Trane VAV VV550 LonTalk, Installation & Operation Manual

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VAV-SVP01A-EN 97
Troubleshooting
• Check the tubing for reversal and/or leaks.
• Check the flow ring for plugged holes. Blow out with compressed air if necessary.
3. Wrong unit size downloaded into the VAV VV550 Controller setup menu
• Verify that the actual unit size matches the unit's nameplate.
4. Poor inlet configuration
• Trane recommends 1½-duct diameters of straight duct before the inlet of the box (a 12-inch
box should have 18 inches of straight run duct before the inlet).
5. To determine whether or not the transducer has failed, perform the following steps:
• Check the 24 volts AC supply at TB1-1 24VAC input and TB1-2 on the VAV VV550 Controller
board. Voltage should be between 20 volts AC and 28 volts AC.
• Read the input voltage to the transducer from the VAV VV550 Controller between the green
and red wires on P1 of the VAV VV550 Controller board. The voltage should be between 4.50
volts DC and 5.50 volts DC (5 volts DC cataloged). If no voltage indicated, replace the VAV
VV550 Controller.
• Remove the high and low tubes from the transducer (to simulate no flow). Read the
transducer output voltage on P1 of the VAV VV550 Controller board between the green and
the black wires with a voltmeter. The voltage should be between 0.20 volts DC and 0.30 volts
DC (0.25 volts DC is the null voltage output of the transducer indicating zero flow). If voltage
not available replace transducer
Note: The formula for the Transducer output voltage is 0.25 + 0.75 * <delta P>, where delta P
is the pressure in inches of water column. Delta P can range from 0 to 5 inches of W.C.
• With flow going across the flow ring measure the differential pressure with a magnahelic
and use Transducer output voltage formula to check accuracy of reported value. Read the
transducer output voltage between the green and the black wires. The measured value
should correspond to the value given in the transducer output formula. If transducer is off
by ± 5%, replace transducer.
Figure 57. Sensor signal vs. airflow delivery
0.01
0.1
1
5
10 100 1,000 10,000
C fm
Flow S
ens
or
DP
(
In
. w
g
)
4 "
1 2 " 1 0 " 8 " 6 " 5 " 1 4 "1 6 "