Conductor Sizing and OCP for a AC Solar Panel

[tallgirl]

In point of fact, it would probably be nuisance tripping.

Not likely. The time curve on the breaker should be long enough at 18 amps that the sun will be headed on down before any thermal trip happens. Put ten of them on a two axis pole-mounted tracker and then maybe.

 

[Smart $]

I believe this is the document you're looking for --...

No, I'm not looking for that document. I've already seen it. IMO, all it adds to this discussion is just more rhetoric. If there is something in that document which truly substantiates your view, please elaborate.

 

[tallgirl]

No, I'm not looking for that document. I've already seen it. IMO, all it adds to this discussion is just more rhetoric. If there is something in that document which truly substantiates your view, please elaborate.

Really, I'd love to say more, but I think that the best thing I can do is encourage you to contact Intertek if you feel they are misrepresenting their product.

 

[Smart $]

Not likely. The time curve on the breaker should be long enough at 18 amps that the sun will be headed on down before any thermal trip happens. Put ten of them on a two axis pole-mounted tracker and then maybe.

Perhaps... perhaps not. If the location of the breaker enclosure is also in the sun, and non-ventilated or otherwise not cooled, and the breaker is a typical thermal magnetic type, the enclosure's internal ambient temperature will "accelerate" the trip curve.

Regardless, the concept behind this forum is Code compliance... not "When can I disregard Code compliance and get away with it?"

 

[Smart $]

Really, I'd love to say more, but I think that the best thing I can do is encourage you to contact Intertek if you feel they are misrepresenting their product.

I'll likely never use their product. Ultimately, I can think of much better things to waste my time on. In fact, I've wasted too much of that time discussing this issue with you

 

[tallgirl]

Perhaps... perhaps not. If the location of the breaker enclosure is also in the sun, and non-ventilated or otherwise not cooled, and the breaker is a typical thermal magnetic type, the enclosure's internal ambient temperature will "accelerate" the trip curve.

Regardless, the concept behind this forum is Code compliance... not "When can I disregard Code compliance and get away with it?"

Thus far you've really not demonstrated that the manufacturers instructions as applied to an ETL certified product is not Code compliant. We've had a lot of naive discussions about why some wire that's not a #12 whatever-the-heck can be used to connect to some other device that's ETL certified and a #12 =somewhere= with a 20A OCPD.

Again, I'd love to say more, and would be more than willing to discuss my personal thoughts over a beer in a nice beer consuming location, but all I've seen from you and others is conjecture. Y'all aren't an ETL. Intertek is. Take up your objections with them.

 

[tallgirl]

I'll likely never use their product. Ultimately, I can think of much better things to waste my time on. In fact, I've wasted too much of that time discussing this issue with you

I'm 100% certain I won't! I have a behind-the-fence array at the house, another on my roof and a bunch of arrays on the roof at the office and I'm very happy with what I've got

 

[Smart $]

Thus far you've really not demonstrated that the manufacturers instructions as applied to an ETL certified product is not Code compliant. We've had a lot of naive discussions about why some wire that's not a #12 whatever-the-heck can be used to connect to some other device that's ETL certified and a #12 =somewhere= with a 20A OCPD.

Again, I'd love to say more, and would be more than willing to discuss my personal thoughts over a beer in a nice beer consuming location, but all I've seen from you and others is conjecture. Y'all aren't an ETL. Intertek is. Take up your objections with them.

You're still missing the point... :thumbsdown:

The only indication that Intertek is involved from what I can tell is the following excerpt from the mentioned White Paper...

PVAC Modules are electronically current limited to 1.8 amps and will not under any circumstances generate more than 1.8 amps each, irrespective of the available input wattage. This current limit is certified by Intertek, a Nationally Recognized Testing Laboratory authorized and certified by the Occupational Safety and Health Administration, a federal agency of the United States government.

I cannot take this to mean anything beyond what it says... Intertek certifies the Exeltech AC Module to have a max' output current limited to 1.8A.

Show me where Intertek or any other recognized ETL certifies 10 Exeltech AC Modules may be paralleled on Exeltech's Home Run Cable (the #12 you are referring to) and connected to any 20A breaker. I doubt very, very much you can. Your likely response, if any at all, will be just one more episode of side-stepping the issue. :happyyes:

 

[GoldDigger]

ifies 10 Exeltech AC Modules may be paralleled on Exeltech's Home Run Cable (the #12 you are referring to) and connected to any 20A breaker. I doubt very, very much you can. Your likely response, if any at all, will be just one more episode of side-stepping the issue. :happyyes:

It seems to me that since there are two different chains of reasoning which appear to be consistent with the Code but which reach contradictory results, the only way to conclusively resolve the problem is to get a ruling specifically on the issue, rather than a statement from the manufacturer. The fact that Exeltech does not have a 10AWG Home Run Cable (and the connecting devices designed for 12AWG probably would not work with it if they did) makes Exeltech's statement self-serving and not fully persuasive.

