NEC 2011 Annex I

[Nom Deplume]

In Annex I of the NEC, the tables have a column "A" and "B".

How do you use these tables?
What is the difference between the two columns? :?

 

[Dennis Alwon]

I found that Col. "A" is Lbs/ft while Col. "B" is N-M which I believe is a Newton Meter

 

[Dennis Alwon]

Okay-- Forget the last post.

Large Branch----Torque screw to applicable value shown in Column B
of the table for the conductor size installed.


Small Branch Torque screw to applicable value shown in Column A
of the table for the conductor size installed.

Each col. is lbs/ft or N-M in parenthesis - newton meter

That is from the white book. I still don't get it. Large branch-- what is that - large wires???

 

[mivey]

Column A is for current-cycling tests, column B is for other tests (heating, secureness pull-out, etc)

 

[mivey]

As for how to use: As far as I know, use column B.

The column A values are reduced values of column B for current carrying tests. It is interesting that the tables roughly have 75-80% of the B values but if there is a tightening torque specified with a connector, the UL 486 current-carrying test uses 90% of the specified tightening torque.

 

[Dennis Alwon]

Why isn't any of this described in the table?:?

 

[charlie b]

Each col. is lbs/ft or N-M in parenthesis - newton meter

This annex is in the 2011 version. The item in parenthesis is the English Engineering parameter (lbf-in), and the one without parenthesis is the metric parameter (N-m). You are correct in interpreting N-m as "Newton-meter." It refers to a force of one Newton acting at a distance of one meter from the axis of rotation of the torque wrench. The other one is not pounds per foot. It is "pounds of force acting at at distance of one inch from the axis of rotation."

 

[Dennis Alwon]

Thanks for the correction and I know it is in the 2011. It does not explain Col. A from B nor the lbf-in (N-M). I would think that that would be advisable otherwise the table is not much use to most.

 

[Gregg Harris]

Thanks for the correction and I know it is in the 2011. It does not explain Col. A from B nor the lbf-in (N-M). I would think that that would be advisable otherwise the table is not much use to most.

It appeares that it will change for the next cycle the description is in the ROP for the columns and A will be eliminated

 

[mivey]

Why isn't any of this described in the table?:?

Sloppiness I guess, or an assumption that everyone has access to everything and therefore we automatically know what they are talking about.

If you refer to the 2005 handbook you will see the desired values correspond to the B column. These values correlate to older versions of UL 486A before it became UL 486A-B.