The most common form of 'power' circuit used to supply the socket outlets into which portable appiances are plugged is known as the ring circuit or 'ring main'. This method of wiring consists of a loop of cable 2.5 sq. mm in cross section, that starts at the consumer unit and goes around your house, connecting socket to socket and returning back to the same terminals. This allows power to travel in both directions to the socket outlets or fused connection outlets and reduces the load on the cable.
The ring circuit runs from a 30 amp fuseway or a 32 amp MCB. It can supply appliances up to a rating of 3 kilowatts: table lamps, TVs, washing machines, portable room heaters, personal computers. Anything above that rating must have its own circuit.
The advantage of the ring circuit is that only one size and type of plug is used no matter what the appliance. There is, however, a cartridge fuse inside the plug and this should be changed according to the amount of power the appliance takes.
In theory, there is no limit to the number of socket outlets or fused 13 AMP connection units that can be fitted to one ring circuit provided that it does not serve a floor area of more than 100m sq. (120 sq. yd). This limit is based on the number of heaters, which would be required to heat the space. In practice, two-storey homes usually have one ring circuit for the upper floor and one for the lower floor. You can increase the number of sockets on the ring circuit by adding extensions known as 'spurs'.
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