I do Ethernet I/P now almost exclusively. The idea that hard wire is somehow “safer” doesn’t fit with my experience. I’ve run into far far more mistakes in hard wiring than I have ever seen in network control. When people were standing next to machinery all the time and interacting with it, hard wire control was fine because if anything went wrong, a human was there to intervene and trained on the complexity and interoperability of the entire system. But those days are gone now, those jobs have been eliminated. So when something goes awry, all that complexity is being handled by the control system anyway and hard wiring just means it takes a long time to find and repair a problem. A properly trained technician can find and fix a network control issue very fast, partly because if properly set up (using managed switches), the network will TELL you right where the problem is. Do you try to find and fix it in a solid state OL relay? No, you swap the bucket out and take it to the bench to diagnose later when you have time.
My old partner (now retired) famously stated to me once in front of our rock plant customer, “If I can’t check it with a Wiggy, it ain’t worth sh*t!”. The end user decided to go with an Ethernet MCC anyway and they love it. The plant has never run more trouble free in its 40 year history.
That said, I also believe in having an HOA switch on each starter, because bump checks are a PITA over network control. Then having the HOAs give people that necessary “warm and fuzzy” feeling of control should the network go down. It’s not likely realistic that you can operate a complex system that way, it’s more of a placebo effect.
