In article ,
Lobster wrote:
Currently being driven nuts by the above... I have a split load CU. When
the RCD trips, it's only that which goes; ie none of the MCBs trips at
the same time which means there's not much for me to go on.

Question 1: if, for diagnostic purposes, I switch off each circuit in
turn by manually flipping its MCB, does that actually isolate the
circuits for the purpose of elimination? Or would I need to open the CU
and physically disconnect all the cables from each circuit in turn,
completely?

Question 2: what does the fact that no MCBs are tripping; and the trips
occur at apparently random intervals (4-5 times in the last day, with
interval of up to ~10 hours so far, and including an overnight trip; and
no problem with reinstating the RCD immediately) tell me about the
nature of the fault, if anything?

Thanks for any pointers!

The MCB will only trip on current overload. The RCD trip indicates a leak
to earth somewhere. This is frequently on things that have heating
elements, but they'd probably need to be switched on for the trip to occur.

But it could be water getting into a junction box somewhere. Do you have
any outdoor supplies?

--
From KT24

Using a RISC OS computer running v5.18