The AHU has mixed air dampers, a heating coil, and a cooling coil.

The heating coil alone has a 5 second time constant. The cooling coil alone has a 20 second time constant. The supply air temperature sensor time constant is 30 seconds. The damper actuator stroke time is 30 seconds. Therefore, the damper time constant is:

Heating coil time constant:        5   seconds

Cooling coil time constant:    20

Supply air temp. sensor:        30

Damper actuator:                     30

Total                                            85    seconds