Electrical & house wiring technician book soft copy

Course
Material
Electrical & House Wiring Technician

1 | P a g e
Electrical & House wiring technician
Table of Contents
1. Electrical safety................................................................................................... 4
Introduction ........................................................................................................................... 4
Electrical safety...................................................................................................................... 4
Handling electrical fires ......................................................................................................... 6
Artificial respiration ............................................................................................................... 8
Artificial respiratory resuscitation ......................................................................................... 9
Resuscitate an accident victim............................................................................................. 10
Other steps........................................................................................................................... 17
2. Use of workshop tools ...................................................................................... 18
Hammers and nails .............................................................................................................. 18
Chisels: ................................................................................................................................. 19
Saws ..................................................................................................................................... 20
Drilling.................................................................................................................................. 21
Hand operated wire stripping tools..................................................................................... 22
Hand tools for skinning -auto-eject stripper........................................................................ 23
3. Basics of electrical engineering ......................................................................... 24
Circuit................................................................................................................................... 24
Voltage................................................................................................................................. 24
Current................................................................................................................................. 24
Power................................................................................................................................... 25
Energy .................................................................................................................................. 26
A.C. alternating current ....................................................................................................... 26
Cycle..................................................................................................................................... 26
Frequency ............................................................................................................................ 26
Direct Current ...................................................................................................................... 27
Three Phase Supply.............................................................................................................. 27
Materials & Components..................................................................................................... 28
Insulators.............................................................................................................................. 29
Resistances........................................................................................................................... 29
Inductance ........................................................................................................................... 29

2 | P a g e
Capacitance.......................................................................................................................... 30
Connections of components................................................................................................ 30
The Ohm’s Law..................................................................................................................... 31
Units of measurement for voltage....................................................................................... 33
4. Domestic wiring................................................................................................ 34
Planning for wiring............................................................................................................... 34
Load estimation ................................................................................................................... 34
Wattages of domestic appliances:....................................................................................... 36
Wire selection chart............................................................................................................. 37
Symbols (IS:732 – 1989)....................................................................................................... 38
Indian standards FOR FITTINGS and accessories................................................................. 40
Electrical accessories ........................................................................................................... 41
Making electrical joints........................................................................................................ 49
Solder copper conductor joints ........................................................................................... 51
Solder a ferrule/sleeve to copper cable .............................................................................. 53
Solder a sleeve to a copper cable joint................................................................................ 55
Solder a lug to a copper conductor...................................................................................... 55
Selection of wiring ............................................................................................................... 57
Method of marking the layout for wiring............................................................................ 59
methods of connections in domestic installations.............................................................. 62
Measure wire sizes............................................................................................................... 64
Cleat wiring .......................................................................................................................... 65
Executing PVC casing-capping wiring................................................................................... 66
3.0 Estimating the cost of house wiring................................................................. 69
4.0 Testing of domestic installation....................................................................... 71
Polarity test.......................................................................................................................... 71
Testing polarity of sockets ................................................................................................... 72
Continuity test...................................................................................................................... 72
Earth leakage current test ................................................................................................... 73
Insulation resistance test..................................................................................................... 73
Checking fuses...................................................................................................................... 74

3 | P a g e
Typical lighting circuits......................................................................................................... 75
Variable master control ....................................................................................................... 77
Assemble and install a fluorescent lamp ............................................................................. 78
Assemble, connect and test the instant start fluorescent lamp ......................................... 80
Assembly and installation of sodium VAPOR LAMP with accessories................................. 82
Connection and installation of Mercury Vapour Lamp with accessories............................ 83
Connect the given neon sign with the accessories and test................................................ 84
5. Transmission and distribution........................................................................... 86
Power system....................................................................................................................... 86
Distribution .......................................................................................................................... 87
Systems of A.C. distribution................................................................................................. 88
Corona.................................................................................................................................. 89
Sag........................................................................................................................................ 90
Skin effect ............................................................................................................................ 90
Effect of temperature on resistance.................................................................................... 91
Supporting structures .......................................................................................................... 91
6. Insulators.......................................................................................................... 96
String efficiency.................................................................................................................... 98
7. Underground cables.......................................................................................... 99
Construction......................................................................................................................... 99
Types of cables...................................................................................................................100
Laying underground cables................................................................................................ 103
Cable terminal boxes .........................................................................................................105

4 | P a g e
1. Electrical safety
INTRODUCTION
As an electrician, you will be required to handle a number of tools, instruments and
equipment. The first and the foremost consideration should be safety. This is particularly
important in case of electrical safety. Even a minor mistake can cause death or severe
burns on the body. It can be dangerous to other persons and cause fire.
Keep the first aid kit ready for immediate use.
ELECTRICAL SAFETY
 Never work in wet/damp places without
proper safety.
 Do not put any metallic articles like finger
rings, bracelets or any other jewellery on your
body while working on electric supply.

5 | P a g e
 Use insulated rubber sole shoes while
working.
 Do not work without any footwear.
Do not use chappals.
 The stairs used while working should be sturdy and
safe. An assistant should be working with you.
 All tools used should be properly insulated and in good working condition.

6 | P a g e
 Always use insulated gloves while working on high voltage electric supply.
 Avoid working on live parts. Switch off supply before working.
HANDLING ELECTRICAL FIRES
All fires are dangerous. They cause damage to property and loss of human lives. Electric
fires are particularly dangerous. An electrician will be required to handle electrical fires. He
must be smart, quick acting and fast in decision making to save damages of any kind.
Sources of electrical fire
The main causes of electric fire are:
1. Loose connections
The loose connection cause sparking which ultimately result in fire. The electrician
must ensure that all the connections are tight and safe.
2. Overload
If the current carries more current than what it is designed for, it may lead to fire.
The ratings of the equipment connected in a circuit should be kept in mind.
3. Use of incorrect rating of fuses
Great care should be taken in selection of fuses. Wrong selection of fuses can be
dangerous.
4. Short circuits

7 | P a g e
Short circuits occur due to failure of insulation, overheating, and use of poor quality
of cables.
Extinguishing the fire
The basic reason of growth of fire should be
understood.
The three things Fuel, Oxygen and Heat
together are responsible for fire. Whenever,
the supply of any one, or, all the 3 is stopped,
the fire will be extinguished. You should keep
this in mind, whenever the fire is to be
extinguished.
The fires are classified under categories A,B,C, D and E for different types of fires. Ensure
that the extinguisher, you are using is suitable for electrical fire. It will be written on the Fire
extinguisher.
Carbon dioxide, dry power and vaporizing liquid (CTC) extinguishers can be used to deal with
electric fires.
Caution:
Foam or liquid (water) extinguishers must not be used to quench electric fires. It can be
dangerous and user can get shock.
Always read and understand the operating instructions before using a Fire extinguisher.

8 | P a g e
ARTIFICIAL RESPIRATION
Isolating a person from a live supply
 Remove the victim safely from the
'live' equipment by disconnecting
the supply or by using anyone of the
available insulating material.
 Do not run to switch off the supply
that is far away.
 Do not touch the victim with bare
hands until the circuit is made dead
or the victim is moved away from
the equipment.
 Push or pull the victim from the
point of contact of ‘live’ equipment
without causing serious injury to the
In case of fire:
 Do not panic. Be calm.
 Switch off the electric supply immediately.
 Raise an alarm to let others know about the accident.
 Evacuate persons from the area of safety.
 Use Fire extinguishers as advised in Operating instructions.

9 | P a g e
victim by using rubber gloves to
hold him.
 Move the victim physically to a
nearby place.
 Check for the victim's natural
breathing and consciousness.
 Take steps to apply respiratory
resuscitation if the victim is
unconscious and not breathing.
ARTIFICIAL RESPIRATORY RESUSCITATION
1. Loosen the tight clothing of the victim. If not possible to loosen quickly, do not spend
time in this activity.
2. Remove obstructions from the mouth, if any.
3. Send word for professional assistance. (If no other person is available, you stay with
the victim and render help as best as you can.)
4. Look for visible injuries in the body and decide suitable method of artificial
respiration.
In the case of injury / burns in chest and / or belly, follow the mouth-to-mouth method of
resuscitation.
In case the mouth is closed tightly, use Schafer’s method or Nelson’s method explained
later.
In case of burn and injury in the back, follow Nelson’s method.
5. Put the victim in the correct position for applying artificial respiration.
All actions should be taken immediately. Delay even by a few seconds may be dangerous.
Keep the patient quiet and be careful to prevent injury to internal organs.
6. Place the victim in the recovery position.
7. Cover the victim with coat, sacks or improvise your own method, to keep the victim's
body warm.

10 | P a g e
RESUSCITATE AN ACCIDENT VICTIM
PROCEDURE
Prepare the victim, who is suffering from a cardiac arrest, to receive artificial respiration.
1. Remove the victim from contact with the live wire equipment, taking
necessary safety measures.
2. Loosen the tight clothing which may interfere with the victim's breathing.
3. Remove any foreign materials or false teeth from his mouth and keep the
victim's mouth open.
4. Bring the victim safely to the level ground in case the victim is on a ladder,
post or on the top of an equipment.
5. Start artificial respiration immediately without delay. Do not waste too much
time in loosening the clothes or trying to open the tightly closed mouth.
6. Avoid violent operations to prevent injury to the internal parts of the victim.
7. Send word for a doctor immediately.
Resuscitate the victim by Nelson's arm -Lift back pressure method
Nelson’s arm-lift back pressure method must
not be used in case there are injuries to the
chest and belly.
1. Place the victim prone (that is face down)
with his arms folded with the palms one
over the other and the head resting on
his cheek over the palms. Kneel on one or
both knees near the victim's hand. Place
your hands on the victim's back beyond
the line of the armpits, with your fingers
spread outwards and downwards,
thumbs just touching each other as in Fig.

