What does a thermostat do in an HVAC system?

A thermostat's primary function in an HVAC system is to automatically control the temperature within a designated space. It achieves this by constantly monitoring the ambient temperature and comparing it to the setpoint temperature that the user has established. When the ambient temperature deviates from the setpoint, the thermostat sends a signal to the HVAC system to either activate heating or cooling equipment to help maintain the desired temperature.

This functionality makes the thermostat an essential component for ensuring comfort and energy efficiency within residential and light commercial settings. It allows users to maintain their desired indoor climate without manual intervention, thereby optimizing both energy consumption and comfort.

The other choices pertain to functions that are outside the thermostat's role. For instance, regulating the flow of refrigerant is a function of components like expansion valves or compressors, filtering dust from the air is the responsibility of air filters, and directing air into ductwork pertains to the system's air handling components rather than the thermostat itself.