11 2 UNT-SVX07B-EN
Diagnostics
Table 37. Fresh air damper stays closed
Probable Cause Explanation
Normal operation
The controller opens and closes the fresh air damper based on the controller’s occupancy mode and fan status.
Normally, the fresh air damper is open during occupied mode when the fan is running and closed during unoccupied
mode.
Warmup and cooldown The controller includes both a warmup and cooldown sequence to keep the fresh 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 It is possible to communicate the operating mode (such as off, heat, cool) to the controller. When off is communicated
to the controller, the unit closes the fresh air damper.
Manual output test
The controller includes a manual output test sequence that verifies analog and binary output operation and associated
output wiring. However, based on the current step in the test sequence, the fresh air damper may not be open. Refer
to “Manual Output Test,” p. 108.
Diagnostic present A specific list of diagnostics effects fresh air damper operation. For more information, see “Diagnostics,” p. 107.
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 device, the damper may not work correctly.
No power to the controller
If the controller does not have power, the fresh air damper does not operate. For the controller to operate normally,
a 24 Vac input voltage must be applied. When the green LED is off continuously, the controller does not have sufficient
power or has failed.
Unit wiring The wiring between the controller outputs and the fresh air damper must be present and correct for normal damper
operation. Refer to the typical unit wiring diagrams (see “Wiring Diagrams,” p. 126).
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