11 | P a g e
2. Gently rock forward keeping your arms
straight until they are nearly vertical, and
steadily pressing the victim's back as
shown in Fig to force the air out of the
victim's lungs
3. Synchronize the above movement of
rocking backwards with your hands
sliding downwards along the victim's
arms, and grasp his upper arm just above
the elbows as shown in Fig. Continue to
rock backwards
4. As you rock back, gently raise and pull the
victim's arms towards you as shown in Fig
until you feel tension in his shoulders. To
complete the cycle, lower the victim's
arms and move your hands up to the
initial position.
5. Continue artificial respiration till the
victim begins to breathe naturally. Please
note, in some cases, it may take hours.
6. When the victim revives, keep the victim
warm with a blanket, wrapped up with
hot water bottles. Stimulate circulation
by stroking the insides of the arms and
legs towards the heart
7. Keep him in the lying down position and
do not let him exert himself.
Do not give him any stimulant until he is fully
conscious.

12 | P a g e
Resuscitate the victim by Schafer's method.
Do not use this method in case of injuries to
victim on the chest and belly.
1. Lay the victim on his belly, one arm
extended direct forward, the other arm
bent at the elbow and with the face
turned sideward and resting on the hand
or forearm as shown in Fig.
2. Kneel astride the victim, so that his thighs
are between your knees and with your
fingers and thumbs positioned as in Fig.
3. With the arms held straight, swing
forward slowly so that the weight of your
body is gradually brought to bear upon
the lower ribs of the victim to force the
air out of the victim's lungs as shown in
Fig.
4. Now swing backward immediately
removing all the pressure from the
victim's body as shown in Fig thereby,
allowing the lungs to fill with air.
5. After two seconds, swing forward again
and repeat the cycle twelve to fifteen
times a minute.
6. Continue artificial respiration till the
victim begins to breathe naturally.

13 | P a g e
Resuscitate the victim by mouth-to-mouth method
1. Lay the victim flat on his back and place a
roll of clothing under his shoulders to
ensure that his head is thrown well back.
(see figure).
2. Grasp the victim's jaw as shown in Fig,
and raise it upward until the lower teeth
are higher than the upper teeth; or place
fingers on both sides of the jaw near the
ear lobes and pull upward.
Maintain the jaw position throughout the
artificial respiration to prevent the tongue from
blocking the air passage
3. Take a deep breath and place your mouth
over the victim's mouth as shown in Fig
11 making airtight contact. Pinch the
victim's nose shut with the thumb and
forefinger.
If you dislike direct contact, place a porous
cloth between your mouth and the victim's. For
an infant, place your mouth over his mouth and
nose.
4. Blow into the victim's mouth (gently in
the case of an infant) until his chest rises.
Remove your mouth and release the hold
on the nose, to let him exhale, turning
your head to hear the rushing out of air.
The first 8 to 10 breathings should be as rapid as

14 | P a g e
the victim responds, thereafter the rate should
be slowed to about 12 times a minute (20 times
for an infant).
If air cannot be blown in, check the position of
the victim’s head and jaw and recheck the
mouth for obstructions, then try again more
forcefully. If the chest still does not rise, turn the
victim’s face down and strike his back sharply to
dislodge obstructions.
Sometimes air enters the victim’s stomach as
evidenced by a swelling stomach. Expel the air
by gently pressing the stomach during the
exhalation period.
Resuscitate the victim by Mouth-to-Nose method
Use this method when the victim’s mouth will
not open, or has a blockage you cannot clear.
1. Use the fingers of one hand to keep the
victim's lips firmly shut, seal your lips
around the victim's nostrils and breathe
into him. Check to see if the victim's
chest is rising and falling.
2. Repeat this exercise at the rate of 10 -15
times per minute till the victim responds.
3. Continue this exercise till the arrival of
the doctor.

15 | P a g e
Resuscitate a victim who is under cardiac arrest.
In cases where the heart has stopped beating,
you must act immediately.
1. Check quickly whether the victim is under
cardiac arrest.
Cardiac arrest could be ascertained by the
absence of the cardiac pulse in the neck, blue
colour around lips and widely dilated pupil of the
eyes.
2. Lay the victim on his back on a firm
surface.
3. Kneel alongside facing the chest and
locate the lower part of the breastbone.
4. Place the palm of one hand of the center
of the lower part of the breastbone,
keeping your fingers off the ribs.
Cover the palm with your other hand and lock
your fingers together as shown in Fig.

16 | P a g e
5. Keeping your arms straight, press sharply
down on the lower part of the
breastbone; then release the pressure.
6. Repeat step 5, fifteen times at the rate of
at least once per second.
7. Check the cardiac pulse.
8. Move back to the victim's mouth to give
two breaths (mouth-to-mouth
resuscitation).
9. Continue with another 15 compressions
of the heart followed by a further two
breaths of mouth-to-mouth resuscitation,
and so on, check the pulse at frequent
intervals.
10. As soon as the heartbeat returns, stop
the compressions immediately but
continue with mouth-to-mouth
resuscitation until natural breathing is
fully restored
11. Place the victim in the recovery position
as shown in Fig. Keep him warm and get
medical help quickly.

17 | P a g e
OTHER STEPS
1. Send for a doctor immediately.
2. Keep the victim warm with a blanket,
wrapped up with hot water bottles.
Stimulate circulation by stroking the
insides of the arms and legs towards the
heart.

18 | P a g e
2. Use of workshop tools
In addition to the electrical safety discussed earlier, you will also be required to use many
tools properly and safely.
It is necessary that you :
 Select the right type of tools for every operation
 Familiarise yourself with different parts of each tool
 Take care of the tools after use.
 Use the tools properly and safely
HAMMERS AND NAILS
(Different types of nails)
 The hammers are available in different sizes. Select the right size and type of
hammer for the task.
 Ensure that the handle of the hammer is firmly secured and the grip of the handle is
good.
The more you practice these operations, the more skillful and
efficient you will be.

19 | P a g e
 The face of the hammer should be without defects, of correct size and should not
slip.
 The stroke of the hammer should be at the correct angle. Begin with a light stroke
and then strike harder until the job is completed.
CHISELS:
The Chisels will primarily be used for making trenches in the walls for laying of conduits and
in wood work.
 The chisels should be sharp and of correct size
 The hammer should strike the chisel at the correct angle.
 To make a trench in the wall, move from bottom to top. Use goggles to save the eyes
from falling dust or brick and concrete pieces.
 Work slowly and steadily

20 | P a g e
SAWS
You will be required to cut wood, PVC, plastic and metal objects. You will need different
types of saws. Some precautions are necessary to carry out the cutting operations properly
and safely.
 Make a mark at the place where cutting is to be done with a marker or a scriber.
 Use the right size of the blade in the hacksaw. The cutting angle should be borne in
mind while fixing the blade.
 Maintain the balance of your hands during forward and cutting strokes. Apply correct
pressure.
 Carry out the operation slowly and smoothly or else the blade may break.

21 | P a g e
DRILLING
Drilling machines are required to drill holes in the walls, in sheets and at many other
places. Because of the efficiency and ease of operation, hand operated electrical drilling
machines are very popular.
 Ensure that the electrically operated hand drill
machine is safe. It must be earthed and the
connecting wires should be in good condition.
 Use the right size of bit which should be firmly
secured
 Make markings at the place where drilling is to take place.
 The drill should be at angle of 900
 Operate the switch carefully.
SEREW DRIVERS :
Screw driver (insulated) Screw of different types
Use screw driver of correct size to fit the screws. Never use hammer to fix screws.
Drill bits

22 | P a g e
HAND OPERATED WIRE STRIPPING TOOLS
These can be used to remove P.V.C. or rubber
insulation from a single core cable without
damaging the conductor.
There are two types
 manual
 auto-eject.
Manual wire stripper:
The jaws have V shaped notches to cut the
insulation.
The adjuster screw operates as a stop to allow
for a wide range of wire diameters.
Often one cutter becomes sharper than the
other, and cuts more than halfway through the
wires, damaging the conductors. In such an
event, the blunt cutter should be sharpened.
Fig shows another type of wire stripper.
This tool has a series of sharp openings in its

23 | P a g e
scissor blade to allow stripping of wire of
different gauge sizes or diameters. The gauge
size of the wire must be matched with the
opening in the wire stripper to prevent cutting
into the wire and weakening it.
Precautions:
 When using this tool, make sure that it is
correctly adjusted before trying to strip
the insulation from the cable without
damaging the conductor.
 Do not use this tool to cut metallic
conductors.
HAND TOOLS FOR SKINNING -AUTO-EJECT STRIPPER
Auto-eject strippers are used to cut back the
insulation from electrical wire without
damaging the wire strands. To remove the
insulation automatically.
This stripper has two sets of jaws; one set grips
the insulation, the other set has cutting edges.
When the handles are apart, both sets of jaws
are open.
This stripper operates automatically once the
correct position on the blade matching the
diameter of conductor in mm is selected and the
handlers are compressed together.
In an auto-eject stripper, we can select different
blade sizes to match different sizes of
conductors.
Precautions:
While using this stripper the cable insulation
should be put in the proper slot to avoid damage
to the conductor.

24 | P a g e
3. Basics of electrical engineering
CIRCUIT
A circuit contains a source of power, a switch and a load.
Switch
Source
VOLTAGE
Voltage is the electrical pressure which causes the flow of
electric current in a circuit. An anology will help you
understand the concept better. If the level of the water in
the water tank is high, the pressure of water in the pipe
will be more resulting in increase in the amount of water
flowing in the tap. Greater the pressure, more the water.
Similarly, if the voltage in a given circuit is increased more
current will flow in the circuit.
The unit of electrical pressure is VOLTS. In house wiring, you will handle electrical pressures
of 250 V and 400 Volts. The voltage is measured by voltmeter and multimeter.
CURRENT
Current is similar to flow of water in a pipe. The amount
of current in a conductor will depend on the electrical
pressure as well as on the type and dimensions of the
conductor. More current will flow in a copper wire than
in an Aluminium wire for the same electrical pressure.
The unit of current is AMPERES. The current is measured
by Ammeters and multimeters.

