Materials and Devices Used in Wiring

Following are the materials and devices used in the wiring of a building.

1. Cables

Cables consist of copper of aluminium conductors surrounded by insulation. Aluminium conductors are used to reduce the cost but they are inferior in quality compared to copper cables. Now-a-days stranded wires are commonly used for better performance.

Rubber or PVC insulation may be made. In moist or wet conditions PVC insulation may fare better than rubber.

2. Fuses

Basically a fuse protects appliances and cables from damage by electrical faults. The current rating of fuses should be lower than that of the cable it has to protect. Two types of fuses are in use, viz., Rewirable or semi-enclosed fuses and cartridge fuses.

3. Miniature Circuit Breaker

Now-a-days miniature circuit breakers (MCB) are used instead of fuses. Miniature circuit breakers are single pole switches which automatically switches off when excess current flows. An MCB trips at 1.25 times its rated current capacity. It is only an overload device. But for the initial cost it has many advantages.

4. Earth Leakage Circuit Breaker (ELCB)

An electric appliance with a fault is connected to a line and if the metal parts are not earthed the metal may become live without the fuse blowing. Such a situation may cause a shock to the person touching it. On the other hand, if the metal body is earthed, then current will flow through the earth wire. In such a condition, it is advisable to use a tripping device called the earth leakage circuit breaker. It automatically trips even where a small current flows through the earth wire. This switch is connected to the neutral line of the electric supply. When it trips, the supply to the building will be completely cut off.

5. Residual Current Circuit Breaker (RCCB)

This type of breaker is much more positive protection device which can be provided instead of earth leakage circuit breaker to avoid electric shocks and current leakages. An RCCB is connected to all the three phases and the neutral. It is more expensive but provides excellent protection.