Trough Fill

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sparky220volt

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Pensacola, FL, USA
I have a 10 foot long by 10 in by 10 in trough. It has 4 parallel 500 copper from the transformer totaling 16 500 coppers. There are three main lug panels on top of the trough with main breakers feeding there respective panels. There spliced in the trough from the transformer to all three panels. What I'm trying to figure out is, is the trough to small cause We've tried to fit it all in and it doesn't seem possible. I get 12,000 cubic inches for the trough. I looked up the circular mill area for all my wired then I found out the ground only counts once. But after I get my cma all multiplied and added up it doesn't come any where close to 12,000. I also saw something about only being able to fill gutters at 20%. To me this is a hard question. Just hopping someone can simplify it for me. I'm running this job and My PM is coming tomorrow and we're gonna try to figure out a way to get this done. Any input would be appreciated.
 
sparky220volt said:
I have a 10 foot long by 10 in by 10 in trough. It has 4 parallel 500 copper from the transformer totaling 16 500 coppers. There are three main lug panels on top of the trough with main breakers feeding there respective panels. There spliced in the trough from the transformer to all three panels. What I'm trying to figure out is, is the trough to small cause We've tried to fit it all in and it doesn't seem possible. I get 12,000 cubic inches for the trough. I looked up the circular mill area for all my wired then I found out the ground only counts once. But after I get my cma all multiplied and added up it doesn't come any where close to 12,000. I also saw something about only being able to fill gutters at 20%. To me this is a hard question. Just hopping someone can simplify it for me. I'm running this job and My PM is coming tomorrow and we're gonna try to figure out a way to get this done. Any input would be appreciated.
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The circular mil area is the area of the copper inside the conductor. When you add insulation and the wasted space between the round cables you are taking up a lot more space in the trough than that. And on top of that there definitely are fill requirements as well as derating requirements. Somebody goofed in the design.
 
The 20% fill is for a cross section, meaning that you have a cross section of 100 cubic inches (10"*10"). Take the area of the 16-500's and it cannot exceed 20% of the 100 cubic inches. Derating begins when you exceed 30 CCC's at any cross section.
 
infinity said:
The 20% fill is for a cross section, meaning that you have a cross section of 100 cubic inches (10"*10"). Take the area of the 16-500's and it cannot exceed 20% of the 100 cubic inches. Derating begins when you exceed 30 CCC's at any cross section.
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I agree with your computation, but it sounds like the OP may have splices involved in this wireway as well which they may not have accounted for.
 
Unless I made a mathematical mistake. based on the area of a 500 kcmil THHN (0.7073), you don't have a fill problem with a 10 x 10 wireway.
Finding a splicing means that allows you to connect your 4 parrall runs plus your taps and fit in the 10x10 may be challenging.

I do have an associated question: What tap rule are you using to feed MLO panels and how many breakers do you have in those panels. ?
 
sparky220volt said:
I have a 10 foot long by 10 in by 10 in trough. It has 4 parallel 500 copper from the transformer totaling 16 500 coppers. There are three main lug panels on top of the trough with main breakers feeding there respective panels. There spliced in the trough from the transformer to all three panels. What I'm trying to figure out is, is the trough to small cause We've tried to fit it all in and it doesn't seem possible. I get 12,000 cubic inches for the trough. I looked up the circular mill area for all my wired then I found out the ground only counts once. But after I get my cma all multiplied and added up it doesn't come any where close to 12,000. I also saw something about only being able to fill gutters at 20%. To me this is a hard question. Just hopping someone can simplify it for me. I'm running this job and My PM is coming tomorrow and we're gonna try to figure out a way to get this done. Any input would be appreciated.
Click to expand...
It seems that you are using Art. 314 rules as if this is a juction box. You ned to be using the Art. for wireways as infinity pointed out. This is a vastly different calculation. In addition you need to pay close attention the the requirements for splices in the wireway. Didn't run the calcs for your situation, so you will have to do some calculating. Art 312 rules will also come into play here.
 
augie47 said:
Unless I made a mathematical mistake. based on the area of a 500 kcmil THHN (0.7073), you don't have a fill problem with a 10 x 10 wireway.
Finding a splicing means that allows you to connect your 4 parrall runs plus your taps and fit in the 10x10 may be challenging.

