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I am replacing a 20A 250V receptacle with a NEMA 5-20 and am seeing voltages I can't explain.

  • Hot-ground: 122v
  • Neutral-ground: 20v
  • Hot-neutral: 95v

What could be the problem here?

Details

  1. Turned off main
  2. Removed 2 pole circuit breaker
  3. Capped red wire
  4. Installed 1 pole breaker and connected black wire
  5. Turned on main
  6. Remove old receptacle, discover there are only 3 wires - white, black, ground (this receptacle is labeled 20A 250V)
  7. Installed NEMA 5-20 receptacle - black to brass, white to silver, ground to green as per instructions.
  8. Read above voltages

Where did my red wire go?

I am certain I replaced the correct breaker. No voltage when I turn the breaker off.

The wire appears to be 12 gauge.

My outlet tester is inconclusive because all three lights appear to be lit.

  • How many poles are on the existing breaker? – ThreePhaseEel Aug 14 '18 at 2:48
  • Removed breaker had 2 poles. Installed breaker has 1 pole. – Dean Brundage Aug 14 '18 at 3:09
  • What happens to the white wire at the breaker panel end? – ThreePhaseEel Aug 14 '18 at 11:39
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So in the breaker box, you have black, red and ground but in the outlet box you have black, white and ground.

Odds are that you have a junction box somewhere where the red wire is connected to the white wire. Since you capped the red wire in the breaker box, the white wire is not connected, just floating.

I’m also assuming you checked the voltages with a digital voltmeter. In this case, you’re seeing a phantom voltage, induced from other wires. The voltmeter provides very little load.

To test this, plug an outlet tester into the outlet, it should show “open neutral”. You can also measure the voltage with the tester plugged in. You should now see 120 volts (or nearly that) on the white, conducted through the tester.

Assuming all of that proves true, you need to land the red wire onto the neutral bus in the breaker box. I’d also suggest marking the end of the red wire as white, either with paint or tape.

  • I'll give that a try. When I plug an outlet tester in all three lights are on, which means nothing. 20v across the neutral-ground is pretty high. Could that be a phantom load? – Dean Brundage Aug 14 '18 at 14:09
  • Also, I think my neutral bus is full. Can I land the red wire onto the neutral bus somehow, or can I install a longer bus? – Dean Brundage Aug 14 '18 at 14:11
  • I’m concerned that you are getting three lights on your tester. I wouldn’t think the phantom voltage would light it. I’d still try connecting the red to neutral. – DoxyLover Aug 15 '18 at 20:57
  • You can try connecting the red to the ground bus as a test only. Don’t leave it there! It’s against code and potentially dangerous. If this solves the problem, you do need to move it to the neutral bus. You could add a second one and connect them together. Be sure to remove the grounding screw on the new one. – DoxyLover Aug 15 '18 at 21:01

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