Boot Project Load Failure (Power Dip)

What does E4-4 mean?

The Safety PLC failed to load its boot project, possibly due to reaching the maximum allowable power dip duration. This suggests an unstable power supply condition prevented the PLC from initializing correctly, compromising system startup.

• Supply voltage dip below the minimum operating threshold (e.g., <20.4V for 24VDC systems) during the PLC's boot-up sequence.
• Excessive capacitance discharge time in the power supply, causing insufficient hold-up time during transients.
• Faulty or undersized 24VDC power supply unit unable to maintain stable voltage under load.
• High impedance in the power cabling from the PSU to the PLC, leading to voltage drop during current surges.
• Incorrectly configured 'Max Power Dip Duration' parameter (e.g., P-MAX_DIP_TIME) in the PLC.

Click steps to track your progress.

1. 1

   1. Measure and log the 24VDC supply voltage at the Safety PLC's power terminals (e.g., X1:1, X1:2) using a power quality analyzer during boot attempts.

2. 2

   2. Increase the hold-up time of the 24VDC power supply by adding an external buffer module or replacing with a larger capacity PSU.

3. 3

   3. Verify that the 'Max Power Dip Duration' parameter (e.g., P-POWERDIP_MAX_TIME) in the PLC configuration is set appropriately for the application.

4. 4

   4. Inspect the cabling from the power supply to the PLC for excessive voltage drop due to thin wires or long runs (measure voltage at both ends).

5. 5

   5. Replace the 24VDC power supply unit if it consistently shows instability or inability to maintain voltage during load transients.