Ground vs Neutral Wire

garlicjimMarch 1, 2010

I'm running a 10-2 w/ground wire from a sub-panel to the outside of the house for the purpose of A/C installation. The A/C guy said it didn't need 4 wires (ground plus neutral).

Question: Does it matter to which bar I attach the bare copper wire?



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10/2 cable has two current carrying conductors and a ground wire. Straight 240v circuits do not use a neutral wire. You just have two hots and a ground. Don't worry, this confuses a lot of people. In your case you would use the white wire in the cable as a hot. The wire should be "re-identified" so that everyone else who works on the circuit knows what is going on. Use a black marker or paint marker to color the last few inches of the wire.

In case you made a typo, 10/3 cable has three current carrying conductors (typically black, red, white) plus a ground. In that case you would use the red and black and just cap off the white at either end.

    Bookmark   March 1, 2010 at 3:20PM
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Yes, It matters.
The bare copper wire is a Ground wire and may only be connected with other Ground wires anywhere except the main panel. At the main panel they may be connected on the same bar, though I usually keep them separate.

Your sub panel should have one bar where only white-insulated (neutral) wires are connected, and another bar where only bare or green-insulated (ground) wires are connected.

    Bookmark   March 1, 2010 at 3:20PM
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Thanks, guys.

Mike, I appreciate your answer, but it didn't quite do the job for me. The wires are white, black and plain copper. My question was must I connect the copper wire the ground rod. I thought maybe because there WASN'T any negative wire, I could just use the negative bar, rather than run it clear across to the other sided to the ground bar. Not a problem, just easier since I exited the box on the right side. BTW, I used to know a Mike Kaiser in Sunnyvale, Ca. Any knowledge of this man?

Randy, you are correct. All the bare (ground) wires are connected on the left side to the ground bar. In this case the two hot ones are black and white. So, I know I won't be wrong connecting the ground to the ground bar, but wondered if I could connect it to the neutral.......because of where I exited the box.

BTW, it is 220v.



    Bookmark   March 1, 2010 at 4:50PM
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In a subpanel, the ground must go to the ground bar. It will probably take you $1 for of wire and a solid 2 minutes of extra work to get it to the other side of the panel.

    Bookmark   March 1, 2010 at 5:23PM
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" The wires are white, black and plain copper."

That is 10/2 cable with ground.
The bare wire is NOT counted in defining the cable.

It IS counted in flexible cords though.

The black is hot.
The white will be the other hot to get 240 V.

Even a wrap of tape around the white at each end to mark it as a hot conductor is acceptable.

The bare wire is ground.

I usually land the ground and neutral for each circuit near the breaker in a main panel to make keeping track of what goes with what easier.

    Bookmark   March 1, 2010 at 5:26PM
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Thanks everyone.

Bill, I have plenty of wire, so no problem there. Just wanted to be certain.



    Bookmark   March 1, 2010 at 6:31PM
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Don't know anyone in Sunnyvale.

In a subpanel, neutral and grounds must be kept separate. In your case, you could connect the bare copper ground wire to the ground bar.

    Bookmark   March 1, 2010 at 10:14PM
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