Johnson Controls A28AK-1 2-SPDT Flange Mounted Duct Temperature 30°F/110°F Differential 2F

The Johnson Controls A28AK-1 is a flange two-stage duct thermostat that is applied for the control of temperature of HVAC systems. It has a remote bulb sensor that measures air temperature within a duct and operates two distinct switches (SPDT) according to set parameters. When the air temperature goes higher than the set point, which can be set between 30°F and 110°F, the A28AK-1 initiates the first stage, which is usually a cooling system. If the difference is another level higher, say 2 degrees in this case, the second stage may include other cooling, or an alarm. These two operations assist in the regulation of temperature in addition to the use of a timer that assists avoids constant turning on and off of the HVAC units.