Energy myth-busting: Is it cheaper to have heating on all day?

grahamc2003

Malc, and the final paragraph of mine?... repeated in shorter form below, no obligation to answer of course. Something really doesn't make sense in all this, just trying to clarify the inconsistencies in my mind.

I'm just curious. Did you get your C.Eng via the BCS? If not, mind me asking which professional body you got your C.Eng through?

malc_b

Cardew wrote: »

malc_b

This was your reply!

On any modern system the water max temperature dial on the boiler should be set to max and left there.

Do you stand by that statement?

P.S

Not what you do with your non-modulating non-condensing oil boiler.

Which you are taking out of context and excluding the however that follows it! What I said was:

Coal: Set it to minimum workable since it controls tick over (and DHW). It's likely this will have to go up in winter so the radiators have enough output to keep the house at temperature.

Oil and non modulating non condensing gas: Set to max as all it does is cut off the boiler causing short cycling.

Modulating non condensing gas: Very little difference between max or min. Slightly more efficient to have a lower water temperate (and safer for toddlers and for DHW where there is no tank stat). Likely to need to be set higher in winter to meet house loss so could just set it high always.

Modulating condensing gas: (I assume stat modulates flow so) more efficient to have a lower water temperature so operates in condensing mode. May need to set that higher in winter to meet house requirements. May not have any effect since it takes a while to heat up the rad water so short burns might not reach dial temp anyway.

I trust that clear now I've split it into the different boiler types rather than starting from general case and then refining that for exceptions.

malc_b

grahamc2003 wrote: »

Malc, and the final paragraph of mine?... repeated in shorter form below, no obligation to answer of course. Something really doesn't make sense in all this, just trying to clarify the inconsistencies in my mind.

I'm just curious. Did you get your C.Eng via the BCS? If not, mind me asking which professional body you got your C.Eng through?

If you must... the letters after my name are BSc(Hons) CEng MIET MIRSE so my CEng is because I'm MIET, (or MIEE as was). But I only mentioned it to correct the suggestion that I didn't understand the maths.

oldskoo1

Malc thanks for your input to this discussion, you have bought a slightly different angle to this thread and explained some of the reasoning behind parts of this debate.

It's interesting to know the costs for different scenarios. Ultimately timed does work out cheapest. I conducted this experiment, moving from timed to 24/7 about 4 years ago when my daughter was born. I kept the house at 18c. The first year we did see increases of around 14%-15% but the second year we turned it down to around 15c overnight. Consumption was only up 8% on timed. The difference really wasn't as much i expected.

I ran micro tests, week by week using different methods and i achieved similar results as i tried the factor in weather too.

At our new current house i repeated these micro experiments and found similar results. So 24/7 (with simulated off at 12c overnight) has produced only marginally more gas consumption than timed. I may even try keeping the temp around 15c overnight. The comfort is worth the extra £5-£10 per month.

The final piece of the jigsaw for me was trying to get my heating running efficiently. After 2 months of a broken boiler, it is now fixed. It's an older non condensing model and i've managed to get it running at just a tad under max and pump speed 3 and it rarely cycles. I have to run the ch all day as I am home, i still get blistering hot rads so will see how it goes.

I can see that if someone is trying the always on method in a drafty, poorly insulated house they may find their gas usage does increase more.

wantanswers

I replaced my old boiler about 4 years ago with a Condensing Boiler (not Combi) and never really paid much attention re flow temperatures.......

I will in future, and thanks malc you've posted some interesting 'Practical' information.

Cardew

malc_b wrote: »

Which you are taking out of context and excluding the however that follows it! What I said was:

Coal: Set it to minimum workable since it controls tick over (and DHW). It's likely this will have to go up in winter so the radiators have enough output to keep the house at temperature.

Oil and non modulating non condensing gas: Set to max as all it does is cut off the boiler causing short cycling.

Modulating non condensing gas: Very little difference between max or min. Slightly more efficient to have a lower water temperate (and safer for toddlers and for DHW where there is no tank stat). Likely to need to be set higher in winter to meet house loss so could just set it high always.

Modulating condensing gas: (I assume stat modulates flow so) more efficient to have a lower water temperature so operates in condensing mode. May need to set that higher in winter to meet house requirements. May not have any effect since it takes a while to heat up the rad water so short burns might not reach dial temp anyway.

I trust that clear now I've split it into the different boiler types rather than starting from general case and then refining that for exceptions.

This is yet another example of your backtracking and attempting to cover up.

Out of context? what you stated was;

By this I assume you mean the water temperature dial on the boiler and not the hall thermostat?

