conductor is not
tinned, and the conductor
is covered with the three
braids of fibrous yarn and
saturated with water proof
compound.
Flexible wires
These wires are very useful
for household portable
appliances where the
flexibility of wire is more
important. Flexibility
contributes to the reliability
of a product and influences
the longevity of cable life in
environments.
ELECTRICITY IN BUILDINGS

SYMBOLS