It is a fairly simple job to convert a single 13A socket outlet to a double.
Materials required: One 13A double socket outlet. One plastic two-gang surface mounting box. A short length of green/ yellow PVC sleeving.
Surface to surface conversion
Turn off the main switch. Release the existing single socket from its box and disconnect the six wires (two red, two black and two earth wires) from the socket terminals. Remove the box from the wall.
Knock out the section of thin plastic from
the base of the new box. Thread in the cables and hold the box in position against the wall and mark the screw fixing holes. Drill and plug the holes for gauge 8 wood screws. Fix the box to the wall.
If the earth wires are not sleeved, slip a length of the green/yellow sleeving over the wires and connect them to the E terminal of the new socket outlet. Connect the red wires to the L terminal, and the black wires to the N terminal of the socket outlet. Fix the socket outlet to the box using the two screws supplied.
Flush to surface conversion
Remove the existing single-gang socket outlet from its flush box.
Knock out the section of thin plastic from the base of the new two-gang plastic box. Thread in the cables and fix the box to two of the screwed lugs of the metal flush box using the existing original screws removed with the single socket outlet. Connect the cables to the respective terminals of the new socket outlet after fitting sleeving to the earth wires if not already sleeved.
Fix the socket outlet to the box using the two screws supplied with the socket.
Identifying spur cables
A spur cable may only feed one double or one single socket outlet, so it is important to check that the single outlet you are converting is the only one on a spur. If it contains only one cable, examine the nearest socket outlet each side of it. One of these should have three cables and the other two or three (this may be feeding another spur). If neither has three cables, your chosen outlet is second on a spur and may not be converted. To check if a socket outlet having two cables is in a ring circuit, again examine the adjacent outlets. If one has three cables and the other has one, the outlet is the first of two on a spur, but if both adjacent outlets have two cables, it is part of a ring circuit and may be safely converted to a double.
Adding a socket
The simplest method of providing an additional 13A socket outlet is to supply it from a spur cable connected either to the terminals of an existing socket outlet on the ring circuit or to connect it to a 30A joint box in the ring cable. Both methods involve a minimum of disturbance to existing wiring.
Materials required: A quantity of 2.5mm2 twin and earth PVC sheathed cable, green/ yellow PVC sleeving, one double or single 13A socket outlet together with a surface or a flush mounting box; a PVC grommet for a flush box; a 30A three-terminal plastic joint box if the new cable is connected to the ring cable (not at a socket), cable clips, wood screws and wall plugs.
Turn off the main switch and release the nearest socket outlet from its box to check it has two cables. Raise a floorboard at this position and another near the new socket position and any other floorboards needed to be raised along the cable route. Ease out the plaster behind the skirting at the existing socket position and pass the cable up from the void and into the mounting box.
Prepare the end of the cable by stripping off the sheathing leaving about 12mm in the box. Connect the wires to the socket terminals: red alongside the existing red wires in the L terminal, the black wire alongside the existing black wires in the N terminal and the sleeved earth wire in the E terminal. Refix the socket to its box.
If the joint box method is used instead, insert the joint box, in the void, into one of the cables going up into the socket, having removed the section of sheathing. Connect these wires and the wires of the new cable to the three terminals in the 30A joint box.
Return to the new socket position and ease out the plaster behind the skirting board. Pass the end of the new cable up behind the skirting board. Knock out a section of thin plastic on the edge of the box if a surface type. If a flush box, knock out a blank on the bottom edge and fix a grommet in the hole.
Fix the box to the wall. If a flush box, first chop out a chase in the wall so that the front edge of the box is flush with the wall.
Thread in the end of the cable. Prepare the end of the cable by stripping off the sheathing in the box but leave about 12mm within the box. Strip about 9mm of insulation from the ends of the insulated wires and slip green/yellow PVC sleeving over the bare end of the earth wire.
Connect the red wire to the L terminal, the black wire to the N terminal and the sleeved earth wire to the E terminal. Fix the socket to the box using the two screws supplied with the socket.