Description
The Johnson Controls A28AA-29 is designed as a two-stage, remote bulb temperature control system for HVAC. It employs a liquid filled sensor bulb, which is connected to the main control unit through an 8 feet capillary tube. The liquid within the unit expands as the temperature increases in the surrounding, thereby closing electrical contacts. This sets in two steps of either heating or cooling depending on the setting of the desired point and the differential. The thermonic couple A28AA-29 works in the range temperature of -30°F to 100°F and is applied for commercial refrigeration and freezer, pool heater and comfort heating systems. Compared to single stage models, its two-stage operation provides a better control of temperature.
