Christian McArdle wrote:

My plan is to fit a trv to the hall radiator and turn it down,
along with the other room radiators.


This won't work. If the hall TRV is set above the room thermostat, than the
TRV will never operate. If the TRV is set below the room thermostat, the
heating will never turn off and is the equivalent to shorting out the room
thermostat. This will keep the conservatory warm. However, the boiler will
remain on constantly, even when no heat is required, costing you a fortune
if the boiler cutout doesn't operate.


But they do.

I ran my old house like that for 6 years no problem. TRV's on all rads
except bathroom, and stat on max. the PUMP runs all the time. The boiler
does not...eventually there is just one super hot bathroom, and the
pipes going to it, and the boiler occasionally firing up to keep it that
way.

Short of a zone for every room with its own thermostat, its actually the
best way to do it. You CAN balance everything and hope that the heat
losses stay teh same, and the master stat will do everything right, but
its a darned sight cheaper to TRV everything, so you can turn down
certain rooms when not in use.



The only solution that will really be satisfactory in your situation is to
have a separate zone for the conservatory. This means that the conservatory
will have its own programmable thermostat totally independent from the rest
of the house. It also allows different time scales to be used. If, for
example, the conservatory is used as a dining room, the timer can be set to
only heat it for the early evening, saving you loads in keeping a poorly
insulated conservatory hot for the entire day and evening.


I disagree..



Another alternative is to have TRVs in every room and remove the room
thermostat. Then an automatic bypass loop is used (any old manual one
removed) with a flow switch that can turn off the boiler when the automatic
bypass opens. This solution is not as good, as there isn't separate timing
for the conservatory. However, it may be easier to implement if the pipework
isn't conducive to sub zoning.


That is pretty much what I suggested. Except why remove the stat? Just
whack it up to full...and the auto bypass? That's a neat idea..except
that without the pump running all the time, and using the boiler to
monitor flow temp, how does it know when to cut in again?

All I can say is the bodge described WORKS. Short of re-engineering
everything, its a good compromise between economy, cost of installation,
and pump life.

Its IMHO the best compromise to upgrading an existing system to get
better control over room temps without going to a proper fully zoned
system complete with loads of motorised valves and thermostats, which
need a lot of wiring as well as re-plumbing.




Christian.