If the lugs for the breaker are not listed or labelled for two conductors of the given size, then it would indeed be a violation. I'm unsure of when this particular code was put into place that requires materials to be installed consistant with the listing and labelling, perhaps as early as '74, but I do not know. It is not unusual for HVAC mechanics, past and present, to have total disregard for the NEC, so many installations may have never passed code at any time! "Home Inspectors" are notorious for "making up" their own code rules, mostly due to ignorance and good intentions. Perhaps you could hire an IAEI certified electrical inspector to give a second opinion?
[This message has been edited by sparky66wv (edited 10-15-2002).]