Ground Source Heat Pump - anyone got one?

edited 30 November -1 at 1:00AM in Greenfingered MoneySaving
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pinklady21pinklady21 Forumite
870 Posts
edited 30 November -1 at 1:00AM in Greenfingered MoneySaving
Hope this is the right board for this question:
I am currently refurbishing a victorian farmhouse and 3 cottages.
We intend to let out the cottages, and live in the main farmhouse.

No current "proper" heating systems in any of them, only open fires or plug in heaters.
Going to be insulating as well as we can as part of refurb - underfloors, lofts and internal walls.

Question is - what is best system for heating and hot water in all of the properties either individually or a "district" type system for all of them?

Would like to go for a renewable system if possible and feasible given the limitations of the structure and getting it as energy efficient as we can.
Thinking Ground Source, as we have a lot of land around that is fairly wet.
Main issue is expense of installing it, and whether it is worth it by offsetting cost with either the domestic or non domestic RHI.
Looks like with domestic, the RHI pays a higher rate per unit, it is not metered and lasts for 7 years.
Non-domestic will pay a lower rate per unit, has to be metered and will last for 20 years.

1. Anyone with a GSHP - what are pros and cons?
2. What questions should we ask of any installer?
3. RHI for multiple properties - all the cottages are self contained, likely to be eligible for non-domestic RHI scheme - assuming we get a system big enough for heating and supply of hot water to all of them.
4. RHI - are we better going for domestic RHI for each property and is it possible to apply for RHI on more than one domestic property?
5. If we also decide to install a boiler stove in one room in each of the houses to supplement heating and hot water, is this going to foul up any RHI application?
6. Also thinking about a Solar Thermal system to raise water temperatures and Solar PV to generate electricity which will also power the GSH pump. Any possible snags with that?

Thanks all!


  • Just realised this is probably better posted on the Green Energy Board. I will cross post on there too - and in meantime if anyone can help with additional info I would be most grateful. Thanks!
  • DaftyDuckDaftyDuck Forumite
    4.6K Posts
    Part of the Furniture 1,000 Posts Combo Breaker
    I did look over on the green & ethical, and no replies over there, and I'm more at home in the garden, so...

    With old properties that leak heat (and mine is a large old farmhouse) ground and air heat source pumps can be problematic. They generally run the heat output (usually, but not always radiators) at a lower temperature than, say, oil or gas, so are slower to heat the house, and require better insulation. I guess you know that, but when you start to play with the maths, it may come as a nasty shock.

    You can still use them, but you will lose some of the environmental benefits. You'll need to oversize the radiators more than you might with gas, and will have to insulate more than might suit the house.

    I have a complex system, with a large thermal store (it will be two connected ones soon), connecting wood burners, a.s.h.p., oil boiler, and thermal. It was a challenge to get any one to install it right , I had to do a lot of the sums and diagrams myself, it took an engineer from Mitsubishi a couple of days to configure it (they were interested to see if it would work... which may not install confidence), and I guess I'm the only one who really understands it. I do have a relevant-ish PhD, which helped a bit, but much of it was done in hope rather than science, and it was partly done for fun. (I am eccentric...) It's probably the sole reason my wife hasn't chucked me out... that I understand the heating system, not my eccentricity! :p

    Because of the combined nature of my heating system, and the fact I grow my own wood, I'm not eligible for rhi or any other eco payment (go figure!) but I heat an eight bedroomed house for well under a thousand pounds a year. I think you will find that, if you stick solar PV or solar water on the heating side, you'll lose rhi, but the rules do keep changing. I have no idea how the multiple property side of yours plays out with rhi either.

    I also let out properties. The one simple rule for that is: keep the systems there as simple as possible, for a tenant will screw it up if they can, and they will want a quick fix moist of all! They all have combined boilers, with backup electric showers. I would recommend the same to you. A complex heating system will also deter quite a few good tenants, and you won't be paying their heating bills, will you?
  • Thanks DaftyDuck for the really interesting response!
    I have only visited one older property with GSHP and you are quite right, the radiators were huge! The house was not terribly warm either....
    We are also wondering where to find someone with the experience and nouse to be able to install the system and get it working properly.

    My thoughts are that as we are taking all the properties right back to the walls to do other repairs, it makes sense to retrofit insulation everywhere we can, which will help with the energy efficiency and general thermal leakiness.
    At the same time, we would install an underfloor heating system, which we would hope would provide a large enough surface area to maintain a reasonable temperature in the house.
    On the coldest days, we would light the wood burner. Ideally I would also want a back boiler too, but I think that might foul up the RHI.

    It would seem that if we can make the numbers work, we could get the system to pay for itself via RHI over 20 years, and possibly even see some income from it eventually.

    I agree though, apart from the substantial initial capital cost, there are other challenges:

    1. Tenants who don't understand how the system works.
    2. Not messing up the RHI by installing non-compatible elements.
    3. Other things I have not thought of yet.....

    On a related note - we also have enough land to grow wood for fuel - there is some standing wood there already, but we will have to plant more for use as it matures.
    In your experience, what would be the wisest species to plant for a reasonable crop in say 10 - 20 years time?
  • DaftyDuckDaftyDuck Forumite
    4.6K Posts
    Part of the Furniture 1,000 Posts Combo Breaker
    I have recently planted two acres of mixed hazel, willow, and sweet chestnut (plus some other trees in that bit that aren't cut for firewood, but are left for wildlife and looking good). I will coppice that on something like a six year cycle, varying on species and size needed. That's more than enough for me and two other houses.

    Until then, I'm cutting wood from the rest of the farm, and there's plenty to share out as well. However, preparation time will be dramatically reduced when it's all in one place, and the right size to harvest.

    With any heat pump, the low temperature output is a major problem. In luke cold weather, that's not a massive problem, but as winter gets colder, the problem worsens. With a leaky old house.... and when you come back from a winter holiday, it could take days to bring the house back to warmth, right when those solar panels do nothing! So, you pay for your leccy... and freeze ast the same time.

    We get the high temperatures we want on the heating circuit by using multiple coils in a thermal store: the heat pump will run for free whenever it can, and some energy is stored. The temp. in the t.s. can then be raised by a high temperature output like wood burners or oil, and the store can then release that directly to the heating system, or hot water. Any sunlight, and that electricity gets used, and if it doesn't, it gets stored as heat.... When oil burner, log stoves are on, and we are unloading the t.s., we can output well over 100kW with no trouble..., not that we've ever needed to!

    I ended up working out that, to be rhi-compliant, I'd have such a less-efficient system that I couldn't bear to do it! I could sell my wood, buy in wood pellets, do that at a profit, then claim the rhi... but I couldn't bring myself to do that! I could drop the wood and solar heating input... but that would cost me too... so I just went ahead and did it my waaay...

    It's still far from perfect, but I did do it as a fun project as much as anything. Oh, and Mitsubishi were intrigued, and I got some bits from them for almost free... That means they can now charge other folk vast sums because they know it works! :rotfl:

    Whatever you do for yourselves, make sure your tenants have a temperature dial and a switch, and no more!
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