Here's my question since it maybe confusing. Correctly there is a 12/2 with a ground running from panel in basement to the second floor AC. The outlet for the AC was wired 120v 20amp. I am going to install a ductless mini split and need 15amp 240v. So what I want to do is change the single pole breaker to a two pole breaker move the neutral to the breaker tape it red and change the outlet to a disconnect. So far I have no issues doing this.
My question or concern is how can I made sure there's no additional outlets/lights Daisy chained before the end of the line before I make it 240v. I obviously checked the normal ways and have turned the breaker off for 3 months and haven't noticed anything not working.