Let's say I want to add a 240 and 120 line to outlets immediately below my subpanel. I have only two slots left. If I run 12/3 cable (black, red, white, and bare ground), can this be done? The first box would be 240 volt, and use the two hots (black and red), and the bare ground, but NOT the white (neutral). The white (neutral) and one of the hots (black) and the bare ground would continue to the second outlet box, which would result in a 120 volt circuit. Is this code? If so, what do I use for breakers? A double-pole 40 amp, or two separate 20 amps? I realize they must be beside each other, so that the black and red hot wires will be on L1 and L2.
If it is a double-pole 40 amp, could the 120 volt line still trip the breaker if overloaded?
Further, could you run the first 240 volt box (black, red, bare ground), then a 120 volt box (black, white, bare ground), and then another 120 volt box (red, white, bare ground)? What breaker combination would you use then?
I would just run a separate line, but my box is running out of space. I should also add that I assume the 240 volt box would NOT be running at the same time as either 120 volt circuit.
Thanks for any info. I know that, logically, this setup would work. But, is it code, and is it wise?