Application

Sequence of Operation
Calibration
7
Siemens Industry, Inc. Application Note, App 2030 140-1021
2015-08-07
Example
If UNOCC FLOW = 250 cfm, and if OCC FLOW = 1000 cfm
then, in unoccupied mode the FLOW STPT
= (250 cfm ÷ 1000 cfm) × 100% flow
= 0.25 × 100% flow
= 25% flow
Since 250 cfm is 25% of 1000 cfm, the flow setpoint in unoccupied mode is 25%.
UNOCC FLOW can be set less than or equal to, but not greater than OCC FLOW.
Calibration
Calibration of the controller’s internal air velocity sensor(s) is periodically required to
maintain accurate air velocity readings. CAL SETUP is set with the desired calibration
option during controller startup.
Depending on the value of CAL SETUP, calibration may be set to take place
automatically or manually. If CAL AIR = YES, calibration is in progress.
 For a controller used without an Autozero Module (CAL MODULE = NO), the
damper is commanded closed to get a zero airflow reading during calibration.
 For a controller used with an Autozero Module (CAL MODULE = YES), calibration
occurs without closing the damper.
NOTE:
The first time after startup or initialization, the controller will calibrate the dampers as
if not using Autozero Modules, although the Autozero Modules will be activated. All
subsequent calibrations will use the Autozero Modules only.
At the end of a calibration sequence, CAL AIR automatically returns to NO. A status of
NO indicates that the controller is not in a calibration sequence.
Fail Mode Operation
If the air velocity sensor fails, the controller determines the status of FAIL MODE and
positions the damper accordingly. If FAIL MODE = OPEN and the velocity sensor fails,
the damper will open. If FAIL MODE = CLOSED (the default) and the velocity sensor
fails, the damper will close.
If the room temperature sensor fails, the controller holds the last known temperature
value.