First of all, it's ultimately possible that I've done something excessively
stupid to cause my problems (I say this so that no-one will rule out any of
the obvious suggestions).

I've just started rewiring my house today, I've ran a new set of tails to
my new consumer unit, and have another set of tails to my old consumer unit.
The new consumer unit is split load.

Just to test things out, I've wired a single socket to the new CU on the RCD
protected side.
If I plug anything what so ever into the socket I've wired in then the RCD
trips the moment the item is turned on.

I also had another consumer unit with RCD which I was going to use to
protect the external sockets. So I removed the RCD from that and used it to
replace the RCD in the installed consumer unit. The RCD's are exactly the
same model number. I get exactly the same response, immediate trip when a
device asks for power.

I rewired the socket over to the non RCD side of the consumer unit and it
works fine.

The socket is wired as a direct spur straight from the RCD rather than as a
loop (it's only for testing).

The consumer unit and the RCDs are Contactum.

Can anyone make any suggestions? I'm highly doubtful that I've been given
two duff RCDs but I can't think of anything else...

Help! Please?

Thanks

Seri