The process of designing and installing ground-source and groundwater-source heat pump systems is straightforward, but some steps differ from design and specification steps for more common systems. Many of these involve the heat exchanger itself, with considerations of geology and hydrogeology. Others involve drilling technologies and working with a new trade ally, the heat exchanger installer, or "looper". We attempt to help the designer understand the driller's tools, techniques, and the ground they penetrate. This includes an introduction to geology, hydrogeology, soil development, and other conditions that impact the feasibility and economics of borehole heat exchanger (BHEx) and open-loop system installation. Nothing about geothermal heat pump systems is beyond the competence of mechanical designers. However, the design engineer should work with a hydrologist for certain ground-water issues related to water quantity and quality for open-loop (groundwater source) systems.

Units: Dual