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Ummm.
You know a log burner is heating right?
Which is less bad from efficiency perspective- low temp and cycle more or high temp and cycle less?
Pretty similar to you Edward- I keep the kids bedroom warm in the night in the vein hope it helps them sleep better!
Not sure I follow the connection between short-cycling and lower temperatures; surely short-cycling is a function of thermostat offset, rather than temperature?
I’m not sure either ..but if the temperatures are lower then the boiler takes less time to reach the flow temp and so then switches off, but if the room isn’t up to temp it then comes on again after not long and repeat. Whereas higher flow temp the boiler runs full tilt and room heats up quicker so maybe less cycling?
This guy says you shouldn’t lag your indoor pipes as can reduce boiler efficiency. Any thoughts?
Your rooms don’t all have the same heating requirements. Our kitchen and hallway are cool due to the doors, floor and the fact it’s on the ground floor; but the living room above them is fine. Unlagged pipes in the ceiling void put heat into the living room where it’s not needed instead of the kitchen where it is.
As for boiler efficiency – you do need to be able to dump enough heat to have a low return temp. But unlagged pipes are the same effect as slightly larger radiators, except you can’t control where the heat goes.
As always – it depends.
In short, boiler efficiency is sort of irrelevant compared to total heating system efficiency. Useful output is hard to calculate though since as above it's the heat transferred to the rooms you need heating
Not sure I follow the connection between short-cycling and lower temperatures; surely short-cycling is a function of thermostat offset, rather than temperature?
When a boiler is oversized for the heat that is required, or can't reduce its output adequately, the temperature of the returning central heating water is so hot that the boiler thinks it's done it's job and it turns off the burner.
This means the boiler can't get anywhere near its dew point for recovering latent heat, and maximising its efficiencies, and it will need to fire up again fairly shortly because insufficient heat it lost from the rads into the room due to the short burn time - you get repeating firing events which adds wear and tear into the boiler.
No, I switched the boiler a year ago to one that will modulate down to 1.5kw. I alao have quite large radiators.
Nice. I can't splash for a new boiler currently but bigger rads might be on the cards in some rooms. I figured that the efficiency gains from a colder return temp would not pay for a new boiler very quickly.
Not sure I follow the connection between short-cycling and lower temperatures; surely short-cycling is a function of thermostat offset, rather than temperature?
Muddyjames has it right. There are two reasons for short cycling. One of them is as you say - if the on and off temp of the thermostat is too close then it will be short cycling.
However in the other case, if I set my flow temp to 50 then the rads are at 48 or so. The heat output of the radiator is therefore lower so it takes longer for the room to hear up and the stat to switch off. Ideally, the boiler would heat up the circulating water to 50C and then turn itself down so that it stays at 50 and the return temp at say 30. But for that to happen the heat input of the boiler has to equal the heat lost by the radiators. When they are at 47C the heat lost is lower so the boiler has to turn it's flame down to match that. But many boilers can only go so low. Mine has a minimum of 9kW so 9nce that 50C is reached it has no choice but to switch off. The flow temps then drop towards to the return temps. But because my boiler is shit, it sees the temps drop and goes "oh, better start up again" within a minute or two.
The only way to stop this is to increase the flow temp so that the rads can dump 9kW of heat, or fit bigger rads so they can dump 9kW at the lower temps. I can increase the flow through the rads to make them hotter, but whilst they emit more heat, more heat is going into them to begin with, so the return temps are higher. The boiler is simply adding to the return temps, so it reaches its target temp more quickly! And then the return temp is higher so it condenses less well.
When it was cold, the rooms would not heat up fast enough so I had to set the flow temp to 60C. The cold weather didn't mean my radiators were dumping more heat since although it was -4C outside it was still 16C inside just as it is when it's 10C outside. It did mean that they needed to run for longer though, and more frequently.
Now that it is warmer, I could turn the flow temp down, but that makes it take longer to warm the room. I have to position the thermostat so that it will warm up and switch off before the flow temp exceeds the set value and it short cycles. But if it shuts off too soon in the hallway the other rooms have not got up to temp!
So I have to adjust the flow temp, flow through the hallway rad and the distance from that rad to the stat to keep the return temps as low as I can whilst avoiding short cycling and giving the other rooms time to warm up!
When a boiler is oversized for the heat that is required, or can’t reduce its output adequately, the temperature of the returning central heating water is so hot that the boiler thinks it’s done it’s job and it turns off the burner.
