Short answer
A breaker protects the cable. If it trips after a lot has been on for a while, it is overload: too many appliances on one circuit. If it trips immediately when switched on, it is a short circuit and there is a fault in the installation or in an appliance. Reset it once; if it trips again straight away, leave it off.
Who this article is for Anyone with a circuit that keeps going off. You may reset it yourself, but not search behind the consumer unit cover.
What a circuit breaker does
A circuit breaker protects the cable, not your appliances. It makes sure no more current ever flows through a cable than it can handle, because an overloaded cable gets hot and that is how a fire starts.
It can trip in two ways, and the difference tells you almost everything.
Overload: it trips after a while
There is more on the circuit than it can handle, but not massively more. The breaker slowly warms up and snaps off after tens of seconds to minutes.
Typical picture: the tumble dryer and the kettle together, or a few appliances in the kitchen coming on at the same time.
What you can do about it:
- spread the appliances over different circuits
- do not switch on heavy loads at the same time
- have a circuit added if it keeps happening
How many circuits there should actually be is covered in how many circuits and using dedicated circuits.
Short circuit: it trips immediately
Live and neutral touch each other directly. The current rises to hundreds of amps in a fraction of a second and the breaker cuts out immediately, often with a click.
Causes:
- a faulty appliance, from a blown bulb to a burnt-out motor
- a damaged cable, for example a screw or a nail through it
- damp in an outdoor socket or in a light
- a wrong connection after a job
How to track down a short circuit
- Switch off the circuit.
- Unplug everything on that circuit. Everything.
- Switch the circuit on. If it now stays on, it is in an appliance.
- Plug the appliances back in one by one. The appliance that makes it trip is the culprit.
- If it keeps tripping even without appliances, the fault is in the installation. Leave the circuit off and call.
One of the few faults where you can really get a long way yourself.
This is one of the few faults where you can really get a long way yourself.
Breaker, RCD or both
If the RCD has also tripped as well as the breaker, an earth fault is involved and it is a different story. That is covered in RCD keeps tripping.
If the breaker only trips when a specific appliance is switched on, that appliance is the suspect and not the installation.
Do not
Replace a breaker with a heavier one to get rid of the problem. The breaker is matched to the cable behind it. A heavier breaker means the cable can get hot without anything switching off. That is exactly the situation you do not want.
From my own work
At a home in Sittard the kitchen circuit tripped every morning. A kettle, a Quooker, a microwave and a coffee maker were all on one circuit, and all four were on around eight o'clock. No fault, just too much on one circuit. The kitchen now has three circuits, and that was the end of the problem.
When to call an electrician
- The breaker trips again immediately when you reset it
- There has been a bang or a flash
- It happens more and more often without you having changed anything
If you suspect a short circuit: leave the circuit off and call. During the day on +31 43 204 18 26, outside office hours through the fault service.
Frequently asked questions
Can I fit a heavier breaker?
No. The breaker is matched to the cable behind it. A heavier one means the cable can get hot without anything switching off.
How often may I reset a breaker?
Once. If it trips again straight away, there is a short circuit and you leave it off until someone has looked at it.
Can a breaker wear out over the years?
Yes. A breaker that has tripped often or is decades old can start switching more slowly or too early. I measure that during an inspection.
Further reading
RCD keeps tripping: how to find the cause yourself
Usually it is one appliance and not your installation. In four steps you find out yourself which one, and you read exactly where it stops and you need to call.
Lights flickering or dimming: what it tells you
Flickering in one light is usually the bulb or the dimmer. Flickering throughout the house is a reason to measure.
Power out in one room: the step-by-step plan
One room without power is almost always one circuit. In four steps you know which one, and what to do if nothing seems to have tripped.
Questions and comments
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