The Potter PS15 Series Supervisory Pressure Actuated Switches are designed primarily to detect an increase and/or decrease from normal system pressure in automatic fire sprinkler systems. Typical applications are: air/nitrogen supervision in Dry pipe and pre-action systems, pressure tanks, air supplies, and water supplies. The PS15 has two switches. The Low switch is factory set to activate at approximately 10 psi (0,35 BAR) on a decrease in pressure. The High switch is factory set to activate at approximately 20 psi (1,4 BAR) on an increase in pressure. See section heading Adjustments and Testing if other than factory set point is required.