Possible MCB problem.

May 24, 2014
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We are having some minor issues on site. When using the microwave, sometimes on its own and sometimes in conjunction with the electric hob, the MCB is tripping. There are no other electrical items that we can see connected to that part of the electrical system.

Today, I have unplugged both and using an extension connected both to the sockets on the other side of the caravan and using a different MCB. That MCB doesnt trip.

How likely is it that we have an MCB thats a bit oversensitive. Would you start by changing the MCB or look for something else. How do you go about testing an MCB.

This caravan had a full electrical inspection after the water ingress last month and has its certificate. Not that I would trust that dealership as far as i could throw them.


May 23, 2021
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Is the MCB rating close to the appliance load? From what you said, it seems the MCB is at fault (or the connection of it). Try disconnecting the electric and checking the connection of the MCB before swapping the MCB's if they are same rating.


Mar 14, 2005
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If your MCB's are F&S, then they are well known as cheap chinese items and are very unreliable.
Hager are the best around .

With regard to the electrical inspection, did you get a copy of the results including the trip times of the MCB's?
Also a reading of the resistance of the insulation?

If none of those things the a "full electrical test " has not been done, just a simple visual inspection and trying the various electrical items individually (possibly).

The thing to remember is that on start up the microwave briefly uses twice its rated power and that with an electric hotplate running that in itself would trip the MCB most likely.
May 24, 2014
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Thanks Damian. The mcbs are Sargent fitted Conectum I think. Priced around 2 quid each so I fully get where you are coming from, cheap and nasties.

I do have all the results and times but not with me.

On our van, the Ec600 is fitted low down in a floor cupboard and very difficult to access without withdrawing the whole unit. We can certainly manage until we get home and at that juncture we have decided to change the caravan anyway.

Had access been easier I would have gone and bought three quality mcbs and replaced them all. Its not dropping the RCD so as you say, its probably a bit oversensitive.
Mar 27, 2011
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Hi Thingy, it sounds to me as though you’ve reached a point with the current van that you’ve simply decided to start again from scratch, I can understand totally how you feel, our previous van was a bailey ranger with a fixed bed which just became an annoyance having to climb over each other and we had reached a point after a two week trip where it was time to change, we talked about what we wanted and compiled a short list of what a replacement had to have, we got home on the Saturday and within a couple of hours it was on eBay and sold within 24 hours, best decision we’ve made and I hope your as pleased with your replacement as we are, when we made our short list of what we wanted it made things easier because we only had to look at the vans with the right spec, is there a lingering nagging of things likely to go wrong due to the endless problems you experienced until recently, I wouldn’t be at surprised if there were doubts, good luck what ever you decide.



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