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Mysterae

Ground Source Heat Pump

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Does anyone have any experience of Ground Source Heat Pump systems?

I'm currently researching GSHP systems as an alternative to heating the house we recently moved in to in the Highlands. At the moment there is an old oil fired boiler and a biomass boiler with a massive accumulator tank fitted:

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The old oil fired boiler (small green thing with the hose on the left of the image) could do with replacing but heating oil is so expensive (approx 49p per litre) and going by our current consumption I estimate that we'll consume around £3,000 in oil a year 😮. The biomass boiler, a fancy name for a wood burner (the red/black contraption in the middle) is much cheaper to run but takes quite the bit of effort to keep going in the winter - it eats logs for breakfast, lunch and dinner! I reckon we'll consume around 20 tonne of wood a year (around £1,500 worth without cutting our own) and although wood burning is sustainable and is seen as a form of renewable energy, it's stinking, dirty and high in maintenance, and we'd need the oil boiler as a backup if we were ever to go away for more than a few days in winter.

A Ground Source Heat Pump system seems like the ideal replacement if you've got the land to lay the ground source pipework. It's low maintenance, environmentally friendly and highly efficient - depending on the efficiency of the system, for every kWh of energy you put in, you get up to four times the kWh of energy out. Yes, you read that right - more energy than you put in, effectively cutting energy costs down by three quarters.

The catch? It's stupid expensive to install, requires land and significant ground works (unless you want a 150 - 200 metre bore hole drilled which is even more expensive). From what I've read, the system I'd need could cost somewhere north of £20,000....

The good news is that with Ofgem's Domestic Renewable Heat Incentive, they'll pay me back up to £28,000 over seven years:

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It's a no-brainer. A few months ago I thought my first big project was building a new garage, but no, it's going to be a GSHP system. Perhaps I can route some of that pipework to underfloor heating in the new garage too 😉.

So, as my original question, does anybody have any experience with Ground Source Heat Pump systems? Are they really that great?


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Whilst my property is a rented converted barn we have a GSHP. All I can say is, it’s fantastic. It’s a 4 bed barn, underfloor heating with 10 zones! 
Also have a heat recovery vent system. House is a constant 20deg c. Energy supplier is Bulb, so all renewables. £65.00 per month. Having said that I understand the bores are expensive to sink. I have 2, flow and return, 100m deep. About £15k.


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 My biomass absolutely gobbles up the wood. Is a pain in the ass to keep clean, needs constant maintenance and ongoing de-ashing. That said - the payments are very nice indeed.

im liking the look of the gshp options a lot - I’ll watch this eagerly


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Think you still need an immersion to boost the temperature for bathing. Water is not hot enough for radiators so underfloor heating everywhere.


hindsight: the science that is never wrong

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@DDubya Encouraging words Danny! £65 a month sounds fantastic, to put it in to context we burned through 1,800 (£900) litres of heating oil in just under 3 months. Yikes! Now there's a few reasons for this - it's a big house, un-insulated at the moment (the loft and cavity wall insulation are being done early next year) and we treated the system like our previous house that was smaller, gas heated and very well insulated. Plus it was winter and we just weren't familiar to using the system. I've since installed a 2-zone Hive heating controller which has much better control but being realistic it's not going to drop our usage massively. 

You mention underfloor heating and that is what they recommend with GSHP systems. In traditional radiator systems the water circulated round the radiators is around 70 degrees C, whereas in underfloor heating it only has to be 40 to 50 degrees C. You can use radiators with GSHP systems but you have to increase the size of the radiators by around 20%, either by new or additional radiators, not exactly ideal. So I'm looking at the idea of retrofitting underfloor heating to our concrete floors or fitting bigger radiators. Both options increase the cost of the job but I'd much prefer the underfloor heating, and the level of control (get you with your 10 zones!).

Was that £15k for just the boreholes? I've seen some mental prices for borehole digging. I'm not considering the borehole option, purely the horizontal array because it's cheaper and also while the digger is doing it's work I'll add in some french drains to dry out the bit land so it's not the quagmire it currently is 😉 .

