The importance of RCD’s

An RCD, or residual current device, is a life-saving device now embraced throughout the world. They act as a primary source which prevents a fire or electrocution. RCD’s offer a level of personal protection that ordinary fuses and circuit-breakers cannot provide.

RCD Board

According to Powerbreaker it takes less than one quarter of an amp leaking from a faulty installation to generate sufficient heat to start a fire, or if leaking through a human body for only 200 milliseconds can cause heart fibrillation and subsequent death. The scary thought is many people still don’t have RCD boards installed in their homes.


How an RCD works


An RCD protects by constantly monitoring the current flowing in the live and neutral wires supplying a circuit or an individual item of equipment. Under normal circumstances, the current flowing in the two wires is equal. When an earth leakage occurs due to a fault in the circuit or an accident with the equipment, an imbalance occurs and this is detected by the RCD, which automatically cuts off the power before injury or damage can result.


The Electrical Safety Council state that every year in the UK around 70 people die and 350,000 are injured as a result of electrical accidents at home.  A Government report also indicated that, each year, about 4,000 fires caused by electricity in homes might have been prevented if RCD protection had been fitted in the consumer unit.  Despite this, more than half of UK homes – that’s 13 million – don’t yet have any, or an adequate level of such additional protection.


Here’s the different types of RCD’s available:


Fixed RCDs

Fixed RCD Board

These are installed in the consumer unit (fusebox) and can provide protection to individual or groups of circuits. A fixed RCD provides the highest level of protection as it protects all the wiring and the sockets on a circuit, and any connected appliances.


Socket-Outlet RCDs


Socket RCD


These are special socket-outlets with an RCD built into them which can be used in place of a standard socket-outlet. This type of RCD provides protection only to the person in contact with equipment, including its lead, plugged into the special socket-outlet.


Portable RCDs

Portable RCD

These plug into any standard socket-outlet. An appliance can then be plugged into the RCD. They are useful when neither fixed nor socket-outlet RCDs are available but, as with socket-outlet RCDs, they provide protection only to the person in contact with the equipment, including its lead, plugged into the portable RCD.


How do I check whether I already have fixed RCD protection?


To check if you have fixed RCD protection, go to your consumer unit and have a look to see if there is a device with a pushbutton marked ‘T’ or ‘Test’. This ‘test’ button is part of an RCD. If an RCD is fitted, there should also be a label on or near the consumer unit stating ‘test quarterly’.

If you have an RCD, you should check that it is functioning properly by pushing the test button every three months. When tested, the RCD should switch off the power to the areas of the home it protects.

The RCD (or RCDs) in your consumer unit may not cover everything in your home, such as the lighting circuits, so it’s a good idea to check (while the RCD is off) which sockets and lights are no longer working, showing that they are protected by that RCD.

Switch the RCD back on to restore the supply.


If your RCD does not switch off the electricity supply to the protected circuits when the test button is pressed, or if it does not reset, get advice from a registered electrician.

If you don’t have RCD protection fitted in your consumer unit, the best way to protect yourself in the short term is by using a portable RCD, which you can find in most DIY or gardening stores.  All you have to do is plug it into a socket and plug the appliance into the RCD. The appliance will then be safer to use.

However if, for example, you damage a hidden cable when fixing something to a wall, you won’t be protected against electric shock unless you have an RCD in your consumer unit protecting that circuit.



If you believe your home may not be fitted with an RCD or require it testing then please do get in touch with Select 1, we will be more than happy to help guide you through your installation. Call us on 0800 118 2568 or email us at:


Source:  Electrical Safety Council




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