What does return air refer to in an HVAC system?

Return air in an HVAC system refers to the air that is pulled from the conditioned space back into the system for reconditioning. This air is typically at a temperature that has already been altered by the heating or cooling process and is sent back to the air handler or furnace to be reheated or re-cooled as necessary.

In the context of the choices provided, the correct answer emphasizes that return air is effectively the air that is cycling through the system after it has been heated or cooled and is then drawn back to continue the process. This ensures a continuous flow of conditioned air throughout the space.

The other options describe different aspects of HVAC function but do not accurately define return air. For example, air cooling the compressor does not pertain directly to the concept of return air, but rather refers to the cooling process within the refrigeration cycle. Air being distributed to supply vents describes the conditioned air leaving the system, contrasting with the return air’s role in bringing air back to the system for further conditioning. Lastly, air discharged outside refers to exhaust air, which is not part of the return air cycle but instead relates to the removal of air from the building to maintain efficiency and manage humidity levels.