Heavy heavy rain trips fuse (but not shed fuse or shed sub-board)

pdpdpdpd

Strange scenario and looking for some ideas....

During heavy rain (and only really heavy rain) when the ground gets really sodden the main fuse (No. 8) in the main board serving all the house sockets trips.

The only way to reset is to trip all fuses on the bottom row (1 to 8, 20 and 21), leave the one serving the shed (No. 20) down, and then bring all the others back up.

The small sub-board in the shed itself never trips and the fuse serving the shed (No.20) never trips by itself.

Few days later when the ground has dried out can set the trip again and all is fine until the next time.

I figure it's something to do with the cable to the shed in the really really wet ground but don't understand why it trips No.8 instead of No.20 first.

Any help greatly appreciated.....

Lenar3556

That is all consistent with leakage, brought about by water ingress to some wiring/fitting/junction box likely in the shed based on your description.

No. 8 isn’t a main fuse, it’s an RCD which monitors for leakage on any circuit which it monitors. They are quite sensitive.

It it most likely the issue lies on the circuit supplying the shed - So check for any point where water has/can come into contact with anything electrical there. Outside lights, sockets, junction boxes etc. the cable itself wouldn’t be particularly likely, but a possibility if all else seems ok.

Any decent electrical contractor will be able to diagnose the cause quite easily, if you don’t see anything obvious.

con747

https://www.boards.ie/discussion/2058338853/heavy-heavy-rain-trips-fuse-but-not-shed-fuse-or-shed-sub-board

Looks like you have a solar system? If so I have seen similar issues in the one of the renewable threads where things short during heavy rain. Maybe post there as well. I'm not sure if this is the thread I seen it in but worth a post. https://www.boards.ie/discussion/2058101518/solar-pv-hints-tips-troubleshooting#latest This might be the thread I remember. https://www.boards.ie/discussion/2058222496/solar-for-dummies/p62

PM @micks_address address and see if his issue was the same.

10-10-20

https://www.boards.ie/discussion/comment/121847172#Comment_121847172

If it's happening at night at all then it's not the solar capacitance issue. Plus it normally trips out the solar RCD (probably 21 on that board). It could be cumulative leakage with the new solar adding to what was a marginal condition though too.

pdpdpdpd

https://www.boards.ie/discussion/comment/121847122#Comment_121847122

Thanks Lenar,

Quick follow up....

From the fuseboard in the house to the shed is a straight run to a small sub board in the shed. This sub board never trips.

Does this indicate that it's most likely something with the cable running to the shed?

Or could it still be something in the shed on the far side of the sub bord? (e.g. ingress to fitting etc?)

Could the RCD in the house trip but the sub-board in shed not?

pdpdpdpd

https://www.boards.ie/discussion/comment/121847172#Comment_121847172

Thansk Con747

Has been happening for a couple of years - well before solar went in - and has happened at night.

Just took us a while to narrow it down to definitly heavy rain and defintily the shed.

Lenar3556

https://www.boards.ie/discussion/comment/121850110#Comment_121850110

No, it could be anywhere between the house board and any of the circuits in the shed. What is tripping isn’t an overcurrent device like a fuse, it’s designed to detect leakage and is very sensitive.

There would be better ways of designing the circuit protection if it were a new install being carried out today.

smuggler.ie

Could it be potential damage to cabling(insulation) on internal shed distribution(rodents) or condensation build up in the electrical boxes in the shed or both in combination

pdpdpdpd

Thanks everyone

Will keep searching. Bit of a spaghetti out there over the years.

Anyone know a good electrician in the Swords area who likes a challenge? :-)