It holds for a few hours, then it's off again. Or it goes the moment the washing machine hits its spin. Maybe it won't reset at all and you're standing at the board in the dark, wondering what's defrosting in the freezer.

We see this every single week across London - in part-rewired Victorian conversions in North London, in ex-council flats still running on tired boards, in new-builds where one gadget too many has tipped a circuit over. A tripping RCD is maddening, but here's what most people miss: it isn't the problem. It's the messenger.

Something on your wiring is leaking current where it shouldn't, and the device is cutting the power before that leak can hurt someone. Ignore the message long enough and you're gambling on the fault staying polite.

What it might mean

Nobody can diagnose this from a search result - anyone naming the cause without testing is guessing. But after years of chasing these faults, the usual suspects line up like this:

A faulty appliance leaking current to earth. The most common cause by a distance. Kettles, washing machines and immersion heaters are the classic offenders - if the trip happens when one particular thing runs, start there.
Moisture in an outdoor circuit, light fitting or junction. Does it go when it rains? Garden sockets and outside lights let water in more often than people think.
Background earth leakage spread across several circuits sharing one RCD. No single fault - just lots of small, legal leaks adding up until the device can't tell the difference.
A cable or accessory quietly deteriorating and developing an earth fault. Common on older runs that have been decorated over for decades.
A borrowed neutral between circuits confusing the RCD. Rarer, but it turns up in homes that have been extended or "improved" in stages.

Possibilities, not a verdict. And it's the same fault list that turns a routine electrical installation condition report into an unsatisfactory EICR - which matters if you ever let the property.

How urgent is it?

Same-day. Not next month, not "when someone's passing". A tripping RCD means there's a live fault somewhere on the installation, and until it's found you don't know whether it's a damp junction box or a cable one knock away from being dangerous.

Two situations move it from urgent to emergency: the RCD won't reset at all, or anything near the board or the sockets smells hot. Either of those - stop, and get an electrician out now.

And whatever happens, don't let anyone "cure" it by holding the device on, taping it closed, or swapping it for something with a bigger rating. That stops the tripping by removing the protection. The fault stays exactly where it was - you've just silenced the one thing warning you about it.

Meanwhile every trip is another round of dead fridges, freezers, alarms and - in some homes - medical equipment. That alone is a reason not to limp along for weeks.

What you can safely check

There's one genuinely useful test you can do without tools. Unplug everything on the affected circuits. Reset the RCD. Then plug things back in one at a time and see what knocks it off. If one appliance does it every time, you've probably found your culprit - stop using it.

Beyond that, be a good witness. Does the trip follow the weather? A specific machine? The same time each evening? That pattern is gold - it can shave a lot of head-scratching off the diagnosis when an engineer arrives.

What not to do: don't hold the RCD closed, don't wedge or tape it, and don't fit a higher-rated device to make the nuisance go away. Every one of those turns a warning into a hazard.

If your detective work finds nothing - or the answer keeps changing - that's your sign it needs proper test equipment, not more resets.

What we check

First job on site: establish exactly which device is tripping and which circuits sit behind it. Boards in older London homes rarely match their labels, so we prove it rather than trust the sticker.

Then it's elimination done properly - splitting the loads and isolating circuits one by one until the fault localises. We measure insulation resistance on the suspect circuits and check the standing earth leakage, because numbers beat hunches: a circuit can look fine and still be leaking enough to take the RCD out the moment the kettle joins in.

Once the culprit's confirmed - appliance, accessory or cable - we don't stop there. The repair gets tested before we call it done, so the fix is proven rather than assumed.

How it's fixed

Depends entirely on what the testing finds. A leaky appliance is the cheap outcome - it gets condemned and life goes on. A damaged accessory or cable section gets repaired and re-tested. And where the real cause is cumulative leakage across circuits that were never meant to share one device, the proper fix is converting the board to per-circuit RCBOs - so one damp garden light can't black out the whole house again.

If the power can't be restored safely - the RCD won't hold on anything - that's a job for an emergency electrician rather than a diary slot.

One thing we'd say from years of doing EICR testing London-wide: the tripping faults people live with for months are often the same defects that later surface as C2 codes on a landlord's report. Finding the fault now, on your terms, costs less than finding it against a compliance deadline.

Tripping RCDs and your electrical safety certificate London

Renting the property out? Then this fault has a paperwork dimension too. An earth fault that keeps taking the RCD out is exactly what an electrical safety certificate London inspection exists to catch, and private rented homes need that inspection on a five-year cycle by law. A known fault sitting unfixed reads very badly on that report - and even worse in an enforcement file.

Call now if the RCD won't reset at all, if anything smells hot, or if the trips are getting closer together - that's a fault developing, not settling. The longer a live earth fault stays hidden, the bigger the job that's waiting once it's finally traced.

Trip switch or RCD keeps tripping in London