Cause: Encoder Thermal Detected Error comes when the thermal sensor monitoring function has detected a high temperature error on encoder module analog input.

"tHEF" fault in Schneider ATV950 drive indicate "Encoder Thermal Detected" error. This means the encoder's temperature has exceeded its specified operating range, or that there is a thermal issue detected with the encoder itself. This can affect the accuracy and reliability of the feedback provided by the encoder. 

1. Search for a possible cause of overheating.
2. Verify the settings of the monitoring function.