Ohio Soil conditions horizontal loop

Discussion in 'General Discussions' started by Adam Porter, Dec 13, 2018.

  1. Adam Porter

    Adam Porter New Member

    Hello, I am a new member located in eastern Ohio. I am a licensed HVAC contractor . However I am new to geothermal and think I know just enough to be dangerous . I am seeking advice based on experience, and data and greatly appreciate everyone's time and input. That being said I am considering doing my own geothermal system for my home. I would prefer to do most work myself obviously and save money and learn along the way for possible future installs.

    So to start I was thinking of doing a horizontal loop field because I have heavy equipment capable of digging 10'+deep. My land area is basically unlimited and pretty flat.

    My first concern is my soil conditions. I have maybe 18-24" of topsoil and then it turns to layers of shale . Is the shale going to allow acceptable contact / transfer? I would think fractured rock and moisture after backfill would be a good thing? Rock is a good conductor of heat ....I have many more questions but figured I'd start with that.

    Last edited: Dec 13, 2018
  2. arkie6

    arkie6 Active Member Forum Leader

    Shale is fine, especially if it is moist.

    Once you have determined your heating and cooling loads, you can download loop sizing software at the Climatemaster website and get a feel for how much loop pipe you need at what depth.
  3. Adam Porter

    Adam Porter New Member

    Thank you for the response. I was thinking shale would be acceptable but just wanted more experienced folks opinion before I went too far. That was what I wanted to know. If I had to go vertical or not.

    Yes that is my next task. Doing my heat gain/loss. I will report back soon.

    Can anyone tell me how much more energy or efficiency the vertical would be compared to the horizontal? My goal is obviously to not have to supplement with electric or propane. I think that is still achievable with a properly designed horizontal loop correct? To me the cost of drilling outweighs the lesser efficiency. But again I'm hypothesizing.

  4. Adam Porter

    Adam Porter New Member

    I cannot get the software to download for some reason.

    Would you be willing to run the program for me ? I'd be willing to pay you even. I have all my heat gain/loss completed. I actually posted on the general discussion forum with alot of the details.

  5. nc73

    nc73 Member Forum Leader

    where in Ohio?
  6. Adam Porter

    Adam Porter New Member

    Located in eastern Ohio near St clairsville
  7. nc73

    nc73 Member Forum Leader

    Darn, was hoping you could dig me a Pond :) I almost rented equipment to dig horizontals but I'm not good at it so I'm going vertical. I owned a backhoe for a short time once, and it was hard to dig past 5 ft, not mention my bucket wasn't wide enough. They charge arm and a leg here just for trenches, it was actually almost the same price to drill.
  8. arkie6

    arkie6 Active Member Forum Leader

    I downloaded the program on my work computer several years ago and never had any issues. Tonight I tried to download it on my home computer and got an error when I tried to open. Apparently you have to have some type of "key" to use the software now. If I was at work, I could do it on my old version of the software, but unfortunately, I'm not planning on going back to work for the next 3 weeks. If you can wait until after then, I can run it for you.
  9. Adam Porter

    Adam Porter New Member

    Hi Arkie,

    Yes I got the same error message. Unfortunate. Especially when it is suposuppto be promoting their product. Anyhow yes that would be so great if you could run it for me. I can wait until then.

    Is there a rule of thumb or from your experience do you have an idea of the loop I'd be looking at ? I have a 3.5 ton air heatpump now.... Propane modulating furnace rated at 90k btu. Just wondering if you had an idea?

    Thanks again
  10. arkie6

    arkie6 Active Member Forum Leader

    Have you done a Manual J heat load analysis of your home? If not, how large is your home? When was it constructed? What is the amount of wall, ceiling, and floor insulation? Quality of windows and doors? Gas furnaces are typically way oversized for the heat load, so they are hard to use as a gauge for sizing a heat pump. Now if you know your gas usage over a typical cold month and and can get the heating degree days for your location during this time period, you can back calculate how many actual BTUs were used and use that to size a unit.

    A common practice is to slightly undersize the heatpump for heating load and let electric heat strips pick up the ~5% of days where heat load exceeds the capacity of your heat pump. You spend $100 or less on extra electricity per year, but save thousands on initial unit purchase and installation. Sizing the unit for full heating load in a colder climate then typically makes the unit oversized for cooling which makes for poor humidity control unless the unit is a multi or variable stage unit.

