It’s one of the most common calls we get. The power drops out, someone goes to the switchboard, flicks the safety switch back up, and a few minutes or a few days later it happens again. Sometimes it won’t reset at all.
A tripping safety switch is annoying, but it’s almost always doing exactly what it’s meant to do. The goal is to find out why, not to stop it tripping. Here’s how we approach it, and what you can safely check before calling us.
What a safety switch actually does
A safety switch, also called a residual current device (RCD), constantly compares the current flowing out on the active conductor with the current coming back on the neutral. In a healthy circuit those are the same. If some current is leaking somewhere else, for example through damaged insulation, water, or a person, the RCD detects the imbalance and cuts the power in a fraction of a second.
That’s different from a circuit breaker, which trips when a circuit draws too much current, such as too many heaters on one circuit. Many modern boards use combined devices called RCBOs that do both jobs for a single circuit. Knowing which device tripped is a useful first clue.
The most common causes
A faulty appliance
This is the number one cause we find. Appliances with heating elements are the usual suspects: kettles, toasters, washing machines, dishwashers, fridges with defrost elements, hot water systems and portable heaters. As elements age, their insulation breaks down and they start leaking current to earth.
Moisture
Water and electricity don’t mix, and on the coast, moisture finds its way in. Outdoor power points, garden lights, pool equipment and fittings under eaves are common trouble spots, especially after heavy rain or when a storm blows water sideways into fittings. If your trips cluster around wet weather, moisture is a strong suspect. Salt air makes it worse, which we cover in our article on salt air corrosion.
Damaged or ageing wiring
Older cable insulation can become brittle and crack over time. Cables can also be damaged by rodents in the roof, by a screw or nail during renovations, or by heat. These faults can be intermittent and difficult to find without the right test equipment.
Too many circuits on one safety switch
Every appliance leaks a tiny amount of current as a normal part of how it works. On their own, these amounts are harmless. But when an older installation has one safety switch covering the whole house, all those small leakages add up and can push the RCD close to its trip threshold. It then trips on something minor. Splitting circuits across more safety switches often solves this, and it’s one of the reasons we recommend it during a switchboard upgrade.
A faulty safety switch
It’s less common, but RCDs do fail. We test the device itself as part of any fault-finding job rather than assuming it’s the problem.
What you can safely check yourself
These steps don’t involve opening anything or touching wiring. They just help narrow down whether an appliance is the cause.
- Unplug everything on the affected circuits. If you’re not sure which circuits those are, unplug everything you reasonably can.
- Reset the safety switch. If it stays on with everything unplugged, an appliance is the likely culprit.
- Plug appliances back in one at a time, switching each on and waiting a moment. When the switch trips, you’ve probably found the faulty appliance.
- Stop using that appliance and have it repaired or replaced.
If the safety switch trips even with everything unplugged, or won’t reset at all, the fault is likely in the fixed wiring, a light fitting, a hardwired appliance or the device itself. That’s when you need a licensed electrician.
What you should never do
- Don’t hold the switch in the on position or tape it up. It’s trying to protect someone from a shock.
- Don’t remove covers from the switchboard, power points or light fittings to look for the problem.
- Don’t ask anyone to bypass or remove the safety switch. A licensed electrician won’t do it, and anyone who offers to is putting you at risk.
- Don’t keep resetting it after something has smoked, sparked or smelled like burning. Turn off the main switch if safe and call for help.
Electrical work on fixed wiring by unlicensed people is illegal in Queensland and NSW, and for good reason.
How we find the fault
When the simple checks don’t solve it, we use insulation resistance testers and other equipment to test each circuit and isolate where the leakage is coming from. We work systematically, circuit by circuit, then through the fittings and outlets on the faulty circuit, until we find it.
Intermittent faults, the ones that only trip after rain or once every few days, can take longer to track down. It helps a lot if you can tell us when it happens, what was running at the time and what the weather was doing. Notes on your phone are genuinely useful. You can read more about how we approach this on our electrical fault finding page.
Test your safety switches regularly
Safety switches have a test button for a reason. Pressing it should trip the device straight away. It’s good practice to test them every few months, and a common suggestion is at the change of seasons. If a safety switch doesn’t trip when you press the test button, it needs attention from an electrician.
If your home only has one safety switch, or none, it’s worth considering an upgrade. We cover the Gold Coast, Brisbane, Logan and the Northern Rivers, and we’re happy to have a look at your board and give you a clear answer on what it needs. See our safety switch page for more detail.
Safety note: electrical work in Queensland and NSW must be done by a licensed electrician. This article is general information, not advice for your specific property. If something looks or smells wrong, switch off at the main switch if it’s safe to do so and call an electrician.