I'm embarking on a re-wiring of my Garage/Workshop. I've identified 3 new circuits I'm adding. I have a large roll of new 12-3 wire, which I'm looking to use up in this project. After completing the wiring I'll be insulating and covering the stud-bays.
I am thinking of running two pulls of 12-3 while I've got easy access, and leaving one of the extra hot wires unconnected (capped), in the box, for when I get around to re-doing my pantry (shares a wall) and want to add a grounded outlet. Running an extra 12-2 would mean putting another hole in each stud along the wall, and I've already got 2 holes in each (50's house with many partial-remodels), I don't really want to turn the structure into swiss cheese.
I have not been able to find anything in the code about leaving one of the wires of 12-3 unused. Do you think an inspector would balk at this? My city uses the most recent version of the NEC code.
I know a 12-3 run needs a double-pole breaker because of the shared-neutral, but what about my theoretical extra wire (with one live circuit, but will eventually require a shared neutral)? Do I just need to run the circuit and wire a dummy outlet? I'd rather not unless necessary.