Do you need a disconnect at a ground-mounted array?

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wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
My position is simply that the language is too ambiguous with respect to PV systems. In any system with an inverter you would need to characterize the inverter as something that appears in the definitions of branch circuits and feeders, and it is not clear how to do so.
I'm trying to understand if I'm missing some complexity here, because to me it seems very straightforward. The PV panels are the "other power supply source" mentioned in the definition of Feeder. The inverter doesn't really enter into it, anymore than a non-SDS transformer would enter into it.

Since the original discussion is about outdoor PV conductors between two structures, let me ask you this: are the requirements for practical safeguarding different in the case of AC conductors versus DC conductors? Should article 225 apply in one case and not the other? If so, what is different about AC versus DC?

Cheers, Wayne
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
How is a PV system not an electrical source?
Code:
Separately Derived System. An electrical source, other than
a service, having no direct connection(s) to circuit conductors
of any other electrical source other than those established by
grounding and bonding connections. (CMP-5)
And in my 2017 Handbook the commentary:
Examples of separately derived systems include ... solar photovoltaic systems.
I don't have a 2017 handbook, but keep in mind that comments in the handbook are not code but someone's opinion of an interpretation of code.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
I'm trying to understand if I'm missing some complexity here, because to me it seems very straightforward. The PV panels are the "other power supply source" mentioned in the definition of Feeder. The inverter doesn't really enter into it, anymore than a non-SDS transformer would enter into it.

I don't think it's unreasonable to characterize the entire PV system as the power source and argue that 690 covers conductors within it. I'm not arguing that that's more reasonable than your position. But both positions result in some unreasonable consequences if followed through strictly logically.

Since the original discussion is about outdoor PV conductors between two structures, let me ask you this: are the requirements for practical safeguarding different in the case of AC conductors versus DC conductors? Should article 225 apply in one case and not the other? If so, what is different about AC versus DC?

Cheers, Wayne

I never said there was a blanket difference between AC and DC conductors, but there are many practical differences among the details. The original subject of this thread is a case in point. A typical 225.31 disconnect serves the purpose of deenergizing the structure. A disconnect for the PV output circuit at a ground mount array does not do that.
 

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
I don't think it's unreasonable to characterize the entire PV system as the power source and argue that 690 covers conductors within it.
Ah, that interpretation didn't even occur to me, that the inverter is the power source, not the PV panels.

(2014) 690.3 defines a "Photovoltaic Power Source" as "an array or aggregate of arrays that generates dc power at system voltage and current." I think that makes it clear that the array is the power source, so the conductors between the array and the inverter are feeders.

Cheers, Wayne
 

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
I don't have a 2017 handbook, but keep in mind that comments in the handbook are not code but someone's opinion of an interpretation of code.
Not just anyone's opinion.
Comments in the code handbook are debated as much as the code itself, editors have long meetings with CMP members and IAEI members. But yeah comments are not enforceable just like the 'fine print notes', but they are intended by the NFPA and IAEI to assist AHJ's in interpreting the code.

A typical 225.31 disconnect serves the purpose of de-energizing the structure. A disconnect for the PV output circuit at a ground mount array does not do that.
I think we all agree on this now, same as a 'generator house' the feeders exiting don't need a disconnect.
 
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