Changes to Table 310.(15)(16)

[inspector163]

I was looking through the 2011 Draft today, I noticed the values for copper 14 and 12 in the 60 degree column had been reduced to 15 and 20 respectively. Following the notes I tried to find a place in code that would allow the traditional values of 20 and 25 amps for uses such as derating, and use for 240(G) AC and motors etc. I have yet to find the language that allows the usual values of 20 and 25 amps for a starting point for these purposes. Both the table and 240.4 (D) mention 15 and 20A. Am I missing the values or is this gone?

 

[bphgravity]

They only changed Table 310.16 of the NEC to match the same table found in the CEC. The values used for the purposes of making adjustment or correction factors are based on the insulation type. If you are using 60 degree rated conductors, the value in the table is what you must use. If you are using 90 degree rated conductors, the higher rating is permitted to be used. There is no change to the code that allows small conductors to be loaded to the values in the tables for specific loads.

I think you are overthinking the change...

 

[don_resqcapt19]

If I am using a 60?C conductor for an air conditioning unit with a minimum circuit ampacity of 19 amps, under the 2008 code I could use a #14 and under the 2011 code I would have to use a #12.

 

[inspector163]

I hope I am over thinking the change. My concern is that where NM is used as feeder/branch circuit to AC or motor load with a min circuit ampacity of 18amp, the change would mean the min. wire size is now # 12. In NC it is viewed currently as #14. While I personally don't run it this way most do. I am a contractor, inspector and instructor.