Combi-microwave issue

alfa_aficionado · 03-10-2023 7:05pm #1

Usually just use the microwave function but thought I’d try out the combination microwave + convection oven setting this evening to do some jacket potatoes.

Anyway the issue is that the main house RCD at the consumer unit tripped twice, both times after it had been running for maybe 5min or so. I’m at a loss to explain why this happened? There was nothing else substantial on in the house (base load is 4-600W) & I don’t understand why the main RCD went rather than the MCB that covered the location of the microwave.

Any ideas?

10-10-20 · 03-10-2023 9:41pm

Hi. It might be a cumulative leakage rather than a jacket-potato-induced-fault and the microwave is pushing the RCD over the limit.

Drop the majority of MCB breakers in the house and stick a jacket potato back in as you did and see it it repeats. If it does, you might have a faulty combi; probably a steam/moisture issue (would make sense at 5mins of cooking).

Dave_D_Rave · 03-10-2023 9:53pm

Fault is earth leakage most likely.

The RCD supplies the downstream MCB's. Therefore is there is a earth leakage fault downstream then the RCD will trip regardless of which circuit it is on.

MCBs typical focus on thermal and magnetic faults and in the event of a fault of this type then the MCB would operate.

Chances are your element has broken down and failed and there is a link between a phase conductor and earth.

If you handy you can get a replacement element online for most models

alfa_aficionado · 04-10-2023 8:29pm

Thanks - I’ll have to Google that explanation!

I've also noticed on our other microwave (built-in and on a different MCB) that every so often it seems to stop for a fraction of a second before carrying on. It might do this several times over the course of a few minutes (or other times it seems not to happen at all).

Is this a similar issue or something else entirely?

Combi-microwave issue

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