RCDs Explained

What is a residual current device (RCD)?

It’s a safety device that automatically switches off the electricity if

there is a fault. It’s far more sensitive than normal fuses and circuit 

breakers. It can be a lifesaver, reacting quickly to prevent electricity
causing a fatal shock.

An RCD constantly monitors the electric current flowing along a circuit.

If it detects electricity flowing down an unintended path, such as 

through a person who has touched a live part, it will switch the circuit

off instantly, reducing the risk of death or serious injury.

RCDs can help protect you from electric shock in potentially dangerous

 areas such as bathrooms and gardens. Using electricity when you may 

be wet significantly increases the risk of electric shock. If you are wet 

and make contact with the ground, it’s easy for electricity to flow through

you. So it’s very important to have RCD protection when using electrical 

equipment in these areas. If you don’t, a job like mowing the lawn could 

turn into a deadly disaster should you cut the lead.

RCDs are available as fixed, socket or portable.

Fixed RCDs – are installed into the fusebox and can provide protection to

individual or groups of circuits. A fixed RCD provides the highest level of 

protection. It protects all sockets and connected appliances on any circuit.

Socket RCDs – these replace a standard socket. They provide protection 

to anyone plugging electrical equipment into that socket.

Portable RCDs – these plug into any standard socket. An appliance can 

then be plugged into the RCD. These are useful when fixed or socket RCDs 

are not available. But again they only provide protection to the person 

plugging electrical equipment into the socket.

Are RCDs reliable?

We’ve found that fixed RCDs are about 97% reliable. This improves if they 

are tested regularly. If you have fixed RCD protection, it will reduce the risk 

of electric shock to you and your family. It can also protect your home 

against the risk of fire caused by faulty wiring or appliances.

Remember – Although RCD protection reduces the risk of death or 

injury from electric shock it does not reduce the need to be careful. 

Have your wiring checked at least once every 10 years to ensure the 

safety of you, your family and your home. If you find a fault with your 

wiring, or an appliance, stop using it immediately and contact 

a registered electrician.

Don’t forget to test – You should test all fixed and socket RCDs about 

every three months. Manufacturers recommend that portable RCDs are 

tested every time you use them.

A good tip is to test them regularly, like when putting your clocks forward, 

or back. Especially as many electric clocks and timers have to be reset anyway.

Beware – If you hold the test button in for a long time and the RCD does 

not switch off the electricity supply, then get advice from a registered electrician.

The new UK standard for safety – Since July 2008 virtually all circuits in 

new or rewired homes have been required to include an RCD under the

 latest edition of BS 7671.

Article information obtained from ESC Site.

For further information or to have us arrange a visit to inspect 

your electrical system call: -

0800-542-0638 or Visit us at: -www.safe-electric.com