Conduit Fill

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Alwayslearningelec

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NJ
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Estimator
Maximum number of #14 THHN in EMT @ 40% fill? Looking for NEC section, I can't locate. Weird I always have bookmarked.
 
don_resqcapt19

don_resqcapt19

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Illinois
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retired electrician
The actual rule is in Chapter 9, Table 1, and the numbers found in Annex C are calculations that have been done for you based on Chapter 9, Tables, 1, 4 & 5. The numbers in Annex C are all based on more than two conductors of the same size in a raceway. Where you have conductors of differing sizes, you have to do your own calculations based on Tables 1, 4 and 5.
 
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wwhitney

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Berkeley, CA
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Retired
don_resqcapt19 said:
The actual rule is in Chapter 9, Table 1, and the numbers found in Annex C are calculations that have been done for you based on Chapter 9, Tables, 1, 4 & 5. The numbers in Annex C are all based on more than two conductors of the same size in a raceway.
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Wait, really? Where the table says "2" that should mean that the fill is no more than 31% with 2 conductors. And where the table says "-" that should mean that one conductor is bigger than 53% of the cross sectional area. Did they really use 40% in all cases?

Cheers, Wayne

PS Seems like Table 1 needs a footnote for 3 or more conductors saying that any 2 of the conductors should not exceed 31% of the conduit area. At least, I'm not sure why the limit is 31% for 2 conductors, but I can't imagine a reason for which adding one or more smaller conductors would help.
 
Seven-Delta-FortyOne

Seven-Delta-FortyOne

Goin’ Down In Flames........
Location
Humboldt
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EC and GC
Not big on these things they call “apps” 😳 I just got a “smart phone” about a year ago, but…..


This is I think the only “app“ I have. It’s great for quick ampacity and conduit fill calculations.

637D6159-70EE-4E29-A7AA-C2C010882206.png
 
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