The main purpose of a spur is adding an extra socket on to an existing ring main circuit.
Ring main socket wiring diagram.
The first image is how the back of your double socket should look and the second is the wiring for a spur.
The ring starts at the consumer unit also known as fuse box distribution board or breaker box visits each socket in turn and then returns to the consumer unit.
Three or four cables normally indicate a socket on a main ring circuit with one or two spurs running from it.
The ring main is typically 32a in rating which allows it to power an area of 100 square metres.
They are not so common in the uk but are used extensively abroad as the ring main or final ring circuit does have it s drawbacks.
Its simplicity makes it a great arrangement for that use.
Ring circuits are commonly used in british wiring with socket outlets taking fused plugs to bs 1363 because the breaker rating is much higher than that of any.
Typical house wiring diagram illustrates each type of circuit.
This increases the current carrying capacity without increasing the wiring size.
A general rule for a ring main is that if you only have two cables in the back of an existing socket then it is ok to spur.
In a typical new town house wiring system we have.
As you can see it eliminates the need to wire a socket all the way back to the a consumer unit but the nearest ring main socket is used instead.
The other type of circuit used to power your home is a radial circuit.
Wiring a socket correctly in a final ring circuit or ring main.
2 such rings is typical for a 2 up 2 down larger houses have more.
If the wiring has been changed by a previous diy er it may be possible to identify any added cables and then deduce the original circuit.
Ring circuits from 32a mcbs in the cu supplying mains sockets.
Ring main circuit starts from the consumer unit connects to a number of electrical devices typically sockets and then returns to the consumer unit.
Ring main and spurs.
Ring mains as they are called are a series of cables linked together starting and terminating at the same point in a distribution board.
The cable size is important it has to be either 2 5sq mm or 4 0sq mm twin core and earth these are rated in free air at 24amps or 32amps respectively.
The ring is fed from a fuse or circuit breaker in the consumer unit.