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.
Ring mains may have spurs off them either they can be spured from an existing socket or from a junction box, there is importantly, over the whole ring, the total number of spurs must not exceed the number of socket outlets directly on the main ring. No more than two separate spurs may be connected from each outlet on the ring.
The resultant connections on the rear of the socket should look like the example below:
Where connection to a fixed appliance is required, a fused outlet unit may be fitted to the wall (rather than a plug socket) and connected into the ring main. These outlets require the correct fuse rating for the appliance and are connected to the appliance by a cable or flex. The outlet may be switched or unswitched and may be fitted with an indicator light to show when the supply is connected.
Where a flex is taken to a heater of any sort (e.g. night store heater) the flex must be of a special 'high temperature' type suitable for the elevated temperatures encountered. Use of ordinary flex will result in the insulation breaking down causing the flex to become dangerous.
A clock outlet is a similar type of unit, but with a small fuse fitted in a special plug connected to the flex. The plug may be retained in the socket by a screw or knurled thumbscrew. Though called a clock outlet, they are also suitable for other small low current appliances such as extractor fan units and door bells
D i s c l a i m e r
Whether you're starting a fresh or a competent electrical person, be sure to read and study the following pages, if you have further questions please consult a qualified electrician, it's better safe than sorry -
Don't forget - Electricity KILLS....