@Barrykearley Yes, biomass boilers really do burn it quick. Plus you have the storage and drying of the wood and the handling of it all. Open the furnace door to top it up and breathe a 20 pack worth of smoke! It was quite romantic at first, look as us being all renewable and one with nature, but once you've wheelbarrow'ed your tenth load through it's just a pain. I'm also fed up of smelling burnt every time I come from the garage! I thought about a wood pellet hopper type biomass boiler as a replacement but ideally I want to remove both the oil and wood boilers. The current system isn't eligible for the DRHI as it was installed by the previous owner many years ago.

At the moment I'm still at the feasibility stage but watch this space. After the new year I'll contact a few MCS installers (Microgeneration Certificate Scheme) and go from there. Another thing worth mentioning is that you don't even have to pay for it - by utilising Assignment of Rights (AoR). Assignment of Rights is essentially when a nominated party pays for the installation of the GSHP (so you get it for free) and in return they receive all of the DRHI payments. Sounds great, but if your system costs £20k to install and the DRHI payment is £28k, you've lost out on a potential £8,000. A nice investment for them!


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@pete That was certainly the case a few years ago but modern systems are said to be able to cope with the hot water side of things. Some systems do have an immersion type heater integrated for the hot water side (boosting it kinda thing), or you can fit solar thermal panels exclusively for the hot water tank, which is DRHI eligible too.


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Be really, and I mean really, careful with any system which has a booster heating element.

many of those systems were ditched from the MCS list years ago when the whole lot was suspended during times when manufacturers were lying. If you use the “backup” heater - your bills will go interstellar.

low output rads are absolutely crap imho - spend the dosh and go for an overlay system. Hot water should be done separately with a megaflow or similar and utilise an immersion for the top up between 40-65deg

 


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@Barrykearley For sure Barry! In my research I came across a BBC documentary about a housing association estate where most of the houses were built with recovered air sourced heating from NIBE. Poorly specified, poorly utilised and understood, it was meant to provide the tennants with cheap heating but ended up costing them thousands. The electrical element of the boiler was practically running 24/7. Quite the sad story.


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The only thing I would add as a Refrigeration eng is be very mind full of the refrigerant that is used as the industry is changing fast and R404a as of Jan 1st will not be allowed to be used in its virgin form unless the system operates at -50 or contains less than 10kg even so it will be hugely expensive per Kg 

I've lost count the amount of customers who were sold R22r  r stands for reclaimed or R422D for their  original R22 systems at huge cost only to be told oh now you can't use it anyway and will be charged again per Kg to have it incinerated it's a propper minefield at the moment and before anybody tells you well you can always have it retro fitted for a newer refrigerant later 

Remember we have had customers loose as much as 20% capacity with a different refrigerant 

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At the moment there are heat pumps being commissioned that use hot air from the London underground via an industrial Ammonia system to supply heating for housing estates how successful these will be only time will tell 

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We were a relatively early adopter so things will have changed.  There are some great things about a GSHP set up but its certainly worth thinking about very seriously first. 

The financial argument, in our experience, doesn't stack up so if your looking at it purely as a way of saving money my expectation is that you will be disappointed and spend more than you save.

