Ampacity

[iwire]

For the sake of conversation though....based on the Southwire info what do you think the ampacity is for 12/2 NM-B?:smile:

25 amps and if an inspector tried the 110.3(B) thing on me I would be contacting both southwire and UL about the misprint in that link.

This chart http://gencable.com/index.shtml?cables/dlo.htm for RHW says 12 AWG is rated for 40 amps, they show 400 amps for 4/0.

I will stick with the NEC ratings.

 

[480sparky]

25 amps and if an inspector tried the 110.3(B) thing on me I would be contacting both southwire and UL about the misprint in that link.

This chart http://gencable.com/index.shtml?cables/dlo.htm for RHW says 12 AWG is rated for 40 amps, they show 400 amps for 4/0.

I will stick with the NEC ratings.

Isn't that for Diesel Locomotive Cable 2000V?

 

[ibew441dc]

even though is says 20 amps, according to the nec that is incorrect as bob has pointed out.

110.3(b)......?????

 

[iwire]

Isn't that for Diesel Locomotive Cable 2000V?

It is dual rated for NEC applications.

Diesel Locomotive Cable 2000V ? UL ? RHH/RHW

600V ? CSA R90 ? CT Rated

 

[iwire]

110.3(b)......?????

Dude, it is obvious to me that is a mistake on southwires part.

 

[ibew441dc]

I'm with Bob on this one. Ampacity is based on 310.16, where it says it's 25. 240.4(D) is about overcurrent protection, not ampacity.

It's the same thing when it comes to the top speed of a car, as opposed to the speed limit.

I never mentioned anything about the OCPD or 240.2(D)....to be clear we are specifically addressing the ampacity of the 12/2 NM-B conductors.

 

[ibew441dc]

25 amps and if an inspector tried the 110.3(B) thing on me I would be contacting both southwire and UL about the misprint in that link.

This chart http://gencable.com/index.shtml?cables/dlo.htm for RHW says 12 AWG is rated for 40 amps, they show 400 amps for 4/0.

I will stick with the NEC ratings.

Why are you so sure its a misprint? If you called them and asked, and they told you it wasn't a misprint......Would you change your thoughts?

 

[ibew441dc]

Dude, it is obvious to me that is a mistake on southwires part.

Then what about these guys....it looks like they both messed up:roll:http://www.unitedcopper.com/specs/wire/NMB_sheet.pdf

 

[ibew441dc]

Then what about these guys....it looks like they both messed up:roll:http://www.unitedcopper.com/specs/wire/NMB_sheet.pdf

Shoot these guys must have screwed up too....http://www.cerrowire.com/default.aspx?id=27

 

[iwire]

Why are you so sure its a misprint? If you called them and asked, and they told you it wasn't a misprint......Would you change your thoughts?

I told you what I think, if you do not agree thats fine.

From your Cirro link

Type NM-B (Nonmetallic-sheathed Cable) may be used for both exposed and concealed work in normally dry locations at temperatures not to exceed 90?C (with ampacity limited to that for 60?C conductors) as specified in the National Electrical Code?.

From your Southwire link

APPLICATIONS
Southwire's Romex SIMpull ? Type NM-B (nonmetallic-sheathed cable) may be used for both exposed and concealed work in normally dry locations at temperatures not to exceed 90?C (with ampacity limited to that for 60?C conductors) as specified in the National Electrical Code

IMO both those links have mistakes in the charts.

 

[ibew441dc]

I told you what I think, if you do not agree thats fine.

IMO both those links have mistakes in the charts.

I'm not so much arguing that there is a possible and likely mistake:smile:......just cutting a clean conversation about code accountability, specifically 110.(3)(B)

I wonder if they did that for good reason...or just assumed no one would ever question it?

IMO the fact that the manufactures are limiting the 12awg conductors to 20amps tells me that only a 16amp continuous load is allowed.

If the conductors were good for 25amps a continuous load of 20 amps would be acceptable.

I'm starting to think that if their info is intended and accurate, it is addressing the possible breakdown of the outer jacket not so much the conductors???

 

[mivey]

IMO both those links have mistakes in the charts.

OK all you antiengineerites: obviously they are using 310.15(C) . Imagine the audacity of accusing the engineers of a mistake...I'm having a little trouble finding the table footnoted in this link or I could prove it to you:
http://www.unitedcopper.com/specs/wire/NMB_sheet.pdf

+ Not more than 3 conductors in cable per table 310-6, National Electrical Code.

 

[Pierre C Belarge]

Ampacity of 12/2 NM cable is determined as per 310.15, which leads us to Table 310.16. The 60C column limits NM cable to 25A, as per 334.80.

240.4(D) is the overcurrent protection of the conductor, not the ampacity rating of the conductor, as has already been discussed.


As for the charts of the two manufacturers, it is a shame, but they do have human beings working there, and it is another shame, but human beings make mistakes (except for the special "Mike Holt Breed"). :grin:


One of the reasons we can say that the ampacity value is 25As for NM-B cable is that 240.4(G) permits the ampacity to be up to 25 amps, not restricted as in 240.4(D).

 

[iwire]

I wonder if they did that for good reason...or just assumed no one would ever question it?

I think they made a mistake on the chart.

I think the words beside the chart tell us to follow the NEC.

I'm starting to think that if their info is intended and accurate, it is addressing the possible breakdown of the outer jacket not so much the conductors???

I disagree plain and simple.

Why is it that the outer jacket is going to break down only on 15, 20 and 30 amp circuits as the other ratings match the NEC?

 

[Pierre C Belarge]

Dan
the outer jacket is there to help provide some protection.
Your response shows you are using the gray matter a little and trying to reason...all good stuff.

Remember their engineers are sometimes just like us. Some are so used to the 20 Ampere requirement, that you tell them that under certain applications the ampacity can be higher they almost have a coronary. :grin:

 

[ibew441dc]

Fact- 1978 NEC T310-16, 60 degree C column said 12awg was good for 20amps
Fact- 1981 NEC T310-16, 60 degree C column said 12awg was good for 25amps

Assumption- Southwire, United, Cerro, ect. had there products listed a long time ago and forgot to update there info....????

 

[iwire]

Remember their engineers are sometimes just like us. Some are so used to the 20 Ampere requirement, that you tell them that under certain applications the ampacity can be higher they almost have a coronary. :grin:

I think it is as simple as that. :smile:

 

[480sparky]

Fact- 1978 NEC T310-16, 60 degree C column said 12awg was good for 20amps

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

Fact- 1981 NEC T310-16, 60 degree C column said 12awg was good for 25amps

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.

 

[ibew441dc]

I think they made a mistake on the chart.

I think the words beside the chart tell us to follow the NEC.




I disagree plain and simple.

Why is it that the outer jacket is going to break down only on 15, 20 and 30 amp circuits as the other ratings match the NEC?

The tables only differ for 14awg and 12awg, as to the exact reason, I don't know, and am merely open to conversation. I am not one who closes the door on something based upon opinion. Regardless of intent the manufactures for what ever reason state that there cables are only good for the limits listed. That being said mistake or no mistake 110.3(B) comes into play because that info is included in the product listing.

 

[Pierre C Belarge]

The tables only differ for 14awg and 12awg, as to the exact reason, I don't know, and am merely open to conversation. I am not one who closes the door on something based upon opinion. Regardless of intent the manufactures for what ever reason state that there cables are only good for the limits listed. That being said mistake or no mistake 110.3(B) comes into play because that info is included in the product listing.

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.