Motor branch circuits

[Rets Instructor]

I was watching Mike Holt's DVD on motor installation and he said that for motor branch circuits, ampacity can be taken from the 75C column of 310.16 as allowed in 110.14 however, it looks to me like that is only the case for NEMA design B, C, or D. Am I missing something? He also said that feeder ampacity (for multiple motors and other loads) can also always be chosen from the 75C column. I always thought the 100a or less, #14 thru #1 rule applies requiring 60C ampacities. Any clarification?

 

[Dennis Alwon]

I was watching Mike Holt's DVD on motor installation and he said that for motor branch circuits, ampacity can be taken from the 75C column of 310.16 as allowed in 110.14 however, it looks to me like that is only the case for NEMA design B, C, or D. Am I missing something? He also said that feeder ampacity (for multiple motors and other loads) can also always be chosen from the 75C column. I always thought the 100a or less, #14 thru #1 rule applies requiring 60C ampacities. Any clarification?

Read that section carefully. If the terminations and the wire insulation are 75C or better than we can use the 75C column-- excluding nm cable and se cable in the 2008 nec.

 

[Rets Instructor]

I understand the terminal temperature rule. I was just wondering about his blanlet statement that for "all" motor installations, the 75C column is used. He apparently either mis-spoke, or is assuming that all motor equipment has 75C rated terminals.