WHATE IS ELECTRICAL WIRING ? FACTOR AFFECTING CHOICE OF WIRING ? TYPES OF WIRING USED IN BUILDINGS AND RESIDENTS ?
Electrical wiring is generally refers
to insulated conductor used to carry current
and associated device. This article
describes general aspects of electrical wiring as used to provide power in
buildings and structures, commonly referred to as building wiring.
Types of wiring according to uses
1. Domestic wiring.
2. Commercial
wiring.
3. Industrial
wiring.
FACTOR AFFECTING THE CHOICE OF WIRING:
1.Durability:
Type
of wiring selected should conform 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
Types of Wiring
§ Cleat wiring
§ CTS wiring or TRS wiring or batten
wiring
§ Metal sheathed wiring or lead
sheathed wiring
§ Casing and capping
§ Conduit wiring
Cleat Wiring:
Introduction
The types of wiring to be adopted is
dependent on various factors, viz, durability, safety, appearance, cost,
consumer’s budget etc.
Cleat Wiring
This System uses insulated Cables sub
protected in porcelain cleats
Cleat wiring is recommended only for
temporary installations. 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.
Cleat wiring is one of the cheapest wiring
considering the initial cost and labor, and is most suitable for temporary
wiring. This wiring can be quickly installed, easily inspected and altered.
When not required, this wiring could be dismantled without damage to the
cables, cleats and accessories.
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
joist, 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 witch they are passing.
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, conductors shall
not be less than 2.5 cm apart, centre to centre, and in the case of sub-mains
not less than 4 cm apart, centre to centre. 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 ensure that grooves f porcelain cleats
are essential and the difference in size shall be reasonable. Care should also
be taken ensure that grooves of porcelain cleats do not compress the insulation
nor be too wide for a loose fit. Under no circumstances two wires shall be
placed in one groove of the porcelain cleats.
Advantages:
1) Easy installation.
2) Materials can be
retrieved for reuse.
3) Flexibility provided
for inspection, modifications and expansion.
4) Relatively economical.
5) Skilled manpower not
required.
Disadvantages:
1) Appearance is not
good.
2) Open system of wiring
requiring regular cleaning.
3) Higher risk of
mechanical injury.
Batten Wiring
In this wiring system, wires sheathed in
tough rubber are used which are quite flexible. They are clipped on wooden
battens with brass clips (link or joint) and fixed on to the walls or ceilings
by flat head screws.
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.
Advantages:
1. Easy installation and is durable
2. Lower risk of short circuit.
3. Cheaper than casing and capping system of wiring
4. Gives a good appearance if properly erected.
Disadvantages:
1.
Danger of mechanical injury.
2. Danger of fire hazard.
3. Should not be exposed to direct sunlight.
4. Skilled workmen are required.
Metal Sheathed or Lead Sheathed wiring:
The wiring is similar to that of CTS but
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. The wiring system is very
expensive. It is suitable for low voltage installations.
Precautions to be taken during installation:
1. The clips used to fix the cables on battens should not react with
the sheath.
2. Lead sheath should be properly earthed to prevent shocks due to leakage
currents.
3. Cables should not be run in damp places and in areas where chemicals (may react
with the lead) are used.
Advantages:
1.Easy
installation and is aesthetic in appearance.
2.Highly durable.
3.Suitable in
adverse climatic conditions provided the joints are not exposed.
Disadvantages:
1. Requires skilled labor.
2. Very expensive.
3. Unsuitable for chemical industries.
Casing and Capping:
It consists of insulated conductors laid
inside rectangular, teakwood or PVC boxes having grooves inside it. A
rectangular strip of wood called capping having same width as that of casing is
fixed over it. Both the casing and the capping are screwed together at every 15
cms. Casing is attached to the wall. Two or more wires of same polarity are
drawn through different grooves. The system is suitable for indoor and domestic
installations.
Advantages:
1.Cheaper than
lead sheathed and conduit wiring.
2.Provides good
isolation as the conductors are placed apart reducing the risk of short
circuit.
3.Easily
accessible for inspection and repairs.
Since the wires are not exposed to
atmosphere, insulation is less affected by dust, dirt and climatic variations.
