Residential - Commercial service conductor size

[Stevenfyeager]

Hi, For residential service entrance conductors, 2/0 CU carries 200 amps in NEC, but for commercial, I need to use 3/0 CU (250 AL) correct? (table 310 16, 75 degree column). Thanks

 

[jumper]

Hi, For residential service entrance conductors, 2/0 CU carries 200 amps in NEC, but for commercial, I need to use 3/0 CU (250 AL) correct? (table 310 16, 75 degree column). Thanks

Correct.

You could possibly use 4/0 AL in commercial if your calculated load is 180A or less, including any derating and correction factors.
240.4(B) would allow a 200 breaker in that case.

 

[iwire]

Hi, For residential service entrance conductors, 2/0 CU carries 200 amps in NEC,

Not exactly.

Commercial or residential 2/0 copper can only carry 145 amps @ 60 C, 175 amps @ 75C or 195 amps @ 90c.

However, the NEC allows us to protect it at 200 amps for certain residential applications. The calculated load still must be less than the wires rating.

but for commercial, I need to use 3/0 CU (250 AL) correct? (table 310 16, 75 degree column).

Yes, or as Jumper mentions you might be able to use 4/0 AL.