Every house is supposed to have at least two lighting circuits, each protected by a 5-amp fuse or 6-amp trip in the consumer unit. A single 5/6-amp circuit can cope with up with twelve 100-watt lamps. In a multi-stored house it is common to have at least one lighting circuit for each floor even if the number of lamps are less than 12 on each level.

Shaver units may also be connected to the lighting circuit. In case of a bathroom or a room containing a shower, the shaver unit must incorporate an isolating transformer.

Lighting cable:

The lighting circuit does not form a loop returning to the consumer unit. The consumer unit is usually connected to the first lamp, which in turn is connected to the second lamp and so on.

The cable used is a 1sq mm PVC twin core and earth rated for up to 12 amps. It consists of a red insulated core for live, black insulated core for neutral with a bare earth conductor between them. The three conductors are laid side by side within a PVC sheath. When connecting the cable, the exposed earth connector must be covered with a sleeve colored yellow and green.

The lighting cable will be routed from the consumer unit to a series of lighting points for ceiling roses or wall light fittings. The power to each lamp is connected through a wall or ceiling mounted switch. Some light units incorporate their own switch for these fittings. The power circuit is then connected directly to the fitting.

Light switches:

Most room lights are normally controlled by wall mounted toggle switches. Alternatively touch sensitive or rotary light dimmers can also be fitted. The cable normally runs down the wall conduit within the plaster.

A flush fitting wall box is sunk into the wall to take the switch. Or, alternatively a surface mounted box is fitted. Multi-switch units enable more than one light to be controlled from one position. In bathrooms and shower rooms, the switch must be a pull string type.

These switches can also be used when installing new lights. They can be easily screwed under a ceiling joist with minimal disturbance to the decorations. There is stereotype among people that pull switches are only suitable for bathrooms etc. However this limits the opportunities and therefore should be avoided.

Methods of wiring:

There are two basic methods of wiring lights – by ceiling rose and by junction box. Systems using the ceiling roses make all the connections at the ceiling rose. Though it removes the need for one junction box per lamp, it may often look more awkward.

In case of junction box system, a cable is taken to a series of junction boxes, one for each light fitting or switch. The junction boxes are usually located between the ceiling joists or under floorboards close to the switch. Junction box type connections are required for fluorescent lights and other fittings that do not use a ceiling rose.