25 | P a g e
You will also handle smaller values of current. For example,
POWER
When ever a voltage is applied to an electrical circuit,
some power is consumed in the circuit (load).
The power consumed = Voltage applied x Current flowing
= V x I
The unit of Power is Watt (W)
The higher units of power that you will come across are:
Kilowatt (KW) = 1000 watts
And Megawatts (MW) = 1000000 watts
The electrical devices are rated on the basis of the power consumed by them. The examples
are
Lamps : 15 W, 25 W, 40 W, 60 W, 100 W, 200 W, 500 W and 1000 W
Heaters, irons ovens : 750 W, 1000 W, 1500 W, 2000 W, 3000 W
With this information, you can calculate the current requirements of an electrical device, if
the wattage rating and the voltage are known, using the relationship:
1. A lamp of 100 W will draw a current of = 0.4 A
2. An oven of 3000 W will draw a current of = 12 A
P = V x I
100W
250V
3000W
250V
1 Amp = 1 milliampere = 1 mA
1000

26 | P a g e
ENERGY
You are all familiar with the energy meter that has been installed
near the entrances to your houses. This meter records the energy
consumed in the house over a period of time. For billing purpose
the period considered is 30 days.
Energy = Voltage x current x time
= Power x time
1 kwH = 1 unit
The unit of energy is Kwh
A.C. ALTERNATING CURRENT
In domestic wiring A.C. is used. This A.C. is
supplied to an installation by the electric supply
company.
Its shape is shown in the diagram.
Note that its value is changing with time. It is on the positive side for half of the time and
then it changes its direction. That is the reason why it is called alternating current.
CYCLE
One complete change from (positive to negative) i.e.0 to 0 again is known as a cycle. (see
figure). The symbol of a.c. cycle is
FREQUENCY
The number of cycles completed by the alternating current in one second is called the
frequency of the a.c. supply.
In India and in many other countries, the electric power is supplied at 50 cycles per second.
Number of cycles per second (frequency) is also called Hertz (Hz).

27 | P a g e
In many electrical equipment, you will notice the letters 50 Hz or 50  written on them.
DIRECT CURRENT
The direct current is available from batteries and cells. It is mostly used for devices like
automobiles, mobiles, radios, toys and other electronic gadgets.
current
time
It does not change direction. It’s value remains constant.
THREE PHASE SUPPLY
The electrical supply from the supply company to a domestic installation is available either
as single phase supply or both as single phase and three phase depending upon the needs of
the customers.
Three phase supply : 400 Volts, 50 Hz
Single phase supply : 250 Volts, 50 Hz
The diagram illustrates the concept.
R
B
Y
N
V3
V2
V4
V1


28 | P a g e
In the diagram R, B and Y represent the 3 phases.
N is the neutral wire.
The voltage between any two phase wires is 400 V.
The voltmeter readings of V1, V2 and V3 will be 400, because they are connected between
phases. The 3 phase supply is at 400 V.
The voltage between any phase and neutral will be 230 V.
If voltmeters are connected between R phase and N, or between Y phase and N or between
B phase and N, the readings will be 230 V.
The single phase supply is at 230 V.
The figure above shows a schematic diagram of a 3 phase supply. The phases are called R, B
and Y phases. N is the neutral wire.
The single phase supply is obtained by connecting the domestic installation to any phase
wire and the neutral wire (V4).
MATERIALS & COMPONENTS
You will be required to handle different materials and accessories. You should be able to:
(i) Identify the materials and state their properties.
(ii) Select the materials and use them in wiring properly.
CONDUCTORS:
Conductors are those materials which permit the
flow of current rather easily. Some materials are
better conductors than others.
The most commonly used materials are copper
and aluminium. Copper is a better conductor
than aluminium but it is more expensive.

29 | P a g e
INSULATORS
Insulators are those materials which do not allow the current to flow through them. Hence,
they are used as coverings of the conducting wires, as materials for switches, boards and all
other devices which are used as safety devices.
The most commonly used materials are rubber, plastic, pvc, mica, porcelain and bakelite.
New insulating materials are coming up.
The materials and components used in house wiring has some properties with which you
must be familiar.
RESISTANCES
A resistance opposes the flow of current in an electric circuit.
All materials offer resistance to the flow of current. Materials can be
classified as those which offer high resistance, medium resistance and
low resistance.
The symbol of resistance is  (ohm)
You will come across all the 3 types of materials. The unit of resistance is Ohm (). Higher
values are kilo-ohms (k) and Mega-ohms (M). Lower values are milliohms and micro-
ohms. If you look at an ohmmeter, you will find that the value of resistance varies from zero
ohms (no resistance) to  (very very high resistance).
INDUCTANCE
They are also called chokes. They also oppose the current
flowing through them. They oppose a.c. current only. Not

30 | P a g e
D.C. They are used together with fluorescent lamps and other devices.
The symbol is
And the units are mill-henry and henry.
CAPACITANCE
The capacitance oppose the flow of A.C. They do not
permit d.c. They are also called condensers. The symbol
is (c) and the unit is Farad.
CONNECTIONS OF COMPONENTS
You have noticed that a resistance has two ends. A number of resistances can be connected
in 2 ways.
I I
1.
This connection is called series connection.
 You will also notice that the current in every resistance is same.
 The total resistance between the terminals A and B will be the sum of all the
resistances.
Total = R1 + R2 + R3 = 5  + 10  + 15  = 30 ohms.
2. The resistances can also be connected in a different manner, as
shown.
(L)

31 | P a g e
One end of each resistance is connected at one point and the
other end at another point. This connection is called Parallel
connection.
 Notice that the current in each resistance is different. The value of current in each
branch will depend upon its resistance.
I = I1+I2+I3
 The total resistance will be I = I + I + I
R total R1 R2 R3
 = I + I + I
5 10 15
= 11
30
Therefore R = 30 = 2.72 
The resistances can also be connected as
shown. This is called a mixed connection of
resistances.
The same rules described earlier for series and
parallel connection of resistances apply here.
THE OHM’S LAW
This is a very important and useful law which you will be required to apply in calculations.
Ohm’s law is applicable both in a.c. and d.c. circuits.
It shows the relationship between
Voltage, Current and Resistance

32 | P a g e
In an electric circuit
Ohm’s Law Triangle
You can remember the law easily, if you remember the following training:
E ? E E
I R I R ? R I ?
IR = E E = I E = R
R I
That means, if any two quantities in a circuit are known, the third quantity can be calculated.
Voltage sources
An electrical voltage can be generated in various
ways. A battery uses an electrochemical process. A
car’s alternator and a power plant generator utilize a
magnetic induction process.
Voltage circuit symbol
The terminals of a battery are indicated symbolically
on an electrical drawing by two lines. The longer line
indicates the positive terminal. The shorter line
indicates the negative terminal.

33 | P a g e
UNITS OF MEASUREMENT FOR VOLTAGE
The following chart reflects special prefixes that are used when dealing with very small or large
values of voltage:
Prefix Symbol
1 kilovolt 1 kV 1000 V 103
V
1 millivolt 1 mV 1/1000 V 10-3
V
1 microvolt 1 V 1/1,000,000 V = 10-6
V
Resistance
A third factor that plays a role in an electrical circuit is resistance. All
material impedes the flow of electrical current to some extent. The
amount of resistance depends upon composition, length, cross-section
and temperature of the resistive material.
As a rule of thumb, resistance of a conductor increases with an increase of length or a decrease
of cross-section. Resistance is designated by the symbol “R”
R is proportional to length and inversely proportional to area.
The unit of measurement for resistance is ohms (W).
Resistance can be in the form of various components. A resistor may be placed in the circuit, or
the circuit might contain other devices that have resistance.
Units of measurement for resistance

34 | P a g e
4. Domestic wiring
PLANNING FOR WIRING
The first and foremost activity in planning the wiring of a domestic installation is to calculate
the total connected load as well as the load in different circuits.
As an example, a plan of a house is given in this unit. To workout the load and obtain other
relevant information. It is advisable to have preliminary discussions with the owner of the
house to know his requirements, his budget and his plans for future. Different house owners
will have different requirements depending on their family size, taste, economic conditions.
They will ask you several technical questions and seek your opinions on other matters also.
You must speak to them politely with all the courtesy and give them only correct technical
advice.
LOAD ESTIMATION
The building plan has two bed rooms, a kitchen, bathroom, open space and a corridor. The
example illustrates the procedure. There can be variations.
Bed Room:
(each)
(i) Air conditioner - 2000 W
(ii) 3 light points (CFL,Tube,Lamp) - 150 W
(iii) 1 Ceiling fan - 60 W
(iv) T.V./Computer/Music System - 100 W
TOTAL - 2310 W
Say = 2500 watts
= 2.5 kw
Kitchen : (i) Refrigerator - 100 W
(ii) Oven - 2000 W
(iii) Exhaust fan/electronic chimney - 100 W

35 | P a g e
(iv) Mixie/Grinder Etc. - 500 W
(v) 2 lights (CFL, Lamps, tube) - 100 W
TOTAL - 2800 W
Open Space : (i) Washing Machine - 350 W
(ii) Electric Iron - 750 W
(iii) CFLs (2) - 50W
(iv) Ceiling fan - 60 W
TOTAL - 1210 W
Hall : (i) Air conditioner - 2000 W
(ii) TV/Music System - 200 W
(iii) 2 fans - 120 W
(iv) Decorative lights - 300 W
(v) Others - 100 W
TOTAL - 2720 W
Bath Room : (i) Geyser - 2500 W
(ii) Lights - 100 W
TOTAL - 2600 W
Garage/
Corridors :
(iii) Lights, fan, power point - 750 W
150 W
TOTAL - 900 W

36 | P a g e
WATTAGES OF DOMESTIC APPLIANCES:
Sr. No. Appliances Wattages
1. Fluorescent Tubelight 40 watts
2. Fan 60 watts
3. Mixer/Juicer/Grinder 450 watts
4. Oven 1000 watts
5. Refrigerator (165 ltrs.) 100 watts
6. Air conditioner 2 K watts
7. Night lamp 15 watts
8. Mosquito Repellent 5 watts
9. Air Cooler 170 watts
10. Toaster 800 watts
11. Hot plate 1000 – 1500 watts
12. Washing machine with heater 1500 – 2000 watts
13. Washing machine without heater 200 - 350 watts
14. Water Heater 1500 – 2000 watts
15. Television Set 60 – 90 watts
16. Stereo, Music Player 50 watts
17. Electric Iron 400 – 750 watts
18. Table fan 40 watts
19. Immersion heater 250 – 1000 watts

37 | P a g e
20. Vacuum Cleaner 700 – 750 watts
21. Radio 700 – 750 watts
22. Water pump 750 watts
23. Tape Recorder 20 watts
24. Video Recorders 40 watts
Note : There may be variations due to make, capacity and size of the equipment. Make sure the
rating before you proceed further.
WIRE SELECTION CHART
Flexible Copper wire, size and rating
AREA (Sq.mm) CURRENT (In Amperes)
0.5 4 Amp.
0.75 7 Amp.
1.0 12 Amp.
1.5 15 Amp.
2.5 20 Amp.
4.0 27 Amp.
6.0 35 Amp.
10.0 46 Amp.
16.0 62 Amp.
25.0 80 Amp.
35.0 102 Amp.
50.0 138 Amp.

