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  • Grounding? EGC and GEC required?

    Ok.. trying to wrap my head around properly grounding my PV system. I thought I had it... but then I read of another code change that makes me scratch my head a good bit.

    With that said... Here is what I'm currently planning.. can someone please tell me if this meets current code requirements or anything I need to change.

    I'm using IronRidge racking with integrated grounding.

    Plan for the EGC was to run a #10 or #8 (10 is the minimum required) stranded/insulated wire from the grounding lug on the rack to the EGC lug on the inverter ran in the conduit with the DC conductors. Then from the inverter to the 40a disconnect... then to the sub panel ground bar.

    From what I'm reading, I will also need to run a GEC from the racking system back to the GE using #6 solid copper.

    So both the GEC and EGC connect to the racking system/array via the ground lugs on the rack themselves... correct?

    I had also read about an additional ground rod being needed potentially... however I don't think I would need it due to proximity of the building's GE. Might have to call the AHJ to find out on that one....

    If it matters, the inverter being used is a SMA SB7.7

    Suggestions?

    Thanks for the help.
    Last edited by Mr4btTahoe; 04-17-2018, 03:50 PM.

  • #2


    Well there are no good answers to your question. There is a right and wrong answer and both can be code compliant. It depends on what code cycle your AHJ is on, most notable ia 2014 and whether or not your AHJ Adopted or Rejected 697.47(d) or not. Most AHJ rejected it because it is extremely dangerous and should be ignored.

    How it got there is simple, this is what happens when you let advocates make safety and energy policies. John Wiles Phd NMSU is the Godfather and high priest of all things solar in the public eye. He is a member of the NEC code making panel. Like most academics with a Phd has never done anything in real life and do not know how things really work. He wrote 690 and lobbied to get it passed with help of manufactures and electrical contractors. Done solely to make installation labor and equipment less expensive and affordable with no regard to safety.

    EGC and GEC have different functions. EGC basically is to provide a path to operate breaker and fuses. It is a wire with no direct realittiopn to earth aka Ground other than a reference point which could be a ham sandwich Its sole purpose is to protect wirng from faults in your homes AC and DC wiring.

    GEC function is to discharge static, and provide a planned fault path for external faults like high utility voltage and lightning. Its job is to keep that crap out of you rhomes wiring an dnot invite it inside. Well 690.47(d) ninvite lightning and utility faults inside your home by using an EGC.

    So if your AHJ adopted 690.47(d) is to ignore it and not use that option and use a, b, or c. Having said that DO NOT use an isolated ground rod as that is extremely dangerous. If you use a Drive a Ground Rod to bond the panels with a GE Bonding Conductor, dig a trench to your AC Service Ground and bond the two together with a #6 AWG Solid Bare Conductor.

    Mike Holt is the God of NEC code and runs a NEC Code Forum. I am a moderator on that forum. Mike carries a big stick in the NEC and his moderators have either been or have been a voting member on NEC. The Forum has 100,000 members and everyone of them in the industry. Mike makes his living teaching industry professionals especially sparkies. If you want to obtain and pass your test to be an electrician, chances are Mike Holt taught you. Mike is a Bible Thumping Christian with no ill words, except when it comes to NEC 690.47(d). Watch the first video an din the first minute Mike shocked all us moderators with his very strong statement during out 2014 Code cycle meeting. Watch both videos and you will get a batter idea. Yep I am in both videos. I am the good looking one. The second video will tel you how and answer your question.







    Last edited by Sunking; 04-17-2018, 07:44 PM.
    MSEE, PE

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    • #3
      Thanks ... I am watching the outcome of the thread with interest as I have similar questions.

      To the Mods Here: Might it be a good idea to have a Sub-Forum just for electrical and code questions that might be RE related, but not directly RE specifically. I have a similar question as above and have been at a loss as to the best forum to post it in as it does not relate directly to Off-Grid or Grid-Tied, but more to wiring said RE system to the home etc. (and another question more related to a Sub-Panel not directly connect to my RE system, but in the same room and needing updating while having everything else taken apart).

