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I had a power cut this morning. After a lot of experimentation, it seems to be related to the washing machine.

The thing that confuses me is that when we power the washing machine the master circuit breaker in the consumer unit trips. It then refuses to reset. I have every plug I can find in the house disconnected, and every switch turned off. It still refuses to reset.

It seems like after enough banging my head against a wall, and slowly trying to reset the master circuit breaker, it'll give in. It takes a while though, and I have no idea why it eventually gives in, and even whether it will in the future.

Does this suggest that the master circuit breaker switch in the consumer unit needs replacing? Or perhaps there's some leakage between earth and live and it just takes some time for that to 'drain' out of the system?? I'm obviously guessing here!!

I can't exactly try many experiments with the washing machine as when it dies it's a pain to get power back.

I tried changing the fuse in the washing machine plug just in case. That made no difference. Surely that fuse should have blown first? I also tried adding in an rcd between the washing machine and the plug socket - that also didn't help and the main fuse went. Why could that be?

Any advice or suggestions really appreciated. I have an electrician booked in but the next available date is a few days away - and I'd also like to understand the issue a bit too!

Many thanks, Dave.

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    I think this question could be clearer if you distinguish between a fuse (needs to be replaced when blown) and a circuit breaker (like a switch, can be reset when tripped). Also it is not clear to me what you mean by saying the master fuse "gives in". Do you mean it resets? May 2 at 15:25
  • Thanks. I appreciate the suggestion. I've tried to make it clearer. It's the circuit breaker. Even with all the individual ones turned off, the master one refuses to reset. Eventually, if I keep trying, and if I switch it slowly, the it turns on.
    – DaveS
    May 2 at 15:30
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    I take it your 'master circuit breaker" is your main RCD in your consumer unit? Or does it have an overcurrent trip as well/instead? May 2 at 15:31
  • Yeah, I think so. Sorry for my lack of understanding of the correct terminology!
    – DaveS
    May 2 at 15:33
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    Are you moving it to off position first before resetting? Most trips do not go to full off, and need to move to off before resetting.
    – crip659
    May 2 at 15:34
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As a follow-up, there were a couple of issues:

  1. The RCD was broken. It was tripping correctly, but it should have been able to be reset. This has been replaced and now works as expected (and as an aside, I'll soon be replacing the whole CU).

  2. The washing machine was defective. Once the RCD was fixed I was able to perform some tests. The heating element had failed. Disconnected it stopped it tripping the RCD. I've installed a new heating element and it now works perfectly.

Thanks for everyone's help & suggestions.

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If the washing machine caused high-enough current load to cause the master circuit breaker to toggle off, which takes 50 or more amperes, you'd certainly see a bright flash at the plug when plugging in the washer, and the tip of the plug would look burned or melted.

More likely, the master circuit breaker is also a Ground Fault Circuit Interrupter (GFCI), which is designed to prevent shock hazard as well as to prevent current overload. If that is the case, the GFCI triggers because there is electrical leakage within the clothes washer. If the motor or circuitry became wet, for example, electricity could leak from the hot wire to ground... or worse, through your body to ground.

Make sure there are no water leaks in the washer, and try drying it with a fan for a day or two before testing it on a cycle (empty, so you're not stuck with half-washed, soapy clothes). If that doesn't resolve the issue, the washer needs repairs.

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  • IIUC, GFCI in the US is an RCD in the UK*, so the 2nd paragraph is likely the culprit. * I believe that there are some technical differences between them, but that functionally, they're the same.
    – FreeMan
    May 3 at 12:30
  • Ah, like hood and bonnet, boot and trunk. To quote MFL, "One common language I'm afraid we'll never get." Of course, the UK needs the devices even more, since mains are usually 220 VAC, rather than North American 110 VAC. May 3 at 16:18
  • Thanks. I'm still confused about why I can't reset the rcd after it trips. I think you're right that it's due to leakage - there's no accompanying bang like I've experienced when other things have failed in the past and tripped it (like a heater element in the oven). It really feels like the switch is failing to catch when I try to turn it on. Obviously it could also be re tripping again. There's no obvious fixed time after I've disconnected everything that it takes to recover and allow me to turn it on. The best success I've had is turning on on super slowly a lot of times.
    – DaveS
    May 4 at 6:50
  • Are you saying that you can't reset the breaker even with the washer unplugged, or just that the breaker is difficult to reset? A GFCI/RCD may trigger on current surge, and if there are inductive devices (e.g., motors, fluorescent lamp ballasts) on, the very act of trying to reset the breaker causes it to trip again. If that is the issue, shut other appliances and older fluorescent lights before resetting the breaker. May 4 at 17:24
  • Yes - I can't reset the breaker even with the washing machine unplugged. I also can't reset it with every plug in my house disconnected, and all light off (I think). Eventually, if I try enough times it seems to switch. It takes a lot of goes though and generally an hour or so of waiting & then retrying. It seemed to switch best when I switched it really slowly, but that could be a coincidence. I've not dared to trip it after the first 3 or so because I'm worried I won't be able to get power back if the RCD is defective.
    – DaveS
    May 4 at 20:17

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