SE cable ampacity

[crtemp]

I'm a little confused on the amp rating of SE cable. I have been installing this for electric furnaces for as long as I can remember. I have been installing it under the 2008 NEC. When I look at
338.10 (b)(4)(a) for interior installations it says that I must comply with part II of article 334. In that part it says that it must use the 60 degree column for ampacity. If I look at that column it says it is only good for 55 amps, yet I have been using it for furnaces that draw 55-59 amps all the time and never get tagged for it. I always assumed it was good for 65 amps and I could use the 75 degree column. I thought it was weird that in 2011 a code change said that this wires ampacity now had to be determined by the 60 degree column. Wasn't it always in the 60 degree column if it has always had to comply with part II of article 334?

The wire I use is SE cable U type THHN

 

[infinity]

SE cable was for a long time used at its 75? C ampacity, then a few code cycles ago they changed to it be used, as you would NM cable, at 60? C ampacity. Then that was changed again {2011} to allow interior installations not embedded in insulation to be used at 75? C. Under the 2008 you're stuck with a maximum ampacity from the 60?C column of 310.16.

 

[Smart $]

E2+: As Rob said, and...

2008 says...

...comply with the installation requirements of Part II of Article 334.

2011/2014 changes it a bit and says...

...comply with the installation requirements of Part II of Article 334, excluding 334.80.

Where installed in thermal insulation, the ampacity shall be in accordance with the 60?C (140?F) conductor temperature rating. The maximum conductor temperature rating shall be permitted to be used for ampacity adjustment and correction purposes, if the final derated ampacity does not exceed that for a 60?C (140?F) rated conductor.

So it appears you may have been installing to Code after and before its time...