What is an RCD and why are they so important?

When you first make enquiries about electric vehicle charging points, you may be asked a few questions in relation to your electrical supply, one of which may be whether your consumer unit (fuseboard) is covered by an RCD.

An RCD (Residual Current Device) is a potentially life-saving device, designed to prevent fatal electric shocks caused by touching something live, such as a bare wire. These clever devices can also provide some protection against electrical fires, thus offering a level of personal protection against earth faults that ordinary fuses and circuit-breakers cannot provide.

Domestic consumer unit

What does an RCD do?

An RCD is a safety device that switches off electricity automatically if there is a fault.  For example, if you are mowing the lawn and accidentally cut through the cable, the RCD will switch the circuit off very quickly, significantly reducing the risk of death or serious injury.

How does it work?

An RCD’s job is to constantly monitor the electric current flowing through one or more circuits and if it detects electricity flowing down an unintended path, such as through a person who has touched a live part, it will switch off the circuit almost immediately.

How do I check whether I already have fixed RCD protection?

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 push button 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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