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  • Rodent protection for PV cables

    Can anyone help with ideas for protecting a rooftop PV array from squirrels or other rodents chewing up PV wiring? Is this a problem?

    Specifically, the USE2 PV cables connecting the modules of an array are exposed, and I know that rodents generally like to chew cable insulation. Has this been an issue with PV cables, and if so what do people do about preventing it?

    One could put the wires between modules in conduit, but the junction boxes on the back of my panels do not have knockouts. Furthermore, to cut knockouts would violate module warrantees, and the MC4 connectors are 1" thick (need >1" ID conduit to fit through). One could also surround the entire array with a hardware cloth apron.

    What do people out there do about this problem, if it is indeed a problem

    Thanks.
    Christo

  • #2
    Yes it is a problem and this is a sure fire solution. Metal conduit raceway. Use RMC or EMT
    MSEE, PE

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    • #3
      Originally posted by Sunking View Post
      Yes it is a problem and this is a sure fire solution. Metal conduit raceway. Use RMC or EMT
      Yes, but what about the lack of knockouts, and the warranty problem?
      Christo

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      • #4
        What lack of knockouts and warranty problem?
        MSEE, PE

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        • #5
          Thanks for the response. As mentioned in my original post, the Kyocera modules have USE2 cables coming out of each junction box, with MC4 connectors on the ends in order to connect them to adjacent modules. The junctions boxes do not have have knockouts to attach conduit to them, and to drill holes to accommodate conduit fittings would violate the module warranty.

          I realize conduit would be the best solution, but there doesn't appear to be an easy way to attach conduit to these boxes. Do you have any suggestions on the best way to proceed?

          Thanks
          Christo

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          • #6
            Originally posted by Christo View Post
            Thanks for the response. As mentioned in my original post, the Kyocera modules have USE2 cables coming out of each junction box, with MC4 connectors on the ends in order to connect them to adjacent modules. The junctions boxes do not have have knockouts to attach conduit to them, and to drill holes to accommodate conduit fittings would violate the module warranty.

            I realize conduit would be the best solution, but there doesn't appear to be an easy way to attach conduit to these boxes. Do you have any suggestions on the best way to proceed?

            Thanks
            You can just have the wires in free air for an inch or two, then enter a conduit with a plastic bushing to prevent the edge of the conduit from chafing the wire. Hopefully the little varmints won't find that exposed section, or if they do they'll be touching something grounded and get a wallop out of it.

            Any other metal enclosure would do as well. For example a piece of aluminum C channel might do as a handy cable tray, with some thin sheet aluminum clamped over the top. If you have a big array, such an arrangement might be easier and cheaper than a lot of conduits.
            Lawrence Lile, PE

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            • #7
              Originally posted by Sunking View Post
              Yes it is a problem and this is a sure fire solution. Metal conduit raceway. Use RMC or EMT
              I'd probably avoid EMT on a roof, it tends to rust because the galvanizing is thin. RMC (Rigid Metal Conduit) is OK but it is kinda hard to work with, and kind of expensive. I'm thinking about using a piece of aluminum C channel as a sort of cable tray, or even getting a section of commercial cable tray. I don't know if that would be less expensive than RMC, but all of the metal I am using under the array is either aluminum or stainless for long-lasting durability.

              Lawrence
              Lawrence Lile, PE

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              • #8
                Rodents

                Thanks for the input. It does sound like aluminum cable tray might be a good solution, and far easier to work with than a bunch of short segments of either EMT or RMC. If you find a good source, let me know.
                Thanks for the ideas.
                Christo

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                • #9
                  Originally posted by Christo View Post
                  Thanks for the input. It does sound like aluminum cable tray might be a good solution, and far easier to work with than a bunch of short segments of either EMT or RMC. If you find a good source, let me know.
                  Thanks for the ideas.
                  Call your local electrical supply house. They'll stock cable tray, and will sometimes have better prices on the kind of stuff you'll find at Lowes and Home Depot. Most of them will sell to anybody, they've never kicked me out of there at least. Might even be a good source for more of this kind of info. For example, I started talking to one of them about running wires, and he came up with a cool little UV rated plastic clip that I can use to support panel wires.
                  Lawrence Lile, PE

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