Replacement Boilers & Building regs….Sneaky NASTY rule change?

[Stevekane]

Here is a link to the article about Boiler Oversizeing, interesting read.
https://www.theheatinghub.co.uk/oversized-boilers-are-bad-your-bank-balance-and-the-planet

 

[Spectric]

Another bad aspect of the combi boiler, you need a lot of BTU's to get instant hot water but with a system boiler you still get hot water just that it is a gradual process to fill a cylinder, mine takes 20 minutes from cold. So with a combi you will have an oversized boiler for your heating, you are trying to get the one tool for every job but end up with it does every job just not as efficiently. The combi boiler is needed for flats and small homes where you cannot fit a cylinder, but don't overlook the horizontal hot water cylinder. I just think of a combi as an overly complicated device that may be self contained but uses proprietry components that offers less flexability in design but great for builders as it is just a simple cheaper installation and keeps heating engineers employed.

 

[Blackswanwood]

We are completing on a new home, which is on LPG, hence my great interest at the moment on heating systems as it’s probably the most expensive system. My present house runs on oil, which is one of the most effective fossil fuel heating sources. Anyway, after I retired I started to run the house at a constant temperature all day long. I anticipated my heating bills increasing as a consequence. I was both surprised and delighted that my use of oil actually on average reduced by around 20~25%! that’s compared to morning and evening heating only.

We have a biomass (wood pellet) boiler with underfloor heating and also find that just letting it run constantly (controlled only by the room thermostats) significantly reduces the amount of pellets used.

 

[Stevekane]

Another bad aspect of the combi boiler, you need a lot of BTU's to get instant hot water but with a system boiler you still get hot water just that it is a gradual process to fill a cylinder, mine takes 20 minutes from cold. So with a combi you will have an oversized boiler for your heating, you are trying to get the one tool for every job but end up with it does every job just not as efficiently. The combi boiler is needed for flats and small homes where you cannot fit a cylinder, but don't overlook the horizontal hot water cylinder. I just think of a combi as an overly complicated device that may be self contained but uses proprietry components that offers less flexability in design but great for builders as it is just a simple cheaper installation and keeps heating engineers employed.

Indeed, we presently have a very old open vented boiler and I did toy with the idea of eventually swopping it for a combi, but decided against it, when (if) I have to change it it will be for another heat only one,,but how well a modern boiler will run on 8mm microbore is anyones guess,,
Steve.

 

[woodieallen]

I'm intrigued why keeping the boiler running reduces fuel consumption. Not doubting anyone...just trying to get my head round as to why.

EDIT: Quick Google shows that it's not the same for everyone and depends on how well insulated your house is

https://www.thegreenage.co.uk/is-it...eating-on-all-the-time-or-turn-it-on-and-off/

 

[Jameshow]

I'm intrigued why keeping the boiler running reduces fuel consumption. Not doubting anyone...just trying to get my head round as to why.

EDIT: Quick Google shows that it's not the same for everyone and depends on how well insulated your house is

https://www.thegreenage.co.uk/is-it...eating-on-all-the-time-or-turn-it-on-and-off/

I'm guessing it's more economical like a car travelling at constant speed is more economical than start / stop driving.

 

[Spectric]

It really depends upon insulation and heat loss, if insulation is low and heat loss high then it is like having the door open and you are trying to heat the garden so leaving the boiler on is pointless, just like having the aircon on in a convertable. If the insulation is good and heat loss low then once you get the house upto temperature all the boiler does is to maintain that temperature, the hard work was getting there in the first place so leaving it on is more efficient. Think of climbing a big hill, all your effort is in the ascent and once you are at the top you can walk round all day long using little energy.

 

[John Brown]

I have to disagree. The only way leaving the heating on all the time could be more efficient is if the boiler is running more efficiently due to being in condensing mode.
Would you leave your kettle on permanently on the grounds that it took a lot of energy to get that room temperature water up to boiling point?

 

[deema]

Well, I have to dispel some of the theories. I relate my house to basically, well, leaving all the doors and windows open. Its solid wall, brick built in 1830, when insulation hadn’t been thought about. Apart from what I’ve put in the roof along with double glazing, it’s got no insulation credibility worth a sheep’s blanket. Equally it’s heated by an oil boiler that was installed around 25 years ago, so no condensing mode. But, I’m defo using 20 to 25% less oil keeping it on all the time and the house at 21C (same temp as we had it at before in stop start heating). A couple of others I know with different era of houses / different levels of insulation have all reported the same effect to different degrees. Why it’s happening, I’ve not a clue! But I’m delighted it is!

 

[MikeJhn]

Have to agree with Spectric and Deema, my house has solid flint walls, can't trace the build date, but there was a building here registered in the Doomsday book, point is no wall insulation, but over 600mm thick, insulation in the loft only, the oil boiler is over forty years old and is amazingly reliable and cheaper to run all day than timed, realised that after retirement, been ten years or so now, so do have a long period to compare consumption as I take monthly readings of the oil level in the tank.

 

[Bingy man]

It’s interesting to read though these posts on the subject of small bore ( 6 8 10 mm) etc . I recall the conversation with the trainer during my time at b.gas as condensing boilers were making a comeback ( yes they were around several years prior to the latest generation ) this trainer was not employed by b. Gas directly and took the stance that condensing boilers were pointless unless the entire system was re- designed around the house where it would be installed. Now I know that 1,000,s of condensing boilers have been installed on existing systems of various designs- 6 8 10 mm pipes, systems with 15mm main circs from the boiler, or large bore circs 1” and above and I’ve even seen a few1 pipe systems with condensing boilers. So who is right , which is the correct method- match the boiler to the house and system or the system/ rads to the boiler. On the same point - I’ve worked in many new build homes built after April 2005 ( mandatory condensing boiler in new builds and replacing existing boilers ) that have small 12-18 kw boilers fitted and all the drops to the rads are in 10mm pipes buried or hidden in the wall’s and small radiators in a modern version of a 3 story terrace house , the heating is split into 2 or 3 zones . Some of these boilers/and systems were installed with a 15 mm gas supply which should of been 22 or a 22 mm supply that should of been 28mm etc . This was always evident when gas rating the appliance ( max capacity of a range rated condensing boiler ) so a 12 —18 kw boiler rated to 12 kw would not achieve its 18 kw max setting.