Our costs:  We have a relatively large house, but not exceptional at about 360 sqm.  To provide enough heat for that we were marginal on being able to generate enough heat from the largest GSHP available in 2012 on a single phase supply.  We looked at 3 phase but got a prohibitive quote of well over £10k from Western Power - and that was just for the transformer and didn't cover the 100m dig for new cabling to our house or anything else that we'd have needed to connect up our domestic system.  So we decided to stick to Single phase.  As I said the most powerful pump was marginal so our preferred supplier actually replaced the critical pump  for the brine circuit with a bigger external one.  The initial quote for "everything" was £21k.  Everything turned out to exclude almost everything except the GSHP.  We were advised to site the pump in an outbuilding instead of the house - we're really glad we did because the noise of the pumps all going in unison is disturbingly loud - but the added cost of the 22m of Rehau pipe was over £2k just for the pipe to bridge the run from plant room to the house.   Its a complex electrical setup to power and control all of the elements - electrical works were £2k and they were so poorly done I redid them myself later with better quality components.  The groundworks were £7k to dig the 8x50m long channels 1mx1m and the link back up to an underground manifold housing (think a blockwork box with concrete slab on top) for another £1200 and the 100m run back up to the house.  And then another £500 to get a local farmer in to re-level and reseed to the lower field to put it back to grass - which took about 2 years, but now you'd never know what lies beneath!  So we're over £30k in and we've got some mildly warm water coming into the house.  For various reasons our refurb got out of hand and we eventually needed to rip up and relay the basic slabs that form our ground floor.  (Had we known that at the start obviously we'd have knocked the thing down and started again...but we didn't and that's another story.)  But relaying the slabs was great for sorting the underfloor heating.  I did all of the work on top of the new slab myself so there are no labour charges.  First an eleven layer foil insulation (Triso Sol) £2k; then your choice of pipe base and pipes - ours is a pipe in foam system by Wavin £6k; then you need some pretty substantial plumbing elements like manifolds, circulation pumps, electrical works for zone controls and pumps all well over £3k; then a screed layer £2.7k - So overall about £14k to get heat around the house downstairs.  Upstairs we'd decided on rads.  As Barry suggests low heat through rads can be crap, but with the correct aluminium rads then 45 degree flow water is absolutely fine to keep upstairs a toasty 21 degrees - trouble is they cost lots more than std steel stuff so the radiator bill was £6k plus all the bits for fitting.  So overall our installation cost for the heating system was £56838:68 - and remember that didn't include any labour for any of the elements in the house itself.  Against that we are receiving through the RHI scheme around £3300/annum for 7 years or a total of about £24k.  Since it would have cost no more than £15k to replace the old Calor Gas/Radiator system that the original house had, we quadrupled the budget and even with the RHI paid up will be over £20k worse off financially than we'd would have been. 

To run the thing efficiently you need to know what your heat pump can manage on its own.  Ours comes in at about 47 degree water on full chat so off the back of that we run the floor system and rads and domestic hot water at 45 degrees.  Sounds odd to those with a more typical 65 degree water flow but its actually plenty hot enough for nearly everything.  We have a 400l HW tank and its fine for everyone even when we have a houseful.  The joy of that is that we only run the Immersions once a week for the anti-legionairs cycle - which is really just getting the HW up to 65 degrees for two hours - which we choose to do overnight Fridays.  Nevertheless our leccy bill is considerable - about £3k year.  On the other hand we have no other domestic fuel costs...

I'd say the greatest benefit is the underfloor heating element.  The rooms are very even comfortable temperature wise with no hot/cold spots - each has its own zone control to keep it at 21 degrees.  In 2007 we rented a barn with underfloor heating of a gas boiler and found that uncomfortable as the flow temp was too high.  GSHP is the perfect heat source for underfloor heating.  The rads are less successful. they work well enough in themselves, but I only put in one zone for all of the bedrooms and I've found it impossible to get the balancing right.  If I did it again I'd do each room on its own zone.  The system runs all year and costs very little over the summer.  I service it in May - takes an hour or so.   Very few companies out there know much about these systems so you may end up needing to be your own expert if things go a bit awry - so not for the faint hearted!

In conclusion: I'd certainly have a GSHP based system again as its great to use and benefit from, but its stupidly expensive to install if you do it properly to optimise the inbuilt characteristics so its a definite "upgrade" choice not a bargain! 

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Loving Lionel and Eleanor......missing Charlie and Sonny

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45 minutes ago, Mysterae said:

@Barrykearley For sure Barry! In my research I came across a BBC documentary about a housing association estate where most of the houses were built with recovered air sourced heating from NIBE. Poorly specified, poorly utilised and understood, it was meant to provide the tennants with cheap heating but ended up costing them thousands. The electrical element of the boiler was practically running 24/7. Quite the sad story.

Yep was that in East London by any chance? We wired that lot in it was a complete and utter disaster, we didn’t specify it and only done the electrical, but the running costs were ridiculous. I had the Evening Standard on my door and I said .go talk to the plumbing company we gave them two outlets and had nothing to do with the system. 

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Massively common in Wales. British Gas were paid vast sums to upgrade social housing by the welsh assembly and made a complete mess of it all.

they made a fortune on every house they fitted up 👍


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Two things. What about air sourced systems? And, boy, you guys like your houses hot. I'm sorry but 20c plus really is ridiculous!  Why do you need to waste energy heating your house so high?

For the best nights sleep you need to be looking around 15-17c in the bedroom, 20+ is too high as your body naturally wants to cool during sleep.

Stick the heating at 18c and wear a jumper. It's not about being tight, I just find it mental that people talk about green heating sources and then use more heat than is actually needed.

