How to Adjust a Johnson Controls Low Pressure Switch

Use the low side range screw --- usually found on the left side, towards the back of the switch controls --- to set low side cut-in. For All-Range controls, turn the screw clockwise to raise the cut-in set point. For Micro-Set controls, turning the screw clockwise lowers the cut-in set point.

Adjust the differential screw, located on the front left side of the switch controls. Turning the screw clockwise raises the cut-in set point on All-Range controls. With Micro-Set controls, turning the differential screw clockwise increases the differential setting.

Set high side cut-out set point by adjusting the high side range screw on the front right side of the switch controls. Turn the screw clockwise to raise the cut-out set point. Note that the high side differential setting is fixed and cannot be adjusted.

If your Johnson Controls low pressure switch is a P70S or P170S model, set the reset operation for high side automatic reset or manual reset lockout with the reset button on the front of the switch. After the sensed pressure has reached the desired level, press and release the reset button to restore operation of the controlled equipment.

Cycle the controlled equipment at least three times at normal operating conditions. Monitor the equipment with a reliable pressure gauge to verify that the pressure switch is correctly set and all equipment is operating as expected.