GrahamS wrote:

I replaced an old fuse box with a Consumer Unit before Christmas. A
light (on the non-RCD side) trips the RCD when switched off!? I've
checked for crossed neutrals between the RCD and non-RCD, and checked
the earth resistance of all the cables - all seems OK. There is cable
to a second switch (i.e. 2 way). When it's disconnected, the RCD stops
tripping; but if I connect just the earth back into the primary switch
it starts tripping again. Help!


Earth neutral short somewhere. Disconnect earths one by one and test.