Pilz PNOZ XV3P safety relay

Check the voltage of the two channels in the input circuit: When the safety switch is closed, S11-S12 should conduct (close to 0V voltage drop), and S21-S22 should do the same. If using dual channel with cross short circuit detection, it is also necessary to check the S31-S32 connections.

If all wiring is correct, it may be an internal fault, replace the module.

7.2 Fault phenomenon: After the input is disconnected, the instantaneous contact opens normally, but the delayed contact does not open or opens very slowly

Possible reasons:

The delay setting knob was mistakenly turned to the "0" or infinite position.

Delay circuit capacitor aging (rare, but may occur after years of use).

Excessive load current leads to contact fusion welding, causing the delayed contact to still adhere when it should be opened.

troubleshoot

Check the knob scale and confirm the set value. If the knob is damaged, use a screwdriver to readjust and observe if the delay changes.

After the input is disconnected, use a multimeter to measure the resistance across the delay contacts 47-48: the strain becomes infinite after the expected opening time. If it is still conductive (<1 Ω), the contact has been welded. Replace the module and check if the external load is short circuited or if the suppression circuit is malfunctioning.

Refer to the manual for delay accuracy (-15%/+15%+50ms). If the actual measured delay deviates from the set value beyond this range and the set error is excluded, the module may malfunction.

7.3 Fault phenomenon: POWER LED off or flashing

Reason:

Power loss or low/high voltage.

Power surge causes internal fuses to burn out (rarely).

handle:

Measure the voltage of A1-A2. If the voltage is 0, check the higher-level circuit breaker, fuse, and wiring.

If the voltage is normal but the LED still goes out, it may be due to internal damage to the module. Try turning off the power for 1 minute and then turning it back on. If it still doesn't light up, replace the module.

7.4 Fault phenomenon: After the input circuit is closed, the safety contact briefly closes and then immediately disconnects (self trips)

Possible reasons:

There is loose wiring or contact jitter in the input circuit.

The cross short circuit detection function is triggered (for example, there is leakage resistance between two channels).

The feedback loop is briefly interrupted during the startup process.

troubleshoot

Quickly record the input channel voltage using an oscilloscope or multimeter. If interruptions are found in S11-S12 or S21-S22, check the emergency stop button contacts or wiring terminals.

If using dual channel cross short circuit detection, check the insulation resistance between S22-S32 (should be>100k Ω). If there is low resistance (such as water ingress into the cable), the module will detect a "suspected jumper short circuit" and lock it.

Check if there is an instantaneous open circuit caused by vibration in the Y39-Y40 circuit.

7.5 Fault phenomenon: Unable to start after pressing the reset button in the monitored startup mode

Possible reasons:

The input circuit has not been closed yet.

After the input circuit is closed, there is no waiting period of 300ms.

The reset pulse width is less than 30ms (e.g. hand press time is too short).

The resistance of the S13-S14 connection line is too high.

verification:

Ensure that the input circuit is closed and stable (CH.1/CH.2 LED should be on). If not, please handle the input circuit first.

Press the reset button for at least 0.5 seconds (>30ms), wait for a moment (up to 700ms switch on delay), and see if the output is engaged.

Use a multimeter to monitor the resistance of S13-S14 when pressed, which should be close to 0 Ω.

7.6 Grounding Fault Detection and Recovery

PNOZ XV3P can detect short circuits to ground in input circuits or startup circuits. When a ground fault occurs locally, the module will shut down the output (safety contacts open), the POWER LED may turn off or the ERR indicator may be displayed (the manual does not specify a separate ERR light, but it is indicated by the POWER turning off). Recovery steps:

Eliminate grounding faults (use an insulation resistance tester to find the grounding point).

Disconnect the power for about 1 minute (reset the internal protection circuit).

Re power on, if the fault has been resolved, the module should return to normal.

Regular Inspection and Maintenance Plan

According to EN ISO 13849-1, safety functions must be regularly tested to confirm proper functioning:

Frequency of required safety level inspection

PL e/SIL 3 at least once a month

PL d/SIL 2 at least once a year

Inspection steps (applicable to PNOZ XV3P):

Trigger the input circuit (such as pressing the emergency stop button or opening the safety door).

Confirm that the load corresponding to the instantaneous safety contact stops, and the load corresponding to the delay contact stops after the set delay.

Reset the emergency stop and execute the startup program (such as pressing the reset button).

Confirm that all loads are powered on again.

If it cannot be restarted during the reset process, it indicates that a fault has been detected internally or externally (such as contact welding or abnormal feedback loop), and the above-mentioned troubleshooting should be carried out.