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#84860 - 05/13/03 03:22 PM Free Air  
boxford  Offline
Member
Joined: Mar 2003
Posts: 15
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 06:26 PM Re: Free Air  
HotLine1  Offline


Member
Joined: Apr 2002
Posts: 6,799
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

#84862 - 05/13/03 07:05 PM Re: Free Air  
electric-ed  Offline
Member
Joined: Jul 2002
Posts: 175
Canada
Single conductors, spaced more than one diameter apart in a ventilated (ladder type) cable tray, are usually considered to be "free air".

Ed


#84863 - 05/13/03 08:06 PM Re: Free Air  
sparky  Offline
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Joined: Oct 2000
Posts: 5,303
and i thought i could fill my tires for free here, so much for livin' in the past eh? [Linked Image]


#84864 - 05/14/03 08:52 AM Re: Free Air  
boxford  Offline
Member
Joined: Mar 2003
Posts: 15
St. Paul, MN, USA
I really appreciate everyones help.

Brian



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