Home electrics
Why does my RCD keep tripping?
An RCD trips when it detects current leaking to earth. Most of the time that's a faulty appliance, water where it shouldn't be, or several appliances each leaking a little and adding up, and you can narrow it down yourself in about ten minutes.
By KS Electrical, Uttoxeter · Updated 12 August 2026 · 5 min read
What an RCD is actually doing
An RCD compares the current flowing out on the live with the current coming back on the neutral. If they don't match, the missing current has gone somewhere else, through a fault, through wet insulation, or through a person. At around 30mA of difference it disconnects, in well under a tenth of a second.
So a tripping RCD is not the RCD misbehaving. It's the RCD telling you something is leaking. The job is to find out what.
The ten-minute test you can do yourself
- Unplug everything on the affected circuits, including the things that live plugged in and get forgotten: chargers, extension leads, the garage freezer, the outside light's transformer.
- Reset the RCD. If it won't reset with everything unplugged, the fault is in the fixed wiring rather than an appliance. Stop there and call an electrician.
- If it holds, plug items back in one at a time, leaving a few minutes between each.
- The item that trips it is your culprit. Note it and stop using it.
Kettles, immersion heaters, washing machines, tumble driers, outside lights and tired extension leads account for a large share of these. Heating elements fail by leaking to earth, so anything with an element in it is a prime suspect.
When it's not one appliance
Sometimes nothing individually trips it, but it goes when several things are on together. That's cumulative earth leakage: every appliance leaks a tiny amount by design, and enough of them on one RCD adds up to the trip threshold.
It's most common on older boards where a single RCD covers half the house. The fix is usually splitting the load, moving to individual RCBOs so each circuit has its own protection, which also means a genuine fault stops taking half the house down with it.
The weather test
If it only trips when it rains, or the morning after, the fault is water getting in somewhere: an outside light, a garden socket, a shed supply, or a cable damaged where it leaves the wall.
That's a genuinely useful thing to tell your electrician, because it narrows the search enormously. Intermittent faults are hard to find precisely because they have to be present to be measured.
When to stop and call
- It won't reset with everything unplugged.
- There's a burning smell, scorching, or a socket or switch that's warm.
- Anyone has felt a tingle or a shock from an appliance, a tap or a switch, however slight.
- It trips repeatedly with no pattern you can find.
FAQs
Related questions
Is it safe to keep resetting a tripping RCD?
Once, to see whether it holds, is reasonable. Repeatedly resetting a device that keeps going is not. It's disconnecting because it's detecting leakage, and the underlying fault doesn't go away because you pushed the switch back up.
Why does it only trip at night?
Usually something on a timer or thermostat that only runs at night: immersion heaters, storage heaters, freezers cycling, or outside lights coming on. Have a look at what's actually switching on at that time.
Should I replace my RCD?
Rarely the answer on its own, the device is normally working correctly. What often does help is moving from one RCD covering many circuits to individual RCBOs, so faults are isolated to the circuit they're on.