Residual Current Devices
A residual current device (RCD) is an electrical safety device that turns off the electricity supply automatically if there is a fault in either your wiring or something you plug in and use. RCD’s are far more sensitive than normal fuses and circuit-breakers and so provide you with much needed extra protection against an electric shock.
Having an RCD can save your life. An RCD constantly monitors the electric current flowing around your system. If it detects electricity flowing down an unintended path, such as into a person who has touched something live, it will switch the circuit off very quickly as they usually operate within 25-30 milliseconds, thereby significantly reducing the risk of death or serious injury. Circuit breakers and wire fuses can take significantly longer to turn off the power, as they are primarily designed to protect the wiring, and this can prove fatal if a person was getting an electric shock. If your home has one or more RCD’s, then you must test them regularly.
Testing the button every three months is important. The device should switch off the electricity to a number of circuits; you should then switch it back on to restore the electricity. Do not hold the test button for a long period if the RCD does not trip. If it doesn’t switch off the electricity when you press the button, contact a registered electrician. To test, just follow the instruction label, which you should find near to the RCD. It should read as follows:
“This installation, or part of it, is protected by a device which automatically switches off the supply if an earth fault develops. Test every three months by pressing the button marked ‘T’ or ‘Test’.” More on RCD’s