# What does the forum think of heat pumps?



## Yellow Fang (29 Apr 2021)

Would you get one? If so, what sort? If not, what puts you off?
What would you have it with, e.g. underfloor heating, new radiators, more insulation, solar hot water, PV panels?


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## Eric Olthwaite (29 Apr 2021)

Yellow Fang said:


> what puts you off?



The second law of thermodynamics, aka "you can't move heat from a cooler to a hotter".
Ultimately, no amount of pipework routing trickery can avoid this.


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## Ridgeway (29 Apr 2021)

They are a standard install here, practically no houses built use anything else. Oil is now off limits here and gas is getting harder to get approval for new installs.

The only off putting part is the initial install cost although that tends to depend upon how deep you need to drill (here it's usually 100m).


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## Yellow Fang (29 Apr 2021)

Eric Olthwaite said:


> The second law of thermodynamics, aka "you can't move heat from a cooler to a hotter".
> Ultimately, no amount of pipework routing trickery can avoid this.


Yes you can if you add some electricity. That's the first law of thermodynamics.


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## Yellow Fang (29 Apr 2021)

Ridgeway said:


> They are a standard install here, practically no houses built use anything else. Oil is now off limits here and gas is getting harder to get approval for new installs.
> 
> The only off putting part is the initial install cost although that tends to depend upon how deep you need to drill (here it's usually 100m).


Does it have to be ground source?


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## Ridgeway (29 Apr 2021)

Answering the other points if i were installing a new system here it would be:

PV around 40 x 200w panels
Solar water heater
Heat pump to feed underfloor heating
Insulation overall up to "Minergie" standards (Passivhaus) i think this is called "low energy" in the UK ?

The later is only really achievable if we're talking new build, our house is old so i'll be focusing on the first 3 points over the next years.


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## Ridgeway (29 Apr 2021)

Yellow Fang said:


> Does it have to be ground source?



Doesn't have to be and there's more and more air source but ground source is well established and accepted here. Next install for us will be ground source once the gas boiler dies.....


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## Yellow Fang (29 Apr 2021)

I sometimes wonder if ground source vs air source is a case of the excellent being the enemy of the good enough. People who are interested in it read that ground source heat pumps are better, find out it's more expensive and/or requires digging up your garden. but don't want air source because it's second best, then lose interest.


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## roubaixtuesday (29 Apr 2021)

Eric Olthwaite said:


> The second law of thermodynamics, aka "you can't move heat from a cooler to a hotter".
> Ultimately, no amount of pipework routing trickery can avoid this.



Refrigerators are a figment of my imagination?

shoot. I'd better go eat that cheese pronto!


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## contadino (30 Apr 2021)

I had a MHRV fitted to my previous house and it worked pretty well. We had a couple of kw of pv on the roof so the cost of running it was zero. We went from using the (gas) heating for maybe 4 months each year to a few hours on 11 days in 15 months.

I probably didn't recoup the cost because we moved house, but it'd pay for itself in 3 or 4 years.

When I've got the new house sufficiently insulated I'll be getting one fitted for sure.

ETA: not sure if you meant to include MHRVs as a heat pump but thought I'd chip in anyway


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## annedonnelly (30 Apr 2021)

I've had an air source heat pump for years. It's been no problem at all. I think the first winter after it was installed we had a long, long freeze with temps of about -10C and it worked perfectly.

I also have solar hot water and PVs. And I got new radiators when the heat pump went in.


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## OldShep (30 Apr 2021)

