motor ocp

[misterbill1972]

I am protecting a continuous duty motor. I am basing the conductor size on FLA + 125%. I will be using a .76 correction factor for ambient temperature per inspectors requirement. It makes sence to size my conductors after the correction factor. NEC 240 makes me wonder if I am right. Am I ???

 

[Lcdrwalker]

Depending on the motor it should be FLA + 25% or 125% of FLA.

 

[John Valdes]

I have always used motor namplate FLA x 1.75 for breaker or fuses and nameplate for conductors. (3 phase induction motors). Have I been doing this wrong......Thanks John

 

[jim dungar]

I have always used motor namplate FLA x 1.75 for breaker or fuses and nameplate for conductors. (3 phase induction motors). Have I been doing this wrong......Thanks John

Conductors must be sized per the NEC tables for motor amps not the nameplate. typically, the minimum sizing would be table FLA*1.25.

Overcurrent protection (running/overload) must be provided based on 100% of nameplate amps, with actual selection per the manufacturers instructions.

A good starting point is to use 175% of nameplate amps for the short circuit protective device sizing.