ASHP install questions

NedS

https://forums.moneysavingexpert.com/discussion/comment/81900316#Comment_81900316

Absolutely agree @Alnat1, this is just absolute nonsense that you may read in the heat pump hating Telegraph, or similar.

I have a 17th century stone cottage, not exactly the definition of well insulated, and I'm delighted with my heat pump which now costs around half the cost to heat compared to a gas or oil boiler.

Anyone is welcome to come visit my property, see for themselves and have a chat with me about the reality of living with a heat pump. I hold regular sessions on Visit a Heat Pump website.

akwexavante

I love my ASHP too, even more so after beefing up my insulation. I would highly recommend anybody to consider having one especially in a new modern home, older homes i would suggest they have a close look at how well it's insulated.

When i moved into my 1930's home in 2021 i discovered that the previous owner was spending £1900 to £2202 a year on propane. Mum and two daughters. Two bed roomed end terrace.

I'm now over paying at £54 a month, £648yr. So OK i do have Solar as well thinking about it, so if i remove used solar and exported solar i would be paying £77 a month or £927 a year. I'm all electric.

If you look at my other posts you'll find i have a multifuel stove too, but it has only been used 7 times between Oct 25 and end Feb 26. Xmas eve, Xmas day, Boxing Day, NY eve, NY Day and twice in Jan when i had a power cut.

tfhnota

I don't think I could ever fall in love with a heating system but that is probably just me…

matelodave

https://forums.moneysavingexpert.com/discussion/comment/81904348#Comment_81904348

It can give some of us endless fun - there's something really satisfying about tweaking to try and cheive perfection 🤣

michaels

I think the reason that insulation is more important with a heat pump is the relationship between flow temperature and COP.

With a traditional source (gas, oil) then the impact of insulation will be linear, halve the heat loss and you halve the fuel used (subject to condensing temperature operation but in general)

For a heat pump, halving the heat loss will allow you to reduce the flow temp and this will increase the COP so for a heat pump it matters both the amount of heat loss (linear) and the flow temp hence getting 'double bubble' from improved insulation and why poorly insulated properties can cost a fortune to heat with a heat pump.

It is not a huge effect, my calcs are if you insulated and cut you heat loss by 1/3, with gas/oil you would need 1/3 less fuel. With a heat pump you would make the direct saving of 1/3 of electricity used but also save up to another 10% as a result of a lower flow temp and therefore higher COP.

matt_drummer

https://forums.moneysavingexpert.com/discussion/comment/81904976#Comment_81904976

I am sorry, that is not correct.

The flow temperature required to heat any property with any heat source depends on the size of the emitters, not the level of insulation.

Bigger emitters deliver the required heat at lower flow temperatures.

Bigger heat loss (poor insulation) just needs more heat and that can be delivered by at low flow temperatures with enough emitter capacity.

A well insulated property with emitters that are too small still won't be able to run at low flow temperatures.

michaels

Yes but for a fixed size set of emitters if the heat loss and therefore the heat transfer required is larger then the flow temperature needs to be higher.

So reduce hourly heat loss from 10kw to 7kw via increased insulation and the flow temp can be reduced from say 45c to 40c. Any heat source you save 3kwh per hour due to the insulation, heat pump you also save another approx 1kwh per hour due to higher heat pump efficiency with a lower flow temp.

I think your arguement is that you could have a 40 flow temp in either scenario if you have appropriately sized emitters. Mine is that for a given set of emitters adding insulation will bring a double gain via lower flow temp in addition to the lower heat loss.

matt_drummer

The discussion was about whether poor insulation makes heat pumps unsuitable.

It doesn't because you can still run low flow temperatures with appropriately sized emitters.

Of course better insulation is desirable but it isn't always possible.

That does not mean that a heat pump cannot work as well in such a property as it would in a well insulated one.

Your reply was incomplete as it makes it sound as if the only way to get acceptable efficiency making a heat pump viable is to insulate more by reducing the heat loss.

The only way to get the best or even acceptable efficiency from a heat pump is to have an appropriately sized heat pump for the heat loss and run at the best flow temperature (not always the lowest) by using correctly sized emitters.

The insulation only affects the size of heat pump required, better insulation means a lower heat loss and a smaller heat pump.

You have it the wrong way around, emitters affect flow temperature and insulation determines heat loss and therefore heat pump size.

Some readers may think that you could install a heat pump, then improve insulation and reduce flow temperatures to get acceptable efficiency.

That is likely to cause issues as the heat pump will be too big and will not be able to run at the desired low flow temperatures.

You can always add emitter capacity after installation to reduce flow temperatures but adding insulation to reduce flow temperatures is unlikely to work as what is required is a smaller heat pump to match the lower heat loss.

akwexavante

Putting the science and maths and all the calcs to one side. For me, i cannot escape the fact that when i had my ASHP installed i was not a happy chappy. High bills and not warm enough. I seriously considered chucking it in a skip and starting again with something else.

Researching very much supported my gut feeling that my house was not adequately insulated. I was fortunate that the house that i had moved into needed a lot of work to modernise it in general. Built in 1930 i don't think a single penny had been thrown at it since it was built (It had been cavity wall insulated). So over a couple / three years room to room i have insulted well as part of modernising the home and re decorating etc.

