The 3.5-ton, 14-loop, geo-thermal, direct-exchange, EarthLinked® heating and cooling system is efficient and easy to service, says the manufacturer. Unlike other geothermal systems that rely on plastic tubing to transfer water and anti-freeze through a large intermediate loop, EarthLinked circulates refrigerant through highly conductive copper earth loops, enabling more direct transfer of thermal energy from the earth, says the company.