Apologies in advance for length of post.

As part of our nearly-complete building work, the old fuseboard (as I
still call it) was replaced by an all-singing, all-dancing consumer
unit. Whizzo, I thought, as I recalled our last house where every
time a light bulb blew the consumer unit arranged for the whole house
to be plunged into darkness and a joyous festival of resetting the
blinking 12:00s was on the cards.

The new unit behaves differently, but it does have one very, very
annoying habit. Every so often without any rhyme or reason that I can
tell, part of the thing trips and all the sockets in the house go
dead. The lights are fine, but nothing else. I asked the electrician
to test it, but he simply suggested unplugging things until it stops
happening. Yet more blinking 12:00s to play with.

Fine, except that it might happen four times in one day, and then not
happen again for three days, whereupon it might happen another six
times in three hours.

We recently went away for a week and fretted about this happening ten
minutes after driving away and all the food in the fridge spoiling, so
we unplugged everything and switched everything off except the fridge,
the DVD recorder and one or two other essentials. When we got back
everything was fine, no power outages (as the Merkins have it), and
gradually we plugged things back in and switched things back on as and
when required. And it all seemed fine for a few days, and then
suddenly they all went off again and the whole merry cycle began anew.

The only appliances that are running 24/7 are fridge, cookers (well,
the clocks anyhow), alarm clocks and whatever controls the boiler.
Plenty of other appliances are plugged in, and on at the wall, but not
in use (washing machine, dishwasher, TV (never left on standby) etc.
etc).

I don't have the correct terms for all the bits and bobs of the
consumer unit, but it's divided into two rows of eight trips (what
would, I suppose, have been fuses in the old days, what I think are
now called MCBs) with each row having a master "trip" (an RCD?) and an
over-arching master "trip" (a super RCD?) for the whole shooting
match.

It's the lower master "trip" that trips - the one controlling the
second row of individual trips. These trips are labelled "Hob",
"Sockets - kitchen", "Sockets - Upstairs", "Sockets - Garage",
"Sockets - Extension", "Immersion Heater", "Cooker", "Hall/Lounge
sockets downstairs".

Given that the rate of failure is so low and MTBF so long (for
elimination purposes), and that the sub-master trip is what goes
(rather than the individual trip for the misperforming part of the
system), which doesn't exactly narrow possibilities down, does anyone
have any ideas how we could go about finding the problem? Electrician
thinks the prime candidate is the fridge, which is the one thing that
we can't realistically turn off and see if everything carries on
working (plus it didn't trip for the 9 days we were away). Would
using an RCD on the fridge tell us anything - such as this

http://www.maplin.co.uk/Module.aspx?...FQaLEgodbE-F2g

http://tinyurl.com/26zt6u?

Could it be a fault in the consumer unit itself?

Thanks

Edward