The various circuits in a dwelling are detailed below.
Lighting circuits
A lighting circuit is wired in either 1.0mm2 or 1.5mm2 cable using either of two methods. One is the loop-in system where the cable from the 5A fuse runs to each ceiling rose or other lighting fitting and terminates at the last on the circuit. From each light a cable is run to its switch which if a 2-way switch, a 3-core and earth cable is run from this switch to the second 2-way switch. The other method is the joint-box system where each light and its switch requires a separate 4-terminal joint-box. The cable from the 5A fuse runs to each joint-box in turn and terminates at the last joint-box in the circuit. From each joint-box a cable is run to the light and another cable to the switch. A lighting circuit may supply up to a maximum of 10 lighting points which is the equivalent of about 1200 watts.
Ring circuits
A ring circuit is wired in 2.5mm2 cable. The cable starts from the terminals of a 30A fuse, runs to each socket outlet it is to supply and returns to the consumer unit where it is connected to the same terminals as the first end of the cable. Cables termed spurs may branch off the ring cable at socket outlets or joint-boxes to supply remotely positioned outlets. A ring circuit may supply an area of up to 100 square meters or 7200 watts maximum load.
Socket outlet circuit
The maximum load for this type of wiring is 3000 watts.
Spur on a ring circuit
This type of wiring is effectively a branching off a ring circuit and the maximum load is the again 7200 watts.
Single appliance circuit
This type of wiring is necessary for power hungry appliances, for example electrical showers, cookers, electrical heaters.