Breaker or RCD: what's the difference?
Circuit breakers (MCBs) protect a single circuit, such as the upstairs lights or the kitchen sockets, and switch off if the circuit is overloaded or there's a fault. RCDs (residual current devices) watch for current leaking to earth, which can happen if someone touches a live part or a cable or appliance is damaged, and switch off very quickly. Some boards use RCBOs, which do both jobs for one circuit.
Only touch the consumer unit with dry hands, and never remove its cover. If it's hot, buzzing, smells of burning or shows scorch marks, leave it switched off and call an electrician.
How to reset it
- Look at the consumer unit and find the switch that is down (off) or in the middle position.
- Unplug or switch off appliances on the affected circuit. For an RCD, that can be several circuits.
- Push the tripped switch firmly back up to on.
- If it stays on, plug appliances back in one at a time. If it trips again when one goes back in, that appliance is the likely cause: stop using it and get it checked.
- If it trips straight away with everything unplugged, leave it off. The fault is likely to be in the wiring or an accessory, not an appliance.
Common causes of tripping
- A faulty appliance, often a kettle, washing machine, fridge, outdoor equipment or anything with a heating element
- Too much load on one circuit (several heaters, for example)
- Water getting into an outdoor socket, light or junction box
- Damaged cable, for example from a nail or screw
- Ageing wiring or accessories
RCDs have a test button. The manufacturer usually recommends pressing it periodically: it should switch off straight away, and you then switch it back on.
- It keeps tripping and you can't link it to one appliance
- It trips with nothing plugged in
- You have an old fuse board with no RCD protection
- There's any sign of heat, burning or damage
Sources and further reading
- Electrical Safety First – Why you need an RCD
- IET – BS 7671 Wiring Regulations
- Electrical Safety First
General guidance only, based on the sources above. Last reviewed October 2026. It isn't a substitute for an inspection by a qualified electrician.