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1k ft trench run electric,fiber,data,voice - how far apart ?

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  • 1k ft trench run electric,fiber,data,voice - how far apart ?

    Greetings:
    I am connecting two buildings in the campus and need to bury power, fiber (62.5/125 multi-mode 6 strands), cat5e 3 cables, cat3 25pair bundle in a single trench. All cables are rated for direct burial. My question is how far away should I keep the electric from the rest of low voltage ? And how best to do it. Are there spacers available that I could use ?

    I will be putting surge protectors at the service entrance for cat5 and cat3. Fiber don't need surge protection

    What is the best way to ground the entire run (electric and low voltage) ? Since these buildings are grounded separately (ie no common ground between them), how do I mitigate the risk of ground loop ?

    Thanks!
    Shaw

  • #2
    Re: 1k ft trench run electric,fiber,data,voice - how far apart ?

    The seperation between electrical and and low voltage data will probably vary according to each cat 5 wire manufacturer but 5" or 6" is pretty common. Could be less if the wires are shielded. I don't think I've seen direct burial cat 5 and not sure why you'd need to ground it since UTP cable is by definition not shielded or grounded unless you're using STP? Is this also a direct run? 1000 ft is too long for cat 5 runs. They should be no more than 328ft (100 meters) without some form of repeater in between.

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    • #3
      Re: 1k ft trench run electric,fiber,data,voice - how far apart ?

      Thanks Velosapien

      We are running security camera's over cat 5e (analog signals). Data is over fiber because of the 100m limit. Cat3 is also voice (analog)

      I did found cat5e direct burial cables. I will check with the manufacturer and make sure 6" gap is ok between low and high voltage


      (a) How to mitigate ground loop. Should I ask the electrician to connect the ground rods of both buildings to a common ground rod approximately in the middle at about 500feet away from each building.

      (b) cat5e is for video application and cat3 is for voice. Should those be grounded or surge protected ?

      -Shaw

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      • #4
        Re: 1k ft trench run electric,fiber,data,voice - how far apart ?

        For the video, this will be constant stream or single-picture at time intervals? It makes a difference in how it's grounded and what kind of interference it'll be susceptible to.

        For the voice lines: Voice carries tip and ring voltage, drastically different from data lines. It has to be properly grounded. The installer should be well-versed in how underground lines are run. If you're not, get someone who is. It has to be separated from the power and data lines by a minimum of 6".

        Your fiber sounds like it's within spec for the run. Keep the fiber runs seperate from power and voice lines by at least 6" or run everything in separate conduits.

        Even if it's ground-contact rated, conduit will save you time and money down the road when someone sticks something in the ground and shorts your cable. It may be required to run conduit for the power lines, regardless. Check your local codes. Go to the town/county office and ask to speak to an inspector about these items. They can give you lots of good ideas on how to do things properly, and who you can go to for professional services.
        I put it all back together better than before. There\'s lots of leftover parts.

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        • #5
          Re: 1k ft trench run electric,fiber,data,voice - how far apart ?

          I've never deal with direct burial cat 5 but did some quick looking around for and can't find anything definitive on what type of cable it is. It looks like there might be both unshielded twisted pair as well as shielded twisted pair. The UTP kind does not require any grounding. There is nothing to ground since it's all rubber insulated aside from the data conductors. The conductors are always fully isolated even at the equipment they end up at. STP is rare here and mostly used in europe but if that's what is used it does need to be grounded. You should be able by to tell by looking at the cables. If they have no metal foil around any of the cunductors it's not STP. EDIT: looks like much of this might not even matter since using the cable for other applications can change everything.

          Since you're using the cat 5 for video camera analog signals that changes the game. I think in this case you will need to contact both the cable and camera manufacturer to get the specifications. Standard cable specifications only apply to the cable being used for normal digital data transmission. While Cat 5can be used for a lot more, the specs can change completely depending on the application, in many cases the runs actually have to be much shorter so you really should double check that.

          I honestly don't really know the answer to the ground loop question but I would say if you are in fact using STP type grounding it at just on of the ends should be enough?
          Last edited by Velosapien; 09-24-2008, 09:09 AM.

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          • #6
            Re: 1k ft trench run electric,fiber,data,voice - how far apart ?

            http://www.muxlab.com/products/ve_cc...ach_balun.html

            I found this looking around. Enables cctv up to 5000 feet over cat 5 and blocks grounding loops.

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            • #7
              Re: 1k ft trench run electric,fiber,data,voice - how far apart ?

              VASandy,
              Video will be constant stream


              Velosapien,
              Cat5e is UTP,

              I will check with the camera dvr manufacturer on the muxlab product info you sent.
              http://www.muxlab.com/products/ve_cc...ach_balun.html

              Thank you VASandy/Velosapien

              On the grounding, Should I ask the electrician to connect the ground rods of both buildings to a common ground rod approximately in the middle at about 500feet away from each building OR should I tell him to follow TIA/EIA 607 and to run grounding between the comm closets in both buildings


              -Shaw

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              • #8
                Re: 1k ft trench run electric,fiber,data,voice - how far apart ?

                1000 ft is ok for video over cat5 with decent baluns. Don't need to ground anything or use STP. If possible, keep data and video at least 12" from power for such a long run. I'm a structured wiring tech BTW.

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