 

[John Brown]

Well, I have to dispel some of the theories. I relate my house to basically, well, leaving all the doors and windows open. Its solid wall, brick built in 1830, when insulation hadn’t been thought about. Apart from what I’ve put in the roof along with double glazing, it’s got no insulation credibility worth a sheep’s blanket. Equally it’s heated by an oil boiler that was installed around 25 years ago, so no condensing mode. But, I’m defo using 20 to 25% less oil keeping it on all the time and the house at 21C (same temp as we had it at before in stop start heating). A couple of others I know with different era of houses / different levels of insulation have all reported the same effect to different degrees. Why it’s happening, I’ve not a clue! But I’m delighted it is!

Maybe you should turn it up to 25C, who knows, it could start putting oil back in the tank?

So what happens if you go away for a week? Do you leave the heating at 21? How about a month? Or a day?

 

[deema]

Maybe you should turn it up to 25C, who knows, it could start putting oil back in the tank?

So what happens if you go away for a week? Do you leave the heating at 21? How about a month? Or a day?

I leave it on. It’s never off. Are we a tad ereked for some reason?

 

[John Brown]

It really depends upon insulation and heat loss, if insulation is low and heat loss high then it is like having the door open and you are trying to heat the garden so leaving the boiler on is pointless, just like having the aircon on in a convertable. If the insulation is good and heat loss low then once you get the house upto temperature all the boiler does is to maintain that temperature, the hard work was getting there in the first place so leaving it on is more efficient. Think of climbing a big hill, all your effort is in the ascent and once you are at the top you can walk round all day long using little energy.

The hill climbing analogy doesn't work for me, as the rate at which your house loses heat is proportional to the difference between the inside and outside temperatures. There is no part of being on top of a hill that that replicates this(unless it's such an altitude that you can't breathe easily, but that's another story).
The only possible reasons, from a scientific as opposed to anecdotal perspective, that I can find for this phenomenon you have observed are
a) a condensing boiler or heat pump system, where better efficiency is achieved at a lower water temperature.
b) moisture condensing in the house and/or walls, that needs to be evaporated each time the heating restarts. Apparently condensation in the walls could reduce the insulation effectiveness, which I accept, but the same source also refers the the latent heat of evaporation, which I suggest would be cancelled out by the enthalpy of condensation.
Both a) and b) would have a break even point that would depend on many factors.

So if anyone has any scientific insight into why it is cheaper to run the heating 24/7, then please have at it.
I would love to be wrong!

 

[John Brown]

I leave it on. It’s never off. Are we a tad ereked for some reason?

I don't know that word, but probably not.
But you'd seriously leave your heating on at 21c if you went away for a month? Is that because you think it would be cheaper, or because you are.very well off and don't subscribe to the climate change theories?

 

[deema]

I have almost twenty years of data on my oil consumption, with six of those now I’ve been retired. I earned my corn as an engineer, and would like to think I have a fairly good understanding of most engineering principles. I understand heat gradients etc, and logically selective heating should be more efficient. However, after a little experimenting, running at a constant temperature (it is lower at night 17C, but not off) and heating our unused rooms is more efficient that keeping unused rooms cool and selective timed heating. The one thing I can’t argue with is the reduction in oil usage, with everything else remaining constant. Ie boiler, piping, radiators etc.

 

[deema]

I don't know that word, but probably not.
But you'd seriously leave your heating on at 21c if you went away for a month? Is that because you think it would be cheaper, or because you are.very well off and don't subscribe to the climate change theories?

Yes, I’d leave it on. I’d turn it down to 18C, but no lower. From measuring oil usage I’ve found going away in winter for two weeks and turning tge heating right down when I’m away causes some to use a lot more oil to heat the hiuse up again when I return. The average is more than if I leave it on slightly lower. I did a Taguchi factorial experiment over a few years to check I wasn’t kidding myself.

Im a Yorkshire man, so hanging onto the coin is my first priority.

 

[John Brown]

I have almost twenty years of data on my oil consumption, with six of those now I’ve been retired. I earned my corn as an engineer, and would like to think I have a fairly good understanding of most engineering principles. I understand heat gradients etc, and logically selective heating should be more efficient. However, after a little experimenting, running at a constant temperature (it is lower at night 17C, but not off) and heating our unused rooms is more efficient that keeping unused rooms cool and selective timed heating. The one thing I can’t argue with is the reduction in oil usage, with everything else remaining constant. Ie boiler, piping, radiators etc.

You didn't mention the 17C setback in the previous post, but all I can say is that I'm envious.

I would still like some scientific theory or speculation as to why this could be the case.

 

[deema]

@John Brown Why not try it for say a week Or two Compare week on week gas useage from the meter or from a smart meter if your on gas.

 

[John Brown]

I have Wiser wireless valves on nearly all the rads, and Octopus provide historical usage data, and the last time I checked we were using about half as much gas compared with a year ago.
Spent more on gas, though, and logs.
To be honest, there are too many variables for me to do a simple comparison. Sprawling house, part of which is a 400 yr old barn, daughter and grandchildren in the newer part, leaving doors and windows open at random, weather.