Is Article 310 used for #14 EMT conduit fill caluclations?

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nanckekr

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I find the NEC a little complicated when trying to figure out how many #14 THNN 90 degree MYW wires are allowed in a 1/2" EMT conduit on a 15 amp general purpose circuit for lighting.

I read the 358.22, and based on Chapter 9 table 5, I found the #14 THHN has .0097in2 and with the ?? EMT conduit having a .304in2 total area, the 40% fill rule would allow me .304*.4/.0097 = 12 wires. So far so good...

For a 15A light breaker circuit, would I need to concern myself with chapter 310, in particular 310.15 ampacity calculations? The posts I found so far looked like only 358.22 were used?
 
hmmm....I am not sure I follow you...

If all the conductors are the same size...why not just use Table C.1 in the Annex C for the number of conductors in the conduit?
 
You are working too hard. Just go directly to Table C.a in Annex C, and look up a 1/2 inch conduit with #14 THHN, and it will tell you that you can fit 12 of them.

The question of how many wires you can put into a conduit is not related in any way to the question of how many amps you can put through any of the wires. The ampacity derating factors of Table 310.15(B)(2)(a) will apply.
 
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