Which safety feature is responsible for shutting off the HVAC system if airflow is obstructed?

The safety feature that shuts off the HVAC system if airflow is obstructed is the limit switch. Limit switches are designed to monitor the conditions within the HVAC system, specifically temperature and airflow. When a limit switch detects that the airflow is insufficient—due to a blockage or any other obstruction—it triggers a shutoff mechanism to protect the components of the system from overheating and potential damage. This proactive measure helps ensure the longevity and safety of the HVAC equipment by preventing dangerous conditions that could arise from inadequate airflow, such as overheating of the heat exchanger or compressor.

In contrast, a thermostat mainly regulates the temperature set-point and controls when to turn the HVAC system on or off, but it does not specifically address or monitor airflow issues. The compressor is a crucial component of the air conditioning or refrigeration cycle, responsible for moving the refrigerant throughout the system, but it does not inherently function as a safety device. The evaporator is another component that facilitates heat exchange within the system but does not provide any safety mechanisms related to airflow obstructions.