Confused about a NEC article.

[jdavis273]

I'm working on getting my masters license,I've read mike holts nec prep book cover to cover,but thought it would be a good idea to take a local course also before i tested.The instructor for the course says that if a test question states,WHAT SIZE THWN WOULD YOU NEED TO FEED A MOTOR THATS RATED 50 AMPS.he says that i have to go to the 75 degree columb of table 310.16 for the answer because they told me thwn insulation.But the way i understand it you have to use the 60 degree columb unless it specifies the terminal rating in the question,if it's below 100 amps.Im not sure what to do on these questions during the test now.Any advice

 

[celtic]

IMHO, use the 60?

 

[nafis]

calculate your load first. find your total amps then proceed accordlingly.
60 degree if less than 100amp or 75 degree if above 100amp. pay attention to the insulation type on each column you have to use it if the question ask to do so .

 

[resistance]

...........if they only list the one from the 75 or 60 degree column, then you are sailing smooth!

 

[ryan_618]

If the motor is design B, C, or D the 75 column can be used. See 110.14(C)(1)(a)(4).

 

[Wes G]

You will always start with the ampacity of the specified conductor and figure any adjustments from that figure. You always end by making sure the adjusted amperage does not exceed that allowed for the wire sized in accordance with the temperature rating of the terminal landed on.

Wes

 

[Pierre C Belarge]

If the motor is design B, C, or D the 75 column can be used. See 110.14(C)(1)(a)(4).

As Ryan has posted, you will reference this section number. Do not forget that there are a number of conditions listed there as well.