# Ground Mount PV System Grounding



## cdcengineer (Nov 24, 2010)

Anyone have a clear understanding of how to apply the NEC requirements of article 690.45 thru 690.47?

We have a ground mount 112kW grid-tied PV array which consists of (10) rack mounted strings. The strings are (12) 235w panels, mounted (4) strings per rack. So essentially, we have 48 panels per rack, times (10) racks or (480) total modules.

The code requires that we run an EGC. This conductor must be #6 if not run in a raceway and subject to physical damage (NEC 690.46).

We are also required to have grounding electrode (or is it electrodes) for the array. It's my opinion that the multiple (48) module racks are only one array as they tie into a single 100kW inverter at 480V-Y.

It's always a point of contention with contractors and/or installers regarding what they have to install. I'm hoping the 2011 NEC will address this in more detail, but I haven't ordered my new code book just yet.

It's my understanding that we are required to provide an additional grounding electrode per NEC 690.47(D) as the array is not w/in 6' of the premises electrode. This #6 AWG GEC will tie in at the inverter which will be bonded to the AC side EGC (EGC &amp; Bond can be one &amp; the same per 690.47©(3)). I also believe that this #6 AWG GEC shall be connected to each array frame (which in this case I interpret this as each rack), and then tie to the additional electrode. I am proposing that the contractor installs a #2 ground ring per 250.52(4).

I am on or off track here folks? Does the #2 ground ring need to be buried? Any thoughts and input are greatly appreciated.

I've corresponded with installers and engineers throughout the Rocky Mtns, CA &amp; Oregon, and each person has a differing opinion.

Input is greatly appreciated.


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## ndekens (Dec 21, 2010)

From what I gather you are looking for; you will need to tie the entire array together with #6 bare copper wire and run this to either the service ground or a dedicated ground rod that is installed at the inverter and at least 6ft from the existing ground rod. The DC and the AC side of the system can share ground point according to the 2008 NEC.

See the attached photos of a 20KW system that I designed. If you can see I have the bare copper ground running from the rack into the combiner box then through the conduit system to the ground rod down the side of the building.




In the inverter picture you can see the new ground rod installed at the right of the inverter which is well away from the incoming utility ground.






cdcengineer said:


> Anyone have a clear understanding of how to apply the NEC requirements of article 690.45 thru 690.47?
> We have a ground mount 112kW grid-tied PV array which consists of (10) rack mounted strings. The strings are (12) 235w panels, mounted (4) strings per rack. So essentially, we have 48 panels per rack, times (10) racks or (480) total modules.
> 
> The code requires that we run an EGC. This conductor must be #6 if not run in a raceway and subject to physical damage (NEC 690.46).
> ...


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