most efficent use of gas heating?
Discussion
Option 1 is self-contradictory.
To use 3 x 1 hour bursts to get to 16C is one thing, but you won't maintain that temperature... the house is continually losing heat (assuming external temperature <16C), so as soon as the boiler switches off at the end of its 1-hour burst, the temperature will start falling below 16C.
If you want it never to fall below 16C, you'd have to heat to well above 16C, so that it only drops to 16C just in time for the next 1hr burst from the boiler.
This would be less efficient than (2): Rate of heat loss depends on the difference between internal and external temperatures, so if you had to heat to (say) 22C in a burst, so that it remains above 16C until the next burst, you'll be losing heat at a greater rate than you would if you maintained a steady 16C.
How much above 16C you'd have to go (therefore how much difference in rate of heat loss/how much less efficient) depends on how well the house is insulated, infiltration rates, solar gain and incidental gains (body heat, cooking etc.), so it's difficult to give precise figiures. Thermal mass also has an effect, by 'damping' the peaks and troughs in temperature, but doesn't make a huge difference on average.
If you want to use Option 1 to maintain an average temperature of 16C, then broadly speaking there wouldn't be much difference in efficiency vs. option 2, but half the time your temperature would be above 16, and half below it.
To use 3 x 1 hour bursts to get to 16C is one thing, but you won't maintain that temperature... the house is continually losing heat (assuming external temperature <16C), so as soon as the boiler switches off at the end of its 1-hour burst, the temperature will start falling below 16C.
If you want it never to fall below 16C, you'd have to heat to well above 16C, so that it only drops to 16C just in time for the next 1hr burst from the boiler.
This would be less efficient than (2): Rate of heat loss depends on the difference between internal and external temperatures, so if you had to heat to (say) 22C in a burst, so that it remains above 16C until the next burst, you'll be losing heat at a greater rate than you would if you maintained a steady 16C.
How much above 16C you'd have to go (therefore how much difference in rate of heat loss/how much less efficient) depends on how well the house is insulated, infiltration rates, solar gain and incidental gains (body heat, cooking etc.), so it's difficult to give precise figiures. Thermal mass also has an effect, by 'damping' the peaks and troughs in temperature, but doesn't make a huge difference on average.
If you want to use Option 1 to maintain an average temperature of 16C, then broadly speaking there wouldn't be much difference in efficiency vs. option 2, but half the time your temperature would be above 16, and half below it.
You can go mad trying to pare the last few £ off a bill.
1) if you don't heat a room enough and you get mould, you're wasting money of redecorating or worse.
We turn those rads down on their TRVs, rather than off.
2), if you cycle the heating on and off every hour, you may find the temperature overshoots, wasting heat. Also you may start to feel cold as the room cools below target, so you may then need it warmer to feel warm.
3) Some houses change temperature quickly, some slowly. If you've got solid stone interior walls and floors, it will take ages to heat up and hold its temperature well. If you have timber frame and dry-lining, it will be much quicker to respond. Not everything suits everyone.
One thing worth trying is to turn the heating off say one hour before bedtime instead of half an hour, do you feel the difference?
Ask yourself:
Where is the heat going? draughts? ceiilings? windows? ???
Can you do anything sensible to reduce?
Main thing here is often knowing when to shut the windows to pre-empt the great outdoors cooling. In Spring and Autumn, letting the house overheat a little in the late afternoon pushes back the time we need the heating on.
But, big picture, maybe you can pay £2k a year in gas and be miserable, £2500 and be comfortable?
Perhaps a much-maligned smart meter might help us make sensible decisions?
1) if you don't heat a room enough and you get mould, you're wasting money of redecorating or worse.
We turn those rads down on their TRVs, rather than off.
2), if you cycle the heating on and off every hour, you may find the temperature overshoots, wasting heat. Also you may start to feel cold as the room cools below target, so you may then need it warmer to feel warm.
