Domestic wiring

UNIT IV
A. ELECTRICAL WIRING
B. ILLUMINATION
C. SAFETY AND PROTECTION
Prepared by
Vima Mali

With the water can we generate electricity?.

INTRODUCTION
• A Building, whether used as a home, as a
godown, as a factory, as a cafeteria, as a hotel,
as a research laboratory, or as an educational
institute, needs electrical installation.
• To run various appliances, equipments and
machinery also we need electrical power.

WHAT IS AN ELECTRICAL WIRING?.
Electrical wiring is generally refers to insulated
conductor used to carry current and associated device.
(or)
Wiring is systematic laying of wires for the smooth
flowing of electricity current at different utility places
with utmost safety and precautions.
(or)
A network of wires drawn connecting the meter board
to the various energy consuming loads (lamps, fans,
motors etc) through control and protective devices for
efficient distribution of power is known as electrical
wiring.

DISTRIBUTION OF ELECTRICAL POWER TO
CONSUMERS
Following supply system is normally is used
for distributing electrical power to consumers.
1. Single-phase two-wire system.
2. Three-phase four-wire system.
3. Three phase three wire system.

SINGLE-PHASE TWO-WIRE SYSTEM(DOMESTIC WIRING)
 For domestic consumers, the most commonly used
system is 1-phase 2-wire system(230V).
 Which is often derived from a 400V, 3-phase 4-wire
system.
 Groups of consumers are connected between one
phase line and the neutral conductor, thus providing
230V, 50Hz, 1-phase supply.
 The consumers- groups are arranged such that the
loads on the three phases remain balanced.

THREE-PHASE FOUR-WIRE SYSTEM(INDUSTRIAL
WIRING)
 For large industrial consumers, particularly those
using heavy motor loads and drawing more than
1 MVA, the power is supplied from a three phase
system at high voltage, such as 6.6kV, 11kV, or 33kV.
 The consumer has its own substation to distribute
power at appropriate voltages at different locations
within his premises.

THREE-PHASE THREE-WIRE SYSTEM(Transmission WIRING)
Because there's no need to run a neutral wire for
transmission service, and it saves on materials
cost.
 Four-wire systems are only useful where single-
phase loads are involved, really. Transmission is
always balanced three-phase(Delta).
So, using 3 wire system is economical and also
results in lesser power loss.

Single and Three Phase Distribution System

DIFFERENCE BETWEEN NEUTRAL WIRE AND GROUND
WIRE
Neutral carries current equal to that carried by
the phase wire.
 Neutral is a circuit conductor that normally
carries current back to the source(return path
for the phase wire) and is connected to ground
(earth) at the main electrical panel.
Ground is there for safety, and it should -never-
carry current except when something has failed(it
should only carry the leakage current).
Even though both Neutral and Ground are
attached to the same point inside the breaker box.

SWITCHES
“An electromechanical device used to connect
or disconnect a circuit is known as Switch.”
The moving part of a switch used to connect
or disconnect a circuit is called a Pole.

SWITCHES TYPES
1. Single Pole single throw switch.
2. Single pole double throw switch.
3. Double pole single throw switch.
4. Double pole double throw switch.

1. SINGLE POLE SINGLE THROW SWITCH(SPST)
 This is a simple ON/OFF switch. It is also called as One Way
Switch (in the US, they called it Two-Way Switch).
Example: light switch, fan switch etc.

2.SINGLE POLE DOUBLE THROW SWITCH (SPDT)
A simple changeover switch: COM( Common) is connected to A
or to B. This button has three pins in which, one pin is used as
common and called a Two-Way Switch (in US, they called it Three-
Way Switch).
For example: SPST switch is used to control two different
circuits etc.

 When the switch A is closed, then the current flows
through the terminals, but only light A will glow and
light B will OFF.
 When the switch B is closed, then the current flows
through the terminals and only light B will glow and
light ‘A’ will OFF.
 Here two circuits will be controlled through one
source or one way.

