With a little guidance on ground-source heat pump design temperatures and a few rules of thumb for ground loop flow rates, most engineers are pretty comfortable designing the building side of a ground-source heat pump (GSHP) system. However, many of these same engineers are intimidated by the ground heat exchanger design and often entrust the design to others; “others” could be a mechanical contractor, the heat pump manufacturer, a pipe supplier, or even a software vendor.
A good ground heat exchanger (GHE) design will pay for itself over time and can improve overall system efficiencies with simple design and control approaches, usually beating out more traditional mechanical systems in lifecycle cost comparisons. A 2011 survey on the long-term performance of commercial building GSHPs found the cost of the ground heat exchanger to be 26% of the total system cost, with the remaining 74% attributed to inside the building costs (equipment, piping, controls, etc.). When compared to results of surveys conducted in 1995 and 2000, the ground heat exchanger cost has risen 52% since 1995 while the interior building cost has risen 177% (Kavanaugh, et. al. 2012).