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  • earth equipment ground

    Hi All,

    I've got two pole-mount PV arrays that need earth grounding. I will be changing panel angle four times a year on these poles. I need a method to go from solid, fixed ground cable on the pole to the solid, fixed ground cable (weeb) on the movable panel array. Should I use some kind of braided copper cable to allow for the moment of the PV assemblies?

    One other thing. I was watching a you-tube video about code for grounding panels. They said that allowances for ground rods at the panels had been removed sometime around 2008/2010. This method really appeals to me. Even though this method is not now expressly listed, does that mean it's not allowed?

    Sure would appreciate any insight .....

  • #2
    Ground rod requirements were relaxed in NEC 2011, but strengthened again in NEC 2014. Without more information about the system, it is hard to know what would apply to you.
    CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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    • #3
      Originally posted by sensij View Post
      Ground rod requirements were relaxed in NEC 2011, but strengthened again in NEC 2014. Without more information about the system, it is hard to know what would apply to you.

      The system has two Iron Ridge top-of-pole mounts on 5" vertical steel pipe. Each pole carries (4) 265 Watt panels (~30 volts each). The four panels on each mount are sub-divided into two groups of two panels wired in series to double voltage. The two groups on each mount are fed via conduit into a combiner box in a shed fifteen feet away. From the combiner, the DC is fed into a Magnum power center with charge controller. Inside the power center, the earth ground bus has been connected to the power ground buss (by the factory) with notice to remove the jumper if that had been accomplished somewhere else.

      I want to sink ground rods by each manual-tilt, pole mount. I want to sink a ground rod beside the shed to connect to the combiner box earth ground. Sound workable? What about the original ground problem at the mount?

      Comment


      • #4
        Originally posted by BAndrews View Post
        I want to sink ground rods by each manual-tilt, pole mount. I want to sink a ground rod beside the shed to connect to the combiner box earth ground. Sound workable? What about the original ground problem at the mount?
        Why? It gains you nothing.

        MSEE, PE

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        • #5
          Originally posted by Sunking View Post

          Why? It gains you nothing.

          Your reply is not helpful.

          Why, specifically, does my plan gain me nothing? How would you go about providing earth-ground in a non-tie system? The devil is in the details my friend. And my particular "devil" is living in a high lightning-strike area (N. Florida).

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          • #6
            Are these pole mounts made of metal buried into the ground in cement peers?
            MSEE, PE

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            • #7
              Originally posted by Sunking View Post
              Are these pole mounts made of metal buried into the ground in cement peers?

              The 5", schedule 40, steel pole mounts are set in concrete 30" in diameter and 54" deep. If you're saying that further earth grounding is unnecessary, I would very much appreciate a cite.


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              • #8
                Originally posted by BAndrews View Post


                The 5", schedule 40, steel pole mounts are set in concrete 30" in diameter and 54" deep. If you're saying that further earth grounding is unnecessary, I would very much appreciate a cite.
                Easy Peazy.

                NEC 250.52 (3) Grounding Electrodes, Concrete Encased Electrodes

                Metallic components shall be encased by at least 50 mm (2 in.) of concrete and shall be located horizontally within that portion of a concrete foundation or footing that is in direct contact with the earth or within vertical foundations or structural components or members that are in direct contact with the earth. If multiple concrete-encased electrodes are present at a building or structure, it shall be permissible to bond only one into the grounding electrode system.

                Informational Note: Concrete installed with insulation, vapor barriers, films or similar items separating the concrete from the earth is not considered to be in “direct contact” with the earth.

                You can bury all the rods you want, but will not help one little bit as there is no better electrode than concrete encased electrode. They were invented by Herbet G Ufer in 1942 for Ammunition Bunkers in Tuscon during WWII. A Ufer ground in NEC is called a Concrete Encased Electrode (CCE)). They are far more effective and a lot cheaper than copper rod systems. They were extremely effective in AZ extremely dry soils. Concrete is highly conductive with a massive surface area in contact with soil. There is nothing you can add that is better than you already have.

                I design Telephone, Data Centers and Cell Tower grounding systems for a living for the past 37 years professionally. We use UL Master Label Certification. There is nothing better than a CCE or Ufer electrode system. This sounds like a ground mount system low to the ground?
                Last edited by Sunking; 06-04-2016, 04:29 PM.
                MSEE, PE

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                • #9
                  Originally posted by Sunking View Post
                  This sounds like a ground mount system low to the ground?

                  Excellent info, thanks. The mounts are seven foot above-ground-level.

                  Question:

                  These poles were uncoated steel. I sanded them down and painted the surface with primer followed by multiple coats of Rust-Oleum Pro Oil-Based Enamel. Did I destroy the grounding value of this assembly?

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                  • #10
                    Originally posted by BAndrews View Post


                    Excellent info, thanks. The mounts are seven foot above-ground-level.

                    Question:

                    These poles were uncoated steel. I sanded them down and painted the surface with primer followed by multiple coats of Rust-Oleum Pro Oil-Based Enamel. Did I destroy the grounding value of this assembly?
                    No absolutely not. If you use the poles to bond the panels with a Bonding Jumper, just remove the Paint down to bare metal, drill and tap holes of a self threading screw. I doubt that will be necessary unless you used isolating bushings to mount the panels. I would need to know more details to help you out further.

                    If you need Bonding Jumpers just use an Extra Flex Stranded # 6 AWG wire.
                    MSEE, PE

                    Comment


                    • #11
                      Originally posted by BAndrews View Post


                      Excellent info, thanks. The mounts are seven foot above-ground-level.

                      Question:

                      These poles were uncoated steel. I sanded them down and painted the surface with primer followed by multiple coats of Rust-Oleum Pro Oil-Based Enamel. Did I destroy the grounding value of this assembly?
                      If you painted the entire portion of the pole that is buried in concrete, both outside and inside, especially if you used a vinyl coating which is an electrical insulator, you might have a problem. Painting the part of the pole which is above ground is not an issue, except where you connect bonding jumpers to it, as Sunking described.
                      Rust below ground is not an issue either.
                      SunnyBoy 3000 US, 18 BP Solar 175B panels.

                      Comment


                      • #12
                        Originally posted by Sunking View Post
                        No absolutely not. If you use the poles to bond the panels with a Bonding Jumper, just remove the Paint down to bare metal, drill and tap holes of a self threading screw. I doubt that will be necessary unless you used isolating bushings to mount the panels. I would need to know more details to help you out further.

                        If you need Bonding Jumpers just use an Extra Flex Stranded # 6 AWG wire.

                        Good to know. Thanks.

                        The bonding jumper on the main vertical steel, 5" pipe ....... what connector would you recommend? Part numbers and a recommended vendor would be greatly appreciated. I can use a belt sander to "clean" and "level off" a spot on the pipe, and a tap and die set to thread it.




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                        • #13
                          Originally posted by inetdog View Post

                          If you painted the entire portion of the pole that is buried in concrete, both outside and inside, especially if you used a vinyl coating which is an electrical insulator, you might have a problem. Painting the part of the pole which is above ground is not an issue, except where you connect bonding jumpers to it, as Sunking described.
                          Rust below ground is not an issue either.

                          The inside of the 5", schedule 40 steel pipe was not coated on the inside at all. Also, the pipe was located in the hole, pre-pour, with a wood form that held the bottom of the pipe off the bottom of the hole at a height of 1.5 inches.

                          Thanks for the info.....

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