Johnson Controls P28DN-1 Oil Control

The Johnson Controls P28DN-1 is a high-performance lube oil pressure cutout control engineered for pressure-lubricated refrigeration compressors. Specifically designed for compatibility with ammonia service and non-corrosive refrigerants, this differential pressure switch prevents catastrophic hardware failure by sensing low net oil pressure. The unit features a factory-calibrated 30-second time delay relay that provides a critical buffer during initial startup or short-duration pressure fluctuations, eliminating nuisance lockouts while ensuring the pump reaches the required differential setpoint. With an adjustable range of 8 to 70 PSIG and a manual reset mechanism, it offers veterans a "trip-free" safety interface that cannot be bypassed by simply holding the button down.

Built for 120/240 Vac industrial environments, the P28DN-1 includes dedicated alarm terminals for remote safety monitoring and notification. The bellows-actuated design measures net oil pressure by calculating the difference between the oil pump discharge and the crankcase pressure. This HVAC compressor protection device is essential for semi-hermetic systems where maintaining precise lubrication system pressure is non-negotiable. The dust-protected switch housing and ambient-compensated timing relay ensure reliable low oil pressure cutout performance despite varying mechanical room temperatures.

• Ammonia Compatible: Specially designed for ammonia refrigeration systems and non-corrosive media applications.
• Internal Time Delay: Integrated 30-second thermal expansion relay prevents premature shutdown during startup transients.
• Trip-Free Manual Reset: Mechanical safety lockout ensures the technician must investigate the system before re-engagement.
• Universal Integration: Dual voltage 120/240 Vac heater circuit simplifies wiring for various pilot duty control schemes.
• Precision Scale: Direct-reading scale allows for accurate field adjustment of the pressure cutout threshold.

• How do I calculate net oil pressure for the setpoint? Subtract the crankcase pressure from the oil pump discharge pressure while the compressor is running; set the pointer 6–8 PSI below this value.
• Can this unit be mounted in any orientation? While not position-sensitive, it is best practice to mount the bellows above the liquid level of the crankcase to prevent oil logging in the capillary.
• Why is the manual reset sticking? The thermal delay relay requires approximately 15 minutes to cool down after a trip before the manual reset will engage.

Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.