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  • P3-16TD2 Output Module Issues

    I have a Productivity 3000 series system with a P3-16TD2 Output module, 16 Point sourcing 24VDC. The module works fine until an E-stop is hit. A contact from an E-stop relay drops power to the module, when the E-stop condition is cleared/reset the ouputs are all fried. Replace the module and everything works until the next E-stop condition. Anyone have any thoughts? The ouput module has 12, 24VDC solenoids connected and a maximum of 4 solenoids can fire at one time. System has been in service for 1.5 years and we have had 4-Estop conditions resulting in 4 modules ruined.


  • #2
    Does the PLC have the outputs turned on when the power is applied after the Estop Reset?

    If so and the power fluctuated from contact bounce, it may oscillate the outputs rapidly and generate a large voltage for a very brief period.
    This may exceed the voltage range on the module.

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    • #3
      Yes, Outputs could be energized when the E-stop is reset but I could put a time delay between the E-stop clearing and the Outputs being re-energized to see if that corrects the problem. That would allow the module time to power up before firing any outputs.

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      • #4
        Just to clarify, when the event occurs with only 4 outputs active after the reset all 32 outputs have failed? What sort of suppression do you have around those DC solenoids?

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        • #5
          No suppresion is being used. All equipment in the panel is rated Class 1 Division 2 and panel is in a Class 1 Div 2 Area. I am unaware of any suppressors that are rated C1D2.

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          • #6
            I dout it is specifically the solenoids opening that is killing the module, as if it were then I woulds think only the channels that had been active at the time of power disconnect would be the ones fried. To me it seems more likely that by suddenly disconnecting power to the module is what is killing it. Whether by a spike in your power itself or something to do with the card having power and suddenly the circuit is broken and it has nowhere for the power to go.

            Is it correct practice to completely disconnect power to the PLC module itself? The machines we have that came with PLCs from the factory do not lose PLC power on an E-Stop. All outputs are forced off sure, but the PLC itself still keeps power.

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            • #7
              Originally posted by dcheser View Post
              Yes, Outputs could be energized when the E-stop is reset but I could put a time delay between the E-stop clearing and the Outputs being re-energized to see if that corrects the problem. That would allow the module time to power up before firing any outputs.
              I'm not an electrician but was under the impression that there needed to be a second action after an e-stop reset.

              What is the reason for cutting power to PLC vs maybe cutting off common to coils and sending E-stop to PLC to interrupt outputs so they can't be re-energized on reset?

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              • #8
                Originally posted by durallymax View Post

                I'm not an electrician but was under the impression that there needed to be a second action after an e-stop reset.

                What is the reason for cutting power to PLC vs maybe cutting off common to coils and sending E-stop to PLC to interrupt outputs so they can't be re-energized on reset?
                Dropping out the commons to the coils would be odd. If I'm understanding what the OP does, they drop out the +24vdc to the +24vdc terminal of the output module (this is how I do it, but with P2K output modules) when an E-stop is invoked.

                I wonder if there are any coil loads (pneumatic valves, motor contactors, relays) on the outputs that don't have suppression? Coil loads can damage solid-state outputs if they don't have suppression.
                Last edited by Ridgeline Mach; 05-12-2018, 06:37 PM.
                If you've done the very best you can, worrying won't make it any better - Walt Disney

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                • #9
                  Originally posted by Ridgeline Mach View Post

                  Dropping out the commons to the coils would be odd. If I'm understanding what the OP does, they drop out the +24vdc to the +24vdc terminal of the output module (this is how I do it, but with P2K output modules) when an E-stop is invoked.

                  I wonder if their are any coil loads (pneumatic valves, motor contactors, relays) on the outputs that don't have suppression? Coil loads can damage solid-state outputs if they don't have suppression.
                  OP mentioned something about class 1div 2 area. Unsure of approriate suppression for c1d2 area

                  Comment



                  • #10
                    Originally posted by kewakl View Post

                    OP mentioned something about class 1div 2 area. Unsure of approriate suppression for c1d2 area
                    I look it up to mean an explosion proof environment? I am unsure how that has anything to do with outputs failing.

                    When I have quoted explosion proof equipment, the enclosures were cast-iron, and all conduits to the enclosure had to be epoxied to isolate it from external devices if there was a fire.

                    What I wonder is, if the module is being damaged when the E-stop is invoked, not from when power is re-applied.
                    If you've done the very best you can, worrying won't make it any better - Walt Disney

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                    • #11
                      Try installing diodes in reverse on the solenoids as close as possible to the solenoid. This will prevent the solenoids current from discharging into the P3s outputs when power is removed.

                      I had similar problem with a click PLC and op to installing a relay output with the reversing diodes. Its now been running for 3 years with no problems.

                      You may want to change out the P3-16TD2 for a P3-16TR relay output module and installing diodes on the solenoids. This should prevent further frying the outputs. Try 1N4150TR diodes to start with. These are 50VDC 4amp diodes.
                      Last edited by LWgreys; 05-12-2018, 11:36 PM.

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                      • #12
                        The module itself is powered through the back plane of the chassis but the outputs require a +24VDC and Common per every 8 outputs. In an E-stop condition we are breaking the +24VDC to the 16 outputs on the module only, not the entire PLC. The system is installed in a Class 1, Division 2 Area. All components in the PLC Panel are rated as Class 1, Division 2 therefore no purge or cast iron enclosure is required. I do not know of any suppressors/diodes rated Class 1, Division 2. They will have to be rated to go in this panel.

                        I am going to try putting a delay timer in to hold any outputs off for 10-seconds after the estop is cleared to see if that fixes the problem. If not I will look into the relay output module that was suggested as long as it is also rated C1D2

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                        • #13
                          The P3-16TR is rated for C1D2 as shown in the document HERE

                          The issue with your module is likely voltage spikes from coils as they are powered off, and are damaging the solid-state outputs. You must suppress the spikes to prevent this. A class 1 division 2 environment has little to do with your module failure. It's like you're complaining that you've got an infection after surgery, and maintain that the hospital was sterile, but ignoring the information we're providing that the instruments used probably did not go thorough an autoclave.
                          If you've done the very best you can, worrying won't make it any better - Walt Disney

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                          • #14
                            ZL-TSD8-24

                            meets your Class and Division requirement, and is meant to suppress some of the voltage spikes you may be seeing.

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                            • #15
                              Use flyback diodes. The module is likely being killed when the estop trips and all of the solenoids turn off at the same time. This is causing large voltage spikes.

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