Motor SF factor

[PE blues]

When motor Service Factor is given, in order to get the branch rating, do we multiply the NEC stipulated percentage with the Service factor or just use NEC % motor Full load amps required for branch circuit rating?

 

[knight1fox3]

Have you come across any problems where the SF was anything other than 1.0? Typically a service factor above 1.0 allows the motor to be run at a slightly higher HP output. For instance, if a 2HP motor has a 1.15 SF, the motor can be slightly overloaded to produce 2.3HP without damaging motor (though shortening its lifespan). The current needed to do this will be slightly higher than nameplate. However, when dealing with the NEC in doing motor calculations, I would use the standard table current values.

 

[PE blues]

The problem I saw had SF=1.0, but I was curious if how the calculations would change if it is >1.0

 

[stedel]

From 2011 NEC, 430.32-A.1

The device shall be selected to trip or shall be rated at no more than the following percent of the motor nameplate full-load current rating:

Motors with a marked service factor 1.15 or greater: 125%