PV Wire - 7 or 19 Stranded, Code or Manufacturer Requirements to observe?

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Anode

Member
Location
Washington, USA
Simply put as title states.

PV Wire - 7 or 19 Stranded, Code or Manufacturer Requirements to observe?

Apparently we are the only contractors using 19 stranded wire. I know initially there was some controversy from a well versed code guru electrician of ours on the requirement of a connector we use frequently, perhaps it was mc4, and it not being able to be used with 7 strand. Or perhaps it was something about the characteristics of the copper being 19 stranded, a more theoretical approach. I don't know, and don't remember.

Anyone care to shed some light on why or why not to use either 7 or 19 strand wire. We do use many different connectors as well, not just mc4.

Thanks in advance for weighing in.
 
Location
California
7 strand is a class B conductor and 19 strand is a class C conductor (at #10 AWG). Most terminations are made for both Class B and Class C conductors (with or without indicating as much).

The finer stranding is more flexible and I've seen it used for dual axis trackers. 7 strand seems sufficient for single axis trackers, in my experience.
 

Zee

Senior Member
Location
CA
See Chapter 9 Table 10 for NEC recognized stranding (i.e. per UL 486A-B Wire Connectors).

I have heard of termination issues for the finer stranded wires, not the 7 strand.
(namely fine-stranded 2/0 and 4/0 cables for battery based PV)
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
See Chapter 9 Table 10 for NEC recognized stranding (i.e. per UL 486A-B Wire Connectors).
There are additional wire strandings which are "recognized" by the NEC in that they are part of the UL standard for recognized wire types that are mentioned in the NEC. They just do not appear in the table AND they are not supported by standard crimp and screw connectors.

From a lug manufacturer's web site, just to give you and idea of some of the options:

Copper fine stranded class G, class H, (aka battery cables) class I / type DLO (aka Diesel Locomotive) / class 5 metric (mm2) (aka "f") and class K (aka "MTW" Machine Tool Wire, Welding Cable). Note that names like "battery cable", "welding cable", etc are not good indicators of the actual stranding class. It is necessary to know the actual stranding class before mounting any wire.

The actual stranding details can be found in the manufacturers' specs and in the UL standard for each recognized wire type.
 

Smart $

Esteemed Member
Location
Ohio
There are additional wire strandings which are "recognized" by the NEC in that they are part of the UL standard for recognized wire types that are mentioned in the NEC. They just do not appear in the table AND they are not supported by standard crimp and screw connectors.

From a lug manufacturer's web site, just to give you and idea of some of the options:



The actual stranding details can be found in the manufacturers' specs and in the UL standard for each recognized wire type.
I'm not seeing anything in your post that backs up what you are saying.... :huh:
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
I'm not seeing anything in your post that backs up what you are saying.... :huh:

Well, just for one example, Table 310.104(A) lists MTW, and 310.10(A), (B), and (C) allow the use of MTW for any of the general wiring methods covered in Chapter 3. (Subject to the dry/damp/wet environment that applies.)

Others such as DLO, if that is the only type listed, are indeed not recognized by the NEC for Chapter 3 wiring. Same for "welding cable" and "battery cable" in general AFAIK. The devil is in the details and in possible multiple listings for one wire.

Or are you doubting that MTW is fine strand?

I do admit that the Application Provisions in the table do appear to limit the use to "machine tool wiring". :)

Type SGT (a subset of Class G stranding) is among the listed wire types for Section 552 use in Park Trailers. Not Chapter 3, but certainly recognized by the NEC.
 
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Smart $

Esteemed Member
Location
Ohio
Well, just for one example, Table 310.104(A) lists MTW, and 310.10(A), (B), and (C) allow the use of MTW for any of the general wiring methods covered in Chapter 3. (Subject to the dry/damp/wet environment that applies.)

Others such as DLO, if that is the only type listed, are indeed not recognized by the NEC for Chapter 3 wiring. Same for "welding cable" and "battery cable" in general AFAIK. The devil is in the details and in possible multiple listings for one wire.

