Garden cabin tripping fuse in house

Del007

We recently got a cabin built out in the garden. The cabin itself has a fuse board inside which is connected to my fuse board in my house.

It has tripped the cabin's fuse in the house fuse board a number of times. It has been raining all of these times.

None of the mcb's in the cabin have ever tripped.

I had the electrician out today who thinks that there could be a problem with moisture getting in contact with the lights.

Shouldn't the mcb's in the cabin trip before the fuse in the house trips?

Thanks for your help/advise

kirk.

New electrician

Sorry but I mean cabins are not complicated

Probably some cockup in the wiring or wired it off the main RCD

Either way get someone else

kirk.

Your last point ya the cabin should trip first not the house

Electrical ABCs:

1) You don't create an unnecessary hazard or nuisance

2) Connect swa to an MCB or fuse if that's whats even supplying the cabin

meercat

https://www.boards.ie/discussion/2058251222/garden-cabin-tripping-fuse-in-house

If the cabin is wired correctly then The problem most likely is on the cable between the house distribution board and the cabin distribution board or perhaps the tripswitch is overloaded. Is the tripswitch in the house distribution board a rcbo(post photos)Either way it should be a simple diagnosis from a competent rec with the right equipment.

Del007

The cabin is def not overloaded. It has 6 downlights and all that's plugged in is an Amazon speaker/ a modem and a heater.

It has tripped when no lights were turned on, would this eliminate the lights?

The cabin is wired with a 4sq swa cable.

asdfg87

https://www.boards.ie/discussion/2058251222/garden-cabin-tripping-fuse-in-house

I expect its moisture getting in the cable thats feeding the shed, the trip will work back from the problem.

What type of cable is going from house to shed?

Del007

It's a 4sq swa

Bass Reeves

https://www.boards.ie/discussion/comment/119233459#Comment_119233459

Is there a joint on the SWA between the house and the cabin. This may have happened where the SWA was previously put in for outside services

b318isp

Get a REC to megger the feed cable to the shed. This will check the supply cable for damage or water ingress.

Del007

https://www.boards.ie/discussion/comment/119233465#Comment_119233465

It's a new cable that was put in, there's no breaks in the cable

Del007

https://www.boards.ie/discussion/comment/119233469#Comment_119233469

The electrician was out yesterday, I'm not sure why he didn't do this.

He seems adamant that the problems are with the lights, he did say that some of them had signs of corrosion on the cables and fittings themselves.

I still don't understand why the MCB in the cabin wouldn't trip first if this was the case. It happened at night time when there were no lights on.

Bass Reeves

I presume he put an new earth bar in for the shed??

Del007

https://www.boards.ie/discussion/comment/119233537#Comment_119233537

I really don't know if he did or not

meercat

https://www.boards.ie/discussion/comment/119233537#Comment_119233537

It’s not a requirement or necessary

OP ,did you Get a certificate for the electrical installation to the cabin

Del007

The cabin was build by a separate company. The builders of the cabin also wired the cabin. His electrician wired the fuse board but the workers did the terminations in the sockets and lights

I got my own electrician to run a cable out to the cabin. He is a qualified electrician. He also did tests on the cabin as he said that he wouldn't sign it off otherwise. He then gave me a cert for it. He did mention something about the lights but I'll have to have a look at the cert to see what it says

Del007

It says on the cert that there are no junction boxes for the connections at the downlights and that they are to be installed at a later date

kirk.

Have u got a pic of the board in the cabin

Del007

These have never tripped

b318isp

https://www.boards.ie/discussion/comment/119233502#Comment_119233502

He may be not wanting to deal with a damaged underground cable!

I agree that the cabin 10A MCB should be tripping before a 32A MCB in your main board if the lights were defective, assuming the "Shed" MCB is not fed by the house RCD (note that recent ET10101 wiring regs changes require RCD protection on light circuits for installs since ~2020).

Del007

The SWA cable is in a conduit running along the wall, there's no way it could be damaged

meercat

https://www.boards.ie/discussion/comment/119234267#Comment_119234267

No rcd protection light circuits

no surge protection (or documentation it’s not required)

no double pole isolation distribution board

surprised anyone certified that

smuggler.ie

Would it be normal to have 80A rated "main isolator" in the cabin vs 32A rated breaker on main fuse board as per images posted above?

Del007

https://www.boards.ie/discussion/comment/119234797#Comment_119234797

Where does this leave me now? Not sure what to do now

Del007

https://www.boards.ie/discussion/comment/119234862#Comment_119234862

I'm also confused by this, shouldn't the breaker in the cabin be less than the breaker in the house?

Tow

https://www.boards.ie/discussion/comment/119234862#Comment_119234862

The Mains Isolator is a switch, not MCB. Would it be possible for 'neighbours' to plug anything into the outside sockets?

The next easiest step is to switch off circuits in the shed to try and isolate circuit the issue is on. Or get electrician to megger them... It is hard to see the 10amp lighting circuit tripping the 32amp Mcb in the house and it's own MCB not tripping.

Del007

My neighbour is an 82 year old woman, I doubt it :)

It seems to have been raining everytime that it has tripped, I can't be 100% certain as it tripped a few times over night. In total it has happened 6 or 7 times

zg3409

The electrician needs to diagnose and fix the issue.

I would not try a DIY diagnosis.

It could be a faulty breaker, it could be damaged cabling (even in a conduit or with no visible damage on cable. It could be water getting in lights.

Really someone needs to use the proper tools to check the issue. Any suspect breakers should be replaced to rule them out. Don't try this yourself as there is various breaker types and you seem unsure. I have seen all sorts of weird issues, but a different, good electrician should at least be able to swap out the basics and maybe isolate the lights if suspect and use a table lamp for a while. There are tools for testing the parts.

Bruthal.

Possible faulty breaker in house, or a fault on the cable, which can be anywhere on the cable, but usually at or close to terminations at either end (house or shed boards, JBS etc), or a fault in the shed board itself.

All asuming the lights etc in the shed are properly wired to appropriate breakers.

meercat

https://www.boards.ie/discussion/comment/119234921#Comment_119234921

Get the rec that certified it to come back,put everything right and recertify it. Also ask for a copy of the test records.

kirk.

https://www.boards.ie/discussion/comment/119235912#Comment_119235912

I would assume it's on the supply side

I wouldn't rule anything out at the cabin either

Bruthal.

https://www.boards.ie/discussion/comment/119236415#Comment_119236415

A safe assumption assuming its correctly wired. Parts of the shed DB will be on the supply side. Ye never know what has been done. Water into lights as a diagnosis seems a little bit like guesswork anyway. But as said, ye never know what anyone has done.