top of page

An electricians guide to different consumer units.

To understand what an RCD (Residual-current device) does we must first understand what an electrical safety switch is. An electrical safety switch is a device that will cut off or divert the flow of electricity. An RCD prevents current from flowing when there is more current passing through the live than the neutral. Energy cannot just ‘disappear’. If there is more flowing in than out, it must be going somewhere other than the neutral. An RCD will trip in this scenario in order to prevent a fire risk or electric shock. This is known as additional protection and all circuits in a domestic setting must now be installed with this safety device as of BS 7671:2008.

RCBO with surge protection
Dual RCD consumer unit

The problem with RCD's is that the device cannot protect against overload or short circuit faults like a fuse or a miniature circuit breaker (MCB) does.

Dual RCD consumer units have 2 RCDs each of which will protect several circuits which are also protected by one MCB per circuit. Whereas an RCBO (Residual Current Breaker with Overload protection) is a combination of an MCB and an RCD within the same device.  RCBO boards are slightly more expensive, however offer numerous advantages:

1. RCBO consumer unit are a smaller and more compact arrangement which may be necessary when there is limited space available to install. 

2. If there is ever a fault with the wiring which needs fixing it will make it easier, quicker and therefore cheaper for an electrician to find and repair.

3. If an RCD detects a fault it will trip, cutting the power to every circuit it is protecting. An RCBO will only cut the power to the one circuit it is protecting rather than half of the circuits protected in a Dual RCD consumer unit.

4. As BS 7671 (the wiring regulations) is constantly evolving there has been talk of making RCBO consumer units a mandatory requirement.

To discuss prices for a replacement consumer unit please contact Tom at Payne Electrical Services on 07762710540 online at or via email at 

Once you have decided on a consumer unit it is also highly recommended to consider having a surge suppressor installed. A surge suppressor or surge protection device SPD is designed to protect the electrical devices used by the installation from voltage spikes. Please look at our guide which offers a detailed explanation on the benefits of having an SPD installed.


If you are in Manchester, Salford, Sale, Stockport, Wigan, Altrincham, Bolton, Tameside, Worsley, Didsbury, Oldham, Rochdale and Cheshire Payne Electrical Contractors are the right choice. Don't just take our word for it read some of customer reviews to find out why.

bottom of page