Ampacity adjustment over 3 conductors

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Jpflex

Jpflex

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310.15C1 of NEC says that in a raceway with more than 3 current carrying conductors you are to reduce the current carrying conductors ampacity according to NEC table per number of conductors

I did not find a place under this section 310.15C1 that would point to this only applying to the number of conductors over 30. The code simply says over 3 conductors. So how would someone know there would be some random code scattered among 900 pages of NEC code to contradict this?

Apparently 376.22 A & B does this. All this time I thought conductors in a raceway such as EMT conduit would have to be de-rated in ampacity if over 3 current carrying conductors

This has brought more confusing and I’m not sure which way to go?
 
Jpflex said:
Apparently 376.22 A & B does this. All this time I thought conductors in a raceway such as EMT conduit would have to be de-rated in ampacity if over 3 current carrying conductors
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EMT is not a Metal Wireway subject to Article 376, so those sections don't apply EMT, and in EMT the limit is 3 CCCs. [Although for small conductors with 90C insulation, the practical limit is higher, as once you do the ampacity adjustment, the outcome is still higher than the 75C termination temperature limit.

Apparently Metal Wireways (and some sizes of MC cable?) are special in this regard. : - )

Cheers, Wayne
 
I don't know what Code cycle you are referencing but in the '17, 310.15(B)(3)(a) addresses the adjustment factor for more than 3 ccc in 310.15(B)(16) For 31-40 it's 40%
 
wwhitney said:
EMT is not a Metal Wireway subject to Article 376, so those sections don't apply EMT, and in EMT the limit is 3 CCCs. [Although for small conductors with 90C insulation, the practical limit is higher, as once you do the ampacity adjustment, the outcome is still higher than the 75C termination temperature limit.

Apparently Metal Wireways (and some sizes of MC cable?) are special in this regard. : - )

Cheers, Waynei
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I don’t recall seeing a NEC definition of metal wire way in article 90 but I’ll recheck. A “metal wire way” to me means a routing or way for wire
 
Checked article 100 under definitions not 90 and seen no such definition for wire way or metal wire way
 
Jpflex said:
Checked article 100 under definitions not 90 and seen no such definition for wire way or metal wire way
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Until you are under 2023 the scope of article 100 tells you to look at individual articles for more definitions.

Scope. This article contains only those definitions essential
to the proper application of this Code. It is not intended to
include commonly defined general terms or commonly defined
technical terms from related codes and standards. In
general, only those terms that are used in two or more
articles are defined in Article 100. Other definitions are
included in the article in which they are used but may be
referenced in Article 100.
Click to expand...
 
roger said:
Until you are under 2023 the scope of article 100 tells you to look at individual articles for more definitions.
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I plan on getting the 2023 NEC code book as my 2020 book is all ripped and pages dislocated. I take it along with every job and reference it
 
Obviously not 2023 code but good example of cross sectional area.
 

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Jpflex said:
I plan on getting the 2023 NEC code book as my 2020 book is all ripped and pages dislocated. I take it along with every job and reference it
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What code is enforced where you work though? Here we are still on 2017 and 2017 is what the inspectors will be enforcing until that changes.


As far as definitions go, I don't see "wireway" as a defined word either. There is "metal wireways" and "non metallic wireways" though.

NEC definitions are not necessarily for a single word term either.
 
roger said:
Until you are under 2023 the scope of article 100 tells you to look at individual articles for more definitions.
Click to expand...
Scope. This article contains only those definitions essential
to the proper application of this Code. It is not intended to
include commonly defined general terms or commonly defined
technical terms from related codes and standards. In
general, only those terms that are used in two or more
articles are defined in Article 100. Other definitions are
included in the article in which they are used but may be
referenced in Article 100.
Click to expand...

2017 Scope is word for word the same.
 
roger said:
That doesn't change what was said in post #8
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I first thought you were quoting what the scope says in 2023 and was wondering what was so different than before.
After looking at 2023 I see you were not quoting it.

Apparently they have moved all the definitions that were previously in other articles to art 100 even though those only applied to the section they used to be in.
 
kwired said:
What code is enforced where you work though? Here we are still on 2017 and 2017 is what the inspectors will be enforcing until that changes.


As far as definitions go, I don't see "wireway" as a defined word either. There is "metal wireways" and "non metallic wireways" though.

NEC definitions are not necessarily for a single word term either.
Click to expand...
NEC doesn’t have jurisdiction at the mine site I work at but that won’t keep me from trying to install safe according to NECs higher standards rather than MSHA.

Refereeing to NEC helps me engraving I’m memory these codes before journeyman license examination
 
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