I recently remodeled a porch and upgraded the electrical for just a few floodlights and plugs, probably less than 1400 watts. I ran a 10/2 with a ground to this remodel, off of a 30 amp breaker at the main. The wire size had to do with distance from the main. I then installed a small subpanel on the porch with one 15 amp breaker. I used 14/2 with ground throughout this project, with 15 amp plugs.
Your thoughts
Porch remodel with improved electrical service
porch
Best Answer
Nope. You need a 20A breaker at the main.
When you upsize wire for long distance, you do not also upsize the breaker. There's no reason to; the long distance doesn't consume any additional amps, it consumes volts. Amps remain the same.
A 30A breaker is not legal on a circuit supplying 15A or 20A breakers, you can only have 30A receptacles on that.
If you really want to get 30A worth of use out of the #10 cable, then add a subpanel at the porch, and you can have 2 or more 15/20A circuits coming out of that sub. You are allowed to install a 120V subpanel, and that requires a 3-wire connection.