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  • PV Array Grounding/System Grounding

    Hello Folks,

    We all know that grounding seems to be a rather difficult area to address and determine proper technique.
    Without dealing with every minute detail, in general, I am looking for opinions regarding the following...

    System setup:
    Pole mounted array with negative lead grounded to ground rod next to pole.
    Interior system componets (inverter, controller, etc.) bonded to battery negative lead and equipment ground with separete system ground rod at home structure.

    The question;
    Should the array ground rod be electrically connected (with cable lead of same gauge) to the other, system ground rod at house structure?
    Should structure rod be eliminated?

    Is individual rods ok?
    Will two rods increase or decrease chances of lightning strike reaching componets?

    ??????????????????????
    My first inclination is that the rods should be connected, but I have read so many articles and "Code Corners" about grounding, i'm somewhat confused. Any ideas/suggestions?
    Thanks
    System: 2kw Kyocera KC130's, OutbackMX60 controller, SW4024, Trimetric metering, 24 volt Hawker Powersafe AGM

    Backup: 1-ProSine 2.0, grid charged 12 volt GNB AGM battery, 15kw Diesel Genset

  • #2

    Re: PV Array Grounding/System Grounding

    Re: PV Array Grounding/System Grounding

    I think John Wiles was pretty helpful in the article below: ground the system at the house, ground at the array framing at the array location, and connect the two grounds. See: http://www.nmsu.edu/~tdi/pdf-resources/cc94.pdf.

    I also find the following guide to be useful: http://www2.fsec.ucf.edu/en/educatio...pector_NEC.pdf

    HTH,
    Jim / crewzer
    120618: System off-line for a while...

    Comment


    • #3

      Re: PV Array Grounding/System Grounding

      Re: PV Array Grounding/System Grounding

      i'll put it in a nutshell. yes, they need interconnected with at least the same gauge wire used in your ground system. i'm not posting this just so you don't have to read what crewzer posted either for you must follow the nec standards. i like to say ideally go beyond the nec and go at least 2 gauges larger and bury it minimumly 1-2 feet below the surface. this will take into account excess corroding of the wire being it's more subjected to moisture and it takes into account possible nicks to the wire. the interconnecting wire will add to the area of the ground system as well, so if you had doubts of your soil or the rod itself then this gives that little extra. more rods and wire under the ground in conjunction with the rods make dissipating lightning strikes or the near strikes better, thus improving the odds of equipment survival. though you are concerning yourself with the equipment survival you do understand that it could mean your survival too by lessening you being hit by the strike physically and could help to prevent a fire. there are no guarantees when it comes to lightning, but increasing your odds should make you feel better too.
      ps-don't solder the grounds.
      NIEL

      Comment


      • #4

        Re: PV Array Grounding/System Grounding

        Re: PV Array Grounding/System Grounding

        Originally posted by niel
        ps-don't solder the grounds.
        Why ??
        http://tinyurl.com/LMR-Solar
        http://tinyurl.com/LMR-BigLug
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        Grundfos 10 SO5-9 with 3 wire Franklin motor (1/2hp 240V 1ph # 214505 ) on a timer for 3 hr noontime run - Runs off PV
        Powerfab poletop PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe battery | 15, Evergreen 205w "12V" PV | Midnight ePanel || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT

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        • #5

          Re: PV Array Grounding/System Grounding

          Re: PV Array Grounding/System Grounding

          Originally posted by mike90045
          Originally posted by niel
          ps-don't solder the grounds.
          Why ??
          I think the NEC definition of "continuous" ground means something that won't come off.* I'm not an authority, but think soldering counts as non-permanent, like wire nuts or terminal blocks.* Mechanical crimp I *THINK* is ok, but I ran a single uninterrupted conductor all the way down so there would be no possible objection.
          I stand corrected, below.* Thanks, Neil!

          Comment


          • #6

            Re: PV Array Grounding/System Grounding

            Re: PV Array Grounding/System Grounding

            the reason is it could explode molten solder during even a modest strike and is not considered a good connection by itself. it does not have to be a continuous run of wire(as in no breaks or connectors), but it has to have good solid connections.
            NIEL

            Comment


            • #7

              Re: PV Array Grounding/System Grounding

              Re: PV Array Grounding/System Grounding

              In my experience the grounding system itself does not seem to help during lightning strikes to save your equipment. It may provide a better path to ground to prevent a fire. The only systems that I've seen that actually work to prevent lightning strikes are air terminal systems, the same stuff you see on hospitals and large commercial buildings. You can purchase the equipment for a medium sized solar system for around $500, and It's very easy to install.