DOUBLE POLE SINGLE THROW SWITCH(DPST)
A Double Pole Single Throw Switch has a lot of versatility
being that it accepts 2 inputs, which makes it then be able to
drives 2 different outputs in a circuit.
What it drives depends on the circuit design and what the
circuit is intended to do. But DPST have enormous applications
in circuits.
For Example:

We can see from the circuit, how a DPST switch
can be used to put a circuit in any of 1 of 2
modes.
When the switch is connected one way (circuit A),
the lamp and LED will both be ON. When
connected the other way(circuit B), the lamp and
the LED are both OFF.
So a DPST switch allows for control of 2
outputs(2 circuits), turning either both on or
both off together.

3.DOUBLE POLE DOUBLE THROW SWITCH (DPDT)
This switch is equal to two SPDT switches, it means
two separate circuits, connecting two inputs of each
circuit to one of two outputs.

 Circuit A is connected to a lamp and an LED. When is
the switch is one way, the lamp is on and the LED is off.
When the switch is flipped the other way, the LED is on
and the lamp is off.
 Circuit B is connected to a buzzer and a speaker. When
the switch is one way, the buzzer is on and the speaker is
off. When the switch is flipped the other way, the speaker
is on and the buzzer is off.
 This shows the dynamic 2-mode capacity that DPDT
switches allow, allowing control of 4 different devices.

FACTOR AFFECTING THE CHOICE OF WIRING
1. DURABILITY: Type of wiring selected should confirm to standard specifications,
so that it is durable i.e. without being affected by the weather conditions, fumes etc.
2. SAFETY: The wiring must provide safety against leakage, shock and fire hazards
for the operating personnel.
3. APPEARANCE: Electrical wiring should give an aesthetic appeal to the interiors.
4. COST: It should not be prohibitively expensive.
5.ACCESSIBILITY: The switches and plug points provided should be easily
accessible. There must be provision for further extension of the wiring system, if
necessary.
6.MAINTENANCE COST: The maintenance cost should be a minimum.
7.MECHANICAL SAFETY: The wiring must be protected against any mechanical
damage.

DIFFERENCE BETWEEN A WIRE AN A CABLE
 Many are often confused, but in fact, they are quite
different.
 A wire is a single conductor(material most
commonly being copper or aluminium).
While a cable is two or more insulated wires
wrapped in one jacket.
Multiple conductors that have no insulation
around would be classified as a single conductor.

SPECIFICATION OF WIRES:
 Electrical wire is specified by the
a. Conductor material
b. Insulation
c. Size
d. The number of cores.
 These are important parameters as they determine the current
and voltage handling capability of the wires. The conductors
are usually of either copper or aluminum.
 Various insulating materials like PVC(Poly vinyl chloride),
TRS, and VIR(Vulcanized India Rubber) are used. The
wires may be of single strand or multi strand.
 Wires with combination of different diameters and the number
of cores or strands are available.

 For example: The VIR conductors are specified as 1/20,
3/22,….7/20 ………
 The numerator indicates the number of strands while the
denominator corresponds to the diameter of the wire in
SWG (Standard Wire Gauge).
 SWG 20 corresponds to a wire of diameter 0.914mm, while
SWG 22 corresponds to a wire of diameter 0.737 mm.
 A 7/0 wire means, it is a 7-cored wire of diameter 12.7mm
(0.5 inch).
 The selection of the wire is made depending on the
requirement considering factors like current and voltage
ratings, cost and application.

EXAMPLE: IN CASE OF DOMESTIC WIRING
APPLICATION
1. Lighting - 3/20 copper wire
2. Heating - 7/20 copper wire

INTRODUCTION TO WIRE
Wires is a substance or object used to transmit
the electricity.
For domestic wiring the most extensively used
conductor material is aluminum and copper
which are properly insulated.
Wires used for ordinary purpose are of single
strand e.g. connection of light, fan where
current rating is below 5 Amp.
But for the power circuit such as mixer point,
refrigerator point , iron point etc where current
may flow more than 5 Amp in such cases
multistrand wires are used.

TYPES OF WIRES
1. V.I.R.(Vulcanized Indian rubber) WIRES
2. C.T.S. (Cab Tire sheathed) WIRES
3. P.V.C.(Poly vinyl chloride) WIRES
4. Lead alloy sheathed wires
5. Weather proof wires
6. Flexible wires

VULCANIZED INDIAN RUBBER
A VIR wire mainly consists of a tinned conductor
having rubber coating. Tinning of conductor
prevents the sticking of rubber to the conductor
and also avoid corrosion.
Cotton bradding is done over rubber insulations
protect against moisture.
Thickness of rubber mainly depends on the
operating voltage to which wire are designed.
Now a days these wires are not used because
better quality of wires available at cheaper price.

