A28AA-29C Johnson Controls Temperature Control

Overview

The Johnson Controls A28AA-29C is a heavy-duty, two-stage mechanical line voltage temperature control designed for reliable temperature sensing in demanding commercial HVAC and refrigeration systems. It features a liquid-filled sensing element with a remote bulb and capillary, offering precise control over a wide temperature range. Encased in a durable NEMA 1 galvanized steel enclosure, this control operates entirely mechanically without the need for external power, making it ideal for robust environmental monitoring.

Features

• Two-stage temperature control with two independent SPDT snap-acting switches
• Liquid-filled sensing element ensures fast and accurate response
• Adjustable interstage differential (2 to 7°F) for custom stage sequencing
• Front-facing convertible adjustment for exposed knob or concealed screwdriver setpoint configuration
• Unaffected by changes in barometric pressure or cross ambient conditions
• Solid steel NEMA 1 enclosure protects internal components in industrial environments

Specifications

• Temperature Range: -30°F to 100°F (-34°C to 38°C)
• Switch Action: Open/Close on Rise (SPDT)
• Capillary Length: 8 feet (96 inches)
• Sensing Bulb Size: 3/8″ diameter x 4″ length
• Enclosure Rating: NEMA 1 Gray Galvanized Steel
• Electrical Rating: 120/208/240/277 VAC; 16.0 Full Load Amps @ 120 VAC
• Pilot Duty Rating: 125 VA

Applications

• Temperature sensing and automatic changeover control for HVAC and refrigeration systems
• Dual-stage heating and cooling plant sequencing
• Environmental control in commercial, agricultural, and light-industrial facilities
• Ventilating and exhaust fan control strategies based on dual temperature points