              Comment


              • #8

                Re: PV Array Grounding/System Grounding

                Re: PV Array Grounding/System Grounding

                got a link to this stuff as i've seen nothing that prevents a strike? nevermind, as it is nothing more than a lightning rod and they do not prevent a strike either.
                NIEL

                Comment


                • #9

                  Re: PV Array Grounding/System Grounding

                  Re: PV Array Grounding/System Grounding

                  You're right niel there is nothing out there to prevent a lightning strike I should have worded that differently. Air terminals simply provide a path to ground from different points on a building, just having a grounded system itself will not help do that.
                  http://www.lightning.org is a good source for info on lightning protection, there is many more sites out there but this is a good place to start.

                  Comment


                  • #10

                    Re: PV Array Grounding/System Grounding

                    Re: PV Array Grounding/System Grounding

                    it has also been argued that a lightning rod could attract the lightning to the area of the array that may not have been hit otherwise. i have done much research into the area of lightning protection and it is amazing the steps i've read that were considered by others to be minimal and we aren't talking the nec either. i wish i could remember the site i read this for my home that they suggested a rod of at least 20-30 feet into the ground. i have enough metal in the air from my ham radio antennas that makes my whole place one big lightning rod. you might say, that should make my neighbors feel better that i'd most likely get the hit, but being their places are in the proximity of the strike hitting me, it would give an emp strong enough to them that they might as well have been struck directly instead of me. even bad connections or wiring can amplify this as i've lit up incandescent light bulbs with my 100w radio in a place i once lived in with bad wiring. emps could far exceed what my radio did. it's a double edged sword as it can go either way with nothing for sure no matter the extent you take it too. the nec states the minimum they deem good protection and i will not go ungrounded as i've seen an antenna of mine in the past get its ground accidentally disconnected and the first storm that came by had a lightning strike to that antenna. i found that disconnect and it was never hit again, but years later it did blow off of my roof and hit the electric lines 100 feet away. 4th of july.
                    NIEL

                    Comment


                    • #11

                      Re: PV Array Grounding/System Grounding

                      Re: PV Array Grounding/System Grounding

                      Well this is what I have seen over the years... we have an area just north of Flagstaff on the mountain with probably 50-75 solar systems. Most of these systems were installed about 15-20 years ago. Around 8-10% of these system have lightning protection systems installed including air terminals, not one of these systems has been hit by lightning in 15-20 years. In that same area we do about 20 service calls every year to repair systems hit by lightning.

                      Comment


                      • #12

                        Re: PV Array Grounding/System Grounding

                        Re: PV Array Grounding/System Grounding

                        Here are some interesting thoughts (plus a linked white paper) on grounding and the NEC...

                        http://www.electrical-contractor.net...80_Removal.htm

                        No black and white answers, but lots of interesting questions.

                        I guess I should thank my lucky stars that I am not in a heavy lightening area.

                        -Bill
                        20x BP 4175B panels (replacement) + Xantrex GT 3.3 inverter for 3kW Grid Tied system + Honda eu2000i Inverter/Generator for emergency backup.

                        Comment


                        • #13

                          Re: PV Array Grounding/System Grounding

                          Re: PV Array Grounding/System Grounding

                          that's some of the stuff i was talking about bill, but it wasn't whiles' site that i read all of it. i'd put some really deep rods in if i didn't have lots of bedrock below my home. i do have a cage arrangement though and 7 ground rods all intertied with buried #6. i, no doubtedly, will have internal damages by the emp of a strike and would be surprised if i came out unscathed inside by one. the neighbors won't have as much of a chance as i would in my view, but lightning isn't all that predictable or tame to say for sure on the outcome of a direct strike on my home. complicating the odds is an underground stream that flows under my home near the surface. one of the rods does contact it directly in the front.
                          dlwindsun,
                          you don't suppose the lightning was being pulled into that general area by those with the lightning rods do you? possibility?
                          NIEL

                          Comment


                          • #14

                            Re: PV Array Grounding/System Grounding

                            Re: PV Array Grounding/System Grounding

                            I do not think the lightning rods are attracting the lightning to the other homes.

                            With all the lightning protection we have tried and seen nothing seems to have made a difference so far except air terminals. Most of the air terminals we see installed are on three story houses with metal roofs with lots of point edges, what is odd is that the systems that seem to get hit are the one story homes with a standard A frame design. For all we know it could just be total bad luck.

                            Surge protection/Lightning arrestors do not seem to help prevent damage to solar equipment. Intricate grounding systems do not seem to help prevent damage to solar equipment. Lightning is a big problem for us here in northern Arizona and I would love to find something that actually makes a difference.

                            Comment


                            • #15

                              Re: PV Array Grounding/System Grounding

                              Re: PV Array Grounding/System Grounding

                              if you find something, let me know too. right now my antennas are lightning rods and part of the lightning will enter my home through the antenna cables. luckilly, i'm not at the top of the hill, but that doesn't make me feel all that much better or exempt of a strike as i've seen it hit lower in the valley.
                              dlw,
                              the pvs are generally the opposite of lightning rods as lightning rods dissipate much static buildup at their points aimed skyward. the vast flat area pvs present, do buildup a great deal of static and make the possibility of a strike increased even when properly grounded.
                              NIEL

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