The Cleveland Controls RFS-4100-078 0.17" Low Air Flow Switch is an air pressure sensing device designed to monitor airflow in HVAC systems. It operates by detecting changes in air pressure through a diaphragm mechanism that activates an electrical switch when airflow falls below the specified set point. This switch helps verify proper blower operation, detect insufficient airflow, an... https://www.partshnc.com/rfs-4100-078-cleveland-controls-17-low-air-flow-switch