How is determining the derating factor and ampacity of 11 cables on a 20A circuit NOT related to determining ampacity, the one singular section of code where engineers are explicitely allowed to deviate?
At any rate, NEC is not the code, NEC is just the code invoked by the locality. The locality always has the final say, and the AHJ will grant engineers a lot more slack than they will for if they have to accept the liability themself. In my area, certain inspections can we waived completely if an engineer stamps a letter attesting to proper design and installation. Plan reviews are still important; I know it's hard to believe and very rarely happens, but engineers can make mistakes too!
Edit: NEC 90.2(C) and 90.4 states explicitely that AHJs can allow deviations.
[This message has been edited by SteveFehr (edited 02-07-2007).]
