Rcd tripping with just a wire

[ChloeRadshaw1]

Please bear with me because I am confused about what I am seeing. I have a 10mm cable running from main cu protected by 80amp rcd. The man is 40 amp

the 10mm cable runs to another consumer unit feeding the garden outhouse

since yesterday the rcd trips and it is the b40 mcb that is causing the tripping

I have removed the connection to the garden outhouse so you have a single 10mm cable buried underground running to the garden outhouse and it still trips even with no load and it not plugged into the garden consumer unit

sparky came and couldn’t understand it either. Suggests we run a new 10mm cable which is a good 15 metre length which I am not happy to do

the garden cu does have mba as well but no rcd

any pointers much appreciated

 

[Adam_151]

sparky came and couldn’t understand it either. Suggests we run a new 10mm cable which is a good 15 metre length which I am not happy to do

What were the insulation resistance readings for the cable with the downstream board isolated?

 

[ChloeRadshaw1]

The spaky came and replaced the mcb and even the rcd which did not change anything. I don’t have the readings to hand and I don’t even think he took any voltage readings.

 

[EFLImpudence]

I suggest you need an electrician who knows what he is doing.

Equivalent to you taking the car to a garage because a warning light is on and idiot changing the bulb.

 

[CBW]

I’m no sparky, but sounds like you have a short circuit/dead short.

 

[Harry Bloomfield]

Sounds like a fault in the 10mm or water has maybe entered the 10mm cable somewhere. Best get a genuine electrician who's actually knows what they are doing, to do an insulation resistance test. It's nothing to do with measuring voltage.