    Say you have a peak heat load of around 50k BTU at design temperature. You might then select a 4 ton geothermal heat pump. This would typically cover ~95% of your heating load with the remainder being covered by electric heat strips. If it is a two-stage unit, first stage is typically 2/3 of full load rating or in this example 2/3 x 4 ton = 8/3 ton or 2.67 tons which is more effective for humidity removal in summer.

    With a 4 ton unit you would typically use four (4) parallel ground loops.

    Typically, you would need around one (1) 3/4" x 600' loop at 6' or greater depth per ton of HVAC, 2' wide trench, 300' out and back (racetrack loop). Many folks on here like slinkies where you put 3/4" x 800' in a 3' wide trench, but shorter in length. If you have the land area, I think a racetrack loop design is more effective, uses less pipe, and has less pumping losses.
  11. Adam Porter

    Adam Porter New Member

    Thanks again for the detailed response and folkfoup questions. So yes I did do a manual J . It was a free software program called HVAC calc 4.0. it was pretty decent I think. I went room by room and input all the data. It yielded a heat gain of around 38k BTU/H. And heat loss of around 67k BTU/H. That said my house was constructed about 5 yrs ago. It's pretty tightly constructed with house wrap .No air leaks that I'm aware of really.

    Insulation is R-13 ( 4.5 " )in the walls,
    R-38 (10" ) in the second floor ceiling. Blown in no floor insulation. .
    Basement is not exactly heated but is nearly 8' below grade and stays around 60 degrees .
    Windows are good quality double pain .

    Total sqft of the house is 2400.
    The basement is 1100sq ft. Again basement isn't heated but stays decent. I could easily dump a couple runs in if need be.

    I have a modulating 98% propane furnace and on low stage it is like 30kbtu and on high it's 88kbtu. I also use a 21 seer 3.5 ton air heat pump. My plan would be to supplement with the propane since I have it already....

    So if I understand you correctly if I used a racetrack loop it would be 4 trenches 2' wide 300' long each and 6-8 ft deep. Which would be 2400 ft total of sdr 11 3/4 hdpe?

    Thank you and look forward to learning more.
    I don't take the infroinformor time for granted. I really do appreciate the information and education.
  12. Eric Kurtz

    Eric Kurtz Member

    I used Loop Link web site. Really liked it.
    Do a Google search for it. It has all the different HP programmed in and you can adjust your loops and see estimated min EWT plus your cost to run compared to other heating sysyems.
  13. Adam Porter

    Adam Porter New Member

    Thanks Eric. I will look it up and give it a try. I appreciate the advice and respires.
  14. nc73

    nc73 Member Forum Leader

    You could do it the easy way and get some bids. They'll lay out all the details for you.
  15. Adam Porter

    Adam Porter New Member

    Hi Nc. I am considering doing that too. Problem is there are not alot of dealers in my area . Closest one is an hour away. It seems like very few are experienced in a horizontal loop field.... Based on some discussiona I have had with a couple in my area. But thanks for the reply.
  16. nc73

    nc73 Member Forum Leader

    Maybe employ one of the pros here to design it for you? Geojerry.com does DIY designs too.
  17. Adam Porter

    Adam Porter New Member

    Yes. I am certainly willing to do so. Arkie is helping me out alot as well . But I'm willing to .I'm learning alot and calculating everything myself as well. But not being experienced in gwo installs is a big disadvantage. I'm sure there are many variables to consider that I am not aware of. Anyone can punch some numbers into the free calculators like I did . But I'm concerned about the things you get from experience.... So hopefully Arkie and others can help me out. But I'm absolutely not opposed to hiring for professional help. Thanks again
  18. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader


    PM me. Happy to help.
    The issue with shale is that sharp rock can damage the pipe in the long run, thus it is important to backfill with the shale/rock free overburden around the pipes to protect them.

    The pipe will move on a microscopic level due to expansion and contraction, between the seasons, due to temperature differences between winter/summer. A sharpe rock laying right on top of it can cut into the pipe over time.

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