Sizing breaker for 1/2 HP 480V/3ph motor

[greenspark1]

We have an odd situation with two small 1/2HP three phase 480V motors. They have overload protection but I need to size the OCPD/circuit to them. #12 wires clearly are fine, but per 430.250 the FLA is 1.1A. Per 430.52 this means the max breaker size is 1.1 * 2.5 = 2.75 A. The smallest standard breaker is 15A, can I round this all the way up to a 15A breaker? Otherwise I'd need to protect it with a FDS and some small fuses (3A is next standard size). The motor cut sheets say nothing about short circuit protection and the rep doesn't know either. Thanks for any input.
I'm currently thinking one 20A circuit with one 3A FDS per motor.
Don't get me started on why they were selected at 480/3ph.

 

[kwired]

15 amp breaker is fine. It protects from short circuits and ground faults, your motor overload protects both the motor and the branch circuit conductors from overload.

 

[greenspark1]

15 amp breaker is fine. It protects from short circuits and ground faults, your motor overload protects both the motor and the branch circuit conductors from overload.

I would like to agree, I just don't see it in the Code.

 

[petersonra]

I would like to agree, I just don't see it in the Code.

look harder.

hint - a good place to look would be 240.4(B).

 

[kwired]

Another limiting factor could be the motor controller, especially the overload unit(s). It may have a maximum for the branch circuit or supplemental SC/GF protection.

 

[greenspark1]

Another limiting factor could be the motor controller, especially the overload unit(s). It may have a maximum for the branch circuit or supplemental SC/GF protection.

Good point. I rarely see that called out on motors though, typically just air handlers and similar.

 

[augie47]

Another limiting factor could be the motor controller, especially the overload unit(s). It may have a maximum for the branch circuit or supplemental SC/GF protection.

excellent point and an often overlooked requirement.

 

[infinity]

Another limiting factor could be the motor controller, especially the overload unit(s). It may have a maximum for the branch circuit or supplemental SC/GF protection.

Could the branch circuit be smaller than 15 amps?

 

[kwired]

Could the branch circuit be smaller than 15 amps?

Yes, NEC basically says it not need be less then 15 if a breaker - but then there is 110.3(B) and the instructions for the item that may have lesser limits.