In an earlier contribution to this discussion,
Dave Fawthrop wrote:

I am setting up my nice new Combi heating system.
All radiators have TRVs except for the hall where I have a thermostat
and no TRV, the doors to the hall are normally open, the radiator
sizing is good having worked well for many years with the old boiler.

Should the thermostat be set above, below, or equal to the
temperature the hall reaches normally?

Equal - but you may need to throttle the hall radiator a bit with the
lockshield valve to ensure that it doesn't heat up too quickly and turn the
whole lot off before the TRVs have had a chance to operate.

Incidentally, assuming that the new boiler is a *condensing* combi, the
radiator sizing may no longer be good - bearing in mind that, for optimum
efficiency, condensing boilers need to run at lower flow and return
temperatures than conventional boilers - thus reducing the *effective*
capacity of each radiator.
--
Cheers,
Roger
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