Given their vital role in protecting the occupants of your home, it is important that your RCDs are tested regularly. This will ensure that any faults, malfunctions or age wear is detected before the device is required to act. Testing also covers whether the RCD is working at an acceptable speed, cutting the power to electrical circuits within a required timeframe.
RCDs are tested by pressing the button marked ‘t’ or ‘test’. pressing this button simulates a fault, which should immediately prompt the RCD to cut the power supply to that circuit. If it does so, the RCD is working as intended. If the current remains flowing to the circuit after several seconds of pressing the test button, call a licensed electrician immediately and avoid using the devices on that circuit as much as you can.
Time-wise, fixed RCDs and socket-integrated RCDs should be tested every three months, and a portable RCD should be tested every time you use it.