Is it legal to feed 400amp 480/277v 3phase panel with a 350mcm thw wire?

[SparkyDrew1999]

Old existing panel has to be changed for an updated panel according to the single line but the existing 350mcm thw wire has no indication to be changed. Also the calculated loads on the panel phases are A(226.9amps) B(216.4amps) and C (240.1amps). So, basically the loads are going to be less than 250amps so the 350mcm thw wire should be fine? but then the main breaker is 400amps, so therefore the wire is not under code. but again the engineer did not mention anything about changing the wire. Am I missing a special code or something??? Please help me.

-Drew.

 

[petersonra]

Does not matter what the main breaker rating is as long as the feeder breaker for the feeder conductors adequately protects the feeder conductors.

 

[infinity]

What is feeding this panel a feeder or a transformer?

 

[gadfly56]

Does not matter what the main breaker rating is as long as the feeder breaker for the feeder conductors adequately protects the feeder conductors.

Good point. Also, supposing that isn't the case, an RFI is in order. Actually, an RFI is in order anyway. The OP might not have access to the other end of the feeder to confirm the feeder is properly protected.

 

[Little Bill]

I think some are assuming here as I didn't read where the OP mentioned feeder. It could be service or feeder so OP needs to confirm which before an accurate answer can be given.

 

[SparkyDrew1999]

Thank you very much for taking your time to help me out! The panel is being feeded by a SES. Also, this issue was resolved but man it was a total fiasco. Long story short. There are 2 separate electrical sub-contractors in this industrial job, One is working for the owner of the building and we are working for the renter. We were working with the original blue prints approved by the city and the other team was working with an updated blue print that had all the fixes and corrections but was not approved by the city. So, you can imaging the argument between the 2 electrical sub-contractors when the other team told us that they were going to install an 800amps 480/277v panel next to the 400amps 480/277v panel that we were working on and we were like there is not such a thing in our blue prints. Anyways, we talked out and fixed the miscomuniction between the 2 teams...