Article 378.22 wireway fill limits

[rjc3po]

Hello,
I would like to better understand the fill requirements for non-metallic wireway (Panduit) according to NEC'08 section 378.22 one is required to calculate the maximum fill of Panduit to be 20%.

But, according to the NFPA 79 Electrical Standard for industrial Machinery 2007 Edition, it specifies:

13.5.2 Percentage fills of Raceways (Ducts)
"The combined cross-sectional area of all conductors and cables shall not exceed 50% of the interior cross-sectional area of the raceway (duct). The fill provisions shall be based on the actual dimensions of the conductors or cables used"


Also, according to definitions "wireways" and ?Conduits? are included under the term "raceways".

Which percent fill should I use?

Further, what does this mean for conduits on industrial machines? If I use NFPA 79, I can fill each conduit to 50% regardless of the number of CCC?s and NEC 08 chapter 9 table 1 does not apply.

 

[mcclary's electrical]

Fill pecentage is fill percentage, DERATING would STILL apply. Machinery Man. are not held limited by the NEC,,,,basically they do what they want and fit wires WHEREVER they can cram em, The NEC says the SMALLEST conductor you can parallel is 1/0. Yet I've worked on cranes that have very flexible cables going to 50 horsepower motors. These cables have fifty small stranded conductors in them and they put 12 conductors per phase feeding their motors because the cable has to be flexible, Are you gonna whip out the nec and tell them they can't do that? I don't think so.

 

[benaround]

rjc,

The cross sectional area can be filled to 20%, after 30 CCC you must derate. The 50%

fill is for when you are using the wireway for larger conductors ( such as taps, etc.) you

may have only 12 conductors in the wireway, so the NEC had to limit it somehow and 50%

fill is how. IMO.

 

[RUWired]

rjc,

The cross sectional area can be filled to 20%, after 30 CCC you must derate. .

The 30 ccc does not apply to nonmetallic wireways. The derating factors apply right off the getgo.

The derating factors specified in 310.15(B)(2)(a) shall be applicable to the current-carrying conductors up to and including the 20 percent fill specified above.

 

[benaround]

The 30 ccc does not apply to nonmetallic wireways. The derating factors apply right off the getgo.

The derating factors specified in 310.15(B)(2)(a) shall be applicable to the current-carrying conductors up to and including the 20 percent fill specified above.

I agree with you on this.

 

[Smart $]

Hello,
I would like to better understand the fill requirements for non-metallic wireway (Panduit) according to NEC'08 section 378.22 one is required to calculate the maximum fill of Panduit to be 20%.

But, according to the NFPA 79 Electrical Standard for industrial Machinery 2007 Edition, it specifies:

13.5.2 Percentage fills of Raceways (Ducts)
"The combined cross-sectional area of all conductors and cables shall not exceed 50% of the interior cross-sectional area of the raceway (duct). The fill provisions shall be based on the actual dimensions of the conductors or cables used"


Also, according to definitions "wireways" and ?Conduits? are included under the term "raceways".

Which percent fill should I use?

Further, what does this mean for conduits on industrial machines? If I use NFPA 79, I can fill each conduit to 50% regardless of the number of CCC?s and NEC 08 chapter 9 table 1 does not apply.

If you are talking about Panduit used as wiring "gutter" internal to control cabinets, you go by NFPA 79's requirements. NEC requirements are for wireways external to the cabinet.