Description
The Johnson Controls A28AA-20 is a two-stage controller incorporated into controlling the temperature in HVAC systems. This is a more durable solution consisting of a remote sensor bulb linked to a control device by a 6-foot capillary line. The bulb which is usually made from copper so that it can conduct heat is installed at a place that should have controlled temperatures. The control unit is composed of two single-pole double-throw (2-SPDT) switches that allow the heating and cooling systems to be run separately. It is a variable frequency drive that operates with a 240-volt power supply and is commonly used in HVAC applications such as air handling units, heat pumps, process control, and systems.
