4 Replies Latest reply on Jan 11, 2018 11:43 AM by dynomightdave

    PLC input to SSR problems

    dynomightdave

      Hi,

       

      We had a PLC discrete output card go bad controlling Crydon  D53TP50CD53TP50C relays

      Is there a known issue for PLC electronic outputs used to control input to SSRs?

      If yes what is the solution.

       

      Thanks,

       

        • Re: PLC input to SSR problems
          PeteB

          Hi Dave.

           

          No, there are no known issues in driving the input of the D53TP type SSR or for that matter any other DC input SSR from a PLC.   The current draw of the 4 to 32 Vdc input on the D53TP is in the range of 24 to 35 ma, so as long as your PLC can handle that level, all should be ok.   Some PLC's that are limited in sourcing 35ma as an output, may be better able to sink the control current, so that may be a consideration.

           

          Was the input of the SSR damaged also?  Or is the SSR operational after you determined the PLC card was bad?

           

          Regards,

          Pete B.

            • Re: PLC input to SSR problems
              dynomightdave

              Hi Pete,

               

              Thanks for the reply.

              We are at a loss to explain why the PLC card failed and are trying determine if there is a problem between the card and the SSRs'.

              Our plc card is rated higher than the SSR and should carry the 35ma without problem.

              5 of 30 outputs on the PLC card failed closed.

              Card is a GE IC694mdl758.

              Card outputs are rated .5A and are operating at 24vdc.

               

              We have not checked the SSR's. 

              When they replace the PLC card I will have them check that the SSR's are functioning.

              We are replacing the PLC card with a different type that has higher output current ratings.

              Maybe this was just a random failure and hopefully there will be not more card faults.

               

              Thanks,

               

              Dave

                • Re: PLC input to SSR problems
                  PeteB

                  Dave,

                   

                  Thanks for the additonal details. yes, the card ratings should be more than enough to handle the SSR inputs.  I'm curious about the 5 of the 30 channels on your card that failed.  Were the 5 connected to 5 SSR's?

                   

                  Pete B.

                    • Re: PLC input to SSR problems
                      dynomightdave

                      Pete,

                       

                      Yes, all 5 channels are connected to d53tp50c.

                      It is an electric boiler with 30 heating elements, each element can be turned on or off with an SSR.

                      The plc controls the 30 heating elements thru the SSR's based on power availability.

                      So we have a total of 30 SSR controlled by the plc outputs.

                      Whatever the reason for the output failures, it is strange that only 5 of the 30 failed.