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#84860 - 05/13/03 12:22 PM Free Air
boxford Offline
Member

Registered: 03/10/03
Posts: 15
Loc: St. Paul, MN, USA
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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#84861 - 05/13/03 03:26 PM Re: Free Air
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6804
Loc: Brick, NJ USA
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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#84862 - 05/13/03 04:05 PM Re: Free Air
electric-ed Offline
Member

Registered: 07/08/02
Posts: 184
Loc: Canada
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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#84863 - 05/13/03 05:06 PM Re: Free Air
sparky Offline
Member

Registered: 10/18/00
Posts: 5545
and i thought i could fill my tires for free here, so much for livin' in the past eh?

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#84864 - 05/14/03 05:52 AM Re: Free Air
boxford Offline
Member

Registered: 03/10/03
Posts: 15
Loc: St. Paul, MN, USA
I really appreciate everyones help.

Brian

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