Great video Allan You try telling a customer they need a new boiler and all the rads replacing as there too small and the temperature will be set to a max of 55 degrees most jobs will jump £1250 - £2000 extra for rads and I bet the price for the big rads with go through the roof.
But will they? What if calculations were made on a typical install from scratch calculated 30 years ago. No cavity wall insulation, single glazing, no draught proofing and minimal loft insulation. I know my energy bills now are lower than they were 15 years ago despite inflation.
With bigger radiators, there is a higher volume of water for the boiler to heat (although at a lower temperature). So is more gas being burnt, or effectively the same amount? Where is the savings?
Great video as always. But with system or heat only systems with unvented hot water cylinders with legionellia requiring storage at 60 Degrees. Only boilers capable of firing at two different outputs with DHW priority, weather comp will give the best efficiency... Intergas exclusive and the other one aswell as viesmen can fire on full output to recharge the Hot water cylinder on DHW priority then modulate right down to the heating systems heatloss... But as you say everything starts with a accurate heat loss calculations!
Just fitted new boiler in my house , flow temp set at 55 , spent time insulating and draught proofing . Boiler still offers quick heat up time as I’m not home much .
Couldnt agree more with what you said about manufactures needing to drop down their minimum modulation, its not like they didnt know in advance, and yet their minimum in some cases is way above your requirements even on their smallest boilers, Baxis I looked at were way above what I needed.
I have already been doing this on an ad hoc basis in my own old house for some years . Installing the Weather Compensation kit on my heat only boiler reduced the flow temperature, and modulates it. I changed my existing single row emitters to double or even triple row so they run cooler but give out the same heat. The only thing that keeps the high flow temp is the hot water cylinder circuit..because it has to. The weather comp electrical circuit allows that. I fitted a Magnaclean about a decade ago. The system works OK, but it does take some getting used to cooler radiators. I also enabled the optimisation feature on my budget Center Brand programmable room stat ( it's a Honeywell underneath). I don't think that with the heat loss profile of my 1885 solid stone house I could get a heat pump to work well without major works to improve the insulation. We are thinking about how to improve insulation affordably over and above what we have managed up to now. My budget is not endless now I'm retired ( from heating). I wonder how my old Mears heat loss calculator would stand up these days😉
I have a 1930s solid wall (no cavity) home, mostly installed with insulated plasterboard, loft insulation, old double glazing, suspended floors with no insulation. Approx 2000 sqft, 16 rads (new, convector type). I oversized the rads by assuming in the calcs the walls were still solid brick with no insulation. The boiler is an Ideal Logic 30+ combi (zoned off for an unvented cylinder). The Drayton Wiser controls are set to Opentherm modulation. During colder months the heating is set to 19.5c from 6.30am to 10.30pm. Over night it's set to approx 17c. I find that first thing in the morning (when the house is coldest) the boiler fires at 65c to 70c, given demand is highest. Once 19.5c set temp is reached the boiler modulates down to 40c to 50c (or lower, if not to cold outside, I've seen as low as 35c). At flow 50c return temp is about 35c. At flow 35c return is about 30c. (I've never been able to reach delta T of 20; is it normal that the lower the flow temperature the smaller delta T gets?). The house stays toasty and warm, the boiler super efficency shows as 72% (which I believe means it's in maximum efficiency / condensing mode 72% of the time). The boiler rarely fires over night, I figure this is because all of the internal walls are solid brick and act like very large, low temp, storage heaters - releasing heat over night. I'm guessing new regs don't take this into account (given new builds are mostly stud wall etc). Really enjoy your videos, very informative!
Good Video Allen. Can you do a small list of combi boilers that can be range rated lower in the settings. I've installed a few Baxi 800's and they have no way of adjusting them in the settings menu. 👍🏾
Good ,informative video ,thanks for your hard work over last few years. Review and more detailed comparison of low modulating boilers and open term controls , which are on the market, will be helpful (as long as not sponsored by the manufactures). .Heard lot of good about Intergas (and lot of bad so we had never installed them..)
Your summing up pretty much mirrors my thoughts. Question for you: For me as someone who works on ALL fuel types, do these regs apply to oil and S/fuel boilers also? As neither of these are modulating.........
I'm looking to install a new combi boiler. We have 10 rads and one shower fed off the boiler. Semi detached 4 bed house originally 3 (had a room made in the loft). Current boiler is 28kw and has lasted us for over 10 years with no problems. Was looking at a Main eco 30 or a Baxi 636, any other recommendations?
Thanks, another really informative video. I still find modulation confusing, surely when the water gets up to temp the flame then turns off but the pump keep running, or does the flame stay on but just down to that lower kw? I have a 40kw Baxi combi which for most of the winter I've managed to run at 55c flow already, just about got away with it but heat up from cold probably too slow for most people. Thanks
Radfoo good morning, you will probably find later in the eves that your boiler would stop start a lot (it is called cycling) as it is not capable to modulate as low, if it makes sense. I have a 33kw one, and later on in the eve is on off like a yoyo 🙄
Dont be confused with water temperature as modulation even though its part of it, You can turn any boiler stat down so that the system water isnt heated too high and that doesnt make your boiler efficient, the modulation part on *modulating boilers* is actually dependent on the temperature across the flow/return when the boiler gets close to its target stat temp the fan speed that sucks the air and gas into the burner will slow down and suck less air gas in, pretty sure i have seen modulation as low as 1:8 so 8 times lower than the maximum heat input for example a 30kw would go as low a 3.75 kw Been a while since i refreshed my knowledge on this stuff so apologies if some of that isnt quite exact..
