Wireways/Troughs

[eddie_kerri]

I am currently feeding a 1600 amp switchgear from a transformer that will require (5) sets of 600kcmil conductors. Due to spacing issues we have decided to utilize a wireway/trough in lieu of individual flex raceways. I have sized the wireway as a 10x10 but would like some feedback as to what sections of the code I need to review to ensure I have sized the wireway correctly given the (2) 600kcmil conductors that will pass through the wireway from the transformer to the switchgear. Any feed back would be appreciated. I only get one shot at getting this right! Thanks!

 

[augie47]

(In regard to your post referencing this "lost posting". New posts are held for review to reduce the change of spam, etc.)
Welcome to the Forum. No doubt your question will be addressed shortly.

 

[augie47]

Assuming a metal wireway, Art 376.22 addresses fill.
You mentioned (5) sets of 600 kcmil then later, (2) sets. Can you clarify what conductors will be in the wireway ?

 

[eddie_kerri]

My apologies. There are (5) sets of (4) 600kcmil conductors for a total of (20) conductors in the wireway.

 

[Dennis Alwon]

Are we talking a 10" x 10" I hope not, or 10'x10'. Is this truly a wireway or JB. How deep?

 

[petersonra]

My apologies. There are (5) sets of (4) 600kcmil conductors for a total of (20) conductors in the wireway.

how much derating does 20 CCC in a raceway get you?

 

[petersonra]

Are we talking a 10" x 10" I hope not, or 10'x10'. Is this truly a wireway or JB. How deep?

good question. how in the heck do you have enough bending space with a 10" raceway and 20 600MCM wires? you might get them all in the wireway if they all came in one end and went out the other and there was no entry through the sides.

 

[eddie_kerri]

The only derating that has to be factored (I think) is if you have more than (30) current carrying conductors in a wireway. Basically, I have to feed a piece of switchgear and it would be more effective to install a wireway between the transformer and the switchgear in lieu of (5) 4" flexible metal conduits. I am looking for the correct size wireway to install to make the installation code compliant.

 

[eddie_kerri]

The wireway would be installed between the transformer and the switchgear. There is only about 18" between the two. Rather than having (5) 4" flexes, I wanted to install a wireway as a means of feeding the switchgear. It is basically like a nipple, but I would be using a wireway instead of emt or grc. I cannot figure out how big the wireway would need to be to comply with the NEC.

 

[don_resqcapt19]

The code would permit 23, 600kcmil THWN conductors in a 10" x 10" wireway.

 

[Smart $]

The wireway would be installed between the transformer and the switchgear. There is only about 18" between the two. Rather than having (5) 4" flexes, I wanted to install a wireway as a means of feeding the switchgear. It is basically like a nipple, but I would be using a wireway instead of emt or grc. I cannot figure out how big the wireway would need to be to comply with the NEC.

Assuming 20 THHN (no reduced neutral?) ? 0.8676 in?/conductor = 17.352in?

Assuming a supply side bonding jumper, 5 ? 600kcmil ? 12.5% = 375kcmils, rounded up to 400kcmil = 0.416in?

17.352in? + 0.416in? = 17.768in?

17.768in? ? 20% maximum fill = 88.84in? minimum cross sectional area.

10"?10" wireway at 100in? is compliant.

 

[GoldDigger]

The code would permit 23, 600kcmil THWN conductors in a 10" x 10" wireway.

Would the "nipple rule" or equivalent allow this less-than-18" wireway to be used without requiring derating?

 

[Smart $]

Would the "nipple rule" or equivalent allow this less-than-18" wireway to be used without requiring derating?

No adjustment factors apply to 30 or less CCC's in wireway [376.22(B)]. Correction for ambient still applies.

 

[Dennis Alwon]

The code would permit 23, 600kcmil THWN conductors in a 10" x 10" wireway.

I didn't even try to calculate it as it seemed there was no way it would fit. I am surprised yet again.

 

[Dennis Alwon]

It is interesting to me that a jb would need to be much larger than a wireway. I wonder why. They are basically the same space wise.

 

[GoldDigger]

It is interesting to me that a jb would need to be much larger than a wireway. I wonder why. They are basically the same space wise.

Possibility:

The JB calculation assumes that the wires will be coming in through limited openings (i.e. knockouts, etc.) while the raceway calculation assumes that the wires will come in anywhere in the open end cross section. That means all of the square cross section space is available, not just a bunch of circular cross sections within the square, which can waste space. And there would be fewer problems making the bends, etc. to enter into and exit the wireway.
JMSWAG.

 

[Smart $]

Possibility:

The JB calculation assumes that the wires will be coming in through limited openings (i.e. knockouts, etc.) while the raceway calculation assumes that the wires will come in anywhere in the open end cross section. That means all of the square cross section space is available, not just a bunch of circular cross sections within the square, which can waste space. And there would be fewer problems making the bends, etc. to enter into and exit the wireway.
JMSWAG.

In short, the wireway is used strictly as a wireway and not as a pull/junction box.

 

[eddie_kerri]

Thanks so much for the feedback! I appreciate everybody's input.