NEC 690.31(A)(2) For AC Modules?

[BarklieEstes]

Good morning,

We were tagged for a 690.31(A)(2) violation for a ground-mounted solar system using AC Modules. Though the DC conductors are readily accessible, I always thought that the NEC didn't apply to manufacturer wiring. Is that correct, or is it more nuanced than that?

Regards,
Barklie Estes

 

[jaggedben]

I think the inspector is being a jerk and you are basically in the right, but it may be a bit more nuanced than you want it to be.

I don't think the people who wrote the definition of AC modules imagined that manufacturers would produce them with exposed DC wiring. But I also don't know if UL 1741 ever defined an AC module (I seem to recall at some point way back that it hadn't). On the other hand I believe that when 690.31(A)(2) was written it wasn't imagined that single modules would quickly exceed 30V, so I think a microinverter systemwas intended to be exempt. The 30V is obsolete in my opinion, but I can't remember if there's been any talk of raising that. But it still says 30V.

What your argument might hinge on is whether Solaria really got the things listed as an AC module or if they are just using that for marketing. In my opinion it doesn't help that the datasheet lists DC specs and refers to the Enphase micro by its model. If it's really an AC module why did they list those DC specs? If the inspector already wants to be a jerk about this, I don't have a great slam dunk response for you.

 

[BarklieEstes]

Thanks for your thoughtful response. I agree that 30V seems low. 50v is the threshold for guarding in other parts of the code. I think I will put a PI in on that.

That's a good point. I am going to try to find out if it is a tested "product" or an untested "pre-assembly", which I agree could make the difference. I would support listing the DC specs either way. A 300W module with a 300W inverter is much different than a 400W module with a 300W inverter. Knowing the internals of a device is nice.

The violation is actually a 690.31(A) violation (under the 2017 NEC). That being the case and assuming it is an untested pre-assembly, wouldn't that conductor still fall outside the scope of a "pv source circuit", which is definitionally between a module and something else. It seems like dc leads are themselves part of a module and therefore not between a module and anything.

 

[jaggedben]

...

The violation is actually a 690.31(A) violation (under the 2017 NEC). That being the case and assuming it is an untested pre-assembly, wouldn't that conductor still fall outside the scope of a "pv source circuit", which is definitionally between a module and something else. It seems like dc leads are themselves part of a module and therefore not between a module and anything.

That argument might seem good on paper, but if you were stringing modules together at 600V would you really want to argue to an inspector that you don't have to guard the module leads, but only the field wiring connected to them? It's all the same PV or USE-2 wire (essentially).

 

[BarklieEstes]

It is. The only difference would be the location of field wiring, which could be anywhere versus module leads which are adjacent to the module cells. Like most protection considerations, you have to suppose about what is being protected against. I'm not sure what objects (shovel, machete?) could accidentally go through pv wire insulation that couldn't go through the electrified glass an inch or two behind it.

 

[jaggedben]

Weedwacker? Goat teeth? Kid with a pocketknife? I'm roughly half serious. But it's moot if you have to follow the rule.

 

[BarklieEstes]

I dialed up my PI for when the window reopens. We will see how it does:


690.31(A)(2) Where Readily Accessible: Where not guarded, PV system dc circuit conductors operating at voltages greater than 3050 volts that are readily accessible to unqualified persons shall be installed in Type MC cable, in multiconductor jacketed cable, or in a raceway.

Statement of Problem and Substantiation for Public Input

The word “a” is missing before raceway.

50 or 60 volts dc is the threshold for protection from unqualified persons in other parts of the code (examples: 430.232, 445.14, 665.5). In recent years, the 30v limitation imposed by 690.31(A)(2) has resulted in some inspectors, appropriately, requiring hazard fences around ground-mounted solar systems using microinverters since the module voltage exceeds 30v (a situation that was nonexistent when the 30v requirement was introduced in the 2008 NEC).

Microinverters have historically been used as a safer, price-similar alternative to the combination of high voltage dc systems and hazard fences. Increasing the maximum allowable voltage to 50 would encourage this safety practice while still being within a voltage regarded as safe in other parts of the code.