RCDs - Residual Current DevicesWhat is a Residual Current Device? What types of RCDs are available?
What is a RCD, and what types of RCDs are there? First of all, a Residual Current Device (RCD) is a safety device that switches off electricity automatically if there is a fault. The RCDs are far more sensitive than normal fuses and circuit-breakers and they provide additional protection against electric shock.
Additional protection by means of an RCD can be a life-saver. An RCD constantly monitors the electric current flowing along a circuit. If it detects electricity flowing down an unintended path, such as through a person who has touched a live part, it will switch the circuit off very quickly, thereby significantly reducing the risk of death or serious injury. Using electricity while the person is wet significantly increases the risk of electric shock. If you are wet and in contact with the ground, it makes it easier for the electricity to flow through you. The RCDs can help protect you from electric shock in areas such as in bathrooms and gardens (where you may be wet).
It is very important to have RCD protection when you are using any electrical equipment outdoors. Without the RCD protection, a simple job like mowing the lawn could turn into a deadly disaster if you accidentally cut through the electrical lead.
Please watch the video below which is a real life example of how an RCD could save your life:
RCD Residual Current Device Types
There are three main types of RCD:
- Fixed RCDs
- Socket-outlets RCDs
- Portable RCDs
Fixed RCDs These are installed in the consumer unit (fuse box) and protect all of the socket outlets on the circuit thus providing the greatest level of protection.
There are two main types of fixed RCD's namely RCBOs and RCCBs. The differences are as follows:
RCBO - Residual Current Operated Circuit-Breaker with Integral Overcurrent Protection
This is a mechanical switching device designed to make, carry and break currents under normal service conditions and to cause the opening of the contacts when the residual current attains a given value under specified conditions. In addition it is designed to give protection against overloads and/or short circuits and can be used independently of any other overcurrent protective device within its rated short circuit capacity.
RCCB - Residual Current Operated Circuit-Breaker without Integral Overcurrent Protection
This is a mechanical switching device designed to make, carry and break currents under normal service conditions and to cause the opening of the contacts when the residual current attains a given value under specified conditions. It is not designed to give protection against overloads and/or short circuits and must always be used in conjunction with an overcurrent protective device such as a fuse or circuit-breaker.
Socket-outlet RCDs the Socket Residual Current Devices are built into a special socket-outlet which replaces a standard socket-outlet. This type of RCD provides protection only to the person in contact with the equipment, including the leads, plugged into the special socket-outlet.
The Portable Residual Current Devices plug into any standard
socket-outlet. An appliance can then be plugged into the RCD. These are
useful when neither fixed nor socket-outlet RCDs are available, but
remember: they provide protection only to the person in contact with the
equipment, including the leads, plugged into the portable RCD.
The Reliability of the RCDs
The official research found out that the fixed RCDs are about 97% reliable and that this rate is improved if they were regularly tested by users. If you have fixed RCD protection, you can rely on it to not only reduce the risk of electric shock to you and your family, but also to reduce the risk of damage being caused to your property by fire caused by faulty wiring or appliances.
Important: Although the Residual Current Device protection reduces the risk of death or injury from electric shock, it does not reduce the need to protect yourself, your family and your property by having your electrical wiring checked at least every 10 years. If you think there is a fault with your wiring or an appliance, stop using it immediately and contact us.
Testing the Residual Current Devices testing the RCDs
It is strongly recommended that you test all the fixed and the socket-outlet RCDs regularly (once every three months) by using the test' button built into them. The manufacturers recommend that portable RCDs are tested every time you use them.
Do not hold the test button in for a long time if the RCD does not trip. If the RCD does not switch off the supply when you use the test button, then contact us.
The UK standard for the safety of electrical installations
In July 2008 a new edition of the UK standard for the safety of electrical installations, BS 7671: 2008, came into effect. This standard now calls for virtually all circuits in new or rewired homes to be provided with additional protection by means of an RCD.
For further information and advice please contact XS Engineering.
XS Engineering Leading electrical engineers and expert electricians serving Paphos Cyprus