Barrier in wireways and derating.

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Tainted

Tainted

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Suppose I have an 8x8 wireway, if you put more than 30 current carrying conductors in this wireway then you would need to derate the wires. I want to avoid the derating.

If I specify some kind of barrier separation in the middle of the wireway, does this will make two 4x8 wireways?

If yes, does this mean I can put 30 current carrying in each of the two 4x8 wireways for a total of 60 current carrying conductors or is it still considered an 8x8 wireway?
 
Tainted said:
Suppose I have an 8x8 wireway, if you put more than 30 current carrying conductors in this wireway then you would need to derate the wires. I want to avoid the derating.

If I specify some kind of barrier separation in the middle of the wireway, does this will make two 4x8 wireways?

If yes, does this mean I can put 30 current carrying in each of the two 4x8 wireways for a total of 60 current carrying conductors or is it still considered an 8x8 wireway?
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I would imagine since both sections share a common cover it would still count as 1 as it would still dissipate the heat the same? Or would a barrier change that?

Good question.
 
Dsg319 said:
I would imagine since both sections share a common cover it would still count as 1 as it would still dissipate the heat the same? Or would a barrier change that?

Good question.
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I think you are right. Technically I think the barrier will absorb the heat and then transfer the heat into the other section, vice versa. The barrier it comes with is not insulated.
 
You do understand that the "30 conductors" refers to 30 conductors in any one cross section and not in the overall wireway.
If you were to slice the wireway as you would a loaf of bread does the sliced piece exceed 30 conductors ?
 
Tainted said:
If I specify some kind of barrier separation in the middle of the wireway, does this will make two 4x8 wireways?
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It would seem that logically you could do that but I know of no code section that says installing a barrier in a wireway would make it the same as two wireways. For boxes a permanent barrier when installed makes a single box into two boxes, that is explicitly spelled out in Article 314, no such wording exists for wireways.
 
What's the difference between a wireway with a barrier and two wireways bolted side by each?

I think the barrier would serve to keep the wires in separate, smaller bundles and away from each other. It's the heat transfer between wires that drives the bundle-derating rules.
 
JoeStillman said:
What's the difference between a wireway with a barrier and two wireways bolted side by each?

I think the barrier would serve to keep the wires in separate, smaller bundles and away from each other. It's the heat transfer between wires that drives the bundle-derating rules.
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Good point.
 
JoeStillman said:
What's the difference between a wireway with a barrier and two wireways bolted side by each?

I think the barrier would serve to keep the wires in separate, smaller bundles and away from each other. It's the heat transfer between wires that drives the bundle-derating rules.
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There really is no difference except that the NEC has no wording that would allow a barrier to make a single wireway into two wireways.
 
Strathead said:
Just install 2 4x4 wireways butted against each other.
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Yea but a 4x8 wireway would let me put more wires in it but seems like we can unanimously agree that you cannot convert a 8x8 wireway into two 4x8 wireways so that each section can have 30 CCC lol.
 
Tainted said:
Yea but a 4x8 wireway would let me put more wires in it but seems like we can unanimously agree that you cannot convert a 8x8 wireway into two 4x8 wireways so that each section can have 30 CCC lol.
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I would say that if you put in a a barrier that is twice the thickness of the 8x8 wireway wall, and you are able to split the cover into two independently removeable covers, then you've successfully covered the 8x8 wireway into two 4x8 wireways. The independently removeable covers criterion does seem unnecessary.

How about installing a 4x wireway inside the 8x8 wireway to divide it into two compartments? : - )

Cheers, Wayne
 
wwhitney said:
I would say that if you put in a a barrier that is twice the thickness of the 8x8 wireway wall, and you are able to split the cover into two independently removeable covers, then you've successfully covered the 8x8 wireway into two 4x8 wireways. The independently removeable covers criterion does seem unnecessary.

How about installing a 4x wireway inside the 8x8 wireway to divide it into two compartments? : - )

Cheers, Wayne
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Would that make any real difference in the heat transferred to the other section? I can see it changing the speed of transfer as it will take a bit more time to get the double thickness up to the maximum temperature it will achieve, but after that, I see the same amount of heat transfer between the sections.
 
wwhitney said:
I would say that if you put in a a barrier that is twice the thickness of the 8x8 wireway wall, and you are able to split the cover into two independently removeable covers, then you've successfully covered the 8x8 wireway into two 4x8 wireways. The independently removeable covers criterion does seem unnecessary.

How about installing a 4x wireway inside the 8x8 wireway to divide it into two compartments? : - )

Cheers, Wayne
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Not sure if that would be feasible. For context, I am looking into using these wireways:

https://www.eaton.com/content/dam/e.../wireway-section-of-the-enclosure-catalog.pdf
 
Tainted said:
Haven't gone far through the design yet, each 8x8 wireway will have 10 apartments. That's 30 CCC right there.
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Does the netural count as an ccc.
Are these stacked or bundled for more than 24".
Rough math on area is 8*8**.20
Around 12.8 you would need to subtract material thickness usually around .0625. That would give you 12.40. for total area allowed.
7.875*7.875= 12.403

You may only have 20 ccc if netural does not count.
If not stacked or bundled longer than 24" no derate.

Edit, you may be able to use the 10' 10% if bundled or stacked longer than 24"
 
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