Electrical wiring is an electrical installation of cabling and associated devices such as switches, distribution boards, sockets and light fittings in a structure. Wiring is subjected to safety standards for design and installation. Allowable wire and cable types and sixes are specified according to the circuit operating voltage and electric current capability, with further restriction on environmental conditions ,such as ambient temperature range, moisture levels, and exposure to sunlight and chemicals .

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KSRM COLLEGE OF
ENGINEERING ,KADAPA.
_________________________
ELECTRIACAL WIRING IN DOMESTIC AND
INDUSTRIES
Contents :
Introduction
1.Electrical power supply wiring.
2.Domestic electric circuits.
3.Domestic wiring .
4.Sub-circuits in domestic wiring.
5.Methods of wiring.
6.Industrial Electrification .
7.Types of installation.
8.Electrical installation for power circuits.
INTRODUCTION :
Electrical wiring is an electrical installation of cabling and
associated devices such as switches, distribution boards,
sockets and light fittings in a structure. Wiring is subjected to
safety standards for design and installation. Allowable wire and
cable types and sixes are specified according to the circuit
operating voltage and electric current capability, with further
restriction on environmental conditions ,such as ambient
temperature range, moisture levels, and exposure to sunlight
and chemicals .
Associated circuit protection, control and distribution devices
within a building’s wiring system are subject to voltage, current
and functional specification. It is necessary to select proper
type of wiring scheme for the domestic purpose. Thus a

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network of wires connecting various accessories for distribution
of electrical energy from the supplier meter board to the
numerous electrical energy consuming devices through
controlling and safety devices is known as Electrical wiring.
Electrical power supply wiring
Fig(1):Electrical power transmission from electric pole to
energy meter to distribution board

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Domestic electric circuits:
1.Electric power is usually generated at places which are far
away from the places where it is consumed . At the generating
station, the electric power is generated at 11KV volts . This
voltage alternates at a frequency of 50HZ.
2.The power is transmitted over a long distance at high
voltages to minimize the loss of energy in the transmission.
3.The electric power line enter our house through three wires -
namely the live wire, the neutral wire and the earth wire.
4.To avoid confusion we follow a colour code for insulating
these wires.
5.The ted wire is the live wire, and the black wire is neutral,
the earth wire is given green plastic insulation.
Domestic wiring
1.The live wire has a high potential of 220V whereas the
neutral wire has zero potential .Thus the potential difference
between the live wire and the neutral wire is 220-0=220V.
2.The earth wire is much thicker in size and is made of copper.
One end of it is connected to a copper plate buried deep under
the earth. The earth connection is made to the electric meter
and then the main switch.
Fig(2):simple circuit of domestic wiring.
3.In case o short circuit occurs in the power circuit ,then the
power fuse will below off but our lights will continue to burn as
the lighting circuit remains unaffected.
4.A constant voltage of the main line is available for all other
electrical appliances.

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5.There are two separate circuits in a house namely lighting
circuit and power circuit . The lighting circuit with a 5A fuse is
used for running electric bulbs ,fans, tube lights etc…
Sub-circuits in domestic wiring
It is Broadly classified into two categories:
1.Light , Fan sub-circuit
2.Power sub-circuit.
(1) Light and Fan Sub-circuit:
The sub-circuit of the electrical installation feeding supply to
various light points, i.e. lamps, Lighting cable, Light switches,
tubes etc. and to fan points is termed as light and fan sub-circuit
respectively.
(2) Power circuit:
The part of the complete installation that supplies appliances
like hot plate , electric iron ,small single-phase motors of
washing machine , refrigerator etc. is generally called the power
sub-circuit.
Methods of wiring
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) can be done using two
methods which are,
I. Joint box system or Tee system or Jointing system
II. Loop – in system
I. Joint box system or Tee system of Jointing system:
1.In this method of wiring, connections to appliances are made
through joints.
2.These joints are made in joint boxes by means of suitable
connectors or joints cutouts.
3. This method of wiring doesn’t consume too much cables size.
4.This method is suitable for temporary installations and it is
cheap.

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II. Loop-in or Looping System:
1.This method of wiring is universally used in wiring.
2. Lamps and other appliances are connected in parallel so that
each of the appliances can be controlled individually.
3. When a connection is required at a light or switch, the feed
conductor is looped in by bringing it directly to the terminal and
then carrying it forward again to the next point to be fed.
Advantages and Disadvantages of Loop-In Method
Advantages :
1.It doesn’t require joint boxes and so money is saved
2.In loop – in systems, no joint is concealed beneath floors or in
roof spaces.
3.Fault location is made easy as the points are made only at
outlets so that they are accessible.

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Disadvantages :
1Length of wire or cables required is more and voltage drop and
copper losses are therefore more.
2.Looping – in switches and lamp holders is usually difficult.
Industrial Electrification
Is the process of powering by electricity and in many contexts
,the introduction of such power by changing over from an
earlier power source.
Even the smallest interruptions can cause huge losses to all
industries served in terms of productivity and profitability.
So availability of quality power is most important for industries.
i] It should produce sufficient illumination on the working
plane.
ii] It should provide uniform distribution of illumination.
iii] It should avoid glare and shadows.
iv] It should be easy to clean.
Types of installations
1.General Lighting:
1.Under this scheme general lighting should be provided such
that there will be uniform distribution of light over the working
plane.
2.In such cases, the color of walls and surroundings are selected
in such a way that it adds effectiveness to the Illumination.
Generally White color is preferred.
2.Local Lighting:
1.There are certain locations where fairly intense illumination is
required.
To provide sufficiently more illumination for such locations, local
lighting is provided.
2.Local lighting is provided by means of adjustable fittings
attached to the working plane and lamps are mounted on
reflectors to avoid the glare.

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3. Emergency Lighting:
1.There are some applications where emergency lighting has to
be provided such as:
2.Control posts , first aid Centre and speedy evacuation of
personnel after main lighting circuit is off.
Electrical installation of power circuits
1.According to Indian Electricity Rules(No. 50 and 51), the wiring
of electrical motors in industries is to be carried out apart from
meeting local requirements on various conditions.
2.Design consideration in case of motor wiring installation is
different from that of the lighting wiring installation. In case of
lighting load, size of the conductor l wire is decided on the total
current of the load.
3.But in case of motor wiring, size of the conductor should not
be less than corresponding to 3% of the motor full load current.
4.The reason is that conductor should be capable of withstanding
the starting current of the motor which is generally 5 to 7 times
the full load current.

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Fig(5):Electrical installation of power circuits
1.Each motor takes a high current at the starting which may be
5 to 7 times full load current of the motor.
2. Hence, to limit the voltage drop in the cable as well as to limit
huge starting current, a separate starting device, called starter
is used for each motor. Starter is located after the motor switch.
3.In domestic installations, single earthing is sufficient but in
workshops or factory , double earthing is necessary from the
extra safety point of view.
4.Calculate the full load current rating of the all resistive loads.
5.Add to this 125% of full load current of the highest rated
motor.
Reference Books:
1.Practical electrical wiring :Residential , farm, commercial and
industrial.
Authors : Herbert P Richter , W . Creighton Schwan
Publisher : McGraw-Hill,1996.