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Air source heat pumps

WouldBe

WouldBe

Dislicksick
Are they worth it?

I've been looking at an ASHP to complement my wood burning boiler stove but from what I've seen so far I'm not sure it's worth it. The cheaper ones have all the controls on the outside unit with no way of controlling them from inside the house and in the event of a power cut (or trying to control it by turning the power on/off) you have to reset it by pressing a button on the outside unit. More expensive units could possibly be controlled from inside but don't heat the water hot enough to prevent bacterial growth. Doing a general search suggests that unless they are installed perfectly then they don't work very well and cost a fortune to run and I need to keep things as cheap as possible for installation and running costs.
 
Yeah heat source pumps can be great. Particularly if your using something like good ground source pump to warm a underfloor heater to the mid 20s.

However if you want to get tap or bath water you end up slapping a electric heater to it to bring it up high enough to kill legionnaires. This can destroy the efficiency of the system.


My dad studied this problem as part of his post grad stuff.
 
When I looked the cheaper ones only had an an inside unit and as you say need to heat water hot enough to prevent bacterial growth. Apparently your house needs to be well insulated. I wondered about them for a while, also for the ones that combined air conditioning/dehumidifying.

Eta the ones I looked at were just for space heating.
 
They are low intensity heat sources, so if your house isn't well sealed and insulated, you will be wasting money. The internet is full of people moaning about their heating bills going UP after installing one because they haven't blocked up all the leaks in their house.
 
two sheds said:
When I looked the cheaper ones only had an an inside unit and as you say need to heat water hot enough to prevent bacterial growth. Apparently your house needs to be well insulated. I wondered about them for a while, also for the ones that combined air conditioning/dehumidifying.

Eta the ones I looked at were just for space heating.
Click to expand...
One of the cheaper ones I looked at could cool the water to 6C to pump round the radiators to provide cooling but I couldn't do that as it would have to pump into the thermal store to start with so would lose the hot water facility.

House is well insulated and needs some more putting in yet.
 
Crispy said:
They are low intensity heat sources, so if your house isn't well sealed and insulated, you will be wasting money. The internet is full of people moaning about their heating bills going UP after installing one because they haven't blocked up all the leaks in their house.
Click to expand...
That was the main problem I saw. Mine is quite well insulated. I only use 10kg of wood over 4 hours per day and the house is toasty (sometimes too toasty) and a tank full of hot water. Just a pain in the arse keeping it fuelled and can't put it on for the odd hour if it's a bit chilly.
 
Mine's an old house so still I'm sure quite leaky. I've added secondary glazing and insulating wallpaper plus a conservatory which really helps heating the house up. I really only need heating (Cornwall) November to March and normally the Rayburn is enough although it doesn't really touch the radiators. January/February I've got a fan heater for upstairs which gets me through.
 
Crispy said:
They are low intensity heat sources, so if your house isn't well sealed and insulated, you will be wasting money. The internet is full of people moaning about their heating bills going UP after installing one because they haven't blocked up all the leaks in their house.
Click to expand...

My dad has one, for his draughty old country cottage. I think the benefits are pretty marginal.
 
ASHP's are old technology that have been disproved a number of times over the decades. At best you will get 2 units of heat for 1 unit of electricity. As electricity is 4 times the price of electricity they end up costing at least twice as much as gas boilers to run. As well as costing a huge amount more to install initially.
 
Oh. Here is what I was looking for.

Analysis of data from heat pumps installed via the Renewable Heat Premium Payment Scheme (RHPP) to the Department of Energy and Climate Change (DECC) A major contract with research consortium from UCL, BSRIA, SP Technical Sweden for UK Department of Business, Energy and Industrial Strategy (BEIS), 2014-2017.
 
what said:
ASHP's are old technology that have been disproved a number of times over the decades. At best you will get 2 units of heat for 1 unit of electricity. As electricity is 4 times the price of electricity they end up costing at least twice as much as gas boilers to run. As well as costing a huge amount more to install initially.
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air sourced heat pumps aren't like ground-sourced ones they do only start at £300 or £400, and there's no gas where I am. I'd get Calor gas but I don't trust me with gas really and they throw loads of moisture into the air.
 
Crispy said:
Yes, but the volume of a fridge is limited, the door is rarely opened and the seal is 100% effective.
Click to expand...
And the ASHP doesn't need to be on all the time. Ones I looked at produced water at 55C. My rads are fed through a thermostatic mixer valve set at 43C ish. So I don't see why an ASHP needs to run all the time.
 