I’ve had a ASHP for ten years. 
installed for £1400, ten years on with no problems I’m now going to give it a service. I could have had it serviced every year at a cost of £120 ( quoted 10 yr ago) to keep a 10 year warranty alive. I think my gamble has won. 
plus side is it’s been very cheap to run and keep the house warm and also cool on the two hot days we get each year. 
down side a homes biggest demand is when it’s coldest outside which is also when the machine is less affective. We’ve always had to supplement with a wood stove winters evenings. The constant air movement gives me a cold nose.
Experience tells me
Sizing and placement of the unit is crucial. I wish I’d put in the biggest I could before 3 phase is required. I wish I’d put the indoor unit in a different location. 
After 10 years we have recently stopped using it and returned to full price electric heating. It keeps us warmer and it costs more than double to run. This experience has also taught us the calculations on heat loss for the living area have been very optimistic. Don’t underestimate how much loss there are from windows and patio doors. 
I looked into buying a bigger better unit and was impressed with a guy near Aberdeen who supplies units produced for use in, I think it was Finland. Claiming real efficiency down to -30C outside. Once bitten twice shy and aged 70 I decided not to take the risk on an outlay nearly three times more than my last foray into heat pumps. If I was still aged 60 then I think I would have taken a punt with his machine. 
i intend, this summer, moving our ASHP to the other end of the house to heat an area less than half of what it does now. I’m fairly confident that will be a success.


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## Yellow Fang (30 Apr 2021)

contadino said:


> I had a MHRV fitted to my previous house and it worked pretty well. We had a couple of kw of pv on the roof so the cost of running it was zero. We went from using the (gas) heating for maybe 4 months each year to a few hours on 11 days in 15 months.
> 
> I probably didn't recoup the cost because we moved house, but it'd pay for itself in 3 or 4 years.
> 
> ...


What's an MHRV?


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## Yellow Fang (30 Apr 2021)

OldShep said:


> I’ve had a ASHP for ten years.
> installed for £1400, ten years on with no problems I’m now going to give it a service. I could have had it serviced every year at a cost of £120 ( quoted 10 yr ago) to keep a 10 year warranty alive. I think my gamble has won.
> plus side is it’s been very cheap to run and keep the house warm and also cool on the two hot days we get each year.
> down side a homes biggest demand is when it’s coldest outside which is also when the machine is less affective. We’ve always had to supplement with a wood stove winters evenings. The constant air movement gives me a cold nose.
> ...



Was that an air to air heat pump, i.e. cold air from the outside, warm air to the inside (rather than radiators or underfloor heating)? What's it power rating?


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## OldShep (30 Apr 2021)

Yellow Fang said:


> Was that an air to air heat pump, i.e. cold air from the outside, warm air to the inside (rather than radiators or underfloor heating)? What's it power rating?


Yes that is A2A experience.
The installer I used back then felt the expense of underfloor wasn’t worthy of the premium of UFH. Whether he was right or afraid of the unknown I can’t say.
whilst I have 2/3 of an acre he also felt my ground is severely shaded with trees any suitable ground would just get colder and colder and once again not worthy of the initial cost.


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## contadino (30 Apr 2021)

Yellow Fang said:


> What's an MHRV?



Mechanical heat recovery ventilator. Pulls warm air from the house and runs it through a heat exchanger pulling cooler air from outside. Doesn't aim to concentrate heat, just not lose it.


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## Drago (4 May 2021)

Been researching this. It is very plausible, and when in and operating its cost effecting, relatively green heat.

Downsides are is the expense installation, and the need for roughly double the amount of radiator area to heat a room to the same temperature as a gas boiler, and thats with ground source.

I wouldn't dismiss the idea, although it appears better suited to a house in the design stage where everything can be better incorporated, particularly the extra rads.


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## TheDoctor (4 May 2021)

They're pretty much the standard in NZ. Certainly where we were, it worked well for both heating and cooling.


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## Yellow Fang (9 May 2021)

I just read that the sale of gas boilers will be banned from 2025, so it looks like we will have to get used to heat pumps.

I don't have central heating in my flat. I only have a gas fire in my lounge, which I don't use much. I have an electric fan heater, which I also don't use much. For hot water I have an electric shower, and two electric water heaters for the bathroom and kitchen sinks. 

In the Orkneys I met someone who had an air-to-air heat pump. The Orkneys are not on the gas grid. It looked quite switch-on-and-offable, which a lot of heat pump systems are not. Hotel rooms often have them too, sometimes combined with air conditioning systems. They don't do hot water though. I wondered whether an air-to-air heat pump that directs warmth to where you are via ducting might be an idea.


