Danfoss · VLT HVAC Drive FC 102
The drive has not received a valid control word from the external controller (e.g., PLC via fieldbus) within the expected timeframe. This indicates a communication failure, causing the drive to stop or trip for safety reasons.
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1. Inspect the fieldbus communication cable (e.g., Ethernet, Profibus) for physical damage, loose connections, or incorrect shielding at both the drive and the master controller.
2. Verify the operational status of the fieldbus master (e.g., PLC), checking its diagnostic LEDs and internal diagnostic buffer for communication errors.
3. Confirm that all fieldbus parameters in the drive (e.g., P8-01, Fieldbus Address; P8-02, Baud Rate) precisely match the settings in the master controller.
4. Monitor the drive's fieldbus status (e.g., P8-03, Fieldbus Status Word) and confirm that control words are being received consistently from the master.
5. Increase the drive parameter P8-10 (Control Word Timeout) to a longer duration (e.g., 5-10 seconds) if transient network delays are suspected, after confirming network stability.