Central heating economy

[Adrian.Curran]

I have a heating system that consists of underfloor to part of ground floor of house and part radiator zone. The upstairs is a radiator zone. All is run by wood pellet boiler.
I have a fule consumption problem which i cannot resolve and have had different advice from people. Basically the way it is set up is u/floor heating all day at 20Deg and set back 17deg at night. Rads on morn for 2 hrs and evening for 6 hrs. Problem is boiler works fine at up to 70 deg with u/floor but as soon as rads kick in boiler temp drops to 50 and struggles to get up casusing high consumption. Someone advised me to run rads all time at low temps as they compared heating a Kettle from cold takes more energy that keeping the temp high by reboiling a hot kettle. I tried this and yes it did help keep the temps up to 70 but the consumption did not change much, in fact i cannot see any saving. The boiler is running efficently and is sized correctly. The fuel consumption thi swinter is 3 ton on 6-8weeks at £500 per ton House size 2300sqft. Would be grateful if anyone can advise.

 

[moony]

its a big house and im not clued up on pellet prices but that does seem an awful lot 1500 quid for a month and a half of heating? what was said when they installed it - did they give you a guide price on running costs?

 

[Adrian.Curran]

Sorry was typing in haste, it's £500 per 3 ton works out roughly £500 per two months during dec/Jan. Any thoughts now

 

[PuraTherm]

Pellet boilers are like heat pumps, they are intended for UFH. The only way to reduce your usage is to turn down the rads or install UFH upstairs. Rads just require too much heat to run.

 

[Adrian.Curran]

Thanks for this. Will it be better to leave rads on all time at lower temp

 

[PuraTherm]

You could try that but rads work off of convection and UFH works off of conduction. Because you are trying to heat air with the rads, air has a high thermal loss, they have to be at a higher temprature. The pellet boiler has to work harder to produce the higher tempratures. You might be able to run the rads at 40 to 45 but there again it's not what they are designed for. Sorry.

 

[Adrian.Curran]

No problem Thanks again

 

[ecowarm]

What size boiler is it?

 

[Adrian.Curran]

its a Scotte/Dor 4kw by Nordic Bio Energy

 

[Adrian.Curran]

opps last post should read Scotte/Dor 24kw by Nordic Bio Energy

 

[ecowarm]

Phew I just read 4kw and thought you must have a PassivHaus

 

[ecowarm]

24kw output should be able to cope even at the higher temp.

Has the performance gone down since installation?

 

[princegoose]

You could try that but rads work off of convection and UFH works off of conduction. Because you are trying to heat air with the rads, air has a high thermal loss, they have to be at a higher temprature. The pellet boiler has to work harder to produce the higher tempratures. You might be able to run the rads at 40 to 45 but there again it's not what they are designed for. Sorry.

Unless you size the radiators according to the heating water temperature. Im sure i read this is quit normal with air to water pumps, but the size of the radiators isnt.

basically you could install very large radiators upstairs.

 

[rapid]

i will say your boiler is a bit too small! y do you leave ur under floor heating on at night you got a bedroom on ground floor? have you tried turn ufh when u go to bed!

 

[ecowarm]

This boiler needs to have a minimum 60c return temp and any less it will not burn correctly and condensate on the inside causing it to rot

 

[Adrian.Curran]

Hi all just to continue with this. From day one we have had this problem. I cannot get any sense from the plumber. someone mentioned switching off UFH at night i was informed this is not economical as the temperature is easier maintained rather than starting from cool and that the prupose of UFH i was informed to use set back at night from 20deg during day to 17deg at night.
When rads are off the boiler works fine at 60-70deg mid to high burn when rads come on its as if the cold water from that zone reduces the heat from the boiler it drops to 50 and fluctuates between 50-58deg BUT if the rads are left continually on for a day or two the temp in the boiler does reach 68deg or so and burns mid to high. What i would like advice on is it better to leave the rads on but how do i manage to get some sort of equilibrium between fuel consumption and comfort.
I find plumbing to one subject that raises so many issues and different opinions.

 

[rapid]

is ur hourse new build or old house that recently got a new boiler fitted?? if you had a new boiler fitter it could be ur gas pipe is under size.

 

[rapid]

check gas prussure see if the gas regulator is damaged! and combustion of your boiler

 

[moony]

i will say your boiler is a bit too small! y do you leave ur under floor heating on at night you got a bedroom on ground floor? have you tried turn ufh when u go to bed!

under floor is designed to be 'left on' as the recovery times are too great if turned off for a length of time then back on - so you have a set back temp then a working temp so to speak.

what i do when i put radiators on a renewable heat source is oversize the rads and run at the underfloor heating temp.

 

[moony]

check gas prussure see if the gas regulator is damaged! and combustion of your boiler

its not a gas boiler matey - hence the pellets....

 

[moony]

Hi all just to continue with this. From day one we have had this problem. I cannot get any sense from the plumber. someone mentioned switching off UFH at night i was informed this is not economical as the temperature is easier maintained rather than starting from cool and that the prupose of UFH i was informed to use set back at night from 20deg during day to 17deg at night.
When rads are off the boiler works fine at 60-70deg mid to high burn when rads come on its as if the cold water from that zone reduces the heat from the boiler it drops to 50 and fluctuates between 50-58deg BUT if the rads are left continually on for a day or two the temp in the boiler does reach 68deg or so and burns mid to high. What i would like advice on is it better to leave the rads on but how do i manage to get some sort of equilibrium between fuel consumption and comfort.
I find plumbing to one subject that raises so many issues and different opinions.

i normally suggest a 5 degree drop for set back so 15 degrees is what id use if you found 20 degrees comfortable on the inderfloor, try leaving the rads on and use the room stat to control temp setting, 15 degrees in the day and 20 at night, not ideal but i must stress - pellet burners are not my area so maybe some other lads have got some advice regarding the actual boiler and consumption. Im not a fan of mixed installs on systems as it does cause these problems.

 

[Adrian.Curran]

Yes im beginning to belive you that a mixed system is a disaster. The house is new build 3 yrs old. Just after checking boiler after leaving heating rads and ufh on all day and night. Temp reasonable, fuel consumption appears no different to running rads intermitently. But still appears to be eating the pellets. Dred to think how it would go through oil

 

[Adrian.Curran]

ok but do you leave them on all the time like the UFH and whats the fuel consumption like.

 

[ecowarm]

You need to have a rethink on the system design, it can't work properly like this.

Pellet boilers run at the most effient flat out, high return temp so should be installed with an accumulation tank a thermostatic loading valve takes care of the return temp by mixing hot flow water into return untill return water is at the correct operating temp.

The radiators and underfloor are then taken from the accumulation tank at different heights, rads mid way or near top underfloor near bottom as it cooler near bottom.

The pellet boiler is controlled by stats and only comes on when it can have another full bore run at topping up the tank.


hope this helps

Eco

 

[Adrian.Curran]

complicated, not sure of all technicla aspects. Im not sure about the accumulation tank where is that sited. I know there is a mixing pipe near the boiler that takes some hot water and mixes that with the colder return. Yes ive been also told that pelllet boilers are at their most comfort running continually and dont like coming on for short bursts. I just cant find out why the return from the radiators is much colder when they run. as the return from UFH when it runs by itself is much hotter