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## numbnuts (9 May 2021)

I live in housing association, they are thinking about electric water boilers when the gas ones need replacing, heating is going to be bloody expensive in years to come, more so for older homes.


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## byegad (9 May 2021)

Eric Olthwaite said:


> The second law of thermodynamics, aka "you can't move heat from a cooler to a hotter".
> Ultimately, no amount of pipework routing trickery can avoid this.


A fridge does.


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## yello (9 May 2021)

Yellow Fang said:


> I sometimes wonder if ground source vs air source is a case of the excellent being the enemy of the good enough. People who are interested in it read that ground source heat pumps are better, find out it's more expensive and/or requires digging up your garden. but don't want air source because it's second best, then lose interest.


I think that's a pretty fair assessment.

We looked at ground source - it was not just expensive but cost uncertain/open. There's a lot of granite in our area so installers couldn't guarantee costs of sinking the borehole. We then looked to air source but I was less than convinced as to their effectiveness. Sure, they use them in Scandinavia (cold countries) but the houses there tend to very well insulated too. Air source might be okay for under floor heating in a well insulated house but I didn't feel it was our answer.

We opted for wood pellet in the end. Not super cheap, neither outlay nor running costs, but does the job well enough. It runs rads, underfloor heating and provides hot water. I also spent a fair amount on insulation. Bang for buck, it was probably that that was the most effective spend.


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## JhnBssll (10 May 2021)

As junior mechanical building services engineers we were taught that conventional radiators are designed to run with a ~60 degree differential between flow and return. Heat pumps on the other hand produce a much lower flow temperature and therefore a lower differential so it's not as simple as removing a boiler and plumbing in a heat pump which to date has minimised their use. The lower flow temperatures are much better suited to underfloor heating, where you're essentially heating the fabric of the building which then heats the air within in, rather than the other way round with radiators. Underfloor systems run by heatpumps in well insulated buildings will run almost constantly at a low output to maintain a steady temperature, unlike a boiler which will fire in short bursts causing the air temperature to fluctuate slightly throughout the day. The downside is not many people are prepared to dig their floor up, and first floor installation in existing buildings can be irksome. This was true 15 years ago anyway, the technology has no doubt come on but I suspect the limitations remain.

Part L of the building regs are constantly being updated and will almost certainly ban the installation of gas and oil boilers in new builds within the next few years. This will likely improve the cost of heat pump installation in new builds, but is unlikely to have much effect on retrofit costs in the short term. My understanding is that gas and oil boilers will still be available as a replacement in homes already heated by these means, otherwise we'd all have a bit of a problem on the horizon 

If I were building a new home now it would be super insulated on the outside with a high internal thermal mass, underfloor heating via ground source heat pump and PV panels on the roof to offset the running costs  Combined with heat recovery ventilation and clever design to minimise the heating effect of the sun through windows and you've got yourself a comfy home with minimal energy use. In theory at least  Controlling moisture is a challenge as the building has to be basically sealed to work properly so the ventilation design is critical, especially around showers, hobs etc where large amounts of steam are generated.

This answer is much longer than expected, sorry  In response to the original question, they're great in the right circumstances but not really suitable for many existing buildings without significant outlay.


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## yello (10 May 2021)

Oil boilers have been phased out/banned already in France, from next year I believe. You can still have one, of course (you don't need to remove it) but you can't install a new one and I don't believe you can get one repaired either, not legally anyway. The latter is obviously going to be a bit of a grey area since plumbers will do cash jobs, and there will be stocks of spares sitting on shelves - and, of course, not everyone has the ready cash to stump up for a new heating system.

There's been a big govt push of later to get people on to more 'eco' forms of heating, with all manner of grants, loans and tax incentives over the years. Air heat pumps are part of that push and are very popular - perhaps even the default option for new builds - and the sight of the units fixed to the side of houses (new and old) is not at all uncommon.


