Residual current devices (RCD) are very useful pieces of equipment and can prevent electrocution under certain electrical fault conditions. There are many different types of RCD and you can now get them for use on almost every piece of equipment imaginable. RCD's can be found in consumer units, RCD sockets, RCD plugs and a good variety of other electrical items which means that you can protect almost any circuit with and RCD.

RCD's are sometimes called earth leakage circuit breakers or residual current circuit breaker and are used to protect the user from electrocution, they do not provide any overload protection and so they need to be used in conjunction with a MCB (miniature circuit breaker) or a fuse. An RCD will not protect the user from a live/neutral shock!

RCD's should be used on equipment that is going to be used outdoors, such as lawnmowers etc. An RCD will trip very fast should an earth fault develop by cutting through the appliance cord, then the RCD should trip out in less than 0.04 of a second.


RCD plug

This is an RCD plug which is designed to replace a normal 3 pin domestic plug, this offers RCD protection but also accepts a fuse so that you could protect an appliance from earth leakage and from over current. These are very useful for using on outdoor equipment such as electric lawn mowers.

split way consumer unit

This split way consumer unit has an RCD at one side which offers RCD protection on the circuits on that side of the consumer unit. These consumer units are now pretty much obsolete as new consumer units now have dual RCD protection so that all circuits are RCD protected.


This is an RCBO, which is a RCD and circuit breaker combined into one unit. Although the cost of these are slightly more expensive they are a much better idea than having one RCD covering several circuits, these are designed to fit in a normal consumer unit alongside existing MCB's Most modern RCBO's are the same width as a normal miniature circuit breaker but are longer, this RCBO is double the width of a normal MCB.