In Love With My Underground Heat Exchanger

Imported fine silt is both 6" under and over the Slinky® to preserve conductivity.  Loops rest at 7-foot depth.

Imported fine silt is both 6″ under and over the Slinky® to preserve conductivity. Loops rest at 7-foot depth.

 A Geo Heat Pump Advocate Expresses Love For His Underground Heat Exchanger

 Our carbonless ZNE Home (in Perpetuity)

CaliforniaGeo 10-16-16

Yes, I know it’s halfway toward crazy to love inanimate objects.  But I’ve got to explain that when my underground heat exchanger can provide perpetual carbonless free energy for our zero net energy house—my love is justified!

After eight years of planning, we began our new home project in the Fall of 2011, using heavy equipment to bury horizontal Slinky® loops of HDPE (high density polyethylene pipe) at a seven foot depth deployed in four trenches totaling 350 feet of length.  The effort and the costs were significant, but consider the benefits.

This 3,200 feet of pipe is a much greater quantity than a normal installation in “reasonable soils” because I live on an alluvial fan of coarse sand, cobbles, and larger boulders to 24” in size.  So in our case, the effort and the cost were defensive measures to insure the heat exchange loop would perform normally.  Since our occupancy in the Fall of 2014, I am happy to report my complete satisfaction (and thus my love for this perpetual source of space and water heating, and efficient cooling).


Our three ton geo heat pump receives a closed loop supply of water to its internal heat exchanger that is better than nameplate test temperatures.  This refers to testing used by AHRI (The Air Conditioning, Heating and Refrigeration Institute) to qualify the heat pump for EPA certification.  Our incoming loop has proven to be warmer than the test standard during the entire heating season, and it is cooler than the standard during the entire cooling season.  Moreover, the temperature swings measured at three and seven foot depth near the heat exchanger show no signs of running contrary to normal underground fluctuation at this depth—a signal of perpetual thermal renewability.  In short, we seem to have a thermal resource that will never tire, wear out, cost anything, or fail to serve our needs.

Geo heat pumps can perform this miracle anywhere by a variety of heat exchanger methods, and we can go carbonless anywhere we choose.  Therefore, I love my underground heat exchanger not only for my wife and I, but for everyone, across the globe.

—Bill Martin