CAB TIRE SHEATHED WIRE
This type of wires is a modification of VIR wires.
It consists of ordinary rubber coated conductors
with an additional tough rubber(Cab tire was the
same rubber formula used for car tyres, making
this cable a very tough rubber cable).
This layer provide better protection against
moisture and wear and tear.
These wires generally available in single, two or
three conductors.

LEAD ALLOY SHEATHED WIRES
 No effect of moisture on it.
 It used where there is moisture presence.
 These wire used for damp places or wet places.
 Wire is covered with lead sheaths. The layer of
covering is very thin like 0.12 cm thick.
 These wires provides little mechanical protections to
the wires.

WHEATHER PROOF WIRES
These types of wires are used outdoor .
The conductor is covered with three braids of
fibrous yarn.
It made waterproof by drooping it into
waterproof compound.

POLY VINYL CHLORIDE WIRE
1. Dielectric strength is more(the maximum voltage
that can be applied to a given material without
causing it to break down).
2. Mechanical strength is more. 3.Life is long.
4. Protect against flame. 5.Protect against oil, alkali.
6. PVC wire is widely used.

FLEXIBLE WIRES
These wire consists of number of strands
instead of a single conductor.
The conductor is insulated with PVC material.
These wires are very useful for household
portable appliances where flexibility of wire is
more important.

SYSTEMS OF WIRING
1. Cleat Wiring
2. Wooden casing and capping Wiring.
3. C.T.S(Cab tire sheathed) or T.R.S(Tough
rubber sheathed) Wiring.
4. Lead sheathed or metal sheathed Wiring.
5. Conduit Wiring.

1.CLEAT WIRING
 Cleat wiring is normally used for temporary wiring
purposes.
 It is quite suitable for taking a temporary connection,
such as for function, marriages, etc.
 In this type V.I.R or P.V.C wires are clamped
between porcelain cleats.
 The cleats are made in pairs having bottom and top
halves. The bottom half is grooved to receive the
wire and the top half is for cable grip.
 Initially the bottom and top cleats are fixed on the
wall loosely according to the layout. Then the cable is
drawn, tensioned and the cleats are tightened by the
screw.

 Cleats are of three types, having one, two or three
grooves, so as to receive one, two or three wires. Two
types of cleats.
 The gutties should be fixed into the wall at regular
intervals of about 15cm.
 The screws used are of size 38-40mm length. For
250 volts supply cables will be placed 2.5cm apart
centre to centre for single core cables.
 Only one cable is passed through each groove of the
cleat.
 While screwing too much pressure should not be
applied so that its insulation remains intact.
The use of cleat wiring system
is over nowadays.

o ADVANTAGES
1. It is the cheapest system of internal wiring.
2. The installation and dismentling is simple and fast and
hence is very useful for temporary wiring.
3. The cable can be inspected easily and if there is any
problem with the wiring the same can be rectified without
much problem.

o DISADVANTAGES
1. It is not good looking i.e. this method does not
give attractive appearance. After some time due
to sagging at some places, it looks shabby.
2. Dust and dirt collects on the cleats, because the
wires are directly exposed to atmospheric
conditions like moisture, chemical fumes etc.
3. Maintenance cost is very high.
4. Life span is very short.
5. It can be only used on 250/440 Volts on low
temperature.
6. There is always a risk of fire and electric shock

FIELD OF APPLICATION
1. The wiring of this type is very suitable for
temporary installations in dry places.
2. This is also accepted where appearance is
not so important and cheapness is the main
consideration.

2.WOODEN CASING AND CAPPING WIRING
 Casing and Capping wiring system was famous wiring
system in the past but, it is considered obsolete this
days because of Conduit and sheathed wiring system.
 This is one of cheapest types of wiring and is
commonly used for house wiring.
 The cable used in this type of wiring is either V.I.R or
P.V.C cables or any other approved insulated cables.
 The casing and capping can be done form two parts of
the wooden or PVC, the casing and capping have
grooves.