38 | P a g e
SYMBOLS (IS:732 – 1989)
S.No. Description Symbols used in the
circuit diagram
Symbols

39 | P a g e

40 | P a g e
INDIAN STANDARDS FOR FITTINGS AND ACCESSORIES
Ceiling rose
A ceiling rose will not be used in a circuit whose voltage exceeds 250 V. Only one flexible
cord shall be attached to a ceiling rose.
Socket outlets and plugs
 Each 15 A socket outlet shall be provided with individual fuse.
 Each socket outlet shall be controlled by a switch located immediately adjacent. The
switch controlling the socket outlet shall be on the live side of the line.
 A socket outlet with plug shall be of 3 pin type with the third terminal connected to
earth.
 Sockets may be placed at suitable height from the floor for safety against mechanical
injury and be safe for children.
Lighting Fittings
A switch shall be provided for control of every lighting fitting or a group of lighting fittings.
Where control at more than one point is necessary, as many two way or intermediate
switches may be provided as there are control points.
About switches and Fuses :
1. Switches and Fuse cutouts should always be in phase wire.
2. The neutral wire should be marked N
3. All main switches should be in metal covers or any insulates cover
About accessories :
4. A switch must be provided to a socket. Combination of switch and socket can also be
used.
5. Socket should be safe for children with socket covers.
6. Three pin sockets should be used. The thick pin should be connected to the earth. A 3
core wire should be used in such cases, the green wire connected to the body of
appliance.
Before Wiring :
1. The load in a circuit should not exceed 800 Watts in which maximum numbers of points
are 10.
2. In case of power wiring the phases should be marked with Red, Yellow and Blue colours.
Single phase wires should be identified by letters P and N.

41 | P a g e
3. Main switch board should be 1.5 meters from the ground.
4. Power and heating circuits should be different from light and fan circuits.
About Casing Capping Wiring :
1. The wires in the casing should be straight without twists.
2. The distance between screws in casing should be between 60 to 90 cms.
3. The screws in the capping should not damage the insulation of wires.
4. At the joints of wires, joint cutouts should be used
ELECTRICAL ACCESSORIES
An important component of house wiring is accessories. You should be able to identify
them, select them and connect them properly and safely. The examples of accessories are
switches, holders, fuses, sockets, connectors, distribution boards and Neutral links.
Ratings:
The standard current ratings of the accessories are 5, 15 and 30 amps. The voltage rating is
250 V AC. You should be careful to use the correct ratings. The wrong selection can lead to
accidents and fire.
Mounting:
The accessories are mounted on the surface or can be flush mounted. As you progress, you
will come across different types of accessories.
Switches
Single pole, one-way switch
Used for making or breaking a single circuit.
Single pole, two-way switch
These switches are used in staircase lighting,
where one lamp is controlled from two
places.
Single way switches have two terminal posts
whereas two-way switches have three

42 | P a g e
terminals.
Intermediate switch
This is a four-terminal device capable of
making or breaking two connections from
two positions. This or this switch is used to
control a lamp from three or more positions.
Bell Push or push-button switch
This is a two-terminal device having a spring
loaded button. When pushed it makes the
circuit temporarily and attains ‘break’
position when released.
Double pole switch (D.P. switch)
These switches are used as Main Switches.
This switch has two poles which are coupled
together, operated by a handle. They have a
neutral link and fuses.
It controls phase and neutral simultaneously
and has 2 fuses. Should be properly earthed.
The rating is mentioned on the switch.
Double pole iron-clad main switch
The one in the phase circuit is wired with the
fuse and the other in neutral is linked with a
brass plate or thick copper wire. These
switches should be earthed properly to
safeguard the user. The current rating of the
switch varies from 15 amps to 200 amperes.
Triple (three) pole iron-clad main switch
Used in large domestic installations in 3
phase power circuits. It has 3 fuses and also

43 | P a g e
a neutral link. Should be earthed.
To specify, you should mention the type of
enclosure, the voltage rating and current
rating.
Holders
Lamp-holders
A lamp holder is used to hold lamps or CFLs.
Many types of lamp-holders are available.
 Bayonet cap lamp-holders
 Screw type holders
 Edison screw type lamp-holders
While selecting lamp holders the following
should be mentioned:
(i) Material (brass / bakelite)
(ii) Current rating
(iii) Type of gripping
(iv) Type of mounting
Bayonet cap lamp-holders
In this type, the bulb is fitted into the slot,
and is held in position by means of two pins
in the lamp cap. It has solid or hollow spring
contact terminals, and the supply mains
through the switch are connected to these
contacts.
There are two grooves on the circular
construction of all types of holders. The
groove and the contact terminals are at right
angle to each other. In these type of holders,
the lamp is inserted, forced in, turned slightly
and then left in position. These holders can

44 | P a g e
be classified further as explained below:
Pendent lamp-holders
Are used along with ceiling roses for
suspending the lamps from the ceiling.
Batten lamp-holders
Used on a flat surface such as the round
block, wooden board.
Angle holders
This holder is to hold the lamp at a particular
angle.
Edison screw-type lamp-holders
In this type, the holder is provided with inner
screw threads and the lamp is fitted in it by
screwing. For wattage above 200W Edison
screw-type holders are used.
Edison screw lamp holders have spring-
loaded central contact to ensure good
contact.
Swivel lamp-holders
The swivel lamp-holder is designed for wide
angle directional lighting which is used for the
lighting of shop windows, show cases, etc.
Fuses:
A fuse is a safety device. It is connected in series with the load. When the current in the
circuit exceeds the rated value, the fuse blows off and protects the circuit.

45 | P a g e
There are several types of fuses. But the kit-kat type fuse is commonly used in domestic
installation. While specifying fuses in general, their type, current capacity and working
voltage also should be specified.
Kit-Kat fuses
These are used in domestic installations. This
fuse consists of a porcelain base having two
fixed contacts, for connecting the incoming
and outgoing cables.
The bottom part of the fuse is called the base
and the top is called the fuse-carrier. The
fuse wire is fixed in the fuse carrier at two
ends.
Miniature Circuit Breaker (MCB)
 MCB is used for over load & short circuit
protection of feeders and appliances.
 It is available from 0.5 Amp to 100Amp.
 For single-phase circuit one pole, two
pole or SPN (single pole Neutral) MCBs
are used.
 For three phases Circuit three poles, four
pole or TPN (Triple pole Neutral) MCBs
are used.
Plug Sockets
Used to connect various appliances to the electric supply. To select a socket you should
specify:
 the type of mounting
 2 or 3 pin type
 Voltage and current

46 | P a g e
Two-pin top
It is used for taking the supply from the
socket. It has two pins of the same size which
fit into the socket.
Three-pin socket
This type of socket is suitable for light and
power circuits. These sockets are available as
surface-mounting type and flush type. They
are shown in Fig. There are three terminals.
Terminal on the top is the earth terminal
which is larger in diameter. The earth wire
must be connected to the earth terminal of
the socket. Other two are marked phase and
neutral.
Three-pin plug top
It is used for taking the supply from the 3 pin
socket. It has three pins. Two are similar in
size and the third one is bigger and longer
which is for earth.
A socket which is controlled by a switch, is
also available. Multi-pin sockets are also
available which are suitable for 2 pins and 3
pins having 5 holes in one unit. Multi-pin
sockets for 3 pin of 5 amps and 15 amps are
also available having 6 holes in one unit.
General accessories
Some accessories are used for general and
special purposes such as:
 Adapters
 Ceiling roses
 Distribution boards
 Neutral links

47 | P a g e
Appliance connectors or iron connectors
These are used as female connectors to
supply current to electric kettles, electric
irons, hotplates, heaters etc. It is made of
bakelite or porcelain. The wires are
connected with two brass terminals and the
earth connection is provided with a twin
nickel spring. The cable entry has a rubber
protection type. These are rated as 15A,
250V.
Adaptors
Adaptors with multiple plugs are also
available for taking supply to a number of
appliances from a single point.
Ceiling Rose
Ceiling roses are used to provide tapping
points from the wiring for supplying power to
fans, pendent-holders, tube lights etc.
Normally flexible wires are used for tapping
the ceiling roses.
Ceiling roses have two parts, base and cover,
both made of bakelite.
There are threadings on internal sides so that
the cover may be fixed or tightened with the
base. The base has terminals and holes for
fixing on the block etc. and for wires to
connect the supply.
Two types of ceiling roses are in use.
Two Plate Ceiling Rose
It is made of bakelite and it has two terminals
(phase and neutral) which are separated from
each other. Each of the terminal plates is
provided with a metallic sleeve and a binding
screw on one side through which the circuit

48 | P a g e
wire from the back, enters them. The other
side of the terminal plate is provided with a
washer and screw for tap wire connection.
The two-plate ceiling rose is used for 5A,
250V current capacity.
Three Plate Ceiling Rose
This type of ceiling rose has 3 terminals which
are separated from each other by a bakelite
bridge. It can be used for different purposes.
Connectors
Connectors are used to extend the length of
the wire without joining. They are made of
porcelain, bakelite or PVC based material.
These are available in different types of single
way, two-way, three-way, six-way, 12-way
types. The current and voltage readings,
both, should be specified.
Distribution board
These are used where the total load is high
and is to be divided into a number of circuits.
The number of fuses in the board is according
to the number of circuits, and a neutral link is
also provided so that the neutral wire can be
taken for different circuits. All these branch
fuses are enclosed in a metal box.
Neutral link
In a three phase system of wiring, the phases
are controlled through switches, and the
neutral is tapped through a link called neutral
link. The rating is in Amperes.
The neutral link consists of a terminal for
incoming current and a multi-way outgoing
circuit.

