Ampacity derating in Panduit wire duct
Ampacity derating in Panduit wire duct
(OP)
I am looking at chapter 12 in NFPA79 with regard to sizing conductors. I understand that Table 12.5.5(b) must be used to adjust ampacity when there are many conductors in a raceway or cable. My confusion is whether this also applies to conductors contained in slotted wiring duct. I was under the impression that since the slotted ducts allow airflow that they would not be considered a raceway.
However 12.5.5 says "Sizing of conductors within control enclosures in wiring harnesses or wiring channels shall be based on the ampacity in cable or raceway."
The verbiage is a little unclear to me. Am I supposed to treat conductors in a Panduit style wire duct like a raceway or cable?
Thanks in advance.
However 12.5.5 says "Sizing of conductors within control enclosures in wiring harnesses or wiring channels shall be based on the ampacity in cable or raceway."
The verbiage is a little unclear to me. Am I supposed to treat conductors in a Panduit style wire duct like a raceway or cable?
Thanks in advance.





RE: Ampacity derating in Panduit wire duct
I always treat them like in raceway -- the heating effect is not amplified so much by how the air circulates as it is by the heating effect of all the conductors' individual contributions when laid in a bundle. They're touching each other, and if there are enough in your wire duct, some will be completely surrounded by other current-carrying conductors.
My opinion anyway -- let's see who else pitches in.
Good on ya,
Goober Dave
RE: Ampacity derating in Panduit wire duct
RE: Ampacity derating in Panduit wire duct
However, if the conductors are loaded I would consider Panduit to be a raceway and derate accordingly.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Ampacity derating in Panduit wire duct
"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies
RE: Ampacity derating in Panduit wire duct
RE: Ampacity derating in Panduit wire duct
"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies