Ground Temperature Around Horizontal Loop

Discussion in 'Vertical and Horizontal Loops' started by TurboTom, Sep 17, 2014.

  1. TurboTom

    TurboTom New Member

    Are there any studies that someone can direct me to of the temperatures around an operating Geothermal loop. Say the system has been running all winter and EWT is 32*F, what would be the soil temperature 2' away, 4' away etc. or how many feet away before we return to undisturbed temps. I realize it depends on soil type climate etc. For the sake of discussion, assume Michigan, damp sand, 3/4 poly, 4'-6' deep. Thanks
  2. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    Maybe with a google scholar search.

    But it is math really - heat transfer equations specifically.
  3. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    You would probably have to provide more info i.e. stable EWT or initial EWT. Kind of loop system foot/ft, load........
  4. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    AJ from ACES has some data on that. We see ice cylinders form usually form only 4-8 inches around the leaving pipes to the loop field. I once had a temp sensor 6 ft away horizontally from the pipe, and it was normal ground temp.
  5. TurboTom

    TurboTom New Member

    Thanks that was kind of what I thought would happen but figured there would be university studies that have installed temperature probes to record the temperature. I have read that loops should be 10 feet apart but never read the supporting documentation to show that was enough.
  6. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

  7. thermalbob

    thermalbob New Member

    TurboTom - I was thinking a few different approaches. 1. I'm sure you've seen that cone-shaped graph with seasonal temperature variation versus depth. I could not put my hands on one but vaguely remember some minimal temperature changes down to 8-10 feet below grade. Turn cone sideways and it might give an idea of possible distances. 2. Shawn Naylor at the Indiana Geological Survey is monitoring soil properties at various sites/soils in Indiana. He is doing good work. I don't think it is published yet but real-time monitoring data can be viewed at:
    terrace or outwash = sandy soil; some temperature variation at 6 feet below grade; ditto cone comment above.
    3. Install temperature probes and measure. This would be the best answer based on your site specific properties.
    PS. What are you hoping to learn from the question?

    Bob Autio

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