Mains tripping

Have lived in this house around five years now and never had an issue with RCDs tripping.

In the last three months I’m experiencing random tripping (mainly overnight) of the 20A Type B RCD on the consumer unit in the lounge (this is an extension).

Here’s what I’ve got plugged in that runs off that RCD:
Power Amp (for AVR)
Sky Q
Blu-ray player
USB plugs for charging
Non NAIM power supply
TP USB power supply
CXN network streamer
Rega P8
Rega Power supply
Rega Aria
Sky router
Hue hub
Fridge (another room)
Washing machine (another room)
CCTV NVR (another room)

Here’s the weird bit - Had the projector on all day yesterday (World Cup) and the washing machine running in the afternoon. No issues with anything tripping.

I wake up to the dog barking at midnight and see I have no WiFi so instantly know that the RCD has tripped as the router is off. I check my CCTV and it stops recording at 11:30 when we were all tucked up in bed.

What’s tripped:
63A RCD in hallway (that feeds extension) = Tripped
20A RCD in extension = Tripped

I flick up the 63A and then the 20A (I get a small spark when I flick this back the the On position) and all is resolved.

What have I changed recently:
The only thing I’ve added in the last few months is a NAP 250 DR. This trippped the RCD the first time I plugged it in but now it seams to be OK when powering up.


  • Do I need to change the RCD to a “Type C”?
  • Anything else ?

I would look at your fridge and washing machine as being potential culprits. I had a problem with a fridge that tripped the RCD. This was earth leakage. Powering the 250DR on and off will do it too. But if it has been left on it’s unlikely to be this. It’s a case of systematically checking each appliance and running it on an extension leas to another circuit in the house. Start with fridge and see what happens.


A Type C is probably not the answer in this case as if it trips when everything is already up & running it indicates it might be something with a earth leak.
You do have a lot of devices on the circuit, finding the culprit might prove frustrating, careful examination of each plug & socket, then reconnecting one at a time might find it.

A Type C breaker will help to prevent inrush current from big Naim transformers from tripping it when you switch them on. However, if your existing breaker is tripping there is a reason for that, and you should identify the fault and fix it rather than start using a breaker that won’t trip.
The easiest way to identify a rogue device is to switch all of them off, and gradually turn them back on until the breaker starts tripping again, although that might take a while with your long list of appliances.

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washing machine in our case

I will guess thats its the Fridge… :thinking:

Its (IMO…) something thats ‘on’ all the time - and ‘runs’ intermittently… Like a Fridge does.

Just a guess…


Are you switching off the 250 at the end of the day. I use to switch off the 250 to save electricity. But after a while the RCD would trip. Later the 250 started blowing fuses. It was sent back to Naim who said there was nothing wrong. I decided to keep it permanently switched on as I didn’t want to risk the tripping or blowing the fuses. It was suggested my old consumer unit might be to blame by other members on this forum but my dealer wasn’t of this opinion.

Hey, just don’t let it get onto the acid man!

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I’m surprised no one’s blamed the non-naim power supply… :wink: (my money’s on the fridge too… )


Hi @gav_sw20, if after following all the sensible suggestions above you don’t identify the culprit and the mains keeps tripping, I reckon it’s time to call in an electrician.

A few years ago I’d been away for a couple of weeks and arrived back late at night (plane delayed and taxi long gone) with a companion who was staying the night. On opening the door, we were greeted with a horrible smell of rotting fish. It turned out the mains had tripped and the freezer had been off for several days. This had never happened before, so I called in a sparky who tried a few things but ultimately recommended a new consumer unit and improved earth. Not cheap, but since then no more trips (look’s around for wood to touch).


That sounds a bit drastic, and expensive. I’d get a second opinion on it. More likely something tripping it , fridges are known culprits.
Try un
Plugging everything and then plugging back in one at a time

This could well be a symptom of a fault that has developed in your wiring/consumer unit.

Get your wiring checked & tested by a qualified electrician as soon as possible.

Asking random posters on a hifi forum is not the safe way forward!

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Earth leakage is cumulative and adds up as you plug in more appliances. I agree with others here that appliances which handle water are the usual culprits although in a commercial environment computers and their switch mode supplies can give rise to earth fault issues too. As I say, some appliances do have small earth leakage (I’ve measured lots) and others none, if you have several appliances which have ‘small’ earth leakage on a single RCD protected circuit at the same time it can add up and trip the RCD.

It can be difficult to identify the biggest offenders without taking measurements. Good practice is to reduce the number of appliances on one circuit.

As Simon says, It could also be a fault on the house circuit which may require professional attention.

Earth leakage protection can be very sensitive, that’s the way it’s designed for safety. You’ve got a lot of kit on the single feed, with several PSs and the white-goods appliances, which as @Roog and others have said, can create a build-up. FYI, I had a 555PS which, inexplicably, went off a couple of times and tripped the dedicated circuit. I’ve also had light bulbs blow which have tripped the lighting circuit.

Diagnosing issues is a step-by-step process, as it could be one of so many things.

If you feel OK with DIY then, with the power off, you can check your sockets as a starting point e.g. make sure everything is dry and the respective cables are properly dressed. Alternatively, you can unplug items as a process of elimination and see whether the tripping continues.

My focus (perhaps obvious) would be on the things which are left switched on overnight, starting with the fridge.

I concur with all that has been said, and add that I have had RCD’s blow due to a faulty Oven, and a Toaster when the damp bread touched the element.

Be aware also that RCD’s are supposed to be tested regularly, and yours could be faulty. An electrician will test it more precisely than you can by pressing the test button on the RCD

For us it was the dishwasher, but took a while to figure out that it was the guilty party, but as stated above you can also have death by a thousand cuts where lots of small leakages add up to enough to trip the ring.

GFCIs (RCDs) do wear out. Unusual but not unheard of if the house was new and the breaker is only 5 years old. But if you aren’t the first owner of the house, it could be much older. In any event, that would be my first port of call - replace it ( with a like unit). If that cures the problem, great; if it doesn’t then you need to get an electrician in to figure out why/what’s tripping the breaker.


New consumer units in the UK are now to be fitted with type A RCD’s to over come the earth leakage from our ever expanding digital appliances etc.

In fact any electrician working on your home circuits has to replace a none type A RCD for a type A.

This would be a good place to start and not that expensive, as long as you can get a matching device.

Good luck.

This was several years ago; it’s all sorted now. My point was that if the mains regularly trips, that’s the time to get a professional in.


I had a very odd RCD tripping issue, one of the socket ring circuits would trip on earth leakage at roughly the same time each evening. It took a while, but I traced the earth leakage to our old plasma TV.

So it took it out of service, I had just set our ‘spare’ TV from the dining room to tune its self when I thought I would test the plasma TV cable on its own. At first nothing, then over the period of 45 minutes the leakage increased to the point when the RCD would trip! I was able to measure the leakage current increasing, slowly at first but at around the 45 min mark it would increase rapidly, Absolutely nuts. The cable earth leakage was increasing with time once energised. So I replaced the cable to the plasma and all was good again.

I still have the old cable, it has no obvious physical damage. I must get around to testing it some time. In all of my years as an electrical/ electronics engineer I have never seem a cable go fault ly in this manner.