Conductor Sizing and OCP for a AC Solar Panel

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Smart $

Esteemed Member
Location
Ohio
On the matter of the Type TC Home Run Cable, they may be able to get away with it under...

690.31 Methods Permitted.

(A) Wiring Systems. All raceway and cable wiring methods
included in this Code and other wiring systems and
fittings specifically intended and identified for use on photovoltaic
arrays
shall be permitted.
 

Smart $

Esteemed Member
Location
Ohio
Unless the manufacturer says so.
That is true for assemblies listed as a whole. I have seen no information to date that indicates such. Additionally, the installation manual states...

NOTE! For domestic US installations, all electrical work must be done in
compliance with local electrical codes and the NFPA 70 National Electrical
Code.
Maximum Continuous Output Current (AC) 1.8A
Compliant with the National Electric Code (NEC 1999-2008)
NOTE! The installer is solely responsible for:
1. Complying with all applicable local or national building codes, including any that may supersede this manual;
2. ...
Additional information required for installation may be found in the National Fire Protection Association Publication NFPA70, known as the National Electrical Code., any state building codes, and any applicable local codes.
NOTE! The combined output power of multiple inverters may not exceed the service rating of the circuits to which the inverters are connected. Consult ANSI/NFPA 70: The National Electrical Code for guidance.
WARNING! Obtain full inspection approval from your local electrical
inspector or other Authority Having Jurisdiction over electrical wiring inspections before activating the inverter.
 

tallgirl

Senior Member
Location
Great White North
Occupation
Controls Systems firmware engineer
Smart$ --

I'd have to go ask the regulatory dude about 20 feet from my current splot, but it is my understanding that if the manufacturer says "You can put ### on a 20A OCPD", you really can put ### of them on a 20A OCPD.
 
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Smart $

Esteemed Member
Location
Ohio
Smart$ --

I'd have to go ask the regulatory dude about 20 feet from my current splot, but it is my understanding that if the manufacturer says "You can put ### on a 20A OCPD", you really can put ### of them on a 20A OCPD.
Let us know what dude says... :D

In most cases I would agree with you. However, the White Paper mentioned clearly shows the determination of said number is not fully compliant with the NEC. To view White Paper, click http://www.exeltechsolar.com/products/ac-module/ and then "Home Run Cable White Paper" link in the Downloads section to the right side of the web page. It essentially says the ocpd is not subject to 690.8(B)(1).
 

tallgirl

Senior Member
Location
Great White North
Occupation
Controls Systems firmware engineer
Let us know what dude says... :D

In most cases I would agree with you. However, the White Paper mentioned clearly shows the determination of said number is not fully compliant with the NEC. To view White Paper, click http://www.exeltechsolar.com/products/ac-module/ and then "Home Run Cable White Paper" link in the Downloads section to the right side of the web page. It essentially says the ocpd is not subject to 690.8(B)(1).

I have read it and it explains their calculations. As I read the Code, the OCPD isn't subject to 690.8(B)(1), it's subject to 240.5(B)(2), as per 690.6(E).
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
I have read it and it explains their calculations. As I read the Code, the OCPD isn't subject to 690.8(B)(1), it's subject to 240.5(B)(2), as per 690.6(E).

240.5(B)(2) doesn't say anything about how to size an OCPD. I don't know how you can read that section to allow more than 16A of solar to be put on a 20A OCPD, regardless of the wire size used. That's especially true when you look at 690.6(C) which says "The output of the ac module shall be considered an inverter output circuit." That clearly implies the applicability of 690.8(A)(3), which in turn is referred to by 690.(B)(1)(a), which makes the whole thing pretty ironclad IMHO. There is nothing in 240.5(B)(2) that conflicts with or contradicts any of that (especially in the 2011 NEC).

I would love to save some circuits and subpanels here and there, but it just doesn't jive for Exeltech to play by different rules than everyone else plays by.
 

