I'm in an American house sitting in a jurisdiction that applies NEC 2014 unaltered. I've got a home office room with all the outlets on one 20A circuit. It is legal to 2014 code in all respects.
Who cares why, maybe I collect European pinball machines, maybe I just need a lot more power in the room, between my server grade PC and window air conditioner. I decide I want to convert that outlet circuit to 240V and install all NEMA 6-20 outlets. Pic
It's wired in NM 12/2 but I mark the white wire with red tape at every accessible point. Ground but no neutral. I have the requisite AFCI or GFCI breaker if required (whatever the circuit had before).
What code of Code compliance issues am I going to run into? After all, I do have outlets in all the right places.
Now suppose I also wanted to power a permanently installed light fixture. I want to use one rated for 240V. Any code issues there?