help Sizing generator conductors

[GlennG]

I am having a little dispute with my co worker about sizing the conductors on a 36 kw Generac generator. He is saying 1/0 , i think 2/0 copper or 3/0aluminum.I went by this: 36000/240= 150amps x 1.25%= 187.5 amps. The generator has a 175 amp Breaker in it. Can anyone tell me if i am on the right track here?

 

[kingpb]

#2/0AWG copper or #4/0 AWG Aluminum

 

[charlie b]

I don't need to look at your math. A 175 amp breaker is not allowed to protect a wire that is only rated for 150 amps. So a 1/0 copper is not adequate for a circuit that has a 175 amp breaker.

But just out of curiosity, since I did in fact look at your math, what is the reason for your 125% factor?

 

[GlennG]

I was under the impression that a generator needed to be sized at 125% because its a continuos load. Is that not correct? Im a little confused also how a 36kw generator has a 175 amp breaker in it?

 

[GlennG]

I was mistaken, looks like 115%, according to 445.13
So 150x115%= 172.5 amps. So if you round that up to the next size you get 175 amps. Am i correct in my train of thought?

 

[Cavie]

I don't need to look at your math. A 175 amp breaker is not allowed to protect a wire that is only rated for 150 amps. So a 1/0 copper is not adequate for a circuit that has a 175 amp breaker.

But just out of curiosity, since I did in fact look at your math, what is the reason for your 125% factor?

310.15 (B) (6)