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DIY well geothermal water to water heat pump feasibility?

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Bigruss
Bigruss Member Posts: 1

looking for someone to review and advise .

Have 11’ deep well ( 3’dia x 7’ constant water level ) next to house.

How many feet of 3/4” pipe would I need to install to “Heat - Only” 2000 sf one level home.

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  • Jon_blaney
    Jon_blaney Member Posts: 322
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    A system using a loop in a well will not work. There is inadequate heat exchange between the water and the surrounding earth. You would need to pump the water from the well, extract the heat, and return to some place else.

    Heat loss drives equipment sizing. Equipment size drives gal/min required. Water flow drives piping. Does your well have an adequate flow rate?

  • DCContrarian
    DCContrarian Member Posts: 305
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    Before beginning I would check to see if this is even legal where you are. A lot of places a fussy about what you do with groundwater.

    ethicalpaul
  • DCContrarian
    DCContrarian Member Posts: 305
    edited July 9
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    This article tells how to calculate your house's heating load based on historical energy usage:

    https://www.greenbuildingadvisor.com/article/replacing-a-furnace-or-boiler

    Let's say your well is at 50F in the winter and you can return water at 35F without having to worry about freezing. Let's say your house needs 50,000 BTU/hr. The formula for BTU/hr for water is (temperature change)*(gallons per minute)*500. With a 15F temperature change, and 50,000 BTU/hr, you'd need 6.7 gallons per minute.

    Your well is 3' in diameter and 7' deep, so that's 49 cubic feet or about 500 gallons. At 6.7 gallons per minute it would take about an hour to cycle through all of the water in the well. Given that it's pretty small it probably won't have a lot of exchange with the surrounding water so it would get cold and stay cold and your heat pump would shut down.

    What we don't know is whether your well can sustain extracting 6.7 GPM all winter long without losing water level. If it can, you could extract water and dump the chilled water elsewhere. You'd have to have a place to put quite a bit of water. It also would take a fair bit of electricity to pump out that much water.

  • Jamie Hall
    Jamie Hall Member Posts: 23,655
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    Not much to add to all that. First point: will your well actually yield 7 gpm or better, pumped steadily 24 hours per day, 7 days per week? I honestly doubt it, but I haven't seen the well — obviously — and I don't know what kind of material it is constructed in (coarse sand next to a lake or river? Might manage quite well. Upland silty material? No hope).

    Second, under those flow conditions, what does the water temperature stabilise at?

    Third, as has been noted, where and how are you going to discharge the now cold water Groundwater recharge is strictly regulated in many areas, and surface water discharge even more so.

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • jumper
    jumper Member Posts: 2,333
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    Trick is to discharge water so that it picks up heat from earth and gets back into well. Geothermal engineering?

    Decades ago, when refrigerant was cheap, some guy buried lots of copper tubing in his yard to directly extract heat from earth. Story is that it took more than one winter to turn yard into solid ice.

  • Jamie Hall
    Jamie Hall Member Posts: 23,655
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    The most reliable — and least subject to regulatory concerns — is not to use the groundwater directly, but to drill one or more deep wells (or a large horizontal grid, preferably well below frost level) and circulate water or some other liquid through them in closed pipes. They will pick up heat from — or release heat to — the ground. The deep well versions, if you are well below the water table in the area, will actually be transferring the heat from or to the groundwater going by, and if you get the numbers right the temperature of your circulating water returning from the well will be very nearly constant.

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    ethicalpaulIntplm.
  • ethicalpaul
    ethicalpaul Member Posts: 5,795
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    Well said @Jamie Hall

    I hit water at 20 feet in my 550 foot well and I'm quite sure that's exactly what I was seeing. Incoming loop temp would slowly fall throughout the heating season but I never did actually need the food-safe antifreeze that I had added to it.

    NJ Steam Homeowner.
    Free NJ and remote steam advice: https://heatinghelp.com/find-a-contractor/detail/new-jersey-steam-help/
    See my sight glass boiler videos: https://bit.ly/3sZW1el

  • DCContrarian
    DCContrarian Member Posts: 305
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    How many BTUs are you pulling out of the well? I've heard 500 feet per ton bandied about as a rule of thumb, curious how that compares with your experience.

