A circuit breaker that keeps tripping is usually doing exactly what it’s designed to do: cutting the power because something on that circuit isn’t right. The cause might be too many appliances on one circuit, a single faulty appliance, moisture getting into a fitting, or a fault in the wiring itself. The symptom alone can’t tell you which — but when it trips, and which switch trips, narrows it down considerably.
Electrical Safety First’s guidance is direct on this: if an RCD in your fuse box keeps tripping, there is likely to be a fault that needs investigating, whether in an appliance or the wiring.
First, which switch is tripping?
A modern consumer unit (the current name for a fuse box) usually contains a few different protective devices, and they trip for different reasons. Look at which switch has dropped to the “off” position.
| Device | What it usually looks like | What makes it trip |
|---|---|---|
| MCB (miniature circuit breaker) | A narrow switch for one circuit, often labelled “sockets”, “lights”, “cooker” and so on | Too much current on that circuit — an overload, or a short circuit |
| RCD (residual current device) | A wider switch, usually with a “T” or “Test” button, protecting a group of circuits | Current leaking to earth — often from moisture, damaged cables or a faulty appliance |
| RCBO | Looks like an MCB but has a test button | Either of the above, on a single circuit |
This matters because the two types point in different directions. An MCB tripping on the kitchen sockets when the kettle, toaster and microwave are all on suggests overload. An RCD tripping and taking out half the house points more towards an earth leakage somewhere on one of the circuits it protects. Older installations with rewireable fuses or no RCD at all behave differently again, and are worth having assessed in their own right — our guide to consumer units vs fuse boxes explains what separates them.
What the pattern of tripping can tell you
It trips when a particular appliance is switched on
This is the most common and most helpful pattern. Kettles, washing machines, dishwashers, tumble dryers, immersion heaters and anything with a heating element are frequent culprits, because elements can develop a leakage to earth as they age. If the same appliance trips the power wherever you plug it in, the fault is very likely in the appliance, not the wiring.
It trips when lots of things are running at once
An MCB tripping at busy times — cooking, laundry and heaters all on together — suggests the circuit is overloaded. Spreading high-power appliances across different circuits may stop it. If the circuit trips under loads it used to handle without problems, though, something has changed and it’s worth having checked.
It trips in wet weather or after a leak
Moisture is a classic cause of RCD tripping. Outside sockets, garden lighting, fittings in bathrooms and anything below a recent water leak are the usual suspects. If tripping started after a leak or flood, leave that circuit off and have it checked before using it again.
It trips immediately when you reset it, with everything unplugged
If a circuit won’t stay on even with every appliance on it unplugged, the fault is very likely in the fixed installation — the cables, a socket, a light fitting or a connection. That’s not something to work around; leave it off and call an electrician.
It trips randomly, with no obvious trigger
Intermittent trips at night or when nothing in particular is being used are the hardest to pin down. Possible causes include an appliance that cycles on by itself (a fridge, freezer or immersion heater), a fault that only appears when something warms up, damp in a fitting, or several small earth leakages adding up on one RCD. This is the situation where proper electrical fault finding is usually needed, because it can’t be solved by trial and error.
A safe check you can do
Without opening anything up, you can often tell whether an appliance is to blame:
- Unplug everything on the affected circuit, or switch it off at the wall if it’s hard-wired with a switched spur.
- Reset the tripped switch at the consumer unit.
- Plug appliances back in and switch them on one at a time, waiting a little between each.
- If it trips again, note which appliance was last switched on and leave it unplugged.
If it trips with nothing plugged in, stop there — the problem is in the circuit. Only do this check if the consumer unit, sockets and plugs are dry, undamaged and show no sign of scorching.
What not to do
- Don’t keep resetting a breaker that trips straight away. Each reset sends current back into a fault.
- Don’t hold, tape or wedge a switch in the “on” position, and never swap a breaker or fuse for a higher-rated one to stop it tripping. That removes the protection, not the fault.
- Don’t take the cover off the consumer unit or open sockets and fittings to look for the cause.
- Don’t run extension leads from another circuit as a long-term workaround for one that won’t stay on.
Some situations shouldn’t wait at all: a burning smell, scorch marks on a socket or the consumer unit, buzzing or crackling, sparks, or tripping after water has reached electrics. Switch off at the mains if you can do so safely, and treat it as a job for an emergency electrician.
What an electrician will look at
An electrician won’t guess from the symptom either. Typically they’ll ask about the pattern you’ve noticed, then test the circuits and the protective devices to find where the fault lies — measuring insulation resistance on the cables, checking connections at sockets and fittings, and confirming the RCD is tripping when it should rather than too readily. The answer may be a single faulty socket or light fitting, a damaged cable, a worn-out device in the consumer unit, or simply an appliance that needs replacing.
That’s why the details you’ve gathered matter. Which switch trips, how often, and whether it follows a particular appliance, time of day or the weather can save a lot of testing time. Our guide to the signs that a problem needs electrical fault finding includes a simple fault log you can keep before a visit.
Getting it fixed
If you’ve traced the tripping to a faulty socket, switch or fitting, our electrical repairs service covers fixing it. If the consumer unit itself is old, has no RCD protection, or a device inside it seems to be failing, the consumer unit and fuse box services page explains the options. And if you’ve tried the checks above and still can’t find a pattern, that’s the point to stop experimenting and have the circuit tested properly.
