On Thu, 11 Jan 2018 11:49:24 +0000, Tim Lamb wrote:

Doesn't the thermal store act as a "buffer tank"? The boiler being
controlled by the temperature of the store not by room stats.

A zone, be that DHW or space heating, takes heat from the store.
If
the store has enough heat that's all that happens, if it doesn't
and
it cools below a given point the boiler is fired up to reheat the
store.

Umm.. I don't know:-) I assume the boiler supplies heat to the thermal
store until the DHW stat. is satisfied.

You don't have any stored DHW so no DHW stat. To control the DHW
temperature there should be thermostatic mixer valve on the thermal
stores DHW coil output to stop 80+ C water being deliverd to the
taps. DHW is heated on demand by passing through the coil in the
(upper part of the) thermal store.

There are pumps supplied with each manifold but I assume they only
circulate water round the associated floor heating circuits.

Possibly, no pratical experiennce of wet underfloor heating.

The store doesn't have to supply the total heat demand in one hit,
once it cools below it's "reheat" point the boiler will be
thumping
heat back into it. We have a 300 l store and 30 kW boiler that
reheats at about 2 C/minute, with say a heating zone demanding
heat,
Remember the boiler will be taking water from near the bottom of
the
store that'll be at 30 to 40 C and returning it to near the top at
at
a round 80 C.

Ah! I don't have a separate coil for CH.

Neither have I. The water in the store is the same water circulated
around the CH zones, the wood burner and oil burner loops. The DHW
passes through a coil immersed in that water to pick up heat. The
solar thermal has a coil because that loop is heavyly dosed with
glycol to stop it freezing at the collector.

The system suppliers are not very forthcoming and seem to assume you
will use professional installers:-(

Who might not understand it either... ours didn't.

--
Cheers
Dave.