  • ethicalpaul
    ethicalpaul Member Posts: 5,795
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    I had a three ton unit on it. My engineer did a heat loss on the house. He sized the well for that size heat pump. It never had trouble heating and for cooling it was amazing

    NJ Steam Homeowner.
    Free NJ and remote steam advice: https://heatinghelp.com/find-a-contractor/detail/new-jersey-steam-help/
    See my sight glass boiler videos: https://bit.ly/3sZW1el

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,840
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    I am not much for heat pumps except for Geothermal. They work well. First ones I installed was back in the 90s. We had 5 or 6 WaterFurnace heat pumps in an animal hospital and they worked great. I think they were 3 ton units. Closed loop in the ground is the way to go

    Expensive to install though

    ethicalpaul
  • ethicalpaul
    ethicalpaul Member Posts: 5,795
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    Upfront cost is high, but operation cost is nice and there is like 0 maintenance for 20 years (if you're luckyish).

    But for the OP I would say that existing well isn't going to cut it.

    NJ Steam Homeowner.
    Free NJ and remote steam advice: https://heatinghelp.com/find-a-contractor/detail/new-jersey-steam-help/
    See my sight glass boiler videos: https://bit.ly/3sZW1el

  • hot_rod
    hot_rod Member Posts: 22,483
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    years ago I went to a training and demo of a geo application with a directional boring rig

    If you have the land area this may be an option to bore holes or trench loops


    https://geosmartenergy.com/consider-horizontal-boring/

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Intplm.
    Intplm. Member Posts: 2,084
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    Those geothermal pits can get quite large.

    If I had the land, I would do it.

  • Jamie Hall
    Jamie Hall Member Posts: 23,655
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    One can, I think, sort of make an estimate of so and so many feet of pipe per ton, but it's going to be a ballpark. If all of your heat transfer is conduction through the pipe walls into or out of the soil, or rock, that's one thing — but if your heat transfer is convection to moving ground water as it might be in fractured rock or certainly in sands and gravels, you can get much higher capacity.

    You'd really need a hydrogeologist (a rather exotic breed of cat) or a very experienced well driller to help with that.

    For horizontal grid systems this isn't a factor, of course.

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • leonz
    leonz Member Posts: 1,187
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    The general rule is 100 feet of drilled bore hole for every ton of heating or cooling needed.

    The so called geothermally enhanced grout is a clay based grout and a net insulator. Using mason sand in a bore hole for a closed loop system would make a better less costly heat exchange method

    Your hand dug well is not deep enough to do any useful amount heat exchange for heating or cooling.

  • Jamie Hall
    Jamie Hall Member Posts: 23,655
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    Excellent point on the grout. It goes with my comment just above: if the system is depending on conductive heat transfer to dry or most ground, or to rock, without significant groundwater movement, then you really do need the "geothermally enhanced" grout, as you are dependent on conductance for the heat transfer. True, the stuff is not a very good conductor, but it does ensure large total effective heat transfer area. On the other hand, if you are depending on groundwater movement, you want a medium to coarse sand pack around the pipes — and no grout (and you'll be better off with a cable tool drill — or very careful development of the well, like a water supply well, if using a rotary or reverse rotary rig).

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • ethicalpaul
    ethicalpaul Member Posts: 5,795
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    I have never personally measured the thermal conductivity of the grout, but the entire "Geothermal" energy industry, its drillers, and its engineers seem to be in concert against you.

    https://www.thedriller.com/articles/87744-an-overview-of-geothermal-grouts

    As someone who disagrees with several residential steam boiler modes of thought, I am sympathetic. But if sand works best, why don't they use it?

    NJ Steam Homeowner.
    Free NJ and remote steam advice: https://heatinghelp.com/find-a-contractor/detail/new-jersey-steam-help/
    See my sight glass boiler videos: https://bit.ly/3sZW1el

    hot_rod
  • DCContrarian
    DCContrarian Member Posts: 305
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    The primary purpose of the grout is to keep surface water from contaminating the groundwater. It's high conductivity only compared to what is normally used for that purpose.

