Another heating query

[Budgie]

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?

[Palindr☻me]

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 required temperatures.

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.

[Andrew Gabriel]

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.

[Codswallop]

If you decide to balance the radiators and need a thermometer I found that this one worked fine: