I am finishing my kitchen remodel but I had run the electrical supply lines previously, before I finished my basement, when its ceiling was exposed for routing. For some reason I can't exactly recall right now, I ran a 12/3 cable to supply the dishwasher and garbage disposal. I now think it was not the best choice because they should either be on a 15A (which corresponds to 14 AWG) dedicated circuit each or share a common 20A circuit. In other words, 20A each is an overkill and might be an overload on the side of the panel. The breaker at the panel is a double 20A where the switch is shared between the two circuits, in other words they are bother either on or off but can't be in a different state, because they share the same cable and the same neutral (I think this is called a multi-wire branch circuit).
Even though this may be perfectly legal (is it?), I prefer to go optimal and not provide more amps than can realistically be drawn. The dishwasher draws a maximum of 10.9A and the garbage disposal 5.9. I am asking for help to decide among several possible recourse options, assuming that the 12/3 cable going in cannot be changed as the distance is very long and blocked by drywall the entire route:
- Even though the wire is 12 AWG, replace the 20A double branch breaker with a 15A double branch circuit and the 20A rater terminal outlet, which both appliances share, with a 15A, making it effectively a 15A circuit for each appliance.
- Make it a single regular 20A circuit by simply not using the red wire inside the cable. Is this allowed?
- Leave it a 20A double branch circuit as is.
The main reason I would like to make this change is so that the main panel looks as elegant as possible and not overloaded so that a future buyer's home inspector doesn't ask any unnecessary questions. It is not so much a safety issue (or is it?) as it is about perception management.