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  • Ground mount GridTied grounding question

    I have attached Electrical Schematic for my system and highlighted in red my area of concern with grounding.

    Grounding.png
    There are 2 arrays and 2 inverters in the IronRidge ground mounted Grid Tied system and I am using Sch 40 and 80 PVC and this is an ungrounded system using the SunnyBoy Transformerless Inverters. All the grounding is suppose to go to the earth ground in the Main Service Panel (MSP).

    In the Conduit Schedule, located on the bottom left of the schematic, it incorrectly identifies ground 1 as 12AWG ENGAGE CABLE. They are all 10AWG with no micro inverters in the system.

    Let me know if this sounds correct. The 10AWG DC grounds (1-1A) from the IronRidge rack enter the inverters on the DC side and connect there. On the AC side of the inverters the 10AWG AC grounds (2-2A) come out and into the 125A Load Center. They would then connect with the 8AWG ground inside the Load Center and be a continuous run to the Main Service Panel and connect to earth ground. I thought I read somewhere that in an ungrounded system using SMA Inverters the ground should be a continuous (no breaks) run from the AC side of the Inverter to earth ground in the MSP. To ground the AC disconnect I am running a separate 10AWG ground wire into the MSP.

    Question...

    1. Can the (2)10AWG AC grounds from the inverters be connected together inside the 125A Load Center with the 8AWG ground or do they have to run separate. In either case how are they connected to stay within NEC code?

    2. How do I ground the 125A Load Center?

    Thanks for any help.
    Attached Files

  • #2
    One of the few things the NEC almost got right. Diverting a lighting strike to inside of your house main panel, before sending it to ground. That's a fail in my book.

    Local inspectors are your "go to" folks, but they don't know you from Adam, and since you are not a contractor, homeowners often get "dissed".

    I don't want to give you bad advice, so the best is to befriend the inspector, and ask him how he would like you to do it.
    Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister

    Comment


    • #3
      I have two Sunny Boy inverters.

      Run your earth ground back to the MSP.. Its ok if it joins a few other wires with the proper connectors.

      And while its not required, you should sink a ground rod within a few feet of your inverter and bond that to the grounding cable(s) going back to the MSP.

      Earth Grounds are about resistance.. the faster the lightening can get into the ground, the less damage it will do to everything else. I have a ground rod within a few feet of my inverter... and now that I've added a second inverter, I'm going to sink another ground rod just for the hell of it. You can never have too many earth grounds... just make sure the grounds are all attached to each other and go back to the main service panel.. the fewer connections the better.. which is why those C style grounding lugs are so nice.. You can strip the insulation away without breaking the wire so it is still one continuous run.

      Comment


      • #4
        Originally posted by Salts View Post
        ............And while its not required, you should sink a ground rod within a few feet of your inverter and bond that to the grounding cable(s) going back to the MSP.

        Earth Grounds are about resistance.. the faster the lightening can get into the ground, the less damage it will do to everything else. I have a ground rod within a few feet of my inverter... and now that I've added a second inverter, I'm going to sink another ground rod just for the hell of it. You can never have too many earth grounds... just make sure the grounds are all attached to each other and go back to the main service panel.. the fewer connections the better.. which is why those C style grounding lugs are so nice.. You can strip the insulation away without breaking the wire so it is still one continuous run.
        OP..........be careful the above is not good advice......in fact it is dangerous.

        Comment


        • #5
          Originally posted by DanS26 View Post

          OP..........be careful the above is not good advice......in fact it is dangerous.
          How is that dangerous? My inspector certainly didn't have a problem with it, and HAM radio operators around the world don't seem to either. Some of these HAMS sink dozens of ground rods encircling their entire homes.

          There is nothing wrong with more ground rods, just so long as the primary ground is hooked up correctly.

          You're thinking of ground loops...

          Comment


          • #6
            Originally posted by Salts View Post

            How is that dangerous? My inspector certainly didn't have a problem with it, and HAM radio operators around the world don't seem to either. Some of these HAMS sink dozens of ground rods encircling their entire homes.

            There is nothing wrong with more ground rods, just so long as the primary ground is hooked up correctly.

            You're thinking of ground loops...
            Multiple ground rods are acceptable as long as they are all tied together to create the same potential. If they are separate then the chance of a large enough potential is dangerous to someone that comes in contact with both.

            Just adding another ground rod without bonding it to an existing one is dangerous.

            Comment


            • #7
              Originally posted by SunEagle View Post

              Multiple ground rods are acceptable as long as they are all tied together to create the same potential. If they are separate then the chance of a large enough potential is dangerous to someone that comes in contact with both.

