Extra sockets, alarms and fans

Plenty of houses round here were built between the 1950s and the 1980s, when a room needed far fewer sockets than it does now. An extra double socket is normally added to an existing circuit, by extending it or with a spur, once the circuit has been tested and can take the extra load.

New sockets need 30 mA RCD protection. If the circuit you are adding to has none, the quote sets out the options, from an RCD at the socket itself to a new consumer unit.

Switches move too: a light switch to the right side of a door after a wall comes down, two-way switching for a landing, a dimmer that works properly with LED lamps.

USB sockets fit in place of an ordinary double socket, sometimes with a deeper back box. Buy them from a known maker: the charger inside is a small power supply, and quality varies.

An outdoor socket for the mower, the pressure washer or a garden light needs to be weatherproof, with a cover that keeps the rain out, and RCD protected. If it is fed by a new circuit rather than an extension of one indoors, it is notifiable under Part P.

A new kitchen, an extension or a knocked-through room moves the furniture, and the sockets need to follow. Cables buried in walls have to run in the safe zones, straight up, down or across from an accessory, so that someone drilling later can predict where they are, or be protected in another way, and those circuits need RCD protection.

It is far easier before the walls are plastered and decorated. If the plasterer is booked, get the wiring done first.

An electric cooker, oven or induction hob is a big load, and normally has a radial circuit of its own from the consumer unit, with a cooker switch nearby so it can be turned off without reaching behind it. Changing from gas to an induction hob usually means a new circuit, sized for the hob’s rating.

A new circuit is notifiable under Part P and gets an Electrical Installation Certificate. Swapping an oven like for like on an existing circuit is not, but the connection still has to suit the appliance.

Mains-powered, interlinked alarms are the norm in new work. Each alarm runs from the mains with a battery as backup, and they are joined, by a cable or by radio, so that when one goes off they all go off. A fire in the kitchen sets off the alarm on the landing too.

Where they go:

• A heat alarm in the kitchen. A smoke alarm there would go off every time the toast burns. A heat alarm responds to the temperature instead.
• A smoke alarm on the circulation route on each floor: the hall downstairs and the landing upstairs.

Every alarm has a replace-by date printed on it. Press the test button on each one as often as its instructions say: if one sounds, they should all sound.

A bathroom fan clears the steam before it turns into mould; a kitchen fan or cooker hood does the same for cooking. Bathroom fans usually run from the lighting circuit, coming on with the light and running on with a timer, or switching on by themselves when the humidity rises.

In a bathroom, the zones decide what can go where. Zone 0 is inside the bath or shower tray. Zone 1 is above it, up to 2.25 metres from the floor. Zone 2 extends 0.6 metres out from zone 1. A fan in zone 1 or 2 must be rated at least IPX4, and its isolator goes outside the zones, often just outside the door. Work in a bathroom’s special location is notifiable under Part P.

The duct has to run to the outside. A fan that blows into the loft just moves the damp somewhere else.

A small addition or alteration to an existing circuit, such as an extra socket, a moved switch or a fan on the lighting circuit, gets a Minor Electrical Installation Works Certificate: one page recording what was done and the test results for that circuit.

Anything that needs a new circuit, such as a cooker or hob supply, an outdoor circuit or a circuit for the alarms, gets an Electrical Installation Certificate and is notifiable under Part P. Work in a bathroom’s special location is notifiable too, even when it only needs a Minor Works certificate. The notification is made for you, and you receive a Building Regulations compliance certificate.