The deep earth temperature is very important in sizing ground source heat exchangers. Ewbank testing equipment directly measures the deep earth temperature at the start of a test during the first circulation of the earth loop. Water is pumped into one side of the loop and the other side flows undisturbed, in temperature, water from the loop. Additional circulations add the heat from the circulating pump and very slowly increases the loop temperature. Ewbank records, at one second intervals, both loop leg temperatures. One can measure and record the temperature profile of the borehole. The map at the left is a location for the South Range Schools in-situ thermal conductivity test where the deep earth tempeature was recorded. The borehole was 400 feet in depth and 5.75 inches in diameter. The borehole had a 1-1/4 inch HPDE SDR-9 loop inserted. It was grouted from the bottom to the surface with 1.0 Btu / (hr*ft*°F) enchanced grout. The test borehole was drilled and installed by Jackson Geothermal, 3401 St. Rt. 13 S., Mansfield, Ohio 44904. www.jacksongeothermal.com

The test was conducted on March 26, 2008 by Zachary Dye and witnessed by John Turley each with Middleton Geothermal Services L.L.C., P.O. Box 4893, 400 E. Cuyahoga Falls Avenue, Akron, Ohio 44310. www.middletongeothermal.com

The test providers team of Mr. Greg Wells with Jackson Geothermal, Mr. John Turley with Middleton Geothermal, and Mr. Garen N. Ewbank with Ewbank and Associates, L.L.C are members of the Internation Ground Source Heat Pump Association (IGSHPA). Greg and John are current members of the IGSHPA Advisory Board and Garen is a former member.

The test was at the intersection of W. Middleton Road and Green Beaver Road and the Canfield Columbiana Road (highway 46). It is in eastern Ohio west of highway 46 that runs south from Canfield to Columbiana, Ohio.

The graph ( click here) of the blue line is the undisturbed leg of the ground loop. The first downward peak at 19:19:30 indicates the test was ran during the winter season as the surface was colder then the lower borehole. The temperature began to increase until 19:22:30 and this was the bottom of the loop temperature. One can clearly see a temperature gradient that increases with depth. The increase is from the geothermal heat of earth, not solar heat.