Mine shuts off based on the flow temp not the return. Mine is still condensing, with the return temps slowly climbing to 42C or so because the flow tops out at 65C. If I increase the flow temps then the room heats faster so no short cycling, but the return temps are 50C or 55C. So it's a toss up which is less efficient - short burn times or higher return temps.
It also matters what temp the stat is set to Vs the TRVs in the rooms. If they shut off, then the system can dump far less heat so short cycling is more likely. But the rate of heat loss is different for different rooms, but the heat input from our activity is the same, so when it's colder I theoretically need different parameters to when it's mild. And when it's cold and the air has been heated more the relative humidity is lower in the house, so I need lower temps to feel comfortable and perversely higher temps in the house when it's mild.
Argh!
So many people buggering about with boilers and CH but none claim to be heating engineers.
Call me old-fashioned but I would stick with people who do this stuff for a living - aka 'experts'.
£390 for the month so far. £1700 for the year but it would appear most of that is the past few months.
‘’So many people buggering about with boilers and CH but none claim to be heating engineers.
Call me old-fashioned but I would stick with people who do this stuff for a living – aka ‘experts’.’’
With all due respect I really don’t like attitudes like this. And it’s common in many formats. People are just trying to help themselves a bit and share new found knowledge. You don’t have to be a mechanic to diagnose a flat tyre.
I reckon we’ll be on ~£220 for December including wood. 3 bed, mid terrace, solid wall 1880’s build. Thermostat at 18 daytime and 14 nighttime.
I used to think it was pretty inefficient but this thread has changed my mind dramatically. Even in the really cold snap with -5 overnight we were only loosing ~3 degrees overnight, on normal nights it’s more like 1.5 degrees.
Call me old-fashioned but I would stick with people who do this stuff for a living – aka ‘experts’.
You are old fashioned. A lot of 'heating engineers' are people who were just fine with boilers when they were just an on/off thermostat and that was it but they struggle with modern heating systems where you have to estimate the thermal mass of your house in order for the control system to work. On a similar theme I just had a quote for solar panels but the 'expert' completely missed the fact that our house requires a three phase inverter rather than single. The person who proposed our underfloor heating didn't want to insulate over the concrete beams because 'heat goes up you know'. It never hurts to do a bit of research yourself. I would love to believe that everyone in a profession is an expert but it really isn't true.
but the ‘expert’ completely missed the fact that our house requires a three phase inverter rather than single
What makes it require a three phase inverter ? Are you hooked up to all three phases in your house. That would be very unusual.
What makes it require a three phase inverter ? Are you hooked up to all three phases in your house. That would be very unusual.
It is unusual but i am. The oven is on all 3, various other parts on the house are on different phases. I have to add though that i am in Brussels and we are a bit unusual in that not only is it 3 phase it is 3 phase delta.
With all due respect I really don’t like attitudes like this. And it’s common in many formats. People are just trying to help themselves a bit and share new found knowledge. You don’t have to be a mechanic to diagnose a flat tyre.
Yeah, My friend was complaining about heating prices, I tried explaining a bit about flow temp, told him about the heat geek YT channels (hes an avid YT watcher)..and he's like, my boiler only has one dial, not seperate ones for water and CH... I was like really? you sure.. he went to look... "oh yeah, there's 2 dials".
I said turn your hot water down to 40c (combi/condenser boiler), there's no point having scalding hot water comming out of the shower head only to have to mix back down with cold.
The response? "nah, I can't be bothered messing about with it"
He literally has no idea how to use his boiler and doesn't seem to care, but does care about his high bills ¯\_(ツ)_/¯
Equally, wallking around my neighbourhood the other day having a nose at peoples flues - the number of houses with huge plumes of steam errupting from them was staggering.
That flow temp pointer above is one of the most useful things I've ever read on here!
I never though about it before but I always mix down the shower with cold, just checked, the hots set to a scalding 60c, I've just wanged it down to 45c and I'll go from there
Thanks!
^ that's OK if you have hot water on demand but ours comes from a cylinder, and with daughter and wife in particular taking long hairwashing showers they can deplete the cylinder sufficiently that by the time son and then me get showers they're lukewarm or even cold
By having the water hot, they use less / cut it with more cold that is unrestricted supply and I've at least then got a fighting chance.
I might look at adjusting when she goes back to Uni and then adjust again when back, it would be interesting to see if it has any impact on bill / usability.
