Geothermal Heat Pump Systems

Missouri Well Construction Rule 10 CSR 23-5 regulates the construction and plugging of heat pump systems. Ground source heat pump systems are designed to heat or cool a structure by using the earth’s constant ground temperature. During winter the outside air temperature averages about 20 degrees Fahrenheit; however, groundwater stays an average of 55 degrees Fahrenheit. The idea of a ground source heat pump system is to pump groundwater or other fluid through a buried loop to a heat exchange unit. The heat exchange unit will transfer the temperature of the fluid to warm your home in the winter or cool your home in the summer. There are three main types of ground source heat pump systems: horizontal closed loop system, vertical closed loop system, and open loop system.

Horizontal systems are only regulated if the horizontal system is constructed at or greater than 10 feet in depth. A vertical closed loop system has a borehole depth limitation of 500 feet and must be grouted full length. For heat systems that are 200 feet or less, the grout plug method is allowed.

Both vertical and horizontal closed loop systems use a loop of heat fused polyethylene or polybutylene pipe. The pipe is laid in trenches (horizontal system) or put down boreholes (vertical system), connected to the heat exchange unit and filled with an approved heat transfer fluid. Approved fluids include inhibited glycol, methanol, ethanol, water, or other fluid approved by the Department.

Open loop systems use a water well to supply groundwater to the heat exchange unit. The water is either pumped back into the ground through a second well or to a surface lake or pond. Keep in mind that if you are disposing of this water to the surface it must remain on the landowner’s property. It may not be run to drainage that leaves the property unless applicable permits are obtained through the Department’s Water Pollution Control Branch.