Electricity is one energy source you can switch on where and when you want it. There is no reason to run a power tool off an extension from the kitchen when you need to work in the garage — or to unplug the bedside lamp when you want to use a portable television in the bedroom. The answer is to provide more socket outlets, a job you can do yourself safely if you follow the correct procedure.
Unless you were lucky enough to have supervised the installation of power points when your house was being built, you may find you have too few sockets and some that are in the wrong place. Moving sockets, adding extra ones or converting a single to a double (or twin) socket are jobs well within the capabilities of the amateur if you follow instructions carefully and make it a golden rule to switch off at the mains whenever you tackle any electrical work. A great part of the work is non-electrical: lifting floorboards to trace cables, drilling holes between joists for new cables or cutting back plastered walls and re-plastering them after you have buried the new cable and connected the new outlets.
Most homes take their power supply from ring circuits — but it is possible that your home’s 13amp socket outlets may be on a radial circuit. This circuit consists of a number of outlets and fixed appliances supplied by one cable, from the consumer unit, which ends at the last outlet. This is quite different from the old radial system of 15amp plugs (with round pins) in which numerous 15amp circuits radiated from a multi-way fuseboard.
These old installations are being phased out; if you still have this system, it could be in a dangerous condition and you should ask your electricity company to check the wiring — something the Electricity Council recommends people should have done every five years.
There are three ways of connecting extra sockets or fixed appliances to the domestic ring circuit, all of which can be handled by the consumer.
By taking a direct loop from the terminals of an existing socket outlet.
By inserting a junction box in the ring cable — generally under the floor — and taking one or two sockets from that.
By running a separate cable from the consumer unit.
Sockets connected by way of loops or junction boxes are called spurs; and you can take two sockets on a spur from any existing socket or from a newly installed junction box. Spurs not only supply extra socket outlets but can also be used to supply a fixed appliance, such as a wall heater.
Here a fused switch connection — placed close to the appliance — replaces a socket outlet. Some fixed connections incorporate a pilot light to show when the appliance is on. Each spur may feed one or two single socket outlets, one double (or twin) socket or one fixed appliance.
Generally there is one ring circuit for each floor in a house. You should run your loop or junction box from the nearest existing socket outlet or nearest accessible part of the ring circuit to the new outlet. If you want to run the spur from a socket, make sure the outlet is not itself a spur. Undo the screws on the front plate and gently pull the outlet from the wall box and examine the wiring. If there are two red, two black and two earth (possibly green-sleeved or bare) conductors in the box, the outlet is probably not a spur. To make quite sure examine the nearest socket outlets each side of it. If there is only one set of conductors on these, your original choice is already a spur and should not be used. If neither outlet is a spur, then you know you can loop out of the first one you examined. Replace the frontplates and switch the mains back on until you are ready to begin work.
While you are planning for extra outlets, you must decide what type of fitting you want. The choice is between flush-fitted sockets or sockets on wall-mounted boxes. More work is involved in installing the flush type, but the wall-mounted
socket can be an obstruction to furniture and vacuum cleaners at ground level and can rob you of space when fitted above a work surface.
If you are in the habit of using an adaptor plug on some of your existing outlets, it may be worth investing in a double (or twin) socket and changing that for the single while you are working on the terminals behind it.
Socket outlets should not be less than 150mm (6in) above the floor or above a working surface in the kitchen or elsewhere. In rooms being used by elderly people or active invalids, outlets should be 1 m (or 3ft) from the floor to eliminate bending.
The cable used in a ring circuit is 2.5sq mm and the usual type for domestic installations is polyvinyl chloride (pvc) sheathed twin and earth, or may be tough rubber sheathed (trs) cable. Older ring circuits are wired in the Imperial-sized cable (called 7/029), which has seven strands. But it is quite all right to use the metric-size cable when adding to a ring circuit wired with 7/029 cable.
