The Cleveland Controls RFS-4100-040 Adjustable Pressure Switch is a sensing and safety control designed to monitor air pressure in compatible HVAC equipment. It operates by detecting pressure changes and activating or interrupting an electrical circuit when the pressure reaches its adjustable setpoint. Commonly used in furnaces, air handlers, ventilation systems, and combustion equipm... https://www.partshnc.com/rfs-4100-040-cleveland-controls-15-5-wc-adjustablepressuresw