@@cvplumbersandheating I also have the Baxi 830 and found that setting the boiler temp to 55 degrees, it cycles much less. Hmm. I have 10mm microbore and 9 rads. I use a Danfoss thermostat with the modulation setting optimum for a condensing boiler.
hi Allan,Great videos.Just wanted to ask, with the implementation of these regs and there is non compliance when installing new systems ,Will it affect the ability to sell that house and how will it affect landlords? if it all. Thanks
I was wondering that too. So I found this out: "When you reduce the mean water temperature of a radiator its heat output *does not reduce linearly."* eg reduce mean water temperature by half, results in *less than half* of the heat output. As there is a non linear reduction a 'correction' factor needs to be applied from a table: Delta_TCorrection: DeltaT. Correction Factor 20 0.3 25. 0.41 30. 0.52 35. 0.63 40. 0.75 45 0.87 50. 1 These corrections are from 20/50 ^ 1.3 25/50 ^ 1.3 etc, rounded up to two decimal places. You'll see the 0.41 (0.406 used in chart in the video) For the heat pump 32.5/50 ^1.3 = 0.57 (which isn't in the chart above, but it shows how such a chart is calculated) HTH
unefficient S plan systems must be replaced with DHW priority. As having one flow temp of 65 Degrees to heat up the stored water is a waste of energy when most properties heat loss is 7 to 9 KWH and would run much more efficient at a lower flow temperature. I suppose mixed and blended curcuits would be one way of doing it as well as priority DHW and a boiler that can fire on two heat outputs :-)
Morning Alan. I may have misunderstood the new regulations but I can’t see how an existing system designed for the higher flow temperature can have additional radiators added that work at the lower temperature. Also, are towel rads going to become obsolete?
Hello David.. Good point, possible solutions could be :- Trv on the new radiators that will be too large for a 70 degree flow temperature will heat the room quickly and switch off earlier than te others ? Adjust the balancing of the radiator. Slow the flow excessively to reduce the average temperature flow /return - may deal with it. Good luck finding a lockshield valve that will reduce enough and reliably ! I'd be interested in your thoughts ?
I called my local building control about the new part L regs. I was told that they need full designs and heat loss calcs for all new builds, this need to be backed up by photographic evidence that the work has been carried out as per the design. For extensions they will also require Heat loss calculations but photographs are not required. For upgrade work we are required to change radiators so that they will work at the 55c design temp. If the older parts of the house do not conform to part L, we are to advise the customers about the new regulations etc. The older circuits are not mandatory but the new circuits will be.
Contradiction. What does 'required' and 'mandatory' mean if the Part L regs are not law. Sounds like they want to make it sound like law instead of specified as best practice.
Bit vague on heat loss at non extreme temperatures. OK, do a calc at -3°C but who has done heat losses at 5, 7, 10°C when heating is still required, without this how can you decide where to pinpoint the modulation range of the boiler? Just as the -5°C figure is only a tiny part of the heating season +13°C when heating is also required forms a small part of the total heating season. We've been covering this and showing how heat loss changes at different temperatures on our Heating Efficiency and Optimisation courses for a couple of years, also heat gains and ∆T across the boiler with the aid of ∆T pumps. Trainers are going to be busy
Wouldn't you just replace the normal conventional radiators with new low temperature flow designed radiators which are designed to be more efficient and so reduce the size of using a conventional radiator - granted the new low temperature radiators are more expensive.
Interesting video in the light of my home's history. I had a standard boiler fitted with a brand new central heating system when I moved into my 1901 terraced house. The installer calculated the system based on the house in 1989, so it had single glazing, no cavity wall insulation, and minimal loft insulation. Over the years the house has had all the above added, so like many older properties the calculations would now be different, with the possibility that the radiators are now back to the standards that are being proposed here Recently I've moved to a Baxi 800 (actually oversized) controlled by a Tado. I've noticed that I can already move to lower boiler temperatures myself most of the time. 55 degrees gives a drop to 34, but what's a degree really? I wonder if lots of older houses now fit into the new regs due to historical changes . The next plan will be a Baxi IFOS, which should force the boiler to lower temperatures in the blazing Lancashire sunshine (does Yorkshire need weather compensation, it always rains when I visit). It fascinates me to hear people in the media talking about the expense of heating. Before impending price increases my bills before the boiler change were lower than 13 years ago. Insulation and a Honeywell Sundial did all the heavy lifting there So, will the IFOS squeak another 10% saving on top of the 8% the Tado is giving?
