Danfoss · VLT HVAC Basic FC 101
The torque measured by the motor is below the threshold set for no-load conditions, strongly indicating a broken or severely slipping belt in the mechanical system. This results in a loss of power transmission to the driven equipment.
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Visually inspect the drive belt(s) for breakage, severe wear, cracks, or signs of slipping (e.g., rubber dust).
Check the tension of the drive belt(s) using a belt tension meter; adjust to manufacturer specifications.
Inspect the motor coupling and driven equipment coupling for damage, looseness, or sheared pins/keys.
Manually attempt to rotate the driven equipment (if safe) to verify if the motor is still connected to the load.
Verify the no-load torque threshold parameter (e.g., P4-02 or similar) is set appropriately for the application's idle state.
Check for issues like a pump running dry or a fan impeller detaching from its shaft.