I recently ran some 12AWG wire to an outside disconnect to use with a 230v AC condenser unit. I used 3 conductor plus ground, but when I went to hook it up, all that was required were 2-hot and a ground. So after connecting my RED (L1) and BLACK (L2) wires, does it matter if I use the WHITE wire as ground, or the bare ground wire - as long as the correct wire is grounded at my sub-panel? What is the convention when you have 3-conductors and ground wire? Should I tie them both to ground at my sub and condenser unit? I haven't applied any power yet.

 

The white/neutral wire is not needed. Put a wire nut on it and tuck it out of the way.

 

Thanks PJ. That's exactly what I was planning on doing.