Disadvantages:
1. Highly
inflammable.
2. Usage of
unseasoned wood gets damaged by termites.
Skilled workmanship required
Conduit wiring:
In this system PVC (polyvinyl chloride) or
VIR cables are run through metallic or PVC pipes providing good protection
against mechanical injury and fire due to short circuit. They are either
embedded inside the walls or supported over the walls, and are known as
concealed wiring or surface conduit wiring (open conduit) respectively. The
conduits are buried inside the walls on wooden gutties and the wires are drawn
through them with fish (steel) wires. The system is best suited for public
buildings, industries and workshops.
Advantages:
1. No risk of fire
and good protection against mechanical injury.
2. The lead and
return wires can be carried in the same tube.
3. Earthing and
continuity is assured.
4. Waterproof and
trouble shooting is easy.
5. Shock- proof
with proper earthing and bonding
6. Durable and
maintenance free
7. Aesthetic in
appearance
Disadvantages:
1. Very expensive
system of wiring.
2. Requires good
skilled workmanship.
3. Erection is
quiet complicated and is time consuming.
4. Risk of short
circuit under wet conditions (due to condensation of water in tubes).
Specification of Wires:
The conductor material, insulation, size
and the number of cores, specifies the electrical wires. 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, TRS, and VIR 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: Application: domestic wiring
1.Lighting -
3/20 copper wire
2.Heating - 7/20
copper wire
The enamel coating (on the individual
strands) mutually insulates the strands and the wire on the whole is provided
with PVC insulation. The current carrying capacity depends on the total area of
the wire. If cost is the criteria then aluminum conductors are preferred.
In that case, for the same current rating much larger diameter of
wire is to be used.
SWITCHES:
In electrical engineering, a switch is an electrical component that can break an electrical circuit, interrupting the current
or diverting it from one conductor to another.
The most familiar form of switch is a
manually operated electromechanical device with one or more sets of electrical contacts, which are connected to
external circuits. Each set of contacts can be in one of two states: either
"closed" meaning the contacts are touching and electricity can flow
between them, or "open", meaning the contacts are separated and the
switch is nonconducting.
The mechanism actuating the transition between these
two states (open or closed) can be either a "toggle" (flip switch for
continuous "on" or "off") or "momentary"
(push-for "on" or push-for "off") type.
A switch may be directly manipulated by a
human as a control signal to a system, such as a computer keyboard button, or
to control power flow in a circuit, such as a light
switch. Automatically operated switches can be used to control the motions
of machines, for example, to indicate that a garage door has reached its full
open position or that a machine tool is in a position to accept another work
piece. Switches may be operated by process variables such as pressure,
temperature, flow, current, voltage, and force, acting as sensors in a
process and used to automatically control a system. For example, a thermostat
is a temperature-operated switch used to control a heating process
A switch
that is operated by another electrical circuit is called a relay. Large switches
may be remotely operated by a motor drive mechanism. Some switches are used to
isolate electric power from a system, providing a visible point of isolation
that can be padlocked if necessary to prevent accidental operation of a machine
during maintenance, or to prevent electric shock.
In circuit theory:
An ideal switch would have no voltage drop
when closed, and would have no limits on voltage or current rating. It would
have zero rise
time and fall
time during state changes, and would change state without
"bouncing" between on and off positions.
Practical switches fall short of this
ideal, and have resistance, limits on the current and voltage they can handle,
finite switching time, etc. The ideal switch is often used in circuit analysis
as it greatly simplifies the system of equations to be solved, however this can
lead to a less accurate solution. Theoretical treatment of the effects of
non-ideal properties is required in the design of large networks of switches,
as for example used in telephone exchanges.
Various Type OF Switches:
SPST:
Single Pole Single Throw: A simple on-off
switch: The two terminals are either connected together or disconnected from
each other. An example is a light switch.
SPDT:
Single pole, double throw: A simple
changeover switch: C (COM, Common) is connected to L1 or to L2.
SPCO, SPTT:
Single Pole Change Over OR Single Pole
Centre OFF OR Single Pole Triple Throw: Similar to SPDT. Some suppliers use
SPCO/SPTT for switches with a stable off position in the centre and SPDT for
those without.
