Feeder question

[joeyos]

I do mostly plan and spec work. I haven’t had to size feeders in a long time. Please help.
I have a 3 phase panel 120/208 4 wire being fed from a 400 amp breaker in the MDP 250 feet away. The calculated load is 175. The job has been spec’d with a 400 amp sub panel and they purchased the panel before I even signed the contract. I wish to use parallel aluminum feeders. My question is how to size them?
I think 250 AL in parallel will suffice. Am I wrong?

 

[texie]

I do mostly plan and spec work. I haven’t had to size feeders in a long time. Please help.
I have a 3 phase panel 120/208 4 wire being fed from a 400 amp breaker in the MDP 250 feet away. The calculated load is 175. The job has been spec’d with a 400 amp sub panel and they purchased the panel before I even signed the contract. I wish to use parallel aluminum feeders. My question is how to size them?
I think 250 AL in parallel will suffice. Am I wrong?

Yep, 250 AL in separate raceways would work.

 

[infinity]

According to my VD calculator parallel #3/0 Al will work at 3% but the conductors are too small. #4/0 Al in two raceways and next size up rule will work.