Trane VUV Installation, Operation And Maintenance Manual page 113

DX Coils or Electric Heat with UC400-B/
Symbio™ 400-B Controller
Table 64. DX or electric heat does not energize
Probable Cause
Unit wiring
Failed end device
No power to the controller
Diagnostic present
Normal operation
Unit configuration
Requested mode off
Freeze avoidance
Outdoor Air Dampers with UC400-B/
Symbio™ 400-B Controller
Table 65. Outdoor air damper remains closed
Probable Cause
Unit wiring
Failed end device
No power to the controller
Diagnostic present
Normal operation
Unit configuration
Warm-up and cool-down sequence
Requested mode off
Table 66. Outdoor air damper remains open
Probable Cause
Unit wiring
Failed end device
Normal operation
Unit configuration
UV-SVX005G-EN
Explanation
The wiring between the controller outputs and the end devices must be present and correct for normal operation. Refer to applicable
wiring diagram.
Check the control contactors or the electric heat element, including any auxiliary safety interlocks, to ensure proper operation.
If the controller does not have power, heat outputs do 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.
Several diagnostics affect DX and electric heat operation. For detailed information about these diagnostics, refer to
p. 111.
The controller controls compressor or electric heat outputs as needed to meet the unit capacity requirements.
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, DX or electric heat may not operate correctly.
The user can communicate a desired operating mode (such as OFF, heat, and cool) to the controller. If OFF is communicated to
the controller, the unit shuts off the compressor or electric heat.
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.
Explanation
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.
Check damper actuator to ensure proper operation.
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.
Several diagnostics affect outdoor air damper operation. For detailed information about these diagnostics, refer to
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.
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.
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.
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.
Explanation
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.
Check damper actuator to ensure proper 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," p.
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.
Diagnostics and Troubleshooting
86.)
Table 60,
Table 60, p. 111.
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