RCD or circuit breaker: which one tripped?
Open your consumer unit (fuse box) and look for the switch that's down. RCDs are usually wider switches with a test button marked T, and each one protects a group of circuits. Circuit breakers (MCBs) are the narrower switches, one per circuit. Some boards use RCBOs, which combine both for a single circuit.
A circuit breaker usually trips because a circuit is overloaded or there's a short circuit. An RCD trips because current is leaking to earth. Knowing which one went helps narrow down the cause.
The most common causes
- A faulty appliance. Kettles, toasters, washing machines, dishwashers and old extension leads are frequent culprits.
- Water or damp. Outdoor lights and sockets, bathroom fittings and anything near a leak can let moisture in.
- Damaged cable. A nail or screw through a cable, or a cable damaged during building work.
- Lots of small leakages adding up. Many appliances on one RCD can trip it between them.
- A worn-out RCD. Less common, but RCDs can fail with age.
How to find the culprit safely
- Unplug everything on the circuits that went off. If you're not sure which ones, unplug everything you can.
- Reset the RCD or breaker once.
- If it stays on, plug appliances back in one at a time. If it trips when one goes back in, that appliance is the likely cause: leave it unplugged and get it checked or replaced.
- If it trips straight away with nothing plugged in, the fault is in the fixed wiring or a fitting. Leave it off and call an electrician.
Never tape, wedge or hold an RCD or breaker in the on position. It's switching off to protect you.
When it's an emergency
Call an electrician straight away if you can smell burning, see scorch marks or sparking, if water has got into a fitting or the consumer unit, or if you've lost power to essential circuits and can't restore it. If there's smoke or fire, get everyone out and call 999. If your neighbours have lost power too, it's a power cut: call 105.
Need a hand?
E.A Electrician Ltd is a North London electrical company based in Wood Green, N22, rated 5.0 from 32 Google reviews. See our 24/7 emergency electrician service, or call 07871 056970 for a free estimate.
Quick answers
Is it safe to keep resetting my RCD?
No. If it trips again straight away, leave it off. Repeated resets can hide a real fault. Unplug everything and try once; if it still trips, call an electrician.
Why does my RCD trip when it rains?
Usually because water is getting into an outdoor light, socket or cable. Those fittings need checking and resealing or replacing.
Why does my RCD trip at night?
Often because something switches on by itself, such as a fridge, freezer, heater or immersion heater, and that appliance or its circuit has a fault.
Published by E.A Electrician Ltd. Last updated 1 November 2026.