Tripping mcb

[richbee]

Not really solar related, but wondering if anyone has helpful suggestions.

Been at my in-laws this afternoon - they had a couple of power outages during & after the storm. After the first one their boiler sprung a leak, then after the 2nd one, one of the mcbs on the consumer unit will not reset. There is only 1 main rcd, which isn't tripped - see photo.


It feeds the boiler and most of the sockets in the older part of the house + the burglar alarm.
I went round & unplugged everything in every room to no avail.
The fuse on the boiler switch is OK, and also the burglar alarm fuse.
I thought I'd hit on something after asking them what they did differently between the 1st & 2nd powercut - to which the answer was - we boiled a kettle in the bedroom - as you do!
So a 3kw kettle plugged in via a fully wound in 10A Extension lead in the bedroom - oops.
I unscrewed the socket but there was nothing obviously wrong (metal back box not earthed, but has obviously always been like that).

They tried unsuccessfully to get a plumber for the boiler and an electrician - hoping for more success tomorrow.

[spread-tee]

When you try to reset the MCB does it make a big "splat" itself and fail to latch? if so obviously you do have a pretty serious short somewhere, if no splat but just fails to latch it might be a knackered MCB itself, fairly rare but not unknown. If you have unplugged and switched off everything it comes down to testing various bits of the circuit to home in on the fault.

Desp

[cojmh]

Just a thought (from a non electrician),

If you turn off the incoming power, then try to turn the MCB on will this show whether the MCB is faulty?

If the MCB fails to stay engaged it would indicate that the MCB is faulty as there is no power to be tripping it?

If the MCB engages then it would indicate that there is an electrical fault somewhere.

Just thinking of ways to try and focus in on where the problem is.

I could be wrong - so perhaps an electrician might have further insights?

Good Luck

[knighty]

Just a thought (from a non electrician),
If you turn off the incoming power, then try to turn the MCB on will this show whether the MCB is faulty?
If the MCB fails to stay engaged it would indicate that the MCB is faulty as there is no power to be tripping it?
If the MCB engages then it would indicate that there is an electrical fault somewhere.

was going to post this but he beat me too it, do this!

[AGT]

If everything was fine before the leak, there must be water stuck in a joint box, accessory , get the heating on/ dehumidifier/ window open and dry the leak area

[ecogeorge]

When you try to reset the MCB does it make a big "splat" itself and fail to latch? if so obviously you do have a pretty serious short somewhere, if no splat but just fails to latch it might be a knackered MCB itself, fairly rare but not unknown. If you have unplugged and switched off everything it comes down to testing various bits of the circuit to home in on the fault.

Desp

With the power off , disconnect the live wire from the mcb .
Reset mcb .
Power on.
If it wont reset then it's an mcb problem.
If it resets its a problem with that circuit.
reconnect wire.
Then .........
Unplug/disconnect (turning sockets off does NOT disconnect appliances unless a DP (double pole socket) -unusual .
Then try again and report back....

[Stinsy]

That board is decades old. Assuming you have removed the possibility of a defective appliance causing the issue by removing everything on that circuit then you either have a defective MCB or defective wiring. TBH, either way, you need a spark to come round a quote for a new all RCBO CU.

[richbee]

Thanks all for the advice and suggestions. I will pass them on - I might have to go back again if they can't get hold of their usual electrician quickly (not surprisingly, was no answer yesterday, and I wouldn't be that surprised if they are rushed off their feet post storm)