The Dungs AA-A2 & AA-A4 are air pressure switches for differential, vacuum, or positive pressure with an automatic reset used to monitor the pressure in firing, ventilation, and air-conditioning systems. The AA-A2 can be used for air and non-aggressive gases but is not suitable for natural gas, propane, butane, or other combustible gases.

The Dungs AA-A2-6 switch is designed for making and/or breaking a circuit when the medium pressure changes relative to the set point. These switches feature NPT threaded connections and also a test button in the lower housing.

The Dungs AA-A2 switches are SPDT and the differential pressure acts via the diaphragm against the force of the setting spring on the microswitch. This pressure switch operates without any auxiliary power.

Note: the side Pressure Connection can only be used as a test nipple.

The AA-A2-6 threaded version is equipped with a test button that when pressed interrupts the connection to the 1/4" NPT pressure connection and relieves the pressure below the diaphragm. The microswitch changes the pressure contact position from Normally Open to Normally Closed.  When released, the pressure below the diaphragm builds again and the microswitch returns to its original position.