Thermal Conductivity??

Discussion in 'Vertical and Horizontal Loops' started by ampicoj, Jul 22, 2010.

  1. ampicoj

    ampicoj New Member

    Just recently installed 8 tons of geothermal (5 ton first floor Carrier/Climatemaster) and 3 ton second floor split system).

    The spec for the wells, in particular the grouting section, calls for a (thermal) conductivity of 1.2.

    Can anyone provide a definition for this term? How would compliance be measured? Is this done in practice?

    I'm beginning to collect operational data - loop temps, power consumption. If anyone is interested, be more than happy to share this information.

    Many thanks,
  2. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    Hi and welcome,
    The spec for a thermal conductivity for your grout to be 1.2 means that between 300 and 400 pounds of silica sand was added to every 50# sack of grout that was used, depending on the brand of grout used.
    It is becoming more widely accepted that the use of any thermally enhanced grout above .8 is an exercise in money not well spent. By applying a simple bore hole cost calculator it is easy to see. Also the reduction in loop footage based on the use of thermally enhanced grout without the data from an active loop conductivity test on site is also folly. More than you asked for, but I am pasionate about "economical efficeincy" sp
    hope this helps
  3. Looby

    Looby Member Forum Leader

    I'll assume that's 1.2 BTU/hour•foot•°F -- meaning that 1.2 BTU per hour
    will flow through each square foot of a one-foot-thick slab of grout -- for each
    one degree F difference in temperature between the two faces of the slab.

    Heat flow is directly proportional to TC, area, and delta-T -- and inversely
    proportional to path length (i.e., thickness of the slab).

    Please, don't try this at home, kiddies.

    Normally, it's not measured in the field. The installer just follows a recipe
    supplied by the grout manufacturer -- as waterpirate described, above.

    For more info on TCs of geothermal grouts, see pg 7~11 of the following:

    McQuay Geothermal Heat Pump Design Manual

    Last edited: Jul 23, 2010

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