derating in emt

[davel]

what is the conduit fill in 3/4 emt. code book said 16- #12thhns, but with derating what would it be?

 

[bphgravity]

It would still be 16 conductors. Derating doesn't limit the number of conductors, it just limits the ampacity of those conductors.

 

[infinity]

Your question is actually asking about two different things. Maximum conduit fill and derating. 16-#12 conductors in a 3/4" could be anywhere between 12 and 16 CCC's. Are you really asking how many #12's can you install in a 3/4" EMT after derating and still maintain their normal (20 amp)ampacity?

 

[charlie b]

Are you really asking how many #12's can you install in a 3/4" EMT after derating and still maintain their normal (20 amp)ampacity?

If that is your question, the answer is 9. This presumes you are using a conductor rated for 90C, such as THHN.

 

[wireman71]

9 current carrying #12 THHN is the max number of current carrying conductors you can run in 3/4 EMT and use 20amp breakers.

310.15(b)(2)(a) 2008 NEC requires you to derate 70% for 7-9 current carrying conductors.

 

[480sparky]

Conduit fill is 16 conductors. (Table C.1)

Ampacity is 15 amps. (Value from T310,16 [30 amps] and multiply it by the figure given in T310.15(B)(2)(a) [50%]. 30 * 0.50 = 15amps.)


Oh, and welcome to the forum!