Tripped breaker or blown fuse: resetting safely – and when not to

Current heats every wire it flows through – the more current, the warmer. Wiring in the walls is designed for a certain load. A fuse contains a thin wire that melts through when there is too much current and breaks the circuit; it then has to be replaced. A circuit breaker does the same mechanically and can be switched back on. It responds to two things: a sustained overload and, very quickly, a short circuit.

The residual-current device (RCD, called GFCI in some countries) watches for something else. It compares the current flowing out to the appliances with the current coming back. If they are not equal, current is leaking along a wrong path somewhere – through a faulty appliance, through moisture or, in the worst case, through a person. Then it switches off very quickly. That makes it an important protection against electric shock.

So when such a switch trips, it is a warning, not a fault in itself. It has done its job. The question is not “How do I get it back on?” but “Why did it trip?”.

What is allowed and sensible is a small, clearly limited routine: first check whether only your home or a single circuit is affected. If the whole neighbourhood is dark, it is not your consumer unit – then do not switch anything and wait for information from the network operator. If only one circuit is out, switch off and unplug the appliances in that area, especially those just switched on or that have got wet.

Then, with dry hands, push the tripped switch fully down and back up again. A screw-in fuse may only be replaced with an equivalent one, and only where the holder is designed for this. Then plug the appliances back in one at a time. If it trips with a particular appliance, stop using it and have it checked.

Not allowed and dangerous: unscrewing consumer-unit covers, opening sockets, switches or wiring, bypassing a fuse or fitting a higher-rated one. Which tasks laypeople may do differs from country to country; in many countries fixed electrical installations are legally reserved for qualified people. Anything beyond resetting belongs to a qualified electrician.

A higher-rated fuse or a bypass switches off the guard. The wiring in the wall can then overheat without anything cutting out – invisibly, behind plaster and wallpaper. That is how fires can start. So the rule has no exceptions: if it trips repeatedly, do not force it.

After flooding or water ingress, do not switch the power back on yourself and do not approach the consumer unit while standing in water. Contact the network operator or a qualified electrician. Never switch anything with wet hands or barefoot on a wet floor.

If something smells burnt, sockets are warm or discoloured, there is crackling, or the breaker trips even with nothing plugged in: leave it off and call a qualified electrician. If there is smoke or fire, get everyone out of the building and call the local emergency number (112 in the EU).

You should know where the consumer unit is before the lights go out. Keep a torch or head torch within reach nearby. If the unit is not labelled, a qualified electrician or the landlord can help identify the circuits – then you can see at a glance which switch is for the kitchen and which for the bathroom.

Note the phone number of an electrician or the landlord somewhere you can find it without power. Many residual-current devices have a test button. How often to press it is stated in the instructions or local recommendations; when pressed, the switch must trip, otherwise it should be checked by a professional.

A classic case: in winter the kettle, toaster and a fan heater are all running in the same kitchen – the circuit breaker trips. That was overload. After resetting, it is better to spread the appliances out or use them one after the other.

Another case: after a rainstorm the RCD keeps tripping as soon as the outdoor socket or garden lighting is switched on. Moisture is probably involved here. The affected part stays off until a professional has looked at it. An RCD that “keeps tripping” is not an annoying component; it is pointing to a real fault.