"Jonathan" . wrote in message ...


SNIP





Thanks for the comprehensive reply!

Unfortunately I don't have the facilities to test for earth leakage.
Presumably I use a "megger" to test for that? Can they be bought cheaply?

Yes and reasonably so but if you don't know how to use one correctly it may
damage more than help.

Regarding the two pumps, we have a strange setup: the boiler has two flows
and two returns and you're supposed to just use one pair, however, when
the
boiler was plumbed in (about 20 years ago) they used both pairs, one pump
per pair, and activate one pump for CH and the other for HW, or both for
both CH and HW! I'm still fairly confident it's the boiler, the power
*only*
trips when the boiler is running. Initially I did think it was the CH pump
but since turning off the CH, it still happens, just less often. No CH
thermostat BTW, just the internal boiler one!

You haven't mentioned the hot water pump being a candidate?

Is it possible to get a sort of multiple RCD that I wire the boiler into,
and the pumps and each is monitored and rather than trips, displays a
count?
Would be very useful!

Possibly but I get the impression it might cost more for such a one time use
device than it would cost to get someone in who can find and fix the
problem.
BTW where are you in the country?