gc=grounded conductor.
110.3 and 110.14A says the panel needs to be listed and identified for more than one wire per gc screw. isn't there something else somewhere?
if you have two circuits under one screw and loosen it then you would want both circuit breakers off. in a lot of panels it would be hard to trace the grounded conductor to find it's corresponding ugc so you can turn off that breaker also. is there a specific code that says you cannot have two neuts under a screw even if the listing allows it?