49 | P a g e
MAKING ELECTRICAL JOINTS
Many a times, it becomes necessary to join wires to increase the length. This joint should
be mechanically strong and should conduct electricity properly.
Types of Joints:
1. Pigtail or Rat tail joint
2. Married Joint
3. Scarfed Joint
4. Tape joint
i. Plain tap joint
ii. Knotted tape joint
iii. Duplex cross tape joint
Pig tail Joint
Used in junction boxes or conduct accessory
box.
Married Joint
Used for mechanical strength and good
conductivity.
Scarfed Joint
Used to connect one single wire with
another. Presents good appearance.
Plane tape Joint
Very commonly used. It is a reliable joint

50 | P a g e
Knotted tape joint
A strong joint, can take tension between
wires.
Duplex cross tape Joint
Easier and quicker to make.
SIMPLE TWIST JOINTS
Take two wires (about 50 cms) and straighten
them.
Remove insulation upto about 80 mms.
Clean the ends.
Join as shown in figure.
Give final shape as shown in Fig.A. Solder the
joint and apply insulation tape.

51 | P a g e
SOLDER COPPER CONDUCTOR JOINTS
PROCEDURE
(A finished soldered joint will look as shown in
Fig)
1. Select a 230V AC 50 Hz. soldering iron
(Fig) and ensure that the iron has no
physical damage; the body is well
insulated from the element and is of
the correct voltage and power rating.
A soldering iron should show continuity
between its terminals. Insulation resistance
between the terminal and the body should not
be less than 2 megohms.
2. Check the bit (Fig) to see whether the
surface is smooth and clean.
3. If found corroded, file the tip with a
flat file, so that the surface is smooth
and clean.
4. Connect the soldering iron to the
supply and switch it 'ON'.
5. When the bit becomes sufficiently hot,
apply a small quantity of rosin-cored
solder, and tin the bit.
If the bit is not completely and evenly covered
with solder, clean and tin it again. Never flick
excess solder off the bit. The hot solder may
cause burns to someone or fall into part of the
work, and cause a short circuit.
6. Wipe the bit gently on the cleaning
pad to remove excess solder as shown.

52 | P a g e
7. Clean the joint to be soldered with the
help of sandpaper '00', grade as
shown in Fig and wipe the dust with a
wire brush.
8. Keep the soldering iron bit on the joint
and heat it for soldering.
9. When the joint is heated, keep the
rosin-cored solder on the joint and
allow it to melt.
10. Melt the solder with the heat of the
bit and make sure the solder flows
freely and evenly on the joint.
11. Remove the soldering iron. Use
cotton cloth to wipe off the excess
solder from the surface of the joint
when it is still hot.
12. Allow the joint to cool naturally. Do
not blow air for cooling.
A shining solder surface ensures a good
soldering.
Do not move the joint until the solder
solidifies.

53 | P a g e
SOLDER A FERRULE/SLEEVE TO COPPER CABLE
PROCEDURE
A completed ferrule joint is shown in Fig.
1. Collect two pieces of 7/1.06 or
7/0.914 copper cable 300 mm long,
ferrule, pot, ladle, solder sticks,
matchbox, tripod stand and pressure
stove.
2. Remove the insulation for 75 mm
from one end of both the cables as
shown in Fig and clean the strands.
3. Clean the inner and outer surface of
the ferrule by means of grade' 0 0'
sandpaper.
4. Light the pressure stove, keep the pot
on the stove with the help of the
tripod stand, and melt solder stick in
it.
5. Put some flux in the molten solder
and remove the slag from the top
surface with a ladle.
6. Apply some flux on all sides of the
ferrule and tin the ferrule by dipping
it in the molten solder as shown in
Fig.
7. Wrap a lightly wetted cloth around
the insulation portion of the skinned
cable ends as shown in Fig.
Excess heat applied to the cable end will spoil
the insulation. Wetted cloth will prevent
deterioration of insulation.

54 | P a g e
Excess water in the cloth causes the solder to
splatter when water comes in contact with
the solder. Hence avoid too much water in
the cloth.
8. Apply a small quantity of flux on the
cable ends.
9. Place a prepared cable end over the
pot (as shown in Fig) and tin it by
pouring molten solder on it with the
help of the ladle. Tin both the cable
ends.
10. Insert the tinned cable ends in the
ferrule such that only 6 mm bare
conductor is seen outside as shown in
Fig. and at the same time the cable
ends touch each other inside the
ferrule.
11. Keep the joint over the tray and pour
molten solder over the joint with the
help of the ladle so that the molten
solder gets inside the ferrule through
the gap.
Initial pouring should be quick to enable the
heat transfer to the joint. After a couple of
pourings, the interval between the pourings
should be increased to enable the solder
adhere to the joint.
Avoid splatterring the solder. This may cause
bad burns.

55 | P a g e
12. Hold the jointed cables without
shaking, and allow the soldered joint
to cool.
13. Finally add pure tin to the molten
solder in the pot to compensate the
loss of tin in the solder due to
repeated melting.
SOLDER A SLEEVE TO A COPPER CABLE
JOINT.
As the sleeve does not have any split as in
the ferrule, the molten solder should be
poured on the joint, which is kept
alternatively at a slanted position, a number
of times to make the solder gradually flow
inside the sleeve and the conductors.
SOLDER A LUG TO A COPPER CONDUCTOR
PROCEDURE
(A soldered lug should look as shown in
Fig.)
1. Collect a 30 amps cable lug,
copper cable 711.06 or 71 0.914(6
sq.mm) of 250 mm length,
blowlamp, matchbox, cotton
cloth, solder stick, tray and flux.
2. Clean the inner and outer surface
of the 30 amps cable lug using '00'
grade sandpaper.
3. Put the cable lug to one end of the
cable and mark the cable

56 | P a g e
according to the depth of the
cable lug, as shown in Fig.
4. Add about 2 mm to the marking,
remove the insulation from the
cable and clean the strands.
Avoid damage to the strands of the cable
while skinning. Clean the tray thoroughly.
The tray should be free from dirt and
water.
5. Wrap a cloth/cotton tape on the
insulation of the cable to a length
of 30 mm as shown in Fig. and wet
it with water.
Use minimum water to wet the cloth/tape.
Do not allow water to drip.
6. Light the blowlamp and let it emit
a blue flame.
7. Apply a thin coat of flux to the
cable end.
8. Tin the cable end by monitoring
the blowlamp on the solder stick
and allowing the molten solder to
fall on the bare stranded cable end
as shown in Fig.
A thin coating of tin should be on the
stranded cable end.
9. Apply a small quantity of flux
inside the lug socket. Tin the lug by
melting the solder stick to fill the
socket and pour the molten solder
in the tray.
Pouring out the molten solder from the lug
socket a couple of times will make the
tinning perfect.

57 | P a g e
10. Apply some flux to the cable end
and the socket interior .
11. Fill up the socket of the lug with
molten solder.
12. Monitor the blowlamp flame on
the socket, insert the cable in the
socket and hold the cable
vertically as shown in Fig.
13. Remove the blowlamp and hold
the cable and socket without
shaking.
14. Remove the extra solder from the
lug and cable by wiping with a
piece of cotton cloth while the
solder is still hot.
15. Keep on holding the cable and lug
and allow the solder to solidify.
Do not use water to cool the lug. This will
make the solder to crystallize and become
weak.
SELECTION OF WIRING
There are some considerations which influence the selection of the type of wiring in a
house.
1. Safety
Safety is the most important criteria. In situations where there is risk of fire and
leakage of electricity due to moisture, conduit wiring is desirable.
2. Appearance
The wiring must have proper look. It should not spoil the beauty of a house.

58 | P a g e
3. Initial cost
The cost of the wiring must suit the pockets of the owner.
4. Maintenance
The wiring should be such that it requires minimum maintenance. The maintenance
cost is also a consideration while choosing the wiring type.
5. Durability
The life of the wiring should be long enough. Wiring for permanent building and
temporary structures will be different.
Out of the many systems of wiring, a comparison is made between the 3 main types of
systems. The PVC materials are now replacing traditionally used materials like wood,
porcelain etc.
1. Cleat wiring
 Low cost
 Appearance not very pleasing
 Additions / alternations very easily done
 Used for temporary work
2. Casing Capping (PVC)
 Medium cost
 Good appearance, quite popular in average houses, Addition – alterations easy.
 Used for residential, offices, commercial buildings
 Parts can be easily fixed, extension easy.
3. Conduit wiring
 Concealed conduit expensive
 Good appearance
 Alterations difficult
 Used in big buildings, workshops, godowns and posh houses.

59 | P a g e
METHOD OF MARKING THE LAYOUT FOR WIRING
When installing electrical wiring in a building, it is necessary to mark the layout on the
ceiling and walls to indicate the position of the various fittings and appliances to be installed
and the routing of the cable runs.
To assist in the marking of the layout on the walls and ceilings, the following tools are used.
 Plumb bob or plummet
 Spirit-level
 Water-Ievel
Plumb bob
A plumb bob consists of a block and a weight attached to
each other by a string through their centers. When the
plumb bob is placed on the wall, the weight is made to
hang vertically through the string and the plumb line
(string) indicates the true vertical as shown in Fig.
Spirit-Level
This consists of a level tube set in a straight edge. When
the air bubble in the level tube locates centrally between
the markings on the tube, the surface on which the
straight edge is kept, it is deemed to be in a horizontal
position, Spirit-Ievels are usually available in sizes from
150 mm to 1 m long. A spirit-Level is shown in Fig.
Water level
A water-Level consists of two calibrated glass tubes
which are connected together by a flexible rubber tube.
The tube is filled with water until the level is halfway up
in both the glass tubes. The glass tubes shall be sealed
when not in use. Instead of glass tubes on either side of a
non-transparent tube, we can use an ordinary
transparent PVC tube as water level. Fig. shows a water-
Level with glass tubes.

