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Doctor Drivel
 
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"John Rumm" wrote in message
...
Mr Fizzion wrote:

Can you have such a thing or is this one of Doctor Evil's fantasies?


It ought to work on "simple" combis so long as the manufacturer states
it is ok for the "cold" inlet temp to much hotter than it usually would.
You also need a combi that can operate on very low mains pressure (so
that it will work correctly when the flow is being driven by the pump
and not the mains).

However you could potentially run into all sorts of difficulties with a
modern combi that uses a more sophisticated control loop, or one that
includes a small store of tempered water so as to give "instant" hot

water.

What difficulties might these be? Or did you make that up?

If you can...how would you do it?


Timer, pipe stat, check valves, secondary circulation pump,


Can be booster pump to achieve the pressure to operate the combi.
http://www.heatweb.com/products/pumps/homebooster.html
Plumb Center also sell them. You also need a time clock to switch off
during the night.

loads of good insulation on the pipe run etc. You would then need to

juggle stat
temperatures carefully to get the operation you require without ending
up in a deadlock state with the pipe stat demanding heat and the combi
HW stat satisfied and hence inhibiting the burner (and the result that
the boiler sits in HW mode for extended periods while the house gets

cold).

Set the pipe stat to 40C