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Ground Source Heat pumps


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A friend of mine has air source as his only form of heating, he lives near Andover.  It works fine all year round.

Surely as long as the refrigerant gas / liquid passes out of the house at a temperature a fair bit lower than ambient then it will extract heat from the air.

Bob.

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Following Ian casting doubt on the physics I did a few minutes research. Turns out Air Source Pumps will work down to -30°C, at that point the efficiency is reduced to a point where it is on a par with an electric fire.

George 

 

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As our dwelling has most of its rooms south-facing it needs no heating, even at night,  from late spring to early autumn, except the bathrooms. If I super-insulate the south facing wall the solar heating in that thick stone wall will be lost. Has anyone come across seasonally-adjustable wall insulation ?

Peter

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I can see all new housing and commercial premises having to have GSHP or ASHP, solar PV and battery storage from 2025 by law. The key is correctly designed and built buildings: Scandinavian or Canadian levels of insulation and air-tightness. From recent experiences of builders, no matter how good the design, the real test comes from the implementation.

Mick

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There is some interesting stuff on this thread. I looked at GSHP's a couple of years ago and was quoted £40k to install. Even with RHI payments I couldn't see how anyone could make economic sense of it particulary in a mid 19thC poorly insulated property using radiators. Anyone have any real-world examples of this actually working?

Jerry

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45 minutes ago, jerrytr5 said:

There is some interesting stuff on this thread. I looked at GSHP's a couple of years ago and was quoted £40k to install. Even with RHI payments I couldn't see how anyone could make economic sense of it particulary in a mid 19thC poorly insulated property using radiators. Anyone have any real-world examples of this actually working?

Jerry

Hi Jerry

I have installed a few also involved with Worcester on groundwork’s. Insulation is key or it’s pointless one factor most do not realise that the flow temperature to rads and under floor heating is lower and come a nice sunny but cold day you open the windows for fresh air and the heat is gone and it is more expensive to build the heat up again 

 

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Hi Neil, it's funny that installers generally say it only really functions efficiently on a well insulated new build with underfloor heating, and the suppliers tell you it works anywhere with anything.

Jerry

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57 minutes ago, jerrytr5 said:

Hi Neil, it's funny that installers generally say it only really functions efficiently on a well insulated new build with underfloor heating, and the suppliers tell you it works anywhere with anything.

Jerry

The installers know what works, mainly because we have seen the failures. I install a lot of ASHPs for swimming pools, the issues of over promising on performance from manufacturers are well known. It is essential to talk companies who really have a good track record and satisfied customers. In the early days of ASHP the manufacturers promises of operational gains at minus temperatures where only achievable in a laboratory, in the real world, when they frosted up and went into reverse cycle to defrost, they were removing more heat than they generated. Thankfully technology has moved on and performance is more credible, but you must ensure the specification is capable of delivering. A caveat with all heat pumps is to ensure they are specified for the conditions in which they are expected to operate. Many ‘failures of performance’ I have seen are from machines whose default internal programming and specification is for countries with much higher ambient temperatures.......cheap internet purchases that cause more problems than they are worth. 
Iain

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For some 40 years, my brother Peter has lived in a cottage (actually, originally 3 very small cottages) with solid stone walls, situated up a very narrow country lane in Gloucestershire - so narrow, the Citroen touches the bushes on both sides!  In the winter, for more than 30 years, he existed (I choose that word deliberately!) in the kitchen huddled next to the oil-fired Aga.

About 10 years ago, he started to do something about the situation and has managed a staggering improvement.  The walls and roof now have over 6” of insulation under cladding.  There are some (not a large number) of solar panels on the roof and an ASHP, which feeds underfloor heating.  In the living room, there is an old wood burner which he can use as a booster.  The Aga has been turned off.

Peter has never been so comfortable and, because of grants and clever electrickery, his overall fuel costs are amazingly low. 

In summer time, the cottage no longer becomes unbearably hot, so sleeping at night is not a problem.

Peter investigated open-loop GSHP, but decided that he could spend £5k on a test bore and end up with the answer that the inlet might well become blocked by the small particles of limestone carried in the underground stream.  Hence, the choice of ASHP.

We are delighted for him, especially as he has undertaken the planning, project management and a considerable amount of the work himself in conjunction with Phil, an excellent craftsman builder who has become a close friend over the years.  The standard of Phil’s workmanship, especially anything to do with carpentry, is a joy to behold.

