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"?
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