Testing borehole capacity after installation

Discussion in 'Vertical and Horizontal Loops' started by dvroblesky, Sep 3, 2010.

  1. dvroblesky

    dvroblesky New Member

    Is there a simple way to test the thermal capacity of a borehole after the loop insertion and grouting? Thanks for your help.
  2. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    It is called a conductivity test. Simple version= impart a given load to the loop in question for a given amount of time, usually 40 hours minimum, and chart the temp change with data logger. Smash all that data into some software and you get a good idea of the capacity of the loop.
  3. dvroblesky

    dvroblesky New Member

    I do know about the "in situ" conductivity testing done primarily on commercial projects. It seems like the test itself runs about $4k and the drilling another $5-$6k. Is there a way to test the thermal properties of a loop in a more cost effective way? I know you could save on the drilling by using it as the loop field, but is there a more basic, cost effective way?
  4. Bore hole heat exchange rate

    Best way is to simply find out from existing geothermal users in the area. The test itself is expensive, but surely there are dozens of installations near to you to provide a good experience base. Talk to a couple of local installers.
  5. The thermal testing equipment consists of a water heater and a circulation pump hooked to the ground loop simply supplying a specified btu/hr. This certainly can be self-constructed.

    Recording the EWT and LWT readings every 2 min for the first hour and gradually extending the temp readings out to every hour allows you to plot the temp over time where the slope of the best fit line is proportional to thermal conductivity (inversely proportional to resistance).

    A datalogger to record the temp readings is what is most expensive but if you have the time (48 to 72 hrs) you could do so with a pencil and graph paper...

  6. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader


    A very steady and consistent btu/hr is the difficult component. Energy output also has to be monitored (not assumed).

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