Glossary of geothermal heating and cooling

The "Glossary of Geothermal Heating and Cooling" provides definitions of many terms used within the Geothermal heat pump industry. The terms in this glossary may be used by industry professionals, for education materials, and by the general public.
G.
Ground Source Heat Pump (GSHP).
In a closed loop system, the heat exchanger is typically coils of high-density polyethylene pipe installed in the ground under or around a building. A heat transfer fluid, usually water or water mixed with antifreeze (propylene glycol, ethanol or methanol), is circulated through this pipe, warming or cooling to the temperature of the earth or rock around it.
In open loop systems the pipe draws water from a well, lake or pond. After it is warmed or cooled the water is returned via a discharge well or back to the lake or pond.
The fluid from the open or closed loop is circulated through a heat pump. The refrigerant in the heat pump either extracts heat from the fluid or rejects heat to it, cooling or warming the refrigerant. When heat is absorbed by the refrigerant, the heat pump boosts its temperature and sends it to the air handler to circulate hot air to heat the home and (optionally) to a hot water heater to produce domestic hot water. The now cooled fluid goes back into the closed loop or, in an open loop system, is sent back to its source.
When the heat pump cools the building, the air handler transfers the heat to the heat pump's refrigerant, warming it and the heat transfer fluid. The now heated fluid circulates back into the closed loop for cooling back to the ambient ground temperature. In an open loop system is sent to the discharge well or back into the lake or pond.
N.
Non-Pressurized Flow Center.
A flow center that maintains a flow of water into the suction side of the pump (maintaining a flooded volute and reliable pump operation) by having the pump located directly adjacent to a column of water (in a canister). As a result, the system can operate at "zero" or atmospheric pressure. Thus the term "non-pressurized" simply means a device that allows for reliable pump operation without the need to elevate the system pressure (typically 20-60 psig for pressurized systems). Non-pressurized does not mean that the system is open to the atmosphere, but simply a closed sealed system that operates at atmospheric pressure.