200a underground service

[Cnorris0916]

Per table 310.12 seems like 4/0 aluminum should be the correct size needed for a 200a underground feeders from a meter main to the sub panel in the house? Roughly 150ft away.

 

[Dennis Alwon]

I believe you mean 310.15(B)(16). A residence is allowed a factor of 83% so for a 200 amp service you only need a conductor rated 166 amps. At 75C 4/0 AL is rated 180 amps so it is fine. There is a bit of Voltage drop you may want to consider if the calculated load is very high.

 

[Cnorris0916]

Yes sorry, as for voltage drop per the calculation at 200amp(s) it's still over the 166a so I figured it won't be a problem. Just double checking. Thanks for the input!

 

[tom baker]

And the NEC is very conservative on load calcs, your connected load will likely be much less

 

[infinity]

Also even without the 83% rule you can go to the next standard size OCPD which is 200 amps on a #4/0, 180 amp conductor.

 

[don_resqcapt19]

I believe you mean 310.15(B)(16). A residence is allowed a factor of 83% so for a 200 amp service you only need a conductor rated 166 amps. At 75C 4/0 AL is rated 180 amps so it is fine. There is a bit of Voltage drop you may want to consider if the calculated load is very high.

Dwelling unit service conductors, and the 83% rule, were in 310.15(B)(7) in the 2017 code but those rules moved to 310.12 in the 2020 and Table 310.12 is correct. They brought the table back, so you only need to use the 83% rule were the you have to adjust or correct the service conductor ampacity for more than 3 conductors in a raceway or cable, or for elevated temperature.