The cables were carried through the wooden
casing enclosures. The casing is made up of a
strip of wood with parallel grooves cut length
wise so as to accommodate VIR cables.
The grooves were made to separate opposite
polarity, the capping (also made of wood) used to
cover the wires and cables installed and fitted in
the casing.

o ADVANTAGES
1. PVC casing capping gives better look and is
economical as compared to wood and even more better
than cleat wiring.
2. It is relatively cheaper as compared to conduit but
costlier as compared to cleat-wiring.
3. Physical inspection of wiring makes it simple to carry out
repair if required (by opening the capping).
4. Short-circuit of wire i.e between phase and neutral is
avoided as the two are placed in different grooves.

o DISADVANTAGES
1. Normally not recommended for damp places.
2. In case of short circuit, there is risk of
fire(use of wood or PVC).
3. This type of wiring can be used only on
surface and cannot be concealed in plaster.
4. Since it requires better workmanship, labour
cost is more.
5. White ants may damage the casing &
capping of wood.

FIELD OF APPLICATION
• This type of wiring is suitable for low voltage
domestic installations in dry places and where
there is no risk of fire hazard.

C.T.S or T.R.S Wiring or Batton Wiring
• This type of wiring is also used for house wiring
and is quite cheap.
• Cab tire sheathed wire or rubber sheathed wire is
normally used on the conductor for this wiring.
• The wires are run on the teak wooden battons
which are fixed on the wall or the ceiling by
means of screws and wooden pluge.
• Straight teak wooden batten (at 10 mm thick)

 Here the conductors (two or three) are individually
insulated and covered with a common outer lead-
aluminum alloy sheath.
 The sheath protects the cable against dampness,
atmospheric extremities and mechanical damages.
 The sheath is earthed at every junction to provide a
path to ground for the leakage current.
 They are fixed by means of metal clips on wooden
battens.

o ADVANTAGES
1. Wiring installation is simple and easy.
2. Cheap as compared to other electrical wiring systems.
3. Repairing is easy.
4. Strong and long-lasting.
5. less chance of leakage current in batten wiring
system.

o DISADVANTAGES
Can’t be installed in open and outdoor areas.
High risk of fire.
Heavy wires can’t be used in batten wiring
system.
Only suitable below then 250V.

FIELDS OF APPLICATION
These cables are moisture and chemical proof.
They are suitable for damp climate but not
suitable for outdoor use in sunlight.
TRS wiring is suitable for lighting in low
voltage installations.

METAL SHEATHED WIRING
 This type of wiring is also adopted for low voltage
installation.
 This system is more or less similar to C.T.S wiring
except that the cable used is different in this wiring
system.
 In this system conductors used are insulated with V.I.R
and then covered with an outer sheath of lead
aluminium alloy containing 95% lead and 5%
aluminium.
 The metal sheath given protection to cables from
mechanical damage, moisture and atmospheric
corrosion.

 The whole lead covering is made electrically
continuous and is connected to earth at the point of
entry to protect against electrolytic action due to
leaking current and to provide safety in case the
sheath becomes alive.

o ADVANTAGES
1. Conductors are protected against mechanical injury.
2. It is suitably employed under damp situations.
3. It has longer life.
4. Conductors are protected against chemicals.
o DISADVANTAGES
1. Cables are costlier then C.T.S or T.R.S wires.
2. In case of leakage, there is every risk of shock.
3. Skilled labour and proper supervision is required.

1. This wiring system is suitable for low voltage
installations.
2. It may be used in places exposed to sun and
rain provided no joint is exposed.

CONDUIT WIRING
Conduit wiring system is the best for domestic
and commercial installations.
It provides proper protection to the installation
against fire hazards, shock, mechanical damage
and dampness.
The cable used in this system is either V.I.R or
P.V.C insulated and is run in mild steel or P.V.C
pipes called as conduits.
Conduit wiring is divided into types :
1. Surface Conduit wiring.
2. Concealed Conduit Wiring.

Surface conduit wiring
•PVC, or metallic conduit are
used.
•PVC, VIR wire are used.
•Appearance is good.
•It protect wire against
mechanical damage, Moisture,
dust.

