230.90(A) Exception 2 and 240.4(B)

[hurk27]

Ok I have a question to this and part of it is because I just bid a 45 kva generator install on a 200 amp service and I can't see that using 2/0 is allowed (commercial) since 3/0 has a 75? rating of exactly 200 amps in table 310.16?

So what stops us from using 230.90 exception 2/ 240.4(B) from using the next size up on 2/0?
or any under size wire for that matter?

The post below and the post I made is where this has confused me:
Post 51 in "50 most common NEC violation thread

I kind of understand the 500 verses the 600 as 600's are over 400 amps and 500's are just under, but still kind of does not make sense to allow it if the next size wire up will handle the rating of the breaker, just like with 2/0 and 3/0?

 

[jwelectric]

I think that the biggest issue here is that 230 will not apply to a generator install as the conductors from the generator are feeders and 230 addresses services :?

 

[hurk27]

I think that the biggest issue here is that 230 will not apply to a generator install as the conductors from the generator are feeders and 230 addresses services :?

What about the service conductors from the meter to the service rated ATS?

 

[RUWired]

So what stops us from using 230.90 exception 2/ 240.4(B) from using the next size up on 2/0?
or any under size wire for that matter?

2/0 cu. at 75 degree is good for 175 amps. 240.6 lists a 175 amp standard breaker, so no rounding up allowed.

 

[hurk27]

2/0 cu. at 75 degree is good for 175 amps. 240.6 lists a 175 amp standard breaker, so no rounding up allowed.

Ok I guess I need to refresh my memory banks' as why I didn't even think of this I have no idea, now it just slapped me in the face as I knew this.:slaphead:

Be having allot on my mind lately with my house.

Thank's