This is from the '11 NEC, and yes, it is not Code, but information:
Informational Note: Table 310.15(B)(16) through Table
310.15(B)(19) are application tables for use in determining
conductor sizes on loads calculated in accordance with Article 220.
Allowable ampacities result from consideration of one or more of the following:
(1) Temperature compatibility with connected equipment,
especially the connection points.
(2) Coordination with circuit and system overcurrent protection.
(3) Compliance with the requirements of product listings
or certifications. See 110.3(B).
(4) Preservation of the safety benefits of established industry practices and standardized procedures.
IMHO, you size the conductor to the load. 350Kcmil Copper within the 75 degree col. insulations on a 300 amp OCP is compliant. (No derating factored in) I believe in the real world, the 'calc load' would 'loose' 5-10 amps.
Last edited by HotLine1; 08/27/12 10:25 PM.
