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Diagnostics and Troubleshooting
UNT-SVX07J-EN
149
Outdoor Air Dampers with UC400-B Controller
Table 91.
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
.
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 92. 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,” p. 118
.)
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.
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