On 06/08/2013 09:58, 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!

Could be anything, but my first thought would be to check anything with
a heating element.

Over the years we've had it with the cooker, washing machine, dishwasher
and iron, but nothing else.

If your fridge/freezer is a frost free one, it'll have a heater too.

SteveW