Beyond me !

[Jimtelford]

I’m 75 and am not an electrician although I’m pretty handy and attended a CnG Domestic Wiring course 30 years ago. If friends or relatives have electrical problems I have always been able to source the problems and rectify them.
HOWEVER, I AM OUT OF MY DEPTH with this problem.

Garage about 5m from bungalow, power directly fed by 4mm, 3 core SWA from a 32A trip. Mini DB in garage serves lights (6A) and a few sockets (32A).

The 32A feed in the bungalow is continually tripping and also trips the main RCD.

I disconnected the garage DB completely so no connections at all in there, but the 32A feed trip in the main DB still blows.

The installation in the main DB looks sound and there shouldn’t be any rodent problem as it has SWA.

It appears to be worse in colder weather.

Any ideas please ?

 

[littlespark]

The cable needs tested between house and DB.

you disconnected the garage db from the cable, but not the cable from the house db? is that right?

Moisture can still get into SWA, and maybe its damaged through spade work, or even just stones settling in the ground. The trench was buried in should be bedded with sand.

Remember, RCD's will trip with a fault between neutral and earth as well as live and earth..... if the 32A mcb is switched off, the neutral of the cable is still connected and can trip the rcd.

 

[mainline]

I’m 75 and am not an electrician although I’m pretty handy and attended a CnG Domestic Wiring course 30 years ago. If friends or relatives have electrical problems I have always been able to source the problems and rectify them.
HOWEVER, I AM OUT OF MY DEPTH with this problem.

Garage about 5m from bungalow, power directly fed by 4mm, 3 core SWA from a 32A trip. Mini DB in garage serves lights (6A) and a few sockets (32A).

The 32A feed in the bungalow is continually tripping and also trips the main RCD.

I disconnected the garage DB completely so no connections at all in there, but the 32A feed trip in the main DB still blows.

The installation in the main DB looks sound and there shouldn’t be any rodent problem as it has SWA.

It appears to be worse in colder weather.

Any ideas please ?

You need some test equipment to be able to do an Insulation resistance test on the cable that feeds the garage.

 

[James]

looks like you may have a damaged cable.
can you measure the resistance between the 3 cores?

 

[Jimtelford]

The cable needs tested between house and DB.

you disconnected the garage db from the cable, but not the cable from the house db? is that right?

Moisture can still get into SWA, and maybe its damaged through spade work, or even just stones settling in the ground. The trench was buried in should be bedded with sand.

Remember, RCD's will trip with a fault between neutral and earth as well as live and earth..... if the 32A mcb is switched off, the neutral of the cable is still connected and can trip the rcd.

Thanks for that.
Yes, that’s right.
I hear what you’re saying, I suppose I considered the cable bullet proof as it hasn’t been touched in 10 years that we know of, and there’s been no problems with it.

 

[Jimtelford]

You need some test equipment to be able to do an Insulation resistance test on the cable that feeds the garage.

Looks like a job for the heavy brigade

 

[snowhead]

SWA can get damaged during / after installation or may have already been damaged before installation where the outer sheath gets cut.
This isn't a problem to start with but as the steel armour corrodes within the outer it can put pressure on the inner cores and break through the insulation.
All you need then is some moisture and you have a fault.