Overcurrent Protection Per 240.4B

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Is the following installation legal per 240.4B

225A Breaker in a MDP feeding a 200A MLO panel (yes I know that isn't allowed per code, assume the panel is suppose to be 225A rated) using 3/0 copper THHN conductors (this is what I'm not sure of).

According to 240.4B(2) you are allowed to round up if the ampacity of the conductors does not correspond with the standard ampere rating of a fuse or a circuit breaker. In this situation 3/0 copper is rated for 200A which in my mind is a standard size so you can not round up. If it was fed with say 250 aluminum which is rated for 205A then you could round up to the next size.

Assuming the feeder does not feed a multi wire cord and plug receptacle circuit and we are under 800A does it meet requirement (2)?

An engineer for this installation is stating that you are allowed to round up to 225A because it is the next standard breaker size based on the ampacity of the copper conductors.
 
I'm trying to understand the his logic. If the conductors are rated for 200 amps, which is a standard size, why would he think that you could go up to the next higher size OCPD? 240.4(B)(2) seems quite clear to me.
 
Rounding up to the next standard size is for breakers, not conductors.

Hand him the good book, NEC 2005, and ask him where conductor rounding up is acceptable.
 
3/0.

3/0.

I had a post similar to this a few days ago (although it was more in reference to xfmr. Secondary conductors) there are a couple here in the office I currently work in that would say 3/0 is ok because the specifications called for 90?C wire at 3/0 that?s rated for 225A. I do not buy into this theory that the conductor specified is rated for 225A because the second it hits the lugs (typically rated 75?) that would determine the conductor ampacity you could carry thru to the device. Maybe I?am all wrong here but to me the conductor (3/0) is used for 200A if connected to a 225A brkr. It?s not in compliance. And I all wrong here??:smile:
 
Thanks

Thanks

Thanks for your help on this topic. I had a feeling that his interpretation was incorrect. Someone showed me in the 2005 handbook that it specifically gives an example right after the code section of #3 copper being rated for 100A @ 75 degress and you can not roundup to the next size; so that along with your confirmations was greatly appreciated.
 
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