3) Some houses change temperature quickly, some slowly. If you've got solid stone interior walls and floors, it will take ages to heat up and hold its temperature well. If you have timber frame and dry-lining, it will be much quicker to respond. Not everything suits everyone.
One thing worth trying is to turn the heating off say one hour before bedtime instead of half an hour, do you feel the difference?
Ask yourself:
Where is the heat going? draughts? ceiilings? windows? ???
Can you do anything sensible to reduce?
Main thing here is often knowing when to shut the windows to pre-empt the great outdoors cooling. In Spring and Autumn, letting the house overheat a little in the late afternoon pushes back the time we need the heating on.
But, big picture, maybe you can pay £2k a year in gas and be miserable, £2500 and be comfortable?
Perhaps a much-maligned smart meter might help us make sensible decisions?
The most efficient way to run a boiler is at a low flow temperature for longer periods so it's not switching on and off very much. If your aim is to maintain a set temperature throughout the day you ideally need to match the boiler input with the house heat loss so it's only putting enough heat into the house to maintain the desired temperature rather than the normal method of adding excess heat then keeping that in check with thermostats. You can only do that with a boiler and heating controls that support weather or load compensation because as the outside temperature gets lower, the heat demand to maintain the house temperature obviously increases. There's not many third party "smart" controls that support this type of control and those that do only work with specific boilers and sometimes require additional connection modules to allow the controls to actually turn the boiler up and down rather than just on and off like most controls do, so it generally means going with the boiler manufacturer controls. The best weather compensation controls don't even have an indoor temperature sensor or room stat, once set up they work out how much heat the house needs based on an outdoor temperature sensor and run the boiler accordingly.
This method of heating a house goes against the idea of zoning and only heating rooms you're using so depending on how many rooms you don't heat it may or may not work out more efficient, but not heating certain rooms and zoning means the boiler is likely to be cycling a lot more heating individual rooms at different times and there'll always be heat shifting from the warm rooms to the colder ones even if doors are kept closed as internal walls / ceilings / floors within the house generally aren't insulated between them, so heating the whole house gently should give a more comfortable even temperature.
This method of heating a house goes against the idea of zoning and only heating rooms you're using so depending on how many rooms you don't heat it may or may not work out more efficient, but not heating certain rooms and zoning means the boiler is likely to be cycling a lot more heating individual rooms at different times and there'll always be heat shifting from the warm rooms to the colder ones even if doors are kept closed as internal walls / ceilings / floors within the house generally aren't insulated between them, so heating the whole house gently should give a more comfortable even temperature.
LocoBlade said:
The most efficient way to run a boiler is at a low flow temperature for longer periods so it's not switching on and off very much. If your aim is to maintain a set temperature throughout the day you ideally need to match the boiler input with the house heat loss so it's only putting enough heat into the house to maintain the desired temperature rather than the normal method of adding excess heat then keeping that in check with thermostats. You can only do that with a boiler and heating controls that support weather or load compensation because as the outside temperature gets lower, the heat demand to maintain the house temperature obviously increases. There's not many third party "smart" controls that support this type of control and those that do only work with specific boilers and sometimes require additional connection modules to allow the controls to actually turn the boiler up and down rather than just on and off like most controls do, so it generally means going with the boiler manufacturer controls. The best weather compensation controls don't even have an indoor temperature sensor or room stat, once set up they work out how much heat the house needs based on an outdoor temperature sensor and run the boiler accordingly.
This method of heating a house goes against the idea of zoning and only heating rooms you're using so depending on how many rooms you don't heat it may or may not work out more efficient, but not heating certain rooms and zoning means the boiler is likely to be cycling a lot more heating individual rooms at different times and there'll always be heat shifting from the warm rooms to the colder ones even if doors are kept closed as internal walls / ceilings / floors within the house generally aren't insulated between them, so heating the whole house gently should give a more comfortable even temperature.
