Air and Ground source heat pumps?

[stockhausen]

Does anyone here have any practical experience of having either an air or ground source heat pump installed?

The Government seem (in the short term) to be encouraging their use and since I should probably be thinking of replacing my ageing gas fired boiler I do wonder whether a (vertical) ground source heat pump is worth investigating (LINK).

 

[Adam_151]

I'd say try and avoid the air source as your main source of heating if possible, the efficiency goes right down in colder weather when you need it most as its having to work a lot harder to 'harvest' the same amount of thermal energy from outside, ground source tends to be a lot mroe stable, but then you have the cost of sinking it all into the ground. Either one you are looking at lower flow temperatures than a gas boiler, so oversized radiators are generally required to get the energy into the rooms, and I'd only consider it in a modern well insulated house, I think in a drafty older house you'd never get the rooms very warm.

I've been to new build properties with air source to address eelctrical snags, and no one seemed impressed with the heating systems, it probably can work, but needs the building and the heating system all designed to work in harmony, passive haus kind of design, rather than just chucked in because it was a requirement of planning with little thought to how itll work in practice

 

[JBuk]

I’ve looked into air sourced and tbh they are not worth it unless you have a modern well insulated home and even then you may need something extra when it’s very cold, plus the initial costs will take quite a few years to recoup in any savings over a gas boiler

I had someone call round doing house to house trying to get people onto a green homes grant scheme and even with the extra money it wasn’t worth it

 

[Armageus]

I've got an ASHP and previously posted my thoughts in this thread:
https://www.overclockers.co.uk/foru...ump-renewable-heating.18896088/#post-33847773

 

[b0rn2sk8]

I had one quoted as part of the green homes grand and gas worked out cheaper before the cost of retrofitting most of my rads with bigger ones. I did a write up in the green homes grant thread.

If your not on gas and have a well insulated home, have a look. If you have gas I wouldn’t bother unless the costs come down, the incentives are increased or gas becomes more expensive relative to electricity. If your home isn’t well insulated, do what you can to improve that first.

 

[ZG002]

snip

Echo this, I've fitted both in the past.

Ground Source tend to be installed more in commercial environments basically due to initial cost and you need the space to sink the loops but are the more stable system due to ground temps being much better regulated. We only ever installed one domestic system and they went with under floor heating, I never got to see the system in it's final state when the build was complete unfortunately.

Air source can work, but as said you really want the house designed around the system and not the system retro fitted. We fitted about 20 for a council as an experiment in some 1/2 bedroom flats that were likely build in the 60's and they were removed within 2 years, just didn't work.

My current employer do run some passive houses which when working are great but we always seem to have one issue or other on the go, seem to go around in circles maintaining them and it's only a small stock.

 

[Terminal_Boy]

There’s big government funded scheme on at the moment in France where you can have an Air Source system installed for €1. The general consensus is that you’ll only see a very marginal benefit in an old stone house that can’t be insulated to modern standards.

As we have a modern condensing boiler gas CH system, I’m not seeing the need to increase our electricity bill for very little gain.

 

[Mysterae_]

I'm always interested when this subject pops up. I'd love to go ground source heating at least in theory as we have the space for the ground loops. The issue I foresee is the floor of the house is concrete so under floor heating is going to be difficult and expensive to install. We don't want to increase the size of the existing radiators either. There's a company with an industrial router that can make tracks in the concrete to retrofit UFH, but again expensive. My last man-maths calculation was around £35k for a complete installation, with about £28k of that returned from the DRHI over 7 years (if things were perfect).

I have a site visit planned next year from Home Energy Scotland to assess the house and discuss the options. I doubt air source will be one of the options though.

 

[theone8181]

I'm always interested when this subject pops up. I'd love to go ground source heating at least in theory as we have the space for the ground loops. The issue I foresee is the floor of the house is concrete so under floor heating is going to be difficult and expensive to install. We don't want to increase the size of the existing radiators either. There's a company with an industrial router that can make tracks in the concrete to retrofit UFH, but again expensive. My last man-maths calculation was around £35k for a complete installation, with about £28k of that returned from the DRHI over 7 years (if things were perfect).

I have a site visit planned next year from Home Energy Scotland to assess the house and discuss the options. I doubt air source will be one of the options though.

