If I use a 20 amp breaker and 12/3 wire as a home run, can I use the black hot wire for the outlet circuit & use a 15 amp breaker for the red hot for lights and use 14/2 for the lighting circuit? Terry
Hi Terry. Thank you for asking your question on Just Answer. If you use 3 conductor plus ground wire for 2 circuits, sharing the neutral, you are supposed to connect the two hot wires (black and red) to a double pole breaker. This is to ensure that turning off the breaker for one of the hots removes all power from both circuits, including the neutral wire.
That being the case, you would have to have the same amperage rating for both of the hot wires. If you are trying to keep costs down by using smaller wire for the lighting circuit, you could also use #14 wire for your outlet circuit, and protect it at 15 amps, rather then 12 wire on a 20 amp breaker. I understand the reasoning behind using 20 amp and 12 wire for outlets, but even at 15 amps and 14 wire, you will be unlikely to overload and trip the outlet circuit. The other option is to use all #12 wire for both lights and outlets if you are running a multiwire circuit and protect the outlets at 20 amps.