adjustment factors

[Geoffrey Lyons]

Am I getting this right... say I have 6, 8awg thhn ccc in 11/4 emt, table 310.16 in thhn column 8awg has ampacity 55 amps so I figure at table 310.15(B)(2)(a) 4-6 ccc , 80% the 8awg is now only good to 44 amps? What about 14 awg,12 awg,10 awg thhn per 240.4(D) do adjust from 15 a,20a,30a or use the ampacity values from 310.16 to make adjustment factors from above 3 ccc

 

[chris kennedy]

What about 14 awg,12 awg,10 awg thhn per 240.4(D) do adjust from 15 a,20a,30a or use the ampacity values from 310.16 to make adjustment factors from above 3 ccc

No sir. Start derating here.

110.14 Electrical Connections.
(C) Temperature Limitations. The temperature rating associated with the ampacity of a conductor shall be selected and coordinated so as not to exceed the lowest temperature rating of any connected termination, conductor, or device. Conductors with temperature ratings higher than specified for terminations shall be permitted to be used for ampacity adjustment, correction, or both.

Use the 90C column.

 

[infinity]

What Chris is saying is that your conductors are rated for 90 degrees C so you may use the 90 degree column in 310.16 to begin your derating calculation.

 

[Geoffrey Lyons]

thanx

thanx

I will have to read 110.14 . Just having hard time putting things in perspective with the temp ratings vs amperage ...like a 20 amp recept or 20 amp spst switch... but You certainly have my attention...will be in the book every break tommorrow trying to work it out,and of course a few more questions