Light Goes On When Breaker is turned off

billnrbostonOctober 13, 2007

This is my first time on the forum. Something just happened that worries me and I'm hoping to find some advice.

I tripped a breaker accidentally while doing some outside electircal work. On the circuit are some basement lights as well as outdoor lights. I went to the basement and found the breaker and flipped it back on. A light in the basement went out! I flipped the breaker to on...and the light went off!

With the breaker on, I went to the switch for the light and turned the switch on. Leaving the light switch on, I went back and turned the breaker off. The light went off as it should.

So this is strange. With the light switch "off," flipping the circuit breaker to "off" turns the light on. With the light switch "on" the circuit breaker works as it should.

Anybody out there have any idea what's going on?


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I went to the basement and found the breaker and flipped it back on. A light in the basement went out! I flipped the breaker to on...and the light went off!

Can you help me with that? Uh, the light went out and then it went off?

I think there's probably an innocent typo there, but this problem is likely going to require some precise info.

And it might be helpful, while you're at it, if you could add details about the electrical work you were doing at the time. Did you have any wires disconnected in a junction box when this poltergeist started shining?

    Bookmark   October 13, 2007 at 9:52PM
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my 1st thought with out further info is
you have an emergency fixture with a switched and unswitched feed. The breaker you triped is for the unswitched feed.

    Bookmark   October 13, 2007 at 10:22PM
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No typo!!!

+ Light switch off, Circuit breaker off, light is on
+ Light switch off, Circuit breaker on, light off
+ Light switch on, Circuit breaker on, light on

Here are some more observations: When the circuit breaker is off, the light is dimmer then normal. I also found another light on the same circuit with a dim light. When the switch for either light is turned on, both lights go off.

The lights are in an 85 year old home. Much of the wiring in the house is knob-and-tube. We upgraded the fuse box to circuit breakers 20 years ago.

My only guess is that the neutral wire is not neutral at all. Maybe I do need to call ghost busters!

    Bookmark   October 14, 2007 at 1:44PM
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The only time I have seen this is when one of the hot leads to the house was out. Turn off all 240 volt breakers and try it again.

    Bookmark   October 14, 2007 at 6:59PM
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Again I think it's an emergency fixture, with a battery back up, that has a switched and un-switched feed.
the reason the light is dim is because it's running on the battery at that point, (not full power)
some emergency fixtures are lit 24/7. when the power fails it runs on the battery, giving light for egress. You can't put these fixtures on a switch.
if it was on a switch, when you turn the switch off, the light would switch to battery backup. Eventually the battery would drain and the light would go off. This could take minutes or hours depending on how old the battery is.
Some emergency fixtures can be put on a switch.
The light goes on and off with the switch. and when the power fails it switches to battery back up giving light for egress
they do this by having a switched feed and an unswitched(constant) feed to the fixture
When you turn off the switch, the fixture knows its not a power failure because it still sees the power from the unswitched feed. so the light turns the off. (instead of switching to battery backup)
In the case of power failure, no matter what position the switch is in, the fixture no longer sees the unswitched feed(constant feed) and switches the light over to battery back up
This is how the fixture knows if the power was cut due to someone turning off the switch or due to power failure

However, I've only seen these fixtures in commercial applications. Not that they can't be in residential, I've just never seen it.
also I have never seen this type of fixture that wasn't florescent (so if your fixtures are not florescent then I am probably wrong)
the house is old as well. I don't know how old battery backup technology is. my gut tells me it's not 80 years old.

so it may or may not be what I've described

Open up one of the fixtures and see if the ballast has a wire marked switched feed and a wire marked unswitched feed.
if it does I could be right
if it doesn't then I'm not

good luck!!!!

    Bookmark   October 14, 2007 at 11:29PM
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I take it this circuit was behaving itself before.

Would one or both switches be 3-way?

I haven't drawn this out on paper, but trying to envision it in my head, I'm thinking you may have a form of 3-way switching that was sometimes used with knob and tube wiring - perhaps drawing hots from different circuits. One of the neutrals may have a bad or loose connection.

I think what's happening is that the first light is being connected in series with the second, using a hot from one circuit and a neutral from another. That would explain why two lights are dimmer than normal.

As I say I haven't drawn this out, so I'm not sure of the details of how this might be causing the symptoms you describe. But that's where I'd probably start looking if I had your house.

As far as fixing it ... it'll require some knowledge of basic electrical circuits. If you don't have that yourself I think you'll get really frustrated trying to troubleshoot this one. I suggest you find a good professional old-timer who's interested in a challenge.

    Bookmark   October 15, 2007 at 11:40PM
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The suggestion of davidr is really the only way this problem will be properly solved.

    Bookmark   October 16, 2007 at 6:57AM
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Wow, DavidR, I think you've got it. It is in fact on a three way. One of them is an old style twist switch that is mounted on the ceiling which is horse hair plaster. Therefore, I can be pretty certain that it is original wiring.

I suspect I have always had the problem. I'm not certain because I have not previously had a need to turn off the circuit breaker.

Thanks for your help!

    Bookmark   October 16, 2007 at 8:04AM
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Could the light be wired in parallel with the circuit breaker, as well?



    Bookmark   October 17, 2007 at 1:01PM
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Two possiblilites:

The circuit breaker is in the common neutral shared by the two lighting circuits. When the breaker is on, each circuit works normally. When the breaker is off, the two circuits are in series across the 240 line. If the two bulbs are the same wattage, I would expect them both to be the same brightness.

You have a circuit with a "california/carter" style 3-way. In this circuit, the bulb is connected between the commons on the two 3-way switches with one pole tied to neutral on each switch, and the other pole tied to a (different) hot circuit, one to each switch. The second lighting circuit is also fed by the same breaker that you are talking about. Turning off the breaker will put the two bulbs in series across 110V; same wattage bulbs will be the same dimness, a bit below half brightness.

    Bookmark   October 24, 2007 at 8:58AM
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