Description
The Johnson Controls A28AA-4 is a robust two-stage temperature control designed for demanding commercial and industrial HVAC applications. Featuring dual SPDT (Single Pole Double Throw) switch action, this controller delivers precise, sequential staging of heating or cooling equipment to optimize system efficiency and maintain tight temperature control.
Key Features
- Two-stage control with 2 SPDT switch action for sequential equipment staging
- Wide voltage compatibility: 120/208/240/277 VAC
- Setpoint range of 30°F to 110°F for versatile application coverage
- 3½° differential per stage for accurate and stable switching
- 3° fixed differential between stages to prevent simultaneous stage activation
- 1 3/8″ x 2 1/4″ coiled bulb sensing element for responsive temperature detection
- Convertible design for flexible field configuration
Specifications
- SKU: A28AA-4
- Brand: Johnson Controls
- Switch Action: 2 SPDT (Two Stage)
- Voltage: 120/208/240/277 VAC
- Setpoint Range: 30°F to 110°F
- Differential Per Stage: 3½°F
- Fixed Differential Between Stages: 3°F
- Bulb Type: Coiled, 1 3/8″ x 2 1/4″
- Configuration: Convertible
Applications
- Commercial HVAC systems requiring two-stage heating or cooling control
- Industrial process temperature management
- Refrigeration and cold storage applications within the 30–110°F range
- Multi-voltage electrical systems (120V, 208V, 240V, or 277V)
The A28AA-4’s convertible design and broad voltage range make it a highly adaptable solution for contractors and facilities engineers. The coiled bulb sensing element provides fast, accurate temperature response, while the fixed 3° differential between stages ensures smooth, efficient transitions without short-cycling. Trust Johnson Controls engineering for reliable, long-lasting performance in your HVAC control applications.
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