What column to use

[timmons101]

There are 3 columns on 316. Thhn is only in one of them. So do I only use the 90 degree column for thhn.

 

[infinity]

Depending on the application you might need to use the 90? C, 75? C or 60? C column for THHN. Do you have a specific example of what you're trying to size?

 

[me=mc pulled]

Yes you use the 90 deg. col.for derateing thhn but remember when you are sizeing the wire for a ckt. you must know the rateing of all parts in the ckt..If the breaker or equipment is only rated for 60 deg. than you must use that column.

 

[raider1]

Take a look at 110.14(C).

Chris