Derating for multiple wires in a conduit.

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xjfam

Member
Location
pennsylvania
I have a job where I am running 12-2 M/C to the panel. I would like to install a trough to run the M/C thru and down multiple conduits into the panel. This means I will have to run a bunch of 3/4 EMT with 3 current carrying conductors or up it to 1-1/2 and splice #10 in the trough to run more circuits. The other option is to just run all the M/C into the top of the panel. That just doesn't look as clean.
Anyone got any better ideas that I have missed? I just want it to look clean and it is on a tight budget.
Thanks,
 

raider1

Senior Member
Staff member
Location
Logan, Utah
If the nipples from the panel to the metal wireway are less than 2' you are not required to adjust the ampacity of the conductors in accordance with 310.15(B)(2)(a). Check out Exception #3 to 310.15(B)(2)(a).

Also if there are no more than 30 current carrying conductors installed at any cross section of the metal wireway you don't need to apply the adjustment factors of 310.15(B)(2)(a). Check out 376.22(B) (2008 NEC).

Chris
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
I'm sorry, I'm don't fully comprehend (nothing new), but if you have nipples between the panel and wireway and they are less than 24", you do not have to derate/ Once you exceed 30 current-carrying conductors in any cross sectional area of the wireway, derating will apply, but not until that number.

Does this help ?

(sorry Chris..typed slower)
 

raider1

Senior Member
Staff member
Location
Logan, Utah
I'm sorry, I'm don't fully comprehend (nothing new), but if you have nipples between the panel and wireway and they are less than 24", you do not have to derate/ Once you exceed 30 current-carrying conductors in any cross sectional area of the wireway, derating will apply, but not until that number.

Does this help ?

(sorry Chris..typed slower)

Not a problem Gus.:)

Chris
 
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