Hi Phil. You make some very interesting points, I have never installed a Tado and to be honest I don’t know much about them. Maybe I could look into this for future videos. Thanks.
Yes it will. As you change the heat curve to suit you house. If it's a system boiler it will have an override PCB for the hot water so the boiler runs at max temp to heat cylinder then back to curve once cylinder is satisfied. We fit them all the time as they are only cheap for what you save.
@@DunkiSTI I have gone from system boiler to Combi. I've already gone to reducing the hot water to 56 degrees. As you say, the IFOS is very cheap. I know enough about how heating works to know how it will work, as I lurk looking at this stuff. On the other hand my 92 year old mother with dementia would be a different thing. She rang up today asking why her heating isn't on (it's 23 degrees outside). I suspect my over specced radiators will be a common thing.
Before they bring out new guidance they need to change the inspection and compensation scheme for new builds. Due to the rush to build new homes buildings are taking massive short cuts to avoid penalties. This includes missing insulation in new homes. Not enough inspectors and no legal protection for them or the house buyer allows builders to walk away from some shocking installations. In addition new homes need bigger room dimensions to allow the equipment to be fitted.
If you’re dropping flow temp to 55c, what’s the reason for continuing to use 20c diff as opposed to the 11c we were used to using? If you used 11c, you’re return is 44 and mean is 49.5. That means the rad size doesn’t need to be quite as big as you suggested. I thought that the initial reason for changing tac to use 20 diff was to bring return temps down below dew point yet maintain a higher flow temp because of typical existing rad sizes? Is there another reason for the 20c? Thank you.
Good video although i dont agree with the fact you can put 9kw through 22mm at DT5. This increases our velocity 1.36m/s when we should be designing at 0.9-1 and also our pressure loss is 944 pa/m when we ideally want no more than 300. That is also copper where plastic and mlcp will be even more restrictive especially with fittings. Heat pumps like flow and should always be designed and installed very carefully. 👍
Thanks for the comment. IMO 0.9 is perfect. I operate on the basis of 0.5 minimum and 1.5 maximum. Obviously the loss is relevant to the size of the index circuit. The chances of taking 9kw any real distance on an average house are minimal.
@@michaelhunt848 but we shouldn't be stretching our designs with heat pumps as you dont have the wiggle room like you do a gas boiler. For them to be working efficiently and to be achieving high COPs we should be sizing them properly or we will be seeing the SCOP of 2.5 like we are now which isn't good at all.
Really good video and thanks Allen and Mike for the info, my take for what its worth and I totally agree with Allen's summary at the end, I don't think customers in the whole will pay the extra ££, Boiler Hangers who don't watch this vid or any similar will have a field day(short term)and rake it in, at the expense of the conscientious installer. Easier said than done but educating the custards is key.
An issue I faced with my new build house boiler is that the boiler can only do one temp. I need put the flow temp above 60 in order to get the water in the tank hot enough to prevent legionella, so the return temp is likely higher than 55 and so there less chance of the boiler using the condensing efficiencies.
So im about to start a self build with UFH ground floor and radiators upstairs with a gas boiler. I can go bigger on the radiators and was going to change the UFH pipe centres from 200mm to 150mm. Will this be enough incase i swap to an ashp in the future or should they be 100mm centres which i wanted to avoid?
If you watch @Andrew Milward he can explain better. But at the worst all UFH should be designed with 150mm centres to achieve 90w psm ideally 100mm centres will be perfect 👍🏼.
Why avoid 100mm centres? Marginal extra cost, not more faff to install. Also, why do a gas boiler now? Your property would be perfect for an ASHP now, £5k grant is available, if you design right it’ll be cheaper to run than gas and you’ll have the option of not paying a gas standing charge every year saving more.
@@jassinghIG45 on a retrofit sure… starting from scratch is a different matter. They’ll be spending £1,000s on a gas boiler, pipe work, rads etc. with a £5k grant you’re basically a comparable cost with gas. Payback period would be short if they can get a high SCOP (which on this they should)
Manufacturers don’t need to advertise this to there installers. They need to advertise this to potential end users. So installers who size and quote jobs properly don’t get walked over by ones that throw in 24kw combis for every job. Also if a client has had a £800 designer rad fitted 2, 3 years ago and you say well we our going to have throw it on the scrap heap now, you won’t get the job for the boiler swap. It should be all new radiators fitted should be designed to run at a low flow temperature and new boilers where existing system design allows a 55 degree flow temperature. Also how do you heat a cylinder to 60, 65 degrees unless you use viesmann 4 pipe
@@edc1569 I am not sure they do. Low temperature means over condensing. For years in the commercial world we are told keep the back end temperature over 55 or it rots the boiler. Their are cast iron boilers still out their 30 years old. You will never get a modern boiler lasting that long. No one calculates how much Co2 could be saved if we make boilers that have a decent life cycle. The throw away world has taken over. I have still to be convinced that the country will have enough engineers to maintain complex electronic heat pumps. Lots of us oldies about to retire and 50% of kids at uni. Electric heating is going to take years. Houses will need to be modified. I am all for tech to save energy. But its really not a mystery. If you want to save energy turn it off. Insulation is a much better way.