              Just adding another ground rod without bonding it to an existing one is dangerous.
              I think your statement is accurate, but not complete.....

              You can add un-bonded ground rods, just so long as they aren't part of the primary grounding system that is required.. The panel has to be grounded back to the main.. but adding a second isolated ground isn't going to harm anything. Technically, the entire array is basically a ground rod since it penetrates 6 feet into the earth.

              What they don't want you to do is try to save money on green wire by using a separate grounding system for some sub panel 200 feet away because its not convenient to run it back to the MSP.

              For example.. My solar array is 60 something feet long... the inverters are on the 20 foot which is closest to my home. If I put a ground rod at the far end of the array and connected it to the frame, I'd be fine.. Just so long as the electrical boxes have proper grounds going back to the MSP.

              Comment


              • #8
                Originally posted by Salts View Post

                I think your statement is accurate, but not complete.....

                You can add un-bonded ground rods, just so long as they aren't part of the primary grounding system that is required.. The panel has to be grounded back to the main.. but adding a second isolated ground isn't going to harm anything. Technically, the entire array is basically a ground rod since it penetrates 6 feet into the earth.

                What they don't want you to do is try to save money on green wire by using a separate grounding system for some sub panel 200 feet away because its not convenient to run it back to the MSP.

                For example.. My solar array is 60 something feet long... the inverters are on the 20 foot which is closest to my home. If I put a ground rod at the far end of the array and connected it to the frame, I'd be fine.. Just so long as the electrical boxes have proper grounds going back to the MSP.
                Agree. If you are using the ground rod for the panel frames and rack for lightning protection and not for the system ground for the electrical boxes it should be ok.

                The problem with DIY people without electrical background can be confusing and dangerous if they misinterpret the information provided by posters.

                I would caution anyone to be as clear as possible when giving electrical circuit details but as always I say to refer to the AHJ for your area to get the final approval on an installation.

                Comment


                • #9
                  This is for the OP......

                  Mike Holt has spent many years (maybe decades) trying to educate electricians in the proper grounding and bonding methods. If you are truly interested in making your system safe as to grounding then you would be wise to carefully study this site and learn all you can........

                  https://forums.mikeholt.com/forums/b...-grounding.22/

                  Comment


                  • #10
                    Originally posted by DanS26 View Post
                    This is for the OP......

                    Mike Holt has spent many years (maybe decades) trying to educate electricians in the proper grounding and bonding methods. If you are truly interested in making your system safe as to grounding then you would be wise to carefully study this site and learn all you can........

                    https://forums.mikeholt.com/forums/b...-grounding.22/
                    I have read his website... lots of good information spelled out in a way people can understand.

                    Comment


                    • #11
                      Here's a couple more links to Ground Rods, Step Voltage Hazards and such.
                      It's not easy, and sometimes the "code" way is not the best way, since code can't foresee every circumstance.

                      https://www.youtube.com/watch?v=7vAA95ZZdjI
                      https://incident-prevention.com/ip-a...ouch-potential

                      Think of ripples from a stone thrown in a pond, if any body part bridge 2 ripples = painful lesson

                      Proper grounding is important.
                      Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                      || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                      || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                      solar: http://tinyurl.com/LMR-Solar
                      gen: http://tinyurl.com/LMR-Lister

                      Comment


                      • #12
                        Everyone,

                        Thanks for all the information and I will read Holtz's article. What do I need to join the AC Grounds from the Inverters to the Ground going back to the Service Panel? I think I read that it has to be an irreversible connector. I have been living out here in the southern Nevada desert for 5 years and have not seen any lightning but any thing is possible.

                        Trying to upload pics but keep getting error code, any reason?

                        Comment


                        • #13
                          Originally posted by Sgtnarc1 View Post
                          ..............

                          Trying to upload pics but keep getting error code, any reason?
                          Likely pics are too large, nobody wants to load a 12mp image on their screen.
                          Decrease the size, lower the resolution. You can post pics here that are not all grains & blurred.

                          I use a program called IrfanView, https://www.irfanview.com/ and it's freeware, no nag and super powerful......and small.

                          Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                          || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                          || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                          solar: http://tinyurl.com/LMR-Solar
                          gen: http://tinyurl.com/LMR-Lister

                          Comment


                          • #14
                            Here are pics of the current project still in progress just as a reference for above questions



                            Arrays.JPGInverters and Load Center.JPGAC Disconnect.JPG
                            Attached Files

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