On 16 Nov 2005 01:38:00 -0800, Ben wrote:

So we had a competent (I believe) electrician round, got out his
megger, tested the kitchen sockets circuit L-E and N-E and found no low
resistances at all. Having found nothing he then tested all the other
circuits and again found nothing.

(Bear in mind that the RCD only tripped, every 4-8 hours, when the
kitchen sockets were on)

He then tested the RCD and found that it was tripping at 20mA not 30mA
(although from comments I've seen in this forum I think I'm right in
saying that an 'in-spec' 30mA RCD could trip anywhere between 15 and
30mA?).

Given we wanted the CU replaced with a split load unit anyway I got him
to do that putting just the sockets circuit and kitchen sockets circuit
on the RCD side. That was 2 days ago... since then, so far (fingers
crossed), we've had no trips at all! The test certificate indicated
that all circuits were OK.

So great minds out there... what could have been causing the original
problem? Can a CU or MCB become 'faulty' in such away as to cause such
a problem?

All very confusing....

Ben

In my house I had orecisely teh same problem. Never tracked it down to
anything partucular - just general leakage from many items of electronics
plugged in seemed to be enough to set the trip 'on the edge' and then
almost any surge would take it over.

Now equipped with 100mA RCD overall..mmust split the bus sometime...and
put 30mA on teh critical bits.

However its still sensitive enough to pop under various faults - had a
leaky kettle..two in fact. Now down to zero electric kettles from three
originally. All showed a minor leak to reath from the elements. All now
binned.