Ian Cornish

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I bought my current house about 3 years ago, the core is 17th century with 1950s and 1970's extensions. Virtually no insulation and drafts everywhere.  It had a GSHP using 4x30m deep bore holes and a 2kW per phase, 3 phase compressor. Apparently it performed poorly and failed to heat the house, surprised? It also had a oil fired boiler as back-up. The GSHP was installed by the previous owner as he would not have gas in the house, following a gas explosion in his factory. After the man died, his widow had a gas boiler fitted and all was well with the world: a warm house.

I spent half a day with the original GSHP installer trying to get the thing working. We failed and he concluded that the compressor was kaput. No spares were available as the US based company had gone out of business year ago. I disconnected it from the central heating but left all the pipework in place "just in case". I also removed the oil fired boiler which the plumber cashed in.

Insulation and air-tightness are the key to a successful installation.

Mick

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40 minutes ago, Mick Forey said:

......

 

Insulation and air-tightness are the key to a successful installation.

Mick

One of many key considerations I would suggest.

Iain

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Heat pumps of any variety look complicated. Maybe there's a halfway house to be had: insulation, air-tightness and electric resistance heating. Plus a real fire for those blackouts. Then after a few winters the heating demands will be known. By then heat pumps more widely used and the expertise wider. Around here heat pumps seem to be "green tech" for a niche market, and priced accordingly. How do we judge a suppliers credentials ?

Peter

 

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I have extensive experience of both ground source heat pump and air source heat pump. Firstly the ground source heat pump where I worked in a commercial building was a Kensa- the building was built to all necessary insulation standards and the system worked- however there was a downside- underfloor heating- why anyone who designs these large buildings thinks that underfloor heating is effective has clearly never had to use the building- low temperature flow means that if a room is cold first thing in the morning it won't be warm until the next day- useless if the room is needed for a conference and the delegates are cold! The Kensa was destroyed after 5 years when oil inside the pump compressor tried to mix with water- shook the building when that went! £20k for a new pump which was out of warranty meant underfloor heating became gas boiler powered. Great when it works but the commercial rhi was so complicated to sort out that it never got done.

My home for past 6 years has been heated by a Mitsubishi Ecodan 8.5kwh air source heat pump. This system cost me including installation and a 250litre super insulated hot water tank £9k. I have received the rhi which is inflation linked for just over 6 years - 7 years is all the rhi runs to. My original standard gas boiler 27 years old had to be replaced due to none availability of parts so I looked into renewables hence buying air source. The system has been extremely reliable and I believe efficient. I would recommend this type of system but over the years I have discovered that my house was not as draught proof as I would have liked- no heating system will ever be efficient if you have a draughty house. One thing I wish I had bought with my system was solar panels- the system uses electricity for heating water as well as the heating so in the summer solar panels- or a solar thermal panel would provide virtually all hot water for free. If anyone wants to know more about air source ask me anything as an early adopter with a "correctly" installed system I'm happy to answer. My day job is a maintenance manager and I have no affiliation with any heat pump companies just a happy owner.

Just to add, my air source system had paid for itself within 5 years with the heating bill reduction and the rhi payments- so for any sceptics don't be this is proven technology which has been used in Europe for over 20 years- we are just soooo far behind in this country that's all.

Edited by michaeldavis39
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My understanding is that because of the thermal masses and relatively low temperatures involved, underfloor heating needs a long preheat time and is not responsive to rapid occupancy needs.  Often it’s on all of the time.   It also needs to be on a different control circuit to one that may have say radiators on it as they have such different responses. 
 

Paul

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11 minutes ago, PaulAnderson said:

My understanding is that because of the thermal masses and relatively low temperatures involved, underfloor heating needs a long preheat time and is not responsive to rapid occupancy needs

Absolutely Paul. I once lived in a flat which had underfloor electric heating. Unless there were long spells of settled weather it was pretty useless - always at least a day behind what was actually needed.   Either you were shivering waiting for it to heat up or the windows were wide open trying to cool things down.

Edited by RobH
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20 hours ago, michaeldavis39 said:

underfloor heating- why anyone who designs these large buildings thinks that underfloor heating is effective has clearly never had to use the building- low temperature flow means that if a room is cold first thing in the morning it won't be warm until the next day- useless if the room is needed for a conference and the delegates are cold!