Good video as alway Allen but how do we explain to a customer that only needs to replace boiler because it’s leaking or not financially not repairable we they have to have larger new radiators they won’t go for it
Controls have improved ,so is it time boiler manufacturers to up there game ? . Baxi are still manufacturing boilers with very poor modulation . . Why are they getting away with it . All boilers should also be able to be range rated .
The only point I would raise with talk of ultra low modulation is that in any system you can only get out what you put in. If you are modulated down to 4kw on a gas boiler then that's the maximum you've got to play with...before losses. With good insulation that can work well, but with the average badly insulated British house we are putting the cart before the horse here. We need to get the houses better insulated first. Everything will follow from that. The priorities are wrong......as usual.
Who is going to police the regulation changes? The installers that just do combi swaps will struggle or not bother at all trying to comply with the new regs. As for heat loss calcs- probably stick a finger in the air and guess!! if no one polices it no few will comply as you say. The good installers that go by the book will lose out to the fit it and F off boys. Also, oil boilers generally don't modulate and have a flow temp of 65 degrees minimum. Interesting times ahead.
Well the maths is wrong. 1. how can 1.3 *1 =1 in the boiler at 80 degree calculation? So the radiator in the calculation is too small! 2. All things being equal for a fair comparison, the return Delta temperature of two low temperature heating systems will be the same as the energy coming out into the house is the same. The heat pump can’t magically increase the return temperature when no extra energy is being put in! The flow rate should be the same for a fair comparison. It’s also worth mentioning that with a smaller temperature difference that the heat exchanger in the heat pump would also have to huge in these calculations!
Hi Dominic, Thanks for your reply. Its not times 1.3. Its to the power of 1.3. The radiator calculation is fine. With the greatest respect, your further comments are incorrect. The return temperature of a heat source with a narrower DT will be higher than that with a wider DT if they both have the same flow temperature. Also the one with the narrower DT will have a higher mean water temperature and as such will give out the same heat with a smaller emitter. Its just physics. Have a great day.
The engineers that try do the best job won’t struggle for work because the crap engineers will be creating work for us we will be busy putting the work they have done which doesn’t work right and will cost the customer more in the long run
Who will police this no one so nothing will change Same with This boiler plus Iv been to loads of jobs where they Havant complied your sounding like a sales person trying to get the customer to change the rads on a combi swap it’s not going to happen with the huge price increase on a job
It all depends on the customer? I installed LED lighting in my house many years back when people said they were dim or bizarrely came on slowly. It should be a matter of managing customer expectations. Tell them that it saves them money, and how. As I said earlier, many houses may now have oversized radiators as calculations were made on under insulated house
@@philtaylor194 totally agree ,but theres a hige diffrent in bulbs and explaining why they cant have a 40kw boiler . I agree with the principles but when u battle with customers who cant grasp with with a simple room stat, theres no hope
@@accesszero4803 Indeed. I am seen by colleagues as the go to for energy advice. However, getting across that a TRV is not an accelerator is a big enough hill to climb
Designer rads have an energy output spec like standard rads so the calcs can still be done and a designer rad of the correct size spec'd for that room.
www.gov.uk/government/publications/conservation-of-fuel-and-power-approved-document-l
Great video Allan
You try telling a customer they need a new boiler and all the rads replacing as there too small and the temperature will be set to a max of 55 degrees most jobs will jump £1250 - £2000 extra for rads and I bet the price for the big rads with go through the roof.
But will they? What if calculations were made on a typical install from scratch calculated 30 years ago. No cavity wall insulation, single glazing, no draught proofing and minimal loft insulation. I know my energy bills now are lower than they were 15 years ago despite inflation.
With bigger radiators, there is a higher volume of water for the boiler to heat (although at a lower temperature). So is more gas being burnt, or effectively the same amount? Where is the savings?
Great video as always. But with system or heat only systems with unvented hot water cylinders with legionellia requiring storage at 60 Degrees. Only boilers capable of firing at two different outputs with DHW priority, weather comp will give the best efficiency... Intergas exclusive and the other one aswell as viesmen can fire on full output to recharge the Hot water cylinder on DHW priority then modulate right down to the heating systems heatloss... But as you say everything starts with a accurate heat loss calculations!
Just fitted new boiler in my house , flow temp set at 55 , spent time insulating and draught proofing . Boiler still offers quick heat up time as I’m not home much .
Hi Batman. What boiler have you installed? Thanks.
Couldnt agree more with what you said about manufactures needing to drop down their minimum modulation, its not like they didnt know in advance, and yet their minimum in some cases is way above your requirements even on their smallest boilers, Baxis I looked at were way above what I needed.
