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I have split circuit outlets: the red hot wire goes to the outlets on the left, and the black hot wire goes to outlets on the right. The red/black probably-hot wires are controlled by different circuit breakers in the panel. Both outlets share the same white neutral wire, and ground wire.

1) If I turn both circuit breakers off, I measure 0V from both outlets.

2) When I turn on one of them, I get 117V from outlet and 24V from the other (and 65V between the 2 hot wires.)

Is 24V normal? Should I expect 0V, when one of the circuit breakers is off?

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  • That looks.... Dangerous. Are those burn marks on the white plastic? Is the ground not really connected? – Jim Garrison May 27 '16 at 21:30
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    What does "prob hot wires" mean? The wiring looks correct in terms of layout, but that doubled neutral screw is crap. Why would anyone do that with two screws and (presumably) two insert connectors available? Sheesh. – isherwood May 27 '16 at 22:06
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    I suspect you're measuring floating voltage. Plug a turned on lamp (regular incandescent bulb, no led or cf) into each outlet, then turn off the breaker to one and measure with both lamps still plugged in. Also when sharing a neutral like that you should be using a double pole breaker in the panel. – Tyson May 27 '16 at 23:17
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    Since nobody else mentioned it, I will do it. Fix that shitty ground on that outlet. – Kris May 28 '16 at 2:30
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Anytime a dead wire runs parallel to a hot one, it will pick up phantom voltage. You can see it with a rather sensitive voltmeter like a modern DVM, but it won't do any useful work. In other words this is an issue with your voltmeter. Stick a dollar-store nightlight in each outlet and that will eliminate the phantoms.

The bigger problem is this shared neutral. Neutrals do not have circuit breakers. Two hots on the same neutral can overload the neutral, and I notice some scorch marks and heat damage on that neutral wire.

The only way "sharing a neutral" can work is a special arrangement called a multi-wire branch circuit (MWBC). Each hot is on a different "leg" of 240V, and the neutral only carries the difference in currents. Becuase of numerous mishaps relating to shared neutrals, Code now requires you install MWBCs in a way that guarantees they are wired to opposite poles. Such as using either a 2-pole 240V breaker or two adjacent breakers with listed, approved handle ties. I can tell you are not to modern Code on that, because you can turn each side off individually.

The most common mistake with MWBCs is using duplex/tandem breakers, or half-width breaker arrangements which put both breakers on the same pole. This guarantees a neutral overload situation.

  • +1 Good...not too overdrawn and not too short. Just right :-) – Kris May 28 '16 at 2:28
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Sounds like you have a Multi-wire Branch Circuit, so the breaker handles should be tied together, or a double pole breaker should be used. And each breaker should be on an opposite leg of the service, to avoid overloading the neutral.

If only one breaker is on, then the other hot is floating. Which means a digital multimeter could measure anywhere from 0 to 120.

Also, it looks like maybe the neutral screw terminals are loose and charred.

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