Lifesavers – RCDs and Electrical Safety
[ Last Updated 15 January 2008 ]
What is a Residual Current Device?
An RCD is an electrical safety device which provides protection by rapidly disconnecting the electricity supply in many situations where someone could otherwise receive a fatal electric shock. They constantly monitor the electric current flowing along a circuit. If there is an earth-fault, the RCD will sense an out of balance current and trip, disconnecting the supply of electricity.
It is a legal requirement for all new houses to be fitted with RCDs, including any extensions to existing houses. But RCDs can easily be fitted to existing homes as well. They offer excellent protection in damp areas of your home and when working with equipment outside.
Types of RCDs
There are three types of RCDs:
- Switchboard RCD
These are installed at the switchboard to provide protection of selected circuits or groups of circuits. A switchboard RCD is the best option in most situations, as it protects all the electrical wiring and appliances supplied from that circuit. The law requires these to be installed only by a licensed electrician or electrical inspector.
- Socket outlet RCDs
These are RCDs that are built into standard socket outlets (power points) to provide protection to equipment plugged into that outlet and, if required, downstream protection of other outlets. The Ministry of Consumer Affairs’ Energy Safety Service recommends that these are installed by a licensed electrician.
- Portable RCD
These are RCD (often incorporated into an extension cord) that plug directly into socket outlets (power points) and then an appliance or extension cord plugs into them. The RCD can be moved from socket outlet to socket outlet as needed. These are very useful when using electrical equipment (such as electric lawn mowers and power tools) outside or in a damp environment. It is very important to use an RCD when working with electrical equipment outside. It is all too easy to accidentally slice through an electric cable. Portable RCDs can be bought at hardware shops and electrical equipment suppliers.
Testing Your RCDs
You can test your socket outlet or portable RCDs by plugging in a small electric appliance (such as a nightlight). Press the ‘test’ button. If the appliance turns off, the RCD is working. If it stays on, get your RCD checked by a licensed electrician. Make sure you press "reset" once the test is complete. You should test these RCDs regularly e.g. every three months. It’s a good idea to test switchboard RCDs every six months by checking that it trips when the "test" button is pushed.
Important Tips: When using electricity outside, you should always use an RCD to protect against electric shock. And remember:
- Water is a good conductor of electricity - if you are wet and in contact with the ground, it is even easier for electricity to flow through you. RCDs offer excellent protection in damp areas of your home where there are electric fittings, and when working with electrical equipment outside.
- Always check your power cords and appliances for damage before using them. If they are damaged have them repaired or replace them. Ask the repairer to fit an inspection tag to show that they have been tested properly.
- RCD protection minimises the risk of serious electric shock. It does not eliminate that risk. If you think there is an electrical fault with your house’s wiring or with an appliance, turn it off and get it checked by a licensed electrician.
RCDs can be purchased from electrical wholesalers and almost any hardware stores.
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