60 | P a g e
Marking of layout
For marking of layout on walls and ceilings of an
installation, chalking lines are used. Fine chalk powder is
dusted on to a twine thread. When the twine thread
dusted with chalk powder is held taut against a wall and
'plucked', it marks the wall with a fine line of chalk dust.
Marking of true vertical runs
For marking the vertical lines, a 'plumb bob' also known
as plumb line, is generally used. A 'plumb line' is used in
the following manner.
 Determine the position of the vertical line to be
marked
 Hold the string (line) between the finger and the
thumb at an appropriate distance from the
weight to correspond with the height of the
vertical line position marked.
 Suspend the weight just clear of the floor or other
obstructions, such as skirting boards, and rest the
thumb against the wall and hold it steady until
the string and the plumb bob are at rest, just clear
of the wall's surface, at the location required as in
Fig.
 Make two pencil or chalk marks on the wall at
least 1 meter apart to correspond with the line of
the string.
 Draw a line joining the two marks using a straight
edge and extend the lines as necessary.
 For marking chalking twine (string) lines, stretch
out the chalking twine, pullout a sufficient length
for the height of the line required.
 Hold the lower end with one foot and pull the
string taut, adjusting the foot and hand as
necessary until the line is directly over the two
pencil marks on the wall. (Instead of holding the
string with your foot, another person may be
asked to assist.)
 Use the free hand to lift the tautly held string
about 20-30 mm away from the wall and release
it. The string springs back to deposit a line of
chalk dust on the surface of the wall as shown in
Fig.
 A chalking line is usually used to mark long lines

61 | P a g e
Marking 'true' horizontal runs
The horizontal run is marked either by using a spirit-Level
or a water-Level. Generally for electrical works, a spirit
level is used.
Mark the horizontal lines as outlined below,
Determine where you want the horizontal line to be
drawn, using dimensions from the drawings and
measuring off the fixed features such as the floor or
ceiling.
Make a single mark on the wall at the required height.
Hold the spirit-Level with both hands and line it up with
the mark on the wall.
Check the position of the air bubble in relation to the
markings on the tube.
Adjust the spirit-Level until the bubble comes to rest exactly in the center of the two
markings. Finally hold the level in position with one hand, and with the free hand draw a
pencil line along the straight end of the level as in Fig.
Use the straight edge of the level and line it up with the line already made and extend the
pencil mark to the left and right of the original line.
Where long lines are required, repeat the above steps in the desired direction of the wall.
Measuring off horizontal and vertical runs
Horizontal lines can also be drawn by measuring off from a common base. For drawing
horizontal lines on the walls, the common base could either be the floor, top of the skirting
board or ceiling surface, provided the floor or the ceiling is reasonably level and even.
This method of measuring is used in many situations where installations are made parallel
to existing features such as door frames, and skirting boards.
Marking cable runs on the ceiling
For marking on the ceiling, choose two adjoining walls which are at right angles to each
other. Taking these walls as the base, take the measurement of the cable run route centers.
Keep the chalk-powdered string on the marking jointly by holding the edges of the string
with the help of assistants and pull the strings hard to make the chalk marking on the
ceiling.

62 | P a g e
METHODS OF CONNECTIONS IN DOMESTIC INSTALLATIONS
Introduction
As shown in the circuit diagram of a sub-
circuit of six lamps, three controlled
separately by one-way switches, and three
controlled as a group by a one-way switch.
If the circuit were wired exactly as in the
circuit diagram, a large number of joints
would be necessary which are to be done in
joint boxes only, resulting in an increase in
cost and labour.
Two methods are adopted to execute the
wiring economically. They are
1) The looping-back method
2) The joint-box method.
Looping Back (Loop-In) Method
In this method, no separate joints are used. Instead twisted joints are used at the terminals
of the accessories themselves.
Where the looping-back system of wiring is specified, the wiring shall be done without any
junction or connector boxes on their line.
In domestic wiring installation, the looping-back system should be preferred.
The loop-back system can be adopted with two variations.
Loop in method using 2-plate ceiling roses
and switches
Fig. shows the schematic diagram of the
circuit shown in Fig as wired by the looping-
in system.
No separate joints are required in joint
boxes. Twisted joints in the terminals of the
two-plate ceiling roses and of the switches
are, however, required.
The schematic diagram shown in Fig is not

63 | P a g e
practicable and cannot be acceptable in any
of the wiring systems like conduit, wooden
batten or casing and capping system as it is
generally necessary to run the cables close
together in the same conduit, batten or
casing.
Fig. shows the same circuit suitable for
practical work.
Loop-in method by 3-plate ceiling rose
We can also use 3-plate ceiling roses as
shown in Fig. Considerable cable length
could be saved by using the third terminal of
the ceiling rose as a looping-in terminal for
the switch drop, so that two cables only are
required from the ceiling rose to the switch.
Joint -box method
In the joint-box method, wherever tapping
has to be taken from the cable, joints are
made. All joints in cable conductors shall be
made by means of porcelain connectors or
connector-boxes, and housed in suitable
joint boxes.
In any wiring system no bare or twist joints
shall be made at intermittent points in the
cable run of the main circuit or sub-circuit.
If joining is unavoidable, such joints shall be
made through proper cut outs or drawn
through proper junction-boxes open for easy
inspection.
Fig. shows the joint-box method of wiring
system.
In this system a pair of cables from the
switches and ceiling roses will terminate in
the junction box. The junction-box is kept in
between the light points and switches for
economy in the cable length.

64 | P a g e
MEASURE WIRE SIZES
Procedure
TASK 1: Measuring the wire sizes by SWG.
1. Skin the insulation of the cable.
Exercise care to prevent nicking.
2. Clean the surface of the wire with a
cotton cloth. Remove insulation
particles and any adhesive coating over
the conductor surface.
Do not use abrasives to clean the conductor.
Use of abrasive material reduces the
conductor size.
3. Straighten the end of the conductor to
be measured. Do not use any hand tool
directly on the conductor for
straightening.
4. Insert the conductor in the slot of the
wire gauge and determine the close fit
slot.
5. Read the marking at the slot. It gives
the wire size in SWG. The other side
will give you the dia. of the wire in mm.

65 | P a g e
CLEAT WIRING
Introduction
The type of wiring to be adopted is dependent on
various factors, viz. durability, safety, appearance, cost,
consumer's budget etc.
Types of internal wiring
The following are the types of internal wiring used in
domestic installations.
 Cleat wiring (for temporary wiring only)
 Wood casing & capping wiring
 CTS/TRS (batten) wiring
 Metal/PVC conduit wiring, either on the surface or concealed in the wall.
Cleat wiring
This system shown in Fig. uses insulated cables supported in porcelain cleats.
B.I.S. recommendations for cleat wiring
General
This system shall not be employed for wiring on damp walls or ceilings unless precautions
are adopted for effectively preventing dampness and thus the deterioration of the
insulation of the conductors.
Accessibility
Cleat wiring shall be run, as far as practicable, so as to be visible. In positions where they
would be liable to mechanical injury and where they are less than 1.5 m above the floor,
they shall be adequately protected.
Class of cables
Vulcanized rubber insulated cables, PVC and polythene insulated cables, braided or
unbraided insulated cables could be used without any further protection.
Cleats
All cleats shall consist of two parts, a base piece and a cap. Cleats shall be fixed at distances
not more than 60 cm apart and at regular intervals. Where cleat wiring is laid along an iron
joint, porcelain cleats shall be inserted either with varnished wood fillets or varnished wood
clamps securely fixed so as to prevent the conductors from coming in contact with the metal
along which they are passing.

66 | P a g e
Fixing of cleats
In ordinary cases, cleats shall be attached to wooden plugs fixed to the walls.
Distance apart of wires
For pressure up to 250 volts, cleats shall be of such dimensions that in the case of branch
loads, the conductors shall not be less than 2.5 cm apart, center to center, and in the case of
sub-mains not less than 4 cm apart, center to center.
Care shall be taken in selecting the size of cleats particularly for branch distribution wiring
where two-way and three-way porcelain cleats are essential and the difference in size shall
be reasonable.
Care should also be taken to ensure that grooves of porcelain cleats do not compress the
insulation not be too wide for a loose fit.
Under no circumstances two wires shall be placed in one groove of the porcelain cleats.
Crossing of conductors
Where cleated conductors cross each other they shall be separated by an insulating bridging
piece, which will rigidly maintain a distance of at least 1 .3 cm between the conductors.
Where joints are required for connecting bifurcating wires, junction boxes with porcelain
connectors inside shall be used.
Protection near the floor
No cleat wiring shall be left unprotected up to 1.5m above the floor level. When brought
through the floor it shall be enclosed in a conduit. (IS 732.:1963}
EXECUTING PVC CASING-CAPPING WIRING
1. Mark the position of casing capping on the walls with a thread coated with coloured
chalk. Make sure that the marking is parallel to the floor.
2. Make holes on the walls with electrical drill machines at regular intervals. Affix rawl
plugs (PVC) in the holes.
3. Drill holes in the casing to match the holes and fix screws. Run the casing capping
throughout.
4. Select the wires depending on the load. Insert the wires and put cover.
5. Install all electrical accessories and connect them.
6. Conduct all tests as per Indian Standards regulations.
7. Take corrective actions, based on test results.

67 | P a g e
This unit contains a plan of a building.

68 | P a g e
‘A’
‘B’
Wiring plan for the building shown (Area A) in the plan. Details of wiring for only one Bed
room are shown (Area B).

69 | P a g e
3.0 Estimating the cost of house wiring
Every customer will like to know the total expenditure to be incurred on House wiring and
ask you several questions. Your must be able to give him advice which is technically correct
and suits his budget.
The cost will depend on
(i) The type of wiring – conduit (surface / concealed)
– casing – capping etc.
(ii) Quality of fittings
Only those fittings should be recommended which satisfy ISI requirements. There
should be no compromise on safety.
From the building plan
(i) Count the number of fittings and accessories required.
(ii) Estimate the amount of wire required from the dimensions of the rooms.
(iii) Estimate hardware requirements (nails, screws,t ape, roll plugs etc.)
(Prepare a complete list with specifications)
Obtain the rates from local market.
Calculate the costs of (i), (ii) and (iii)
Labour Cost
This will be worked out on the basis of mandays for:
(i) unskilled persons required.
(ii) Semiskilled persons required.
(iii) Skilled persons
This cost varies from place to place.
Miscellaneous
To account for unexpected contingencies, profit margins and things not included in the
estimate prepared miscellaneous changres are added.

