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Home/Know your materials/Electric socket outlets and mounting boxes

Electric socket outlets and mounting boxes

An electric socket outlet consists of a mounting box into which the cable is fed and a faceplate with terminals to which the cable cores are connected. The faceplate will usually have either one, two or three power outlets and will be referred to as a one, two or three gang socket.  The holes in the faceplate for the plug pins are shuttered to make them childproof. Socket outlets can be either flush or surface-mounted to the wall, although surface mounted sockets are more vulnerable to being cracked following an impact, so it is worth considering replace these with flush-mounted sockets. If a socket is damaged do not use it until it has been repaired. Scorch marks on the faceplate or around the pin holes indicate poor connections.

Plastic socket outlets

The most common type of socket outlet is made of plastic and will be a one, two or three-gang socket. Plastic sockets fit onto a surface-mounted plastic box or onto a flush-mounted metal box.

Metal socket outlets

Metal sockets add a touch of style to the room and are available either with a single or double outlet. They can be made from brass, chrome or stainless steel. The shuttered pin holes and switches have plastic surrounds. If flush-mounting a metal outlet you need to use a steel mounting box. But a surface mounted metal outlet needs to be fitted onto a mounting box made of the same metal.

Sockets with indicators

Socket faceplates made from plastic and metal are available with small neon indicator lights that light up when the power outlet is switched on. When fitting this type of socket it is important to take care as it is easy to dislodge the small bulb behind the coloured window.

Fused connection unit or FCU

For connecting high-wattage appliances, such as cookers, extractor fans, central heating timers and heaters to a circuit you will need to fit a fused connection unit or FCU. An FCU is fitted with an integral fuse. The flex from the fixed appliance is connected directly into the FCU instead of being plugged into a socket. The FCU may be fitted with a switch and a small neon indicator light.

Flex-outlet plates

Electric sockets must never be fitted in a bathroom, so if you need to connect a fixed appliance such as a towel rail, it needs to be connected to a flex-outlet plate. The cable will run from the FCU outside of the bathroom into the back of the flex-outlet plate's mounting box. The towel rail's flex is fed through the front of the faceplate and connected to terminals on its back. Flex-outlet plates do not have switches.

Outdoor sockets

Outdoor sockets are made from waterproof polycarbonate and are fitted with a cover that closes even when the plug has been pushed into the socket. The high impact polycarbonate is resistant to oil, alkaline and ultra violet. Outdoor power outlets usually have one or two sockets. Always look for an outdoor socket with an IP66 rating as this indicates it conforms to the standard set by the International Electrochemical Commission and offers protection against dust and jets of high-pressure water entering the unit. Outdoor sockets must be fitted with a high sensitivity residual current device (RCD).

Flush mounting boxes

Metal mounting boxes for fitting power outlets flush to the wall can have one, two or three-gangs. Pre-cut discs at the back of the box are pushed out and a grommet is inserted into the resulting opening to protect the cable which is then fed through. There will be an earth terminal in the back of the mounting box and this must be connected to the earth terminal on the faceplate with a flying earth. Plastic mounting boxes with single and double sockets are available for plasterboard walls. These also have cable entry points in the back which need to be knocked out. But grommets do not need to be inserted into the openings.

Surface mounting boxes

Generally surface mounting boxes for interior use will be made of plastic. Once again they can have one, two or three power outlets and need to have the cable entry points knocked-out in the back of the box. It is not necessary to fit grommets into the openings.

Pattress

A pattress is a plastic mounting frame that can be fitted over a single flush mounted metal box to convert it into a surface mounted double or triple socket outlet.

Blanking plate

A white plastic plate that screws over any spare single socket to blank it off.

Master socket

White and square, this is the main phone connection socket that has to be installed by the telephone company.

Extension socket

A socket connected to the master socket and located where the new phone is to be installed.

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