Gas boiler settings

[swill453]

I must admit I haven't quite got my head around whether a higher or lower boiler temperature is better for economy.

I was tempted by a clickbait article on the subject, and I must admit it goes to an extreme I wouldn't have considered:

If you have a combi boiler, set your flow temperature to 50c for heating and 55c for hot water – it’ll take a little longer to heat up, but the gas and CO2 savings make it worthwhile.

https://www.manchestereveningnews.co.uk ... e-22841126

My settings are significantly above this. Any comments?

Scott.

[Lootman]

This article recommends 130 to 140 F (55 to 60 C):

"While turning the temperature up higher can result in burns, turning it lower than the recommended setting can also be dangerous. In colder water temperatures, bacteria can form in the water heater tank. This could become a health risk for you and your family, potentially exposing you to health hazards such as Legionnaires’ disease.

This illness is a type of pneumonia and the bacteria that causes the illness can thrive in a water tank between the temperatures of 77 degrees and 113 degrees Fahrenheit."

https://www.artplumbingandac.com/plumbi ... er-heater/

[swill453]

In my case it's a combi so no tank.

Scott.

[Mike4]

I must admit I haven't quite got my head around whether a higher or lower boiler temperature is better for economy.

I was tempted by a clickbait article on the subject, and I must admit it goes to an extreme I wouldn't have considered:

If you have a combi boiler, set your flow temperature to 50c for heating and 55c for hot water – it’ll take a little longer to heat up, but the gas and CO2 savings make it worthwhile.

https://www.manchestereveningnews.co.uk ... e-22841126

My settings are significantly above this. Any comments?

Scott.

Blimey the content of that link is hard to read in between the reams of adverts! (I opened it in an 'incognito' window to avoid their poxy cookies.)

But to your question. The answer is "it depends". But you knew that really, I bet...

To expand on this, a conventional heating system is designed to heat your whole house to 21c when it is (something like) a howling gale of -3c outside. To do this the boiler temp control needs to be set to MAX. (82c as they are rarely calibrated in degrees C.) The boiler control sets the temperature of the circulating water coming out of the boiler being sent to the rads, so determines how hot the rads get, while the heating is ON.

If the weather outside happens to be less severe, you can probably set the boiler temp control, and consequently the rad temp, a bit (or a lot) lower. Whether this saves any fuel is a moot point as it still takes the same amount of power to balance the heat loss from your house for a given interior temperature. So as you can perhaps imagine, if you set the flow temp from your boiler to your rads lower, your heating system will respond by running for longer. But your boiler will be cycling on and off at the lower temp during this longer running.

However, if you have a modern condensing boiler (mandatory on new boiler installations since 2005), it will run at perhaps 10% higher fuel efficiency whilst condensing. This means having the flow temp set to 56c or lower (loosely speaking, to make it condense). So probably there is a small fuel saving on a modern boiler if you run it cool. Additionally, unlike older style boilers which are either alight or not, condensing boilers modulate their output. They start off at a low flame and slowly ramp up to deliver whatever the selected water temp, and progressively lower the flame size as that temp is approached. This helps with fuel economy too, although I remain to be convinced it makes a great deal of difference.

There is a page on my website (IIRC!) discussing what to set your boiler temp control to. People ask me about this constantly nowadays which is odd, because ten years ago no-one ever mentioned it.

[AF62]

If the temperature of the water to the radiators is lower, and thus the house takes longer to warm, then the house will take longer to warm up from cold.

For those people out working, won’t they just set the heating to turn on earlier than they would otherwise have done so the house is warm when they arrive home, so negating some (all?) of the savings?

[stewamax]

Further to Mike4's reply, boiler manufacturers will be delighted to sell you a weather compensator - an outdoor thermometer linked to the boiler. When it gets cold outside, the mechanism ramps up the boiler outflow temperature and brings it down again when the weather gets warmer. Viessmann, for example, claim a gas saving of up to 15% p.a. together with room temperatures that fluctuate less. Their range of outflow temperatures is wide: at outside -20degC the boiler outflow is 90degC, whereas at outside 20degC the boiler outflow is 35degC (!), although their most intelligent boilers don't work in quite such as crude way and can be adjusted to take unto account how well a building is insulated. Worcester-Bosch et al have similar products.

[csearle]

In the mid eighties I moved into a new German house near Stuttgart and noted the outside temperature gauge. I asked my landlord, the architect, about it and he told me that all (then) modern heating systems included these. So they have been around for decades in first-world countries. C.

[Mike4]

Further to Mike4's reply, boiler manufacturers will be delighted to sell you a weather compensator - an outdoor thermometer linked to the boiler. When it gets cold outside, the mechanism ramps up the boiler outflow temperature and brings it down again when the weather gets warmer. Viessmann, for example, claim a gas saving of up to 15% p.a. together with room temperatures that fluctuate less. Their range of outflow temperatures is wide: at outside -20degC the boiler outflow is 90degC, whereas at outside 20degC the boiler outflow is 35degC (!), although their most intelligent boilers don't work in quite such as crude way and can be adjusted to take unto account how well a building is insulated. Worcester-Bosch et al have similar products.

