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Confused by array grounding

I like the simplicity of that, but just thought of something else. If I'm on the roof of the barn where the solar panels are and there is a fault in the inverter, for example, that causes the panel frame to be energized, wouldn't it be better if the metal roof were NOT grounded? Note that my panels will be mounted with treated wood tiltable frames so as long as it's not raining, the panels will be electrically isolated from the metal roof. As far as I can tell, using wood is okay since the panels will actually be located on an extension of the barn which is in fact a carport structure. Furthermore, my AHJ says they do not inspect the solar panel mountings.

And finally, I plan to individually ground each panel with the EGC I just ran to the house so for the panel to get energized, this ground wire would also have to fail.
We can't control every possibility. We just have to cover all that we can.
 
I like the simplicity of that, but just thought of something else. If I'm on the roof of the barn where the solar panels are and there is a fault in the inverter, for example, that causes the panel frame to be energized, wouldn't it be better if the metal roof were NOT grounded?

If you were standing on the ground leaning against the metal siding, and metal siding does have contact to PV frames, current could flow through you to earth, then back to the inverter. You would have to try hard to ensure frames and siding were isolated, can't count on paint as insulator but can't count on contact either.

People have found PV frames had AC coupled to it from the inverter, got shocked. Or, frames were grounded but inverter wasn't (on RV), got shocked by RV frame.

And finally, I plan to individually ground each panel with the EGC I just ran to the house so for the panel to get energized, this ground wire would also have to fail.

That is the key to electrical safety, EGC back to inverter chassis which is grounded, keeps PV frames from having either DC or AC relative to earth. So long as that EGC is grounded somewhere.
 
Done! After installing, I checked the resistances all around the barn and at the roof and all those panel screws do a better job of creating bonded connections than I thought. I caulked the area around the ground lug afterwards to prevent water from getting inside.

One thing I learned is that the ground, even wet makes a poor conductor. Kilo-ohms range with two probes inches apart and between the ground rod and ground, it was in the meg-ohms.

Thanks once again for the sage advice.

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I am still confused after reading all this. to ground my array, would I need a third wire ( the pv positive and negative wire are the other two) running back to the AIO as ground? All the grounding has to be done into the existing home grounding rod? It is not correct to just ground the array to its own rod outside? I want to run my system detached from the grid itself in a sub panel. I would have to ground everything to that grounding rod in the main system. would that cause any interference with my main panel or the grid if the power went out?
 
I am still confused after reading all this. to ground my array, would I need a third wire ( the pv positive and negative wire are the other two) running back to the AIO as ground?

Yes
All the grounding has to be done into the existing home grounding rod?

Yes. One can use a busbar in different locations to combine the EGC back to the existing ground rod.

It is not correct to just ground the array to its own rod outside?

No, I'll explain why. Anything that can carry current such as a metal PV frame has to be connected by an EGC to the system ground. This provides a low impedance path back to source of power. This low impedance path is what causes a circuit breaker to trip opening the circuit. The EGC also provides a zero voltage reference point.

An auxiliary ground rod is allowed but reality is it does not provide any ground fault protection because it is not a low impedance path back to source.

Watch the video in this post.

I want to run my system detached from the grid itself in a sub panel. I would have to ground everything to that grounding rod in the main system. would that cause any interference with my main panel or the grid if the power went out?
It still is required to have a ground rod at source (an inverter for example) and the N-G bond. An EGC will still run back to the system grounding as you have a power source that can energize anything metal. The purpose of the EGC is for ground fault protection. Leave the N-G bond in your main panel and do not bond the subpanel.

No, it will not cause interference with the main panel should grid power go down.
 
I am still confused after reading all this. to ground my array, would I need a third wire ( the pv positive and negative wire are the other two) running back to the AIO as ground? All the grounding has to be done into the existing home grounding rod? It is not correct to just ground the array to its own rod outside? I want to run my system detached from the grid itself in a sub panel. I would have to ground everything to that grounding rod in the main system. would that cause any interference with my main panel or the grid if the power went out?
Yes, run a ground wire (green if insulated) from your panel frames (all bonded together), back to the AIO, and bond this ground wire to your house ground system. Could be in the main panel, could be in a junction box, or could be at the house ground rod.

A separate ground rod in the earth does nothing to protect you from the AC faults that could occur in the inverter.

Solar panel grounds must be 6 AWG or thicker, and use approved lugs that bite into the aluminum (panel or approved mounting frame)
Can use a smaller ground wire back to the house ground system if in conduit (10 AWG is good, depends on your PV current).
 
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Yes, run a ground wire (green if insulated) from your panel frames (all bonded together), back to the AIO, and bond this ground wire to your house ground system. Could be in the main panel, could be in a junction box, or could be at the house ground rod.

A separate ground rod in the earth does nothing to protect you from the AC faults that could occur in the inverter.

Solar panel grounds must be 6 AWG or thicker, and use approved lugs that bite into the aluminum (panel or approved mounting frame)
To be clear, only the exposed ground. The wire running back to your service does not have to be 6 AWG.
 
Yes


Yes. One can use a busbar in different locations to combine the EGC back to the existing ground rod.



No, I'll explain why. Anything that can carry current such as a metal PV frame has to be connected by an EGC to the system ground. This provides a low impedance path back to source of power. This low impedance path is what causes a circuit breaker to trip opening the circuit. The EGC also provides a zero voltage reference point.

An auxiliary ground rod is allowed but reality is it does not provide any ground fault protection because it is not a low impedance path back to source.

Watch the video in this post.

It still is required to have a ground rod at source (an inverter for example) and the N-G bond. An EGC will still run back to the system grounding as you have a power source that can energize anything metal. The purpose of the EGC is for ground fault protection. Leave the N-G bond in your main panel and do not bond the subpanel.

No, it will not cause interference with the main panel should grid power go down.
Thanks for all of these answers. Very very helpful!!
 
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