As time went by the home became more comfortable and my bills went south (a lot).

If i hadn't insulated i would still be paying £2.5K+ yr, £208 month for energy and i would still be complaining about how uncomfortable the home was. I'm now paying £1000 yr ignoring offset from Solar. My home is now warm and comfortable at less than half the cost.

For me, homeowners shouldn't have to fiddle nor gain in-depth knowledge of how to tweek an ASHP heating system at all. An installer should install correctly and the installed system should just perform with nothing for the homeowner to do except perhaps balance up radiators room to room and set a room temperature on the room stat.

NOBODY should have to become knowledgeable about flow temperatures, charts, weather compensation and more. No homeowner should have to gain complex insider knowledge of the inner workings of an ASHP heating system.

It's possible that my installer "Got It Wrong" and i should have a larger ASHP!? If i had a larger / different ASHP or and if it had been done right in the first place and my annual bill was no more than the national average i think i would have been happy with that and wouldn't have insulated the home as i have done. My gut feeling is that the installer got it wrong and or the installation wasn't completed as it should have been and or the surveyor got his calcs wrong.

I'll say this again, again and again and many may disagree, that's OK……… A very unhappy chappy insulated his home to get his energy bills down and get a warmer house. AND IT HAS WORKED.

I honestly do not think that any amount of tweaking would have reduced my bill by more than half and increased the comfort of the home as much as i have.

Someone posted that they had an old country cottage with thick walls, no insulation, earthen floors etc etc, and they had an ASHP and were comfortably warm, i'd like to know what there energy bill is like.

Put a big enough ASHP into house with no windows and doors, and if it's truly big enough! it will warm the house up to 27 degrees!!!!!!! i wouldn't want to have that bill to pay every month!!!!!!!!!!!!!

If a homes energy bill was £1600yr before an ASHP was installed, it should not cost more after an ASHP is installed, and many promise that bills will be much lower, and in many cases this is not happening.

NedS

@akwexavante said:

"If a homes energy bill was £1600yr before an ASHP was installed, it should not cost more after an ASHP is installed, and many promise that bills will be much lower, and in many cases this is not happening."

How much someone pays before and after is a function of the unit cost of electricity and the efficiency (COP) of the heat pump. It has absolutely nothing to do with how well insulated the property is.

If the unit rate of electricity is 4 times the price of gas, and the heat pump has a SCOP of 4, then the heat pump will cost the same as a gas boiler (actually less, as this assumes the gas boiler is 100% efficient, which it isn't).

@akwexavante said:

"Putting the science and maths and all the calcs to one side. For me, i cannot escape the fact that when i had my ASHP installed i was not a happy chappy. High bills and not warm enough. I seriously considered chucking it in a skip and starting again with something else."

This is because the system was not designed correctly and was probably not big enough for your property. Maybe you told the installers that you were planning future insulation upgrades and they sized the system to accommodate for this. However, you would have had exactly the same outcome with a similarly sized gas boiler so it is nothing to do with the source of heat.

@akwexavante then said:

"Researching very much supported my gut feeling that my house was not adequately insulated. I was fortunate that the house that i had moved into needed a lot of work to modernise it in general. Built in 1930 i don't think a single penny had been thrown at it since it was built (It had been cavity wall insulated). So over a couple / three years room to room i have insulted well as part of modernising the home and re decorating etc."

"As time went by the home became more comfortable and my bills went south (a lot)."

Well yes, you've added more insulation and reduced the heat loss, so of course your bills will reduce and the house will feel warmer.

It's not that your house was previously inadequately insulated, it's that your heat pump was insufficiently sized to provide the correct amount of heat required to heat it. By adding more insulation you have reduced the heat loss down to the range in which the heat pump is able to adequately heat it. As stated above, this was a design fault of the original system, not an insulation issue.

@akwexavante said:

"I'll say this again, again and again and many may disagree, that's OK……… A very unhappy chappy insulated his home to get his energy bills down and get a warmer house. AND IT HAS WORKED."

"I honestly do not think that any amount of tweaking would have reduced my bill by more than half and increased the comfort of the home as much as i have."

Well of course it has worked, because you've completely changed the dynamics (heat loss) of the property. Equally, installing a correctly sized heating system in the first place would have worked too.

Listen, no one is arguing that adding more insulation is a great thing to do, and will reduce your heating bills. It absolutely will, and it will reduce those heating bills regardless of whether you have a gas boiler or a heat pump, because you'll need less heat. But it is absolutely NOT a precondition or requirement to having a heat pump which can heat your home efficiently regardless of whether your heat loss is high due to low insulation levels or low due to high insulation levels (because efficiency is not a function of heat loss!). It will just cost you more to heat a poorly insulated home, with both gas and ASHP. Perversely, my own heat pump would be even more efficient if I had less insulation (but obviously my bills would be higher as a result). If you understand how that statement can be true, then you are starting to understand the relationships involved.

Any time anyone asserts that heat pumps aren't suitable for poorly insulated homes, and uses CAPITALS to make their point, I will call them out as they are simply wrong on all levels.