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Joined: Mar 2003
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Referencing Table 310.19 it states the following:
Table 310.19 Allowable Ampacities of Single-Insulated Conductors, Rated 0 Through 2000 Volts, 150 degrees Through 250 degrees (302 degrees F Through 482 degrees F), in Free Air, Based on Ambient Air Temperature of 40 degrees C (140 degrees F)
Does anyone know of a reference that specifically states the definition of "Free Air"?
I appreciate anyones help.
Brian
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Joined: Apr 2002
Posts: 7,413 Likes: 9
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Boxford:
I'll take a stab at "free air"...
The best street definition I can come up with is an installation as the utility companies use. Single conductors mounted on cross arms or similar approved methods on poles. I could take it a step further and mention the "older" rack service drops at some commercial buildings; a "rack" is mounted to the exterior wall, on which insulators are mounted, and individual conductors are mounted to the insulators. This is not a commonly used installation now.
Hope this helps
John
John
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Joined: Jul 2002
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Single conductors, spaced more than one diameter apart in a ventilated (ladder type) cable tray, are usually considered to be "free air".
Ed
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Joined: Oct 2000
Posts: 5,393
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and i thought i could fill my tires for free here, so much for livin' in the past eh? ![[Linked Image]](https://www.electrical-contractor.net/ubb/rolleyes.gif)
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Joined: Mar 2003
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I really appreciate everyones help.
Brian
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Posts: 2,236
Joined: November 2000
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