Example of a

 switchboard

 mounted  RCD

Residual Current Devices 

Residual current devices (RCDs) also known as Safety Switches, are probably the best means we have for preventing fatality or injury from electric shock. They are installed in the switch boards of new buildings and are being installed in many older premises as well.

A word of Caution:

Good as they are, RCDs should not be relied on as the total answer to electrical safety. We do find faulty ones. They simply provide one level of safety to compliment the other strategies of an effective safety policy.

How RCDs Work

In simple terms, the RCD monitors the outgoing current of a circuit and compares it to the incoming current. If all is normally, these two currents will be the same. However, if some of the outgoing current is leaking away to earth, (flowing through a person for example) the outgoing current will be greater than the incoming. The RCD detects this imbalance and "trips off", disconnecting the supply.

Because they detect the balance between the two currents, they can be made very sensitive and fast acting enough to switch off the current before it has had time to cause harm.  

Portable RCD

Portable RCDs

As well as the fixed wired RCDs that are mounted in switchboards, portable RCDs are also available. These should be used whenever there is a possibility that the building outlets are not RCD protected. 

We recommend their use even when plugging into an RCD protected outlet for two reasons. 

First, your portable RCD can be more sensitive and trip faster than the switch board one, giving you an extra margin of safety. ( Due to the collective effect of the earth leakages in building wiring and the electrical equipment plugged into it, building RCDs may have to be less sensitive to avoid "nuisance tripping".)

Secondly, RCDs use a mechanical switch to disconnect the supply when they trip. These switches can stick and not switch off. That is why they must be tested periodically to make sure they are still working freely. You may not normally be able to test the switchboard RCD because you would switch off everyone else on that circuit. But you can test your portable RCD whenever you want.

We can supply portable RCDs

Comprehensive Safety Services has a range of portable RCDs, from small units suitable for home and office use to more robust industrial models. Our price includes testing and tagging, so you receive them ready to use. Please email us with your requirements.

We can arrange installation of switchboard RCDs

Comprehensive Safety Services can supply competitively priced switchgear including RCDs and surge arrestors, for upgrading your existing switchboard. We work with reputable electrical contractors to arrange installation. Please email us if you would like more information or a quote.