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Grounding Ethernet Cable on a Ship?

Posted by Cliff on from the dealing-with-a-literal-floating-ground dept.

wrschaeffer asks: "On a ship (a vessel at sea) where a floating ground exists, we are running shielded Ethernet cable to connect between 5 and 10 PC in our LAN. We are unsure on the grounding requirement. ABS (American Bureau of Shipping) has no requirements concerning grounding of Ethernet cable (just smoke and waterproof standards). We have many possibilities: ground one end; ground every end; ground every end and install a isolation transformer at the punch-down block; or don't ground any end. What should we do?"

2 of 58 comments (clear)

  1. Ground one end by jcwren · · Score: 5, Informative

    I would only ground one end, and the end at the hub, since that would be the most common point of the network.

    But this raises the question: Why are you using shielded ethernet? Ethernet is differential, and thus pretty immune to common mode noise.

    I've had 25m ethernet cables draped across running engines (test equipment) with HEI ignition, and not experienced any problems (I can't say that I checked the error counters very often, but in high speed data collections, I wasn't seeing any unexpected decreased throughput).

    In addition, I live on a houstboat, and I have ethernet run in the same conduits as AC power carring 5 to 15 amps on 4 different circuits, and don't experience any problems (max cable length is probably 20 meteres)

  2. DoD grounding recommendations by Anonymous Coward · · Score: 5, Informative

    The applicable US DoD standard is MIL-STD-1310G - "Shipboard Bonding, Grounding, and Other Techniques for Electromagnetic Compatibility and Safety". I'm not sure if that document specifically addresses Ethernet, but one of the illustrations should describe how to ground some differential twisted-pair data network. You can get MIL-STD documents from DAPS.