"Aidan" wrote in message
om...

It (primary/secondary pumping) is very
rare on UK domestic installations, mainly
because of the costs. IMM has mentioned a £250
controller; most domestic customers cringe
at £50 for a replacement heating
timeswitch/on-off controller. Whether IMM's
recommended controller is applicable to
this is another convoluted question,

Oh it is, you had better believe me.

but £250 is probably on the low side.

Not really, I did also mention a £160 controller with limited weather
compensation.

The £250 "two stage switched" controller plus the room sensor, or 4 of them
if you want to average temps, would be the only extra cost when using two
combi's. NO valves of any description to buy. NO tanks or cylinders. NO
pumps to buy as the boilers come with them. Just a Honeywell CM67, or
better still a Landis & Staefa equiv.

Each stage of the controller switches a combi. The 1st UFH stage a
condensing combi set to 55C and it will also modulate. The seconds stage
will also modulate, but supplies the rads. Seamless control..

Cost:

Two Biasi Riva condensing combi's can be had for just over £500 each. OK
these are at the lower end. Or more upmarket. An Ideal Icos condensing
combi for £750 and a regular non-condensing Worcester Bosch Junior for
around £560. So, for £1300 for two combi's.

The controls, let's say £320 in all.

A total of just over £1600 and then the rads and pipes on top. That is very,
very good and a top rated commercial controller thrown in.. If you want to
save on the boilers then A condensing Biasi at £500 plus a £381 regular
Biasi. that works out at: £1200 all in plus pipes. NB: I would not go for
the condensing Biasi. The regular is fine, just making a point.

With commercial stuff it's
tax-deductible, so they're less
price-sensitive and are prepared to
pay for effective control.

You would be very fortunate to find a
UK 'heating engineer' who
understood such a system.

Once understood it is quite easy. The £160 controller I mentioned is quite
easy to understand.