conduit fill question


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Old 06-06-06, 10:28 AM
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conduit fill question

Hi All,

Question concerning conduit fill requirements. Iím looking in the NEC in Chapter 9, and I see that under the notes for Table 2 it states that the requirement are not meant for protection of conductors over short runs.

I need to do exactly this: from my subpanel I need to run conductors approximately 6 feet to j-boxes either on the studs or roof eaves. Not sure what table to follow here or what my max is for 12 or 14 awg conductors.

Thanks!
 
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Old 06-06-06, 03:33 PM
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Look at note 4. A nipple 24 inches or less is allowed to be filled to 60% and derating per 310.15(B)(2)(a) does not apply. You are well past the 2 foot rule.


For conduit fill go to Annex C.

Don't forget to derate per 310.15(B)(2)(a)

but if you are using mixed sizes, you get to figure it out manually using , I think , tables 4 and 5 and 5a of chap 9
 
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Old 06-06-06, 05:26 PM
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Originally Posted by nap
Look at note 4. A nipple 24 inches or less is allowed to be filled to 60% and derating per 310.15(B)(2)(a) does not apply. You are well past the 2 foot rule.


For conduit fill go to Annex C.

Don't forget to derate per 310.15(B)(2)(a)

but if you are using mixed sizes, you get to figure it out manually using , I think , tables 4 and 5 and 5a of chap 9
Just checked and I was wrong; I'm right at 24 inches. So according to table C.1, I can fit 61 - 12awg THHN conductors in a 1 1/2" EMT? Am I on the right track? Or because it's less than 24 inches, is there another calc?

Thanks.
 

Last edited by fuente; 06-06-06 at 05:44 PM.
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Old 06-06-06, 08:02 PM
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Actually that table is for 40% fill. the note I gave allows up to 60% fill so that should be 1 1/2 times as many or 90 #12 thhn. Actually if you calculate it out using tabes 4 and 5 of chap 9 it comes out to 100 wires. And you do not have to derate them.

Now if you have this inspected and you have a picky inspector, if the nipple is 24 1/2 inches, he can ding you on it.


Is that enough wires for you??
 
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Old 06-06-06, 08:57 PM
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Originally Posted by nap
Actually that table is for 40% fill. the note I gave allows up to 60% fill so that should be 1 1/2 times as many or 90 #12 thhn. Actually if you calculate it out using tabes 4 and 5 of chap 9 it comes out to 100 wires. And you do not have to derate them.

Now if you have this inspected and you have a picky inspector, if the nipple is 24 1/2 inches, he can ding you on it.


Is that enough wires for you??
wow that seems like a lot of conductors !! Sounds good, that's plenty for the number of circuits I'm running.

Thanks nap.
 
 

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