I have already been doing this on an ad hoc basis in my own old house for some years . Installing the Weather Compensation kit on my heat only boiler reduced the flow temperature, and modulates it. I changed my existing single row emitters to double or even triple row so they run cooler but give out the same heat. The only thing that keeps the high flow temp is the hot water cylinder circuit..because it has to. The weather comp electrical circuit allows that. I fitted a Magnaclean about a decade ago. The system works OK, but it does take some getting used to cooler radiators. I also enabled the optimisation feature on my budget Center Brand programmable room stat ( it's a Honeywell underneath). I don't think that with the heat loss profile of my 1885 solid stone house I could get a heat pump to work well without major works to improve the insulation. We are thinking about how to improve insulation affordably over and above what we have managed up to now. My budget is not endless now I'm retired ( from heating). I wonder how my old Mears heat loss calculator would stand up these days😉
You better tell all the new build sites in england as all they put in is 10mm plastic and its not good enough for heat calculations
I have a 1930s solid wall (no cavity) home, mostly installed with insulated plasterboard, loft insulation, old double glazing, suspended floors with no insulation. Approx 2000 sqft, 16 rads (new, convector type). I oversized the rads by assuming in the calcs the walls were still solid brick with no insulation. The boiler is an Ideal Logic 30+ combi (zoned off for an unvented cylinder). The Drayton Wiser controls are set to Opentherm modulation. During colder months the heating is set to 19.5c from 6.30am to 10.30pm. Over night it's set to approx 17c.
I find that first thing in the morning (when the house is coldest) the boiler fires at 65c to 70c, given demand is highest. Once 19.5c set temp is reached the boiler modulates down to 40c to 50c (or lower, if not to cold outside, I've seen as low as 35c). At flow 50c return temp is about 35c. At flow 35c return is about 30c. (I've never been able to reach delta T of 20; is it normal that the lower the flow temperature the smaller delta T gets?).
The house stays toasty and warm, the boiler super efficency shows as 72% (which I believe means it's in maximum efficiency / condensing mode 72% of the time).
The boiler rarely fires over night, I figure this is because all of the internal walls are solid brick and act like very large, low temp, storage heaters - releasing heat over night. I'm guessing new regs don't take this into account (given new builds are mostly stud wall etc).
Really enjoy your videos, very informative!
Cracking video 👍👍👍
Definitely boilers should be sized and range rated to the property.
Yes I agree
Great educational videos. Can you do one on pipe sizing?
Yes I can
Thanks for this video Allen, can you acually make boiler range rating comparasion video? That could help others choosing best option.
That sounds like a really good idea. I will see what I can do. Thanks.
Good Video Allen. Can you do a small list of combi boilers that can be range rated lower in the settings. I've installed a few Baxi 800's and they have no way of adjusting them in the settings menu. 👍🏾
Very helpful vid mate. Can you also do one on part J ? Thanks
Great video! Good to have the actual maths explained. What about an in-depth video on heat loss calculations?
Very clear instructions.Thanks
Good ,informative video ,thanks for your hard work over last few years. Review and more detailed comparison of low modulating boilers and open term controls , which are on the market, will be helpful (as long as not sponsored by the manufactures). .Heard lot of good about Intergas (and lot of bad so we had never installed them..)
Rule of thumb double the rad size in terms of output from the makers tables.
Your summing up pretty much mirrors my thoughts.
Question for you: For me as someone who works on ALL fuel types, do these regs apply to oil and S/fuel boilers also? As neither of these are modulating.........
Just gas i believe but not sure.
Thank you Sir. Excellent as always.
I'm looking to install a new combi boiler. We have 10 rads and one shower fed off the boiler. Semi detached 4 bed house originally 3 (had a room made in the loft).
Current boiler is 28kw and has lasted us for over 10 years with no problems.
Was looking at a Main eco 30 or a Baxi 636, any other recommendations?
Viessmann 100. You can range rate it down to suit your load. Thanks.
Great Video Allen, thanks
Thanks.
Thanks, another really informative video. I still find modulation confusing, surely when the water gets up to temp the flame then turns off but the pump keep running, or does the flame stay on but just down to that lower kw? I have a 40kw Baxi combi which for most of the winter I've managed to run at 55c flow already, just about got away with it but heat up from cold probably too slow for most people. Thanks
Radfoo good morning, you will probably find later in the eves that your boiler would stop start a lot (it is called cycling) as it is not capable to modulate as low, if it makes sense. I have a 33kw one, and later on in the eve is on off like a yoyo 🙄
Dont be confused with water temperature as modulation even though its part of it, You can turn any boiler stat down so that the system water isnt heated too high and that doesnt make your boiler efficient, the modulation part on *modulating boilers* is actually dependent on the temperature across the flow/return when the boiler gets close to its target stat temp the fan speed that sucks the air and gas into the burner will slow down and suck less air gas in, pretty sure i have seen modulation as low as 1:8 so 8 times lower than the maximum heat input for example a 30kw would go as low a 3.75 kw
Been a while since i refreshed my knowledge on this stuff so apologies if some of that isnt quite exact..
@@cvplumbersandheating I also have the Baxi 830 and found that setting the boiler temp to 55 degrees, it cycles much less. Hmm. I have 10mm microbore and 9 rads. I use a Danfoss thermostat with the modulation setting optimum for a condensing boiler.
hi Allan,Great videos.Just wanted to ask, with the implementation of these regs and there is non compliance when installing new systems ,Will it affect the ability to sell that house and how will it affect landlords? if it all. Thanks
In the video (on the chart) what does the 1.3 multiplication factor represent?
