Setting Boiler Temperature

fourteen85 | 14:20 Wed 23rd Nov 2022 | Home & Garden

20 Answers

There has been a fair bit of talk lately about reducing the set temperature on a combination boiler to reduce the amount of gas used. Isn't this only a saving if you keep the boiler on for the same amount of time? We use our boiler on a manual setting and put it on when cold and off when we are warm, using it this way surely we would use the same amount of gas if the boiler temp was set higher as we would then turn it off sooner. Or am I missing something?

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SparklyKid

We do the same, on when cold, of when warm, seems sensible

barry1010

I've heard a lot of talk about resetting the flow temperature, I don't have a combi boiler so don't really understand it https://www.google.com/amp/s/www.examinerlive.co.uk/news/cost-of-living/martin-lewis-shares-simple-boiler-25239964.amp

The Builder

I guess you mean the "flow temperature".
Modern condensing boilers are actually slightly more efficient at a reduced flow temp.
Rather than have me rattle on, have a read here...........

https://www.theheatinghub.co.uk/articles/turn-down-the-boiler-flow-temperature

It surprised me to learn that max. efficiency can be around only 45 degrees.

As for the length of time the boiler is on... really a matter of trial and error. It will vary immensely for different properties.
As I see it, if it's on for longer but with a lower flow temp, then you are surely going to be toasty for longer, but with no extra cost. (Theoretically.)

Following the principle of "energy in = heat out", I think we're just fiddling around the edges here.
In older, less insulated houses, a lower flow temp may not even be enough to heat sufficiently.

barry1010

Better link http://www.moneysavingboilerchallenge.com/

Atheist

We keep our combi boiler set to run without using the timer. As well as thermostatic radiator valves on all but one rad, we have a room thermostat in the living room, which we set on lowest setting when heating is not required (i.e., Summer or mild weather, when we leave the house, and at night). I learned about heating many years ago, when I was taught that the boiler burns most efficiently when set to give a flow temperature of 80 degrees. That way, the rads get pretty hot and so the rooms heat up more quickly than if the boiler itself was set cool. The TRV's shut down the rad when rooms are warm (e.g. bedrooms which can be kept cooler most of the time), and the boiler itself is shut down by the room thermostat.
I have read lately that turning down the boiler temperature is a good thing, so I am probably out of date, as it seems to be the case that condensing boilers are efficient even when run at a lower temperature.
Maybe someone else here knows more about it that I do.

bhg481

Your room thermostat switches off the boiler when the room reaches the chosen temperature. At that time there will still be hot water in the radiators which will continue to dissipate into the rooms, thus raising the room temperature slightly above the chosen temperature; in other words, that heat will be wasted. The cooler you have the water temperature in the boiler the less heat will be wasted this way. Of course, if you have the water temperature set too low the rooms might never reach the chosen temperature on a very cold day.
We're talking theory here; in practice I can't see it making a serious difference.

Atheist

Builder, you jumped in before I finished typing my post. Of course, running the boiler at a lower temperature can throw off the overall heating capability if the system has rads designed for an 80 degree flow and a 70 degree return, and so any theoretical boiler efficiency based on a condensing boiler run cool might not be available, as the house wouldn't heat up properly.

Atheist

...as BHG has said above.

Hopkirk

Personally I find it more comfortable to have heating that purrs away keeping a steady temperature, rather than radiators that keep getting very hot but switching on and off.

The downside is if the heating is off, perhaps overnight, it takes longer to heat up.

Atheist

Hopkirk:
"Personally I find it more comfortable to have heating that purrs away keeping a steady temperature, rather than radiators that keep getting very hot but switching on and off."
How do you achieve that? You must have some device that keeps it purring at just the right temperature. I call it a thermostat.