Wires
For estimating the cost of internal wiring it is necessary to known the type of wires in use. The usual way to specify the wire is with the reference to the insulation size and number of cores.
Size of wires
For conduction of electrical power insulated aluminium or copper conductor are used. There is a limit to the current carrying capacity of the aluminium conductor. The current flowing through the wire causes heat which proportioned to the sq. of the current against there is the limit to the degree of heat which a particular insulation and with stand safely. According to standards laid down there is particular value of maximum current which can be safely carried by the wires different insulators and if there rates are not adhered there is a possibility of damage to insulations which may cause fire. The wires are not refered according to the areas but numbers have been assigned to the wire size (i.e. standard wire gauge)
Types of wires
The wires used for general electrical purpose can be divided into the following
1. Rubber covered, taped, braded and compounded wires
2. Lead alloy sheated wires.
3. Though rubber sheated (T.R.S) or cab type sheated (C.T.S) wires.
4. Weather proof wires.
5. Flexible wires.
Diagram
1. Rubber covered taped, brainded and compounded wire
These wires are always single core but can be sub-divided into two classes i.e. weather meants upto 600 v or 250 v
The thickness of the rubber insulation depend up on the voltage for which the wire is required.
2. Lead alloy sheated wires
Such types are recommonded where the climatic condition is not dry but has a little bit of moisture.
3. Tough rubber sheated wires (T.R.S.)
The T.R.S. wires are provided with a tough rubber compound which does not deterorated even after long exposure to moisture such wires are also available in single core twin core and three core.
4. Cab type sheated (C.T.S.) wires
The lead sheated cables are costlies and are quite heavy in weight. The T.R.S. cables have properties similar to that of lead sheated cable but it much cheaper.
5. Wearing proof wires
The wheather proof wires are for out door purpose i.e. they run between building such type of wires consist of 3 braids of fibreous yarn provided over the copper conductors.
6. Flexible wires
The wires used for house hold applications such as heaters, irons refridgeretors, lamps etc. must be durable and very flexible. The flexibility is required firstly form the point of view of handling. The equipment secondly to prevent the wires from break. These flexible wires are also used as lamp cords.
The types of wiring to be adopted in dependent on various factors. Viz, durability, safely, appearance, cost and consumers budget etc.
Method of Insulating wiring.
There are a number of methods of insulating a wiring system. They are
1. Cleat wiring (wire in porcelain cleats)
2. T.R.S. wiring (Tough rubber sheath wires run over wooden buttons)
3. Casing cap (V.C.R. wires in wooden casings)
4. Conduct wiring (V.C.R. conductors run in conducts)
Couplings
Scince the conductors are available in smaller length so to obtain a continuous length of the conduct the two are occupied by means of coupling lighting accessories. Switches lamp holders celling roses socket outlets plugs etc.
Switches
These are various types of switches which can be classified as
a) Flush switches
b) Pull switches or celling switches
c) Push button switch
d) Industrial iron-clad switch
e) Rocker switch
f) Quick break knife switch
Lamp holder
As is clear from its name a lamp holder is used to hold the lamp required for lighting purpose. The lamp holders can be classified as
1. Bayonet Gap Lamp holders which can be further sub divided into
a) Pendant holder or coard grip-pattern
b) Button holder
c) Screwed holder
d) Porcelain lamp holders
e) Swivel lamp holders
f) Florescent lamp holders and stared holders
Diagram
Lamp holder adopter
The lamp holder adopter are used for tapping temporary power for small portable electric appliance from lamp holders.
Celling roses
The celling roses are used to provide a tapping to the pondant lamp holder through flexible wire or a connection to a fluroscent tube.
Mounting block
All the surface mounting accessories such as ceiling roses, button lamp holder surface swithes ceiling switches etc. are used in conjuction with wooden mounting block.
Socket out lets
The socket out lets have all insulated base with molded or socket base having 3 terminal sleeves. The two thin terminals sleeves meant for making connection to the cable and the third terminal sleeve thicker in cross section is used for an earth connection.
Plugs
For tapping power from socket out lets or 3 pin plugs are used. In 3 pin plug thicker pin is used for an earth connection to the portable appliance.
Main switch
In order that the consumer may have self control of the electric circuit. They must have switch. The switch is combined with fuses.
Distribution fuse boards
In the industries or in very big buildings where a number of circuits are to be wired. The distribution fuse boards become a necessity.
Fuses
The current drawn by an appliance is restricated by the resistance in the circuit in case of short circuit. The resistance left in the circuit will be that of wires on the which is negligible and thus current drawn from the main will increase to high value. The high value of current will over heat the wires and it may set fire to the building coursing grave damages to avoid this conductor (fuse wire) is provided in the circuit which breaks after the value of the current increased beyond its normal current ratings their by faulty circuit is disconnected.
Diagram
Fuse holder
The fuse holders are designed for
1. Insulation and separation of the terminal
2. Security against fire
3. Ease of replacement
Internal wiring system
Diagram
Fig. shows the wiring of a house with single phase AC. From main switch the leads known as mains are taken to main distribution board from main distribution board wires are taken to various distribution boards which are known as sub boards.
