Johnson Controls A28GJ-33 Temperature Control

The Johnson Controls A28GJ-33 Temperature Control is a heavy-duty two-stage mechanical thermostat engineered for precise thermal management in commercial HVACR and industrial process applications. This remote bulb temperature controller features a 5-foot capillary and a 3/8" x 3-1/2" sensing bulb, providing the flexibility needed for remote mounting in air ducts or tanks. Equipped with dual SPDT switches, the A28GJ-33 allows for independent control of two separate circuits, making it ideal for managing multi-stage heating or cooling loads, or triggering high/low temperature alarms. With a setpoint range of 60°F to 90°F and a wide multi-voltage rating of 120/208/240/277 VAC, this unit integrates seamlessly into various control panels. The open frame design (no enclosure) is specifically intended for integration into existing equipment housings or custom control panels where space and direct access to the knob range adjuster are required.

Key Benefits for Professionals:

• Dual-Stage Logic: Specifically designed to handle two-stage equipment or provide auxiliary alarm signaling through two independent SPDT outputs.
• Wide Voltage Versatility: Field-ready for 120V to 277V applications, reducing the need to carry multiple SKUs for different job sites.
• Durable Sensing Hardware: Features a copper sensing bulb and a 5-foot capillary tube for reliable temperature transmission over distance.
• Simplified Serviceability: The mechanical design eliminates the need for external power to the controller itself and provides a straightforward knob for setpoint adjustments.
• Panel-Ready Configuration: Its no-enclosure, open-frame construction simplifies installation within HVACR control panels or environmental cabinets.

Common Questions:

Can the stage differential be adjusted on this model?
Yes, the A28GJ-33 features an adjustable differential between stages, allowing technicians to calibrate the sequence of operation between the first and second stage loads to prevent short cycling.

Is this control suitable for moisture-heavy environments?
Since this model has no enclosure, it must be installed inside a NEMA-rated enclosure or a protected control panel if used in areas where moisture, dust, or contaminants are present.

What is the maximum bulb temperature for this unit?
The sensing bulb for the A28 series is designed to withstand temperatures up to 250°F, ensuring the liquid-filled sensing element remains intact during system over-temperature conditions.

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.