Deepening well to install geothermal system

Discussion in 'Solar and Geothermal Water Heating Forum' started by Twotone, Sep 7, 2018.

  1. Twotone

    Twotone New Member

    Joined:
    Sep 6, 2018
    Location:
    East Central Ohio
    I’m a newbie here on the forum looking for advice. Not a newbie from DIY. From well log, my well is 238 feet deep. Water was hit at 120-140 ft. The casing was installed to the bottom of the well. The casing was perforated at 140 ft. The 10 gpm pump was set at 230 ft. The well log indicates the well was developed to supply 3 gpm. The pump discharges into a large hold tank (~500 gal) with a float switch. The house is supplied with a small centrifugal booster pump with a medium size bladder tank with pressure switch.

    I am looking to install a single heat pump geothermal system that requires a minimum of 6 gpm. The system indicates a 6-8 gpm range is preferred. I am looking to install a heat pump with superheater on it to make efficient hot water.

    I have a verbal quote from driller indicating that to produce 8 gpm the well would need to be deepened to about 470 feet deep. This is consistent with other well logs in my area. A 1 ½ to 2 HP submersible pump would need to be installed. to pump the 8 gpm. The wiring would need to be upgraded from 12 gauge to 10 or 8 gauge.

    I’m looking for the most efficient way to supply the house, barn, and geothermal unit.

    Researching the forums, I like the idea of reusing the water off the geothermal to supply the house and barn and possibly adding either a sprinkler or pasture irrigation system and dumping the non-reused to drain tile into the field. Any thoughts on collecting water in 500 gallons hold tank for future use?

    I see the (4) heat pump system with the house booster pump diagram. Is there a diagram for what I am trying to accomplish? Which CSV valves are recommended? Any additional advice or questions for the driller quotes would be appreciated.

    I live in a hard water area and plan to install a water softener on the house water supply.

    If additional information is needed please request.
     
  2. Twotone

    Twotone New Member

    Joined:
    Sep 6, 2018
    Location:
    East Central Ohio
    I looked at well logs near my address. The worst case well had a static water level of 280' and draw down of 80'. There is not a vertical rise from the well to the house. The heat pump would be located about 100 ft from well. Using 1" pipe it looks like a TDH of ~400'. My current thoughts would be to use 10 gpm well pump to pump through the heat pump coils and then refill fill the hold tank and use the existing booster pump to supply the house and barn. When the hold tank is full dump the rest to field tile. The 10S grundfos curve looks like the 1 1/2 hp is conservative.
     
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  4. valveman

    valveman Cary Austin Staff Member

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    Mar 15, 2006
    Occupation:
    Pump Controls Technician
    Location:
    Lubbock, Texas
    To supply an open loop heat pump from such a deep well will use a lot of energy. It will take a 1.5HP to deliver 8 GPM from 470', and a 2HP to deliver 8 GPM at house pressure, but it will work. I would install the 1.5HP and run water directly through the heat pump and discharge into the storage tank. If the storage tank gets full, just let it overflow to the tile irrigation. Then use a booster pump with a CSV, small pressure tank, and a pressure switch to supply the house and yard as needed.

    A well test might be worth the expense, so you can see exactly what depth the 8 GPM is coming from. If the pumping level is higher than 470' you might be able to use a 1HP instead of the 1.5 HP well pump. The smaller the well pump the more efficient and less energy will be used for the heat pump.
     
  5. Twotone

    Twotone New Member

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    Sep 6, 2018
    Location:
    East Central Ohio
    upload_2018-9-12_15-29-34.png
    Here is a scale drawing. Looks like my best option is to go with pressure sustain valve. Locate the pressure sustain valve just inside the wall before exiting the walk out basement wall? And PK1A on booster pump?

    The overflow idea was a great! I looked at relocating the storage tank and booster pump but the wire and re-piping cost offset the piping cost savings.