I’m still thinking of this. Over winter I need four loads of wood so say £300 total. My electricity consumption is about £50 more in winter which I’m assuming is mainly a 1 kW fan heater upstairs at night that I use to top up the rayburn when it’s particularly cold (around 250 units over say 5 months so an average of 1 hour/night & 3 hours/night when freezing).

The Rayburn’s very nice and it does warm the house in winter but am somewhat concerned about particulates (although my chimney sweep told me he rates Rayburns almost as highly as the ‘energy efficient’ ones that are becoming requirement, and I have seen that the new approved ones also produce stupidly high particulate levels).

It’s an old house and so, although I’ve done what I can, it isn’t sealed. Heat pumps aren’t generally recommended for this, but I think that’s when you’re using them to drive central heating (air-water heat pump). I’d be using it on demand as an air-air heat pump instead of the 1 kW fan heater. Which I’d hope would let me run it at near 1/3 the cost although I’ll need more if the Rayburn won’t be heating the house. The conservatory does warm the house somewhat even in winter so I only really need to heat upstairs for the evenings, and there's only me so don't have to think about anyone else in the house.

Cheapest air-air heat pumps are about £400 so if I can replace the Rayburn that would mean a 2-yearish repayment time.

I think :(
 
two sheds said:
It’s an old house and so, although I’ve done what I can, it isn’t sealed. Heat pumps aren’t generally recommended for this, but I think that’s when you’re using them to drive central heating (air-water heat pump). I’d be using it on demand as an air-air heat pump instead of the 1 kW fan heater. Which I’d hope would let me run it at near 1/3 the cost although I’ll need more if the Rayburn won’t be heating the house. The conservatory does warm the house somewhat even in winter so I only really need to heat upstairs for the evenings, and there's only me so don't have to think about anyone else in the house.

Cheapest air-air heat pumps are about £400 so if I can replace the Rayburn that would mean a 2-yearish repayment time.

I think :(
Click to expand...
From what I understand it's because the water/air temp given out by the heat pump is relatively low compared to normal central heating so the house needs to be insulted better as it's easier to lose the heat.

Do you have a radiator upstairs? It would be easier and cheaper to put in a radiator and plumb it into the Rayburn.

How come you're using so much wood? I only light my wood burner in the evening although I will put the gas fire on for a bit to take the chill off if it's really cold. I only use just over a tonne of wood over winter.
 
Yes
WouldBe said:
From what I understand it's because the water/air temp given out by the heat pump is relatively low compared to normal central heating so the house needs to be insulted better as it's easier to lose the heat.

Do you have a radiator upstairs? It would be easier and cheaper to put in a radiator and plumb it into the Rayburn.

How come you're using so much wood? I only light my wood burner in the evening although I will put the gas fire on for a bit to take the chill off if it's really cold. I only use just over a tonne of wood over winter.
Click to expand...
yes it wouldn't work with heat pump feeding radiators, they wouldn't get hot enough. I do have radiators upstairs plumbed into rayburn but I've only ever really used rayburn for an hour or so a night for cooking so the radiators don't get hot.

Not sure how much a tonne of wood costs - I get about a truckload's worth for £150, possibly just over a m2 but I'm really not sure.
 
two sheds said:
Yes

yes it wouldn't work with heat pump feeding radiators, they wouldn't get hot enough. I do have radiators upstairs plumbed into rayburn but I've only ever really used rayburn for an hour or so a night for cooking so the radiators don't get hot.
Click to expand...
How do you heat the rest of the house?
two sheds said:
Not sure how much a tonne of wood costs - I get about a truckload's worth for £150, possibly just over a m2 but I'm really not sure.
Click to expand...
I've just had a tonne of briquettes delivered for £280. Roughly a cubic metre.
 
WouldBe said:
How do you heat the rest of the house?
Click to expand...
I don't really :) I've got a burner for end room and fireplace for middle room but only light them occasionally to give the rooms a bit of a warm. The conservatory is warmish in winter so I spend day in there, spend evenings upstairs which is where I really need the warmth.

WouldBe said:
I've just had a tonne of briquettes delivered for £280. Roughly a cubic metre.
Click to expand...
My wood is byproduct of woodland management (not air dried but <20% moisture from what I've seen), but I should perhaps check on price of briquettes. Isn't that about the same though? I have two £150 loads in a winter.
 
WouldBe said:
I've just had a tonne of briquettes delivered for £280. Roughly a cubic metre.
Click to expand...
Must be some dense briquettes.

Edit: I'm thinking of BBQ charcoal briquettes, which seem quite light. I think the proper solid fuel ones might have been a lot denser (haven't used them for about 15 years).
 
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