Just had a new condensing central-heating boiler fitted. System has 12
radiators all fitted with TRVs except one nearest thermostat in hall. System
has been power-flushed. Boiler indicates 70 degrees temperature, hall
thermostat is set for 22 degrees. All TRVs are fully open.
Two radiators in lounge traditionally have been difficult to heat, being at
the end of a loop, and this has not improved with new work. The only way I
can keep hot water flowing to them is to close down the lock valves on other
radiators to a minimum – one-eighth of a turn in some cases upstairs.
To enable correct working of TRVs, is it better energy-wise to turn up the
boiler to, say, 75 degrees or to turn up thermostat to, say, 24 degrees? If
water is hotter, it should require less of it to make radiators hotter – is
this correct, or am I missing the point?
NB Reply to newsgroup. Email address will get you nowhere.
TRVs can only work if there is water being pumped around the system and
that will stop once the hall thermostat operates.
You need to set the hall thermostat to the hall temperature that you
require, then reduce the flow to the hall radiator so that the hall
thermostat only operates after all the other rooms have reached their
Turning the hall thermostat up, so as to keep water flowing to the other
rads, is simply wasting energy in running with the hall hotter than needed.
Turning up the boiler up will cause greater overshoots in room
temperatures plus risk injury to anyone falling against the radiators
plus waste more heat.
I would suggest setting the hall thermostat to the desired hall
temperature, but largely shutting off the hall radiator, so that the
radiators all get flow near enough constantly. Then set all the TRVs to
max and adjust the lock valves to ensure that all radiators are getting
an adequate supply. Then set the TRVs to get the required room
temperatures. Then open the hall radiator, bit by bit, until any room
temperature cannot be maintained - then close it off a bit.
But, IANA plumber - but do have a similar system. Although all my rads
have a good supply, even with all the lock valves open.
System needs balancing. Instructions are in the FAQ:
You get most efficient operation of a condensing boiler when you
set the flow temperature so that the room thermostat never quite has
to cut off, so boiler is running the coolest it can whilst providing
enough heat to match the heat loss from the house. You would need
to adjust this flow temperature upwards as the outdoor temperature
drops and more heat is lost. You will also need to adjust it upwards
whilst a cold house is getting up to temperature. Some more advanced
condensing boilers do this all automatically for you, but you didn't
say which one you have.
As for the TRV's, set them to the temperature you want each of the
rooms to be. They don't care about the water temperature. Remember
they are room temperature adjustments, not radiator temperature
adjustments -- don't try to set the radiator temperature with them
as you'll fail miserably. They will switch the raditors on and off
(and sometimes inbetween) as required.
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