A residual current device (RCD) is a device that could quite literally save your life. Its basic function is to prevent fatal electric shocks by shutting off an electric circuit automatically when it detects a fault, so even if you touch a live wire, it should kick in and save you.

Also offering protection against electrical fires, it’s a standard that provides an extra level of protection above traditional fuses and circuit-breakers.

An RCD is designed to limit the dangers caused by earth faults in any capacity, whether that’s a cable you cut through when owning the lawn or an overheated appliance.

How does it work?

It works by monitoring the electricity running through a circuit. If it detects that electricity running somewhere it’s not supposed to go, then the RCD is engaged and the circuit is switched off instantly, limiting the risk of serious injury.

Types of RCD

All RCDs are used to prevent electric shock, first and foremost, but there are various types of RCD to examine, each of which operates in a slightly different way.

Fixed – Installed in a fusebox, these provide the highest possible level of protection, as all wiring and sockets are covered.

Socket-outlet – This refers to sockets with an RCD built-in and will provide protection only to the person in direct contact with it.

Portable – These RCDs can be plugged into any standard outlet and are, as the name suggests, a portable option that functions in very much the same way as a socket-outlet RCD.

What situations might require an RCD?

There are a number of domestic situations where RCD protection might be required. In any location where there is water present (baths and electric showers), for example, or in any circuits that supply electricity for outdoor use, including garages.

In locations fed by overhead cables, where power lines are often in danger of weather damage, a 100mA RCD should always be used.

RCD reliability

The official figures on RCD reliability are 97% but as long as they are regularly tested then RCDs should be incredibly reliable, particularly if you have a fixed RCD installed on your fuse box. They should be tested on average once every few months, though portable RCDs should be tested every time they’re used.

Do I have fixed RCD protection already?

Since 2008, all circuits installed in new homes or required homes have been required to include an RCD, so if your home is less than a decade old, or you had your home rewired in the last ten years, you probably have a fixed RCD on your fuse box.

To check for yourself, simply examine your fuse box and look for a button marked “Test,” if you see it then you have fixed RCD protection. However, if this is not the case then it might be something you want to look into, as it’s something that could quite literally save your life and can cost a little as a tenner for a portable RCD.

We would always recommend, however, hiring a professional electrical engineer to install a fixed solution. Granted, a fixed RCD will set you back more, but can you really put a price on your family’s safety?