27m houses in the UK all heated to between 3 and 10 (yes, some people I work with have their central heating at 27/28c - ffs I kid you not!) and guess what, we are warming the environment.

I regularly go into London hotels were the room is preset on the thermostat to 23-25c. 

Anyway, rant over. What about air sourced? 😂🤣


Alcohol. Sex. Tobacco. Drugs. Chocolate.  Meh! NOTHING in this world is as addictive as an Evora +0. It's not for babies!        

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Air sourced is ok untill the ambient drops below 0'C then the system has to be sized correctly and the gains become harder to achieve and that's when obviously you need it and also they eventually ice up and require a defrost period either electrically or reverse cycle again interrupting the supply of heating and at further cost.

So ok for an office or work environment only used during the day but for continuous use at home the ground is a fare better and more importantly consistent source of heat.

 

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18 minutes ago, C8RKH said:

 I'm sorry but 20c plus really is ridiculous!  Why do you need to waste energy heating your house so high?

For the best nights sleep you need to be looking around 15-17c in the bedroom, 20+ is too high as your body naturally wants to cool during sleep.

Stick the heating at 18c and wear a jumper. It's not about being tight, I just find it mental that people talk about green heating sources and then use more heat than is actually needed.

Yet another thing where we're all different Andy.   We tried 18 for a year.  It was OK but a bit too cool for any just sitting activity and visitors felt cold.  We upped it through 19 to 20 and finally settled on 21 three years ago.  At 21 it is kept very evenly between 20 and 21.  It suits my daily uniform of joggers and t-shirt - it'd be too hot in a jumper.  Fran feels the cold much more but is comfortable in "normal" clothing (which means more layers than me!).  Like many old men I need to get up in the night and its lovely to be able to pad about without freezing my gonads off, I don't own any PJs .  We use a summer weight duvet all year and our bodies have no trouble sleeping - its perfect for us.  With a GSHP/Underfloor system a downside (or upside - depending how you look at it) is that its far less controllable than a gas fired radiator system.  If you want to change by a few degrees then you need to allow several hours.  If you try to go from cold/off to normal room temperature then its more like 2 days so its not really suitable to try to control like a normal system which may run for a few hours in the morning and evening and basically get cold during the day and overnight.  Since we're always here it suits our life but may seem more wasteful if the property is often unoccupied.    Others may find cooler would work for them most of the time and maybe a wood burner in the lounge in the evening.  We didn't do it to be green or save money - it just seemed like the best system available to me when I did the research, and we run it to make our lives as comfy as poss.  

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Loving Lionel and Eleanor......missing Charlie and Sonny

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As an aside, if you're looking at underfloor heating, a friend of a very good friend owns https://www.thermosphere.com/ and I'm sure I could get some decent discounts for TLFers 👍

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Hmmmm! I'd expect electric underfloor heating to be THE most expensive type of heating to run bar none.  It obviously has its place - a new room/extension beyond the scope of the current heating, or bathroom refurbs or similar, but not as a generic throughout the house solution.  JIMO...


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2 hours ago, MPx said:

Hmmmm! I'd expect electric underfloor heating to be THE most expensive type of heating to run bar none.  It obviously has its place - a new room/extension beyond the scope of the current heating, or bathroom refurbs or similar, but not as a generic throughout the house solution.  JIMO...

Not necessarily or is this based on experience? For instance, Electric UFH using a tiled floor surface would, I suspect, be cheaper than using an oil fired boiler and wall mounted radiators. Not everyone has access to a mains gas connection so your option is either delivered LPG or oil.  We have oil currently and believe me, it's expensive...

However, I'm looking at retrofitting either electric UFH (via mats) or using something like the Nu-Heat Lo Pro system to connect water UFH to my existing oil fired boiler.  My current boiler has plenty of spare capacity to run the UFH so this would be the most cost effective installation as it would take about 20 years to pay back a full new system install, if not much longer, in savings over my current setup. I live on the side of a hill, so although I have a garden of 0.5 acres it is not ideal for a ground source installation. However, if I ever do get flooded then the world has more pressing issues to deal with lol....


Alcohol. Sex. Tobacco. Drugs. Chocolate.  Meh! NOTHING in this world is as addictive as an Evora +0. It's not for babies!        