The downside with running your heating at low flow temp for long hours is that you're running the pump the whole time. The small heat output you're getting may be mostly going to waste as room TRVs turn off.This method of heating a house goes against the idea of zoning and only heating rooms you're using so depending on how many rooms you don't heat it may or may not work out more efficient, but not heating certain rooms and zoning means the boiler is likely to be cycling a lot more heating individual rooms at different times and there'll always be heat shifting from the warm rooms to the colder ones even if doors are kept closed as internal walls / ceilings / floors within the house generally aren't insulated between them, so heating the whole house gently should give a more comfortable even temperature.
I'm sceptical about weather compensation after having had a new boiler with it a few years ago.
Basically, the control software was hopelessly inadequate.
You cannot know the heat required in a house like ours (which is fairly ordinary TBH) just from the outdoor temperature.
You'd need to know wind speed and direction, humidity, intensity and direction of sunshine.
Then you'd need to know what's going on in the house.
For instance, if the oven is on, that's a few kW not needed from a radiator. Likewise the iron, washing machine etc.
Even a couple of extra people in the lounge will make a difference.
Some of these things come down to needing a lot of sensors and programming effort to save a little bit of gas.
everything all comes down to how low the boiler can go if your boiler cant modulate down below 12KW anyway then your wasting lots of energy compared to one that can go down to 1.2KW
all controls need decent modulation especially fully zoned or weather comp.
if your boiler cant match the output of the rads that are calling for heat then your wasting energy.
and if you have 12KW output of rads but you only use 2 rooms with an output of 3KW then why heat the rest?
all controls need decent modulation especially fully zoned or weather comp.
if your boiler cant match the output of the rads that are calling for heat then your wasting energy.
and if you have 12KW output of rads but you only use 2 rooms with an output of 3KW then why heat the rest?
OutInTheShed said:
The downside with running your heating at low flow temp for long hours is that you're running the pump the whole time. The small heat output you're getting may be mostly going to waste as room TRVs turn off.
I'm sceptical about weather compensation after having had a new boiler with it a few years ago.
Basically, the control software was hopelessly inadequate.
You cannot know the heat required in a house like ours (which is fairly ordinary TBH) just from the outdoor temperature.
You'd need to know wind speed and direction, humidity, intensity and direction of sunshine.
Then you'd need to know what's going on in the house.
For instance, if the oven is on, that's a few kW not needed from a radiator. Likewise the iron, washing machine etc.
Even a couple of extra people in the lounge will make a difference.
Some of these things come down to needing a lot of sensors and programming effort to save a little bit of gas.
What boiler did you have as I think there's only a select few weather comp systems (like Veissmann) that actually work really well? I agree that weather comp can't be an exact science though based solely on outside temperature but I think it should still be more efficient and more consistent than stop start blasts of energy heating trying to keep the house at the same constant temperature relying on thermostats/TRVs everywhere to keep the boiler in check. I'm sceptical about weather compensation after having had a new boiler with it a few years ago.
Basically, the control software was hopelessly inadequate.
You cannot know the heat required in a house like ours (which is fairly ordinary TBH) just from the outdoor temperature.
You'd need to know wind speed and direction, humidity, intensity and direction of sunshine.
Then you'd need to know what's going on in the house.
For instance, if the oven is on, that's a few kW not needed from a radiator. Likewise the iron, washing machine etc.
Even a couple of extra people in the lounge will make a difference.
Some of these things come down to needing a lot of sensors and programming effort to save a little bit of gas.
I guess it depends how well insulated the house is as to how much difference body heat and appliances etc make, in a really well insulated house it will make a significant difference but less so in a less well insulated house. For us in the grand scheme of things I don't think running a pump is going to cost much compared to gas consumption when it's cold, even if it's running 24 hours at 100w (an overestimate) that's barely 65p a day at the current capped rate and every heating system will have the pump running for probably 8-10 hours in winter, so call it 35p/day difference? Adjusted for the April cap we were spending £12-14 (150kw+) on gas on the coldest days last winter, so even a 2-3% saving would compensate for any additional pump running cost.
