user manual

UV-SVP01A-EN 57
Troubleshooting
DX/Electric Heat
Outside Air Damper
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 opens the water valves (100%) to prevent coil freezing. This
includes unoccupied mode when there is no call for capacity or any other time the fan is off.
Normal operation The controller opens and closes the valves to meet the unit capacity requirements.
Table 31: Valves stay open
Probable cause Possible Explanation
Table 32: DX or electric output(s) does not energize
Probable cause Possible Explanation
Unit wiring
The wiring between the controller outputs and the end devices must be present and correct for normal
operation.
Unit configuration
The controller must be properly configured based on the actual installed end devices and application.
When the unit configuration does not match the actual end devices, the unit may not work correctly.
Diagnostic present
A specific list of diagnostics affect compressor and electric heat operation. For more information see,
Tracer™ ZN.520 Unit Controller diagnostics, on page 52 for more information.)
Manual output test
The controller includes a manual output test sequence you can use to verify output operation and
associated output wiring. However, based on the current step in the test sequence, the DX or electric
outputs may be
OFF. For more information see, Manual Output Test, on page 48 for more information.)
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. This includes
UNOCCUPIED mode when there is no call for capacity or any other time the fan is OFF.
Normal operation The controller energizes the outputs only as needed to meet the unit capacity requirements.
Table 33: Outdoor air damper stays closed
Probable cause Explanation
Unit wiring
The wiring between the controller outputs and the outdoor air damper must be present and correct for
normal damper operation.
Unit configuration
The controller must be properly configured based on the actual installed end devices and application.
When the unit configuration does not match the actual end devices, the damper may not work
correctly.
Random-start observed
After power-up, the controller always observes a random-start from 5 to 30 seconds. The controller
remains
OFF until the random-start time expires.
Power-up control wait
When power-up control wait is enabled (non-zero time), the controller remains
OFF until one of two
conditions occurs:
1. The controller exits power-up control wait once it receives communicated information.
2. The controller exits power-up control wait once the power-up control wait time expires.
Diagnostic present
A specific list of diagnostics affects outdoor air operation. For more information see, Tracer™ ZN.520
Unit Controller diagnostics, on page 52 for more information.)
Manual output test
The controller includes a manual output test sequence you can use to verify output operation and
associated output wiring. However, based on the current step in the test sequence, the unit damper
may not be open. For more information see, Manual Output Test, on page 48 for more information.)
Fan mode
OFF
When a local fan mode switch (provided on the Trane zone sensor) determines the fan operation, the
OFF position controls the unit OFF and damper to close.