70 | P a g e
An example of estimate for a bed room in the building plan is as below:
Item Quantity Rate
Bedroom 1
1. Switch 5 A 08
2. Switch 15 A 01
Socket 5 A 04
3. Socket 15 A 01
4. Ceiling rose 01
5. Ceiling rose box 01
6. Casing capping (depends on room size and
routing) 10 feet each
07 approx.
7. Bends 15 approx.
8. Wire (including earth wire)
Black 01 roll approx.
Red 01 roll approx.
Green 01 roll approx.
9. Hardware (Rawal plug + screw…….. + Tape
roll)
Assorted
10. Surface modular box 01
4 way 03
8 way 01
11. Modular plate
4 way 03
8 way 01
12. Fan Regulator 01
Labour Charges
The rates are not mentioned due to frequent variations.

71 | P a g e
4.0 Testing of domestic installation
Introduction
The Bureau of India Standards has laid down some regulations (IS: 732-1989) which must be
understood and followed.
 The regulations states that “Every installation shall on completion and before being
energized, be inspected and tested”.
 The methods of test shall be such that no danger to persons or property or damage
to equipment can occur even if the circuit tested is defective.
Visual Inspection:
A Visual inspection shall be made to verify that the installed electrical equipment is
 In compliance with the applicable Indian Standard
 Correctly selected and erected
 Not visibly damaged so as to impair Safety
POLARITY TEST
This test is conducted to test whether the switches are connected in phase or not.
 Open main switch, take out fuse carriers and keep them safe
 Remove all lamps from lamp holders
1. Remove covers of all switches
2. Put fuses of correct ratings in distribution box and in main fuse carrier.
3. Switch on the supply
4. Connect one end of the test lamp to earth point.
5. One by one touch the other end of the test lamp to terminal points of switches
6. In case of 2 way switches, change knob position.
7. If the test lamp glows, the switches are correctly connected

72 | P a g e
TESTING POLARITY OF SOCKETS
This test is conducted to ensure that the
phase in the socket is controlled by the
correct switch.
Method
 Keep the switch in off position.
 Test the neon tester and ensure it is
safe to work with.
 Insert the tester in the right hole of the socket (as shown).
 If the switch is off, tester should not glow.
 Put the switch in ON position. Tester should glow.
CONTINUITY TEST
1. Switch off the Mains. Take
out the fuses and neutral link.
2. Remove fuse links of
distribution box.
3. All lamps and fans should be
connected.
4. Short the socket outlets.
5. Keep the fan regulator knob
in the Centre.
6. Keep all switches in off
position. This test is to be
conducted in different circuits
separately.
7. Disconnect the neutral of each circuit with the common neutral link.
8. Connect one end of a 500 V meggar to an external terminal.
9. Connect the other terminal to the neutral
10. Rotate the meggar at rated speed.
11. One by one, switch ON and OFF the switches of the circuits under test.
12. When the switch is off, the meggar reading should be infinity. The reading should be
zero under switch ON condition
13. Identify the defective area and take corrective action.

73 | P a g e
EARTH LEAKAGE CURRENT TEST
This test is conducted to measure the resistance between wiring of the installation and the
earth.
1. Switch off mains and remove fuse from main
2. All fuses in distribution box should be in place.
3. All lamps are to be in place.
4. Switch on all single pole switches
5. Take a megger of 500 V. connect L and N terminals of the megger. Connect the shorted
link to the wiring side, never on the side of the service line.
6. Connect the earth terminal (E) of the megger to earth terminal.
7. Operate the megger property. The value of resistance measured should be according to
regulations.
INSULATION RESISTANCE TEST
1. Open the main switch
2. Remove all lamps and disconnect all appliances.
3. Put in all fuses in the distribution box. Fuses should be of proper ratings.
4. connect L terminal of the megger to f
5. Operate the megger at rated speed and note the readings. The resistance value should
be more than 1 mega ohm.

74 | P a g e
CHECKING FUSES
For safety reasons, it is necessary that all electrical
circuits are protected by use of properly rated fuses.
1. Switch off the main switch.
2. Ensure that the fuse wires in fuse grips are
properly fixed and are of correct ratings.
3. Check that the rating of the neutral link is OK.
4. Check all circuit fuses in the distribution box.
5. Check branch fuses.
It is advisable to label fuse ratings to avoid problems
in future.
To select the fuse rating, the minimum of the rating of any one is made the base
 Pole to meter
 Meter to main switch
 Meter to DB
 Amperage of main switch
 Tight terminal
 Check rating of ok / not
 Rating of the energy meter

75 | P a g e
TYPICAL LIGHTING CIRCUITS
Introduction
House wiring requirements may be as
simple as one lamp controlled by one
switch or may be a special requirement of
controlling one lamp from two or more
number of places.
For example, such circuits are used for
staircases, bedrooms and the corridor
lighting system.
The basic principle involved in such circuits,
and the requirement of additional special
accessories are discussed below.
Circuit No.1: Bedroom lighting
A bedroom may require one 1.amp at the
dressing table controlled by a switch, and
one lamp just above the bed which may
require dual control by two 2-way
switches, one provided near the entrance
(door) and the other provided above the
bed in the form of a pendant switch
hanging from a 3-plate ceiling rose. Fig
shows such an arrangement.
Circuit No 2: Corridor Lighting Circuit
Let us consider a long corridor having 4
lamps, L 1, L2, L3 and L4 which are to be
controlled such that as a person moves in
the corridor, in either direction, he
switches ON one light after the other while
the lamp lighted earlier is switched off:
Such an arrangement is shown in Fig .
Switches S2, S3 and S4 are ganged two-way
switches operated by cross-bars.

76 | P a g e
According to another requirement for
corridor lighting circuits, the entire set of
lamps in the corridor is controlled from 4
different places in such a way that all lamps
together can be switched 'ON' or switched
'OFF' by any one of the control switches
from four different places as shown in Fig.
Circuit No 3: Series/Parallel Circuits
Connection of single and two way switches
or special switches called two-way center
OFF switches may be used to provide
bright or dim lights in the same circuit
through a series or parallel connections.
Such lamps are commonly found in
corridors and bedrooms of hostels,
hospitals, railway compartments etc.
With two-way centre off switch to control
one lamp bright and two lamps dim
Fig shows two lamps controlled by a two-
way center off (ON/OFF and ON) switch.
When the switch position is on the
terminal No.3, the lamp L 1 burns bright
and when the switch is in position No.1,
the lamps L 1 and L2 are connected in
series so as to give dim light. Switch
position 2 indicates 'OFF' position.
With one 2-way center off switch and one
1-way switch to control two lamps
independently bright or dim
According to the circuit shown in Fig. when
the two-way switch is on, terminal 3, L2 is
short circuited and the lamp L 1 burns
bright. Alternatively when the two-way
switch is on terminal 1 the lamp L 1 is
short-circuited while the lamp L2 burns
bright and when the two-way switch is on
terminal 2, both the lamps give dim light
because they are in series.

77 | P a g e
With one 2-way switch and one 1-way
switch to control two lamps in such a way
that one lamp is bright or two lamps are
dim.
Fig shows such a circuit. When the single
way switch is in 'ON' position and the two-
way switch is in position 1, then the lamp
L2 burns bright and lamp L 1 is off.
When the two-way switch is in position 2
both the lamps are in series and burn dim.
Circuit No.4: Master switch controls
A master switch derives its name from its
function and any switch, such as a one-way
or two-way switch, depending on the
circuit requirement, can be used for this
function.
A master switch can be used as 'master
off', 'master on' or a 'variable master'
control.
A master 'OFF' switch is incorporated in a
circuit to keep the lamps in the 'OFF'
position irrespective of the position of the
individual switches.
Further this switch prevents one from switching 'ON' the lamps. Single way switches
incorporated as shown in Fig is examples of such controls.
A master 'ON' switch is incorporated in a circuit to keep the lamps in an 'ON' position
irrespective of the position of the individual switches.
Further this switch prevents one from switching 'OFF' the lamps. Fig. shows the application
of a master 'ON' switch, with variations in connection.
VARIABLE MASTER CONTROL
When master 'ON' and 'OFF' controls are
incorporated together, the control is called
variable master control. As shown in Fig 8,
the lamps L 1 to LS are controlled

78 | P a g e
independently by switches S 1 to SS
respectively whereas two single-ways
switches M1 and M2 act as variable master
controls.
A careful study of the circuit will reveal the
following conditions.
M1OFF & M2 OFF All lamps off irrespective of their position.
M1 or M2 ON All lamps can be individually controlled for 'ON' or 'OFF'.
M1 and M2 ON All lamps will be ON irrespective of their position.
Apart from the above there are a number of special switches available in the market to have
various combinations of connections. One such switch is the manual switch. You are advised
to investigate the number of terminals in such switches and the mode of connection in those
switches with the help of a multimeter or Megger.
ASSEMBLE AND INSTALL A FLUORESCENT LAMP
PROCEDURE
Assembling of a fluorescent lamp with its
accessories
1. Check the chock for its short and
open with a test lamp as shown in
fig. and record the results.
2. Check the starter with a series test
lamp as shown in fig. Observe the
flickering of the lamp which
indicates good condition of the
starter.
3. Assemble the following fluorescent
tube accessories in the fitting base.
Refer to the sketch
 Holders for tube
 Starter-Holder
 Choke

79 | P a g e
4. Connect the accessories as shown
in Fig (for a single tube light). Also
install the tested starter.
5. Test the filament on both sides of
fluorescent tube for its continuity
as shown in fig. Discard the
fluorescent tube with open or
fused filament in either side.
6. Fix the bulb in the holder.
 Firstly, you have to make sure that
the slot in the inner parts of the
holder is turned to the proper
position.
 Then insert both the ends (pins)
into the holder of the fittings on
either side of the tube. One end is
shown in Fig. Push the socket pins
all the way into the fittings until
you feel that you can turn the tube
in the sockets.
 Turn the tube at both ends in any
one direction by a quarter turn.
Stop when you feel that the pins
have snapped into position.
 Be careful not to bend the pins at
either end of the tube.
7. Test the tube light assembly for its
working

