How to add more electrical sockets
Introduction
Replacing a socket or converting a single socket into a double are simple jobs. Sockets can be surface or flush mounted. Surface mounted electrical fittings are easier – basically a mounting box is screwed to the wall, the cable run in and the faceplate attached – but flush mounted fittings look better and are less prone to accidental damage.
For your safety, electrical products must be installed in accordance with local Building Regulations. If in any doubt, or where required by the law, consult a competent person who’s registered with an electrical self-certification scheme. Further information is available online or from your Local Authority.
Never take risks with electrical safety. Before you start any type of electrical work, follow these safety precautions:
- Switch off the main power at the consumer unit / fuse box. Isolate the circuit you plan to work on by removing the circuit fuse. Put this in your pocket to avoid losing it.
- Or switch off the breaker and lock it if you can - put a note on the unit to advise you're working on the circuit.
- Check the circuit is dead with a socket tester or voltage tester / meter for lighting circuits.
If the socket is flush mounted, it’s very easy to replace it with a surface-mounted double socket. There are special socket conversion boxes available for doing this, or you can use a standard double socket and drill and plug the wall, as shown here. If you want the socket to be flush mounted, however, you’ll have to remove the old box and make a larger recess for a new one, which we’ll explain how to do later.
Tools & materials for the job:
- Screwdriver
- Socket tester
- Pipe and cable detector
- Hammer action drill with masonry bits
- Wire strippers
- New double socket
- Wall plugs and screws
- Green / yellow sleeving if required
Step 1
Isolate the circuit. Use a socket tester to double check that it’s dead. Unscrew the faceplate and disconnect the cables from the terminals of the single socket mounting box. Run green / yellow sleeving over the earth core if you find it bare.
Step 2
Remove the knockout in the new surface mounting box and pass the cables through. Then mark the fixing holes on the wall in pencil. Take the box away, check for hidden pipes or cables, and then drill and plug the wall behind.
Step 3
Screw the new box in place and then connect the cables to the terminals following step 3 above. Fit the new faceplate. Use the socket tester to check it’s correctly wired.
Safety first
If the cable isn’t long enough to reach the terminals of the new socket without straining, don’t be tempted to pull it. Use a specially designed crimp or terminal block to attach a new short length of cable. But only do this if there’s enough room for it inside the mounting box; all wiring connections must be accessible, not buried in the wall behind.
When flush mounting a box in a solid wall, you need to cut a neat recess through the plaster and into the masonry behind. It’s dusty work, so wear gloves and protective goggles.
Tools & materials for the job:
Step 1
Test for hidden pipes and cables and if all is clear hold the mounting box in position. Use a spirit level to check that it’s horizontal then draw its outline on the wall. Using a masonry bit and hammer action drill, make a series of holes within the outline to a slightly greater depth than that of the mounting box. Or use a socket template if you have one. Set the drill’s depth stop or wrap masking tape around the bit as a depth guide.
Step 2
Chop out the plaster and masonry with a bolster and club hammer, cutting down to the bottom of the drilled holes. Brush out all the debris and check the fit of the box.
Step 3
Hold the box in place, mark the fixing positions, and drill and plug the holes. Cut a channel for the cable before attaching the box. Then isolate the circuit and make the final connections following step 3 in ‘Replacing a damaged socket’. Fit the faceplate and check the wiring is correct using a socket tester.
When flush mounting a socket in a stud wall, it’s simplest to use a cavity fixing box. This has a flange that sits against the face of a wall and spring-loaded or rotating lugs that press against the back of the plasterboard, giving more flexibility when you’re positioning the fitting.
Tools & materials for the job:
Step 1
Decide where you want to put the new switch or socket. If you have a stud finder, use it to check that no framework will be in the way. If you don’t have a stud finder, tap the wall gently with a hammer handle, listening for the hollow note to change when you tap over the framework. Hold the box in place, use a spirit level to ensure it’s horizontal, and then draw around it in pencil.
Step 2
Check the area’s free of hidden pipes or cables, then push and twist a screwdriver through at diagonally opposite corners of the outline so that you can insert the blade of a pad saw or plasterboard saw. Cut outwards from the holes, following the box outline, and remove the waste piece of plasterboard.
Step 3
Check that the box fits snugly in the hole. Remove the knockout from the box. Push the box back into the hole, feeding the cable through the opening.
Step 4
Push in or turn the securing lugs so that they grip the rear face of the plasterboard firmly. Connect the wires and fit the faceplate. Check the socket is correctly wired using a socket tester.
A socket can become damaged for a number of reasons: a blow can break the faceplate or overheating may cause scorching. If the problem is scorching, it will usually have been caused by overloading the socket, or by loose connections in a plug. Don’t plug it back in without dealing with the problem or the same thing will happen again.
Step 1
Isolate the circuit. Use a socket tester to double check that it’s dead. Unscrew the socket faceplate and pull it away from the wall. Keep the screws in case the new ones don’t fit.
Step 2
Loosen the terminal screws and free the cable cores. If the insulation is heat damaged, cut back the cores and strip the ends. Run green / yellow sleeving over the earth core if you find it bare.
Step 3
Connect the red core or cores to the live terminal of the new faceplate, the black to the neutral terminal and the earth to the earth terminal. Tighten the terminal screws fully. Refit the new faceplate. If the new screws don’t fit the old box, use the original screws. Use the socket tester to check it’s correctly wired.
