motor question

[buck33k]

Is it safe to say that with modern electrical equipment and a new motor, you would use the 75 degree column of 310.16 in determining branch circuit conductor size?

I ask because I was watching a motor video and the 60 degree column was used several times. That could have been a worst case scenario in the event of terminations rated only 60.

My particular job involves a 3ph 208v 7 1/2 hp motor.
FLA 430.250 = 24.2 x 125% = 30.25 = #10cu. (per 310.16 75 column)

Thanks
Buck

 

[cpal]

You may use the 90 deg column but the load current on the conductors may not exceed the 75 deg ampacities. But pay attention to 110.14 (C) (4).

Charlie

 

[tom baker]

Art 430 was clarifed recently to indicated that motors are designed for 75 Deg C wire but its not a requirement to use the 75 deg ampacity column.
Motor ampacity is sized at 125% of the motor FLA, pumps are required to be 140%, most miss this requirement. For motors that start and stop frequently, use a larger wire. Most of the overheating occurs at the overcurrent device.

 

[buck33k]

Thanks Charlie for the reference and Tom for the responce. I appreciate it.