I’ve just wanged it down to 45c and I’ll go from there
You might want to put it a bit higher. I know that my boiler has a feature where if the water tank temp is as low as that for a few days then it will crank it up over 60 once to prevent legionella
Managing legionella in hot and cold water systems (hse.gov.uk)
I don't know how much of a real issue this is. I just know that my boiler has a feature to avoid this and also the link above. I also did some measurements over a few weeks with the temp set at 58 and also down at 45 and didn't find that I saved a detectable amount of gas. My tank is well insulated so it takes a couple of days to cool down on it's own so that may help.
One point possibly worth mentioning on flow temps is legionella. I’ve no idea on the real risk of legionella but it is something that comes up when lowering flow temps , particularly if you have an indirect hot water cylinder.
The point on experts is one that irks me a lot. So far I’ve not met a heating engineer who doesn’t wang the flow up to 70. Similarly when recently having windows installed- being told that the fitters have “been doing it for 20 years” and so “know what they’re doing”- Problem is they’ve been doing it wrong for years. The other problem is there are so many variables and no arbiter even if you had a new heating install, you won’t have any come back if they’ve set it up to run inefficiently at 70.
There's a heat geek article about legionella.
Call me old-fashioned but I would stick with people who do this stuff for a living – aka ‘experts’.
The problem with people who do this for a living is that they don't need to be a tual experts they just need to know a bit more than the people whose heating they are working on.
Qualified plumbers fitted my pump backwards, left the flow temp on max, didn't bother balancing the system, fitted the stat too close to the rad, over-specced the system, fitted a shit boiler, and later didn't open up the boiler to clean out the condensate and subsequently discover a problem.
I wouldn't mind paying someone to look at this stuff if I could be sure they knew what they were doing. The guy I got in to service the boiler didn't even bother coming to his followup appointment or even respond to his messages.
The concept behind heat geek seems to be to sell services from people who actually understand the engineering behind how to set up heating properly. And not every plumber does. There are several examples on this thread.
So yeah with my Physics degree, my professional diagnostic skills, my DIY experience and the internet I'll have a look at it myself and tune what I can. I know enough to know when to stop. I'm not touching the burner or the gas side for example.
That said, possibly the biggest difference between a plumber and me is that I live here, so I can spend as long as I want fine tuning this particular house and learning how things respond. A hired plumber can't do this.
Mines a Worcester Greenstar combi so no tank, just showered at 45c no mixing, still felt a touch hot for me.
There's only me using it luckily
Mines a Worcester Greenstar combi so no tank, just showered at 45c no mixing, still felt a touch hot for me.
There’s only me using it luckily
Yeah mines a pretty new Baxi combi - i still blend a tiny slight touch of cold in, HW set at 40c as thats as low as it will go.
Less steam too so better for the bathroom humnidity/dampness.
Equally, wallking around my neighbourhood the other day having a nose at peoples flues – the number of houses with huge plumes of steam errupting from them was staggering.
Silly question perhaps, but what does this mean please? I see a good blast of steam emit from my flue when the boiler fires up - is this not right?
I have both dials (rads flow temp and hw) set to 12 o clock, which I suspect is 55c ish?
I've run a mini-experiment over the last couple of days where we've had reasonably comparable outside temperatures.
I haven't changed any of the TRV settings - all set to #3.
There is no separate thermostat to control boiler at all. (Usually runs off the timer.) 6 year old Baxi platinum 28.
Xmas day - had boiler set to '48' and ran it for 8 hours 10-6pm. Temp stable at 18ish degrees (+3 showers on HW from boiler - no tank).
Yesterday - had boiler set at '65' (as per Baxi booklet) and ran for 2 hours in the morning 9-11. Temp achieved was 19.4 degrees and dropped to 15.7. CH back on for 2 hours later 5-7pm (+2 showers on HW from the boiler).
Gas cost yesterday was £1-ish more than Xmas day's total.
No idea what this means, other than it seems cheaper to have the boiler on for longer at lower requested temp than shorter for higher requested temp. Now thinking a thermostat of some variety might be the answer, though, given our CH is generally not in use April thru October, the cost of the stat plus person to fit it all probably is more than the saving. I've rambled enough now, and confused myself further. I reckon I'll save an absolute bloody fortune if I just stop thinking altogether!
🤔😂😂😂😂
Silly question perhaps, but what does this mean please? I see a good blast of steam emit from my flue when the boiler fires up – is this not right?
Yeah you will see some steam, but some of my neighbours look like a constant volcanic eruption on one of Jupiters moons, sugesting they've not done any optimisation of the boiler.
Silly question perhaps, but what does this mean please?