On any modern system the water max temperature dial on the boiler should be set to max and left there. The only exception would be something like a coal fired system where the boiler is always lit and the thermostat controls the tick-over rate too. Then you'd turn the dial down in Spring/summer/autumn to lower the tick-over.

The lower you have the dial set the more likely it will operate and cause the boiler to short cycle. That is the hall thermostat is demanding heat, the water is up to temperature but the
house isn't yet warmed so the pump is still running. The boiler stat cuts the burn then 2 minutes later it burns again, briefly, then the boiler stat cuts out again, etc.. That mode of operation is best avoided as it is inefficient.

This applies to modern oil boilers and similar gas boilers.
There are modulating gas boilers which might be different. I'm not familiar with those and maybe the dial modulates the burn rather than cutting in and out. It is the cutting in/out you want to avoid.

Note: You stated On any modern system.

The majority of 'modern' systems are gas condensing and modulating. So having posted rubbish you have now realised you were wrong and have added the phrase in red(in your quote) which was conspicuously absent in your earlier reply.

grahamc2003

malc_b wrote: »

If you must... the letters after my name are BSc(Hons) CEng MIET MIRSE so my CEng is because I'm MIET, (or MIEE as was). But I only mentioned it to correct the suggestion that I didn't understand the maths.

Thanks, inconsistencies resolved. (Btw, I didn't suggest you don't understand the maths - it's your thermodynamics knowledge which you don't appear to realise is at quite a superficial level, which is now understandable). I only mention this because it's incumbent on chartered pros to speak with authority only in their own areas of expertise.

malc_b

grahamc2003 wrote: »

Thanks, inconsistencies resolved. (Btw, I didn't suggest you don't understand the maths - it's your thermodynamics knowledge which you don't appear to realise is at quite a superficial level, which is now understandable). I only mention this because it's incumbent on chartered pros to speak with authority only in their own areas of expertise.

So because I do a rough "back of fag packet model" with approximations to make it simple I now have a "superficial level of thermodynamics knowledge". A model and maths for which you have not pointed out any major flaws I should add, and which is just designed to give a ball park figure.

Without taking measurements any calculations are just an approximation anyway and the calculations done for house loses are simple and just use basic thermodynamics. In fact they don't even consider energy storage in house fabric AFAIK.

Plus, I would add that I've never claimed I'm an expert so listen to me. You assumed and implied I had no idea what integration was just because I used a simple a model to illustrate a point. I corrected that assumption by listing some of my relevant qualifications. In my opinion assuming someone's lack knowledge is bad manners, I think one should assume the person replying has a reasonable level of education rather than starting from the assumption you're the only one that knows integration.

Perhaps you should google hot water freezes faster than cold, aka
the Mpemba effect, named after Tanzanian student Erasto Mpemba. Although a student who pointed out a fact that the pro's over looked as the phenomenon seems contrary to thermodynamics. It sticks in my mind as we covered it during my physic degree, and I jumped to the obvious conclusion. A mistake I've tried not to repeat in the last 40yrs but rather keep an open mind and consider the maths on its merits rather than jumping to the obvious.

So let's limit the discussion to the facts of the modelling rather than being personal. Are there any serious mathematical errors which would radical change the figures (remembering that it is just a ball park figure we are aiming for).

malc_b

Cardew wrote: »

This is yet another example of your backtracking and attempting to cover up.

Out of context? what you stated was;



Note: You stated On any modern system.

The majority of 'modern' systems are gas condensing and modulating. So having posted rubbish you have now realised you were wrong and have added the phrase in red(in your quote) which was conspicuously absent in your earlier reply.

So you presumably have fact and figures to back up that the majority of modern systems are modulating gas condensing? You may well be right, it's not my impression but then I have a limit set of cases.

And if you read what I said completely you see I included the fact that I thought modulating could be different and that the key point was to not have the boiler short cycle. On oil, and gas (except for condensing and modulation) setting the dial to max is either better or makes no significant difference.

Do you want to contribute to a discussion or just pick holes in what I said or didn't say? I'm quite willing to revise my opinions in the light of reasoned argument. And I admit that I could have set out the various burners and options better as I have now.

Whether or not you set the dial on lower on condensing modulating gas is moot. There may be a gain to having a lower dial temperature but equal that might actually make no difference. It would depend on the burn time as short burns will not get the water up to max anyway so it wouldn't modulate. Long burns you'd require in winter and then you might have to raise the dial temperature to get enough heat into the house. Especially if the condensing boiler is a retrofit to old radiators so with insufficient radiator area.

bestyman

I`m having trouble keeping up at the back.