Conductors Overheat

[farmaped]

When laying or entering conductors in switchgear via wireways, gutters, "hi-hats" etc., is there a concern of phase placement to avoid the effects of overheating by induced fields?
Why I ask is, I am walking through a job to connect a 2MVA Transformer 480V secondary to a close coupled switchgear main. 6 paralled 750's. Pretty straitforward, about 6FT of cableout of the xfmr, through a custom built wireway, into the switchgear, and terminated.
The Foreman seems to remember a job landing 3kA 480V bus duct (via about 7FT of cables, through a hi-hat, into switchgear; and the cable orientation caused an overheating condition. He doesn't quite remember all the details, or how it was solved, but definately got me thinking.
Are there guidelines for this or a good reference?
Thanks

 

[peter]

You've got that right about inductive heating. You need all the phases and the neutral in each set to be in the same conduit, especially if in steel conduit.
There is a Code section about this and I'm sure one of the Code Mavens will soon chirp in with what it is.
~Peter

 

[bob]

Look at 300.20.A and B.

 

[brian john]

Whats a high hat besides a light fixtue?

 

[mistermudd]

Extra section added to the top of gear. Used when more space is needed to enter the gear with conduits and wire or cables. I kind of question the custom made part, usually needs to be listed with gear.

 

[brian john]

Header box, never heard it called a high hat

 

[supermanhicks]

So even though a header box a used the EC still must run the wire in conduit? The situation I am thinking of is 480v main gear outside of a building. Should the wire be in conduit in the header box?

 

[farmaped]

Thanks for the info.
All of the conductors will be grouped together, because they will be in the same enclosure. It can be thought of as Art. 366 Auxilliary Gutter or Art. 376 Metal Wireway, both of which have similiar fill and ampacity req'ts.
Basically, we need to get from the 2MVA transformer to the Switchgear, which is mounted directly beside the transformer. All indoors. The 3FT enclosure will be mounted on the switchgear/xfmr.
Thanks for Art. 320A Reference.
So, I'm wondering, is it best to lay the conductors in the Hi-Hat/Header Box/Aux. Gutter/Metal W-Way (give it a name) stacked (i.e. phase "A" layer, "B" layer, "C" layer) OR, stagger the layers, so that each "layer" has an "A", "B", and "C"?
I'm leaning toward staggering the phases in the layer. Perhaps I am thinking about this too much.

 

[don_resqcapt19]

If possible you need to install in groups of A,B,C,N. There are cases of cable burnup in tray where they were installed A,A,A,A-B,B,B,B-C,C,C,C-N,N,N,N.

 

[brian john]

So even though a header box a used the EC still must run the wire in conduit? The situation I am thinking of is 480v main gear outside of a building. Should the wire be in conduit in the header box?

No just take care in installing then in the header box..

Ski Utah (IN FEBUARY I WILL)

 

[supermanhicks]

If possible you need to install in groups of A,B,C,N. There are cases of cable burnup in tray where they were installed A,A,A,A-B,B,B,B-C,C,C,C-N,N,N,N.

Does anyone have any pictures of this actually happening?