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  • Gounding a Roof Top Array

    Sunking Thanks for the Sticky Grounding Tutorial - Fills in a lot of gaps along with the video you posted on this thread. (But Note that the pic links on the Grounding Tutorial are no longer working. So I cannot see the diagrams there.)

    Trying to properly ground my roof top array. After watching the posted videos from the other thread. Looking for the best option ...


    Example #1: I do not think it should be done like this ... but I am not sure?

    Seperate_Ground.JPG



    Example #2: So, Would this be more Acceptable? Only problem ... seems this might let lightening inside the structure as the array rack grounding conductor is now entering into the house and RE sub-panel (bonded with other EGC's grounds and on to the main load panel ground / neutral bond).

    Single_Ground.JPG



    Example #3: Or could I do this with 2 Ground Electrodes Bonded together? If yes, what size wire for the bond between GE's? Stranded or Solid? Insulated (green) or bare? Do you bury the conductor between the 2 GE's?

    Seperate_Ground_Bonded.JPG




    Which, if any, or all of these would work? Which would be best? Please sight any that would work AND the possible best scenario as some of these are easier to achieve than others ... AND/OR an alternate if none would work.

    Right now I have a bare #8 coming from the Array rack (the array/panels are bonded to the rack with bonding clips) along with #10 Solar Cable for the 3S3P panels in conduit to the combiner box and three 15amp DC breakers . The Ground comes into the combiner box to the grounding bus bar and out thru conduit with #8 green insulated stranded THHN along with a #8 Red and #8 Black THHN for the DC power from the array. I Can change any of this if necessary.

    Thanks
    Mike
    285Wx9 / MNClassic 150 / CSW4024 / TrojanL16H-ACx4

  • #2
    OK good questions and easy to answer. All 3 are compliant.

    Now for details. Drawing 1 and 3 are technically correct, but I I know what is throwing you off track. Technically the Ground Symbol implies they are bonded electrically together. All drawing 3 is clarification. You got tripped up thinking Drawing 1 shows the two rods isolated which is a huge No-No, They must be bonded with a #6 AWG and can be solid, stranded, bare, insulated, tinned or not tinned. Best practice bare, solid, and tinned. No benefit in using larger than #6 AWG, you can larger with no harm, but code requires #6 AWG minimum.

    As for Drawing 2 you have a misconception. You show a Single Point Ground which is ideal. For current to flow it must have two nodes, one to enter, and a one to to exit. Single point is like a cement wall blocking on/off-ramps to a highway.

    Lastly code requires all electrodes to be bonded together to form a common electrode.

    Edit Note:

    Just guessing Drawing 1 might be an Example of 690.47(D) which is DEAD Wrong using isolated rods. DO NOT DO THAT and what Mike was talking about when he said should be removed immediately from the code.
    Last edited by Sunking; 04-18-2018, 06:12 PM.
    MSEE, PE

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    • #3
      Well the blanks of the house pictures I found on the internet ... But the Green Ground Examples are what I drew in to each drawing. I guess I should NOT have draw the circle around the ground symbol? Is it the circle that indicates bonding?

      Just guessing Drawing 1 might be an Example of 690.47(D) which is DEAD Wrong using isolated rods. DO NOT DO THAT and what Mike was talking about when he said should be removed immediately from the code.
      Drawing 1 is what I have now ... except that the ground goes into the RE Sub-Panel and it's one separate insulated bus bar that is NOT bonded to the Sub-Panel and then on out to the grounding rod. The ground comes from the array, into my attic, thru the combiner box where it is connected to a bus bar that is bonded to the combiner, and on out thru conduit into my control room and sub-panel and on to the ground. But it is NOT connected to the home AC ground in any way. Nor are the 2 GE's bonded together.

      My house was built in the early 80s. The Builder / Owner at the time was a bit of a "Jack Leg" and at that time in Putnam County Florida code enforcement was very lax. There is only a single GE for the main load panel and sub panel (not my RE sub-panel). The sub panel has the EGC's and Grounded Circuit Conductors bonded in the Sub-Panel (a code no no) with 6/3 NMB going to the main panel. I plan to redo all that this summer. BUT also I think to pass inspection at the time ... with only one GE, the Owner/Builder jumped over from the GE with bear #6 to a brass water spigot. FUNNY thing is ... once it passes thru the outside wall of the house to under the house, it goes into PVC ... NOT GROUNDED. So the whole house AC system only has 1 GE under the meter.

      So right now. I only have 1 GE. It was my thought to bond the 2nd GE I drove for the Array to the existing GE as they are about 25' apart. The code requires 2 in most cases and at least 6' apart correct? I could Kill 2 birds with a #6 wire if I simply boned my new array GE with my old Whole house GE? Yes?

      As for Drawing 2 you have a misconception. You show a Single Point Ground which is ideal. For current to flow it must have two nodes, one to enter, and a one to to exit. Single point is like a cement wall blocking on/off-ramps to a highway.
      Switching from #1 (what I have now) to #2 is the easiest. All I would have to do is move the array ground off its existing insulated bus bar over to the bonded bus bar in my RE sub-panel and has a ground already running to the main panel for the other EGC's in the sub-panel. Then simply remove the grounding conductor that is not being used and remove the new GE I installed. But I would still be left with only 1 GE that really needs 2 bonded together and at least 6' apart.

      AND my concern is ... what if lightning struck the Array. Isn't that giving lightening a direct path then into the house and the house electrical system? (which is why I gave the array a separate grounding conductor and GE in the first place ... to keep it out of the whole house electrical. )

      So doing #2 would be the cheapest, but #3 would probably solve more problems and only cost what a piece of #6 30' long would cost.

