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Thread: Faulty breaker?

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  1. #1
    DIY Junior Member julesy's Avatar
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    Dec 2010

    Default Faulty breaker?


    I have a main panel (unfortunately without a main breaker) and a sub panel. The sub panel is fed from the main panel via a dual pole breaker. One red and one black connection with some pretty hefty looking wire.

    When I turn off the dual pole breaker (dual switch connected), the black wire to the panel is no longer hot, but the red remains hot. I see no reason why this would or should happen, except that the breaker has failed. Can anyone concur that breakers do fail in this way?

    Thanks in advance.

  2. #2


    Well, anything is possible, but I've never seen a breaker fail that way (and I've seen more than my share of bad breakers). More likely you are using a cheap DVM to determine if there is voltage present or not. They are notorious for returning bad readings when no voltage is present. You need a 120/240 volt circuit tester such as http://www.drillspot.com/products/73...Voltage_Tester or a analog multimeter if you can find one.

    Also, your main disconnect is probably at your meter.

    Last edited by drick; 03-19-2011 at 10:55 PM.

  3. #3
    In the Trades SacCity's Avatar
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    Mar 2011
    Sacramento, CA


    It is possible for the contact to have welded shut, but does not happen frequently, be careful when working on the system.
    Another possibility is a bad neutral on another circuit, which could feed back through that circuit.
    Last edited by Terry; 04-06-2011 at 09:27 PM.

  4. #4
    Plumber jimbo's Avatar
    Join Date
    Aug 2004
    San Diego


    Residential breakers typically have a 10,000 amp interrupt rating. I suspect "welding" of contacts is rare.

    Are you measuring 240 between red and black with it off? How are you measuring the red wire?

    There is probably something else going on. Needs some detective work.

  5. #5
    DIYer, not in the trades LLigetfa's Avatar
    Join Date
    Feb 2011
    NW Ontario, Canada


    A double pole breaker breaks both legs so you should not be seeing voltage on either side. I have to wonder how you are testing. If using one of those contactless testers, they are notorious for giving false positive results. Athough I've never seen them give a false negative,

    Last line deleted as it is very unsafe
    Last edited by jwelectric; 03-20-2011 at 08:49 AM. Reason: safety

  6. #6
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Cave Creek, Arizona


    IF the breaker was going bad the contact could have overheated, or arced, and welded the switch together. You also have to consider whether there is any chance that you could have a cross connection somewhere that could be "backfeeding" the power into that part of the system.

  7. #7


    This is a condition normally asociated with FP breakers a replacement breaker is the fix.

  8. #8
    General Engineering Contractor ballvalve's Avatar
    Join Date
    Dec 2009
    northfork, california


    I just tested my main 3 phase breaker at the pole and it Doesnt work at all. Will not shut off. Stuff gets old and tired.

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