Shielded Ethernet to Cmore

[allukes]

I have a Cmore in a remote enclosure connected via conduit. Inside the conduit I am running 24V control wiring (1 inductive with supression). Its a 25 ft run and planning to use a shielded ethernet cable. On one end, I have the Stride switch, which I am using for a GND pt for the shield. However, at the CMORE side, the shield from the Ethernet cable gets connected internally to the (-) side of the power supply for the display. It is using a separate PS, only used for the Display and a High Speed Counter module and will not be tied to equipment Gnd. However, using the shielded cable, the display will tie it to Gnd at the display end . Will the shield be effective? Is this a good practice or should I isolate the end of the shielded cable at the display?

[KPrice]

allukes, We have done a project with a very similar configuration. I am confused when you say "at the CMORE side, the shield from the Ethernet cable gets connected internally to the (-) side of the power supply for the display". On my C-more (EA7-S6C), I do not see any connection that would allow the Ethernet cable shield to connect to the (-) side. There is metallic trim around the Ethernet port, but it does not have any continuity to ground or (-). So I believe the Ethernet cable shield at the C-more would be effectively isolated. Do the different C-more panels have different port configurations?

[allukes]

I just pulled a new one out of the box EA7-T6CL, the new model. I just ohmed it out.


The Ethernet, USB ports, shields are connected to (-) 24V supply
The serial connector shield is connected to the Equipment Gnd Terminal

I guess they changed things, if mine was like the old ones, I would not worry. Now I am not so sure what to do.

[KPrice]

allukes, my apologies, I am sorry, you are 100% correct. The Ethernet and USB sheilds DO connect to the C-more (-). I don't know how I messed up so. It's times like this I think I should be in food service, or something.

Your question: will the shield be effective in preventing communication problems due to the switching of the 24VDC inductive load? I don't know. Will it cause "problems", but the communication protocol will handle it such that you would not even notice? I don't know. We have a similar configuration, non-shielded Ethernet and DC (non-inductive) inputs in 25ft 3/4 rigid conduit. We have no problems.

My question: are there any other devices that ground the Ethernet cable shield, and because the (-) is connected to the shield, would allow normal C-more operating current to flow thru ground paths, violating the NEC?

[allukes]

The inductive loads are not on that power supply, just sharing conduit with the ethernet cable. I guess if I leave that power supply unbonded at the source, I shouldn't get any current flow through the shield.

[KPrice]

allukes, in the literature for the Stride Ethernet switch: "To prevent ground loops, the cable shield should be tied to the metal connector body at one end of the cable only."

The Stride Ethernet switch connects the metallic connector body to the Chassis GND terminal.

If I used shielded Ethernet cable (with the shield connected at both ends), I would have provided parallel C-more return (-) paths thru ground, on the project I mentioned. I did not use shielded cable on that project, but I will need to pay attention to this in the future. I do not know if the manufactured shielded Ethernet patch cables (from L-com for example) have the shield connected at both ends.

Again, sorry for the goof-up. Thank you for bringing this to my attention.