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  • #1

    Cat 5e cable fire

    I am a volunteer for a NFP sporting the PC's, network, etc. Today I got a e-mail saying that one of our infrequently used PC's could not get online or connect to the network/server. I checked the patch cable, tried a new one and check the NIC settings. Nothing. I check the switch and that drop was dead. Again tried a new patch cable. Nothing.

    I get a ladder and start to follow the cable. I found a small portion of the cable, about 1", had burned to a crisp. No other wires were damaged, no electrical or other wires were near it. No sign of any other damage.

    Anyone seen this happen before?
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  • #2
    Huh. Sounds like a short in the wire. You're lucky it didn't catch the building on fire.
    The Rich keep getting richer because they keep doing what it was that made them rich. Ditto the Poor.
    "Hy kan tell dey is schmot qvestions, dey is makink my head hurt."
    Hoc spatio locantur.

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    • #3
      I am assuming its the plenum cable in the ceiling or wall your talking about. If they used plenum rated cable like they are supposed to, it would be somewhat fire resistant. Most likely it was being burned by something else in the ceiling. The act of tracing the cable most likely moved it off the heat source.

      I have seen shorted out cat 5, but never cat five that has caught on fire.

      Comment

      • #4
        Quoth Daskinor View Post
        I am assuming its the plenum cable in the ceiling or wall your talking about. If they used plenum rated cable like they are supposed to, it would be somewhat fire resistant. Most likely it was being burned by something else in the ceiling. The act of tracing the cable most likely moved it off the heat source.

        I have seen shorted out cat 5, but never cat five that has caught on fire.
        The only thing it could have touched was insulation or the top of a ceiling tile. Their was literally nothing else near the burn spot.

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        • #5
          did the outer insulation of the cat-5 feel stiff, and if bent or folded it would discolor to white? Or was it rubbery like the insulation of a patch cable?

          Also did this cable support PoE? Or connected to a PoE switch?

          Comment

          • #6
            i don't usually see cat 5 burn itself up even when shorted out and energized. and i've handled it energized too

            though, coming from the main line... *that* will give you a jolt, but not if it's just between a switch and computer

            so, going to have to re-run the whole line or just cheat and toss in a splice?

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            • #7
              Quoth Daskinor View Post
              did the outer insulation of the cat-5 feel stiff, and if bent or folded it would discolor to white? Or was it rubbery like the insulation of a patch cable?

              Also did this cable support PoE? Or connected to a PoE switch?
              No PoE or PoE switch. The section burnt was burnt to a crisp, you could see bare wire in a spot.

              Comment

              • #8
                Its just odd. I would still bet money it was some external source. Any melting would of exposed the wires, eventually making them short out. And when that happens the switch and nic card general error out and turn off the port. Even if it doesn't the voltage is still so low.

                Was it sitting on top of a lighting element?

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                • #9
                  Quoth Daskinor View Post
                  Its just odd. I would still bet money it was some external source. Any melting would of exposed the wires, eventually making them short out. And when that happens the switch and nic card general error out and turn off the port. Even if it doesn't the voltage is still so low.

                  Was it sitting on top of a lighting element?
                  The nearest light was two full tiles away. It was in a loose bundle of about 6 cat5 wires. The only other electrical thing near it was a metal conduit about 3 feet away. Other than that it could only touch fiberglass insulation, a ceiling tile or another cat5 wire.

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                  • #10
                    That's absolutely bizarre. I'm certain that normal Ethernet transceivers are capable of surviving a cable short, and that the voltages and currents are too low to cause damage.

                    Which leaves the possibility that someone attached a non-standard device to the port.

                    Comment

                    • #11
                      Quoth mattm04 View Post
                      No PoE or PoE switch. The section burnt was burnt to a crisp, you could see bare wire in a spot.
                      Ok, that is wierd. I was assuming a powered port. Anybody been up there with a heat gun recently? The only other thing I can think of is somehow electricity well over the rating got introduced to the cable. I'd expect to see other evidence of it though.
                      The Rich keep getting richer because they keep doing what it was that made them rich. Ditto the Poor.
                      "Hy kan tell dey is schmot qvestions, dey is makink my head hurt."
                      Hoc spatio locantur.

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                      • #12
                        Ok I need to see a picture of the cable. That is so fricken odd, and I am curious as hell.

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                        • #13
                          I will post a picture later.

                          I asked a CIO I know who is a member of said org. to look at the cable. In all his years he has never see that. He asked his co-workers, never seen it. Asked the cable contractor his company uses, none of them have ever seen it.

                          Were special.

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                          • #14
                            Any dead mice or critters up there? Could be a nomnomZAP problem.
                            Otherwise, I'd look at bends. Or creases. Is this in the middle of a cable run, like this?

                            ===========*spot=================

                            or like ========*
                            |
                            |

                            ?

                            Cutenoob
                            In my heart, in my soul, I'm a woman for rock & roll.
                            She's as fast as slugs on barbituates.

                            Comment

                            • #15
                              Quoth Cutenoob View Post
                              Any dead mice or critters up there? Could be a nomnomZAP problem.
                              Otherwise, I'd look at bends. Or creases. Is this in the middle of a cable run, like this?

                              ===========*spot=================

                              or like ========*
                              |
                              |

                              ?

                              Cutenoob
                              No dead critters or evidence of critters. In the middle of a run. If their was bend or crease ic could have very well been removed when it burned.

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