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Old 09-18-2010, 12:01 PM   #1
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Two breakers to shut off power?


Hi - I'm in a 1960's home where the wiring is totally confusing and seemingly hazardous. I have a bathroom that has a switch on the inside wall and on the bedroom wall outside the bathroom. In order for both switches to elicit zero response from my tester, I needed to shut off two separate breakers. This took several iterations to figure out, because only one of the breakers turned off the light itself (and because the box is not marked at all). When that breaker was off, I still had a response from the switch outside the bathroom - as well as the switch for the closet next to it.

Three questions: 1) What could explain the need to tie in between two circuits? 2) Did the code allow this in the 1960's, and does it allow it today? 3) Do I need to chase this down and re-wire the circuit? (note: My checkbook would do the work - I would definitely call a professional).

Thanks!

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Old 09-18-2010, 12:41 PM   #2
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Two breakers to shut off power?


Interesting, sounds like two hots from two seperate breakers somehow enter that same circuit. This could be tricky to find. You'd need to access all the jboxes of that circuit and try to trace each wire. One of them is wire nutted where it should not be. I'm thinking a jbox somewhere is used for two circuits, and while changing a fixture two hots were put together by error. Just my guess though. Could be lot of things.

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Old 09-18-2010, 01:17 PM   #3
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Two breakers to shut off power?


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Interesting, sounds like two hots from two seperate breakers somehow enter that same circuit. This could be tricky to find. You'd need to access all the jboxes of that circuit and try to trace each wire. One of them is wire nutted where it should not be. I'm thinking a jbox somewhere is used for two circuits, and while changing a fixture two hots were put together by error. Just my guess though. Could be lot of things.

Thanks! I'm not sure how I'd get to each jbox without making a huge mess though. What hazards, if any, exist as a result of this? Also, I am getting ready to replace the Federal Pacific panel that "protects" my house and in preparing for that I was hoping to trace out my circuits. Now I'm wondering if i shouldn't worry about having to review the entire electrical plan for the whole house before I can replace this breaker panel.

Last edited by brex; 09-18-2010 at 01:18 PM. Reason: spelling & clarification
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Old 09-18-2010, 01:32 PM   #4
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Two breakers to shut off power?


what kind of meter are you using?
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Old 09-18-2010, 01:40 PM   #5
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Two breakers to shut off power?


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what kind of meter are you using?
50-1000V AC voltage detector
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Old 09-18-2010, 02:45 PM   #6
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Two breakers to shut off power?


Hot lines from two or more circuits may enter the same box but neither the hot conductors nor the neutral conductors may be tied together there. (Grounds are all tied together wherever they come together.)

You could be reading phantom voltage. Do you need to turn off both breakers to make the light go off? What was the actual voltage (to the nearest five volts) yoiu measured?
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Old 09-18-2010, 03:18 PM   #7
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Two breakers to shut off power?


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Hot lines from two or more circuits may enter the same box but neither the hot conductors nor the neutral conductors may be tied together there. (Grounds are all tied together wherever they come together.)

You could be reading phantom voltage. Do you need to turn off both breakers to make the light go off? What was the actual voltage (to the nearest five volts) yoiu measured?
Thanks Allan! I am using a simple detector - on/off only, not a meter. To turn off the light, I only need to shut off breaker A, and furthermore the light does not turn off if I only shut off breaker B.

Where I am really disturbed is at the closet light. When no breakers are shut off, and the light is off, the voltage detector does not detect any voltage present. However, once the light switch is turned on, the light goes on, and the detector lights up. When I switch off breaker B, the voltage detector lights up regardless of whether the light switch is on or off.

I have read a little about reverse polarity, but that does not seem to be the case here. Any thoughts?
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Old 09-18-2010, 03:25 PM   #8
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Two breakers to shut off power?


I'm thinking you should probably find a multimeter to test the actual voltage with. You may be picking up induced voltage, from the wires running near wires from another circuit. Those voltage detectors can be a little over-sensitive sometimes.
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Old 09-18-2010, 04:15 PM   #9
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Two breakers to shut off power?


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50-1000V AC voltage detector
Is the neutral shared between those two circuits? You might be getting some stray voltage.
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Old 09-18-2010, 06:18 PM   #10
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Two breakers to shut off power?


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Is the neutral shared between those two circuits? You might be getting some stray voltage.
That's what I was originally thinking. It is had to say.

The UPDATE to this craziness: I just replaced a simple outlet on an opposite wall. No other wiring anywhere close to that outlet, no three-way switches, etc. The same thing occurs - I needed to shut off both breakers in order to keep my voltage detector from going off.

I'm convinced that there really are two circuits tied together in a j-box somewhere, just too hard to tell how, or where.
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Old 09-18-2010, 06:40 PM   #11
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Two breakers to shut off power?


One of the problems with a non-contact detector is the chance of false positives. You are probably reading the voltage on a nearby cable. A analog meter like a Wiggy could confirm this.
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Old 09-18-2010, 07:19 PM   #12
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Two breakers to shut off power?


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'm convinced that there really are two circuits tied together in a j-box somewhere, just too hard to tell how, or where.
Now if you plugged something into that receptacle and turned it on, then you will find out whether hot wires are crossed somewhere when you turn of one breaker and then the other.
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Old 09-19-2010, 08:51 AM   #13
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Two breakers to shut off power?


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That's what I was originally thinking. It is had to say.

The UPDATE to this craziness: I just replaced a simple outlet on an opposite wall. No other wiring anywhere close to that outlet, no three-way switches, etc. The same thing occurs - I needed to shut off both breakers in order to keep my voltage detector from going off.

I'm convinced that there really are two circuits tied together in a j-box somewhere, just too hard to tell how, or where.
I'm sensing all the feedback is overwhelming you..... if you are truly convinced that the 2 circuits are tied together, you really should call in a professional.
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Old 09-19-2010, 09:15 AM   #14
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Two breakers to shut off power?


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I'm sensing all the feedback is overwhelming you..... if you are truly convinced that the 2 circuits are tied together, you really should call in a professional.
Not overwhelmed. I enjoy the troubleshooting aspect quite a bit. I would probably get someone else to do the physical work though. Thanks for everyone's feedback!
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Old 09-19-2010, 10:27 AM   #15
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Two breakers to shut off power?


I think he needs to replace the non contact tester with a meter or wiggly.
Circuits do not have to be crossed , just run in close proximity for the tester to show voltage.
I'm sure that after 50 years, this problem whould have shown up before nopw!

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