Product Overview:
Reliable temperature regulation is essential for HVAC systems that require staged control across a defined operating range. The Johnson Controls A28KA-1 2-Stage Temperature Control is an OEM replacement part designed for compatible temperature control applications. It operates across a range of 0°F to 150°F and features two single-pole, double-throw (SPDT) outputs for switching in two-stage control systems. Its 10-foot capillary tube and remote bulb sensor support temperature sensing away from the controller.
Component Operation:
The A28KA-1 uses a remote bulb sensor connected through a 10-foot capillary tube to detect temperature at a selected sensing location. The temperature response is conveyed to the control mechanism, which operates the switching outputs as conditions reach the configured control points.
Two-Stage Switching:
The two SPDT outputs support switching functions in two-stage temperature control applications. This configuration allows the controller to manage separate control stages according to the system's temperature requirements.
Replacement Guidelines:
Replace the Johnson Controls A28KA-1 temperature control when either SPDT output no longer switches reliably or the controller fails to respond consistently to temperature changes detected by the remote bulb sensor. Select a replacement that retains the 0°F to 150°F operating range, two-stage switching, dual SPDT outputs, and 10-foot capillary sensing arrangement.
Common Failure Symptoms:
- Temperature control does not respond consistently to changes detected by the remote bulb sensor.
- One or both SPDT switching outputs fail to operate at their configured temperature points.
- The two control stages switch intermittently or fail to respond as intended.
- Temperature regulation becomes inconsistent across the controller's operating range.
Equipment Compatibility:
The Johnson Controls A28KA-1 is intended for compatible HVAC and other temperature control applications requiring two-stage switching. Check the existing system's temperature range, control stages, switching requirements, and remote sensing arrangement to determine suitability.
Technical Specifications:
Brand: Johnson Controls
Part Number: A28KA-1
Product: 2-Stage Temperature Control
Switch Configuration: 2 SPDT
Temperature Range: 0°F to 150°F
Capillary Length: 10 ft
Sensing Arrangement: Remote bulb sensor with capillary tube
Enclosure Protection: Water/dust tight
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