Overview:
Low Airflow Diagnostic comes from the Symbio or UC400.
LOCH will display on the blue ECM board
The two are related because the motor RPM is not registering or not meeting the requested RPM
Common Issues:
- Motor has failed
- Wiring to the motor has failed or not connected
- One of the boards sending voltage to the motor has failed
- VFD or Drive has failed to send enough AC voltage to the motor (BCXE units with HP 1.5 or higher)
- Motor is not reaching the commanded RPM (Not enough static or load on the motor)
Troubleshooting Process:
The steps below will walk you through troubleshooting
Step 1
Verify voltage
- See detailed guides that will show motor plug and pin locations
-
LOCH- ECM Troubleshooting Guide – Trane Commercial HVAC Help Center
For Symbio or UC400 you can override the fan in commission mode
Commissioning Mode for UC400 in TU – Trane Commercial HVAC Help Center
Step 2
- Voltage from the ECM board is specific.
- Range is .6 or .7 VDC with no call for the fan and no diagnostics @ 3 and 4 on the motor plug disconnected from the motor
- If you have any other voltage WITH NO CALL FOR THE FAN. Replace the ECM board (Blue board - MOD02616 or latest part number)
Step 3
- With 3 phase units always verify that the motor plug is getting all three legs of power.
See a more detailed guide for Blower coil units:
LOCH - Blower coil Troubleshooting guide – Trane Commercial HVAC Help Center
Step 4
- BCXE units with motor HP over 1.5 will have a 4 wire plug from the drive to the motor that includes 3 hot legs and a ground wire so that you can verify AC voltage to the motor.
- Do not condemn the motor until you have verified insufficient AC voltage to the motor.
- More than likely the drive will fail before the motor will on these units