Overvoltage or Undervoltage Detected

What does 8496 mean?

The Safety PLC has detected an abnormal power supply condition, specifically either an overvoltage or undervoltage. This issue can stem from an unstable power source, incorrect wiring, or a fault within the PLC's internal power conditioning circuitry. Prolonged exposure to incorrect voltage can damage the PLC or cause erratic behavior, compromising safety.

• Faulty or improperly regulated 24VDC power supply unit feeding the safety PLC, providing voltage outside the specified range (e.g., 21.6V-26.4V).
• Loose or corroded power supply wiring to the safety PLC's L+ and M terminals, causing significant voltage drop (undervoltage).
• High current draw from other devices on the same 24VDC bus causing the voltage to sag below the PLC's minimum threshold.
• External electrical disturbances (e.g., motor starting, welding equipment) causing temporary voltage spikes (overvoltage) or dips (undervoltage).
• Incorrect fusing or circuit breaker tripping intermittently, leading to momentary power loss or reduced voltage.

Click steps to track your progress.

1. 1

   Measure the 24VDC power supply voltage directly at the safety PLC's L+ and M input terminals using a calibrated multimeter, checking for overvoltage (e.g., >26.4V) or undervoltage (e.g., <21.6V).

2. 2

   Inspect all power cabling, including terminal blocks and wire connections, leading to the safety PLC for loose connections, corrosion, or damage.

3. 3

   Verify the output voltage of the 24VDC power supply unit under load and ensure it is stable and within its specified operating range.

4. 4

   Isolate the safety PLC by temporarily disconnecting other loads from the 24VDC power supply to check if the voltage stabilizes.

5. 5

   Check for external sources of electrical interference or voltage fluctuations on the main supply grid that might be affecting the 24VDC power supply.

6. 6

   Replace the 24VDC power supply unit if it fails to maintain stable voltage within the safety PLC's specified operating range.