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

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deema

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I’ve been researching like many others efficient ways of reducing heating costs. Now, I might be wrong, but I stumbled across Part L of the Building Regs updated 15 June 2022. Building regs used to just be involved with new installation, but now they also appear to be mandatory for replacement boilers.

The updated regs specify that all replacement boilers MUST have a maximum water temperature for heating of 55C!! An assessment of the radiators, pipes etc as well as installing a weekly cycle heater of the hot water tank (if there is one) to kill legionella.

All traditional boiler heating systems run at say 80C which means that radiators will be significantly derated in their BTU when run on a cooler water temperature. Now if my maths are correct, a radiator running at say 50C above room temp with a 1000W output (3400BTU) has when running at only a 30C difference only an output of 510W or 1700BTU a reduction of 50% meaning you need a radiator with twice the output…..or simply put new radiators! (You might be lucky and the installer over sized the existing rads)

With reduced temperatures microbore which is very common to have been installed as it’s cheap (8 or 10mm pipes) may not be able to deliver sufficient water to supply the necessary BTU for the rads to dissipate in order to heat the room. That means the pipes might need replacing to increase the bore to say 15mm. (225% more water volume than a 10mm pipe)

So why the change, (my theory) well the maximum water temperature that’s been set is…….the working temperature for heat pumps (air or ground source). So basically it’s getting every house ready for heat pump heating…….the UK does not have sufficient generating capacity for all houses to use heat pumps!

So, if your thinking of getting your boiler changed, and the installer is doing the work according to the reg, you could well be in for a very nasty and very expensive shock. Now that’s a sneaky implementation of legislation that nobody seems to have picked up / shouted about. A lot of people just won’t be able to afford to have all the upgrades necessary.
 
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Panic ye not, Deema....that's not what the regs say
 

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Deema, The regs. (section 5.10) actually seems refers to the replacement of the complete system and not just the boiler and therefore they are trying to make the owner go down the low Temp route.
 
How long will it take for these to filter through the design, manufacturing and sales path.... ?
 
It’s the interpretation of 5:10 that I dont think is clear. For instance, if you take the whole paragraph which says whole system, if you leave a say 10mm length of the old pipe would this mean you don’t need to comply? Chatting with a building inspector he suggested it applied to just a boiler change.
 
It’s the interpretation of 5:10 that I dont think is clear. For instance, if you take the whole paragraph which says whole system, if you leave a say 10mm length of the old pipe would this mean you don’t need to comply? Chatting with a building inspector he suggested it applied to just a boiler change.
I would suggest that that particular building inspector is in need of a bit of re-training.
 
With reduced temperatures microbore which is very common to have been installed as it’s cheap (8 or 10mm pipes) may not be able to deliver sufficient water to supply the necessary BTU for the rads to dissipate in order to heat the room. That means the pipes might need replacing to increase the bore to say 15mm. (225% more water volume than a 10mm pipe)
There has been a change in flow and return temperatures since the introduction of condensing boilers which need a lower return temperature of around 50°C in order to actually condense. This caused issues because unless you replace the radiators with larger ones then you had to reduce the flow temperature to get the lower return temperature but then less heat from the radiators. As for microbore this is just another cost saving for the builders because it can be slung in with little skill compared to fitting 15mm that requires a pipe bender and fittings.
 
There has been a change in flow and return temperatures since the introduction of condensing boilers which need a lower return temperature of around 50°C in order to actually condense. This caused issues because unless you replace the radiators with larger ones then you had to reduce the flow temperature to get the lower return temperature but then less heat from the radiators. As for microbore this is just another cost saving for the builders because it can be slung in with little skill compared to fitting 15mm that requires a pipe bender and fittings.
Ref Microbore pipework, its often said that it was used as a low cost option however whilst this may have been true for some installations, a real benefit of Microbore is that it lends itself to be buried in walls, and with a smaller surface area its heat loss into its surroundings is considerably less. We have an 8mm system and whilst I wouldnt choose it it does work just fine.
Steve.
 
I think that burying pipes in walls if they outside walls is a really bad idea. They wont be insulated so basically you are heating up the wall with a lot of heat leaking to the outside And not where you want it. The larger the diameter of the pipe the smaller the ratio of volume to circumference which what you want to reduce heat loss. Ie for a given length of pipe and given volume of water flowing through it, the 15mm pipe will lose less heat than a 8 or 10mm pipe.
 