I do have an associated question: What tap rule are you using to feed MLO panels and how many breakers do you have in those panels. ?
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LOL I was thinking the same thing in regards to the main lug panels, but he stated with main breakers

Great minds......:)
 
Joe Villani said:
LOL I was thinking the same thing in regards to the main lug panels, but he stated with main breakers

Great minds......:)
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I was unsure... it seemed like he was stating that he is feeding MLO panels which then had "Main" (Branch) breakers feeding sub-panels.
 
Splices are allowed to increase the fill to 75%. IMO it's impossible to actually make the splice and exceed 75%.
 
infinity said:
Splices are allowed to increase the fill to 75%. IMO it's impossible to actually make the splice and exceed 75%.
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Well, I don't know as I did not due any calcs, but it would seem that the OP has splices in the wireway with 4, 500's in and 3, 3/0's out times 4-don't know if that is compliant with out checking.
 
Also. This was the way the electrical riser was laid out. It's 4 parallels of 500 from the transformer taping to the feed for the 3 above panels. The 3 above panels then load back into the trough feeding straight through into the building where the sub panels are.
 
sparky220volt said:
Also. This was the way the electrical riser was laid out. It's 4 parallels of 500 from the transformer taping to the feed for the 3 above panels. The 3 above panels then load back into the trough feeding straight through into the building where the sub panels are.
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Sounds like you are now sharing a lot of previously unknown critical details that change everything. Details, details....:)
 
infinity said:
The 20% fill is for a cross section, meaning that you have a cross section of 100 cubic inches (10"*10"). Take the area of the 16-500's and it cannot exceed 20% of the 100 cubic inches. Derating begins when you exceed 30 CCC's at any cross section.
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You have confused the OP, because he now thinks that the volume of the trough is important.
What counts for fill is the cross section, as you said, and it is just 100 square inches.

"Details, details...." :thumbsup:
 
GoldDigger said:
You have confused the OP, because he now thinks that the volume of the trough is important.
What counts for fill is the cross section, as you said, and it is just 100 square inches.

"Details, details...." :thumbsup:
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Well, since I'm the one that said details, details, I have to confess that I did not notice that infinity said cubic inches. But I feel certain that he meant square inches. But, yes, it may have confused the OP. But I think we were trying to nudge him that this is a wireway application and cubic inches are not the criteria as in a junction box with conductors sized less than #4.
 
sparky220volt said:
I have a 10 foot long by 10 in by 10 in trough. It has 4 parallel 500 copper from the transformer totaling 16 500 coppers. There are three main lug panels on top of the trough with main breakers feeding there respective panels. There spliced in the trough from the transformer to all three panels. What I'm trying to figure out is, is the trough to small cause We've tried to fit it all in and it doesn't seem possible. I get 12,000 cubic inches for the trough. I looked up the circular mill area for all my wired then I found out the ground only counts once. But after I get my cma all multiplied and added up it doesn't come any where close to 12,000. I also saw something about only being able to fill gutters at 20%. To me this is a hard question. Just hopping someone can simplify it for me. I'm running this job and My PM is coming tomorrow and we're gonna try to figure out a way to get this done. Any input would be appreciated.
Click to expand...
0. The fill rules are based on the cross sectional area of the trough. Your number of 12,000 in3 is of no importance.
1. Maybe the ground only counts once for counting CCCs. But it will still occupy space. No rule can change that.
2. Are all four parallel 500s for each phase spliced and brought up to each of the main lug panels? That will take a lot more space. That means that below each panel there will be 32 500s in the trough, not 16. Even though 16 of them are running vertically.
3. Then you add in the size and number of the feeder conductors leaving the 3 panels, some of which would have to run parallel to the 500s.
 
texie said:
Well, since I'm the one that said details, details, I have to confess that I did not notice that infinity said cubic inches. But I feel certain that he meant square inches. But, yes, it may have confused the OP. But I think we were trying to nudge him that this is a wireway application and cubic inches are not the criteria as in a junction box with conductors sized less than #4.
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Yes, and yet the OP is looking at the area of his wires. Any trough longer than 1" will have a volume number that is greater than the area number. :slaphead:
 
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