Direct Exchange Geothermal Systems Use Copper Instead of Plastic
Typical water-source geothermal heat pumps use high density plastic pipes and a pump to circulate water through deep-drilled loop systems. A direct exchange (DX) heat pump system is a different system that eliminates the plastic water pipe systems, allowing the DX to reach slightly higher efficiencies while using a relatively shorter and smaller set of buried tubing, reducing installation cost. Instead, the refrigerant circulates through copper tubing placed in the ground, exchanging heat directly with the soil through the walls of the copper tubing.
These DX systems, like water-source systems, can also be used to heat water in the house for use in radiant heating applications and for domestic hot water, as well as for cooling applications.
The key difference in a DX system is that there is only one heat transfer process in the DX system. In direct-exchange systems, the refrigerant is distributed through copper tube, which is in direct contact with the earth heat source for effective thermal transfer. Water-based systems rely on two transfer stages, requiring more energy, as well as a circulating pump, which is not necessary for direct-exchange systems. The reduction in energy usage coupled with the cheaper tubing installation costs make DX systems attractive, however there are some lingering questions about DX within the industry.
Criticisms of DX loop fields arise because the initial installation procedures are crucial. Any slight failure in the system creates a large headache which is why its imperative to have a trusted contractor, especially when considering DX.
Overall, these direct exchange geothermal systems provide noticeably greater comfort than conventional heating and air conditioning. Even despite using less energy, geothermal is able to achieve this because the heat source is the earth...warmer than ambient air in the winter and cooler than ambient air in summer. Because of the warmth of the earth, geothermal systems deliver greater warmth in the winter without sudden blasts of heat like a furnace, and don’t have to “heat up” - the source is already warm. In the summer, the ability to sustain longer run cycles and usage of cooler evaporator coils deliver cooler air with significantly less humidification…providing noticeably more comfort within all areas of the home.