thru-roof feeder

[Toros]

Hi
What is derating value for feeders (50ft of 3/0 thhhn,cu to the load of 170A) across the roof in Los Angeles

should I use 90 deg column of 310.15 b 16 or,
310.15b2A

Tanx

 

[kwired]

For rooftop locations you need to find out what ambient temperatures are for the area - informational note tells us one source for such information may be ASHRAE Handbook ? Fundamentals.


Then you need to add values from table 310.15(B)(3)(c) to the ambient temp, depending on distance above roof the conductors are located.

You must make ampacity adjustments based on the temp you come up with from the above steps.

 

[texie]

Here is an excellent paper with the data you need: http://www.copper.org/applications/electrical/building/pdf/rooftop.pdf

 

[Toros]

Here is an excellent paper with the data you need: http://www.copper.org/applications/electrical/building/pdf/rooftop.pdf

Tanx