Which component is primarily responsible for controlling system pressure in HVAC systems?

The component primarily responsible for controlling system pressure in HVAC systems is the compressor. The compressor plays a crucial role in the refrigeration cycle by compressing the refrigerant gas, increasing its pressure and temperature. This change in pressure allows the refrigerant to circulate through the system, enabling heat exchange processes to occur in the evaporator and condenser.

By regulating the flow and pressure of the refrigerant, the compressor ensures that the HVAC system operates efficiently and effectively maintains the desired temperature within the space being conditioned. It maintains the pressure differential necessary for the system's overall operation, making it central to the pressure control aspect of HVAC systems.

In contrast, while components like the blower help with air movement and ducts facilitate airflow, they do not directly control system pressure. The expansion valve does regulate the flow of refrigerant into the evaporator but primarily does so based on the temperature and pressure of the refrigerant rather than controlling system pressure in the compression cycle.