Wiring Remote Socket Outlets

Socket-outlets situated off the main route of the cable do not have to be connected to the actual ring cable. Instead they are usually supplied from spur cables branching off the ring. These spurs are wired in the same size cable as that used for the ring.

Connecting fixed appliances

Fixed appliances which may be connected to a ring circuit include skirting heaters, wall heaters, small water heaters and any non-portable electrical appliances having individual loadings of not more than 3000 W(13 A approx.).

Storage heaters for these are connected to separate time controlled circuits. An immersion heater must not be supplied from a ring circuit, even though the loading is no more than 3000 W. The reason is that an immersion heater is classed as a continuous load and as such would reduce the effective capacity of the ring circuit; the primary function of the latter is to supply numerous appliances in use at various times during the day and night.

Connections of fixed appliances

A fixed appliance may be connected by its flexible cord to a fused plug and socket-outlet but often it is more conveniently connected to a special fused outlet known as a fused connection unit. This used to be known as a fused spur unit.

The advantage of a fused connection unit is that the flex of the appliance is connected permanently to the unit, whereas when connected to a plug and socket-outlet someone might pull out the plug and use the socket for a portable appliance. Fused connection units are available with and without a switch and are available, if required, with a neon indicator.

Connecting spurs

A spur cable branching off a ring circuit may supply either one or two 13 A single socket-outlets, or one double socket-outlet, or one fixed appliance. Spurs from any one ring circuit are limited in number to the number of 13 A socket-outlets and fixed appliances actually wired into the ring cable.

If, therefore, there are eight socket- outlets wired into a ring circuit there may be up to a total of eight spurs branching off the ring. As each spur may supply two socket-outlets twice as many socket-outlets may be fed from spurs, as are connected to the ring cable itself. Where some of the spurs feed fixed appliances with only one on a spur, the number of spur fed socket- outlets will be less.

A spur cable may be connected to the ring cable either at the terminals of a ring socket or at a joint box wired into the ring cable at a convenient point. When adding spurs to a ring circuit it is usually better to insert a joint box into the cable under the floor rather than to break into an existing socket-outlet box. Also the terminals of a socket-outlet will not accommodate more than three cables — two for the looping ring cable and one for one spur.

Joint boxes used to connect spurs are of the 3-terminal 30 A type.

The clock connector is in two portions, one being fixed and connected to the circuit wires and the other being a form of fused plug. This is connected to the flex of the clock and secured in the fixed portion by a captive screw to prevent anyone accidentally pulling it out and stopping the clock. The fuse is usually 3 A, but sometimes a 2 A fuse is fitted.

Clock points can be supplied from spurs. Where there is more than one clock point, a fused spur is preferred and the fused connection unit at the ring cable would be a non-switched version. Clock connectors can be flush or surface mounted. The flush type can be fixed behind a wall-mounted clock.

Height of fused connection units

Fused spurs

A fused spur is a cable branching off a ring circuit similar to that of a conventional spur, except that the connection to the ring cable is at a fused connection unit (fused spur unit) instead of being solidly connected to the cable at a joint box or at the terminals of a ring socket-outlet. A fused spur can supply one or more socket- outlets, but as the total current demand of the points served by a fused spur must not exceed 13 A, only one 13 A socket-outlet can be supplied from a fused spur.

A number of sockets of lower rating may be connected to supply portable lights and small appliances. For instance, two 5 A 3-pin or six 2 A 3-pin sockets.

There is no regulation height for fused connection units. The best position is close to the appliance it serves so that the flex is as short as possible.

Some appliances are connected to the fused connection unit by fixed wiring. This should be only a short length so that anyone working on the appliance is within reach of the switch of the connection unit.

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