Johnson Controls P170AA-118 Pressure Control Switch 100/400PSI Open-Low

The Johnson Controls P170AA-118 is a pressure control switch designed for use in HVAC systems. It helps maintain pressure within a specific range by turning electrical circuits on or off based on the pressure in the system. It is a single-pole, single-throw (SPST) switch, meaning it has one input and one output that connect or disconnect depending on the pressure. In the P170AA-118, it is an “open-low” switch. So, when the pressure falls below a set low limit (100 PSI in this case), the switch completes the circuit and turns on connected equipment. Conversely, when the pressure rises above the set high limit (400 PSI), the switch opens the circuit and powers off the equipment. This helps protect HVAC equipment from damage caused by overpressure or insufficient pressure. Pressure control switches are commonly used in air compressors, refrigeration systems, and boilers.