A28AA-4C Johnson Controls Temperature Control

Overview

The Johnson Controls A28AA-4C is a two-stage line-voltage temperature control designed for heavy-duty commercial, industrial, and agricultural applications. It features a rugged NEMA 1 steel enclosure and utilizes a liquid-filled coiled sensing bulb attached directly to the case for maximum sensitivity to ambient air temperature changes, remaining unaffected by barometric pressure or altitude.

Features

• Two-stage temperature control with two independent SPDT switches
• Liquid-filled coiled sensing bulb for accurate air temperature measurement
• Dust-protected and corrosion-treated enclosure suitable for harsh environments like farm buildings
• Exposed dial setpoint adjustment for easy temperature modification
• Built-in adjustable cutout stop screw to lock high or low temperature settings

Specifications

• Temperature Range: 30°F to 110°F
• Differential: 3.5°F fixed differential per stage
• Switch Action: 2-SPDT (Single-Pole Double-Throw)
• Enclosure Rating: NEMA 1 (gray galvanized steel)
• Electrical Rating: 1 HP at 120/240 VAC; 24 to 277 VAC voltage compatibility
• Sensing Element: Built-in coiled bulb

Applications

• Commercial HVAC space temperature control
• Automatic ventilation or heating control in livestock barns, poultry houses, and milk houses
• Two-speed ventilation fan sequencing based on temperature rise
• Combination heating and cooling systems with automatic changeover
• Industrial refrigeration and general-purpose operating temperature control