Johnson Controls P70MA-2 Pressure Control

The Johnson Controls P70MA-2 Pressure Control is a heavy-duty dual pressure switch engineered specifically for ammonia refrigeration systems (R-717). This SPST switching control integrates both high and low-side protection into a single, ruggedized all-steel enclosure, meeting the demands of commercial and industrial ammonia plants. The low-pressure side features a wide adjustment range from 20" Wc to 100 psi with a tunable 7 psi to 50 psi differential, allowing for precise pump-down control or low-limit protection. For critical safety, the high-pressure side operates between 100 psi to 500 psi and utilizes a manual reset lockout, ensuring the system remains offline for inspection following a high-head pressure event. Equipped with a 1/4" female NPT connection to resist the corrosive properties of ammonia, this Penn P70 series control provides reliable compressor protection and is a standard for contractors troubleshooting industrial cooling loops.

Key Benefits

• Ammonia Compatible Construction: Features specialized materials and a 1/4 inch NPT fitting designed to withstand corrosive ammonia environments.
• Manual Reset Safety: The high pressure lockout necessitates a technician's manual intervention, preventing hazardous automatic restarts after a high-pressure trip.
• Sight-Set Calibration: Built with visible, calibrated scales for both high and low sides, enabling fast and accurate pressure setpoint adjustments without removing the cover.
• Micro-Set Differential: Provides fine-tuned control on the low-pressure side, essential for maintaining stable suction pressures in complex refrigeration cycles.
• Rugged NEMA 1 Enclosure: The all-steel case protects internal SPST switch components from mechanical damage in demanding engine rooms.

Common Questions

Is the Johnson Controls P70MA-2 compatible with standard HFC refrigerants?
While functionally similar to other P70 models, the P70MA-2 is specifically built for ammonia refrigerant applications. For non-corrosive refrigerants like R-404A or R-22, a standard flare or capillary model is typically preferred.

How do I wire this for compressor protection?
This single pole single throw control is typically wired in series with the compressor contactor coil. The circuit opens on a low-pressure drop or high-pressure rise, effectively breaking the control circuit and stopping the motor.

Can the high-pressure manual reset be converted to automatic?
No, the P70MA-2 is a dedicated manual reset pressure control on the high side to comply with safety standards for unmonitored ammonia equipment. If auto-reset is required, a different P70 series model must be selected.

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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.