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## BrumJim (10 May 2021)

JhnBssll said:


> As junior mechanical building services engineers we were taught that conventional radiators are designed to run with a ~60 degree differential between flow and return. Heat pumps on the other hand produce a much lower flow temperature and therefore a lower differential so it's not as simple as removing a boiler and plumbing in a heat pump which to date has minimised their use. The lower flow temperatures are much better suited to underfloor heating, where you're essentially heating the fabric of the building which then heats the air within in, rather than the other way round with radiators. Underfloor systems run by heatpumps in well insulated buildings will run almost constantly at a low output to maintain a steady temperature, unlike a boiler which will fire in short bursts causing the air temperature to fluctuate slightly throughout the day. The downside is not many people are prepared to dig their floor up, and first floor installation in existing buildings can be irksome. This was true 15 years ago anyway, the technology has no doubt come on but I suspect the limitations remain.
> 
> Part L of the building regs are constantly being updated and will almost certainly ban the installation of gas and oil boilers in new builds within the next few years. This will likely improve the cost of heat pump installation in new builds, but is unlikely to have much effect on retrofit costs in the short term. My understanding is that gas and oil boilers will still be available as a replacement in homes already heated by these means, otherwise we'd all have a bit of a problem on the horizon
> 
> ...



Thank you for that. Very interesting.


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## Phaeton (10 May 2021)

Yellow Fang said:


> Would you get one? If so, what sort? If not, what puts you off?


The sales guy, all he is interested in is signing up up for the loan so he gets his commission, same as if you enquire about solar panels.


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## Yellow Fang (10 May 2021)

JhnBssll said:


> As junior mechanical building services engineers we were taught that conventional radiators are designed to run with a ~60 degree differential between flow and return. Heat pumps on the other hand produce a much lower flow temperature and therefore a lower differential so it's not as simple as removing a boiler and plumbing in a heat pump which to date has minimised their use. The lower flow temperatures are much better suited to underfloor heating, where you're essentially heating the fabric of the building which then heats the air within in, rather than the other way round with radiators. Underfloor systems run by heatpumps in well insulated buildings will run almost constantly at a low output to maintain a steady temperature, unlike a boiler which will fire in short bursts causing the air temperature to fluctuate slightly throughout the day. The downside is not many people are prepared to dig their floor up, and first floor installation in existing buildings can be irksome. This was true 15 years ago anyway, the technology has no doubt come on but I suspect the limitations remain.
> 
> Part L of the building regs are constantly being updated and will almost certainly ban the installation of gas and oil boilers in new builds within the next few years. This will likely improve the cost of heat pump installation in new builds, but is unlikely to have much effect on retrofit costs in the short term. My understanding is that gas and oil boilers will still be available as a replacement in homes already heated by these means, otherwise we'd all have a bit of a problem on the horizon
> 
> ...


That's the thing with these big, complex systems. They are alright for new builds. However, the government seems to have a one size fits all approach to heating buildings.
A system like the one you described:

is on all the time - I am not in much of the time. 
heats all the house - I don't need all my flat heated. 
heats water tank- I don't use that much hot water. 
controls air moisture - just not a problem for me really. 
works best with a highly insulated building - my flat has solid walls, sash windows and no access to the roof space. 
has a heat recovery ventilation system - what if it breaks down? Someone installed an extraction fan in my bathroom years ago. Now it is just a hole in the wall.


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## JhnBssll (10 May 2021)

Yellow Fang said:


> That's the thing with these big, complex systems. They are alright for new builds. However, the government seems to have a one size fits all approach to heating buildings.
> A system like the one you described:
> 
> is on all the time - I am not in much of the time.
> ...



I don't disagree, and that is sort of my point - these new systems are excellent in a new build that's properly maintained. They're not so great when bits of it are installed in older properties without properly considering the knock-on effects.

Regarding controlling moisture, you won't have a problem because old buildings are not even close to airtight. It becomes a problem when you seal the space up in order to prevent heat loss, which then has to be solved with mechanical ventilation. Heat recovery units are pretty simple devices, just a pair of fans, a filter and a plate to plate heat exchanger, but the filters will need cleaning periodically and the fans will have a design life so you're right, they're not fit and forget...


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