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No personal experience, just two anecdotal.  Some friends put it in their conservatory but then considered it too expensive to run to use, so just let the conservatory get unusably cold.   Other friends had it in a new en-suite and went on about how expensive it was to run...but I don't know if either of those was real in absolute terms or just different value judgments to what I would have made.  I did a fair bit of research in 2012 and at that time gas was cheapest, then coal, then oil/calor, then wood, and elec was top of the tree at about 4 times the cost of gas for the same heat.

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Loving Lionel and Eleanor......missing Charlie and Sonny

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 Been all electric for 40 years don't think 1500 pounds a year a in is expensive. Modern electric boilers are very efficient


hindsight: the science that is never wrong

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I select and sell this sort of equipment for a living (albeit for commercial / industrial and large residential rather than domestic). If I were in your shoes I wouldn’t want to commit to the initial costs for GSHP. I’d be more inclined to go with a (correctly sized!) ASHP. The SCOP is not quite as high but the costs are way lower and it’s a simpler solution with less to go wrong. 
As a few people have mentioned above the efficiency does drop off significantly below 0 deg C. Sometimes we select a gas boiler which can take over when the ambient temp is low. This is a nice solution as you can size the ASHP on a higher ambient temperature to keep the cost down. 
In your case you have an existing oil and biomas system so you could engineer a change over between the existing system and the new ASHP to optimise efficiency based on Ambient temp and demand.

drop me a PM if you need any more help / advice 

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On 27/12/2019 at 21:39, Mysterae said:

it's a big house, un-insulated at the moment

We looked into a GSHP a few years ago but didn’t end up going for it for a few reasons - primarily, we moved out before we would have received the full 7 years of payments. 

GSHPs really work if A) you’ve got enough land to lay the pipes (bore holes are prohibitively expensive). Also be aware if you plan to lay the pipes under a garden, you will be taking heat out of the ground which the plants would otherwise want to use. 

B) Your electricity bills will be very high (to run the main unit). If you have an alternate method of generating electricity (panels or turbine), then you can nearly get ‘off grid’ with your energy generation.

C) The RHI payments are dependent upon a successful ‘Green Deal Assessment’. Essentially, a GSHP only works within a very well insulated building. This is relatively easy in a new build or a modern (barn) conversion but much, much harder in an old house. You might find that you might never be able to insulate your current property enough to benefit from RHI payments. Which will make a GSHP a very expensive proposition.

 

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This has been a popular subject, so glad I posted this! So much knowledge and experience, I thank you all for your insights.

@MPx Many thanks for sharing your personal experience, it's precisely the kind of scenario that I'd want to avoid, that's a huge cost and would break me! This is about saving money on the energy we use to heat our home and to get away from the burning of logs, making a cleaner home. You've certainly opened my eyes to the possibility of it getting out of hand. Our house is smaller than yours (290sqm) with a combined heating and hot water demand of under 40,000 kWh per year, before insulation improvements. The already assessed and planned loft and cavity wall insulation will bring that down to around 33,000 kWh per year (still 3,000 kWh above the current DRHI cap).  I'm not sure how those numbers stack with a single phase GSHP system; like you I'm unlikely to put in a 3 phase supply.

You still sound positive about it though, but would you do it again if you knew the final cost!

@Dan E Not sure, search for NIBE on Rip Off Britain on youtube. They ended up ripping out the systems and fitting normal gas boilers in a lot of the homes.

@62dave It's an interesting ideal to compliment the existing setup with an ASHP system. In our current system, when the biomass boiler is running this takes priority over the oil boiler, and when the biomass can no longer provide enough heat it automatically changes over to the oil boiler. Putting another heat source in to the circuit sounds plausible, I would need to work out if an ASHP would work all that well - it has dropped below 0c more than a few times this winter and I suspect it's not yet over!

@Bravo73 We have the land space for the pipework and is just soggy grass at the moment - I was planning on digging it up anyway and laying a few french drains. There's roof space for solar panels, either for electricity or thermal gains. I used to run a few crypto miners so I know what high electricity bills are like! As I mentioned before the house is scheduled for insulation but what irks is you won't know what RHI payments you qualify until you've done the installation, could be much lower than hoped for.

All these responses have certainly opened my eyes and made me more cynical to all the hype. I've got a lot of research still to do. What a minefield!


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Look up Greener Living Ltd


hindsight: the science that is never wrong

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