Surely your just lay underfloor heating on top of the concrete and trim doors to suit? I'd be weary about tracks in concrete incase the dpc gets punctured (although not sure how deep it is).

 

[Mysterae_]

@theone8181 , underfloor heating on top of the concrete floor is definitely the most popular and preferred method due to costs and disruption and there's low profile versions too. The problems with UFH (almost all types) is you have to be careful with what carpet you lay, it has to be low tog otherwise the heat gets stifled. You can't just turn up the heating like you can with radiators if you're feeling a bit chilly, likewise turning the temp down takes a while too. However, I like the thought of every room being individually monitored and controlled, optimising the energy use. Still in two minds if it's good or bad!

 

[theone8181]

@theone8181 , underfloor heating on top of the concrete floor is definitely the most popular and preferred method due to costs and disruption and there's low profile versions too. The problems with UFH (almost all types) is you have to be careful with what carpet you lay, it has to be low tog otherwise the heat gets stifled. You can't just turn up the heating like you can with radiators if you're feeling a bit chilly, likewise turning the temp down takes a while too. However, I like the thought of every room being individually monitored and controlled, optimising the energy use. Still in two minds if it's good or bad!

I looked into for my man cave they thought it was a lot of work so bought an electric rad instead.

 

[Rroff]

I always wonder what the environmental impact would be if ground source heat pumps became mainstream - large scale sourcing of energy like that must have some effect.

 

[clv101]

My parents had a ground source heat pump installed a few years ago. Pretty straightforward, but needed to change all the radiators for extra large ones. The RHI pays out a crazy amount, pretty much paying for it inside a decade.

 

[mid_gen]

I always wonder what the environmental impact would be if ground source heat pumps became mainstream - large scale sourcing of energy like that must have some effect.

The sort of energy being pulled to warm houses is absolutely inconsequential compared to sorts of volumes of energy in the ground from both the incoming radiation from the sun, and the internal radioactivity in the Earth.

It's akin to worrying that taking a bucket of water from the sea is going to make sea levels fall.

 

[Slade2]

The sort of energy being pulled to warm houses is absolutely inconsequential compared to sorts of volumes of energy in the ground from both the incoming radiation from the sun, and the internal radioactivity in the Earth.

It's akin to worrying that taking a bucket of water from the sea is going to make sea levels fall.

I believe its not inconsequential for systems that have been installed for extensive periods of time the ground does struggle to replace the heat that gets taken from it. Some systems now are combining ground source heat pumps with a small solar power array to use the free electric to replace the heat taken by the pump and stop the ground from freezing.

 

[mid_gen]

I believe its not inconsequential for systems that have been installed for extensive periods of time the ground does struggle to replace the heat that gets taken from it. Some systems now are combining ground source heat pumps with a small solar power array to use the free electric to replace the heat taken by the pump and stop the ground from freezing.

I guess there's a localised effect....but on a macro scale there's absolutely no issue with pulling heat from the ground.

 

[1pudding1]

I believe its not inconsequential for systems that have been installed for extensive periods of time the ground does struggle to replace the heat that gets taken from it. Some systems now are combining ground source heat pumps with a small solar power array to use the free electric to replace the heat taken by the pump and stop the ground from freezing.

Only a badly designed system would end up freezing the ground. As long it's calculated and designed properly, the collector will be large enough such that the the ground wont get too cold too quickly and freeze, and will have plenty of scope and time to recover via sun/rain heat transfer. We've got a GSHP, had it for 6 years, and have certainly never noticed any effect, no localised frost or anything like that. You get the RHI for 7 years, and ours will just about pay off the total install cost, may end being maybe £1k short, but that's prob been saved in running costs over the years quite easily.

I've just today finished installing a 3 unit air2air heat pump (or air con units), and they're in well insulated rooms so will heat and cool them quite comfortably. As long as any heat pumps capacity is greater than the largest heating/cooling requirement of a room and can transfer that to a room, they work great.

 

[Danm54]

However, I like the thought of every room being individually monitored and controlled, optimising the energy use. Still in two minds if it's good or bad!

I've used an underfloor manifold to supply radiators, got seperate time and temperature controls in every room.

It's great for only heating rooms we need in the morning and can also heat them to a lower temp if needed.
Plus in the summer we can turn a towel rail on for an hour or so.