81 | P a g e
Assemble, connect and install a twin fluorescent Lamp
Procedure
Twin-tube light - series connection
(600mm/20W)
1. Test the choke starter, fluorescent
lamps and capacitor for their
working.
2. Assemble the choke, capacitor,
lamp-holders, starter-holders in
position in the lamp fitting for twin
the feet.
3. Connect the accessories as per the
circuit diagram. (Fig)
Terminate the leads to 3 connector for
connecting to the supply.
4. Fix the starters and the fluorescent
tubes.
5. Connect the fitting to the supply
and test for its functioning.
6. If it is not glowing adjust the
starter and the tube.
Twin-tube light -parallel connection
(1200mm)
1. Repeat the steps 1 to 2 of Task 1
circuit diagram for the two
1200mm tube lights.
3. Fix the starters and fluorescent
lamps, connect the fitting to the
supply and test.
Industrial fitting assembly and
installation
1. Repeat the steps of Task 2 for
assembling the industrial fitting by
connecting 3.8 MFD in series with
anyone of the tube circuits as
shown in Fig.
2. Remove the tubes from the fitting
before installing.
3. Mount the fitting, suspending from

82 | P a g e
the desired location and providing
the required length of wires to
connect to the supply in the wiring
system.
Ensure the mounting is firm and does not
give way because of the weight of the
fitting itself.
4. Connect the supply leads to the
fitting from the ceiling rose or
junction box.
5. Switch on the supply and test for
its working.
ASSEMBLY AND INSTALLATION OF SODIUM VAPOR LAMP WITH ACCESSORIES
Procedure
1. Read the specification from the
markings on the leak transformer,
choke and bulb.
2. Check the transformer and choke
with a test lamp for shorts and
open.
3. Assemble the accessories (choke,
leak transformer and lamp-holder)
in the fitting.
Follow strictly the manufacturer's
instructions.
4. Give connections as per diagram
shown in Fig .
Use the recommended type of termination
only.
5. Choose the appropriate voltage
tapping suitable to the supply
voltage.
6. Fix the bulb in the holder .
Ensure the fitting is properly earthed.
7. Test the working of the assembled
fitting by connecting it to the mains.

83 | P a g e
8. Note the time taken for the bulb to
give full illumination.
9. Repeat the above steps for a high
pressure sodium vapour lamp.
Connect as per the diagram shown
in Fig .
CONNECTION AND INSTALLATION OF MERCURY VAPOUR LAMP WITH ACCESSORIES
Procedure
1. Read the specification of the mercury
vapour lamp and the choke from the
markings.
2. Connect the H.P.M.V. lamp in series
with the 60W, 230V bulb and test in
230V AC supply. Check whether the
series lamp glow.
3. Test the choke for its working
condition.
4. Assemble the accessories (choke,
holder and capacitor) in the fitting,
following manufacturers instructions.
circuit diagram, Fig. using the
recommended type of terminations.
Choose the tapping of the choke suitable to
the rated supply system voltage.
6. Fix the bulb in the holder and test
the working of the lamp with the
supply voltage.
Ensure the fitting is properly earthed at the
earthing terminal provided, before testing.
7. A modem M.V.lamp with a built-in
resistor needs no external accessories
to be connected as discussed above.
It can be connected as we do an
incandescent lamp.

84 | P a g e
Installation of the M V lamp fitting
8. Assemble, connect and test the M. V.
Iamp fitting on a table for its working.
Then remove the cover and bulb.
Mount at the location
9. Observe the recommended method
and procedure specified by the
manufacturer in the installation
leaflet.
Do not alter the specifications recommended
by the manufacturer because it should be
strong enough to support the weight of the
fitting
10. Connect the M. V. lamp fitting to the
supply. The method depends on the
system of wiring, location of fitting
etc.
Ensure that the supply line is dead (not live),
before making the connections.
11. Fix the bulb in the holder securely
and refit the cover.
12. Switch on the supply and wait until
the high pressure mercury vapour
lamp glows with its full brightness.
Then switch off the supply.
CONNECT THE GIVEN NEON SIGN WITH THE ACCESSORIES AND TEST
Procedure
1. Check the neon lamp mounting in the tracks and its proper supporting clips, as
shown in figs

85 | P a g e
2. Make electrode connections between the tubes using nickel leads.
3. Test the transformer for continuity and insulation.
Short the H. T. leads before conducting the test on L. T side. This avoids shock due to
accidental contact.
4. Make the necessary connections as per the circuit diagram shown in Fig
Use cables having an insulation rating at least 4 times of the operating voltage of the neon
sign.
5. Earth the H.T. side of transformer, the body of transformer and metal frame of the
neon sign.
6. Switch ON S1 and S2 respectively and check for neon light glowing. Observe for no
sparking due to loose connection at the neon tube
7. Switch Off S2 and S1 respectively to turn the set off.
Item / Part
No.
Name of Part / Description Specification No.
T
Step up transformer
230/2000V 100VA 1
L1
R. F. Choke
20 mH 1
C
Capacitor
5 F 1
F
Fuse
15A 4
S2
Fireman’s switch D. P.
16A, 250V 1
S1
Main switch D. P.
16A, 250V 1

86 | P a g e
5. Transmission and distribution
POWER SYSTEM
Electric power is generated at the generating stations of different types (Eg. Thermal, Hydro,
Nuclear etc.) These generating stations are interconnected with a common electrical
network. This interconnection of generating station forms a power System. The various
elements of the system are Generating stations, Transmission lines, Substations, Feeders,
Distribution system etc.
A typical layout is given in Figure.

87 | P a g e
Generation and Transmission is 3 phase. The distribution is 3 phase and single phase A.C. 50
cycles. The Generators generate voltages usually 6.6 KV, 11 KV or even 32 KV. This voltage is
stepped up by 3 phase transferred for transmission purpose. (132 KV).
This voltage is stepped down by receiving stations (RS) to lower voltages (33 KV). The power
is then Trans feared to substations through overhead lines/underground cables.
At the substation, the voltage is reduced from 33 KV to 3.3 KV, 3 wire distribution system.
This is called primary distribution.
The secondary distribution is at 400/230 V. The voltage is reduced from 3.3 KV to 400 V in
distribution substations.
The most common system of distribution is 400/230 V 3 phase, 4 wire system, the low
voltage distribution system is devided into
(1) Feeders
(2) Distributors
(3) Service Mains
Generating voltages
High voltage transmission
Primary distribution
Low voltage distribution
6.6,11,13.2 or 33 KV
220,132,66 KV
3.3, 6.6 KV
400/230 V
DISTRIBUTION
The distribution system may be divided into feeders,
distributors, sub-distributors and service mains. Feeders are the
conductors which connect the sub-station to distributors
serving a certain area. From distributors various tapping are
taken. The connecting link between the distributors and the
consumers’ terminals are the service mains. The essential
difference between a feeder and a distributor is that whereas
the current loading of a feeder is the same throughout its
length, the distributor has a distributed loading which results in
variations of current along its entire length. In other words, no
direct tappings are taken from a feeder to a consumer’s premises.
In early days, radial distribution of tree- system type, as shown in fig. was used. In this
system, a number of independent feeders branch out radially from a common source of

88 | P a g e
supply i.e. a sub-station or generating station. The distribution transformers were connected
to the taps along the length of the feeders. One of the main disadvantages of this system
was that the consumer had to depend on one feeder only so that if a fault or breakdown
occurred in his feeder, his supply of power was completely cut off till the fault was repaired.
Hence, there was no absolute guarantee of continuous power supply.
For maintaining continuity of service, ring-main
distributor (R.M.D.) system as shown in Fig. is
employed almost universally. SS represents the
sub-station from which two feeders supply power
to the ring-main distributor at feeding points F1
and F2. The ring-main forms a complete loop and
has isolating switches provided at the people at
strategic points for isolating a particular section
in case of fault. In this way, continuity of service
can be maintained to other consumers on
healthy sections of the ring-main. The number of
feeders of the ring-main depends on (i) the
nature of loading-heavy or light (ii) the total length of the R.M.D. and (iii) on the
permissible/allowable drop of voltage. Service mains (S) are taken off at various points of
the R.M.D Sometimes sub-distributors are also used. Since a loop or. Closed ring-main can
be assumed to be equivalent to a number of str4aighth distributors fed at both ends, the
voltage drop is small which results in economy of conductor material. The service mains are
the connecting link between the consumer’s terminals and the R.M.D. or sub-distributor.
SYSTEMS OF A.C. DISTRIBUTION
1. Single phase, 2 wire system
2. Single phase, 3 wire system
3. Two phase, 3 wire system
4. Three phase, 3 wire system
5. Three phase, 4 wire system
Two phase 3 wire system Two phase 4 wire system

89 | P a g e
Three-phase, 3-Wire System
Three-phase systems are used extensively. The 3-wire system may be delta-connected of
star-connected whose star point is usually earthed. The voltage between lines is V in delta-
connection and √3 V in case of star connection where V is the voltage of each phase as
shown in (a) and (b) respectively.
Three phase 4 wire systems
The 4th
wire the neutral wire; examine the relationship between line voltage and phase
voltage as well as the line current and phase current.
CORONA
This phenomenon occults in high Tension transmission lines. When a high voltage is applied
across two conductors which are spaced at a larger distance compared to their diameter a
bluish glow occurs along the length of the conductors” A hissing sound is also heard. This is
known as corona of the voltage is further increased, the intensity of glow and sound is also
increased. This happens both in case of D.C. and AC transmission lines but the glow is
different.

Electrical & house wiring technician book soft copy

Electrical & house wiring technician book soft copy

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Electrical & house wiring technician book soft copy

Similar to Electrical & house wiring technician book soft copy (20)

More from Ramesh Meti

More from Ramesh Meti (20)

Recently uploaded

Recently uploaded (20)