What a safety switch does
A safety switch, also called an RCD (residual current device), keeps watch on the electricity flowing through a circuit. If some of it starts leaking where it shouldn’t, for example through a person or through water, it cuts the power in a fraction of a second.
That’s a different job from an ordinary circuit breaker, and it’s why a safety switch is one of the most useful protections in a home.
Safety switch vs circuit breaker
- A circuit breaker protects the wiring. It trips if a circuit is overloaded or short-circuits.
- A safety switch protects people. It trips if current leaks to earth, for example through a person.
- Many boards have both. Some devices (called RCBOs) combine the two in one.
How to tell if you have one
Open the outer door of your switchboard and look for switches with a small test button, usually marked T or Test, and often labelled RCD or safety switch. A board with only fuses, or only plain switches and no test buttons, probably has none.
If you’re not sure, a licensed electrician can tell you quickly. Our guide to reading your switchboard shows what to look for.
How to test it
- Warn everyone, and save any work on computers. Pressing the button cuts power to the circuits it protects.
- Press the test button. The switch should flick off straight away.
- Switch it back on.
- If it doesn’t trip when you press the button, call a licensed electrician.
Regulators and manufacturers commonly suggest testing about every three months.
Why does mine keep tripping?
A tripping safety switch is doing its job. Common causes are a faulty appliance, water getting into a fitting or appliance, and a wiring fault.
- Unplug or switch off everything on the affected circuit.
- Switch the safety switch back on.
- Plug things back in one at a time. If it trips when you plug something in, that appliance is the likely cause. Leave it unplugged and have it checked.
- If it trips with everything unplugged, or you can’t find the cause, stop and call a licensed electrician.
Don’t keep resetting a switch that trips straight away, and never bypass or wedge it. If there is burning, smoke, or someone has had a shock, call 000.
Do I need one?
Requirements depend on the age of the home and the work being done. New work generally has to include them, and many older homes don’t have them or only protect some circuits. A licensed electrician can tell you what your home has and what would be worth adding. See safety switch work and switchboard upgrades.
If you rent, ask your landlord or agent. Safety checks and smoke alarms are often handled together.
General information only. Rules and requirements can change, and what applies depends on your home and the work. A licensed electrician, or NSW Fair Trading, can confirm what applies to you.