Roof Top Grounding Sanity Check Please

MrM1

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I have read everything I can find about roof top panel grounding. I have watched the Mike Holt video several times. I have read conflicting interpretations of the video and of roof top panel grounding in general on different forums. Owners manuals from Schneider and Midnite solar are also someone unclear. So before I start I thought I would ask one more time for clarity.

I get confused as to if there should be a separate grounding electrode (rod) for the racking and panel frames run off the roof down the side of the house, separate from the main panel house grounding conductor and grounding electrode (rod) - creating 2 grounding points for the house, 1 for the array, 1 for the main panel

... OR ...

If the panel frame/racking ground should come into the house, to the inverter / SCC / Switchhgear and go from the inverter with the AC in/out ground wire (equiptment grounding conductor) back to the main breaker panel's neutral/ground bond, connected to the grounding electrode conductor and on to the main grounding electrode (rod) for the house. So that there is only 1 grounding point for everything.

MY PLAN: from what I can gleam, (and check my sanity here) is to ...

1. bond the racking and panel frames to a solid copper #6 ground wire and go into the attic to my combiner box.
2. Grounding the combiner box housing with that racking ground and then run a ground down with the combined PV (+) and (-) to the inverter and SCC to be bonded at a busbar with the inverter chassie , SCC chassie, and the AC in/our grounds going back to the main breaker panel of the house
3. At this point, (already installed in the house) at the main panel the neutral and all equipment grounds (including my array, inverter, and SCC chassies) are bonded 4. 4. from that busbar in the main panel there is a whole house grounding electrode conductor (main ground wire) going to the main panel grounding electrode (rod) for the whole house.

Thus giving me one grounding rod point (actually I have two 6 foot apart and bonded underground) for the whole house, all AC circuits, all equipment grounding (ie. inverter case, charge controller, panels, racking, etc) for the entire set up.

I have thought and thought, read and read, and this is what seems to be what I understand of how it needs to be done. My understanding of what Mike Holt advocates is that the NEC allows for a separate grounding electrode (rod) for the array and racking, but that he does not believe this is correct.

Am I anywhere near on track?
 

FilterGuy

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I get confused as to if there should be a separate grounding electrode (rod) for the racking and panel frames run off the roof down the side of the house, separate from the main panel house grounding conductor and grounding electrode (rod) - creating 2 grounding points for the house, 1 for the array, 1 for the main panel
An Emphatic NO!!! Do not have a 2nd/separate Grounding electrode!!! The NEC allowed it but it is a bad thing to do.

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If the panel frame/racking ground should come into the house, to the inverter / SCC / Switchhgear and go from the inverter with the AC in/out ground wire (equiptment grounding conductor) back to the main breaker panel's neutral/ground bond, connected to the grounding electrode conductor and on to the main grounding electrode (rod) for the house. So that there is only 1 grounding point for everything.
This is a much better plan.
MY PLAN: from what I can gleam, (and check my sanity here) is to ...

1. bond the racking and panel frames to a solid copper #6 ground wire and go into the attic to my combiner box.
2. Grounding the combiner box housing with that racking ground and then run a ground down with the combined PV (+) and (-) to the inverter and SCC to be bonded at a busbar with the inverter chassie , SCC chassie, and the AC in/our grounds going back to the main breaker panel of the house
3. At this point, (already installed in the house) at the main panel the neutral and all equipment grounds (including my array, inverter, and SCC chassies) are bonded 4. 4. from that busbar in the main panel there is a whole house grounding electrode conductor (main ground wire) going to the main panel grounding electrode (rod) for the whole house.
This works fine. However, if possible, I would run the ground from the combiner box directly to the grounding electrode. Alternatively, do a non-reversible splice to the grounding electrode conductor. Running the ground through the breaker panel is fine if you can't bypass the breaker panel. I just like the idea of keeping any pulse on the Panel Frame Grounding out of the main breaker panel.
 

MrM1

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So As Long As It Runs From The Combiner To The Main Grounding Electrode Of The House, it does not have to go thru and be bonded to the neutral in the main service panel? But It Should have a irreversible slice crimp as it joins the GEC below the main service panel?

What about a second "acorn" type connector on the main grounding electrode next to where the main GEC connects to the ground electrode? Would that suffice? (in other words there would be 2 acorn connectors on the grounding electrode, one from the main service panel and one from the array.)
 
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FilterGuy

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Or will an "acorn" type connector on the main grounding electrode next to where the main GEC connects to the ground electrode suffice? (in other words there would be 2 acorn connectors on the grounding electrode, one from the main service panel and one from the array.
Yes, a second Acorn should suffice but..... If the install is going to be inspected, make sure the inspector can see the connection before it is covered up.


Your description and questions make me wonder if you have all of the grounding for the building that is required.....

* All Grounding electrodes must be tied into the grounding system. (This includes what I call 'unintentional' grounding electrodes)
* The resistance to earth must be 25 ohms or less.

* A single 8 foot grounding electrode is often (usually?) Not sufficient to meet the 25ohm grounding requirements. Some inspectors don't even measure....they just require 2 rods if that is the only grounding for the structure. (BTW: To be effective multiple 8' rods must be at least 8ft apart. If they are right next to each other, it is not much better than a single rod)
* All of your metal pipes are supposed to be tied to your grounding.
* On any new construction, the Rebar in concrete is supposed to be tied to your grounding (This turns out to be a really good way to tie to earth).

It is allowed to bring separate grounding electrode conductors from each grounding electrode up into the breaker box. However, the best way to tie all of the electrodes into the grounding system is to daisy chain between the various electrodes with grounding electrode jumpers and bring a single grounding electrode conductor up to the main breaker panel. This keeps any pulse between the electrodes away from the breaker box.
 

JoeHam

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FWIW I have a small system running a boat lift and some times a small refrigerator at a boat house.

Our AHJ passed me with one 6 AWG ground wire from the roof panels and another 6 AWG ground wire from the breaker box to a single acorn on a single ground rod. He also checked that the inverter was bonded to the breaker box ground connection.

The ground from the roof runs on the exterior of the structure which I believe is best in case of a lightning strike. You wouldn’t want that through your attic IMHO.
 
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MrM1

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@FilterGuy I do have all pieces in place, except the new array expansion on the roof.

All existing equipment is bounded back to the main panel neutral / ground bond and on out to the grounding electrode.

At few years ago I added a 2nd grounding electrode 8 ft from the main electrode. (Sandy soil). The only issue is there is not a single continuous grounding electrode conductor, there is a jumper or splice underground connecting the primary and secondary electrode. I assume That would be an issue if I were to be inspected.

I am presently adding on to my array. And have been kicking it around for months . But now the new panels have arrived and before I start I want to do it as correct as possible.

I also have the option to run the equipment grounding conductor from the combiner box directly to the main grounding electrode. The existing array grounding conductor goes through the main panel, but as you suggest, when I install the new array I will change that.
 
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