RCDs, Smoke Alarms and Electrical Safety - Compliance Alert Reminder

How to test your RCDs

Residual current devices (RCDs) are an essential safety feature in any home. It is the seller’s responsibility to ensure that a home has at least two compliant RCDs installed before sale. But as a buyer, you need to understand why RCDs are so important, and how to make sure they remain fully functional after you take possession of your new home.

What is an RCD?

An RCD monitors the flow of electricity (current) from the main switchboard. If it detects any imbalance in the current, it cuts off the electricity supply to all the power and lighting circuits it regulates.

Why are RCDs so important?

RCDs are a potentially life-saving device, designed to protect against electric shock, electrocution, and electrical fires. Fuses and circuit breakers perform a similar function, but RCDs provide far superior protection.

When you touch a live wire, electric current flows through your body. The RCD immediately detects that change in current and instantly shuts off the electricity. You may end up with a minor burn – as opposed to possible death had the RCD not been triggered.

Why do homes need to have two RCDs?

The main reason for having more than one RCD is that if one operates, the home will still have light and power to the areas protected by the other RCD. Some home owners choose to have more than two RCDs fitted, so that even fewer circuits are affected when any given RCD operates.

Having multiple RCDs also reduces the risk of faulty operation. Some electrical appliances and wiring may have a small amount of earth leakage current which, while not a safety risk, can trip an RCD. If a home has more RCDs, each will protect fewer appliances. This means less overall earth leakage per RCD, and therefore less chance of the RCD being ‘tripped’ by this low-level leakage.

How and when should I test my RCDs?

The current EnergySafety recommendation is to test your RCDs every three months.

  1. Turn the main switch to the ‘on’ position.
  2. Plug in a lamp and turn it on. Turn all other appliances off.
  3. Push the ‘test’ button on the RCD to simulate an earth leakage fault. Push quickly then release; don’t hold the button down.
  4. When the RCD operates, it will cut off power to all the circuits it protects. Check that the lamp has turned off and try it in a few other power points as well. Check that the light switches don’t work.
  5. Turn the main switch back to the ‘on’ position to restore power. Check your clocks and reset them if necessary.
  6. Turn the RCDs back to the on position and ensure the lamp works when plugged into a power point.

Should I have my RCDs checked by an electrician?

You should have your RCDs and wiring checked by a licensed electrical contractor if:

  • You need an RCD to be installed,
  • An RCD trips twice for no apparent reason, or
  • An RCD fails to operate when you test it, or any of the power points or light switches still work after it has operated.

Image by Giovanni Collazo via Flickr