1/0 awg with 200 amp main breaker

[mnahrgang]

Originally Posted by pabernathy

The reality is the 2 AWG is only good for 100A as you have stated. You put on the report the capacity but their is another issue...you provided the weakest link but the new issue is the se conductors are not rated for 125A...that would need a 1/0 minimum based on 310.15(B)(6). so this should also go on the report.

So if the meter is rectangular (200 Amps), and the main breaker is 125 Amps: The sec (between the two) which is rated at 100 Amps is too small? And that is an issue correct? What is the potential harm in such a layout? (The house was 60 years old.)

[Jeffrey R. Pope]

The potential harm is that you could over-load the SEC without tripping the service breaker.

The house could be drawing nearly 125 amps (throughout its circuits or in a short-circuit condition) and not trip the breaker. The SEC (rated at 100 amps) is your "weak link," and could burn up.

[mmixson]

Guys I've run across something similar on new construction this afternoon. Maybe I'm just and idiot, and that's probably the case, but the panel is rated 200, the main disconnect is 200 and the underground service entry is 1/0 Aluminum. Meter is not on but similar construction in the neighborhood is using a meter rated for 200 amps. Here's the pic?? What am I missing besides some brain matter?

[Jim Port]

Are you are asking about the conductors coming from the underground to feed the meter? If so these are sized by the power company, which operates under a different set of rules than the NEC.