I thought one of the earlier ideas for microbore was to enable different zones in a house, supplied via a manifold with timer controlled valves. That woudl allow things like warming the bedrooms/bathroom and living room at times to suit. I guess we now have the option of individually controlled radiator valves - at a price - but microbore+manifold struck me as a good idea.

On the boiler/return temperature discussion, yes a condensing boiler needs a lower return temperature for maximum efficiency, and that would suggest lower set temperature and bigger radiators might be needed, but I wonder if just starting the heating a bit earlier would do the same thing. If a house has resonable insulation the system doen't have to work very hard to maintain steady state except in rare (in UK) very cold or windy weather. There must be a cost and CO2 trade off between best boiler efficiency and running it for a bit longer each day (assuming you don't rush out and replace all the radiators). Wonder how to work it out ... too many variables I think.

Summer 2021 we relpaced our 35 year old oil boiler with a new 'blueflame' one - cost to go ashp and all the insulation we would need was prohibitive - and I reckon we saved over 200l of oil last winter. It was mild though, so need a year or few to really know. Won't pay for itself, except that the old one was about to die anyway so it would have to be done one day.
 
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 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 moved last May and our new (to us) house runs on oil. I've experimented with various timing scenarios to heat it and have come to a similar conclusion as you: it's best to simply set the temperature and just leave it running all the time. We run a slight set back at night. A few caveats though: we have hydronic under floor heating, a thermal store and thermostats in each room. It's actually quite nice having a warm house throughout and hot water whenever you want it. One downside is that I haven't found a way to stop the boiler from short cycling - there doesn't seem to be a facility in its control system.

It's hard to know if we are actually saving money using the central heating in this way as we don't have long term history data using any other method. It's a bit of a shock when I have to refill the oil tank but that's mainly because it's a big bill in one go as opposed to a monthly direct debit to a gas or electric company.

LPG, from what people tell me, is a pretty expensive form of heating and, often, you are tied to a particular supplier.

Heat pumps? I've researched this to death and, for our old house, even with under floor heating, I'm not convinced that it's a cheaper option. My green aspirations do not exceed the worry of emptying my wallet, sorry to the green lobby, in advance!
 
We moved last May and our new (to us) house runs on oil. I've experimented with various timing scenarios to heat it and have come to a similar conclusion as you: it's best to simply set the temperature and just leave it running all the time. We run a slight set back at night. A few caveats though: we have hydronic under floor heating, a thermal store and thermostats in each room. It's actually quite nice having a warm house throughout and hot water whenever you want it. One downside is that I haven't found a way to stop the boiler from short cycling - there doesn't seem to be a facility in its control system.

It's hard to know if we are actually saving money using the central heating in this way as we don't have long term history data using any other method. It's a bit of a shock when I have to refill the oil tank but that's mainly because it's a big bill in one go as opposed to a monthly direct debit to a gas or electric company.

LPG, from what people tell me, is a pretty expensive form of heating and, often, you are tied to a particular supplier.

Heat pumps? I've researched this to death and, for our old house, even with under floor heating, I'm not convinced that it's a cheaper option. My green aspirations do not exceed the worry of emptying my wallet, sorry to the green lobby, in advance!
I have been pondering on permanently on heating, but we are so tight on money I only turn it on for an hour if the indoor temperature feels particularly chilly (that's usually in the low 15s or under) then I set the temperature to the balmy 16.5C.

I do have the water on constantly right now, there is a well insulated cylinder and I got fed up with my wife saying the bath water is cold because the heating has been on (I'm going to change from 'Y' to 'S' system in the summer).
I've looked around but there don't seem to be any equivalent to electricity smart meters, I want one that will count the hours the boiler is firing, not just turned to "on", and constantly chart this so I can properly see the best return on oil used with various timing scenarios. It's simple enough and I could easily make one - except I have an outside boiler so unless I drill holes and have wires everywhere I will need bluetooth or wifi and a program or app for a phone or computer. A nice use for the raspberry computer my son gave me a few years ago if my depleting mental agility will cope.
 
I have been pondering on permanently on heating, but we are so tight on money I only turn it on for an hour if the indoor temperature feels particularly chilly (that's usually in the low 15s or under) then I set the temperature to the balmy 16.5C.