 

[jaggedben]

It seems to me that since there are two different chains of reasoning which appear to be consistent with the Code ...

I disagree. Exeltech's whitepaper simply ignores certain relevant section of the code, as I detailed above. Ergo their reasoning is not consistent with the Code.

 

[tallgirl]

I disagree. Exeltech's whitepaper simply ignores certain relevant section of the code, as I detailed above. Ergo their reasoning is not consistent with the Code.

You disagree? Do you disagree that there is a disagreement, because there very certainly IS a disagreement.

Manufacturers produce whitepapers all the time. Depending on my vacation schedule (and whether or not I take one ...) I'm hoping to write a few white papers. But I do not confuse white papers for manufacturers specifications which state that the maximum OCPD rating is 20A. Nor do I think that manufacturers just write stuff, put their name on it, and hope for the best.

At this point I truly think the best thing to do is contact Intertek and probably Exeltech.

 

[tallgirl]

Your likely response, if any at all, will be just one more episode of side-stepping the issue. :happyyes:

Side-step? No, I gave up. If you have any serious questions, and aren't just badgering me for fun, I'd suggest you contact Intertek or Exeltech.

I work for a microinverter manufacturer that isn't Exeltech. I'd prefer not to defend Exeltech's product and have tried to limit my comments to stating what I thought was reasonably common knowledge -- products are installed based on the manufacturer's instructions, not the musings of people on an Internet forum. I was taught that if I had questions, I contacted the manufacturer for clarification, I didn't ask my buddies on an Internet forum for their opinion.

And on that note, I'm done for the evening. I have to head to the house and deal with customers of my own and maybe watch some history documentaries on Netflix. And probably even have a beer.

 

[jaggedben]

You disagree? Do you disagree that there is a disagreement, because there very certainly IS a disagreement.

I disagreed with Goldigger's statement that there are two different chains of reasoning that are consistent with the code. Exeltech's whitepaper is not consistent with the code, in my opinion.

It is worth noting that the whitepaper does not even appeal to 240.5(B)(2), as some have done in this thread. The extent of the argument in the white paper is this:
"NEC 690.8 (?Circuit Sizing and Current?) focuses on PV source and output circuit currents, and stand-alone inverter input circuit
currents. Inasmuch as AC Modules have no exposed DC circuits, this section is not applicable to PVAC Modules."

The word 'focuses' serves as a nice little bit of obfuscation, intentional or not, that serves to ignore those parts (mainly 690.8(A)(3)) that apply to inverter output circuits. I don't know where the writer gets the notion that these clauses focus on stand-alone inverters.

It really just seems as if either the writer was not very familiar with the code, or if he was hoping that the reader would not be.

At this point I truly think the best thing to do is contact Intertek and probably Exeltech.

Well if I were actually installing this stuff, or if I were an AHJ inspecting it, I might do that. I think our OP's decision to following 690.8 regardless of the Helios instructions is a wise one.

 

[jaggedben]

... products are installed based on the manufacturer's instructions, not the musings of people on an Internet forum. ...

Products also need to be installed according to applicable Code. That's the point of this forum.

 

[tallgirl]

Products also need to be installed according to applicable Code. That's the point of this forum.

Totally agreed. However, "maximum current" is NOT always a number you can simply plug into an ampacity calculation. The maximum output current of an OutBack GVFX 3648 is 70 amps. The maximum OCPD is 50 amps.

 

[Smart $]

Side-step? No, I gave up.

Just full of contradictions, eh...

If you have any serious questions, and aren't just badgering me for fun, I'd suggest you contact Intertek or Exeltech.

Advisement most certainly taken under consideration... as I certainly will not be asking you any questions on this matter.

I work for a microinverter manufacturer that isn't Exeltech.

I don't care in the slightest who you do or do not work for.

I'd prefer not to defend Exeltech's product

Then don't. Its as simple as that!

...and have tried to limit my comments to stating what I thought was reasonably common knowledge -- products are installed based on the manufacturer's instructions, not the musings of people on an Internet forum.

Well your thoughts, from my perspective alone, appear to be somewhat skewed. I do not care to know or debate the nature of such. I'll chalk it up to you being allowed your own opinion and leave it at that.

I was taught that if I had questions, I contacted the manufacturer for clarification, I didn't ask my buddies on an Internet forum for their opinion.

This leads me to believe you think the manufacturer always knows best, including matters of Code. This is analogous to an engineer is always correct... :lol:

And on that note, I'm done for the evening. I have to head to the house and deal with customers of my own and maybe watch some history documentaries on Netflix. And probably even have a beer.

Again, from my professional perspective I could care less... but on the personal side, I hope you enjoyed your evening.

 

[jaggedben]

However, "maximum current" is NOT always a number you can simply plug into an ampacity calculation.

690.8(A)(3) defines the number that is used for ampacity calculations for inverter output circuits.