Trane Tracer UC400 - Page 56

56 VAV-SVX07F-EN
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 cycl
ing power to un
it. 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 po
int.
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 UC400 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 calibratio
n process to simulate this.
e. Select the Zero Air and Water Valve Start b
utton
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 multi-state value 2,
air flow override, to Air Valve
Maximum Setpoint, from the Multi-state 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 bal
ancin
g work. For details, refer to the
Tracer TU Online Help.
h. Check to see if flow has been established. If flow
is no
t 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
an
d compare with the delta pressure (DP) chart located on
the VAV box. (See Figure 8, p. 57.)
Note: The chart shown in Figure 8 is inten
ded 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.