Derating Question....

[emahler]

we have a 400A 3PH 4W service entering a building...from the CT we are feeding (2) 200A MCB panels via a trough...

if we run a set of 3/0 from the CT to each panel (distance is about 6' to 1st panel, and 8' to 2nd) in the trough.....do we need to derate?

i haven't done any calculations, just thinking out loud...

edit to add: the trough is 8"x8"

 

[benaround]

emalher,

Well, you would have more than 3 CCC,s in a raceway, so I would say you have to derate.

O.k. 6 CCC's = 80% derating

3/0 cu. 90deg. = 225a

80% of 225 = 180a

If the calculated load is less than 180amps, imo, your set up is good.

 

[augie47]

My vote would be otherwise. In a wireway or auxiliary gutter,derating doesn't apply until you exceed 30 {376.22(b)}

 

[Pierre C Belarge]

My vote would be otherwise. In a wireway or auxiliary gutter,derating doesn't apply until you exceed 30 {376.22(b)}

Wireways are part of the definition of Raceway in Article 100. Yet, the Article that Augie posted does have specific requirements in regards to ampacity adjustment which would preclude the "more than 3 current carrying conductors". Ampacity adjustment in this case is not necessary.

 

[benaround]

You guys are right, I just saw that and was coming back here to correct what I said, but

I'm too late. I know better too, just took the wrong road this time!!!

 

[infinity]

I agree, for a wireway, unlike other raceways the magic number is 30.

 

[M. D.]

I agree, for a wire-way, unlike other raceways the magic number is 30.

as long as it is not a non metallic wire-way

 

[emahler]

as long as it is not a non metallic wire-way

why is that?....

in this case, it's a metal trough...