CH - Boiler to max or middle?

[beko1987]

Was in the pub last night for their fireworks show, and got chatting to someone. We got talking about heating, and I mentioned that out rads never got very hot, despite the thermostat being quite high.

He recommended to turn the boiler up to full, then the thermostat won't have to be as high.

I tried it last night, and the rads quickly got too hot to touch, and we could turn the stat down to about a quarter and stayed toasty warm.

However, does having the boiler on full, and the thermostat down munch more gas? I can sort of see where he is coming from, get the boiler up to temp quickly, then it should cost less to stay there, but I don't want a nasty surprise in Feb when the next quarters bill comes in!

[paulrockliffe]

The question is really at what temperature is the system most efficient. Anyone any ideas? Mine has an 'Eco' label about 3/4s of the way to max, so maybe it's there?

[Mave]

I guess running the boiler hotter will use more fuel simply because previously your house was colder! Turning up the thermostat up makes no difference if the boiler can't deliver any more heat... The most efficient boiler temp is the lowest that gets you the room temp you want, but in reality you need it set higher to keep the warm up time sensible.

[Gingerbread Man]

Rads are designed to run with ~80' water. Turning the stat down will mean less output from the rads, so the heating stays on longer to heat the room before turning off. Similarly it'll take longer to transfer the needed heat into the hot water cylinder. I normally turn the boiler temp to max and then knock it back a little bit.

[Mave]

Gingerbread Man said:

Rads are designed to run with ~80' water. Turning the stat down will mean less output from the rads

I think it's more about the quoted output being at 80 than them being designed for 80. If you need them to be at 80 in anything but the coldest winter, then imho they're too small...

[Gingerbread Man]

Mave said:

Gingerbread Man said:

Rads are designed to run with ~80' water. Turning the stat down will mean less output from the rads

I think it's more about the quoted output being at 80 than them being designed for 80. If you need them to be at 80 in anything but the coldest winter, then imho they're too small...

But working out heat losses for the room, therefore gauging the size of the radiator to heat the room rely on the destined radiator to be filled with ~80 degree water.

So for the room to happily meet the designed temperature, the rads need to be running at the designed temperature to achieve the output.

[Tampon]

I always work on the basis of full wack, I want heat when it is cold so the thing is going to give it to me asap.

No idea if this has a effect on the boiler, I boil water in the hob on full wack and don;t think about that either.

[Gingerbread Man]

Tampon said:

I always work on the basis of full wack, I want heat when it is cold so the thing is going to give it to me asap.

No idea if this has a effect on the boiler, I boil water in the hob on full wack and don;t think about that either.

Too right. If the radiator water was only 50 degrees, and your room thermostat was set at 25 degrees, it would take quite a long wait for the house to get up to temp and for the room stat to click off. So the boiler is on longer and using gas for longer.

Wack it up to max then back to slightly off to avoid any chance of overheating issues. Rads running around 80. Cylinder water gets up to temp quicker. Things are designed for a reason.

[Pixelpeep]

i think its like driving a car.

You'll get to 100mph eventually regardless of how much throttle you use (as long as its some lol) - getting there quicker uses more fuel so not recommended.

also like a car, if you can get to 100mph with power to spare you get extra man points.


edit to say, ours has a pretty blue LCD display that says things like DHW 40 degrees and Pump Over run. - it just excites the geek in me. it also never goes above half for rad temp. mainly because i prefer things to be over engineered for my requirements so we got one that would do double the rads we have. Just incase, ya know..

Edited by Pixelpeep on Wednesday 6th November 18:37

[Gingerbread Man]

Pixelpeep said:

we got one that would do double the rads we have. Just incase, ya know..

But if it's a condensing boiler, they should be slightly undersized, so working flat out to sit in the most efficient condensing mode most of the time.

If over sized, a condensing boiler won't be getting you the fuel savings that you'd hope for.

[Mave]

Gingerbread Man said:

But working out heat losses for the room, therefore gauging the size of the radiator to heat the room rely on the destined radiator to be filled with ~80 degree water.

So for the room to happily meet the designed temperature, the rads need to be running at the designed temperature to achieve the output.

The 80 degree number is just for comparison. Car manufacturers used to quote fuel consumption at 75mph, doesn't mean you should drive at that speed. If you size your radiators to 80c for the current temperatures, what are you going ti do when it gets really cold? Run them at 90?

[Mave]

Gingerbread Man said:

Too right. If the radiator water was only 50 degrees, and your room thermostat was set at 25 degrees, it would take quite a long wait for the house to get up to temp and for the room stat to click off. So the boiler is on longer and using gas for longer. .

The boiler isn't on for longer though. When it gets to 50c it shuts off and doesn't carry on burning fuel! If anything, it's slightly more efficient because you get slightly better heat transfer from flame temperature to 50c water than 80c water.... Just takes longer so you make sure your radiators are big enough when you design the system :-)

[Rickyy]

Pixelpeep said:

i think its like driving a car.

You'll get to 100mph eventually regardless of how much throttle you use (as long as its some lol) - getting there quicker uses more fuel so not recommended.

also like a car, if you can get to 100mph with power to spare you get extra man points.


edit to say, ours has a pretty blue LCD display that says things like DHW 40 degrees and Pump Over run. - it just excites the geek in me. it also never goes above half for rad temp. mainly because i prefer things to be over engineered for my requirements so we got one that would do double the rads we have. Just incase, ya know..

Edited by Pixelpeep on Wednesday 6th November 18:37

Ideal Logic +?

The boiler stat only gets turned right the way up when it is minus temps outside.

[Mave]

Rickyy said:

The boiler stat only gets turned right the way up when it is minus temps outside.

Agreed, no point having radiators hot enough to burn your skin unless it's sub zero out, and only then if you've allowed the house to get below the 5c frost temperature...

[KTF]

Rickyy said:

Ideal Logic +?

The boiler stat only gets turned right the way up when it is minus temps outside.

What setting do you normally have it set to?

I have an Ideal Icos with a similar dial on the front. The previous owners always had it set to max but I have turned it down a bit and there is seemingly no difference - the hot water still heats up in a similar time in the morning.