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Tracer UC 400 Controller
Table 87.
Diagnostics generated by UC4000 controller
Diagnostic
Probable Cause
Invalid or missing value for generic
Generic AIP failure
analog input.
Invalid or missing fan-speed switch
Local fan mode failure
(reverts to default fan speed).
Invalid or missing value for zone
Local setpoint failure
temperature setpoint (reverts to default
setpoint).
1
For detailed information about zone temperature control methods, refer to
Note:
Troubleshooting UC400 Controller
Fans
Table 88. Fan does not energize
Probable Cause
Unit wiring
Failed end device
Normal operation
No power to
the controller
Diagnostic present
Unit configuration
Random start observed
Cycling fan operation/
continuous
Unoccupied operation
Fan mode off
Requested mode off
146
Explanation
The wiring between the controller outputs and the fan relays and contacts must be present and correct for normal
fan operation. Refer to applicable wiring diagram.
The fan motor and relay must be checked to ensure proper operation.
The fan will turn OFF when:
• The controller receives a communicated off signal
• The fan-speed switch is set to OFF if no communicated value is present
• Specific diagnostics are generated
• The default fan speed is set to OFF and the fan is operating in the Auto mode.
If the controller is in unoccupied mode, the fan cycles between OFF and the highest fan speed.
If the controller does not have power, the unit fan does not operate. For the controller to operate normally, it must
have 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 fan operation. For detailed information about these diagnostics, refer to
page
145.
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 fans may not work correctly.
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.
The controller continuously operates the fan when in the occupied, occupied standby, or occupied bypass mode.
When the controller is in the unoccupied mode, the fan is cycled between high speed and OFF with capacity.
Even if the controller is configured for continuous fan operation, the fan normally cycles with capacity during
unoccupied mode. While unoccupied, the fan cycles ON or OFF with heating/cooling to provide varying amounts
of heating or cooling to the space.
If a local fan mode switch determines the fan operation, the OFF position controls the fan to off.
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 controls the fan to off. There is no heating or cooling.
Consequences
• Fan Unaffected
• Valves Unaffected
• Outdoor air damper Unaffected
• DX cooling/electric heat Unaffected
• Fan Unaffected
• Valves Unaffected
• Outdoor air damper Unaffected
• DX cooling/electric heat Unaffected
• Fan Unaffected
• Valves Unaffected
• Outdoor air damper Unaffected
• DX cooling/electric heat Unaffected
"Zone Temperature Control," page 115
Diagnostic Type
Informational
Automatic
Automatic
Table 87,
UNT-SVX07E-EN
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