    The booster pump has a 44 gal Well Rite WR140R bladder tank. Should I replace it with smaller tank? If so what size? The pressure switch is currently set at on at 30 psi and off at 45 psi. What is the best settings?

    Booster pump is Goulds J5 with 1/2 HP 3450 rpm 115/230 volt motor. Currently wired for 115. Would I save energy rewiring to 230 volt?
     
  6. valveman

    valveman Cary Austin Staff Member

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    Lubbock, Texas
    It is still a 1/2HP motor no matter if you feed it 115V or 230V. The amperage will just be twice as high on the pressure switch, wire, and breaker on 115V. I can't tell about the pipe lines in your drawing, but the CRL should be on the heat pump discharge, after a tee to the house supply.
     
  7. Dana

    Dana In the trades

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    Pumping power can bring the as-used efficiency of any geothermal system to it's knees if not done correctly. It's too easy to spend a lot of money and still end up with something that underperforms on both capacity and efficiency. This calls for a professional design by a competent designer (and not all geo installers are competent), even if implemented as a DIY.

    Getting to the optimal heating/cooling solution usually starts with an aggressive Manual-J load calculation, an all-important step that is often skipped by DIYers and pros alike, and oversizing by 2x or more based on rules of thumb is more common than not.

    If your actual heating & cooling loads called for a geo unit that would really only need 3 gpm (not 6 gpm) it would be worth knowing right now. If the actual loads could be made that low with upgrades on the house for less money than it costs to deepen the well, that too would be worth knowing.

    What do you THINK your space heating loads are, and how did you estimate that?

    If you have a heating history on the place and only used one type of heating fuel source (say just propane or oil, not a combination of woodstove, electric space heaters & oil furnace or something) a simple fuel-use based heat load calculation can put firm brackets on the likely load fairly quickly to avoid the oversizing problem. With the high cost of geo systems you're better of being slightly undersized and use resistance heat strips to cover just the shortfall during the coldest 100-150 hours of the heating season, whereas oversizing a hot air furnace by 2x costs next to nothing in up front cost or ongoing efficiency.
     
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  8. Twotone

    Twotone New Member

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    Sep 6, 2018
    Location:
    East Central Ohio
    Thanks so much. My thinking was the existing booster pump motor would be more efficient and use a little less kwh to produce the same hp at the higher voltage/lower amperage if I rewire it to 230V.
    Sorry about the piping lines. I tried to color code the lines. The light blue is the line from the sub pump to the heat pump. The dark blue line, kinda blends with the green building line. It tees off the heat pump to the storage tank and also to the drain tile. A solenoid valve and CRL would be installed on the drain side of the tee. My question on the solenoid and CRL valves is, does the location matter? As in close to the heat pump or close to the drain tile.
     
  9. valveman

    valveman Cary Austin Staff Member

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    Pump Controls Technician
    Location:
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    As long as the solenoid/CRL is after the tee to the house supply, it doesn't matter how far away it is.
     
  10. Twotone

    Twotone New Member

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    Sep 6, 2018
    Location:
    East Central Ohio
    What size booster pump tank do you suggest? Use the existing 44 gallon bladder tank, depressurize and add a CSV?
     
  11. valveman

    valveman Cary Austin Staff Member

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    Pump Controls Technician
    Location:
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    A 44 gallon pressure tank only holds 10 gallons of water. If the tank is still good you can use it with a CSV. If the tank needs to be replaced, anything larger than a 10 gallon tank tank is more than you need with a CSV.
     
  12. Twotone

    Twotone New Member

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    Sep 6, 2018
    Location:
    East Central Ohio
    Thanks for you knowledge. I ordered the CSV for the booster pump. Do I depressurize the pressure tank?
     
  13. valveman

    valveman Cary Austin Staff Member

    Joined:
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    Occupation:
    Pump Controls Technician
    Location:
    Lubbock, Texas
    No. With a large pressure tank you just set the CSV closer to the off pressure setting. Like with a 40/60 switch set the CSV at 55 PSI.
     
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