Summary: Wiring an outdoor socket: Learn how to wire an outdoor socket, run a spur from a socket outlet and fit the outdoor socket.
Installation must conform to Building Regulations.
To avoid running outdoor appliances from indoor sockets, you can run a spur from an indoor circuit to a weatherproof outdoor socket. If possible, drill through the back of an existing socket so that the new socket is backing on to it on the outside wall. Otherwise, run a cable from the interior socket along the wall or skirting board to the desired position.
Running a spur from a socket outlet
Using a continuity tester, check that the socket you have chosen to run the spur from is not itself supplied by a spur or supplying another spur.
- Cut off the mains power at the consumer unit.
- Remove the face-plate and mounting box of the interior socket.
- Using a power drill with a hammer action fitted with a 10mm (2/5in) masonry bit which is at least 300mm (12in) long, drill a hole through the wall. With the power switched off you will need a cordless drill.
- Fit the mounting box back in position and feed a length of 1mm2 three core cable through the back of the mounting box and through the hole in the wall.
- If the earth core is bare, slide some green-and-yellow insulating sheath over the end.
- Connect all the cores to the face-plate: the live cores (red) to the L terminal; the neutral cores (black) to the N terminal; and the earth cores (yellow-and-green) to the E terminal. There should be three cores of the same colour in each terminal.
- Ensure a flying earth is connected to both the earth terminal on the socket plate and the earth terminal in the mounting box.
- Screw the face-plate to the mounting box.
Fitting the outdoor socket
Use a weatherproof outdoor socket with a cable entry hole in the back and a high-sensitivity 30 milliamp RCD (residual current device).
- Ideally the cable from the interior socket should feed directly into the back of the exterior mounting box. If this is not the case any exposed cable running from the hole to the exterior mounting box, must be protected by a conduit.
- Press out one of the tabs in the back of the mounting box and insert a grommet into the hole, which will make a watertight seal with the cable. Drill out any drainage holes in the bottom of the mounting box to reduce condensation.
- Feed the cable into the mounting box and mark the position of the screw holes on the wall.
- Drill and plug the holes.
- Screw the mounting box to the wall.
- Prepare the cable and insulate any bare earth core with green-and-yellow sheath.
- Connect the cores to the socket face-plate: the live core (red) to the L terminal; the neutral core (black) to the N terminal; and the earth core (yellow-and-green) to the E terminal.
- If you have a metal mounting box, ensure that it is earthed: an earth core should be connected to both the earth terminal on the socket plate and the flying earth terminal on the mounting box. There is no need to earth a plastic exterior mounting box.
- Screw the face-plate to the mounting box.
- You should test the RCD before you use the socket each time by plugging in an appliance, switching it on, and pressing the test button. If the RCD cuts off the power, press reset on the socket and continue using the socket. If the circuit is not tripped, call an electrician to fix the fault.
Tools Needed
- Insulated screwdriver
- Wire cutters/strippers
- Trimming knife
- Continuity tester
- Power drill
- Masonry bit
Materials needed
- Weatherproof outdoor socket
- PCV conduit
- Yellow-and-green sheathing
- Screws
- Wall plugs
Important note:
The colour-coding system for electric cable changed in 2006, make sure you read Electric cable and flex to view the new information.
Fitting the outdoor socket video
Video showing you how to install an outdoor socket on your exterior wall.