In article , Andy Hall
wrote:

On Mon, 20 Sep 2004 10:03:15 +0100, "Christian McArdle"
wrote:

[Snip]

One method that could be used is to separate the heating circuit from the
combi boiler primary, using a plate heat exchanger. Then, the new circuit
can have a full time alpha pump, flow switch or whatever, with all TRVs. The
flow switch, which detects flow through any radiator is used connected to
the combi as the call for heat. The system would work and be efficient, but
viability depends on obtaining a cheap plate heat exchanger.

Cost is in the £80-100 range......



+--------+ PHE
| -------------++-------+-FS----- to rads
| Boiler | || BP
| -------------++---------+--------
+--------+

= external pump, run continuously
BP = bypass (p. not required if pump is alpha)
FS = flow switch, demands heat from boiler
PHE = plate heat exchanger


Christian.


.andy

Thanks, this looks a much more elegant approach than my idea for an
extra pump and valves. Either way it's going to be quite a lot more
expensive than just adding a flow switch if that had been feasible.

I'm reassured by Andy's earlier comment about the losses from cycling
when the TRVs are all off being low, so I'll probably just go ahead with
adding TRVs to the rest of the rads and see how things go. I'll try to
get a feel for the losses by monitoring the gas meter for a couple of
hours or so with all the rads shut down.

--
Mike Clarke