Table 430.52

[624]

If I have a moter FLC 10hp 208 volt is 30.8, sizing inverse time breaker 2.50% table 430.52.
FLC 38.8x2.50%= 77 amps next size up 80 amp. My wire size would be FLC amps 30.8x1.25=
38.5 number 8 awg wire, I’m I doing this right it seems wrong 8 awg wire on a 80amp breaker?

 

[LarryFine]

If I have a moter FLC 10hp 208 volt is 30.8, sizing inverse time breaker 2.50% table 430.52.
FLC 38.8x2.50%= 77 amps next size up 80 amp. My wire size would be FLC amps 30.8x1.25=
38.5 number 8 awg wire, I’m I doing this right it seems wrong 8 awg wire on a 80amp breaker?

Read 240.4, then 240.4(G) and Table, then back to the appropriate part(s) of 430.

 

[Dennis Alwon]

Remember that your motor will have overload protection so the wire is protected. The breaker is there for short circuit or ground fault protection only.

 

[Strathead]

Larry sent you to the appropriate code section to tell you that the answer to your question is yes. Dennis told you why. I thought I would let you know because sizing a wire that way is scary until you know you are right. I have only seen an engineer size a motor feeder to these tables a couple times in my career. They usually size them to the feeder breaker. A similar over-engineered thing is the size grounding electrode conductor (250.66) for a concrete encased electrode our a pair of ground rods.

 

[624]

Ok thanks a lot