Low Pressure Sensor / Switch, HVAC

The low pressure cut-off switch contacts are open when the suction pressure is about 48 to 90 kPa (7 to 13 psi) or lower. The switch contacts will close when the suction pressure rises to about 103 to 172 kPa (15 to 25 psi) or above. Lower ambient temperatures, below about -1° C (30° F), will also cause the switch contacts to open. This is due to the pressure/temperature relationship of the refrigerant in the system.