Michael, this is for UFH in the slab, right? It's not surprising when you have to heat that enormous mass before any gets out into the room. These high mass systems along with loads of insulation must be a disaster for many people - it would be for us. As soon as the sun comes out in winter, sun streaming through the windows warms our house up and our (ultra reliable hot air) central heating goes off. And with so much insulation, what does heat do? It rises. Your bedrooms are upstairs and typically you would like them a few degrees cooler. Plainly insulation is important. But too much insulation, I think, makes a house uncomfortable.

As it happens, I am thinking of heat pump + UFH for our place. But a low mass system on top of the existing concrete floor, engineered for minimal thermal resistance from the heated layer to the floor surface. Such a system has a lower water temperature for better heat pump COP, requires less insulation underneath to give reasonable efficiency, and would be relatively responsive.

Thanks for your experience re: the Mitsubishi Ecodan.

Cheers, Richard

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Richard I think actually if you could get heater blowers connected to air source or radiators with fans it would be better than ufh. I really would not ever recommend ufh from 6 years experience of operating it in a very large building- it works best if never turned off but then how is that efficient? It isn't believe me and you also end up with people opening windows on the side of the building that has the sun streaming through it's just a total nightmare been there believe me! I have fitted radiator fans under my downstairs radiators to help circulate the heat better and it works brilliantly which is why I think that wall mounted fan heaters would be better - you know the ones that look like Aircon units? At my new workplace we have two of these units which heat and cool and they perform brilliantly - each are on opposite sides of the room which is quite a large space- there was three but one broke and we've found it isn't actually needed. 

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There are dry UFH systems, where the hoses are not embedded in the cement. 60-80 W/m2 capacity. 

Heat pumps that heat the (boiler-) water that warms the house require an “as low as possible” water temperature (preferably 30 degrees C or less) to be efficient. At these low temperatures normal radiators are not sufficient, and this is where UFH comes into the picture.

Before even considering a heat pump, improve insulation first. That’s what I’m doing at the moment.

A required water temperature test gives you a good indication if your house can be heated efficiently with a heat pump: Reduce the maximum watertemperature to 45- 50 degr. C and see if you can still heat your house with the current low temperatures. If not, your electricity costs will spike.

Cheers,

Waldi

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Speed of  response doesnt seem ot be feasible with underfloor heating. But with almost all our windows  facing south heating is often only needed in evenings. Im toying with insulation plus solar PV heating for hot  water and evening supply to radiators. Then in winter, radiant elec fire in just the rooms in use. Plus log/coal fire for the winter "blocking high" when the grid fails.  Not a lot to go wrong.

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20 hours ago, michaeldavis39 said:

I really would not ever recommend ufh from 6 years experience of operating it in a very large building- it works best if never turned off but then how is that efficient?

I'm always interested in the experience of others Michael. Did you ever come across UFH heating on top of an existing floor, with just a thin layer of insulation underneath? Probably a retro-fit in fact, which is what I'm considering. I've armed myself with design guides and regs, modelled our house - it all seems to work!

Cheers, Richard

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8 hours ago, Spit_2.5PI said:

I'm always interested in the experience of others Michael. Did you ever come across UFH heating on top of an existing floor, with just a thin layer of insulation underneath? Probably a retro-fit in fact, which is what I'm considering. I've armed myself with design guides and regs, modelled our house - it all seems to work!

Cheers, Richard

Hi Richard,

I’m considering that too, we call it a “dry system” . Part of the living room does not have UFH. My goal is to have a bit more capacity to reduce the water temperature. UFH is very comfortable by the way.

There are several systems available over here, some only 20 mm thick; with 10 mm flexible tubes. Whatever you decide, ensure the bottom of the floor is properly insulated. I applied 80 mm rhesol foam to the underside of my floor (in the basement), that was 10 years ago. I would increase that if I had to do it today.

Cheers,

Waldi

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Guys don't get me wrong ufh heating is nice to walk on- it was installed as a new build in the nursery at work- so all specifications had to be met especially regarding insulation- it's just very difficult to control. Yes temperature of the system water was low and in the coldest periods it would actually struggle unless it was left on every day all day. If you want the cheapest way to heat your home listen to this story. My friend has a modern  4 bedroom detached house with triple glazing, 4.5kwh solar panel system and a DEFRA approved log burning stove- I believe it's a 7.5kwh but have to check. Anyway his total annual gas and electric bill is £100 and he thinks that is expensive! He's going to half it this year he says and there's 3 adults living in the house. So key to a cheap to heat property is insulation and a wood burner so long as you don't mind lighting a fire every day in the winter- and the wood my friend gets is free from a joiner he knows.

Edited by michaeldavis39
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