I was wondering that too. So I found this out: "When you reduce the mean water temperature of a radiator its heat output *does not reduce linearly."*
eg reduce mean water temperature by half, results in *less than half* of the heat output.
As there is a non linear reduction a 'correction' factor needs to be applied from a table:
Delta_TCorrection:
DeltaT. Correction Factor
20 0.3
25. 0.41
30. 0.52
35. 0.63
40. 0.75
45 0.87
50. 1
These corrections are from
20/50 ^ 1.3
25/50 ^ 1.3
etc, rounded up to two decimal places.
You'll see the 0.41 (0.406 used in chart in the video)
For the heat pump 32.5/50 ^1.3 = 0.57 (which isn't in the chart above, but it shows how such a chart is calculated)
HTH
@@vidleon thanks for that. Just not explained on the video. 👍🏻
It relates to the types of heat emitters we use- there is some variance for other types of emitters
unefficient S plan systems must be replaced with DHW priority. As having one flow temp of 65 Degrees to heat up the stored water is a waste of energy when most properties heat loss is 7 to 9 KWH and would run much more efficient at a lower flow temperature. I suppose mixed and blended curcuits would be one way of doing it as well as priority DHW and a boiler that can fire on two heat outputs :-)
Hot water priority doesn’t always suit everyone. It can be a real pain if you have a large hot water demand. Thanks.
Morning Alan. I may have misunderstood the new regulations but I can’t see how an existing system designed for the higher flow temperature can have additional radiators added that work at the lower temperature. Also, are towel rads going to become obsolete?
You make some good points. we will see how it all pans out.
Hello David..
Good point, possible solutions could be :-
Trv on the new radiators that will be too large for a 70 degree flow temperature will heat the room quickly and switch off earlier than te others ?
Adjust the balancing of the radiator. Slow the flow excessively to reduce the average temperature flow /return - may deal with it. Good luck finding a lockshield valve that will reduce enough and reliably !
I'd be interested in your thoughts ?
I called my local building control about the new part L regs.
I was told that they need full designs and heat loss calcs for all new builds, this need to be backed up by photographic evidence that the work has been carried out as per the design. For extensions they will also require Heat loss calculations but photographs are not required. For upgrade work we are required to change radiators so that they will work at the 55c design temp. If the older parts of the house do not conform to part L, we are to advise the customers about the new regulations etc. The older circuits are not mandatory but the new circuits will be.
Contradiction. What does 'required' and 'mandatory' mean if the Part L regs are not law. Sounds like they want to make it sound like law instead of specified as best practice.
Bit vague on heat loss at non extreme temperatures. OK, do a calc at -3°C but who has done heat losses at 5, 7, 10°C when heating is still required, without this how can you decide where to pinpoint the modulation range of the boiler?
Just as the -5°C figure is only a tiny part of the heating season +13°C when heating is also required forms a small part of the total heating season.
We've been covering this and showing how heat loss changes at different temperatures on our Heating Efficiency and Optimisation courses for a couple of years, also heat gains and ∆T across the boiler with the aid of ∆T pumps.
Trainers are going to be busy
Looks like a massive increase in lost wall space to radiators.
Hi John. You could also use underfloor heating. Thanks.
Hello Allen, what is the new radiator sizes for rooms and living rooms?
Heatloss loss Calculation and Head loss calculations also pipe sizing calculations PLEASE!
I will try and do more of these at Viva Training. Thanks.
Wouldn't you just replace the normal conventional radiators with new low temperature flow designed radiators which are designed to be more efficient and so reduce the size of using a conventional radiator - granted the new low temperature radiators are more expensive.
Thanks Allen top video
Thank You
Thank you so much for this experience
Interesting video in the light of my home's history. I had a standard boiler fitted with a brand new central heating system when I moved into my 1901 terraced house. The installer calculated the system based on the house in 1989, so it had single glazing, no cavity wall insulation, and minimal loft insulation.
Over the years the house has had all the above added, so like many older properties the calculations would now be different, with the possibility that the radiators are now back to the standards that are being proposed here
Recently I've moved to a Baxi 800 (actually oversized) controlled by a Tado. I've noticed that I can already move to lower boiler temperatures myself most of the time. 55 degrees gives a drop to 34, but what's a degree really? I wonder if lots of older houses now fit into the new regs due to historical changes .
The next plan will be a Baxi IFOS, which should force the boiler to lower temperatures in the blazing Lancashire sunshine (does Yorkshire need weather compensation, it always rains when I visit).
It fascinates me to hear people in the media talking about the expense of heating. Before impending price increases my bills before the boiler change were lower than 13 years ago. Insulation and a Honeywell Sundial did all the heavy lifting there
So, will the IFOS squeak another 10% saving on top of the 8% the Tado is giving?
Hi Phil. You make some very interesting points, I have never installed a Tado and to be honest I don’t know much about them. Maybe I could look into this for future videos. Thanks.
