Didn't think was possible

[guest119]

And don't assume there is always just one fault,there may be more or an accumulation.

Boydy

 

[PEG]

Ok, I swung by on way home and sure enough the ze at the origin is 3.5 ohms so all four flats are affected. Have emailed my office saying as a matter of urgency we need to contact the supplier.
I always thought that a rcd looked for an imbalance between neutral and earth,and a mcb took care of overcurrent and short circuit and earth fault, hence being stumped after removing all neutrals from the board and even removing the outgoing neutral from the rcd and the rcd still tripping

Hi Pondy,an RCD does monitor and operate due to an imbalance,but between line and neutral,this may be shootin' up THE earth,or AN earth,but it determines "some",maybe 30 ma's worth is awol,and operates accordingly. The advice concerning the order of tests is sound,and although on occasion skipping some can still bring a quick result,in general it negates back-tracking. Happy hunting.