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All conductors and switches and other accessories should be having a rating such that they are not exceeded under any circumstance of use. This may be calculated knowing the rating (W) of the lights, fans and equipment connected. The size of the conductor of the circuit should be chosen so as to permit only minimum voltage drop form the inlet to any point in the installation. In each circuit or sub-circuit the fuse shall be such as to match the cable rating to ensure desired protection.

In the case of concealed wiring, installation should begin immediately on completion of the main structural work and before finishing works such as plastering. In the case of surface wiring, it can be carried out after plastering. Generally, installation should not start before the building is reasonably weatherproof.

However, where electrical wiring is to be concealed within the structure as in a RCC building, the necessary conduits or ducts shall be positioned firmly and tied to the reinforcement before concreting. When shutters are removed after concreting, the conduit ends shall be sealed by caps to protect them from getting blocked.

All conduit openings and junction box openings should be protected against entry of muck or mortar during construction.

Conductors for all internal wiring may be of copper. The conductor for final sub-circuit for fan and light wiring should be not less than 1.5 mm2 of copper and for power cable not less than 4.0 mm2 of copper. In existing buildings it is advisable to replace wiring which is more than 30 years old as the insulation in it would have deteriorated. This will be in a state to cause failure leading to short circuit on the slightest of either mechanical or electrical disturbances.

Earthing is required to by-pass the over-rated current caused due to fluctuation in circuit parameters such as phase frequency and line voltage etc., to save human life and electrical assets from short circuits.

Fuse is a conditional switch having fuse wire of low melting point required to save the electrical network in case of overloads and short circuits. Short circuit occurs due to accidental contact of phase with another phase or phase with neutral or phase with earth wire.

Use of RCCB/ ELCB (residual current circuit breaker/ earth Leakage circuit breaker) prevents the accidental shocks and also keeps a check on the earthing system of the house. In case of leakage of very small current in milli-amperes, it would trip the circuit and prevent the mishap.

Concealed wiring is safe for the building as long as it is properly placed and joints are properly covered. There should be tap holes for checking the wiring at suitable intervals. The wiring should not be too close to the slab and also from the wet areas in the building.

The wiring should not be exposed to external cracks in the walls. While concealing and embedding inserts into a structural member, care should be exercised to see that the member is not made weaker. A six inch switch box cannot be inserted into a nine inch column.

Thus the benefits of greater personal and equipment safety, reliability, current load capacity, discharge path for short circuits, fault current/surge protection, stable earth values, low resistance, longer life, and low cost maintenance can all be achieved by proper installation of electric wiring.

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