Decide carefully where your new cable will run. There will be problems, for example, if you have a modem house or flat in which underfloor wiring on the ground floor was installed before a solid floor was laid. The costly solution to this, in terms of cable, may be that you will have to run cable from the consumer unit up to the first floor, under the floorboards and then trail it down the cavity of the wall to the position of your intended outlet. Alternatively you could bury the cable in the plasterwork (the cable does not need any additional insulation) or run it on the surface of the wall — in which case you must clad it in a plastic conduit. Surface cables look unsightly in living rooms and create a further problem when decorating.
Another method is to remove your existing skirting and replace it with ducting, in metal or plastic, designed to house cables. Never consider cutting sockets into existing skirting boards. It is dangerous, illegal and may invalidate any insurance claim in the event of a fire.
If you do have a solid floor and need only one or two extra socket outlets, you will find it simpler to loop out of an existing outlet and bury the new cable in the wall.
There are two methods of making a channel in plaster. You can do it with a club hammer and brick bolster after first scoring with a sharp knife two straight lines in the plaster along the intended cable route, chipping out the depth you require. Or you can use a specially designed router, which works off an electric drill at a slow speed. Before you start routing you must drill a series of guide holes along the intended cable route. It is unlikely your plaster will not be deep enough to take a cable, but if you are unlucky you will just have to get to work again with the chisel.
Before you start laying cable, prepare the recesses or mountings for new sockets or position the junction boxes — preferably out of sight beneath floorboards. Where you run cables across joists you should run them through holes drilled at least 50mm (2in) below the top of the joists. Never lay cable in the grooves cut in the tops of joists because of the danger from nails that may be driven through and penetrate the cables.
When replacing floorboards, use screws instead of nails, which will enable you to identify the cable run and to reach it more quickly on future occasions. Before replacing the boards you should cut out a small section of the board at the skirting board end to protect cable running up or down the wall, behind skirting and then under the boards.
Care must be taken not to damage any existing cables or pipes. Make sure current is turned off at the main; gas and water should also be turned off.
Cutting out the recess for a flush socket box is quite simple. Mark on the wall in pencil an outline of the knock-out box, score the lines with a sharp knife and, using a brick bolster and club hammer, chip away until you reach the brickwork. Drill a series of close-spaced holes all round and then chip away another layer until you reach the required depth. Test the knock-out box fits, knock out the required access holes in it (sharp taps with a cold chisel are usually enough) and fix a grommet in each hole. This is a rubber or plastic ring, with an exterior slot which fits neatly in the hole, to protect the cable. Drill the mounting holes, plug them and screw the knock-out box into the recess, making good the edges with plaster.
Fixing a wall-mounted box is much easier. You only need to channel out enough plaster to accommodate the cable run from the floorboards and behind the skirting (unless it is being channelled into a wall from another socket) and into the box, which is plugged and screwed to the wall.
Moving existing sockets
If you intend to line your rooms with plasterboard or panel boards fixed to battens, you must plan how you are going to reposition your existing outlets. If you already have wall-mounted sockets, you can cut a snug opening into your lining where each socket is situated, turning the outlets into flush fittings. If your existing outlets are flush fitting, with a knock-out box recessed into the original wall, you have several alternatives.
You can check, by easing the knock-out box from the wall, whether there is enough slack cable on the ring to allow you to move the entire outlet forward to the new surface. If there is plenty of slack, you can fit a new wall-mounted box and reconnect to the socket terminals. If there is not enough cable, check whether the cable is fed from above or below. In each instance you will probably be able to find enough cable to enable you to reposition the outlet either higher or lower than it was on the old wall. But remember, the socket
should be at least 150mm (6in) above the floor and never be installed in a skirting board.
If this is also impossible, you will have to fit a three-way terminal block into the existing knockout box, which converts it into a junction box. You must run cable from a knock-out hole (not forgetting to use a grommet) at the top or bottom of the box and use this to feed either one double or two single wall-mounted socket outlets nearby on your new wall. You must also cover the modified knock-out box with a blank plate.