Ampacity

[ibew441dc]

Fact: There were no obelisks in the 60?C column of T310-16 in the 1978.



Fact: There ARE obelisks in the 60?C column of T310-16 in the 1981.

All they did is rewrite the same thing in a difference manner.

They changed the numbers from 20 in 1978 to 25 in 1981 for 12awg in the 60* column

 

[cpal]

to get a little off target
NM is a 60 degree insulation
NM A is 75degree, and
NM B is 90 degree,
its in the explanatory print of the 84 or 87 HB in old art 336.

 

[mivey]

I wonder if this same info is identified/labeled on the packaging?

Anybody have a package they can look at and see?


I have not done any side work lately, othewise I would.
Yes, the world is a safer place since I stopped.

It is not on the packaging.

 

[Pierre C Belarge]

Mivey
Thank you for looking.

 

[76nemo]

I thought there was a thread awhile back where Tom Baker found out NM was tested and rated at 30A's, but only allowed by NEC for 20 or 25 depending on the article????

 

[gndrod]

rating

rating

I'm catch'n what your throw'in as far as the directive stated in 334.80 but take a look at this http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheet6

although it may be unintended...it says 20 amps is the ampacity of 12/2.

Using the Southwire Brand Romex type NM-B, I think 110.3(B) comes into play.

Hi Daniel, Bob is correct and so are you. It just depends on whether the application is applicable to 310.15 for 20 and 310.16 for 25 ampacities. Check Southwires note below that states 310.15. rbj

 

[gndrod]

Test

Test

Question: What is the ampacity of a 12/2 NMB Cable?
How do you answer this when taking a Master Electrician's Exam?

Ampacity per Table application = 310.15....20, 310.16....25 (defaults to 240.4(D)]

 

[mivey]

Ampacity per Table application = 310.15....20, 310.16....25 (defaults to 240.4(D)]

"310.15....20"?? Don't see 20 amps until 240.4(D)(5). It is either a typo or outdated tables. I'm guessing outdated tables.

No need to guess. I've just sent an email to ask.

 

[iwire]

No need to guess. I've just sent an email to ask.

Don't start messing things up with facts.

 

[mivey]

"310.15....20"?? Don't see 20 amps until 240.4(D)(5). It is either a typo or outdated tables. I'm guessing outdated tables.

No need to guess. I've just sent an email to ask.

According to a conversation with Southwire, the 15 & 20 amp listing in the table is based on the footnote of Table 310.16 referring you to 240.4(D). They were limiting the ampacity to the overcurrent protection shown in 240.4(D)

They had not considered that "Unless specifically permitted in 240.4(E) or (G)" might allow for greater ampacity, and had never heard it come up (at least the guy I talked to). They are going to look into it and see if they might need to revise their table.

 

[ibew441dc]

Thanks Mivey

Thanks Mivey

According to a conversation with Southwire, the 15 & 20 amp listing in the table is based on the footnote of Table 310.16 referring you to 240.4(D). They were limiting the ampacity to the overcurrent protection shown in 240.4(D)

They had not considered that "Unless specifically permitted in 240.4(E) or (G)" might allow for greater ampacity, and had never heard it come up (at least the guy I talked to). They are going to look into it and see if they might need to revise their table.

Cool Thanks for the update!:smile: Prior to this thread being started I wouldn't even of questioned the directive in the NEC, I probably never would have looked at the ampacity table provided by Southwire....and I definitely would not have called Romex NM-B.....I always called it plain ole NM.
The gears are always forced to turn on this forum

 

[Pierre C Belarge]

According to a conversation with Southwire, the 15 & 20 amp listing in the table is based on the footnote of Table 310.16 referring you to 240.4(D). They were limiting the ampacity to the overcurrent protection shown in 240.4(D)

They had not considered that "Unless specifically permitted in 240.4(E) or (G)" might allow for greater ampacity, and had never heard it come up (at least the guy I talked to). They are going to look into it and see if they might need to revise their table.

I am willing to bet all of your money the table will be revised. Bet, bet...huh?

 

[Twoskinsoneman]

It's funny sometimes during a discussion ANY information provided by the manufacture is gossple, but when we don't like oh it must be a misprint.

My opinion is that 110.3(b) does not say you have to follow the tables in a a pdf about a product. It says listing and labeling. It says what it says.

So here is what the UL listing says.

NONMETALLIC-SHEATHED CABLE
(PWVX)​

USE​

This category covers Types NM-B and NMC-B nonmetallic-sheathed
cable, rated 600 V, intended for use in accordance with Article 334 of
ANSI/NFPA 70, ??National Electrical Code?? (NEC), and Listed in copper
sizes 14 to 2 AWG inclusive and aluminum or copper-clad aluminum​

sizes 12 to 2 AWG inclusive.

This cable contains conductors rated 90?C; however, the ampacities of the cable are those of 60?C conductors as specified in Article 334 and Table 310.16 of the NEC

25 amps it is.​

 

[Pierre C Belarge]

TWO=

I believe a manufacturer can be more strict than the standard when testing/labeling their product.
As long as they identify the product properly.

 

[480sparky]

TWO=

I believe a manufacturer can be more strict than the standard when testing/labeling their product.
As long as they identify the product properly.

I'm leaning more towards it wasn't an engineer or designer that came up with the numbers on their specs..... it's probably a lawyer.

Marketing: "We need a cut sheet for this wire. We need to specifiy it's current-carrying capability."
Engineering: "Well, the NEC says it's 25 amps."
Legal: "Guys, let's CYA. Put down 20 amps."
Management: "Sounds good. Make it so."

 

[Twoskinsoneman]

TWO=

I believe a manufacturer can be more strict than the standard when testing/labeling their product.
As long as they identify the product properly.

PIE=
I agree. As long as it's in the listing or labeling.

This is silly but I guess it comes down to definitions of instructions and labeling and listing.

The NEC says labeling is attached to the equipment. It doesn't mention anything about pdf found on it's website.

So IAW the NEC if it's not a label on the equipment or instructions in the listing than it isn't mandatory.

Funny how "Charlie's" rule gets tossed when it doesn't align with our opinions any more.

 

[iMuse97]

PIE=
I agree. As long as it's in the listing or labeling.

This is silly but I guess it comes down to definitions of instructions and labeling and listing.

The NEC says labeling is attached to the equipment. It doesn't mention anything about pdf found on it's website.

So IAW the NEC if it's not a label on the equipment or instructions in the listing than it isn't mandatory.

Funny how "Charlie's" rule gets tossed when it doesn't align with our opinions any more.

Yes, and thanks for a great thread. Y'all hashed this one out really well!

 

[iwire]

PIE=
I agree. As long as it's in the listing or labeling.

I agree, only the instructions found connected with the listing and labeling matter, not marketing documents.

 

[iwire]

TWO=

I believe a manufacturer can be more strict than the standard when testing/labeling their product.
As long as they identify the product properly.

We have talked about this before and I still do not agree.

In order to list a product to a particular standard there are obligations you must meet, you can't say I choose not to meet all these obligations but still desire the same listing as another manufacturer that meets all the obligations.

 

[Pierre C Belarge]

I remember speaking with John Canjemi of UL, and he has stated in the meetings that the manufacturer uses the standards as guidelines, but can write stricter labeling as long as it does not change the minimum of the Standard(s) they are required to adhere to.


Similar to the way there are so many different types of manufacturing processes for metal boxes.