Smart $

Esteemed Member
Location
Ohio
I have read it and it explains their calculations. As I read the Code, the OCPD isn't subject to 690.8(B)(1), it's subject to 240.5(B)(2), as per 690.6(E).
And there is nothing wrong with that IF?and it's a big IF?that wiring is Fixture Wire [see 240.5(B)(2) and also Article 402]. There's an actual picture of the cable labeling in the instruction manual (link in Post #24), bottom picture on page 25. The resolution is a bit fuzzy, but I make it out to read: E171058-T (UL) TYPE TC 600V 90C WET 3C 12AWG XLPE SUN RES. This is not Fixture Wire.
 

tallgirl

Senior Member
Location
Great White North
Occupation
Controls Systems firmware engineer
240.5(B)(2) doesn't say anything about how to size an OCPD. I don't know how you can read that section to allow more than 16A of solar to be put on a 20A OCPD, regardless of the wire size used. That's especially true when you look at 690.6(C) which says "The output of the ac module shall be considered an inverter output circuit." That clearly implies the applicability of 690.8(A)(3), which in turn is referred to by 690.(B)(1)(a), which makes the whole thing pretty ironclad IMHO. There is nothing in 240.5(B)(2) that conflicts with or contradicts any of that (especially in the 2011 NEC).

I would love to save some circuits and subpanels here and there, but it just doesn't jive for Exeltech to play by different rules than everyone else plays by.

I'm not convinced they are.

Believe me -- I'm very competitive in the marketplace, but if the certification lab agreed with their 20A maximum OCPD specification for a 10 module string, that should be the answer.

Personally, I think it's a moot point because they are a 120VAC output solution, and I don't =personally= think 120 volt microinverters or ACPV modules are competitive in the market place, but I'm very uncomfortable with electricians arguing with manufacturer installation instructions for a product that's been through a test lab.
 

Smart $

Esteemed Member
Location
Ohio
I'm not convinced they are.

Believe me -- I'm very competitive in the marketplace, but if the certification lab agreed with their 20A maximum OCPD specification for a 10 module string, that should be the answer.

Personally, I think it's a moot point because they are a 120VAC output solution, and I don't =personally= think 120 volt microinverters or ACPV modules are competitive in the market place, but I'm very uncomfortable with electricians arguing with manufacturer installation instructions for a product that's been through a test lab.
That's another issue...

The way the documentation is presented makes many believe (apparently includes you) the product "stringing" is certified. If you go by UL certification, you'd be wrong. UL doesn't certify anything on the load side of an inverter's connections.

http://www.ul.com/global/eng/pages/offerings/industries/energy/renewable/photovoltaics/balance/

In the case of AC Modules (QHYZ), "AC modules are marked with the maximum size of dedicated branch circuit on which they may be installed and the maximum number of modules which may be connected in parallel."

Go to UL.com certifications directory search page...

http://database.ul.com/cgi-bin/XYV/template/LISEXT/1FRAME/index.html

...and search Helios or Exeltech as the Company Name. You'll find that neither has any file in the QHYZ category.
 

tallgirl

Senior Member
Location
Great White North
Occupation
Controls Systems firmware engineer
That's another issue...

The way the documentation is presented makes many believe (apparently includes you) the product "stringing" is certified. If you go by UL certification, you'd be wrong. UL doesn't certify anything on the load side of an inverter's connections.

http://www.ul.com/global/eng/pages/offerings/industries/energy/renewable/photovoltaics/balance/

In the case of AC Modules (QHYZ), "AC modules are marked with the maximum size of dedicated branch circuit on which they may be installed and the maximum number of modules which may be connected in parallel."

Go to UL.com certifications directory search page...

http://database.ul.com/cgi-bin/XYV/template/LISEXT/1FRAME/index.html

...and search Helios or Exeltech as the Company Name. You'll find that neither has any file in the QHYZ category.

Two comments:

1). UL is one of many labs. They aren't the only lab.
2). I believe this covers what you're objecting to --

"AC modules are marked with the maximum size of dedicated branch circuit on which they may be installed and the maximum number of modules which may be connected in parallel."

Please, I'd love to stop defending a competitor, but I'm not convinced there's anything wrong with putting 10 of their modules on a 20 amp OCPD if they made it through whichever lab's test program they went through.
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
Two comments:

1). UL is one of many labs. They aren't the only lab.
2). I believe this covers what you're objecting to --

"AC modules are marked with the maximum size of dedicated branch circuit on which they may be installed and the maximum number of modules which may be connected in parallel."

