wireway in wireway

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benaround

Senior Member
Location
Arizona
I'm trying to come up with a fix to this problem, more than 30 CCC in a 10x10 wireway.

One idea would be to install a 6x6 wireway inside the 10x10, this would reduce the CCC to

less than 30. I don't think that all the details are needed to ask if this basic principal would

violate the NEC ?
 
mcclary's electrical

mcclary's electrical

Senior Member
Location
VA
It's just a guess,,,IMO they are TECHNIALLY still in the same raceway.If you slid a 1/2" pvc into a 2" piece of pvc would that be two raceways? i know that sounds weird but that's how I look at it
 
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dbuckley

Senior Member
Location
Canterbury, New Zealand
I think this is a first principles failure.

The reason for derating cables in close proximity is because of the effects of excessive heat buildup, and you have to think that the NEC has a judgement based on a number of cables that can safely be grouped without excessive heat buildup

What you appear to be trying to do is undermine that engineering provision with a regulatory ruse that enables more current carrying, heat producting conductors to be installed in the same space.

I think that is wrong.

However, there is wiggle room if you can arrange your circuits so that the neutrals are not counted as CCCs.
 
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K2500

Senior Member
Location
Texas
I dont recall a requirment for air space between stacked wireways, and this would be similar to that. the only difference being one peice of sheet metal :EDIT: (and maybe heat disipating surface area). While i agree with it being more of a regulatory ruse,and would probably find an alternative method, I also think it would be legal as long as the resulting wireway(s) has ample crosssectional area for the conductors. I say that because you only mentioned number of conductors, and not size of conductors.

OTOH, if your conductors do not excede 10% of their rated ampacity, they need not be considered CCC. Is that correct?(Code Book not handy)
 
Pierre C Belarge

Pierre C Belarge

Senior Member
Location
Westchester County, New York
If it is possible, installing a barrier in the wireway will help you to conform to the number of conductors.
I see no issue with this type of workaround, as a matter of fact, code compliant creativity is part of the foundation of our industry.
 
tkb

tkb

Senior Member
Location
MA
dbuckley said:
I think this is a first principles failure.

The reason for derating cables in close proximity is because of the effects of excessive heat buildup, and you have to think that the NEC has a judgement based on a number of cables that can safely be grouped without excessive heat buildup

What you appear to be trying to do is undermine that engineering provision with a regulatory ruse that enables more current carrying, heat producting conductors to be installed in the same space.

I think that is wrong.

However, there is wiggle room if you can arrange your circuits so that the neutrals are not counted as CCCs.
Click to expand...

What's the difference between a wireway in a wireway, a wireway with a divider or two wireways next to each other.

I would call all of them separate raceways.
 
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nakulak

Senior Member
if there was any science involved in calculating wire fill for conduits, tubing, etc., how can installing filled wireways inside of other wireways have been accounted for in calculating heat dissipation in those wireways ? side by side (barrier) I can see, but wireway in another wireway ? I don't get it. Maybe someone can show me the science and convince me ?
 
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benaround

Senior Member
Location
Arizona
nakulak said:
if there was any science involved in calculating wire fill for conduits, tubing, etc., how can installing filled wireways inside of other wireways have been accounted for in calculating heat dissipation in those wireways ? side by side (barrier) I can see, but wireway in another wireway ? I don't get it. Maybe someone can show me the science and convince me ?
Click to expand...

nak,

You can put 30 #12's in a 4x4 wireway or 6x6 or 8x8 or 10x10, as soon as you get 31 CCC

in a cross sectional view you need to derate to 40% ampacity, it doesn't matter how many

cubic inches of "cooling" that have been allowed for.

I don't think there is any science to it, 30 CCC no derating, 31 CCC derate to 40%, do you

think that one extra CCC has enough science in it to cause such an effect?

Anyway, It was just an idea, We did not install it that way, had the guys rip it out and

repipe about 30 homeruns 1" AND 1.25".
 
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