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Diagnostics and Troubleshooting
Table 60. Outdoor air damper remains open (continued)
Explanation
Probable Cause
The controller opens and closes the outdoor air damper based on the controller occupancy mode and fan
Normal operation
status. Normally, the outdoor air damper is open during occupied mode when the fan is running and
closed during unoccupied mode. (Refer to the section,
The controller must be properly configured based on the actual installed end devices and application. If
Unit configuration
the unit configuration does not match the actual end device, the outdoor air damper may not work
correctly.
ECM Motors
WARNING
Hazardous Voltage w/Capacitors!
Failure to disconnect power and discharge capacitors
before servicing could result in death or serious
injury.
Disconnect all electric power, including remote
disconnects and discharge all motor start/run
capacitors before servicing. Follow proper lockout/
tagout procedures to ensure the power cannot be
inadvertently energized. For variable frequency drives
or other energy storing components provided by
Trane or others, refer to the appropriate
manufacturer's literature for allowable waiting periods
for discharge of capacitors. Verify with a CAT III or IV
voltmeter rated per NFPA 70E that all capacitors have
discharged.
An electronically commutated motors (ECM) is a closed
loop system that has equipment protections and envelope
enforcements. Do not assume that the motor has failed
without first consulting the VelociTach engine status/
diagnostics screen. In many cases, the engine shuts down
the motor operation and locks it out to prevent equipment
damage.
Electric heat operation and changeover coil control on
CSTI units are coordinated by the VelociTach motor control
board.
The mini-access lid on the front of the main control panel lid
has the VelociTach troubleshooting/setup guide affixed to
the back of the lid. This guide is unit-specific and should be
consulted before determining the disposition of a unit.
The adapter boards contain high voltage. Configuration
adjustments to the VelociTach board should be made
through the SMALLER of the two low-voltage lids on the
front of the control panel, through the low-voltage
insulation/shielding.
138
"Modulating Outdoor/Return Air Damper," p.
WARNING
Hazardous Voltage!
Failure to disconnect power before servicing could
result in death or serious injury.
Disconnect all electric power, including remote
disconnects before servicing. Follow proper lockout/
tagout procedures to ensure the power can not be
inadvertently energized. Verify that no power is
present with a voltmeter.
General Information
The VelociTach motor control board oversees and monitors
all motor operations and changes to speed resulting from:
•
Direct fan speed requests
–
Customer fan speed switches
–
Thermostat fan speed, On or 0–10V requests
–
Automatic fan request from DDC controllers
•
Indirect fan speed requests
Electric heat requests will bring the fan to the
proper speed.
•
Conflicting fan speed requests
If two or more commands are received (direct or
indirect), the fan will honor the higher speed
requested.
Note: In some cases, indirect requests will result in fan
behavior change regardless of whether the end-
device fails to actuate (due to device failure, or
safety/down-stream lockouts).
The VelociTach motor control board also coordinates the
operation of electric heat, electric/hydronic heat lockouts,
and CSTI changeover coil operation.
Troubleshooting Tips
•
VelociTach motor control board configuration must
perfectly match the factory-supplied ECM. Refer to for
configuration of the motor control board
"Adjustments," p.
92.
•
The VelociTach motor control board will display
troubleshooting information, and contains dual
tachometers to aid in performance verification.
•
Under normal circumstances, the VelociTach display
will display the operational status of the motors and
electric heat circuit/sensors, however, a malfunction will
110.)
BCX-SVX002A-EN
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