Demonstration of Geothermal Heating & Cooling Installation

The owner of this new 3,000-square-foot home in Mechanicsburg, Pennsylvania, learned about direct-exchange geothermal heating/air conditioning systems on the Internet, as he was planning construction. Through research, homeowner Del Leese quickly became aware of the unparalleled efficiency, comfort and cost savings provided by such systems, and was impressed with the fact that direct-exchange geothermal systems require no fuel or energy beyond the small amount needed to operate the compressor.

In direct-exchange geothermal systems, a compressor unit and air handler are installed inside the home, not outdoors, as with conventional air-conditioning systems. This aesthetic benefit is one of the system’s selling points.

At the heart of direct-exchange geothermal systems is a series of copper earth loops and a copper manifold installed underground, outside the home. Copper earth loops can be installed in several different configurations, depending upon site specifications like soil characteristics, space availability and equipment costs.

For Del Leese’s property, 14 holes were drilled diagonally at 30-degree angles in a circular configuration with a 6-foot diameter. Mechanical contractor Jeff Demme chose this setup because it consumes less surface space than others, so more property is free for planting.

After the holes were drilled, a copper earth-loop fabricated with 1/4″ and 3/8″ seamless Air Conditioning and Refrigeration (ACR) copper tube supply and return lines were fed into each hole. These lines circulate the refrigerant back and forth from equipment in the house to the earth loop field.

Once all the copper tubes were installed, sand was used to backfill the holes using a sand-water slurry.

Next, the centre of the circle was excavated to 4 feet below grade, where the earth’s temperature is relatively constant.

All of the copper lines are joined to a corresponding supply or return manifold, which provide a junction where the 14 earth loops converge, channeling refrigerant through return and supply lines that are connected to the compressor.

A 4-foot-deep trench was dug from the manifolds to the house foundation to accommodate the house supply and return lines.

The copper supply and return lines were connected to a compressor, which pressurizes the refrigerant according to the need for heating or cooling, based on the thermostat setting. Heat energy released by the pressurized refrigerant may be either channeled to the air handler if heat is needed, or back to the earth for cooling indoor air temperature. The process is controlled by a reversing-valve.

Copper tube was then run from the compressor to the air handler. The air handler is used to circulate the heat into the home, or extract it from the home by carrying it through ducts.

A water heater connected to the direct-exchange system can either use waste heat given off in the air-conditioning mode or ground-source heat generated by the heating mode to reduce water-heating costs by as much as 70 percent compared to electric-resistance heating.