Weather compensation has been around to my knowledge since the 1970s (and possibly earlier), but never caught on because people like to vary the temp in their houses according to how active and warm they feel. If you're say, hoovering as opposed to lazing in front of the telly, you're more likely to turn the room stat down, than up as you would if you're feeling a bit chilly. There is nothing to change when you have weather comp, short of logging in and adjusting your software compensation curves. This is also the reason I suspect heat pumps won't ever be popular.

The other problem with WC is non-technical people simply can't understand what is going on, with no room stat. I mean, can you imagine trying to explain how it works to your mum, or to the little old lady queueing at the Post Office counter?

[9873210]

There is nothing* that prevents having a whole house or individual room thermostats with weather compensation. It's a simple control problem. The thermostat(s) set the target temperature(s) and the control system takes the weather, the parameters of the boiler and the characteristics of the house** into account and figures out the most efficient way to get there. The user or installer need not set the boiler temperature, the controller figures out what is needed.

* Except for retraining plumbers and the public, which may be impossible. People still think cranking the thermostat to the max will heat the house up faster (ironically if there is a somewhat smart controller that actually works, although not with a much smarter controller)
** These can be deduced on the fly by the controller from operational history, they don't need to be set manually.

[UncleEbenezer]

Hmm. I did some googling when I got the new boiler, and found lots of recommendations to run heating at 70+ with hot water at not more than 60. So that's what I set (hot water now being set higher than in summer)! Are you saying that's inefficient?

[Mike4]

There is nothing* that prevents having a whole house or individual room thermostats with weather compensation. It's a simple control problem. The thermostat(s) set the target temperature(s) and the control system takes the weather, the parameters of the boiler and the characteristics of the house** into account and figures out the most efficient way to get there. The user or installer need not set the boiler temperature, the controller figures out what is needed.

* Except for retraining plumbers and the public, which may be impossible. People still think cranking the thermostat to the max will heat the house up faster (ironically if there is a somewhat smart controller that actually works, although not with a much smarter controller)
** These can be deduced on the fly by the controller from operational history, they don't need to be set manually.

Missing my point by a country mile!

[9873210]

There is nothing* that prevents having a whole house or individual room thermostats with weather compensation. It's a simple control problem. The thermostat(s) set the target temperature(s) and the control system takes the weather, the parameters of the boiler and the characteristics of the house** into account and figures out the most efficient way to get there. The user or installer need not set the boiler temperature, the controller figures out what is needed.

* Except for retraining plumbers and the public, which may be impossible. People still think cranking the thermostat to the max will heat the house up faster (ironically if there is a somewhat smart controller that actually works, although not with a much smarter controller)
** These can be deduced on the fly by the controller from operational history, they don't need to be set manually.

Missing my point by a country mile!

Perhaps you could express it better.

You can combine weather compensation with a thermostat and explain to mom that the temperature set on the stat will be the temperature in the room, if she wants it hotter turn it up a degree or two and if she wants it colder turn it down. She does not need to understand Kalman filters or thermodynamics.

[scotview]

I think that an order of magnitude more important than outside temp compensation or exit water temperature is to have as small a kW rating of boiler as is practicable and only heat those rooms that need heat. We have four zones for a 3 bed house and have a 15kW boiler. 90% of the time the boiler is modulating at low output at good low firing efficiency, the other 10% of the time when the whole home needs heating it just takes a little longer to heat. We have an open vented hot water tank system.

Most combi boilers for a house like ours will probably be rated at 30/40 kW and with no zoning. These systems waste a lot of heat and spew out unnecessary CO2.

Rather than mandate heat pumps, I think a strategy of insulation, zoning, educating people on heat control, and minimizing boiler kW would maybe be a nice transition strategy.....hey ho.

[stewamax]

Weather compensation ... never caught on because people like to vary the temp in their houses according to how active and warm they feel. If you're say, hoovering as opposed to lazing in front of the telly, you're more likely to turn the room stat down, than up as you would if you're feeling a bit chilly. There is nothing to change when you have weather comp, short of logging in and adjusting your software compensation curves. This is also the reason I suspect heat pumps won't ever be popular.

Definitely. There is the wrong assumption made by boiler makers and those who sell CH systems that we want our rooms to stay at a constant temperature, irrespective of what we are doing.

[9873210]

Weather compensation ... never caught on because people like to vary the temp in their houses according to how active and warm they feel. If you're say, hoovering as opposed to lazing in front of the telly, you're more likely to turn the room stat down, than up as you would if you're feeling a bit chilly. There is nothing to change when you have weather comp, short of logging in and adjusting your software compensation curves. This is also the reason I suspect heat pumps won't ever be popular.

Definitely. There is the wrong assumption made by boiler makers and those who sell CH systems that we want our rooms to stay at a constant temperature, irrespective of what we are doing.

[sarcasm]Which is why thermostats with dials to set the temperature and set back thermostats and smart thermostats, whose entire purpose is to vary the room temperature to match the desires of the occupants do not exist.[/sarcasm]

The assumption is yours and perhaps the central heaters installers. It is not an assumption made by boiler makers or other equipment makers. Problem exists between keyboard and chair.

