1) E3303.3 requires that all electrical equipment be listed. This is not even a possibility, much less a good idea. Many items of an electrical installation do not have a standard by which they can be listed, so compliance with this requirement is impossibility.
2) E3304.2 requires a minimum interrupting capacity of not less than 10,000 amperes, where the NEC permits 5,000. This is a foolish conflict, as overcurrent protection devices should be selected based on the available fault current, not an abstract number. The number 5,000 is selected in the NEC to mirror the UL listing requirement.
3) E3305.2 governs dedicated electrical space. The IRC addresses only the clearance above the panel, whereas the NEC addresses the clearance both above and below the panel.
4) E3603.2 permits the small appliance branch circuits of a kitchen to supply any and all receptacles in the kitchen. This would allow the dishwasher, disposal and trash compactor to be on the same circuit as the kitchen countertop receptacles. The NEC prohibits this practice, for good reason.
5) E3603.3 requires at least one 20 ampere circuit to supply all of the receptacles in the laundry. The NEC permits a combination of both 15 and 20 ampere circuits for this purpose.
6) E3604.1 permits a reduced conductor size for feeders supplying a dwelling unit, as does the NEC. The IRC, however, only permits this reduction if the feeder circuit serves 100% of the dwelling unit load. The NEC permits this reduction for any feeder serving a dwelling, regardless of the percentage of the load it is serving. This conflict makes for a significant increase in cost for both the installer and the end user.
7) E3604.3 contains a table that requires a separate and different load calculation that service conductors. The NEC contains only one table, as that should be all that is needed.
8) E3604.7 requires all conductors to have overcurrent protection at the point where the conductors receive their supply. Because of this, the common installation practice of installing ?feeder taps? is not permitted by the IRC.
9) E3703.2 Requires a warning ribbon for all underground service conductors, whereas the NEC requires this only where the service conductors are directly buried without a conduit system.