      If I go the route of #3 ... the shortest route from one GE to the other GE is thru the Craw space of the house. The craw space is actually about 3.5' high so it's easy to get up under there. Would it be acceptable to run a #6 insulated wire stapled to the floor joists or would it be better to bury it in the ground - except where it passes thru the exterior walls - and go solid bear copper?
      285Wx9 / MNClassic 150 / CSW4024 / TrojanL16H-ACx4

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      • #4
        Oh by the way, should I fix the drawings in post number one and remove the circles around the ground symbols? That would be easy to do.
        285Wx9 / MNClassic 150 / CSW4024 / TrojanL16H-ACx4

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        • #5
          Any followup to post #3?
          285Wx9 / MNClassic 150 / CSW4024 / TrojanL16H-ACx4

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          • #6
            Originally posted by Matrix View Post
            Well the blanks of the house pictures I found on the internet ... But the Green Ground Examples are what I drew in to each drawing. I guess I should NOT have draw the circle around the ground symbol? Is it the circle that indicates bonding?
            Nah does not mean anything, just what can happen between what you see on paper and what is actually done. This is where forums get into trouble, and why I hesitate.



            Originally posted by Matrix View Post
            Drawing 1 is what I have now ... except that the ground goes into the RE Sub-Panel and it's one separate insulated bus bar that is NOT bonded to the Sub-Panel and then on out to the grounding rod. The ground comes from the array, into my attic, thru the combiner box where it is connected to a bus bar that is bonded to the combiner, and on out thru conduit into my control room and sub-panel and on to the ground. But it is NOT connected to the home AC ground in any way. Nor are the 2 GE's bonded together.
            OK I think I got the picture and we can get you on the right track. Take the Panel Frame Ground out of the conduit and go straight to the Ground Rod and bond all GE's together. Right now the Frame Ground is an EGC and you want to make it a GEC.

            Disclaimer: My comments are based on what I think you are telling me and the picture in my head from your description. The responsibility is all on you. Clear enough?

            MSEE, PE

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            • #7
              Yes thanks
              285Wx9 / MNClassic 150 / CSW4024 / TrojanL16H-ACx4

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              • #8
                You are welcome. Had to be firm because without actually seeing what you have and how it is all connected, I could be full chit giving bad advice. Based on what I think you described should be a good plan. So if you think I might have overlooked something, or you still have questions, ask away. I just want to make sure you take ownership.

                Perhaps a different approach may shine some light and help you see the big picture because there are a lot of confusing terms with respect to Ground. Grounding is a terrible word and causes a lot of confusion even among pros.

                So wrap you noodle around this. The EGC (called EBC today equipment bonding jumper) primary purpose is to operate breakers. It requires no connection to operate, it s bonded to Earth as a reference point to minimize touch potential differences during normal operation. That is all it does and Shall Not be used to clear utility and lightning faults.

                The GEC primary purpose is for protection from the outside elements of Nature and the Utility. Today for clarification in the code, there is only 1 GEC and 1 only. It is the conductor ran between your AC Meter Box and and GES aka Ground Electrode System. Note I did not say Ground Rod, I said GES which includes all electrodes bonded together to form a common GES. Make sure you clearly understand EGC/EBC, GEC and GES. Now we can move on.

                OK the panels on top of your house we can use them like Air Terminals aka Lightning Rods to met code compliance. Or they can be configured as Equipment requiring an EGC/EBC. Code gives you the two options. Right now what I think you have is configured as Equipment. What I am suggesting is to reconfigure as Air Terminals. You can do it eitherway and both are compliant. Best Practice is what I am suggesting but it can cost more money.

                The conductor I have been talking about, I have called it an GEC and today it is not called that. It is a Lightning Down Bonding Conductor. Use to be any conductor that went to the GES was called a GEC, not today as I explained above. So what I am telling you is treat the panels as Air Terminals and take the Down Conductor directly to the GES bypassing everything. A straight dire route to EARTH good ole dirt. If you drive a rod to accomplish that, then it must be bonded to all other electrodes so as to make a common GES. It can also be routed to the GEC and bonded below the Meter Can just above or below grade. It comes down to how everything is laid out. A good layout will bring the Lightning Down Conductor straight down to the AC Meter Box so you do not have to drive another rod and go that extra expense and trouble.

                So now get your Noodle wrapped around that picture and go see what you got.
                MSEE, PE

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                • #9
                  Thanks ... Processing ... Always Awesome. More later. (Oh BTW ... could not figure out who was you in the Mike Holt Video ... at first I thought you where "Bill" until they introduced him as Bill)
                  285Wx9 / MNClassic 150 / CSW4024 / TrojanL16H-ACx4

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                  • #10
                    Ok so as of last week I finally got time to bond all of my electrodes together as a common GES. I had 2 grounding electrodes that were separate, but now they are both bonded with #6 at ground level.

                    In working with my whole house grounding system, I came across a situation (one of many I have found thru the years) created by the original home owner/builder. Only one grounding electrode was ever driven for the house under the meter back in the 80s. But I guess to pass code or something, the owner/builder came off of the one grounding electrode and with stranded #4 bonded the grounding electrode to a nearby brass water faucet 2ft away. This must have passed inspection, and I guess it would have been OK ... BUT ... the brass faucet was attached to PVC pipe in the wall under the house. So what appeared to be 2 earthing locations connected to pipe was really only the 1, the single grounding electrode.

                    I now have 2 bonded together about 20 ft apart, and I also added a 3rd bonded to the others all with a single piece of #6. The 3rd grounding electrode is 8 ft away from the original whole house electrode under the meter. I also disconnected the bond from the faucet and PVC pipe.

                    285Wx9 / MNClassic 150 / CSW4024 / TrojanL16H-ACx4

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