I am wondering about the 240 connection to my AC unit. It was originally wired using 12/3 wire with the copper ground snipped off. It was suggested I should rewire it with 12/2 wire but I have a question. Where do I connect the bare copper ground in the pannel. To the ground bar or to the neutral bar where the white wire would normally go

Thanks

If you have a separate grounding bar, that's where the bare ground wire will go. The other terminal strip is for the neutrals when running 120 volt circuits. What size unit do you have? Did you check to be sure 12/2 will be large enough? If your unit is 36,000 btu/hr (3 ton) or larger, you'll probably need a 30 amp breaker with #10 wire.