BG RCBO ramp test on one of them shows trip at 15ma every other one is 24 ma

[The Ghost]

So just did an EICR few problems mostly rectified. Customer wanted new CU so put in BG with RCBO just five circuits. Tests on EICR were fine except for high ohms on Zs for lighting first floor so tracking that down. All RCBO are fine except this one 32a ring final circuit. RFC tests all fine IR around 400 + Mohms. 10ma leakage with clamp on tails. So it was the end of a long day. Said I will replace the 32 rfc RCBO.
What really made me wonder is when the downstairs ring is used i.e. kettle on, the upstairs ring trips. I just can't right now formulate an approach to it. And I do seem to remember BG RCBO being quite often defective, is that true in your experience. My first thoughts were that there is some cross connection between the RFC, not that I picked that up on testing. Now I can assure you that I have not mixed up the RFC neutrals I triple wipple checked on that.

 

[The Ghost]

OK went back and sorted it. Managed to get it down to middle room spurred socket opened it up and neutral and earth connected incorrectly. Owner had installed a couple of sockets. Didn't take long at all. Thought I would be under the floorboards all day. Phew!

 

[marconi]

So Richard Burns was spot on - an N-E fault as a result of N and E reversal at a spurred socket, which was switched on (dp switch?) or switched on or off(sp switch)on the up FRC with an appliance plugged in to it using L,N and cpc?

 

[The Ghost]

In fairness to @telectrix as @Richard Burns acknowledged Tel got it. And Richard illustrated it. But otherwise that is about the size of it @marconi

 

[telectrix]

the important thing is always the result. ( as Croatia said after the semi-final).