# Ground Temperature Around Horizontal Loop

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

1. ### TurboTomNew 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. ### urthbuoyWell-Known MemberIndustry ProfessionalForum Leader

Maybe with a google scholar search.

But it is math really - heat transfer equations specifically.

3. ### AMI ContractingA nice Van Morrison songIndustry ProfessionalForum Leader

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

4. ### docjenserWell-Known MemberIndustry ProfessionalForum 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. ### TurboTomNew 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.

7. ### thermalbobNew 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:
http://igs.indiana.edu/Geothermal/ShallowGeothermal.cfm
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
bautio@envdata.com