ECM Motors
148
UNT-SVX07E-EN
Outdoor Air Dampers
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. Changeover function on Tracer ZN units can also be
affected by incorrect configuration of the VelociTach motor
control board or improper wiring of terminals to analog
input 1 on the Tracer ZN controller (polarity sensitivity).
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.
Table 92. Outdoor air damper remains closed
Probable Cause
Explanation
Unit wiring
The wiring between the controller outputs and the outdoor air damper must be present and correct for normal
outdoor air damper operation. Refer to applicable wiring diagram.
Failed end device
Check damper actuator to ensure proper operation.
No power to the controller
If the controller does not have power, the outdoor air damper does not operate. For the controller to operate
normally, apply an input voltage of 24 Vac. If the Marquee/Power LED is
OFF
continuously, the controller does not
have sufficient power or has failed.
Diagnostic present
Several diagnostics affect outdoor air damper operation. For detailed information about these diagnostics, refer
to
Table 87, page 145
.
Normal operation
The controller opens and closes the outdoor air damper based on the controller’s occupancy mode and fan status.
Normally, the outdoor air damper is open during occupied mode when the fan is running and closed during
unoccupied mode.
Unit configuration
The controller must be properly configured based on the actual installed end devices and application. If the unit
configuration does not match the actual end device, the outdoor air damper may not work correctly.
Warm-up and cool-down
sequence
The controller includes both a morning warm-up and cool-down sequence to keep the outdoor air damper closed
during the transition from unoccupied to occupied. This is an attempt to bring the space under control as quickly
as possible.
Requested mode off
The user can communicate a desired operating mode (such as
OFF
, heat, or cool) to the controller. If
OFF
is
communicated to the controller, the unit closes the outdoor air damper.
Table 93. Outdoor air damper remains open
Probable Cause
Explanation
Unit wiring
The wiring between the controller outputs and the outdoor air damper must be present and correct for normal
outdoor air damper operation. Refer to applicable wiring diagram.
Failed end device
Check damper actuator to ensure proper operation.
Normal operation
The controller opens and closes the outdoor air damper based on the controller occupancy mode and fan 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,
“Modulating Outdoor/Return Air Damper (UC400),” page 102
.)
Unit configuration
The controller must be properly configured based on the actual installed end devices and application. If the unit
configuration does not match the actual end device, the outdoor air damper may not work correctly.
ECM Motors
Troubleshooting
WARNING
Hazardous Voltage w/Capacitors!
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 an appropriate voltmeter that all
capacitors have discharged. Failure to disconnect
power and discharge capacitors before servicing could
result in death or serious injury.
