The short answer
A safety switch (RCD) trips when it detects current leaking to earth, which is exactly what it is designed to do. The most common cause is a faulty appliance, but it can also be water getting into an outdoor power point or light, or damaged wiring. You can safely unplug everything on that circuit, reset the switch once, then plug things back in one at a time to see if a particular appliance sets it off. If it trips with everything unplugged, trips again straight away, or you notice burning, buzzing or a tingle, leave it off and call a licensed electrician. Never tape, wedge or hold a safety switch on.
What a trip is telling you
An RCD compares the current flowing out to the circuit with the current coming back. If some of it is leaking to earth, whether through a damaged appliance, moisture or a person, the two don't match and it switches off. Household RCDs are rated at no more than 30 mA, so they react to quite small leaks.
So a trip is a sign of a fault, not a faulty safety switch. The job is to find the fault. Occasionally the RCD itself is the problem, but that is something an electrician confirms by testing it.
Safe checks you can do
These steps don't involve opening anything up, and they are things any householder can do:
- Note what was happening. Was it raining? Did it trip when the kettle, washing machine or air conditioner started? Did it trip at the same time every day? This helps a lot later.
- Check which circuits are off. Look at the switchboard. If you have shared RCDs, one trip can take out up to three circuits. If you have an RCBO on each circuit, only one device will be down.
- Unplug everything on the affected circuits. Switch off at the wall and pull the plugs, including the fridge, the TV and anything outside.
- Reset the switch once. Push it back to the on position.
- If it holds, plug things back in one at a time. Wait a little between each. If it trips when a particular appliance goes back in, you've probably found the culprit. Stop using that appliance and get it checked or replaced.
- If it trips with everything unplugged, stop. The fault is likely in the fixed wiring, a power point, a light or hardwired equipment. That needs a licensed electrician.
Don't keep resetting it over and over. Each trip is the device protecting you from a fault.
Common causes
| Cause | Typical clue |
|---|---|
| Faulty appliance (kettle, toaster, washing machine, heater, fridge) | Trips when that appliance is switched on or plugged in |
| Water in outdoor power points, lights or garden lighting | Trips during or after rain or storms, or when sprinklers run |
| Damaged cable (a nail or screw, rodents, a cable squashed in a shed) | Trips with appliances unplugged, may be after building work |
| Hardwired equipment (hot water system, oven, cooktop, pool pump, air conditioner) | Trips when that equipment cycles on |
| Too much on one shared RCD | Several circuits drop together, harder to pin down |
| Worn or damaged extension leads and power boards | Trips when a lead is used, often outdoors or in a shed |
On Riverina properties, sheds, pumps and outdoor lighting are common suspects, because they are exposed to dust, heat, water and the odd mouse. Our fault finding page has more on how we track these down.
When it is not a DIY job
DIY electrical work is illegal in NSW. The NSW Government says homeowners shouldn't do electrical maintenance beyond changing a light globe. So:
- don't open power points, light fittings or the switchboard to look for water or burnt wires;
- don't swap the safety switch for a "bigger" one or bypass it;
- don't keep resetting it if it trips straight away.
Call a licensed electrician if the switch trips with nothing plugged in, won't reset, trips again immediately, or if you see scorching, smell burning or hear buzzing.
How we find the fault
Nelson tests the circuits to find where the leakage is coming from, then tells you what he found and what it will cost to fix before he fixes it. Fault finding and circuit tracing are charged by the hour, so the cost depends on how long the fault takes to find. Travel is free close to Wagga and charged further out.
If your board has shared RCDs, a fault on one circuit can keep switching off others, including the fridge. Changing to an RCBO on each circuit means a future fault only drops one circuit. See RCD vs RCBO and, if your board is old, switchboard upgrade cost.
Renting? It's an urgent repair
In NSW, any electrical fault in a rental is an urgent repair, and the NSW Government specifically lists a faulty safety switch, or one that keeps detecting a fault, as an urgent repair. Tenants should report it to the landlord or agent straight away. Landlords must get it fixed within a reasonable time by a licensed electrician. See landlord electrical obligations in NSW.
Common questions
Can a safety switch trip for no reason?
It almost always trips because it detected leakage somewhere, even if the cause isn't obvious. Intermittent faults, such as water getting into an outdoor fitting only when it rains, can make it seem random. Keeping a note of when it trips helps find the cause.
Is it dangerous if my safety switch keeps tripping?
The tripping itself is the safety switch protecting you. The fault behind it can be dangerous, so don't ignore it or bypass the switch. If anyone feels a tingle or shock, stay clear and call Essential Energy on 13 20 80, or 000 for a serious shock.
Why does my safety switch trip when it rains?
Usually because moisture is getting into an outdoor power point, light, garden lighting or a cable joint, and current is leaking to earth. It needs a licensed electrician to find and fix it.
Should I replace a safety switch that keeps tripping?
Not until the cause is found. In most cases the safety switch is working correctly and the fault is elsewhere. An electrician can test the RCD to confirm whether the device itself is faulty.
My safety switch trips when I turn on the kettle. What does it mean?
Most likely the kettle has a fault, so stop using it. If a different kettle works fine on the same power point, replace the old one. If the new one trips the switch too, get the circuit checked by a licensed electrician.