1. The cycle starts as cold liquid refrigerant within the heat pump passes through a heat exchanger (evaporator) and absorbs heat from the low-temperature source (fluid circulated through the earth connection)
  2. The refrigerant evaporates into a gas as heat is absorbed.
  3. The gaseous refrigerant then passes through a compressor where it is pressurized, raising its temperature to over 180 degrees F.
  4. The hot gas then circulates through a refrigerant-to-air heat exchanger where the heat is removed and sent through the air ducts.
  5. When the refrigerant loses the heat, it changes back to a liquid.
  6. The liquid refrigerant cools as it passes through an expansion valve, and the process begins again.