Grounding wire to the inverter

[bosco]

Hi,
I'm building a ground mount system and my inverter has DC PV+ and PV- inputs and AC outputs (L1, L2, N and Ground). The inverter instructions are silent on the ground "input" coming from the panels and I do not see an "input" for ground. See attached picture IMG_8329.jpg

I've read online that I need to ground my panels/racking to a grounding rod, and all the line diagrams show a ground running to the inverter with the PV+ and PV-

However, like I mentioned, I do not see a ground "input" in the inverter wiring box (on the DC side). There is a screw on the exterior of the inverter, but that seems weird.

Any advice will be appreciated

thanks so much
Steve

[Mike90250]

You do not ground the inverter to the panels. You ground the inverter to the household service ground rod, The panel frames/racking also should go to a ground rod.

The panel frames are likely to experience a lighting strike, and in that case, you don't want your ground to go into your household service panel. It's sometimes possible to have a short direct run to it's own grounding rod, and then bond that rod to the main panel ground rod, with a heavy, protected, #4 solid wire.

Your installer should be able to guide you better than some semi-random hack on the internet, about code requirements in your area.
The Mike Holt videos (contributor to the NEC) have some good points in them https://www.youtube.com/watch?v=3vvvv5QVZoA

Mike Holt is much more of a grounding expert than , but he is not the AHJ in your area.

[bosco]

Thank you Mike
I watched the link you sent and have been reading a lot this morning.

Based on my reading, all my equipment needs to be grounded, so the panels/racking/pass through box and inverters (metal housing) need to be grounded.

Some interpretations of the NEC say that these all need to be connected to the same grounding rod at the array. Further, other articles say that the house grounding rod and array grounding rod should be connected.

If it helps - for context:

-ground mount arrays ~225' from inverters (two) that are next to house panel/PG&E meter
-I ran a single, bare copper 6awg wire in the PVC conduit (with DC + and - cables) between arrays and inverters
-I've connected all my racking and panels with a 6awg bare copper to a grounding rod driven 10' deep at the arrays

Based on my reading this morning...
1. My panels, racking, junction box at the array, and inverters should be connected/bonded to the same grounding system that terminates at the array grounding rod.
2. I need to somehow connect my array grounding to the house grounding rod....which seems to be in direct conflict with your advice of "keeping the lightening" away from the house. Here's the link that advises connecting the grounding - http://www.weatherimagery.com/blog/h...els-correctly/

Any thoughts or advice would be appreciated
thanks
Steve

[Mike90250]

I think you use 2 grounding rods, 1 at house, one at array, and then use a heavy copper wire to connect/bond the ground rods together to avoid "Step Potential" electrocution, This does not bring the array ground into the house panel before it sees at least 1 ground rod.

[bosco]

Hi Mike,
What do you think of this-

Bond the array grounding bar to the house grounding bar using #4 copper, and
-connect/permanently crimp panels/racking/metal junction box and metal inverter housing to this #4 along the way...

Thanks again for your help
Steve

[Mike90250]

It's not what I think, it's what you can defend to the inspector. But that plan sounds OK to me, if those are /exceed the wire gauge specs code calls out.

[bosco]

of course - totally understand
My inspector is actually pretty weak so I'm more concerned I "get it right" because he won't catch it if I don't
Thanks again Mike