Safety Factors of electric wiring

The function of wiring safety codes is to give technical, performance and material standards that would allow proper use of the electrical energy. Materials required for wiring a building depend on factors like rating of the circuit, type of occupancy of the building, type of electrical system, national and local regulations and conditions in which the wiring must operate. The design and planning of an electrical wiring installation involve consideration of all prevailing conditions such as the type of supply, envisaged load, earthing arrangements, safety aspects and energy conservation. It is essential that adequate provision is made for all services such as lighting, power requirement for A/C, fridge and kitchen heating. Proper planning will prevent the householder from relying on the use of long flexible cables and multi-plug adopters which are dangerous and not recommended.

Estimation of load requirement

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 equipments 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.

Installation

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.

Accidental shock

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 would trip the circuit and prevent the mishap.

Concealed wiring

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 6 inch switch box cannot be inserted into a 9 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 planning and installation of electric wiring.

Safety instructions

•Always buy electrical items that carry the ISI mark

•Identify locations for switchboards in advance so that they will not be an obstruction when the room is being decorated

•Proper earthing should be done for the entire house

•Each power board should have a separate fuse

•Registered electrical contractors should be engaged to carry out the electrical work

•Consumption of electricity should be need based. Try to save electricity as much as possible

•The entire network should be designed to avoid unnecessary or excess power loss during transmission