PID Feedback Loss

What does FBL mean?

This fault occurs when PID Feedback Loss Detection is enabled (b5-12=2) and the PID feedback signal drops below the defined level (b5-13) for a specified time (b5-14). It signifies that the PID feedback source (e.g., transducer, sensor, building automation signal) is either incorrectly installed, malfunctioning, or disconnected. Loss of PID feedback means the Drive cannot maintain accurate process control, potentially causing system instability.

• Broken wire or loose connection in the PID feedback sensor circuit (e.g., pressure transducer, flow meter).
• PID feedback sensor failure or malfunction, providing no output signal.
• Incorrect scaling or wiring of the PID feedback input (A2-01, H3-01 to H3-04) to the Drive.
• PID feedback loss detection level (b5-13) set too high, triggering prematurely during normal operation.
• Temporary feedback interruption (e.g., air bubble in pressure line) exceeding the allowed time (b5-14).

Click steps to track your progress.

1. 1

   1. Power down the Drive and verify the PID feedback sensor wiring connections at the Drive's analog input terminals (A1, A2, etc.) and at the sensor itself.

2. 2

   2. Using a multimeter, measure the output signal from the PID feedback sensor directly (e.g., 4-20mA, 0-10V) to confirm it is operational.

3. 3

   3. Check parameters H3-01 to H3-04 (Analog Input Scaling) to ensure they are correctly configured for the feedback sensor's range and type.

4. 4

   4. Adjust parameter b5-13 (PID Feedback Loss Detection Level) to a lower, more appropriate threshold if the sensor's minimum normal operating output is higher than the current setting.

5. 5

   5. Verify parameter b5-14 (PID Feedback Loss Detection Time) is set with sufficient delay to account for normal process fluctuations without nuisance trips.