Why does my RCD keep tripping?
An RCD tripping is not the RCD failing. It is the RCD detecting current leaking to earth and cutting the supply, which is exactly what it exists to do. The job is finding out where the leak is.
What an RCD is reacting to
An RCD compares the current flowing out with the current returning. If a small amount goes missing, typically 30mA on a domestic circuit, it assumes that current is finding another path to earth and disconnects in a fraction of a second.
That missing current can come from a genuine fault, from water where it should not be, or from the accumulated small leakages of several appliances adding up to the trip threshold. The last one is why tripping is often intermittent and infuriating to chase.
Safe checks you can do yourself
Do this with the board in front of you and without removing any covers. Switch off all the MCBs, reset the RCD, then switch the MCBs back on one at a time. The one that trips it identifies the circuit at fault.
Then unplug everything on that circuit, reset, and plug items back in one by one. Kettles, washing machines, dishwashers, immersion heaters, freezers, outdoor lights and anything in a shed or garage are the usual suspects.
- Turn off all MCBs, reset the RCD, restore circuits one at a time
- Unplug appliances on the tripping circuit, reintroduce them individually
- Check outdoor sockets, garden lighting and shed supplies after rain
- Note whether tripping follows weather, time of day or a specific appliance
- Do not remove the consumer unit cover or any accessory front
When to stop and call someone
Stop immediately if you smell burning, see scorching, find a hot accessory, or if the RCD will not reset at all with every circuit off. Those are not situations to keep testing your way through.
Also call if the trip cannot be traced to a single circuit. That pattern usually means cumulative leakage across the installation, which needs insulation resistance testing to quantify rather than trial and error.
The fixes that usually follow
The common outcomes are: a faulty appliance replaced, water ingress at an outdoor accessory corrected, a damaged cable repaired, or a board reconfigured so circuits are split across more than one RCD instead of all sitting on one.
That last one is worth knowing about. Older split-load boards put half the house behind a single RCD, so one small fault takes out the fridge, the freezer and the lights together. Splitting circuits across RCBOs solves the nuisance as well as the fault.
Official guidance
This guide is general information. For the final word on your own situation, use the official sources below.
Common questions
Is it safe to keep resetting the RCD?
Resetting once to identify the circuit is reasonable. Repeatedly resetting to keep living with a known fault is not, because the fault is still there.
Can a freezer trip an RCD?
Yes, ageing motors and heating elements are common causes. It is one of the first appliances worth isolating.
Why does it only trip when it rains?
That points strongly at an outdoor socket, garden light or shed supply letting water in. It should be found and corrected rather than left.