# 366.22 and 366.56



## Sparkythao (Mar 26, 2013)

Also examples please, gutter im working with is 8"x8"x48". Thanks.


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## erics37 (May 7, 2009)

Sparkythao said:


> Also examples please, gutter im working with is 8"x8"x48". Thanks.


You take all the cross-sectional areas of the conductors installed in the gutter, measured in circular mils (or square inches or square centimeters or whatever) and you add them together.

You can find information on cross-sectional areas of various conductors & insulations types in the NEC Chapter 9, Table 5.

Personally I've found that conduit and gutter fill is kind of a self-enforcing code rule. You can try to stuff wires in there over capacity but good luck :laughing:


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## raider1 (Jan 22, 2007)

I agree with Eric.

Lets look at an example.

Your 8X8 wireway would have a cross sectional area of 64 square inches. Multiplying that by 20% you would be left with a cross sectional area you could fill of 12.8 square inches.

Now according to Table 5 Chapter 9 the area in square inches of #12 THHN/THWN-2 is 0.0133. So by dividing the 12.8 square inch cross sectional area of the 8X8 wireway by 0.0133 you could fill the 8X8 wireway with 962 #12 THHN/THWN conductors and fall within the 20% fill.

Now if we try it with say #6 THHN/THWN-2 we have an area of 0.0507 square inches according to Chapter 9 Table 5. So we could have 252 #6 THHN/THWN-2 conductors in the 8X8 wireway.

So you can see that the maximum conductor fill of 20% is really tough to accomplish.

The bigger factor with wireways is not the conductor fill but the ampacity adjustment factors that apply if you have more than 30 current carrying conductors at any cross sectional area of the wireway.

Chris


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## Pete m. (Nov 19, 2011)

I agree with Eric and Chris and will also point you at 366.23.

As shown you can get a boatload of conductors but derating will apply once you exceed 30 CCC's.

Pete


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## Semi-Ret Electrician (Nov 10, 2011)

Aux gutters are the best thing since sliced bread:laughing:


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