Service size wire

[Southern Charm]

If you built a 400 amp residential service wouldn’t the conductors between the utility point of attachment ( overhead ) and the meter enclosure need to be a minimum of 400 copper or 600 Al. ? Then if you wanted to go from the load side of the meter ( double lugs ) to two 200 amp disconnects with say 4/0 Al to each panel that would be fine. Co worker told me the line side meter wire is decided by a load calculation. I say no, it’s decided by the OCPD. Another example, if you had an 800 amp commercial service with 4 disconnects at 200 amps each you could parallel two sets of 500 copper. I’m I missing something?

 

[augie47]

Yep. If you go to multiple service disconnects the common service conductors must be size to the calculated load (230.42)

 

[Southern Charm]

Yep. If you go to multiple service disconnects the common service conductors must be size to the calculated load.

 

[Southern Charm]

Always learning, thank you! Code ref?

 

[wwhitney]

If you built a 400 amp residential service wouldn’t the conductors between the utility point of attachment ( overhead ) and the meter enclosure need to be a minimum of 400 copper or 600 Al. ?

If it's a meter in its own enclosure, are the terminations rated 90C? If so, then assuming the splice at the weatherhead is also rated 90C, those conductors can use the 90C column. Then 350 kcmil Cu or 500 kcmil Al would suffice.

Then if you wanted to go from the load side of the meter ( double lugs ) to two 200 amp disconnects with say 4/0 Al to each panel that would be fine.

Yes, because the 75C ampacity is 180A, so under 240.4(B) can be protected at 200A. The calculated load on each such feeder segment would need to be 180A or less.

Augie addressed that with multiple disconnects, the common service conductors can be sized to the calculated load, rather than the sum of the disconnect ratings. See the exceptions to 230.90(A).

Cheers, Wayne