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Chapter 7 Troubleshooting
66 CNT-SVX07C-EN
Requested mode off You can communicate a desired operating mode (such as off, heat, and cool) to the con-
troller. If off is communicated to the controller, the unit shuts off the compressor or elec-
tric heat.
Freeze avoidance When the fan is off with no demand for capacity (0%) and the outdoor air temperature is
below the freeze avoidance setpoint, the controller disables compressors and electric
heat outputs (100%) to prevent coil freezing. This includes unoccupied mode when there
is no call for capacity or any other time the fan is off.
Table 21. 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
Tracer ZN521 controller to operate normally, you must apply an input voltage of 24 Vac. If
the green LED is off continuously, the controller does not have sufficient power or has
failed.
Diagnostic present Several diagnostics affect outdoor air damper operation. For information about these
diagnostics, see Table 16 on page 59.
Normal
operation
The controller opens and closes the outdoor air damper based on the controller’s occu-
pancy 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.
Manual output test The controller includes a manual output test sequence you can use to verify output oper-
ation and associated output wiring. However, based on the current step in the test
sequence, the outdoor air damper may not be open. Refer to the “Manual output test” on
page 52.
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 You can communicate a desired operating mode (such as off, heat, or cool) to the control-
ler. If off is communicated to the controller, the unit closes the outdoor air damper.
Table 22. 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.
Table 20. DX or electric heat does not energize (Continued)
Probable cause Explanation