What is calibration sequence followed by a VariTrac III system ?

Issue:

What is calibration sequence followed by a VariTrac III system ?

Resolution:

The calibration sequence performed by a VariTrac is incomplete in The VariTrac Operator Guide VAV-SVU01A-EN (page 11).

https://tranesupport.zendesk.com/hc/en-us/articles/11744522945677-VariTrac-III-CCP-literature

When does calibration occur?
Calibration of a VariTrac bypass system takes place at power-up or a transition from occupied to unoccupied mode. If the VariTrac has no schedules (24 hour operation), calibration occurs approximately once every 7 days.

VariTrac Calibration sequence:<br>
1. All zones perform a self-calibration function (UCM reset).  The position of the damper blades and the zero-flow pressure of the transducer are calibrated for VariTrane VAV boxes.

2. All zone dampers modulate to their maximum-open position.

3. The bypass damper modulates open; with the fan off, the zero static pressure reading is taken.

4. The system fan turns on and the bypass damper is closed. The bypass damper is driven closed for a minimum of 120 seconds. Once the system stabilizes, the reference static pressure reading is read and stored by VariTrac.

5. The bypass damper is released and modulates to maintain the fan static pressure set point.

Note: The calibration sequence can be manually started by pushing the Calibrate Now button available on the operator display or via PC software.

Note: During a transition from the occupied to unoccupied mode, the CCP checks if calibration has occurred within the past 23 hours. If calibration has previously occurred, the previously stored values are used.

 

Other Question/Problem/Cause Statements:

• What is calibration sequence followed by a VariTrac III system ?

Facts:

• VariTrac III Central Control Panel (CCP)

Original wave: case3682