URGENT: Anything else to try before calling out an electrician?

[Sprogginz]

while the garage CU is OFF

as a Fusebox, I suspect the main switch is a Double pole and so isolates the Neutral and Live connections from the House CU and the garage , which means at least the cable to the garage should be OK

its worth removing the front cover and see if damp or if full of water
of course overtime , they may simply dry out and so ALL will work OK again, until next rainfull

Yes, if it is water damage but it starts working again, I'm hoping the culprit will leave some evidence to suggest water was once there such as some residue of some sort.

Thanks again.

 

[Harry Bloomfield]

Yes, if it is water damage but it starts working again, I'm hoping the culprit will leave some evidence to suggest water was once there such as some residue of some sort.

Thanks again.

All you can do, is isolate the power, and before it might dry itself out - open up and check any likely suspects for any remaining water.

 

[FrodoOne]

As John Ward mentioned in the Video referenced in Post #9, (from 2:40 to 3:35) :-
The major disadvantage of having RCDs "protecting" multiple MCBs is that,
when the RCD "trips",
one does not know which MCB (protected) circuit caused this !

"Now-a Days", the cost differential of having
RCBOs protecting ALL circuits,
- as compared to having
a few RCDs "protecting" (the users of) multiple MCB protected circuits -
is so small
(compared to the "labor" of figuring out what has gone wrong)
that using all RCBOs is actually more "economic"
than using RCDs, in combination with MCBs.

(It also "frees up space" on the CU.)

 

[Mottie]

Firstly, that MK B20 MCB on the left that davelx pointed out, I don't know what it does but is it possible that it could be connected to the fuse box in my garage? I totally forgot about it! I've just gone into the garage, switched that fuse box off and now the RCD stays up.

It has been raining a lot as davelx also pointed out so I think there might be a leak somewhere that perhaps has gone into a socket. Would that explain it? Can't check properly yet as I've temporarily crammed so much crap in there.

Thanks again and apologies in advance for my brain.

Had something similar in a rented cottage a few months ago.

Been piddling about with the electrics in the rental cottage. A breaker that controls one half of the consumer unit keeps popping. It controls 4 other breakers - cooker, downstairs lights, kitchen lights and 'garage fuse box'. (No garage but actually a car port). I managed to deduce it was the garage fuse box that was causing it to pop after about 5 minutes so left that off. Notified the owner because it controls 2 chest freezers in the car port that are full of food - both human and frozen raw dog food for his dogs. Luckily it’s cold here at the moment but he'll need to look at it pretty quick. Question for the sparkys on here - why isn’t the garage breaker popping but the main one is?

 

[Ragnar_AT]

usually an MCB does not need to be ON to find an earth fault, hence why it was tripping even with those OFF previously

That‘s not entirely correct. An earth fault can be L - E or N - E. An L-E fault is disconnected if you switch the MCB off or pull the fuse, an N-E fault isn‘t because the MCB doesn‘t disconnect the neutral.