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Microinverter Grounding Requirements - Enphase vs Power One

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  • Microinverter Grounding Requirements - Enphase vs Power One

    Hello,

    I am looking at installing an 11 panel PV array using 250W Power One microinverters.
    As an electrical design reference I have Enphase's sample wiring diagrams.

    As far as I know, Enphase requires a GEC (Grounding Electrode Conductor) to run from the microinverters to a grounding electrode.

    I am not sure about Power One Microinverters' requirements. Will an EGC (Equipment Grounding Conductor) that runs from inverter to inverter (and also to the panels) be sufficient? This conductor would run back to the main service panel's grounding terminal bar.

    I cannot find any documentation that clearly shows what the requirements are. In Power One's manual it only makes mention of a EGC, which would indicate that no direct run to a grounding electrode is required.

    Thanks!

  • #2
    According to the NEC they would both require a GEC. They also will have a ECG which is built into the wiring harness.
    Depending on your AHJ the GEC can connect to the rails only and the modules and inverters are bonded to the rails with WEEB clips.
    This will pass code in some areas and not in others. Safest thing to do is use the bonding lug on the inverter (Enphase has one don't know about the other) and lugs on all the rails and modules. Don't forget about the bonding jumpers at all rail splices.
    NABCEP certified Technical Sales Professional

    [URL="http://www.solarpaneltalk.com/showthread.php?5334-Solar-Off-Grid-Battery-Design"]http://www.solarpaneltalk.com/showth...Battery-Design[/URL]

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    • #3
      You are required to have both.
      MSEE, PE

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      • #4
        Originally posted by Sunking View Post
        You are required to have both.
        ok, but by EGC I was not talking about the ground wire in the Trunk cable. The Power One manual shows a 6 AWG conductor (see attached picture) running to all inverters and they call it EGC (not GEC). Can this wire be connected only to the ground terminal bar in the main service panel (from where a GEC runs to the grounding electrode)?
        Attached Files

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        • #5
          Originally posted by Jaxx View Post
          ok, but by EGC I was not talking about the ground wire in the Trunk cable. The Power One manual shows a 6 AWG conductor (see attached picture) running to all inverters and they call it EGC (not GEC). Can this wire be connected only to the ground terminal bar in the main service panel (from where a GEC runs to the grounding electrode)?
          Well you may not like what I am going to say but it is 100% accurate. The manufacture drawing, or I should say, notation is incorrect and actually a bit alarming they made a technical error. What they are calling the EGC is actually a GEC. The EGC is ran with the line circuit conductors. The EGC is located inside the modular inter-connect cable.

          The #6 AWG GEC goes to as its name impiles, to the facility Ground Electrode System (GES)
          MSEE, PE

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          • #6
            Originally posted by Sunking View Post
            The #6 AWG GEC goes to as its name impiles, to the facility Ground Electrode System (GES)
            Thanks for the clarification.
            What about the possibility to elect installing in accordance with NEC 690.47(C)? This would mean the GEC and EGC are combined and could be terminated at the ground bus bar in the main service panel (?)

            Thanks a lot!

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            • #7
              Originally posted by Jaxx View Post
              Thanks for the clarification.
              What about the possibility to elect installing in accordance with NEC 690.47(C)? This would mean the GEC and EGC are combined and could be terminated at the ground bus bar in the main service panel (?)

              Thanks a lot!
              Check with your AHJ on that one. I have had them make me terminate the #6 GEC both ways. at the ground buss bar in the panel and splice irreversably to the GEC.
              NABCEP certified Technical Sales Professional

              [URL="http://www.solarpaneltalk.com/showthread.php?5334-Solar-Off-Grid-Battery-Design"]http://www.solarpaneltalk.com/showth...Battery-Design[/URL]

              [URL]http://www.calculator.net/voltage-drop-calculator.html[/URL] (Voltage drop Calculator among others)

              [URL="http://www.gaisma.com"]www.gaisma.com[/URL]

              Comment


              • #8
                Originally posted by Jaxx View Post
                Thanks for the clarification.
                What about the possibility to elect installing in accordance with NEC 690.47(C)? This would mean the GEC and EGC are combined and could be terminated at the ground bus bar in the main service panel (?)
                Problem is from what I can see is there is no way to access the EGC as they are enclosed in the modular wiring system for the inverters. That is why the manufacture is illustrating a separate GEC conductor. The EGC will go with the circuit conductors to the main panel, and the EGC bonded to the AC Panel ground buss. The GEC will bond to the facility GES aka AC service ground.
                MSEE, PE

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                • #9
                  Originally posted by Sunking View Post
                  Problem is from what I can see is there is no way to access the EGC as they are enclosed in the modular wiring system for the inverters. That is why the manufacture is illustrating a separate GEC conductor. The EGC will go with the circuit conductors to the main panel, and the EGC bonded to the AC Panel ground buss. The GEC will bond to the facility GES aka AC service ground.
                  And I could not irreversibly splice the GEC with the EGC (which is inside the cable, as you mentioned) in the rooftop junction box, and run a combined ground conductor from there to the ground bus bar in the main service panel?

