Refrigeration for HVAC
Air conditioners and heat pumps use the process of refrigeration to provide heating and cooling. What is the definition of the process of refrigeration? Refrigeration is the process of moving heat and depending on whether it is a heat pump or air conditioner and what mode it is in will depend where you are moving the heat. An air conditioner and a heat pump (in the cooling mode) will move heat outside. The evaporator coil absorbs the heat and the condenser rejects the heat.
Refrigeration for HVAC - Heat Pumps and Geothermal Systems
A heat pump in the heating mode absorbs heat from the outside air (the average air source heat pump is only good down to approximately 38 degrees Fahrenheit before the process of refrigeration becomes inefficient) and move the heat to the inside. Many heat pumps and air conditioners use the vapor compression refrigeration method to provide heating and cooling. Vapor compression refrigeration utilizes a compressor, condenser, metering device, and an evaporator coil.
Water source or geothermal heat pumps do not have this problem since the source of where the heat pump absorbs heat is a constant 50 degrees plus or minus slight variables. Air source heat pumps need a backup source of heat so when the temperature outdoors falls below 38 degrees Fahrenheit the served space can remain comfortable. The typical source of backup heat for air source heat pumps is electric heat strips. Other sources of back-up heat for air source heat pumps include gas heat and oil heat. For efficiency reasons, the heat pump condenser should be set up with an outside air temperature cut-out switch to disable the heat pump condenser when the outside ambient air temperature falls below 38 degrees Fahrenheit.
The diagram below illustrates the entire refrigeration process from beginning to end for the process of refrigeration used in HVAC. If you drew a diagonal line from the compressor to the metering device you would illustrate and separate the high pressure side of the refrigeration system from the low pressure. Without any one of any these four components the process of vapor compression refrigeration would not be possible.
Related Link: Learn more about Piping Design and Best Practices for Refrigeration Piping (opens in a new window)
Additional resources for refrigeration can be found here.