Trane Direct-Fired Indoor and Outdoor Make-Up Air Units, MUA-SVP01A-EN Diagnostics

MUA-SVP01A-EN • Direct-Fired Indoor and Outdoor Units 26
Critical Fault Codes
This section should assist the user in troubleshooting critical fault codes
messages that have been displayed on the local user interface. These faults
require the operator to correct the condition and reset the alarm before normal
unit operation resumes.
FAULT CODE: Low Discharge Temperature
PROBLEM: The controller has detected a low temperature at the fan
outlet and has shut off the unit. See Freezestat section of this manual.
SOLUTION: If burner was operating prior to shutdown (check prior alarm log)
1. Is the outside air (OA Temp) or room air (Room Temp) displayed on the
BACview remote, reading 150°F or more?
–Yes . That sensor circuit or the sensor itself is shorted. Unplug the input
jack from the AdaptAire controller. Did the display ch ange to -40 °F o r le ss?
– No. There is a short in the controller input. Replace the controller.
– Yes. Disconnect the sensor wiring at the sensor. Connect an ohmmeter
to the sensor. If it is shorted replace the sensor. At 77°F the resistance
should be 10K?. See thermistor output curve for other temperatures. If
it is not shorted, there is a short in the wiring between the sensor and
the input plug. Determine cause and rectify. Refer to Appendix II for a
typical 10K? thermistor output curve.
–No. Continue.
2. Is the discharge air temperature (DA Temp), displayed on the BACview
remote, reading -40°F or less?
–Yes . That sensor circuit or the sensor itself is open. Jumper the input for
the sensor. Did the display change to 150°F or more?
– No. There is an open in the controller input. Replace the controller.
– Yes. Disconnect the sensor wiring at the sensor. Connect an ohmmeter
to the sensor. If it is open replace the sensor. At 77°F the resistance
should be 10K?. See thermistor output curve for other temperatures. If
it is not open, there is a break in the wiring between the sensor and the
input plug. Determine cause and rectify.
–No. Continue
3. Reset the alarm. Check and note the DC voltage at output for the gas valve
modulation. Set the Heating Setpoint for 90°F . S et the MAX DAT and MIN DAT
Setpoints for 130°F. Did the Burner VDC, displayed on the BACview remote,
increase?
–No. Unless the outside air temperature is extremely warm the Burner VDC
should have increased to 7.5VDC or more. Close the manual main gas
Diagnostics