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                  • #10
                    Originally posted by Jaxx View Post
                    And I could not irreversibly splice the GEC with the EGC (which is inside the cable, as you mentioned) in the rooftop junction box, and run a combined ground conductor from there to the ground bus bar in the main service panel?
                    No they are two separate things.
                    NABCEP certified Technical Sales Professional

                    [URL="http://www.solarpaneltalk.com/showthread.php?5334-Solar-Off-Grid-Battery-Design"]http://www.solarpaneltalk.com/showth...Battery-Design[/URL]

                    [URL]http://www.calculator.net/voltage-drop-calculator.html[/URL] (Voltage drop Calculator among others)

                    [URL="http://www.gaisma.com"]www.gaisma.com[/URL]

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                    • #11
                      EGC and GEC are two separate items and serve two different purposes.
                      MSEE, PE

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                      • #12
                        Quote Originally Posted by Jaxx "And I could not irreversibly splice the GEC with the EGC (which is inside the cable, as you mentioned) in the rooftop junction box, and run a combined ground conductor from there to the ground bus bar in the main service panel? "

                        Originally posted by Naptown View Post
                        No they are two separate things.
                        I would disagree based on this paper from John C. Wiles Jr. Oct 2012 (go to page 15-16)
                        http://www.solarabcs.org/about/publi...tudyreport.pdf

                        "Section 690.47(C)(3) in the 2011 NEC (similar to 690.47[C] in the 2008 NEC) combines the inverter AC EGC with the DC GEC into a single conductor and thereby uses less copper. "

                        What I did was bond and terminate the ECG from the inverter bus cable on one of the screws in the metal junction box on the roof. Then also bonded the GEC from the inverters/rails to the other screw in the junction box and continued this single 8AWG GEC/ECG unspliced to the main panel. This from my understand meets 2011 NEC code.

                        --
                        SharpT

                        Comment


                        • #13
                          Originally posted by SharpT View Post
                          I would disagree based on this paper from John C. Wiles Jr. Oct 2012 (go to page 15-16)
                          http://www.solarabcs.org/about/publi...tudyreport.pdf

                          "Section 690.47(C)(3) in the 2011 NEC (similar to 690.47[C] in the 2008 NEC) combines the inverter AC EGC with the DC GEC into a single conductor and thereby uses less copper. "

                          What I did was bond and terminate the ECG from the inverter bus cable on one of the screws in the metal junction box on the roof. Then also bonded the GEC from the inverters/rails to the other screw in the junction box and continued this single 8AWG GEC/ECG unspliced to the main panel. This from my understand meets 2011 NEC code.

                          --
                          SharpT
                          This is also what I had in mind. I read this somewhere some time ago, but couldn't find it to use in this discussion. Would this only be in conformance with NEC 2011 and NOT NEC 2008?

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                          • #14
                            The final authority is the inspector. What ever we say here means nothing it is up to his or her interpretation.
                            There are 2 rules (and I do not always follow them, Ask Sunking)
                            1- the inspector is always right.
                            2- If the inspector is wrong too bad refer to rule #1
                            NABCEP certified Technical Sales Professional

                            [URL="http://www.solarpaneltalk.com/showthread.php?5334-Solar-Off-Grid-Battery-Design"]http://www.solarpaneltalk.com/showth...Battery-Design[/URL]

                            [URL]http://www.calculator.net/voltage-drop-calculator.html[/URL] (Voltage drop Calculator among others)

                            [URL="http://www.gaisma.com"]www.gaisma.com[/URL]

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                            • #15
                              Originally posted by Naptown View Post
                              The final authority is the inspector. What ever we say here means nothing it is up to his or her interpretation.
                              There are 2 rules (and I do not always follow them, Ask Sunking)
                              1- the inspector is always right.
                              2- If the inspector is wrong too bad refer to rule #1
                              ok ok, but they can't and don't know everything. If you can show them proper documentation it can be a different story. PLUS I typically do the research, then go to the city and discuss with them what I have planned. This has worked so far.

                              For this topic though, I need some more help to figure out how this can be applied.

                              Can someone speak to the questions in my last post?

                              Thanks!

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