"John" wrote in message
...

"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.

That's me out then, I do have a degree in electronic engineering, but they
don't teach this kind of stuff - maybe electrical engineering would have
covered it.



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?

I've been in touch with the pump manufacturers and they were insistent that
the failure mode of the pumps would be different. And the fact that the
problem occurs more when the CH is on would mean both pumps have problems...
which occurring at the same time would be rather unusual.


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?



Near High Wycombe in South Bucks.