Or are you doubting that MTW is fine strand?

I do admit that the Application Provisions in the table do appear to limit the use to "machine tool wiring". :)

Type SGT (a subset of Class G stranding) is among the listed wire types for Section 552 use in Park Trailers. Not Chapter 3, but certainly recognized by the NEC.
Thank you for the elaboration... but (and you know there's a 'but' when I'm involved :D) just being a recognized wire type does not mean you can use finer than Class C stranded. MTW is a good example. It comes down to 110.14, paragraph 2, even for recognized wire types...
Connectors and terminals for conductors more finely
stranded than Class B and Class C stranding as shown in
Chapter 9, Table 10, shall be identified for the specific
conductor class or classes.
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
Thank you for the elaboration... but (and you know there's a 'but' when I'm involved :D) just being a recognized wire type does not mean you can use finer than Class C stranded. MTW is a good example. It comes down to 110.14, paragraph 2, even for recognized wire types...
"But...."
What I took issue with was the implication of the literal wording of your statement that the NEC does not recognize or allow the use of finer stranded wire.
All that 110.14 tells us that is that standard terminals and connectors, not specifically identified for fine stranding, cannot be used with other than B or C stranding. To allow use of fine stranding with "ordinary" equipment there are a wide range of pin adapters, splices, and lugs which are UL listed for fine stranding and are properly marked for that purpose.
You just cannot blindly substitute fine stranded wire where you think added flexibility would be useful.
 
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Smart $

Esteemed Member
Location
Ohio
"But...."
What I took issue with was the implication of the literal wording of your statement that the NEC does not recognize or allow the use of finer stranded wire.
All that 110.14 tells us that is that standard terminals and connectors, not specifically identified for fine stranding, cannot be used with other than B or C stranding. To allow use of fine stranding with "ordinary" equipment there are a wide range of pin adapters, splices, and lugs which are UL listed for fine stranding and are properly marked for that purpose.
You just cannot blindly substitute fine stranded wire where you think added flexibility would be useful.
I concede to your amended version... ;)

...and MTW is made in several Classes of stranding, not all of which are consider fine stranded.
 
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Anode

Member
Location
Washington, USA
Requesting further clarification

Requesting further clarification

Thanks for the responses thus far.

I am requesting some further clarification with these two documents for the connector in question, and hopefully can mark the question as solved in my head thereafter.

MC4 connectors we use:

Data Sheet: https://www.platt.com/CutSheets/Multi-Contact/Pages 14-15 from Solarline.pdf
Assembly Guide: http://www.multi-contact.com/AcroFiles/MA/PV_MA231_(de-en).pdf

PV Wire we use:

Data Sheet: https://www.platt.com/CutSheets/Multiple/PV wire 600V PV Solarlink.pdf
Data Sheet: http://www.servicewire.com/sharepoi...2-416A-A284-2BD857E04319&InternalVersion=2817



The assembly guide on page 4 says that, "only cables with strand construction of class 5 and 6 can be connected". Can someone provide any information on what class 5 and 6 strand construction is, preferably with a document?

There is also a table for the acceptable gauges of wire, then some corrosponding definitions of sub text to the right where it states in sub text 5, "UL certified for UL PV-wire without USE2 certification only for 7-78 strands and ?-range of 6,05-8,2 mm". Does that mean that 7 strand would be acceptable?

It is of no real importance, but the assembly guide shows a fine strand cable in the diagrams. That doesn't mean 7 strand is not acceptable.

Anyone care to offer their expertise on this?
 

MasterTheNEC

CEO and President of Electrical Code Academy, Inc.
Location
McKinney, Texas
Occupation
CEO
I concede to your amended version... ;)

...and MTW is made in several Classes of stranding, not all of which are consider fine stranded.
A quick view of UL 4703 would show all of the conductors for use in PV Systems under Item 6.

Yes, both 7 and 19 are used......and indeed MTW is available in more than just fine stranded.
 
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