If you touch something electrically live, such as a bare wire, chances are that you will receive an electrical shock that may even be fatal. An RCD or a Residual Current Device protects you from this danger, offering a level of personal protection not provided by circuit breakers and fuses. The RCD, being a sensitive safety device, automatically switches off electricity when it senses an earth fault.
Earth faults are associated with the risks of electrocution and fire. Such faults happen, for example, when you accidentally touch a faulty appliance or an exposed live wire, causing electric current to flow to earth. Outdoors, such faults may be the result of a lawn mower cutting through the supply cable.
When an RCD is protecting a circuit, it constantly monitors the electric current flowing through the different paths. The RCD switches off the circuit very quickly as soon as it detects an unusual electrical activity such as current flowing through the body of a person who has accidentally touched a live part. This reduces the risk of serious injury or death.
Using RCDs is an effective way of protecting oneself from electric shock in potentially dangerous environments such as gardens and bathrooms. To be as safe as possible, the RCD to be used must be chosen carefully from among fixed, socket-outlet and portable types.
Fixed RCDs are usually installed in commercial and industrial places at the consumer unit or fuse box. Typically, they provide protection to individual or groups of circuits. As all wiring, sockets and connected appliances on a circuit remain protected by the fixed RCD, it offers the highest level of protection.
Special socket-outlets can have RCDs built into them and you can use them in place of standard socket-outlets. This type of RCD will protect only the person who is in contact with the equipment plugged into the special socket-outlet, including the equipment’s lead.
You can plug portable RCDs into any standard socket-outlet. Just like the socket-outlet RCDs, It will protect any person who is using a device (including its lead) plugged into the portable RCD. This is a very useful device when neither the fixed nor the socket outlet RCDs are available.
Reliability of an RCD increases when tested regularly. Apart from reducing the risk of electric shock to you and your family, fixed RCDs will also defend your home against the risk of fire caused by an appliance or faulty wiring.
Although protection by using an RCD does reduce the risk of injury or death from electric shock, it does not mean that you should not be careful. Get your home wiring checked every ten years to ensure the safety of your home and your family. A registered electrician should immediately attend to any fault in the wiring or an appliance.
Be aware that if the RCD does not shut off the electricity supply even after you have held the test button for a long time, the RCD is most likely not functioning. Have it replaced or take advice from a registered electrician.