An RCD is a residual current device, a piece of safety equipment designed to help prevent fatal electric shocks or electrical fires.

What is an RCD?

Do the letters ‘RCD’ mean anything to you? Installing one of these sensitive safety devices could be the best investment you ever make, as they could save your life or the life of an employee

An RCD is a residual current device, a piece of safety equipment designed to help prevent fatal electric shocks or electrical fires.

What does it do?

An RCD automatically cuts off the electrical supply when it detects an imbalance between the live conductors. For example, if you’re using a plug-in electric hedge cutter in the garden and accidentally cut through the cord then touch the exposed wires, or if a electrical appliance develops a fault, an RCD will cut the current if it tries to earth itself through you. The unit provides protection against electrical faults and some protection against electrical fires. It won’t provide any protection against overcurrent (where a larger than intended electric current is delivered through a conductor), as for that you’ll need a circuit breaker (MCB). It’s possible to install combined RCDs and circuit breakers, and these are called RCBOs or residual-current circuit breakers with overcurrent protection.

How does it work?

An RCD works by constantly monitoring the current flowing through the live and neutral wires of the circuit it’s being used to protect. Normally, the balance of current in the two wires should be equal. If the RCD detects an abnormal flow, such as unexpected earthing through someone touching a live wire, it will automatically shut off the current very quickly before it can cause death or any serious injury.

Types of RCD

For maximum protection, we recommend installing a fixed RCD. These are installed in your consumer unit and will protect all the sockets on a circuit. This is the most efficient way of protecting multiple appliances.

Alternatively, for high-risk appliances such as lawnmowers or chainsaws, you can use a socket-outlet RCD. These are sockets with the RCD built in, but they only protect the appliance plugged into that particular socket.

Finally, there are portable RCDs available which can be plugged into any standard socket-outlet. These are ideal if you’re travelling between locations with power tools and need to make sure you’re protected at any site. There’s always a chance of forgetting to plug it in, though, so for domestic use, it’s best to use a more permanent solution.

Stay safe with RCDs

Once you’ve chosen a type of RCD and had it installed, don’t forget that fixed and socket RCDs should be tested every three months for maximum safety. Since July 2008, almost all circuits in new or rewired homes must include an RCD under current regulations, so you may already have fixed RCD protection. To check, go to your consumer unit and check for a push button marked ‘Test’. The presence of this button means you have a fixed RCD which must be tested every quarter.

Here at KDE, we’re approved by NICEIC, the regulatory body for the electrical contracting industry. Using an approved contractor is the best way to ensure a safe job, so if you’d like to discuss installing or testing an RCD to protect your home or workplace, give us a call now on 01928 711444 for a chat about how we can help.

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