Concealed conduit wiring:
•PVC, or metallic conduit are
used Conduit inside the wall
•Appearance is good
•Protect against fire dust
moisture mechanical damage,
•Less maintenance
•Less chance of Fault
•Cost is high

In conduit wiring, the conduits can be steel or PVC
conduits tubes.
 In case of steel conduit then the conduits should be
electrically continuous and connected to earth at some
suitable points.
Conduit wiring is a professional way of wiring a
building. Mostly PVC conduits are used in domestic
wiring and are buried in walls under plast.

 VIR or PVC cables are afterwards drawn by means of
a GI wire of size if about 18SWG.
The conduit protects the cables from being damaged
by rodents (when rodents bites the cables it will cause
short circuit) that is why circuit breakers are in place
though because Prevention is better than cure.

o Advantages
1. Conduit provides protection against mechanical
injury and fire.
2. The whole system is water proof.
3. Conductors are safely secured from moisture &
rodents.
4. Good appearance.
5. Relatively longer life.
o Disadvantages
1. It is costly system of wiring.
2. It requires more time for erection.
3. It requires highly skilled labour.

As this system of wiring provided protection against
fire, mechanical injury and dampness, this is the only
approved system of wiring for:
1. Damp situations.
2. In domestic places such as home lighting etc.
3. Where important documents are kept such as
a record room.

WHY TO MAKE WIRE A MOISTURE
PROOF?.
 Occasionally in humid conditions insulation will
absorb the humidity from the atmosphere and can
cause IR failures.
When wire insulation absorbs water or water
vapor, electricity begins to leak (water is a
conductor) between wires that are next to each
other or to a shield.
The more water absorbed, the worse the problem.

ELECTRIC WIRING SYSTEMS
For domestic wiring, there can be following two
systems of wiring.
1. Tree System of Wiring
2. Distribution System of Wiring

TREE SYSTEM OF WIRING
 It is one of the cheaper and simple system of wiring.
 The live and neutral wires are run throughout the
house.
 The branch circuits are tapped wherever needed.
 After removing the insulation of the main wires, the
branch-circuit wires are joined. An insulation tape is
wrapped around the joint.

DISADVANTAGES OF TREE SYSTEM OF WIRING
1. Poor appearance.
2. Frequent occurrence of faults due to many joints.
3. Difficulty in locating faults.
4. Scattered fuses.
APPLICATION
This system is not suitable for regular
long lasting domestic wiring. However, we may use it
for temporary wiring such as for a marriage pandal.

DISTRIBUTION SYSTEM OF WIRING
The live and neutral main wires are first taken
to one or more convenient distribution boards.
Each branch circuit is then separately taken out
from the distribution board.
DISADVANTAGES
 This system requires more length of wire and hence it
is costlier than the tree system.

Because of the following advantages, this system of
wiring is normally adopted for domestic wiring now-a-
days.
1. Good appearance.
2. Fault in one circuit does not affect the other circuits.
3. Easy to locate faults.
4. Each circuit protected independently by a fuse or MCB.
5. Simple system capable of further extension, if required.
6. Easy to replace blown fuse, or to restore the MCB.

SIMPLE CONTROL CIRCUITS IN DOMESTIC
INSTALLATION
Various lighting control circuits have been developed
for maximum convenience and economical use of
electric lighting.
• The domestic lighting circuits are quite simple and
they are usually controlled from one point.
• But in certain cases it might be necessary to
control a single lamp from more than one
point(Two or Three different points).
FOR EXAMPLE: Staircase lightning, long corridors,
large halls lightning etc.

TWO-WAY CONTROL OF LAMP
Two-way control is usually used for staircase lighting.
The lamp can be controlled from two different
points: one at the top and the other at the bottom -
using two- way switches which strap wires
interconnect.
They are also used in bedrooms, big halls and large
corridors.
Always the switches are connected in phase wire
not in the neutral wire.

THREE- WAY CONTROL OF A LAMP
 Some times it may be required to control the lamp from
three different places.
 Examples are long corridors, big godowns, workshops
etc.
 To achieve this along with 2 two-way switches, an
intermediate switch is used.
 The intermediate switch will be having four terminals.

CONNECTORS
• “A conductive device used for connecting
electrical circuits by means of wires and
cables.”
• Wires and cables are connected using
permanent and temporary connections.
• Seperable connections are used when circuits
can be connected to other electrical
components.

Domestic wiring

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