I do have the water on constantly right now, there is a well insulated cylinder and I got fed up with my wife saying the bath water is cold because the heating has been on (I'm going to change from 'Y' to 'S' system in the summer).
I've looked around but there don't seem to be any equivalent to electricity smart meters, I want one that will count the hours the boiler is firing, not just turned to "on", and constantly chart this so I can properly see the best return on oil used with various timing scenarios. It's simple enough and I could easily make one - except I have an outside boiler so unless I drill holes and have wires everywhere I will need bluetooth or wifi and a program or app for a phone or computer. A nice use for the raspberry computer my son gave me a few years ago if my depleting mental agility will cope.
We have a Tado system with thermostats on all the radiators in the house (except the bathroom towel rails). It works very well for us including turning off when we leave the house and on again as we are returning. It also detects open windows or doors and stops heating the room. Being able to switch the spare rooms off individually is very useful. When the kids come home it’s just a case of resuming the schedule on their room.
You can get quite a bit of information on what the system is doing including how much gas, in our case, you are using.
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I think that burying pipes in walls if they outside walls is a really bad idea. They wont be insulated so basically you are heating up the wall with a lot of heat leaking to the outside And not where you want it. The larger the diameter of the pipe the smaller the ratio of volume to circumference which what you want to reduce heat loss. Ie for a given length of pipe and given volume of water flowing through it, the 15mm pipe will lose less heat than a 8 or 10mm pipe.
Indeed its not a good idea and I wouldnt do it myself, but if your installing a drop pipe system it was a neater option, I will happily accept what your saying about the heat loss as Im easily baffled by science, but it does seem counter intuitive, ie larger radiating surface giving off less heat!
Steve.
 
Having been replacing the small bore pipework with 15mm as I replace radiators and rework rooms is that it is so evident that the biggest advantage of these small bore pipes is installation cost. If you compare running a pair of 15mm pipes down to a radiator and then making the job neat to using small bore the time difference is hours. The small bore was just run down the blockwork and then along the bottom edge to the radiator, clipped to the blockwork. Then the plasterboard was slapped over the top using dot and dab, no skill required on the part of the guy fitting the pipes.
 
I thought one of the earlier ideas for microbore was to enable different zones in a house, supplied via a manifold with timer controlled valves. That woudl allow things like warming the bedrooms/bathroom and living room at times to suit. I guess we now have the option of individually controlled radiator valves - at a price - but microbore+manifold struck me as a good idea.

On the boiler/return temperature discussion, yes a condensing boiler needs a lower return temperature for maximum efficiency, and that would suggest lower set temperature and bigger radiators might be needed, but I wonder if just starting the heating a bit earlier would do the same thing. If a house has resonable insulation the system doen't have to work very hard to maintain steady state except in rare (in UK) very cold or windy weather. There must be a cost and CO2 trade off between best boiler efficiency and running it for a bit longer each day (assuming you don't rush out and replace all the radiators). Wonder how to work it out ... too many variables I think.

Summer 2021 we relpaced our 35 year old oil boiler with a new 'blueflame' one - cost to go ashp and all the insulation we would need was prohibitive - and I reckon we saved over 200l of oil last winter. It was mild though, so need a year or few to really know. Won't pay for itself, except that the old one was about to die anyway so it would have to be done one day.
Microbore runs off a manifold system, a bit like modern plastic underfloor systems but ours doesnt have any fancy controls.
Im no expert but did read a report by a bunch of experts who basically said that many Condensing boilers hardly ever got into condensing mode because they had been wrongly sized, its apparently a particular problem with Combi boilers because there is a tendency to go for the larger Btu model to give better domestic HW supply. It sounded convincing enough.
As to running the heating permanently, we all know that this was once considered the way to go but of late your Martin Lewises and the like have poo pooed the idea,,I wonder if they've got it wrong, or that with some informed people well insulating their homes to a high degree of efficiency, it now becomes the better option?
 
@davethebb Thanks for the links, I’ve never heard of this technology and will certainly be giving it a good cost of looking at.

The tank I will have is 2500ltr and from a bit of research it appears that I have to sign up to a provider for a minimum of 2 years! The price of LPG / litre ys the same roughly as oil, but about half the calorific value!! If I can ensure the condensing boiler is condensing I will gain around 20 to 25% efficiency gain over my very old but highly reliable oil burning boiler I have now.
 

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