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

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      • #4
        Originally posted by Matrix View Post
        To the Mods Here: Might it be a good idea to have a Sub-Forum just for electrical and code questions that might be RE related,
        Not so sure that is a good idea. This is a DIY forum, not professional. Although there area couple of professional members with Code experience, i snot where folks should get professional answers. The forum can be held accountable, and some pretender, this site has many pretending to know something, could get the owners in deep trouble if someone takes a pretenders advice and gets hurt or cause damages. Making a sub-forum for that is a perfect storm for trouble.

        On a professional forum like I moderate on has experienced that kind of trouble years ago. Fortunately today there are so many members (100K), all pros as required for membership, any wrong response is corrected in seconds my dozens of people who know better. It could take days here for someone to spot dangerous advice, and when spotted the mods do not have much authority to do anything about it.

        Stop and think about it. A licensed electrician requires two years formal education, 5-year apprenticeship, and pass written exams before they can work on their own. Even they get it wrong at times. Fortunately pros have at leat a fail safe to protect the public, INSPECTIONS and BONDED/INSURED. So not so sure it is a good idea to ask DIY's who tinkers and threw something together and pretends to be an expert the kind of person you want code and professional advice from.

        My two-cents worth.
        MSEE, PE

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        • #5
          Thanks for the videos. I really like how he explains things.

          So.. let me make sure I'm wrapping my head around it.

          If I run an EGC from the rack on the roof... down to the inverter... to the disconnect... to the sub-panel's ground bus (which is bonded to an electrode as well as a ground conductor from the main service panel at the house).... there shouldn't be any other need for "extra" grounding.

          So the EGC sized for the disconnect (40a) (according to 250.122 would be 10awg copper) should be all that is needed... right?

          Comment


          • #6
            I also wanted to add.... considering the nature of my questions as far as code and safety, I release anyone associated with this forum from liability when responding.

            This installation has to pass 2 inspections before activation... 1 by the AHJ and 1 by the POCO.

            I am asking these questions solely to avoid hang-ups on inspection day. I'd prefer to have it all right the first go around and not have to re-do anything.

            I know how answering questions directly when it comes to code and safety can have liability issues and wanted to reassure the members and admins that the liability falls on me and those performing the final inspections.

            Again, thanks for all the information. Spent last night and a good chunk of the morning digging deeper into the code and I think the EGC is all that will be required for my specific installation as my installation falls into the "Ungrounded" category. If anyone can verify that.. I'd appreciate it.

            -Chris

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            • #7
              Another question that goes along with grounding requirements. My array will consist of 3 strings all on the same racking (all racking bonded). Due to conduit fill, I'll need to run 2 runs of 3/4 pvc from the rack to the inverter. I'll be using PV cable from panels to inverter.. no splicing or transitions. I ordered enough PV cable and don't want the hassle of more potential failure points/connections. Due to the jacket thickness of the PV cable, I'll have to use 2 conduit runs.

              Will each conduit run need its own EGC ran with the conductors even though the entire racking system is bonded? I wouldn't think so but wanted to verify.

              Comment


              • #8
                Originally posted by Mr4btTahoe View Post
                Again, thanks for all the information. Spent last night and a good chunk of the morning digging deeper into the code and I think the EGC is all that will be required for my specific installation as my installation falls into the "Ungrounded" category. If anyone can verify that.. I'd appreciate it.
                Chris are you saying you have a Transfomerless Inverter? If accurate you are on the right track. Mike answers your question directly in either video. Note when he says he thinks the EGC requirements are too large, but there is no harm in large than required wiringthat.

                But be warned there is Code and Best Practice. Those are two different things. Best Practice complies with code. Think of this. As I stated earlier EGC and GEC have completely different jobs. Example if lightning were to directly strike a panel, lightning is looking for earth. Both EGC and GEC wil get there but take different paths to get there.

                A GEC if you route it correctly down the outside of your house to the AC Service Ground or a Ground Rod that is bonded to your AC path takes a direct path outside of your home and bypasses your equipment.

                The EGC is routed with your PV wiring going through chokes along the way you created with raceways, junction boxes, passes through your home if routed that direction, your equipment into your main breaker panel, and exits to the AC Service ground. Catch that. You invited lightning into your home, equipment, and house wiring. Code permits you to do that as an option. Electrically it is SAFE. NEC is not lightning protection or a design guide. Just minimum electrical safety requirements.