[DrFfybes]

You can combine weather compensation with a thermostat and explain to mom that the temperature set on the stat will be the temperature in the room, if she wants it hotter turn it up a degree or two and if she wants it colder turn it down. She does not need to understand Kalman filters or thermodynamics.

Yes, but she'll still turn it up 5 degrees, then back down 5 degrees when it gers too hot.

And as for explaining TRVs to an 80 year old who still thiught the lockshields affected how hot the rads got.

And there's the rub - all this fancy technology is tinkering around the edges of the human override, which is often down to a lack of understanding. The savings are there, but a lot are theoretical and depend onideal scenarios, in the real world the biggest saving we would make replacing our 40 year old Gloworm would be losing the pilot light.

And £5k+ for new kit and controls pays for a lot of gas, even at today's prices.


Back to the OT - running the rads cooler will result in less heat loss from the pipes if they are uninsulated under the floor, especially if the floor void is ventilated.

Paul

[88V8]

And there's the rub - all this fancy technology is tinkering around the edges of the human override, which is often down to a lack of understanding.
And £5k+ for new kit and controls pays for a lot of gas, even at today's prices.

Back to the OT - running the rads cooler will result in less heat loss from the pipes if they are uninsulated under the floor, especially if the floor void is ventilated.

Anything that involves education and understanding is doomed.
And zoning is good but requires keeping the internal doors shut.
£5k will generate £250pa of (pretax) income so that has to be saved before one even thinks about payback.
All pipes should be insulated, even those upstairs. But most householders have not the slightest clue about what installers are doing and just go for the cheapest quote, so no insulation.

Our previous house where I designed and installed the ch in 1983, we ran a 1300 sq ft detached on a 60,000 bthu boiler, the rads were not oversized because I calculated the per room heat requirements carefully which no installer is going to do, all the pipes were insulated, we heated different rooms to different design temps, we kept the doors shut, and the hall stat that ran the whole system was set to low 60s.
This despite solid walls, and not much loft insulation.

Efficiency is possible, it doesn't need fancy technology, but it falls down at the human element which I sometimes think is becoming more stupid not less.... who was it commented in another place that in the past a car's owners' manual told you how to set the valve clearances, now it tells you not to drink the battery acid.

V8

[Mike4]

And there's the rub - all this fancy technology is tinkering around the edges of the human override, which is often down to a lack of understanding.
And £5k+ for new kit and controls pays for a lot of gas, even at today's prices.

Back to the OT - running the rads cooler will result in less heat loss from the pipes if they are uninsulated under the floor, especially if the floor void is ventilated.

Anything that involves education and understanding is doomed.
And zoning is good but requires keeping the internal doors shut.
£5k will generate £250pa of (pretax) income so that has to be saved before one even thinks about payback.
All pipes should be insulated, even those upstairs. But most householders have not the slightest clue about what installers are doing and just go for the cheapest quote, so no insulation.

Our previous house where I designed and installed the ch in 1983, we ran a 1300 sq ft detached on a 60,000 bthu boiler, the rads were not oversized because I calculated the per room heat requirements carefully which no installer is going to do, all the pipes were insulated, we heated different rooms to different design temps, we kept the doors shut, and the hall stat that ran the whole system was set to low 60s.
This despite solid walls, and not much loft insulation.

Efficiency is possible, it doesn't need fancy technology, but it falls down at the human element which I sometimes think is becoming more stupid not less.... who was it commented in another place that in the past a car's owners' manual told you how to set the valve clearances, now it tells you not to drink the battery acid.

V8

Lol very true!

And was it here or somewhere else we were discussing how crucial it is to stop the engine if the oil pressure light comes on, then someone pointed out they use that light as an indicator to check the oil level some time soon?

[tjh290633]

Our original boiler in 1977 had no thermostat on the hot water tank and cycled on and off when there was no demand . It sprang a leak in 1996 and was replaced with a newer model, the system was remodelled with a 3-way valve and a tank thermostat, and a new control system.no pilot light now.

The gas consumption fell by about 30%, and in cold weather I found that leaving it on 24/7 for heating used no more gas than turning it off overnight. By cold weather I mean sub zero during the day. My conclusion is that turning the heating off during the day and at night is of marginal if any benefit. Likewise varying the temperature settings. The energy used to get back to temperature is more than that needed to maintain it.

TJH

[BullDog]

Our original boiler in 1977 had no thermostat on the hot water tank and cycled on and off when there was no demand . It sprang a leak in 1996 and was replaced with a newer model, the system was remodelled with a 3-way valve and a tank thermostat, and a new control system.no pilot light now.

The gas consumption fell by about 30%, and in cold weather I found that leaving it on 24/7 for heating used no more gas than turning it off overnight. By cold weather I mean sub zero during the day. My conclusion is that turning the heating off during the day and at night is of marginal if any benefit. Likewise varying the temperature settings. The energy used to get back to temperature is more than that needed to maintain it.

TJH

Correct. We were very surprised that when Mrs BD quit work and the heating stayed on all day, the monthly gas consumption stayed exactly the same as when we had the heating switched off all day during work hours. Surprising but absolutely true.