Yes it will. As you change the heat curve to suit you house. If it's a system boiler it will have an override PCB for the hot water so the boiler runs at max temp to heat cylinder then back to curve once cylinder is satisfied. We fit them all the time as they are only cheap for what you save.
@@DunkiSTI I have gone from system boiler to Combi. I've already gone to reducing the hot water to 56 degrees.
As you say, the IFOS is very cheap. I know enough about how heating works to know how it will work, as I lurk looking at this stuff.
On the other hand my 92 year old mother with dementia would be a different thing. She rang up today asking why her heating isn't on (it's 23 degrees outside).
I suspect my over specced radiators will be a common thing.
Before they bring out new guidance they need to change the inspection and compensation scheme for new builds. Due to the rush to build new homes buildings are taking massive short cuts to avoid penalties. This includes missing insulation in new homes. Not enough inspectors and no legal protection for them or the house buyer allows builders to walk away from some shocking installations. In addition new homes need bigger room dimensions to allow the equipment to be fitted.
If you’re dropping flow temp to 55c, what’s the reason for continuing to use 20c diff as opposed to the 11c we were used to using?
If you used 11c, you’re return is 44 and mean is 49.5. That means the rad size doesn’t need to be quite as big as you suggested.
I thought that the initial reason for changing tac to use 20 diff was to bring return temps down below dew point yet maintain a higher flow temp because of typical existing rad sizes?
Is there another reason for the 20c?
Thank you.
Good video although i dont agree with the fact you can put 9kw through 22mm at DT5. This increases our velocity 1.36m/s when we should be designing at 0.9-1 and also our pressure loss is 944 pa/m when we ideally want no more than 300. That is also copper where plastic and mlcp will be even more restrictive especially with fittings. Heat pumps like flow and should always be designed and installed very carefully. 👍
Thanks for the comment. IMO 0.9 is perfect. I operate on the basis of 0.5 minimum and 1.5 maximum. Obviously the loss is relevant to the size of the index circuit. The chances of taking 9kw any real distance on an average house are minimal.
@@michaelhunt848 but we shouldn't be stretching our designs with heat pumps as you dont have the wiggle room like you do a gas boiler. For them to be working efficiently and to be achieving high COPs we should be sizing them properly or we will be seeing the SCOP of 2.5 like we are now which isn't good at all.
Totally agree mate.
I guess the goal here is to button up the house, before selecting medium temp rads.
Really good video and thanks Allen and Mike for the info, my take for what its worth and I totally agree with Allen's summary at the end, I don't think customers in the whole will pay the extra ££, Boiler Hangers who don't watch this vid or any similar will have a field day(short term)and rake it in, at the expense of the conscientious installer.
Easier said than done but educating the custards is key.
An issue I faced with my new build house boiler is that the boiler can only do one temp. I need put the flow temp above 60 in order to get the water in the tank hot enough to prevent legionella, so the return temp is likely higher than 55 and so there less chance of the boiler using the condensing efficiencies.
Hi Dino. you could address that by having a different setup, depending on the boiler.
So im about to start a self build with UFH ground floor and radiators upstairs with a gas boiler. I can go bigger on the radiators and was going to change the UFH pipe centres from 200mm to 150mm.
Will this be enough incase i swap to an ashp in the future or should they be 100mm centres which i wanted to avoid?
If you watch @Andrew Milward he can explain better. But at the worst all UFH should be designed with 150mm centres to achieve 90w psm ideally 100mm centres will be perfect 👍🏼.
Why avoid 100mm centres? Marginal extra cost, not more faff to install.
Also, why do a gas boiler now? Your property would be perfect for an ASHP now, £5k grant is available, if you design right it’ll be cheaper to run than gas and you’ll have the option of not paying a gas standing charge every year saving more.
@@kieranmccreedy271 still a massive cost to fork out initially and the tech is not all there for low flow temps.
@@jassinghIG45 on a retrofit sure… starting from scratch is a different matter.
They’ll be spending £1,000s on a gas boiler, pipe work, rads etc. with a £5k grant you’re basically a comparable cost with gas. Payback period would be short if they can get a high SCOP (which on this they should)
Manufacturers don’t need to advertise this to there installers. They need to advertise this to potential end users. So installers who size and quote jobs properly don’t get walked over by ones that throw in 24kw combis for every job. Also if a client has had a £800 designer rad fitted 2, 3 years ago and you say well we our going to have throw it on the scrap heap now, you won’t get the job for the boiler swap. It should be all new radiators fitted should be designed to run at a low flow temperature and new boilers where existing system design allows a 55 degree flow temperature. Also how do you heat a cylinder to 60, 65 degrees unless you use viesmann 4 pipe
Some manufacturers are going to struggle as they don’t modulate down enough as well. Thanks.
Ive always wondered how do you heat a tank to 60 for legionella when the ch is lwer than that?
@@handle1196 I believe some boilers allow for a separate boiler call for hot water tanks, allowing a higher temp to be set.
Use EPH controls on an opentherm boiler to get dual temp
@@handle1196 hot water priority, intergas W plan.
