A mate of mine has completely rewired our house so everything in the
installation is brand new, including the split-load consumer unit. We have
an upstairs ring main, downstairs ring main and a kitchen ring main, all of
which are protected by the RCD, and the problem is the kitchen ring.

As soon as *anything* (portable radio, halogen lamp, electric drill or
whatever) is plugged into *any* socket on the kitchen ring, the RCD trips
(plugging the same things into either upstairs or downstairs rings does
*not* trip it).

Splitting the ring at the CU and using a proper Megger (500v insulation
resistance tester, not just a multimeter) to test each leg of the ring shows
the following:

L-N = almost infinity resistance (certainly over 1,000Mohms anyway)
L-E = " " " " " "
"
N-E = " " " " " "
"

so no short-circuits, but yet the RCD trips. What's the problem - more
importantly, what's the solution to the problem? )

TIA,

Mogweed