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I have equipment that has 3 wires (red, black, green)

The wire run from the breaker box is 10-3 (red, black, green, white)

The equipment requires 220/240v. I'm just wondering if it's OK to leave the white wire capped off at the outlet?

Basically I have a red & black hot tied to the red and black (respectively) and ground to ground. The white (which is tied to the ground in the circuit breaker box) is just capped off by itself at the equipment.

Is this good, or should I cut the white off in the breaker box which would essentially make my 10-3 run of wire a 10-2?

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  • Do NOT cut it short - leave the full length stuffed in the back of the box! Someone, at some time will need that (quite possibly future-you) and curse you for having cut it off!!
    – FreeMan
    May 24, 2021 at 15:32

2 Answers 2

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Go ahead and cap the unused white (neutral) wire off

Your plan to cap the unused white wire off is fine, and for the best even, as it'll leave it available in case someone else wishes to run a 4-wire appliance off this circuit in the future.

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You are fine with just capping off the white wire in the outlet box. Usually people here have the opposite problem: Needing a 4 wire feed and only have 3, you have a good problem! Which isn't exactly a problem. If you want to be double/triple sure, remove the cover of your main panel and see where those wires land. Probably both the neutral and ground will land on a neutral bus bar.

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  • Thanks. The ground and neutral in the panel are tied together. I believe the both go to the neutral bar from there.
    – WP.
    May 23, 2021 at 4:30
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    That's not quite "best practice" both the ground and neutral should be landed individually on the neutral / ground bar. Not critical, but certainly not best practice. May 23, 2021 at 4:39
  • Ground should go to a grounding bar and neutral to a neutral bar. Don't want neutral current (remember that there are other circuits!) flowing in the (typically smaller) ground wire, or an open neutral connection upstream resulting in an energized ground. May 23, 2021 at 19:09
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    @TylerH OK, I'm going on, but the other reason is if in the future somebody needs to turn a main panel into a sub-panel, like after a whole house generator transfer switch, it's far easier to do if the grounds and neutrals are on separate bus bars. May 24, 2021 at 22:19
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    @TylerH Yeah, the terminology gets complex! It took me a while to get my head around the difference between "grounded neutral conductor" and "equipment grounding conductor". The first is expected to carry some current, the second is not but is there in case of a ground fault. May 25, 2021 at 15:31

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