Johnson Controls A28AA-20 Temperature Control

The Johnson Controls A28AA-20 is a heavy-duty two-stage temperature control designed for multi-stage heating or cooling applications in commercial refrigeration and HVAC systems. Featuring dual SPDT switches, this controller allows for independent sequencing of equipment loads, making it ideal for managing staged compressor banks or ventilation systems. The unit operates across a wide voltage range, including 120/208/240/277 Vac, ensuring compatibility with most industrial power configurations. With a setpoint range of -5 to 28 degrees Celsius and a 6-foot capillary, the A28AA-20 temperature control provides accurate sensing even in remote or deep-reach installations. As the direct replacement for the A28AA-9, it transitions the scale from Fahrenheit to Celsius while maintaining the same physical footprint and reliability. Technicians rely on this refrigeration temperature controller for its rugged construction and precise dual stage thermostat functionality in demanding environments.

• Dual Stage Sequencing: Two independent SPDT switches allow for precise control of two separate stages of heating or cooling.
• Wide Voltage Compatibility: Field-adjustable for 120, 208, 240, or 277 Vac circuits, reducing the need for multiple SKUs.
• Direct Replacement: Specifically engineered to replace legacy A28AA-9 models with updated Celsius-scale calibration.
• Remote Sensing: The 6-foot capillary length facilitates flexible bulb placement for accurate ambient or liquid temperature monitoring.

How do I wire the Johnson Controls A28AA-20 for cooling applications?
For cooling, wire to the "Common" and "Open on Rise" terminals of each SPDT switch. This ensures the stages activate sequentially as the temperature rises above your setpoints.

Is the A28AA-20 compatible with 277V systems?
Yes, the internal switches are rated for 277 Vac, making it suitable for commercial lighting or heavy-duty HVAC equipment operating on higher voltage legs.

Can I use this to replace an A28AA-9?
Yes, the A28AA-20 is the designated replacement. Note that the scale is in Celsius, so recalibration of your setpoint targets from Fahrenheit may be required during installation.

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.