Unventilated concrete trough

Jc.Sea

New User
Location
USA/CAN
Occupation
Engineer
My client is interested in removing ventilation and reducing the wire size within a concrete trench or trough.

Could it be confirmed whether the NEC (or California CEC) permits the installation of
6 sets of 4 parallel 3c-2/0+G XHHW conductors (480V, 3-phase, 140A FLA continuous load) in a triangular configuration, with 2.15 OD spacing, placed on racks within an unventilated concrete trough(50ft length, 5 feet in width and 4 feet interior depth)?

I felt the heat in this trough already, but can I go even with a smaller wire?
Or NEC does not allow it to be non-ventilated.

NEC 392.80(2)— is this the correct section to reference? since this is rack mounted, or should another part of the code be considered?

Thank you all.
 
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