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What is an RCD?

What is an RCD?

RCD short for residual current device, simply saves lives. It is designed to prevent you from getting a fatal electric shock if you touch something live, such as a bare wire. Due to its efficiency it is a form of fire protection. It offers a different form of protection to miniature circuit breakers and fuses.

What does an RCD do?

An RCD is a safety device which is very responsive and detects any faults within the electrical system, and if a fault is present the RCD will cut off the electricity supply.

An RCD has the main purpose of protecting anyone from the risks of electrocution and fire from earth faults.

For example, if you wanted to hang up a painting on the wall and accidentally drill through a live cable the RCD would 'trip' disconnection the circuit.

How does it work?

An RCD works by monitoring the electric current flowing through the circuits it is protecting. If the electricity flows down an unusual route the RCD will detect this and cut off all electricity. For example if someone touched a live part, the RCD will automatically disconnect the power supply, significantly reducing any serious injuries.


To check if you have fixed RCD protection, go to your consumer unit and have a look to see if there is a device with a pushbutton marked ‘T’ or ‘Test’. This ‘test’ button is part of an RCD. If an RCD is fitted, there should also be a label on or near the consumer unit stating ‘test quarterly’.

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