  • Jamie Hall
    Jamie Hall Member Posts: 23,655
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    Details details. Quite correct. I just sort of assumed that the well would be drilled and completed properly. That is, drill oversize at least 10 feet into bedrock, if a rock well, or to a depth of at least 20 feet below the surface in unconsolidated materials. Lower casing in to that depth (never pound casing) and cement grout from the bottom up to the surface. Then drill through that to finish size as far down as needed…

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    PC7060
  • ethicalpaul
    ethicalpaul Member Posts: 5,795
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    So the reason they don't use sand is because that would allow surface (or near surface) water to flow into the well. It sounds like the grout is probably mandated by regulation then, no?

    NJ Steam Homeowner.
    Free NJ and remote steam advice: https://heatinghelp.com/find-a-contractor/detail/new-jersey-steam-help/
    See my sight glass boiler videos: https://bit.ly/3sZW1el

  • leonz
    leonz Member Posts: 1,187
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    No, Baroid has convinced them thier grout is the be all, end all for geothermal.

    ethicalpaul
  • leonz
    leonz Member Posts: 1,187
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    The geothermal grout and closed loop systems are just another way to empty your wallet. if a 20 well closed loop system fails they may never find the leak.

  • ethicalpaul
    ethicalpaul Member Posts: 5,795
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    My house had one well and that tube was extremely solid. if it did leak, I wouldn't have to look very far, but honestly that tube is going to outlive all of us and our children

    NJ Steam Homeowner.
    Free NJ and remote steam advice: https://heatinghelp.com/find-a-contractor/detail/new-jersey-steam-help/
    See my sight glass boiler videos: https://bit.ly/3sZW1el

  • Jamie Hall
    Jamie Hall Member Posts: 23,655
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    In some jurisdictions it is. In others, no. Unfortunately. However, it is generally regarded in the industry as good practice.

    It is important to remember that what flows into a well in the way of near surface water — or other contaminants — will not stay in the well. It will migrate with the groundwater. Speaking from considerable experience, it can be devilishly hard to track down the source of such contamination, although it can usually be done (I once tracked a contamination plume back about a mile to an improperly built well…)

    And guess who gets to pay the cost of the tracking down and the remediation? Right. The property owner. And we are talking low six figures in many cases.

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    ethicalpaul
  • Teemok
    Teemok Member, Email Confirmation Posts: 570
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    I had the Idea of pulling water up from one side of my 150' lot and reintroducing it on the other side. I live on an alluvial plain. 15' of silty soil down to 3-6' of 3/8-3/4 gravel that sits on a 20' clay layer. the first water table flows down following the natural slope of the clay in the gravel above it. It would be a 150ft diversion with a slight temperature change. I researched how to properly reintroduce the water back into the water table. Regulations made me think the better of it but I do think it would work……well

  • ethicalpaul
    ethicalpaul Member Posts: 5,795
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    Pump and dump (open) systems like that can be hard on the heat pump depending on the water quality, I understand.

    NJ Steam Homeowner.
    Free NJ and remote steam advice: https://heatinghelp.com/find-a-contractor/detail/new-jersey-steam-help/
    See my sight glass boiler videos: https://bit.ly/3sZW1el

    Teemok
  • Jamie Hall
    Jamie Hall Member Posts: 23,655
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    Usually that does work quite well — but you do have to be very sure of the regulatory environment — which can be squirrely. The other thing to make sure of is that the water quality you are pumping back in is at least as good as what you have pumped out — and be able to prove it.

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Teemok
  • Teemok
    Teemok Member, Email Confirmation Posts: 570
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    From evap. tests it doesn't seem to be loaded with much. I think heat exchanger type and maintenance would be key. I was concerned pulling that much out of the gravel it might eventually clog up. It will never happen. It was just a young man's musings.

  • hot_rod
    hot_rod Member Posts: 22,483
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    I would look to IGSHPA for actual facts and data on what works, how and why.

    https://igshpa.org

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream