An RCD keeps tripping because it is detecting current leaking out of the circuit to earth, usually from a wet outdoor fitting, a failing appliance element, or degraded wiring insulation. You can narrow it down at home by switching every circuit off, resetting the RCD, then restoring one circuit at a time until it drops out.
That last step is where most guides stop, so this one covers the process of actually finding the fault.
What is your RCD actually reacting to?
An RCD compares the current flowing out to your appliances with the current coming back, and cuts the power the moment those two stop matching. Any difference means current has found a second path to earth, through wet insulation, a damaged cable, or a person touching a live part. Domestic safety switches in Australia act at about 30 milliamps.
It measures whether the electricity is going where it should, not how hard the circuit is working. That is why a single damp power point can shut down a circuit carrying almost no load.
Why does the RCD trip when the circuit breaker does not?
They protect against two different faults. A breaker watches for too much current through the circuit, as with an overload or a dead short. An RCD watches for current escaping it. A leak to earth can be far too small to trouble the breaker while still being enough for the RCD to act on.
The breaker protects the wiring in your walls. The RCD protects you. Our guide on why a circuit breaker trips when nothing is turned on covers the devices in your board and the causes behind nuisance trips.
What the trip pattern tells you
Before you touch the switchboard, think about when it trips, because the timing narrows the search faster than anything else.
| Trip pattern | Most likely cause | What it usually needs |
|---|---|---|
| Trips during or after rain | Water in an outdoor power point, garden light, or a weathered cable seal | Sealing or replacing the affected fitting |
| Trips at the same time each day | A timed appliance such as a pool pump, hot water element, or dishwasher | Testing that appliance on its own |
| Trips only when one appliance runs | A failing element or motor winding in that appliance | Appliance repair or replacement |
| Trips randomly but resets fine | Accumulated leakage from several appliances on one RCD | Splitting circuits onto RCBOs |
| Will not reset with everything switched off | A fault in the fixed wiring, a hard wired appliance, or a failed RCD | An electrician, and often switchboard work |
How do you find which circuit is causing it?
Work from the switchboard using only the switches on the front of the board, and bring the circuits back one at a time. Never remove the cover or touch anything behind it. The process is straightforward:
- Switch off every circuit breaker, leaving the main switch and the RCD alone.
- Reset the RCD. With every circuit isolated it should hold. If it still will not reset, skip to the section below on faults that persist with everything off.
- Turn the circuits back on one by one, pausing a few seconds after each. Most boards are labelled, so note what each feeds.
- When the RCD drops out, the circuit you just switched on holds the leak. Leave it off and restore the rest so the house has power while you keep looking.
If your board still runs ceramic rewireable fuses, or has no safety switches at all, stop here. Those boards cannot be tested this way.
How do you find which appliance is causing it?
Unplug everything on that circuit, reset the RCD, then plug items back in one at a time and wait. Many faults only appear once an element heats up or a motor reaches speed, so give each appliance a couple of minutes and actually run it rather than just plugging it in.
The usual culprits combine heat, water, or age: kettles with corroded elements, older fridges, washing machines, hot water systems, pool pumps, and outdoor lighting. Anything that has sat in a damp garage deserves early suspicion.
Traced it to a circuit but not a cause?
That is the point where testing equipment is needed. DM Electrical is Level 1 and Level 2 ASP accredited and based in Brookvale, so a fault in the switchboard, the consumer mains, or the service connection is handled by the same team. Available 24/7 across the Northern Beaches and wider Sydney.
What if it trips with everything unplugged?
A trip with every appliance disconnected points at the fixed wiring, a hard wired appliance, or the RCD itself. Hard wired items are easy to forget because there is no plug to pull: ovens, cooktops, hot water systems, and air conditioners all sit permanently on their circuits. Otherwise the leak is in the cabling, which can mean water in a conduit, a nail through a cable, or insulation that has aged out.
Locating that needs an insulation resistance test, and the repair may involve replacing a section of cable or upgrading the switchboard. If a whole side of the property has gone dark rather than one circuit, the problem may sit upstream of your board, which we cover in our guide on half the house having no power.
When should you stop and call an electrician?
Stop testing and call someone if there is any sign of heat, damage, or a shock risk. Specifically:
- The RCD will not reset at all, or trips again within seconds of resetting.
- There is a burning smell, scorch marks, or discolouration at the board or a power point.
- Anyone has felt a tingle or a shock from an appliance, a tap, or a light switch.
- The board runs ceramic rewireable fuses, or has no safety switches fitted.
- Power is out to a whole section of the property rather than one circuit, which is a job for a 24/7 emergency electrician and may involve the service fuse rather than your board.
Repeated tripping is the system doing its job. Treating it as a nuisance to reset around is how a small fault becomes a fire or a shock.
Frequently asked questions
Why does my RCD trip but my circuit breaker stays on?
They watch for two different faults. A circuit breaker trips when too much current flows through the circuit, such as an overload or a short. An RCD trips when current escapes the circuit and finds a path to earth, which is what happens through damp insulation or a failing element. A small earth leak is nowhere near enough current to bother the breaker.
Is it safe to keep resetting my RCD?
Resetting once to see if the trip was a one off is reasonable. Resetting repeatedly is not. The RCD is reporting that current is leaking somewhere it should not, and that path may be through damp wiring, a damaged cable, or a person. If it trips again within a short time, stop resetting it and get the circuit tested.
Why does my RCD only trip when it rains?
Water is the most common cause of nuisance tripping in Sydney homes. Rain gets into an outdoor power point, a garden light, or a weathered seal, and gives current a path to earth. The leak often dries out by the afternoon, which is why the fault seems to come and go with the weather.
Do I need a separate RCD for every circuit?
Not one per circuit, but splitting the load is the practical fix for a board that trips often. Older boards commonly run many circuits through a single RCD, so leakage from several appliances adds up until it crosses the trip threshold. Fitting RCBOs, which combine breaker and RCD protection on one circuit, isolates a fault to that circuit instead of blacking out the house.
The bottom line
An RCD that keeps tripping is reporting a real leak to earth, not misbehaving. Most of the time you can find it by isolating the circuit at the board, then the appliance on that circuit. If it trips with everything off, will not reset, or your board has no proper safety switches, hand it over. DM Electrical holds Level 1 and Level 2 ASP accreditation and works across the Northern Beaches, North Shore, Eastern Suburbs, and wider Sydney. Get in touch and we will find what is leaking.