Dude. Ohms law is just a rough estimate. Don't use it. Look at the name plate on your ballast. If it doesn't haven't a metal nameplate on it, then find a PDF on your specific ballast. Falling that, use an ammeter on the hot wire. Either way you slice it, you need an exact amp rating that your ballasts draw. Ohms law will not get you there.
16 Amps is the maximum you can draw on a 20A circuit with continuous loads. 16.1 Amps and you need to bump up to a 30A breaker with #10 wire. Don't fuck around with that. I mean, ultimately, it's up to you. If your drawing 17A and want to use #12 and a 20A breaker than go ahead, but I wouldn't.
Thanks for that. It really wasn't about pinching pennies, the difference is like $15 more for the 10A stuff, no big deal. It was more of about trying to keep anything from looking too suspicious. It was more of IF I can run 12/2 with a 20W breaker for 2 ballasts only, then I'd do that. Seeing as how its so close cut, I'm just going to go with the 30. It's just a really small bedroom, and a whole extra 30A circuit in the room might raise an eyebrow or two. Then again that's after I'm gone, but still.
I think your not fully grasping the concept of a flip/flop. 2 ballast that run 4 reflectors (but not at the same time). Yes, the 2 ballasts run 24/7 but without a timer to flip the relay contacts, how are the other 2 reflectors ever going to fire up? Do some research about flip/flops here on Icmag.
I really do get the concept of the flip/flop, it's been my latest obsession. I only wish I had knew about them earlier. I just wasn't sure about the timer, I knew the timer was just handling the flip, but I didn't know how much power was actually going through the timer. Going back and reading it, I really didn't type that up the way I should have. For some reason I was under the impression that the timer was plugged in between the receptacle and the flip box itself. My mistake.