DPST:
Double Pole Single Throw: Equivalent to two
SPST switches controlled by a single mechanism.
DPDT:
Double pole Double Throw: Equivalent to two
SPDT switches controlled by a single mechanism.
DPCO:
Double Pole Change Over OR Double Pole
Centre OFF: Equivalent to DPDT. Some suppliers use DPCO for switches with a
stable off position in the centre and DPDT for those without.
INTERMEDIATE SWITCH:
DPDT switch internally wired for
polarity-reversal applications: only four rather than six wires are brought
outside the switch housing.
MANUFACTURING COMAPNIES:
ANCHOR SWITCHES:
HAVELLS SWITCHES:
AC POWER PLUG AND SOCKETS:
AC power plugs and sockets are devices that
allow electrically operated devices to be connected to the primary alternating current (AC) power
supply in a building. Electrical plugs and sockets differ in voltage and current rating,
shape, size and type of connectors. The types used in each country are set by
national standards.
Generally the plug is the movable connector
attached to an electrically operated device's mains cable,
and the socket is fixed on equipment or a building structure. Plugs have male circuit contacts, while
sockets have female contacts. The plug has protruding prongs, blades, or pins
that fit into matching slots or holes in the socket. A socket is also called a
receptacle, outlet, or power point (British English). It may be surrounded by a
cover called a wall plate, face plate, outlet cover, socket cover, or wall
cover.
To reduce the risk of electric
shock, plug and socket systems can incorporate safety features. These may
include socket design intended to accept only compatible plugs inserted in the
correct orientation; plugs with insulated sleeves on contact pin shanks so a
partially inserted plug does not bear exposed live pins that could be touched;
or sockets with blocking shutters that open only when a compatible plug is
inserted. Sockets are designed to prevent exposure of bare live contacts. The
exposed contacts present in some sockets are used exclusively for earthing (grounding).
ANCHOR SOCKETS:
HAVELLS SOCKET:
COMPARISON BETWEEN PRICE OF THREE
MANUFACTURING COMPANY
Sr
No.
|
ANCHOR
|
HAVELLS
|
WIPRO
|
COMMENTS
|
1.
|
1-WAY
SWITCH
20A-250V
Rs.207
|
1-WAY
SWITCH
10A-250V
Rs.101
|
1-WAY
SWITCH
6A-250V
Rs.101
|
HAVELLS
IS BEST WITH MEDIUM RATING AND RESONABLE PRICE
|
2.
|
2-WAY
SWITCH 20A-250V
Rs.256
|
2-WAY
SWITCH 10A-250V
Rs.140
|
2-WAY
SWITCH 6A-250V
RS.122
|
WIPRO
IS BEST WITH RESONABLE PRICE
|
3.
|
1-WAY
SWITCH WITH LED
20A-250V
Rs.247
|
1-WAY
SWITCH WITH LED
10A-250V
Rs.140
|
1-WAY
SWITCH WITH LED
6A-250V
Rs.133
|
AGAIN
WIPRO IS BEST WITH RESONABLE PRICE
|
4.
|
2-WAY
SWITCH WITH LED
20A-250V
Rs.272
|
2-WAY
SWITCH WITH LED
6A-250V
Rs.172
|
WIPRO
IS BEST WITH RESONABLE PRICE
|
Sr No.
|
ANCHOR
|
HAVELLS
|
WIPRO
|
COMMENTS
|
1.
|
2 PIN 16A/250V SOCKET
Rs.332
|
6A 2 PIN SOCKET
Rs.100
|
6A 2/3PIN SOCKET
Rs.170
|
HAVELLS IS BEST FOR IT LOW PRICE
|
2.
|
2 PIN +E
16A/250V
Rs.346
|
6A 3 PIN SOCKET
Rs.141
|
6A 2 AND 3 PIN SOCKET
Rs.240
|
HAVELLS IS BEST FOR IT LOW PRICE
|
3.
|
6A-16A SOCKET
Rs.367
|
6-16A 3 PIN SOCKET
Rs.230
|
6/16A 6 PIN SOCKET
Rs.265
|
AGAIN
HAVELLS IS BEST FOR IT LOW PRICE
|
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