There is water vapour in the natural gas along with methane and whatever else, o when you burn it one of the byproducts is H2O which on a cold day condenses into the steam you see. Your boiler is designed to condense some of that steam inside it whch recovers more heat fro the gas. The better the set up, the more steam is condensed and the less you will see coming out. But also, the less gas being burned, the less steam there is to begin with.
So a system to hat hasn't been set up well will produce a lot of steam because it's not condensing, and not running efficiency either. The above poster has a boiler that can run super low which is both not burning much gas and also condensing very well. But it is probably burning for much longer. The efficiency savings for setting up the flow temps and rate correctly are probably 20%, from best case to worst, I'd say.
That's impressive that my oil boiler gets water vapour out of the gas .
Why are you burning oil at all trail_rat? Surely the hot air coming out of your mouth is enough to heat your home?
That’s impressive that my oil boiler gets water vapour out of the gas .
H2O is a product of combustion, irrespective of the source.
Call me old-fashioned but I would stick with people who do this stuff for a living – aka ‘experts’.
But how do you know they are?
I went through 6 local 'heating engineers' before I found one that actually knew more than just how to bang a new box on the wall and connect the pipes.
Most of these people know what they know, but dont know why it has to be done a certain way.
I'm fortunate as a former Domestic energy assessor, it was pretty easy for me to put out some of the lingo and see how they responded.
We gave in during the cold spell.
-8 during the day.
£239.00 for the last month, central heating on for less than 10 days.
Gt absolute f.
We need to embrace our inner children and get used to ice on the inside of the windows. We've gone soft.
H2O is a product of combustion, irrespective of the source.
Correct. But my (tongue in cheek) point still stands.
My comment was really for the benefit of others...😉
But my (tongue in cheek) point still stands.
Your point was that you don't have gas? But the person I was addressing does.
Not putting the heating on is going rather well seeing as it's been broken since the 19th and isn't going to be fixed until Jan 5th. I'll never take heating and warm water for granted ever again. Properly fed up with being cold all the time in the house especially over Christmas. ☹️
We can fix it remotely.
Tell us what's going on, or isn't.
Have it fired up in no time.
Or possibly wait for a plumber to come out and scratch his arris and tell you itsca 3 dayv wait for a new pcb from the merchant and it will be £205 plus fitting, plus vat.
What’s the best additional insulation to add to the hot water tank? I see there are loads of covers available which wrap around the tank, but they can’t all be the same?
Is your tank not pre-insulated?
So a system to hat hasn’t been set up well will produce a lot of steam because it’s not condensing, and not running efficiency either.
Thanks Molgrips. So is inefficiency something that can be identified/calculated by simply seeing a lot of steam (which was how I took the initial comment I responded to)? I ask as I've previously read up on the flow temp advice and have dialled mine back to (I think) 55c, but still occasionally notice the boiler bellow out steam. I assumed this is correct operation, but now wondering whether I should be seeing less steam, and whether it's currently a sign that I should be turning the flow temp down further. I guess it's a case of finding the balance by trial and error - turning the flow temp down as far as you can until the house is struggling to heat. But the flue will always kick out steam regardless?
As mentioned elsewhere in the thread, there's a need to know things are running as efficiently as your system can, rather than just working to kick out heat.
The tank is pre insulated, but I do believe it would benefit from some further insulation as the insulation feels warm to touch.
So is inefficiency something that can be identified/calculated by simply seeing a lot of steam
No. There will likely always be steam. In theory with a low enough return temp you could get rid of much of it, but you probably won't be able to run your system that low for other reasons.
There will always be an amount of steam, but the quantity can be used as a proxy for whether your boiler is condensing well or not.
When mine is running the heating, theres the faintest of wisps that dissipates almost immediately, and when its heating the cylinder, it runs at full bore and chucks out noticeably more. (Hot water priority setup and a system boiler)
Pretty much it tells you nothing else about the system though.
£239.00 for the last month, central heating on for less than 10 days.
Sounds like you need some insulation. Ours was set to 18-20 degC all day every day and only hit £175 (ouch) on octopus variable tarif. That's a rental 1930 ish 3 bed semi. YMMV if you aren't on a gas supply / much bigger house etc
My supplier asked me to increase my direct debit several months ago, to allow for energy price increases, so I upped it to slightly above what they asked for, £170/month. I’ve got the system set at 17°/12°/15°/12°/16.5°/14°, highest first thing in the morning, lunchtime and evening. Just checked my latest bill, and I’m £196 in credit…