LocoBlade said:
What boiler did you have as I think there's only a select few weather comp systems (like Veissmann) that actually work really well? I agree that weather comp can't be an exact science though based solely on outside temperature but I think it should still be more efficient and more consistent than stop start blasts of energy heating trying to keep the house at the same constant temperature relying on thermostats/TRVs everywhere to keep the boiler in check.
I guess it depends how well insulated the house is as to how much difference body heat and appliances etc make, in a really well insulated house it will make a significant difference but less so in a less well insulated house. For us in the grand scheme of things I don't think running a pump is going to cost much compared to gas consumption when it's cold, even if it's running 24 hours at 100w (an overestimate) that's barely 65p a day at the current capped rate and every heating system will have the pump running for probably 8-10 hours in winter, so call it 35p/day difference? Adjusted for the April cap we were spending £12-14 (150kw+) on gas on the coldest days last winter, so even a 2-3% saving would compensate for any additional pump running cost.
Modern boilers don't really work in stop-start blasts of energy.I guess it depends how well insulated the house is as to how much difference body heat and appliances etc make, in a really well insulated house it will make a significant difference but less so in a less well insulated house. For us in the grand scheme of things I don't think running a pump is going to cost much compared to gas consumption when it's cold, even if it's running 24 hours at 100w (an overestimate) that's barely 65p a day at the current capped rate and every heating system will have the pump running for probably 8-10 hours in winter, so call it 35p/day difference? Adjusted for the April cap we were spending £12-14 (150kw+) on gas on the coldest days last winter, so even a 2-3% saving would compensate for any additional pump running cost.
They are fiddling with the flow temp and modulating the pump according to demand.
At low demand, the flue fan probably draws more than the pump.
Our boiler is an Ideal.
They sent a stream of engineers and changed the PCB a few times before giving up and disconnecting the outdoor thermistor.
OutInTheShed said:
Modern boilers don't really work in stop-start blasts of energy.
They are fiddling with the flow temp and modulating the pump according to demand.
At low demand, the flue fan probably draws more than the pump.
Our boiler is an Ideal.
They sent a stream of engineers and changed the PCB a few times before giving up and disconnecting the outdoor thermistor.
Modern boilers do modulate pump speeds and the flame size to maintain the required flow temperature, but if you use most third party controls then you're limiting the benefit of a modern boiler as the flow will be fixed at whatever temperature the boiler is set to maintain regardless of demand because all the controls do is tell the boiler to turn on and off. If you have a system boiler with a hot water cylinder that fixed flow temperature needs to be at 65-70c so there's enough heat in the flow to heat the hot water, but that flow temperature is way higher than most radiators need even on the coldest days let alone underfloor. This is what I mean by (relative) blasts of excessive heat that's reined in by thermostats as running at an overly high flow temperature leads to excessively high return temperatures, which means less condensing and more cycling. With weather comp and load comp (Opentherm) controls, they obviously tell the boiler to turn on/off but also tell it to raise and lower the flow temperature based on demand and what is being heated, raising it when the hot tank is charging and reducing it for whatever heating demand there is, dropping the flow temp right down if that's all the heating needs to maintain the house temperature.They are fiddling with the flow temp and modulating the pump according to demand.
At low demand, the flue fan probably draws more than the pump.
Our boiler is an Ideal.
They sent a stream of engineers and changed the PCB a few times before giving up and disconnecting the outdoor thermistor.
Trustmeimadoctor said:
Yep it's working well for several years also got the hgi 80 for logging
Yep I've thought about going that route with my Vaillant but the controls we've got (Geniushub) still don't support Opentherm despite it being on their roadmap for several years, and if I'd known 18 months ago when I chose it all what I do now I'd have gone for Vaillant controls to get WC at the very least, but probably would have chosen a Veissmann boiler instead due to their equally good controls and ability to modulate far lower than the Vaillant, down to about 1.5kw compared to 6kw that the Vaillant can manage.
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