60 VAV-SVX07B-EN
Troubleshooting
Troubleshooting Procedures
UC400 Controller Failure
In the event the UC400 controller fails, check the following:
• Check for incorrect supply voltage or no voltage. Verify that UC400 is properly grounded
through one leg of transformer or with jumper to ground.
– Check Marquee LED for the following:
– Displays solid green when the UC400 controller is powered and operating normally.
– Displays solid red when the UC400 controller is powered, but represents low power or
a malfunction.
– If marquee LED displays solid red, check incoming power. Measure the power input to
the UC400 controller on XFMR 24 Vac input and .
The supply voltage should be between 20.4 to 27.6 Vac (24 Vac cataloged). However,
voltages at either extreme may result in system instability.
– If no voltage, check up stream of controller to see were voltage has been interrupted.
Refer to the section, “Appendix: Typical Trane Factory Wiring Diagrams,” p. 77.
• Check for short.
– Remove all wires from controller except incoming power.
– Check device using Tracer TU service tool to see if the UC400 controller is operating properly.
If it does operate properly check, inputs/outputs for a short.
– If controller still fails, replace controller.
Note: For Instructions on how to use Tracer TU, refer to the Tracer TU Online Help and to
the Tracer TU Service Tool Getting Started Guide (TTU-SVN02).
• Check for alarms or diagnostics with Tracer TU service tool.
Freeze protection active (ventilation flow
control)
Closed Off Off
Thumbwheel in * position (single star position) Minimum airflow Normal Normal
Thumbwheel in ** position (double star position) Maximum airflow Normal Normal
Normal Normal Normal Normal
(a) If system mode is heat or auto with a warm or hot supply air temperature
(b) When a temperature sensor fails after being valid, the controller generates a diagnostic to indicate the sensor loss condition. The controller automatically
clears the diagnostic once a valid sensor temperature value is present (non-latching diagnostic).
Table 10. Controller Diagnostics (continued)
Diagnostic Air Valve Fan Reheat
WARNING
Live Electrical Components!
During installation, testing, servicing and troubleshooting of this product, it may be necessary
to work with live electrical components. Have a qualified licensed electrician or other
individual who has been properly trained in handling live electrical components perform these
tasks. Failure to follow all electrical safety precautions when exposed to live electrical
components could result in death or serious injury.
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