If you have 10 3 wire from your electric panel and it is going to an air conditioner disconnect should the white wire be caped or grounded?

Answer 1

The white wire is neutral. If you need 110V at whatever this is supplying you need to connect it to neutral (Not ground). If you only want 220V you can simply cap it with a wire nut at both ends and leave it unused. If you can connect it do neutral, do so. The next person will expect it to be neutral and it is better to have it tied to neutral than floating. If in doubt, go to your local home improvement center and buy a book. It will teach you how to do it legally and will serve as a handy reference during the job. Finally, I will add do it right or don't do it at all. If you are negligent you could easily kill someone through fire or electrocution. If you read and do your homework and learn what it required you may find that small electrical repairs can be quick and easy. If you can't understand what you need to do hire an electrician. The cost of a professional is not worth the time you will waste if you don't understand what you are doing and the danger therein.

Answer 2

#10-3 w/ Ground NM cable is made up of 4 conductors, a black, red, white and bare or green wire. In a 240 volt air-conditioner circuit the white wire isn't needed and shouldn't be connected to anything on either end. If your cable doesn't have a bare or green ground wire, then, by all means, use the white wire for the ground and mark the white insulation green on both ends so its use is understood by the next person. Don't just leave the white wire floating. Connect it to neutral in the panel and cap it at the airconditioner if not needed. This way if someone else comes along behind you and connects something else to this circuit without checking the panel, everything is as it should be. Since neutral should be bonded to ground in the panel having it connected to neutral in the main panel is harmless.