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ropeguru
Premium
join:2001-01-25
Mechanicsville, VA
reply to Killa200

Re: The renovation continues ... today new 400 amp service!

said by Killa200:

I'm assuming by the 350kcmil marking on the underground feeder wires from the utility. 250kcmil aluminum is rated for 250amp @ the 75c rating, which is more than likely what those terminations are rated for.

But he was not referencing the terminations. He stated that the service wire was not rated for 400 AMPS. Additionally, would you ever expect one leg of a residential single phase to have to supply a full 400 AMPS? Wouldn't the total be more balanced across both?


Killa200
Premium
join:2005-12-02
Southeast TN
Reviews:
·Charter

Fixed a typo above and added my thoughts. While he wasn't referring to the terminations, you have to in order to get the correct handling capacity of the feeder run. The wire alone isn't what determines what it can carry, but also what it terminates into.

If you want to focus in the wire alone and in all technicalities, it as well isn't rated for 400 amps, even at 90C.

Do i ever expect 400amps @ 240v worth of load on his service regularly? I have no idea, but it isn't plausible, as if a load calculation pushed him to that point they would have oversized again.

IN technical terms is the service setup as rated? No. But the utility also isn't bound by the NEC, but their own set of guidelines on how to install things.



alkizmo

join:2007-06-25
Pierrefonds, QC
kudos:1
reply to ropeguru

Looks like they used the same type of wire for the overhead (which can be 400A for neutral support overhead).



cdru
Go Colts
Premium,MVM
join:2003-05-14
Fort Wayne, IN
kudos:7
reply to Killa200

I was just going by the wire being stamped 350 kcmil, which by NEC table 310.15(B)(7) seems to indicate a max of 300 amps. I was under the impression that the service wires had to be at least as big as what the combined main disconnects protected to, but maybe not.

said by Killa200:

But the utility also isn't bound by the NEC, but their own set of guidelines on how to install things.

Aren't service entrance cables covered under NEC, but not transmission lines?


Killa200
Premium
join:2005-12-02
Southeast TN
Reviews:
·Charter

said by cdru:

Aren't service entrance cables covered under NEC, but not transmission lines?

Hmmm, that may be true. I'm going to remit on an answer from that and instead hope whiz or nunya chimes in.