Do I Need an RCD?

RCDs protect humans against electrocution in a way that fuses and circuit breakers do not. For more information about the differences and applications, read our guide.


If you have a new circuit installed, or a circuit is substantially modified, you may be required to have an RCD fitted under the Building Regulations (Part P) or BS7671 wiring regulations. This is a legal requirement.


In domestic properties, situations requiring mandatory RCD protection include:

  • Properties supplied by a TT earthing arrangement (one with a local earth terminal, as opposed to an earth being provided by the distributor). This typically includes rural locations fed by overhead cables. In this case, a 100mA RCD should be used for all circuits other than those below, which require a 30mA RCD.
  • Socket outlets for general use, where a device can be routinely plugged in or disconnected.
  • Any location with a bath or shower.
  • Circuits supplying equipment for use outdoors - for example, outside sockets, or sockets in a garage used to supply a jetwasher or lawnmower.
  • Cables installed in walls or partitions where the installation depth is less than 50mm, or where the wall contains metal parts other than nails/screws.


RCDs can be fitted to specific circuits, such as power showers, if you have an older fuseboard which does not support RCDs. Alternatively, you may consider replacing a fuseboard with a more modern consumer unit which incorporates full RCD protection.


This is not an exhaustive list. If you are unsure, contact us for expert advice.

Any questions?

Devonia Electrical
13 Shute Park
Malborough, Devon TQ7 3SU


Tel: 01548 561561

Mobile: 07970 062008



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