690.6 AC Module System Exemption

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BarklieEstes

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Location
Richmond, VA
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Master Electrician
The 2020 NEC expanded a dc circuit exemption in 690.6(A) so that it applied not just to AC modules, but also to AC module systems, which according to the definition is a system comprised of AC Modules.

At the risk of stating the obvious, there are no dc circuits between AC modules. Thus, I am totally confused about what this code change was about. Does anyone know what you are now allowed to do that you couldn't do before?

Regards,
Barklie Estes
 
Well, the definition of an AC module system was also new in the 2020 code, so I think it's just expanding the language to cover that. I presume an AC module system was something newly layed out in the product standards, but I don't know how they are 'evaluated' or if anyone claims to have produced such a thing. I haven't looked at the revision info for clues.
 
Thanks for the response. I looked at the revision info, which isn't very helpful. The "or AC module systems" language was added by CMP-4, without any acknowledgement that applying a "PV source circuit" exemption to wiring between AC modules (i.e. ac wiring) is pointless. It makes me wonder what the actual intent was.
 
I could be wrong, but it might have to do with some AC modules having exposed DC conductors. When I first saw the definition of AC modules, I thought there would be no exposed DC conductors. But then I started seeing some products that claimed to be listed AC modules with exposed DC conductors between the module and micro.
So the rule you're asking about may be intended to clarify that those conductors are covered by the listing and not the code.
 
Perhaps- although, as worded, the AC module definition includes the totality of its components, one of which being the module-to-inverter dc wiring. Adding to the confusion, the leads of a Module (ac or dc) would already be excluded by the Code structure since they're not a "wiring method" but rather an "integral part of equipment" [300.1(B)].

Pretty much any 1:1 microinverter system doesn't include the type of field wiring that falls under 690.31(A), which covers wiring "from modules" (a factory-installed lead is part of the module itself). Strictly speaking, plugging one piece of UL-listed equipment into another is not a wiring method. I've never had an inspector try to fail one of our SolarEdge Synergy installations, even though the factory-installed cable there are running at 400Vdc.

Not that I could write code any better. Capturing safety intent into words on a page is an astonishingly difficult task in practice.
 
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