Comments on ground loop specs in quote

Discussion in 'Vertical and Horizontal Loops' started by grein002, Sep 1, 2010.

  1. grein002

    grein002 New Member

    I've been quoted a geothermal system, and would like feedback, particularly with regard to the loop (bore # & depth, etc):

    I've not heard of multiple loops being installed per bore before. This contractor says they have had great success with this in the RTP NC area for a number of years (obviously I will be checking his references). Opinions welcome...

    -Scott
     
  2. Double loops are just starting to be used in the U.S. for some residential and commercial. They are the norm in europe. Double loops can reduce the total borehole footage by 15% and may make sense in geologies that are expensive to drill like crystalline bedrock where you are already using large diameter downhole hammers. The average borehole length is around 150-200' per ton in your area so 420' of borehole is definitely on the low side even with the 15% reduction. I'd want to see this run in a design program and take a look at the entering water temps, btu's produced etc.

    -Adam
     
  3. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    In MI common installations are about 150' of vertical bore/ton with 3/4" loop, there are many variables but your proposed design offers more. Conditions are wildly different for reasons mentioned by d2e.

    What jumped out at the mechanical inspector in me was:
    " NO VEHICULAR PROTECTION IS INCLUDED. Add $350.00 if required by inspections department."
    Forgive me if it varies as we use the MI amended International Mechanical Code here, but 303.4 Protection from damage reads:
    "Appliances shall not be installed in a location where subject to mechanical damage unless protected by approved barriers."

    What's more 304.3 Elevation of ignition source states "Equipment and appliances having an ignition source and located in hazardous locations.....private garages......shall be elevated such that the source of ignition is not less than 18 inches above floor surface......"

    Thrust is to avoid ignition of fuel vapor, so things they reside in the bottom of heat pumps i.e. contactors, or motors on flow centers, etc potentially could spark.

    Not all municipalities enforce IMC and interpretation varies......
    Good Luck,
    Joe
     
  4. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    I am curious to know if your installer is using the "rehau" system or just stuffing two loops in one hole. Iregardless of any discusion here if you trust your installer and he/she has a good track record and reputation in your area, nuff said.
    Eric
     

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