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Thread: Can a 3way switch short?

  1. #1
    DIY Junior Member Tollerplumbing's Avatar
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    Default Can a 3way switch short?

    I have a 30 year old house that is for sale. The realtor told me that the lights in the bathroom didn't work. I found the circuit was shorted. After checking 4 outlets and 9 switches I found that removing the very last item, a 3way switch, fixed the problem. I replaced the switch and all is well. But then I tested the switch and it seems to work properly.

    The switch is in a very stupid place and I didn't even know it existed; I only found it because I knew there had to be 2 3way switches and hunted down the second one. I never used it and doubt the previous owner did either. Just maybe someone at an open house flicked it for the first time ever, shorting the circuit.

    So my question...
    Is it possible for a 3way switch to cause a short? I don't really see how; I can see it not working, but I don't see how it could cause a short; especially since it seems to be working properly now.

  2. #2
    Electrical Contractor/Instructor jwelectric's Avatar
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    In your statement you made the remark that you had never used it. Is it possible that it was miswired in the first place?

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    Jack of all trades DonL's Avatar
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    If a light switch don't short then the light never comes on.


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    DIY Junior Member Tollerplumbing's Avatar
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    Quote Originally Posted by jwelectric View Post
    In your statement you made the remark that you had never used it. Is it possible that it was miswired in the first place?
    I don't think so. There were just 4 wires in the box and I wired the replacement switch up exactly the same, and it worked normally then.

    The only possibility I can think of, other than a defective switch, is that the ground wire was excessively long. It might have been making contact with one of the traveler terminals, and that would be a short; but I didn't see that when I opened the box. Maybe I missed it.

  5. #5
    DIY Junior Member Tollerplumbing's Avatar
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    Quote Originally Posted by DonL View Post
    If a light switch don't short then the light never comes on.


    Be careful playing with electricity.
    A short normally refers to creating an unintended path, generally to ground. Completing an intended circuit would not be a short.

  6. #6
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by Tollerplumbing View Post
    It might have been making contact with one of the traveler terminals, and that would be a short; but I didn't see that when I opened the box. Maybe I missed it.
    This is what I was thinking the problem would have been but if this were true it would not have been a short it would have been a fault to ground called a ground fault.
    A short circuit is when you have one hot touching another hot or as Don pointed out the switch shorts the circuits causing the light to burn. Yes I know this is a play on words but being technical correct means a lot when dealing with current flow.

  7. #7
    DIY Junior Member Tollerplumbing's Avatar
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    Quote Originally Posted by jwelectric View Post
    This is what I was thinking the problem would have been but if this were true it would not have been a short it would have been a fault to ground called a ground fault.
    A short circuit is when you have one hot touching another hot or as Don pointed out the switch shorts the circuits causing the light to burn. Yes I know this is a play on words but being technical correct means a lot when dealing with current flow.
    A short to ground is when a hot contacts a ground; it is a universally recognized term.
    On the other hand the term "short" is never used to refer to an intended circuit; it is always accidental.
    I hope you guys are just having some fun, rather then really being ignorant, but I won't be coming back here either way.

  8. #8
    DIY Senior Member Homeownerinburb's Avatar
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    Quote Originally Posted by Tollerplumbing View Post
    I won't be coming back here either way.
    And diplomacy scores again.

  9. #9
    Jack of all trades DonL's Avatar
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    Quote Originally Posted by Tollerplumbing View Post
    A short to ground is when a hot contacts a ground; it is a universally recognized term.
    On the other hand the term "short" is never used to refer to an intended circuit; it is always accidental.
    I hope you guys are just having some fun, rather then really being ignorant, but I won't be coming back here either way.

    Sorry you have a attitude.

    Many light switches do not have anything to short to. If the switch shorts then the light stays on, Not off.

    Or if it has a short and it is grounded it should Blow a Fuse or Pop a breaker. If not then it is not protected properly.


