John Rumm wrote:
* But the UHF rooms will have their own thermostat on the wall anyway
which controls a zone valve on the manifold

Does this zone valve do any blending to achieve lower flow temperatures
typically used for UFH, or does it just modulate the on/off demand to
control them?

Yes, there is a separate UFH pump and blending valve so the temperature
of the UFH circuit may be set correctly at a lower value than the
primary boiler/heating circuit.

[...]
But the question is, how weather compensation and intelligent boiler
controls can be connected to a UFH system which just calls for heat in
an on-off fashion? And does this destroy the efficiency?
[...]
The first bit, about how you interface an external demand I can't answer
definitively with that stat / boiler combination - since its not
covered in the compensator docs (it may be in the boiler manual - which
I have not read in detail). I would assume that any additional demand
would be met with a flow temperature as dictated by the compensator. The
only time that might be a limitation the UFH is if you are using some
fixed blending arrangement rather than a thermostatically controlled
one; since this might give a blended temperature that is too low to be
useful.

This is how we'd imagined it could work: the trouble is that Worcester
Bosch are being singularly unhelpful!