"John Aston" wrote in message
.. .

Aidan wrote in message
om...

It (primary/secondary pumping) is very rare on UK domestic
installations, mainly because of the costs.

snip

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

Also, the Americans generally have bigger houses, so it's more common
in the US. See ' Primary-Secondary Pumping made Easy' by Dan Holohan,
available from HeatingHelp.com. It's written for home owners, so it's
fairly free from techno-jargon. It's in US/Imperial units (gpm,
BTU/hr, degF) but it's easy to grasp.

If anyone else is reading this thread and wants some background
information,
I came across Warmrite's "Manual Of Modern Hydronics" at
http://www.heatinghelp.com/pdfs/156.pdf

It gives loads of examples of different boiler/heating arrangements.

I had a look. The document is specific to UFH and the USA/Canada variantions
and heavily leans towards the makers solutions. Look at figs. 2.1, regular
boiler & 2.2, condensing boiler. Condensing biolers should not mix return
water that woudl raise its temperature. That is why a thermal store/heat
bank is the best alternative when using a condesning boiler, which is what I
have been trying to get you to understand.

The North Americans are way ahead of us in dosmestic forced air and vent, to
the point we are hardly in the race.