Running from my house panel to my garage I currently have a 12-3 wire split into two circuits with a common ground, each circuit has a 15 amp breaker. I know 12 gauge wire can support a 20 amp but my question is can I run one circuit on a 20 amp breaker and the other on a 12 amp breaker with a common ground.
My reason for doing this is I want to run a slightly larger heater in the garage on colder days when I am working in there and once in a while it will trip the 15 amp breaker when it kicks on.
The garage currently has one 15 amp outlet on one circuit (the one I want to change to 20 amp) and the other circuit has a two 15 amp outlets and 2 50 w lights.
I hope this is clear. I look forward to the answers