Testing RCDs

Information on testing RCDs

To ensure that the RCDs fitted to your property perform correctly, they must be tested at regular intervals. Building and Energy recommends that each RCD be tested every three months.

To test your RCD press the ‘test’ button on the front of the device quickly and then release it. The button will only test the RCD if an electricity supply is connected.

Pressing the test button will simulate an earth leakage fault and indicates whether the device is operating correctly. When an RCD operates all power is lost to the equipment, power point or circuit protected by the RCD. To restore power simply move the “on/off” switch back to the “on” position. Electrical clocks and timing devices may have to be reset.

If the RCD fails to operate, a licensed electrical contractor must be engaged to test the RCD and replace it if necessary.

Simple steps for testing your RCD

Follow these simple steps to ensure your RCDs are operating correctly:

  1. Plug a small lamp into a power point and make sure it works. Leave it turned on.
  2. Make sure that electricity is connected to the property and the main switch is in the "on" position. The lamp should be on.
  3. Turn off all electronic equipment (computers and televisions) etc.
  4. Push the test button on each RCD. Do not hold your finger on the test button. The RCD should operate (turn off). If it does not operate, it must be checked by an electrical contractor.
  5. After pushing the test button and the RCDs have turned off, check that the small lamp is now off. Also check that all the lights and power points do not operate. To do this, plug the small lamp into all the power points and turn the power point on. If the lamp turns on, a licensed electrical contractor must be engaged to correct the wiring.
  6. When finished testing, turn the RCDs back on and check that the lamp works when plugged into a power point. 

Nuisance tripping

Some electrical appliances and old wiring may have a normal small amount of earth leakage current which can trip an RCD.

Earth leakage increases with each additional electrical appliance plugged in, so a single meter box RCD protecting all household wiring is more likely to experience nuisance tripping.

If an RCD trips twice for no apparent reason, have your wiring and appliances tested by a licensed electrical contractor.

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