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An RCD, or residual current device, is a life-saving device which is designed to prevent you from getting a fatal electric shock if you touch something live, such as a bare wire. It can also provide some protection against electrical fires. RCDs offer a level of personal protection that ordinary fuses and circuit-breakers cannot provide.

In short, an RCD protects against injury and death caused by electric shock by detecting an imbalance between the outgoing and incoming total current of a given number of circuits. It works on the very simple principle that if there is a difference in the electricity coming in against that which is going out, then it must have gone somewhere.

This phenomena is commonly known as 'earth leakage' - (or the 'Residual Current' in the RCD's title). It can be caused by a number of problems including poor electrical wiring and DIY accidents such as drilling through a cable when mounting a picture hook or cutting through a cable with the lawn mower. In this type of situation the electricity must go somewhere and choosing the easiest route can travel through the lawnmower or drill to the human holding them to create a circuit and cause electric shock.





It is  recommended that your RCD is tested at least every six months to ensure it's operating correctly. It's easy to spot the test button in your fusebox as it will have the word 'TEST' or a 'T' on it. If the RCD fails to cut the electrical supply immediately then it should be repaired as a matter of urgency.

There are many types of RCDs that protect against different things, lets take a look at some of them on the Left. 

As you can see the AC type of RCD offers the least amount of protection, this is the most commonly installed type of RCD. However, due to the way we now use electricity these types of RCD does not fully protect us, a lot of appliances use DC such as Phone Chargers, LED Lighting, Laptop Chargers, Electrical Vehicle Chargers. These appliances will blind the RCD stopped it from operating. It is important to make sure you have the correct type of RCD installed for your use. 

You won't know your RCD is faulty until that one time you need it, so lets get it checked. 


With over 18 Years experience in Design, Installation & Testing in the Domestic, Commercial and Industrial Sectors. 

Are you ready for a free Design and Quotation? 

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