The AFS Series Differential Pressure Switches are general purpose proving switches designed for both HVAC and Energy Management applications. These pressure switches can be used to sense positive, negative, or differential air pressures when used in conjunction with an A/SPT or A/VPT Series sampling tube. The plated housing contains a diaphragm, calibration spring and single snap-acting contact closure with either a manual or automatic reset switch depending on the model. The enclosure cover contains a ½” conduit knockout and guards against accidental contact with the live switch terminal screws as well as the set point adjusting screw. Applications: Monitoring Filter Blockage, Proof of Flow, Prove Excessive or Insufficient Flow, Alarms and Control