Whilst gas is 0.07p a kwh and leccy 0.28p a kwh i don't see customers buying in
why wouldn't customers want their gas boilers to run more efficiently?
@@edc1569 I am not sure they do. Low temperature means over condensing. For years in the commercial world we are told keep the back end temperature over 55 or it rots the boiler. Their are cast iron boilers still out their 30 years old. You will never get a modern boiler lasting that long. No one calculates how much Co2 could be saved if we make boilers that have a decent life cycle. The throw away world has taken over. I have still to be convinced that the country will have enough engineers to maintain complex electronic heat pumps. Lots of us oldies about to retire and 50% of kids at uni. Electric heating is going to take years. Houses will need to be modified. I am all for tech to save energy. But its really not a mystery. If you want to save energy turn it off. Insulation is a much better way.
Good video as alway Allen but how do we explain to a customer that only needs to replace boiler because it’s leaking or not financially not repairable we they have to have larger new radiators they won’t go for it
You will still be able to replace the boiler.
Controls have improved ,so is it time boiler manufacturers to up there game ? .
Baxi are still manufacturing boilers with very poor modulation . .
Why are they getting away with it .
All boilers should also be able to be range rated .
The only point I would raise with talk of ultra low modulation is that in any system you can only get out what you put in. If you are modulated down to 4kw on a gas boiler then that's the maximum you've got to play with...before losses. With good insulation that can work well, but with the average badly insulated British house we are putting the cart before the horse here. We need to get the houses better insulated first. Everything will follow from that. The priorities are wrong......as usual.
I don't follow, if you've got 6:1 modulation and 4kw is minimum then you've got up to 24kw to play with - that's the point.
I do think that customers will not always want larger sized radiators throughout and so this will define the work carried out.
It’s very unlikely customers will want to spend more money than they need too lol .
Who is going to police the regulation changes? The installers that just do combi swaps will struggle or not bother at all trying to comply with the new regs. As for heat loss calcs- probably stick a finger in the air and guess!! if no one polices it no few will comply as you say. The good installers that go by the book will lose out to the fit it and F off boys.
Also, oil boilers generally don't modulate and have a flow temp of 65 degrees minimum. Interesting times ahead.
Well the maths is wrong. 1. how can 1.3 *1 =1 in the boiler at 80 degree calculation? So the radiator in the calculation is too small! 2. All things being equal for a fair comparison, the return Delta temperature of two low temperature heating systems will be the same as the energy coming out into the house is the same. The heat pump can’t magically increase the return temperature when no extra energy is being put in! The flow rate should be the same for a fair comparison. It’s also worth mentioning that with a smaller temperature difference that the heat exchanger in the heat pump would also have to huge in these calculations!
We have a full detailed video coming soon, This is a full house with a heat pump going in. Thanks.
Hi Dominic,
Thanks for your reply. Its not times 1.3. Its to the power of 1.3. The radiator calculation is fine.
With the greatest respect, your further comments are incorrect. The return temperature of a heat source with a narrower DT will be higher than that with a wider DT if they both have the same flow temperature. Also the one with the narrower DT will have a higher mean water temperature and as such will give out the same heat with a smaller emitter. Its just physics.
Have a great day.
Time to retire, few will want to replace all rads
so many regs to follow now. plumbers need to earn good money otherwise its hardly worth it.
Leave it to the heating engineers?
@@edc1569 "Engineers"???
The engineers that try do the best job won’t struggle for work because the crap engineers will be creating work for us we will be busy putting the work they have done which doesn’t work right and will cost the customer more in the long run
Fingers crossed that means all the Baxi and Ideal boiler range will be banned!
Ideal vogue was better than the Viessmann 100 upto this year lol.
Who will police this no one so nothing will change Same with This boiler plus Iv been to loads of jobs where they Havant complied your sounding like a sales person trying to get the customer to change the rads on a combi swap it’s not going to happen with the huge price increase on a job
Building Control, certification required when selling up etc, Completion Certificates for refurbs.
What a load of rubbish, its impossible to explain/make customers understand this.the industry wont change and customers wont have huge daft radiators
It all depends on the customer? I installed LED lighting in my house many years back when people said they were dim or bizarrely came on slowly.
It should be a matter of managing customer expectations. Tell them that it saves them money, and how. As I said earlier, many houses may now have oversized radiators as calculations were made on under insulated house
@@philtaylor194 totally agree ,but theres a hige diffrent in bulbs and explaining why they cant have a 40kw boiler . I agree with the principles but when u battle with customers who cant grasp with with a simple room stat, theres no hope
@@accesszero4803 Indeed. I am seen by colleagues as the go to for energy advice. However, getting across that a TRV is not an accelerator is a big enough hill to climb
People want designer radiators not big ugly ones big radiators will look stupid in rooms
Lower flow temps can still be achieved with designer rads, just means installers will have to use their brain and design the system better.
There needs to be a education campaign towards the end user (customer) otherwise cowboys prosper!
Since when is a standard type22 rad ugly?
Designer rads have an energy output spec like standard rads so the calcs can still be done and a designer rad of the correct size spec'd for that room.