The following assumes your house is wired conventionally, using modern materials. Old round-pin sockets should be replaced by an electrician.
Most socket outlets in modern homes are connected to what is known as a ring circuit or ring main. From a 30amp fuse or 32amp miniature circuit breaker (MCB) in the consumer unit, a length of 2.5mm² two-core-and-earth cable runs from one socket to another and then back to the consumer unit where it is connected to the same set of terminals from which it originated.
There are usually two ring circuits in the average house, one supplies power to the ground floor sockets and the other to the sockets upstairs. At each socket the cable is cut and connected to terminals behind the faceplate.
Some homes have only one or two socket outlets per room, but the number can be increased with the addition of an extension known as a spur. This comprises a single 2.5mm² cable connected to the terminals of an existing socket or to a separate junction box on the ring circuit. From there, the spur cable runs to a new socket. You can have as many spurs as there were socket outlets on the ring originally. Each original double socket counts as two.
Individual radial circuits are used to supply power to a single appliance such as a cooker or shower unit, but radial circuits can also be used to supply a number of sockets. Spurs can also be connected to this multi-outlet type of radial circuit.
A radial-circuit cable terminates at the last socket - it does nTesting the circuit
Step 1
Before testing the circuit, turn off the electricity using the main switch on the consumer unit.
Step 2
Unscrew the socket faceplate and ease it off its mounting box. Note the number of cables feeding the socket - if three cables are connected, it is safe to upgrade the socket. If two are fitted you should test the circuit.
Step 3
Disconnect all the appliances on the circuit, then remove the red-coloured live wires from the socket terminal and separate these wires. Attach a continuity tester between the two live wires - if the tester glows, the socket can be changed.
- If the tester fails to light, get a qualified electrician to test the circuit before changing the socket.
- Similarly, if only one cable is connected to the back of your single socket, have that tested by an qualified electrician to make sure it is safe to convert.
t return to the consumer unit as with a ring-circuit cable. A 2.5mm² two-core-and-earth cable is used for a floor area up to 20m² (24yds²), and the circuit must be protected by a 20amp fuse or MCB. Higher-rated fuses and cable are required for larger floor areas.
Single sockets on a ring or radial circuit can be converted to doubles or even fused triple sockets. Spur sockets can also be upgraded, provided the spur cable is serving only the one socket outlet.
Previous
