Plenty of Australian homeowners believe they have safety switches because the switchboard has rows of switches. Many are looking at circuit breakers, which protect wiring, not people. The distinction is worth two minutes of your attention, because it is the difference between a tripped circuit and an electrocution.
This guide explains what an RCD actually does, where the law generally stands, how to test the ones you have, and what it costs to bring an older board up to scratch.
Safety switch versus circuit breaker: different jobs
A circuit breaker protects the wiring. It trips on overload or short circuit, preventing cables from overheating and starting fires. It does nothing to stop current flowing through a person.
A safety switch, properly a residual current device or RCD, monitors the balance between current flowing out and current returning. If even a small amount leaks to earth, such as through a person touching a live wire, it cuts the power in a fraction of a second, fast enough to prevent a fatal shock. Modern boards combine both functions in a single device called an RCBO, one per circuit.
What the rules generally require
Requirements differ by state and by the age and use of the property, but the direction is uniform: new installations and new circuits must have RCD protection, and the current wiring rules require it across effectively all final circuits in new domestic work, lights included.
Rental properties attract the strictest retrofit obligations, with several states requiring RCD protection as a condition of leasing. Owner-occupied older homes are usually not forced to retrofit until electrical work is done, but that grandfathering protects the paperwork, not the occupants. Your state electrical regulator publishes the specifics; your electrician will know them cold.
How to test your safety switches
Every RCD has a test button marked T or Test, and pressing it is the only way to know the mechanism still works. Regulators commonly suggest testing every three months or so; twice a year, say when clocks change, is better than never.
- Warn the household, and note anything sensitive that is running before you start
- Press the test button on each RCD: the switch should snap off instantly
- Check which lights and outlets went dead, which tells you what that RCD covers
- Flip it back on and reset clocks and appliances
- If any RCD does not trip when tested, or will not reset, call an electrician promptly
Nuisance tripping: causes and cures
An RCD that trips repeatedly is almost always doing its job: something is leaking current. The usual culprits are moisture in an outdoor outlet or garden fitting, a failing appliance element (kettles, hot water systems, ovens and washing machines lead the list), damaged flexible cords, or rodent-chewed cable insulation.
The DIY diagnostic is unplug and divide: unplug everything on the affected circuit, reset the RCD, then reconnect appliances one at a time until the trip repeats. If the RCD trips with nothing plugged in, the fault is in the fixed wiring and it is an electrician's job. On very old boards where many circuits share a single RCD, splitting them across individual RCBOs also ends the whole-house blackout every time one appliance sneezes.
What upgrades cost
Adding RCD protection to an existing board that has space typically costs a few hundred dollars for a couple of devices, installed and tested. Protecting every circuit individually with RCBOs costs more per circuit but ends nuisance whole-house trips and is the standard on new boards.
If the board is a ceramic-fuse relic with no room for modern devices, RCD protection effectively arrives as part of a full switchboard upgrade, typically $800 to $2,000. Given what the device does, it is among the least discretionary money a homeowner can spend on the house.
Frequently asked questions
How do I know if I have safety switches or just circuit breakers?+
Look for a test button marked T or Test on the devices in your switchboard. Circuit breakers have no test button. If nothing on your board has one, you have no RCD protection and should talk to an electrician.
How many safety switches should a house have?+
Current practice is RCD protection on every circuit, ideally one RCBO per circuit so a fault on one circuit does not black out the house. Older homes often have a single RCD covering only power outlets, which leaves lights, the oven and hot water unprotected.
Why does my safety switch trip when it rains?+
Water is getting into an outdoor outlet, light fitting, junction box or garden appliance and leaking current to earth. The RCD is working correctly. An electrician can isolate which item is wet and fix the sealing or replace the fitting.
Are safety switches compulsory in rental properties?+
Several states require RCD protection in rentals as a condition of leasing, and the trend across the country is toward stricter retrofit rules. Landlords should confirm current requirements with their state electrical regulator rather than relying on what was compliant when the property was bought.