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Thread: PV Array Grounding/System Grounding

  1. #1

    Default 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. #2

    Default 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...

  3. #3
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    Default 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

  4. #4
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    Default Re: PV Array Grounding/System Grounding

    Quote Originally Posted by niel
    ps-don't solder the grounds.
    Why ??
    http://tinyurl.com/LMR-Solar
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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

  5. #5

    Default Re: PV Array Grounding/System Grounding

    Quote Originally Posted by mike90045
    Quote 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!

  6. #6
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    Default 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

  7. Default 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.

  8. #8
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    Default 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

  9. Default 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.

  10. #10
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    Default 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

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