IREM Certified Property Manager (CPM) Practice Test

The two major systems of most HVAC (Heating, Ventilation, and Air Conditioning) units can be best represented by refrigeration and air-distribution cycles.

The refrigeration cycle is responsible for the cooling of air through the removal of heat, which typically involves a process using refrigerants that absorb heat in one part of the system and release it in another. This cycle is fundamental to the functioning of air conditioning units as it enables the effective cooling of indoor spaces.

The air-distribution cycle is concerned with how the cooled (or heated) air is distributed throughout the living or working space. This involves ductwork, fans, and registers to ensure that air circulates efficiently, maintaining a consistent temperature and air quality.

While the other options incorporate elements of HVAC systems, they do not encompass the primary functionalities as comprehensively as refrigeration and air-distribution cycles do. The heating and humidity control can be components of these cycles, but they don't represent the primary operating systems. Ventilation and air-conditioning, though relevant, are broader terms that don't pinpoint the specific cycles. Thus, refrigeration and air-distribution cycles are the most accurate representation of the major systems within HVAC units.