Can a wireway be classified as a "Free Air" environment if there is 125 scfm of airflow through it?
Can free air be classified as "a wireway" if there is no air movement whatsoever?
I have myself battled the free air issue. My opinion is there are very few times this is useable. If you are using wireway I believe the section 376 could help there are very liberal conductor fill and derating rules but I think no to free air.
In an old production facility like mine there are 3 phase wires ran as single conductors in a triangle shape space a few inches apart ran over head like the power company I believe that qualifies.
i have seen motor starter manufactures prewire there enclosures similar to this based on ventilation and size of enclosure. But we do Temperature studies and many times I have seen hot spots develop. Keep in mind there is very little equipment made to run at the 90c rating of the 3 conductors in conduit rating. The 90c wire is mainly for other derating factors.
i had a class once for Nec and the instructor said just put a giant X on that table lol.
Retrieving data ...