Ground mount

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JoeNorm

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We are installing a small ground mount array about 15 feet from a costumer's outbuilding. The outbuilding has an outdoor panel where we will connect the feed from the inverter. Originally I was going to locate the inverter and disco on the structure of the ground-mount but now I would like to run the DC conductors in a trench to the building and mount all the gear there. See any issues with that? Next question is about the GEC, should I connect it to the ground mount frame and run it to the inverter in the trench? I was planning to pound 2 ground rods at the array. Thanks
 
JoeNorm said:
We are installing a small ground mount array about 15 feet from a costumer's outbuilding. The outbuilding has an outdoor panel where we will connect the feed from the inverter. Originally I was going to locate the inverter and disco on the structure of the ground-mount but now I would like to run the DC conductors in a trench to the building and mount all the gear there. See any issues with that? Next question is about the GEC, should I connect it to the ground mount frame and run it to the inverter in the trench? I was planning to pound 2 ground rods at the array. Thanks
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Generally for a ground mount you are free to put the inverter at the ground mount or remote on another building. Keep in mind that depending on the specifics, code cycle, and interpretation of the wording, having the inverter on a building may trigger rapid shutdown requirements.

Assuming we are talking about transformerless inverters, I dont believe there is any requirement for a grounding electrode system at the array regardless of whether the inverter is at the ground mount or remote. Hopefully someone else can confirm nothing has changed in the new code cycles. In either case you just run an EGC with the inverter output circuit or the DC strings.
 
One issue is that Rapid Shutdown (690.12) is not required for a groundmount but is required if you have DC on or in a building. Your AHJ might cut you some slack if the DC comes straight out of the ground into the inverter, or they may not.

You do not need a GEC between the array and the inverter, only an EGC. Think of the array like a subpanel at detached building in this respect.
 
jaggedben said:
One issue is that Rapid Shutdown (690.12) is not required for a groundmount but is required if you have DC on or in a building. Your AHJ might cut you some slack if the DC comes straight out of the ground into the inverter, or they may not.

You do not need a GEC between the array and the inverter, only an EGC. Think of the array like a subpanel at detached building in this respect.
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and there is still no requirement for a grounding electrode system at a ground mount with DC only? If the ground mount was served with a feeder I would see one required.
 
electrofelon said:
and there is still no requirement for a grounding electrode system at a ground mount with DC only? If the ground mount was served with a feeder I would see one required.
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The ground mount still requires a grounding electrode system, as does any structure with a PV array. That's about all that 690.47 still requires.

As we've discussed, if the ground mount structure is supported by numerous metal posts in the ground, it's very well grounded and rods do nothing and are only necessary per the letter of the code.
 
jaggedben said:
The ground mount still requires a grounding electrode system, as does any structure with a PV array. That's about all that 690.47 still requires.

As we've discussed, if the ground mount structure is supported by numerous metal posts in the ground, it's very well grounded and rods do nothing and are only necessary per the letter of the code.
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Has an electrode always been required at a ground mount with only DC strings? I could have sworn there was no requirement in certain code cycle(s). 2014 690.47(D) has it. Did they do away with it in 2017 and bring it back in 2020? (I dont have either of those codebooks). Sort of just an academic question for me because I always feed a ground mount with a set up service conductors per 230.40 exception 3 and that of course requires a GES.
 
Hmmmm. The Rapid Shutdown idea has me a little nervous. The best part of a ground mount is not needing it. But the pipe does just come straight out of the ground and into the inverter. I think I will take my chances at this point. It is just a greenhouse, not a residence.

So I don't need the GEC. But do I still need the rods at the array? The five foot long ground screws obviously are better than a rod but just trying to satisfy the code.
 
electrofelon said:
Has an electrode always been required at a ground mount with only DC strings? I could have sworn there was no requirement in certain code cycle(s). 2014 690.47(D) has it. Did they do away with it in 2017 and bring it back in 2020? (I dont have either of those codebooks). Sort of just an academic question for me because I always feed a ground mount with a set up service conductors per 230.40 exception 3 and that of course requires a GES.
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A brief and paraphrasing summary as far back as my experience goes.
2008 All ground mount arrays shall have a grounding electrode.
2011 Above requirement deleted. GES could theoretically be at a different structure.
2014 - 2008 requirement comes back.
2017 - A structure that supports a PV array 'shall have' a GES. (Replaces previous requirements.)
2020 - A structure that supports a PV array 'shall utilize' a GES.

Honestly I hadn't really noticed the significance of that 2020 change until you asked. It appears that once again, the GES can be at another structure. Otherwise I don't know why they would change that phrasing.
 
JoeNorm said:
Hmmmm. The Rapid Shutdown idea has me a little nervous. The best part of a ground mount is not needing it. But the pipe does just come straight out of the ground and into the inverter. I think I will take my chances at this point. It is just a greenhouse, not a residence.

So I don't need the GEC. But do I still need the rods at the array? The five foot long ground screws obviously are better than a rod but just trying to satisfy the code.
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If one of the ground screws was ten feet in the ground then it would surely qualify as an electrode per code wording. Should two five foot screws qualify? In my opinion, yes. In your AHJs opinion, I can't say.
 
Is 250.52 and the 10 foot number specifically there to get the depth? In this case there is 40 feet of vertical structure in the ground, but nothing 10 feet deep.
 
jaggedben said:
A brief and paraphrasing summary as far back as my experience goes.
2008 All ground mount arrays shall have a grounding electrode.
2011 Above requirement deleted. GES could theoretically be at a different structure.
2014 - 2008 requirement comes back.
2017 - A structure that supports a PV array 'shall have' a GES. (Replaces previous requirements.)
2020 - A structure that supports a PV array 'shall utilize' a GES.

Honestly I hadn't really noticed the significance of that 2020 change until you asked. It appears that once again, the GES can be at another structure. Otherwise I don't know why they would change that phrasing.
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Thanks,. okay apparently it was 2011 I was thinking of where it disappeared but then came back.
 
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