Wiring up sockets

Electricity can be supplied where you want it, as long as you have enough outlets. You can install new power points or move existing ones yourself.

Having done all the non-electrical work such as lifting boards, channelling plaster to take cables, or cutting recesses for the new knock-out boxes and installing them, it is time to start wiring with 2.5sq mm twin core and earth PVC sheathed cable. This is quite simple and safe if you turn off the mains before you start work — and follow the instructions carefully.


If you are running a loop from the back of an existing socket to connect to one or two spur socket outlets or a fixed appliance, you must start by cutting your cable lengths. Since you will need to feed about 125min (Sin) of cable into the recessed knock-out boxes, wall-mounted socket outlets, junction boxes or spur socket outlets, you should remove about 100mm (4in) from the outer sheath and then strip about 15mm (tin) of the insulation material from the red and black conductors. The earth conductor will be bare and you should slip on a short length of green insulation sleeving (generally available where you buy twin core and earth cable), leaving just 15mm (kin) bare at the end.

You are now ready to run the cable into its chanelling or under the floor, depending on the route you have chosen. Cable under floors should be run in holes drilled at least 50mm (2in) below the top of joists and secured only by cable fixing clips. If you are running cable in plaster, you should wedge it in position while you are connecting up. The cable sometimes wriggles free and if this happens you should secure it with a couple of dabs of contact adhesive — but make sure the cable is in the right place.

Socket to socket

Thread the 125mm (Sin) of unsheathed conductors into the knock-out hole you have prepared (into which you must always place a rubber or plastic grommet as protection for the cable) and loosen the wires on the terminals on the back of the socket plate. Arrange the new conductors alongside the entwined pairs already there; red with reds, black with blacks and earth (or green) with earths. Put each set of three wires in their respective terminals. Reds go to the live terminal, blacks to the neutral terminal and greens to the earth terminal. All terminals are clearly marked on the back of the socket plate. Tighten the terminal screws, check the conductors are secure and replace the front of the socket outlet.

If you are wiring up only one spur socket, you simply enter the spur knock-out box in the way described and connect each of the three conductors to its relevant terminal. Screw the socket plate on, plug in an appliance that you know is working, turn on the mains and switch on at the new outlet. If the appliance works, your wiring is correct. Only then — and again with the mains switched off—should you plaster the cable into the wall or replace the floorboards.

Second spur outlet

If you are running on to a second spur outlet, follow the same wiring procedure remembering you will have two sets of wires to connect to the terminals in the first new socket — the feed conductors and earth from the original socket and the feed conductors and earth leading to the second spur outlet. When the wiring is complete, test.

Fused connection unit

Follow the same wiring procedure if you are running a loop from a socket outlet (or a junction box) to a fused (switched or unswitched) connection unit for connecting with a fixed appliance, such as a wall-mounted heater. At the connection unit there are six terminals — two live, two neutral and two earth. The live and neutral conductors from the loop cable must be connected to the terminals marked IN. The other terminals are marked OUT and to these you connect the live and neutral leads in the appliance’s flex, feeding the flex in through a knock-out hole at the bottom of the unit. The earth leads can connect to either of the two earth terminals. When this is done, check the wiring.


Check there is a 3 or 13amp cartridge fuse in the pull-out holder at the front of the unit (manufacturers sometimes forget to include one) and do not be too violent in clearing the knock-out hole or you may shatter the plastic casing. Never connect to an appliance rated at more than 13amp (or 3kW), because it will need a separate circuit from the consumer unit.

Junction boxes

If you are supplying your extra sockets or fused connection unit through a junction box, you will already have sited this within reach of the ring circuit cable and secured it to a joist, a short length of timber between joists or another suitable timber fixture. Knock out three holes: for the ring cable to enter and leave the junction box and a third for the spur cable, which should be prepared as already explained. There are three terminals in the box : live, neutral and earth. It does not matter which you use as long as you are consistent – but it is bad practice not to connect to the properly designated terminals. Try to avoid cutting the ring cable. You should be able to strip away the outer sheath and cut away enough insulation at a suitable point so there is sufficient bare wire to lay in the terminal (with the corresponding conductors from the spur cable) under the terminal screws. Connect the other end of the new cable, either to a new socket outlet or to a fixed connection unit.

Terminal block conversion

If you are turning an existing outlet into a junction box by using a three-way terminal block inside an existing recessed knock-out box or surface-mounted backplate, you must first remove a knock-out hole to get the new spur cable into the box. Connect the three sets of conductors and earths: the cable going into the existing socket and the cable leaving the socket to continue the ring circuit, and the new spur cable, which can be used to connect either one or two spur outlets or one fused connection unit. Before connecting the spur, cover the knock-out box or backplate with a blank plate.

Consumer unit connection

If you are running an extra single socket outlet or a fused connection unit (up to 13amps) direct from the consumer unit, you wire the socket or unit in the normal way — but with only one set of cdnductors. The other end of the cable is fed directly into the consumer unit and great care must be taken here because a wrong connection could cause a lot of expensive damage.

The consumer unit is clearly marked inside: the red (live) wire from your cable must be connected to a spare live terminal block, the black conductor must be connected to a spare terminal on the neutral terminal block and the earth must be connected to its corresponding place on the earth terminal block: A 15amp fuse should be inserted in the consumer unit to protect the new circuit.

Double socket

When you are replastering a single socket outlet or removing it to run off a spur, you should consider whether it is worthwhile replacing the outlet with a double (or twin) socket outlet. The terminal connections on double sockets match those on single outlets; all you have to do is exchange them.

The easiest method is to place a slim surface-mounted box over the recessed knock-out box (if you have one and provided you have enough cable). Smooth the edges of the entry hole with a file to ensure the stripped insulation does not chafe. You will probably have to secure the box to the wall with plugs each side of the old box, so take care not to drill into the ring circuit cable. If you have an existing surface-mounted box, you must remove this and replace both the backplate box and the socket outlet.

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