AC microinverter Solar and romex

[dm9289]

I seen an odd install and I could not find a code ref to justify in my mind.
2 strings of micro inverters
Junction box on end of 1 string hole drilled into attic from the roof box 10-2 romex runs thru interior of attic and penetrates roof again to combine with other string in roof box, then goes to flex that runs thru attic converts to emt at side exit of house in elbow.

I know with DC 690.31(G)(2) you would need conduit or protection, but whats bothering me is I cant find an AC code ref that says this is no good.
Help.

I know the microinverters should offer some protection before the combiner but the romex running thru the attic bothers me maybe im just picky. I should not look at these things I drive myself nuts.

 

[TallTimber]

I dont see an issue with the romex as long as it is sized for 125% of the maximum output of the microinverters as combined. 10-2 romex should be good for up to a ~7kW system as a ballpark number.

 

[jaggedben]

...

I know with DC 690.31(G)(2) you would need conduit or protection, but whats bothering me is I cant find an AC code ref that says this is no good.
Help.
...

Because there isn't such a code reference. It's basically fine. And you shouldn't be viewing a micro-inverter circuit as presenting any danger that other AC circuits do not.

The only thing is if they brought the 'romex' onto the roof such that it's clearly in a wet location, then if the 'romex' is NM cable you can tell them they should have used UF instead.

 

[dm9289]

Because there isn't such a code reference. It's basically fine. And you shouldn't be viewing a micro-inverter circuit as presenting any danger that other AC circuits do not.

The only thing is if they brought the 'romex' onto the roof such that it's clearly in a wet location, then if the 'romex' is NM cable you can tell them they should have used UF instead.

Thank you for your input. It does penetrate roof but enters thru back of box. I have been using a few resources to understand solar better and I’m having a lot of confusion. Hopefully I’ll eventually put the puzzle together

 

[Electrical Geek]

Because there isn't such a code reference. It's basically fine. And you shouldn't be viewing a micro-inverter circuit as presenting any danger that other AC circuits do not.

The only thing is if they brought the 'romex' onto the roof such that it's clearly in a wet location, then if the 'romex' is NM cable you can tell them they should have used UF instead.

It's my understanding that any pipe run outside of a house is a damp location, but a junction box isn't. We do this all of the time and haven't been called on it yet.

 

[jaggedben]

It's my understanding that any pipe run outside of a house is a damp location, but a junction box isn't. We do this all of the time and haven't been called on it yet.

It's one of those things lots of people do all the time even though the code doesn't allow it, or at least can be read that way.

 

[don_resqcapt19]

It's one of those things lots of people do all the time even though the code doesn't allow it, or at least can be read that way.

300.9 was purposely written specifically to exclude boxes unlike 300.5(B) that includes boxes and enclosures in the ground. The concern was not to prohibit NM from being stubbed out to boxes in or on the exterior wall.
(I was the author of 300.9)

 

[jaggedben]

Good to know.

The issue with 'roof boxes' in solar (or other roof stuff) is between the two typical ways to get wiring to a box on the roof. One way is to use a (more expensive, longer lead time) specialty box with a built in flashing, such as a Soladeck or Q-box. No problem to bring romex directly into that from the attic. The other typical way is to stub conduit through the roof with a cone flashing and rain collar, and then stick the box on top of it or LB to a box some distance away. With this second method it's technically a violation to use NM in the conduit stub, even if it's just a foot or so. UF makes the second method compliant. (So does pulling THWN and using, say, FMC in the attic.)

 

[JoeNorm]

We used Romex all the time with Enphase systems. Often, like Jaggedben said, you end up with an LB and maybe a very short section of pipe coming out the roof to get to the Jbox. It’s a violation to have the Romex in this 1 foot section but I would usually do it anyway.

 

[wwhitney]

We used Romex all the time with Enphase systems. Often, like Jaggedben said, you end up with an LB and maybe a very short section of pipe coming out the roof to get to the Jbox. It’s a violation to have the Romex in this 1 foot section but I would usually do it anyway.

Doesn't seem so hard to put a junction box on the attic side of the nipple penetrating the roof, and change over the wiring from NM in that junction box. Avoids the 300.9 violation.

Cheers, Wayne

 

[jaggedben]

Doesn't seem so hard to put a junction box on the attic side of the nipple penetrating the roof, and change over the wiring from NM in that junction box. Avoids the 300.9 violation.

Cheers, Wayne

Um, splicing wires in a j-box while lying sideways in a tight attic is definitely hard, and you're lucky if you come down out of the attic with all your tools. Least easy option. Then there's vaulted ceilings in new construction, i.e no attic and not an option.

 

[BackCountry]

Um, splicing wires in a j-box while lying sideways in a tight attic is definitely hard, and you're lucky if you come down out of the attic with all your tools. Least easy option. Then there's vaulted ceilings in new construction, i.e no attic and not an option.

After trying out a bunch of boxes, we’ve settled on EzSolar. If you haven’t tried one yet, try it for sure. It’s better and cheaper than a soladeck, and the tile version is great too.

We use one 10-2 NM-B per Enphase string, and either fish down to the IQ combiner or transition to EMT at the soffit with an LB and a short nipple or section of EMT with a bushing on the end. Even easier now with the Milwaukee M12 NM stapler.

2x 10-2 max for 3/4”, 4 for 1”, and tie in with an LR or LL to a close nipple so you have enough threads exposed for a ground bushing.

I’d say we run about 1/20 with exposed conduit on the roof, most are ran in the attic this way so there’s no roof conduit.

At one point I did find 10/4, which would have been nice for two string pulls, but it’s pretty rare.