A fuse blows or a breaker trips because it has detected a problem: too much current on a circuit (an overload), a short circuit, or current leaking to earth through a fault or a faulty appliance. Resetting once after unplugging appliances is reasonable. If it trips again straight away, or there is a burning smell, scorch marks, heat, buzzing or water near the electrics, leave it off and get the circuit checked.
Stop and get help if
- you can smell burning, or see scorch marks or melted plastic on a socket, switch or the consumer unit
- a socket, plug or the consumer unit feels hot or is buzzing
- there is water near electrics, such as a leak through a light fitting
- it trips the moment you reset it, even with everything unplugged
- anyone has had an electric shock
- you have just drilled or nailed into a wall
In any of these cases leave the circuit switched off, keep away from the affected fitting and get an electrician to trace the fault. Our fault finding and power restoration page explains what that involves.
Which device has tripped?
Circuit breakers (MCBs) are the small switches, one per circuit, usually marked with a rating such as B32 or B6. They trip when a circuit draws too much current or there is a short circuit.
An RCD is usually a wider switch with a test button, and it often protects several circuits at once. It trips when it detects current leaking to earth, so a fault on any circuit it covers switches them all off. An RCBO does both jobs for a single circuit. In an older board with rewirable fuses, the fuse wire melts instead of a switch moving.
Common causes
- Overload: too many high-power appliances on one circuit at once, such as a kettle, heater and tumble dryer, or a heavily loaded extension lead.
- A faulty appliance: worn elements in kettles, washing machines and dishwashers are frequent causes of RCD trips.
- Water: outside lights and garden sockets after heavy rain, or a leak reaching a fitting.
- Damaged cable: from drilling, nails, rodents or age.
- Loose or worn connections, often at a socket or switch that is warm or discoloured.
A worn socket or switch can be a fault in its own right, and our socket and switch repairs page covers those.
Safe checks you can do
If none of the warning signs above apply, these steps are safe for a householder:
- Switch off and unplug everything on the circuit that has tripped.
- Reset the breaker or RCD once.
- If it stays on, plug appliances back in one at a time, waiting a little between each.
- If it trips when one appliance goes back in, leave that appliance unplugged and have it repaired or replaced.
- If it trips with everything unplugged, the fault is in the fixed wiring or a fitting. Stop there.
Do not remove covers from the consumer unit, hold a breaker in the on position or keep resetting it. If you have rewirable fuses, only ever replace fuse wire with the rating marked on the carrier, never thicker wire or anything else, and if it blows again leave it out and get the circuit checked.
When the whole property goes off
Check whether the main switch or an RCD in your consumer unit has tripped, and whether your neighbours have power. If they are off too, the problem is likely to be the supply. Call 105, the UK power cut number, to reach your network operator. Never touch the sealed main fuse next to the meter, which belongs to the network.
If only your property is off and the main switch will not stay on, leave it off and get help.
When it keeps happening
A circuit that trips again and again is telling you something is wrong, even if it resets each time. It may be an overloaded circuit that needs splitting, a cable fault that only appears when damp, or an older board that is struggling. If your board still has rewirable fuses or no RCDs, our guide to the signs a consumer unit needs upgrading is worth reading, and our fuse replacement page explains how the cause is found rather than just reset.
Common questions
Is it safe to keep resetting a breaker?
No. Resetting once after unplugging appliances is reasonable, but a breaker that trips again is telling you the fault is still there. Repeated resetting can let a fault overheat, so leave it off and get the circuit tested.
Why does my RCD trip when it rains?
Water getting into an outside light, a garden socket or a damaged external cable lets current leak to earth, which the RCD detects. It often stops once things dry out, but the fault remains and should be found and repaired.
Why does it trip at night when nothing is switched on?
Appliances that run by themselves, such as fridges, freezers, heating controls and timers, can trip a circuit when they cycle on. A cable fault that changes with temperature or damp can do the same, so if unplugging appliances does not find it, the wiring needs testing.
Can I use thicker fuse wire so it stops blowing?
No. Fuse wire must match the rating marked on the carrier, because the fuse is there to protect the cable. Thicker wire lets the cable overheat before the fuse blows.
What number do I call in a power cut?
Call 105 from a landline or mobile to reach your local electricity network operator. They can tell you whether there is a fault on the supply in your area.