Ground source or air source heat pumps(21 Posts)
Hello, we are starting to restore an old house (fully striped out) and we are trying to work out how to heat the space and water. We are not on mains gas so we are considering what other options we may have apart from oil. Does any one have any experience either making this decicion or with heat pumps? How are they to live with? How cost effective to run? How warm are they? Any advice?
There are all sorts of options:
Of ground source vs air source I prefer ground source.....but I don't know why
I also looked at a small wind turbine which were fab but there were issues with storage of power
Biomass boilers are good but it depends how much heat you need - lots of chopping wood & a wood burner or for more money you can burn those big enormous hay bales (but you need somewhere to store them in the dry)
My aim is to combine our wood burner with some solar panels & we will have hot water nearly all year round.
Have you thought about grey water recycling too? that can work well in this sort of situation (esp on a heat harvesting front)
I dont have any hands on experience but understood that a big part of the decision is related to how much land you have. Ground source needs space. Air source make noise so need to be screened from public living spaces. Hope someone else more knowledgeable is along soon.
Ground source can either be horizontal (over a large lawn or field) or vertical in a very, very deep hole
We have air source heating in our HA house, it is very economical but can be a bit tempermental when the temperature drops (which is when you need it so can be a pita!) However we just turn the wall panel off and on again and it restarts itself fine. It isn't too noisy, we got used to it within days.
my daughter replaced oil with air source heating last year, I love the whirry thing in the garden, it's like a miniature UFO
it seems very cheap to run too, electricity fir her two bedroom house costs about £30 a month in summer and £50 last winter
We don't have a massive garden so we are looking at possibly a very deep bore hole (60m I think). Ground source does somehow seem better (although based on no evidence) but the borehole could make it too expensive. We are waiting for quotes. I was worried about noise and reliability from air source so these views are useful.
I'm a bit worried about the level of maintenance with biomass, chopping and getting wood or storing lots of pellets could be a pita ??
Katymac we are going to fit in the plumbing for grey water recycling to the toilets and washing machine (i do loads of washing) and add the tank to the garden when we do that next.
katymac, I use a large wood burner in the winter for all warm water and to heat all the rads, in the summer I use 3 banks of solar tubes for background heat and warm water which cost zero for 8-9 months of the year. I also use a DC wind turbine and store the energy in reclaimed car batteries (64 in total) this in turn supplies low energy low voltage LED lighting and all my mains powered needs bar washing machine via 2 x 1 kw invertors, again this costs nothing to run.
We also have an old, reasonably large, very draughty house, and switched from oil to a GSHP two years ago.
Supposedly GHSPs work better in modern houses, with good insulation and double glazing, but we have neither of those, and it still works well. The heating is designed to work 24/7 and maintain a reasonably constant temperature with plenty of hot water.
We have it running through cast-iron radiators and under-floor heating (tiles and wood) and it works well for both.
In terms of costs; our running costs are roughly half of what they were using oil, but it really depends on the size of the house and hence which kw unit you will need.
One word of caution, if you do decide to go ahead, then it is probably worth looking at the energysavingtrust and Microgeneration Certification Scheme websites. They also do take a while (in our case a year) to calibrate and stabilise.
Other things to consider are, changing your electricity tariff (you will use more electricity to top up the system when it is not getting sufficient heat from the ground), annual maintenance contract, and space to install it (our system is in a cupboard which is about four feet deep by 10 feet long). You may also need to change your electricity supply to three phase, but this is not usually a problem.
We also have log-burning stoves but these are rarely used.
With respect to land needed, obviously a bore-hole will need less but they seem to cost more, than simply digging trenches - which is what we did round a 2.5 acre field.
Hopefully this helps and I am happy to help if you have any more questions.
Relatives put a GSHP and solar hot water panels in and they're currently having major teething problems to do with the amount of hot water available at any one time, although the temperature of the water seemed excellent. I believe they're replacing the hot water tank with a much larger one?
Yes, we have two hot water tanks - one for the CH and one for household use. That's why you need a reasonable amount of space for all the equipment. Their engineer should have raised this as an issue in advance though.
This isn't exactly a direct answer to your question, but depending upon the direction your house faces, have you considered passive solar heating as a starting point? Check out Ecospheric:
I meant to say the video on that website gives some interesting ideas
Charley - what size are your tanks?
We have a 4bed, 3 bathroom house with existing solar thermal. Major re-fit currently underway includes woodburner which produces 14kW of heat to a thermal water store. I have had one system plan whcih recommends a 750L Akvatherm and another which recommends a 475L Excel thermal store.
But the plumber doing the installation reckons we only need a 300L thermal store. As this is the smallest size Excel make it doesn't seems big enough to me ( house is approx 2000 sq ft). If we fit this pricey woodburner and the thermal store isn't big enough to actually store the heat I shall lynch him!
We thought about ground source but it seems most efficient with low level underfloor which we weren't putting in. (Turns out all the floors have rotten joists so most have been replaced with solid slab so underfloor would have been an option after all... grrr). I didn't like the large boxes of the air source.
Better, we have two 300L tanks, which serve a 5,000 sq ft house with five bathrooms, and we never run out of hot water.
We have a combination of radiators and underfloor heating (about 1,000 square feet) and a very draughty house; the GSHP works well for us, but probably not as efficiently as it could.
Have you thought of an ideal payback time period?
Thanks charley so maybe one 300L IS enough for us?
Line i don't think payback periods ever really work - everything seems expensive, but it's more about long term planning and sustainability I think. eg PV panels are not currently suitable for our roof, but in the future they are bound to improve and they too could be added. (When the ones that look like slates are more efficient!)
Aha - thanks Charley. I shall pass on the message to the relatives.
Looks like the original company doing the work weren't as helpful as they should have been.
Better, it might be an idea to get a second opinion (from the manufacturer perhaps) as these things tend to be more expensive to rectify afterwards.
Hope it all gets sorted out Grendel.
I can't seem to get a straight answer! I have done 2 different online system designs - one by entering all details and the other was done by the woodburner supplier. I had to send him full details of the house, wall types, insulation, roof heights etc so he could work out heat requirements and then what size store accordingly. They recommened a 475L Excel and a 750L Acvatherm respectively. Completely different to what the plumber is suggesting.
Given that he originally mentioned a Megaflo (NOT the the same thing at all!) I am not inclined to beleive he knows what he is talking about. But I have gone round the bend reading plumbing forum boards to try to get an idea of what would be right.
Charley who worked out your system for you?
Better, the plumber came up with the design, although I believe he was receiving a lot of advice from the manufacturer's technical team. The manufacturer's engineers also came out a few times to oversee/ check the installation.
Does the manufacturer of the equipment have a list of installers? If so, it might be worth speaking to one of them.
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