Most of us only think about the switchboard when the power goes off. But one small device inside it, the safety switch, is one of the most important pieces of electrical safety equipment in your home. This guide explains what a safety switch does, how to test it, and when it's time to call a licensed electrician.
What is a safety switch?
A safety switch is also called a residual current device, or RCD. It monitors the electricity flowing through a circuit and cuts the power when something looks wrong.
Tasmania's Consumer, Building and Occupational Services explains that safety switches help protect people from electric shock by disconnecting a circuit when they detect current leaking away. It gives examples of when that can happen:
- an appliance comes into contact with water
- someone drills into a wall and hits a live cable
- a power point or electrical appliance is faulty
Energy Safe Victoria says a safety switch can cut the power within milliseconds when it detects a problem. The catch is that it only protects you if it's working properly and connected to the circuit with the fault.
Safety switch vs circuit breaker
People often mix these up because they sit side by side on the switchboard and look similar.
- Circuit breakers protect the wiring. They switch off when a circuit is overloaded or has a short circuit, which helps prevent overheating and fire.
- Safety switches protect people. They react to current leaking to earth, which is what can happen when electricity passes through a person.
You can usually tell a safety switch apart because it has a button marked "T" or "Test". The Queensland Electrical Safety Office notes there may be more than one, and they can come in different colours, shapes and sizes, so look carefully.
Is every circuit in your home protected?
Not necessarily. Older homes may have one safety switch covering only the power points, or none at all. CBOS Tasmania points out that safety switches may protect some circuits but not others, and recommends getting a licensed electrician to check what you have.
The Queensland Electrical Safety Office encourages homeowners to have safety switches on all circuits, including power points, lighting, air conditioning, stove, hot water and pool equipment.
Requirements for existing homes differ between states. For example, the WA Government says homes there must have at least two safety switches fitted. Rules can change and differ for rentals and home sales, so check with your state's electrical safety regulator or ask a licensed electrician.
How to test your safety switch
Regulators in several states, including the Queensland Electrical Safety Office, Energy Safe Victoria and the NSW Government, recommend testing safety switches every three months. The WA Government adds that you should follow the manufacturer's instructions if they call for more frequent testing.
Here's the general process the regulators describe:
- Tell everyone at home that the power is about to go off, so nobody loses work or gets a fright.
- Go to the switchboard and press the "T" or "Test" button on the safety switch. It should flick to the off position, and you may hear a clunk.
- Check around the house. The lights, power points and appliances that have gone off are the ones protected by that switch.
- Reset the switch by lifting or twisting it back to the on position.
- Repeat for each safety switch on the board.
If you have a fridge or air conditioner on the circuit, CBOS Tasmania and the Queensland Electrical Safety Office suggest waiting two to three minutes before switching the power back on, to avoid damaging the appliance.
What if it fails the test?
If the switch doesn't trip when you press the test button, or it won't stay on after you reset it, it may be faulty. The regulators all say the same thing: call a licensed electrician. CBOS Tasmania specifically warns not to try replacing a safety switch yourself. Electrical work like this needs a licensed electrician.
Why does my safety switch keep tripping?
A safety switch that trips is usually doing its job. It has detected something it doesn't like. Common reasons include a faulty appliance, moisture getting into an outdoor power point or light fitting, or damaged wiring.
Some simple, safe checks you can do:
- Unplug everything on the affected circuit, reset the switch, then plug appliances back in one at a time. If it trips when a particular appliance goes back in, stop using that appliance and have it checked or replaced.
- Notice whether it happens after heavy rain. That can point to water getting into outdoor fittings.
Don't keep resetting a switch that trips straight away, and never try to bypass it. If you can't find an obvious cause, book an electrician to track down the fault.
When to call an electrician
Get a licensed electrician in if:
- your safety switch fails the test or won't reset
- it trips often and you can't trace it to an appliance
- you're not sure whether you have safety switches, or which circuits they cover
- your switchboard still has old ceramic fuses or looks worn or damaged
Adding safety switches is often done as part of a switchboard upgrade. Our guide to switchboard upgrade costs explains what affects the price. After the work is done, you should receive the right paperwork, which we cover in electrical compliance certificates explained.
Before you book, it's worth checking the electrician holds a current licence. See our guide on how to choose an electrician, then find electricians near you, such as electricians in Brisbane.
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Frequently asked questions
How often should I test my safety switch?
Electrical safety regulators in Queensland, Victoria, NSW, WA and Tasmania recommend testing every three months, or more often if the manufacturer's instructions say so.
Can I test a safety switch myself?
Yes. Pressing the "T" or "Test" button is designed for homeowners and tenants to do. Repairing or replacing a safety switch, though, is a job for a licensed electrician.
Is a safety switch the same as a circuit breaker?
No. A circuit breaker protects the wiring from overloads and short circuits. A safety switch protects people by cutting power when it detects current leaking to earth.
I'm renting. What should I do if the safety switch fails?
Tell your property manager or landlord straight away. The WA Government recommends tenants test their safety switches regularly and report any that don't work.
This guide is general information only, not legal or financial advice. Rules change, so check the official sources linked above for your state.