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  10. #10
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by Tollerplumbing View Post
    A short to ground is when a hot contacts a ground; it is a universally recognized term.
    Anyone who works in the electrical field knows what a ground fault is and how to remedy the problem.
    250.4(A) (5) Effective Ground-Fault Current Path. Electrical equipment and wiring and other electrically conductive material likely to become energized shall be installed in a manner that creates a low-impedance circuit facilitating the operation of the overcurrent device or ground detector for high-impedance grounded systems. It shall be capable of safely carrying the maximum ground-fault current likely to be imposed on it from any point on the wiring system where a ground fault may occur to the electrical supply source. The earth shall not be considered as an effective ground-fault current path.
    Quote Originally Posted by Tollerplumbing View Post
    On the other hand the term "short" is never used to refer to an intended circuit; it is always accidental.
    All a switch does is short the open of the circuit or closes the path of the circuit so the light will emit
    Quote Originally Posted by Tollerplumbing View Post
    I hope you guys are just having some fun, rather then really being ignorant,
    I have spent more time in this field than you are old and about that many years standing at the front of a class. My wall is covered with papers from different colleges stating the amount of knowledge I have so no my friend I don’t think ignorance comes into play here with me.

    Quote Originally Posted by Tollerplumbing View Post
    but I won't be coming back here either way.
    This is a choice that only you can make

  11. #11
    DIY Senior Member bluebinky's Avatar
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    I have over 300 university/graduate credits, but none of them are in "ego management" or "diplomacy". Here's my shot at it...

    All three hot (non-bare) wires would see power during normal operation, even if the switch in question was never touched. The problem could be that the switch suddenly failed internally and shorted the hot terminal(s) to the ground lug, but that doesn't sound likely to me. Have any of you guys with lots of "field experience" ever seen that?

    To me, it sounds like wires touching somewhere that was "fixed" when things were moved around as the switch in question was replaced. Unless it can be verified with and ohmmeter reading zero between the ground terminal and at least one of the hot terminals on the "broken" switch, more investigation is needed.

    For safety (and liability), I would recommend someone licensed and insured looked at it unless the cause can be verified.

    Just for kicks, my understanding of the origin of the usage of the word "short" is sort of like landing short of a runway -- an unintentional return path physically "before" the intended load.
    Last edited by bluebinky; 09-01-2013 at 08:33 PM.

  12. #12
    Retired Defense Industry Engineer jadnashua's Avatar
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    FWIW, every switch is shorted once you turn it on...it connects one lead to another. The time when a short causes problems is when you short-circuit power to a place it is not designed to go without a load, such as directly to ground. Now, few switches can do that internally, since they normally only switch hot, or power, not neutral or ground connections, at least in residential situations.
    Jim DeBruycker
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  13. #13
    Electrical Contractor/Instructor jwelectric's Avatar
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    Gentlemen,

    Ever hear if a Ground Fault Circuit Interrupter? It is the receptacle in your bathroom or over your kitchen countertops. It is not a Short Circuit Interrupter.

    There is a big difference between a short circuit and a ground fault. A ground fault is the hot having a path to ground be it the equipment ground or through you to earth.

    A short circuit deals with hot and hot as when the switch is turned on it shorts the hot to the hot causing the light to work or it is hot to hot causing the fuse to blow.

  14. #14
    Jack of all trades DonL's Avatar
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    Really when you read the original post, it sounded like a open to me.

    If it would not light, That would be a open.

    Maybe a GFCI was tripped. And after working on it the breaker or outlet got reset somehow. Or you had a loose wire at the switch. Both are OPENs, and can cause the same symptom.

    Short Circuits Trip Breakers.


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  15. #15
    DIY Senior Member bluebinky's Avatar
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    Really bad posting here guys...

    The OP said "shorted", and that removing the switch "fixed the problem" -- most likely meaning that the breaker kept tripping. No one here has offered an answer to the question do switches "short out". I have never seen one do so (at least not to ground), but my experience is limited to perhaps a few thousand -- way less than those of you who have worked with the stuff every day for decades...

    Switches do not "short" and "unshort" during operation -- they open and close (or make and break). A normally operating switch is no more a short by itself than is a piece of wire.

    A "short" does not mean zero ohms or even necessarily close to it. In some applications, a 100 megohm resistance would be considered a short, while in others much less than an ohm for a load would not be. A short is a current path in the wrong place. We have slang terms like "leakage" and "dead short", but these need a context to have meaning.

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