Although you can increase the number of sockets in a room by converting single sockets to doubles, there may be times where you need an extra socket where none exist already. In this case, you’ll need to add a spur from a ring circuit. You can either run this from an existing socket, or from a junction box that’s connected into the cable run of a suitable ring circuit. The circuit must have RCD protection.
The easiest way of connecting into a ring circuit is to run a spur cable from the terminals of an existing socket – but you can’t connect it to any socket. The IEE Wiring Regulations are very specific about this. You mustn’t run a spur from a socket that’s already on a spur, or that already supplies a spur. And the new socket mustn’t extend the floor area served by the circuit beyond 100 square metres.
If you’re in any doubt about whether the socket from which you plan to run is part of a ring circuit, you’ll need to consult a qualified electrician. An alternative to running a spur from an existing socket is to run it from a 3-terminal, 30-amp junction box wired into the main circuit cable. But as the same regulations apply, make sure you ask a qualified electrician if you’re in any doubt.
Step 1 - Finding the right socket
Isolate the circuit at the consumer unit and use a socket tester to double check that the power is off. Then remove the faceplate from the socket you want to run a spur from. Count the cables entering the mounting box: one cable means it’s already on a spur; three cables mean it already supplies a spur. You can’t add a spur in either instance – try another socket.
What you need to find is a socket with two cables entering it. But before you add a spur, you must first confirm that this is a ring circuit. Disconnect the black cores and – with the power still off – test them with a continuity tester. If the tester shows continuity, this is a ring circuit and you can add a spur – provided it won’t extend the floor area of the circuit beyond 100 square metres.
An alternative to running a spur from an existing socket is to run it from a 3-terminal, 30-amp junction box wired into the main circuit cable. The same regulations apply, however, so trace the cable to the nearest socket and run the above tests.
Step 2 - Consider your floor area
Although the IEE Wiring Regulations let you have an unlimited number of socket outlets on each main circuit running from your consumer unit, there are restrictions on the floor area that each circuit can supply. A 30 / 32 amp ring circuit can supply a maximum area of 100 square metres. But because ring circuits serving kitchens and utility rooms are usually the most heavily loaded, it’s best to avoid extending them into other rooms wherever possible.
You should find that the rooms of the house covered by each circuit are written inside the fuse cover of your consumer unit, but you can check this by isolating the circuit and using a socket tester on each socket to see if it works.
Once you’ve found out the extent of the circuit, you can measure the rooms it supplies and calculate the floor area. If you have a large house and were planning to run a spur through a wall to feed a socket in a different room, you may find it’ll exceed the limit. If so, you’ll need to run the spur from a different circuit.
Energy saving – no more stand-by
An intelligent multi-socket adapter has one main and several supporting sockets. When the adapter detects that the appliance plugged into the main socket has been switched off, it automatically switches off the supporting sockets too – which will save you energy. The secondary sockets switch back on as soon as you switch on the master appliance.
Begin by installing your new socket, then run a length of 2.5 mm two-core-and-earth cable from the new outlet to the existing socket.
Tools & materials for the job:
Step 1
Isolate the circuit and use a voltage tester to double check that the existing socket is dead.
Step 2
Unscrew the faceplate of the new socket, feed the cable into the mounting box through a rubber grommet and connect its cores to the faceplate terminals. Don’t forget to add green / yellow sleeving to the bare earth core of the new cable, and make sure the terminal screws are tight.
Step 3
Cut the cable and do the same at the existing socket.
Step 4
If you have metal faceplates, cut a short length of earth core from 1.5 mm² cable and run it between the earth terminals of the faceplate and mounting box.
Step 5
Put on the faceplates and turn the power back on. Finally, check your new socket is correctly wired by using a socket tester.
Begin by installing the spur socket and run a length of 2.5 mm² two-core-and-earth cable back to the point where it will be connected to the main circuit cable. The junction box should have the same amperage as the circuit.
Top tip
Make sure you’re connecting to the correct socket terminals – their position varies between brands. And do take time to read any instructions that come with your new socket.
Safety first
If you’re using metal mounting boxes, you’ll need to fit rubber grommets to protect the incoming cable from being damaged by the sharp edges around the metal cut-outs.
Step 1
Isolate the circuit and use a socket tester to double check that it’s dead.
Step 2
Unscrew the faceplate of the new socket, feed the cable into the mounting box through a rubber grommet and connect its cores to the faceplate terminals. Don’t forget to add green / yellow sleeving to the bare earth core of the new cable, and make sure the terminal screws are tight.
Step 3
If the faceplate is made of metal, cut a short length of earth core from 1.5 mm² cable and run it between the earth terminals of the faceplate and mounting box. Replace the faceplate.
Step 4
Next, screw the base of the junction box to the side of an adjacent joist, or to a batten nailed between joists. Then it’ll be within reach of the cut ends of the main cable.
Step 5
Cut the cable, stripping back the outer sheathing (but making sure it extends a few mm into the junction box). Expose the ends of the cores and connect them to the terminals of the junction box. Then connect the cores of the spur cable to the matching terminal – live to live, neutral to neutral, and earth to earth. Remember to add green / yellow sleeving to the bare earth cores.
Step 6
Make sure the terminal screws are tight, then replace the cover of the box and turn on the power. Finally, test the socket is wired correctly using a socket tester.
