Hzatph wrote:

Interesting responses thank you. Giving Aga a call sounds a great idea and
I will do that. The pumped system will need to be turned right down so as
not to exceed the modest heat output capability of the Aga which is oil by
the way. I don't really want to run a 240,000 BTU boiler just to heat a
water cylinder in summer. The boiler will feed something like 28 radiators
so the prospect of all being shut down sounds unlikely - a no-flow switch
closing down the boiler sounds much more sensible than a room thermostat
in one room.

If your Aga heats water for the radiators/HW circuit continuously then the
standard system (as descriped by TNP and Andy H) is not applicable, since
the room stat cannot turn off the heat source (though it could operate the
circulating pump). OTOH if your Aga has a separate heating boiler inside it
(I don't know if Agas have this arrangement but I know that some Aga-like
ranges do) then you should treat it like a normal CH boiler with a room
stat arrangement.