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I have a 1948 house that has mid-century conduit throughout. All old two-prong outlets in the old house; only the 1980s extension has your typical 14/2-G.

Anyway, in the old house (as the title says) my finder is locating two circuit breakers associated with a single outlet.

I haven’t looked closely at this yet but strongly suspect that the last homeowner replaced a two-circuit outlet (where one was controlled by a nearby switch) with a single circuit outlet. There is an extra switch in my living room - doesn’t appear to do anything - so this seems about right. If its load is also on the outlet then its return will be affected too.

So could the outlet be going back to the panel across two different circuits? Not sure there’s a way to test this without taking out the outlet and testing everything in there w/ a multimeter in tandem w/ the light and breakers.

Any thoughts? Could it be something else?

  • When you say "mid-century conduit" are you talking about actual conduit (rigid/flex) or are you talking about BX instead? – ThreePhaseEel Aug 25 '18 at 1:48
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    Also, how many breakers do you have to turn off to get the outlet to stop providing power? – ThreePhaseEel Aug 25 '18 at 1:49
  • Does the switch that doesn't do anything have wires connected to it? If so, the other ends of these wires would terminate in the original receptacle box. Look for a receptacle box with two capped off wires. Of course, the hacker might have cut them off close. – Jim Stewart Aug 25 '18 at 1:49
  • @ThreePhaseEel good questions. It’s BX with no grounding strip. Just moved in here and still figuring the place out. One breaker controls the power to the outlet. The other breaker has no effect but the finder shows a link. Switch doesn’t seem to do anything in either case, but it could be a broken switch they never replaced, and the return/neutral is functioning fine back to the panel. – Pat M. Aug 25 '18 at 2:07
  • @JimStewart That’s definitely something to look for. I have not opened up the outlets yet, just been trying to map the unmapped breaker panel in my new/old house before I get to work. I did plan to do some outlet replacements (thinking I will convert to three-prong GFCI grounded to the box because I don’t really trust grounding to the box alone). – Pat M. Aug 25 '18 at 2:13
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The Klein circuit breaker finder is just a re-branded High-Tech, the Harbor Freight brand for about triple the price.

https://toolguyd.com/klein-breaker-finder-and-hi-tech-circuit-detective-identical/

Klein-vs-HF-Circuit-Breaker-Detectors

So don't expect much. But even with a good one, a breaker finder should never be treated as more than a guess to narrow down further testing and verification.

If the breaker finder indicates two circuits, it's possible the wiring is crossed up somewhere and both breakers energize this receptacle. That's not uncommon if someone makes a mistake connecting blacks to blacks somewhere. However it's even more common for the breaker finder to make a mistake.

If you turn off the breaker and test the receptacle for voltage, and find no voltage present, then you have demonstrated that that breaker and only that breaker provides power to that receptacle. However: In a case like this where you're concerned something's wrong, I'd not trust a non-contact voltage tester or a plug in receptacle tester to verify there's no voltage present; I'd want to test with a good voltage tester or meter.

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    I do agree that even an $800.00 circuit tracer may show more than one breaker occasionally, then the simple thing to do is turn them off one at a time. Only powered by 1 breaker don't waste any more time or worry it is fine. – Ed Beal Aug 25 '18 at 17:31
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It's possible he had a multi-wire branch circuit and the light switch was on the other leg. Since MWBCs must be on opposite legs to not overload neutral.

When he changed the receptacle without breaking off the tab, he promptly tripped a breaker.

Then he discovered if he moves the breakers around enough, they stop tripping. He ended with both breakers on the same pole. Which of course is overloading neutral.

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