Model AFS-A is a general purpose airflow proving switch designed for package burners, furnaces, and fuel-burning equipment. AFS-A accurately senses positive, negative, or differential air pressure. The plated housing contains a diaphragm, a calibration spring and a snap-acting SPDT switch. The AFS-A has a field adjustable set point range of 0.05″ wc to 12.0″ wc. The screw terminals and set point adjusting screw are protected by an enclosure that accepts ½” conduit. The sample connection located on the low pressure side of the diaphragm accepts ⅛” pipe. The sample connection located on the high pressure side of the diaphragm accepts ¼” pipe.