BAS-SVX62E-EN
55
Troubleshooting
Airflow Sensor Failure
In the event that the air valve is reading position (pressure dependent) instead of flow (pressure
independent), or in the event that the measured flow reads incorrectly, (for example, different from
the balance report), check the following:
•
Recalibrate the VAV unit by cycling power to unit. This can also be accomplished with Tracer
TU service tool or Tracer SC.
Important:
Cycling power to the VAV board: The default will automatically cause the unit to
calibrate, but this depends on binary value, auto-calibrate, enable/disable point.
However, following the procedure outlined below will provide a more accurate
calibration. It is only necessary to perform this procedure when experiencing
incorrect flow readings or if the unit reverts to pressure dependent mode despite
being above 5% and below 110% of cataloged flow and performing a normal
calibration and does not correct the problem.
To calibrate:
c. Connect to the UC210 controller with Tracer TU service tool.
d. Turn the central air handler OFF. If this is not possible, Trane recommends pulling the
transducer tubes off during the calibration process to simulate this.
e. Select the Zero Air and Water Valve Start button on the Commissioning page. Tracer TU
service tool will indicate that calibration is taking place. When calibration is complete, the
box will release to AUTO.
f. Drive the box OPEN by overriding multistate value 2, air flow override, to Air Valve Maximum
Setpoint, from the Multistate Status page to ensure that the box is not below 5% of its
cataloged CFM. The controller is accurate in reading flow from 5% to 110% of cataloged CFM.
g. Release the box to AUTO and perform any necessary balancing work. For details, refer to the
Tracer TU Online Help.
h. Check to see if flow has been established. If flow is not established, or inaccurate, proceed
to the following bullet.
•
If the tubing or flow ring is OFF, reversed, plugged, or has a leak:
a. Check with a magnahelic gauge and compare with the delta pressure (DP) chart located on
the VAV box. (See
Note:
The chart shown in Figure 12 is intended for Trane F-Style boxes. Other
manufacturers may have different delta pressure charts.
b. Check the tubing for reversal and/or leaks.
c. Check the flow ring for plugged holes. Blow out with compressed air if necessary.
