Conventional boiler temperature control

[chalkywhite]

Hi, my Greenstar Ri boiler has a dial temp range of between 35 and 82C.

I appreciate that the higher temps use more gas but get rooms up to temp quicker and more heat is retained in rads for longer.

Why then, would I ever want to reduce it?

Currently set to around three quarters of max dial setting, which would be ~70C, and house heats up nicely. Water tank has its own thermostat which seems to click on and off properly.

Cheers

 

[muggles]

You've answered your own question. Turning it down will reduce gas consumption, making it cheaper to run.

 

[chalkywhite]

What I dont get is that surely over the longer duration on the lower setting it will use as much gas?

 

[Razor900]

You won't be able to reduce the temp very much assuming it's on an S or Y plan system or you will start getting long hot water cylinder reheat times.

If you run the rads at 82 degrees when the room thermostat shuts the system off the rads will continue to give heat out and the temp will overshoot the desired value by a few degrees then as it cools it will drop below the required temp and the system will yoyo between too cold and too hot.

The lower you can run the flow temp and have decent reheat the better

 

[muggles]

Condensing boilers only start to condense (and therefore run at their best efficiency) with a flow temperature of 70°C and a return temperature of 50°C. Higher than that, they stop condensing and start throwing more heat out of the flue. Lower encourages more condensing (lower flue gas temps, more heat going into your system rather than out your wall) but as Razor says you need a high enough flow temperature to heat your cylinder, so it's a compromise