                As for passing both AHJ and POCO, if the AHJ passes POCO will pass. The POCO i slooking for the GREEN INSPECTION TAG th eAHJ wil place on the meter and look to see if your Service is Grounded properly.

                Lastly there are two golden rules when dealing with Inspectors and Wifey. Live by them and you will be fine.

                1. Inspector and Wifey are always right.
                2. When Inpsector and Wifey are in error, refer to rule 1.

                Might try asking Inspector or Wifey how they like it first. Just be careful cause they can have an attitude if you do not already know, They will not tell you and expect to already know.
                MSEE, PE

                Comment


                • #9
                  So running an EGC back to the inverter and a GEC back to the AC ground electrode (not a separate electrode) would be the smart thing to do.. giving a faster path to ground and better protecting the equipment. That was my initial thought... the secondary electrode was a head scratcher.

                  The inverter I'm using is a SMA SB7.7 which is transformer-less.

                  Also, from what I'm gathering, we are still on the 2008 cycle if it matters.
                  Last edited by Mr4btTahoe; 04-18-2018, 03:42 PM.

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                  • #10
                    Also... I've heard it both ways as far as requiring an EGC in each conduit run. Some say no... some say yes.

                    What does the code say about it?

                    Comment


                    • #11
                      Originally posted by Mr4btTahoe View Post
                      Also... I've heard it both ways as far as requiring an EGC in each conduit run. Some say no... some say yes.

                      What does the code say about it?
                      EGC has to be ran with line conductors whether or not it is in a raceway. In fact the EGC can be the raceway and no ta wire at all. An EGC is a single conductor and requires no raceway. If one is use and metallic must be bonded to the raceway where it enters and exit to prevent magnetic choking.

                      The EGC and GEC have different functions. An EGC is there to facilitate OCPD operation. It must be ran tightly coupled with line conductors to eliminate magnetic inductance preventing the OCPD from operating quickly or failing completely. So whoever said [B]NO[/B] is full of poop. If the line conductors use a raceway, then there must be an EGC rans with them period.

                      A GEC is not ran with line conductors, and not required to be in a Raceway, just needs protected from physical damage. If a raceway is used it should be a non magnetic raceway like , PVC, or if magnetic materials are used like EMT, the GEC must be bonded at both ends to eliminate inductive magnetic CHOKING causing flash-overs to nearby objects. It would be like adding a big resistor.


                      Last edited by Sunking; 04-18-2018, 05:42 PM.
                      MSEE, PE

                      Comment


                      • #12
                        Thanks for the clarification. I'll run an EGC in both conduit runs. The GEC will be in PVC to protect if from damage... separate from everything else.

                        Comment


                        • #13
                          Originally posted by Mr4btTahoe View Post
                          Thanks for the clarification. I'll run an EGC in both conduit runs. The GEC will be in PVC to protect if from damage... separate from everything else.
                          Sounds like I am getting through. Just remember the 2 Golden Rules.

                          MSEE, PE

                          Comment


                          • #14
                            Amen to that! Lol. Thanks again.

                            All of my components will be here on LTL Monday... Inverter will be here tomorrow. Then the real work starts.

                            Comment


                            • #15
                              Originally posted by Mr4btTahoe View Post
                              Amen to that! Lol. Thanks again.
                              You are welcome.

                              With exercising both options, you are covered, but the AHJ may only accept one method, his own. Good thing is easy fix assuming you are not over looking something. Could be so simple and fast like removing a wire, you do it Johnny on the spot, you get your certificate and green tag. At worse schedule another inspection and pay another Inspection Fee. You know time and money. Some Inspectors are pretty laid back and willing to help, some are jerks and will only cite what code violations did not pass and make you figure it out. Not sure where you live but the economy and building biz is kicking butt and booming, so time is short for some Inspectors. Lots of money to be made right now.

                              My Son runs my biz now and he is so busy, he hired me under contract and I am sort of out of retirement again. Kind of nice get 20% profit plus of all my former company biz, plus a nice contract.

                              Good luck.

                              MSEE, PE

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