Please, I'd love to stop defending a competitor, but I'm not convinced there's anything wrong with putting 10 of their modules on a 20 amp OCPD if they made it through whichever lab's test program they went through.
I wouldn't do it. When the NEC and manufacturer's instructions disagree, I'm going with the more conservative approach.
 

tallgirl

Senior Member
Location
Great White North
Occupation
Controls Systems firmware engineer
I wouldn't do it. When the NEC and manufacturer's instructions disagree, I'm going with the more conservative approach.

What bad thing do you envision happening if someone puts 10 of their microinverters on the line side of a 20A breaker?

Since the NEC explicitly recognizes lab ratings programs, why do you think this lab certified product, with its manufacturer-provided installation instructions, isn't compliant when a power cord that isn't a #12 can be plugged into a receptacle, connected to a 20A OCPD via #12 wiring? I'm trying to understand why you give one the nod and don't much care for the other.
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
What bad thing do you envision happening if someone puts 10 of their microinverters on the line side of a 20A breaker?

Since the NEC explicitly recognizes lab ratings programs, why do you think this lab certified product, with its manufacturer-provided installation instructions, isn't compliant when a power cord that isn't a #12 can be plugged into a receptacle, connected to a 20A OCPD via #12 wiring? I'm trying to understand why you give one the nod and don't much care for the other.
Perhaps it's just ignorance of the subtleties of the NEC on my part, but I prefer to err on the side of caution. I know that I can safely and compliantly put 16A of inverter power on a 20A breaker. For 18A, I know I can do it with a 25A breaker and appropriately sized conductors. Unless it's a hugely redundant system, the cost difference is negligible. The code is fairly straightforward: 1.25 X the total inverter rated current and go up to the next sized breaker. This may or may not be a legit exception, but the fact that an exception exists does not mean that you have to use it. IMO, this is more like an exam question than a real world decision.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
if the certification lab agreed with their 20A maximum OCPD specification for a 10 module string, that should be the answer.

I see no evidence that that is the case. Instead I see a white paper that conveniently ignores the code sections I mentioned. Also the exception to 690.(B)(1)(a) requires that such a product be listed as an assembly together with its overcurrent device. The Exeltech system does not include an OCPD.
 

Smart $

Esteemed Member
Location
Ohio
It appears the point is escaping you...

Two comments:

1). UL is one of many labs. They aren't the only lab.
True... but 10 of these AC Modules is not certified—by any of those labs—for connection to the Home Run Cable or a 20A breaker. That assessment is made entirely by the manufacturer.

2). I believe this covers what you're objecting to --

"AC modules are marked with the maximum size of dedicated branch circuit on which they may be installed and the maximum number of modules which may be connected in parallel."
Yes it covers what I'm objecting to... IF ...the product were certified in this category. It is not.

Please, I'd love to stop defending a competitor, but I'm not convinced there's anything wrong with putting 10 of their modules on a 20 amp OCPD if they made it through whichever lab's test program they went through.
Well we have given you plenty info' to stop defending a competitor. Continuing to do so just escalates our opinion that you support questionable business practice.
 
as a electrician

as a electrician

I will use what I think the code says whether AC or DC photovoltaic output is continuous for more than three hours so that tells me to use 125% of the output current to size OCPD
 

tallgirl

Senior Member
Location
Great White North
Occupation
Controls Systems firmware engineer
It appears the point is escaping you...


True... but 10 of these AC Modules is not certified?by any of those labs?for connection to the Home Run Cable or a 20A breaker. That assessment is made entirely by the manufacturer.


Yes it covers what I'm objecting to... IF ...the product were certified in this category. It is not.


Well we have given you plenty info' to stop defending a competitor. Continuing to do so just escalates our opinion that you support questionable business practice.

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

http://www.heliossolarworks.com/Portals/132436/Sales/6t ac.pdf

Personally, just for myself, I wouldn't purchase that product. I have plenty of professional reasons not to, and I'd be more than happy to share them outside of a public forum (over a beer without a tape recorder ...).

That said, if y'all have any questions about how they are representing their product, feel free to contact Intertek.
 
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