No voltage from breaker even though breaker is good

Discussion in 'General Electronics Chat' started by bradsmith74, Jun 21, 2015.

  1. bradsmith74

    Thread Starter New Member

    Jun 21, 2015
    3
    1
    I’ve searched the forums quite a bit and can’t find any other question like this one. I recently moved into a new house and needed to remove a light fixture from a wall in a bathroom. So I needed to turn off the breaker to the fixture, but the previous owners didn’t mark any of the breakers in the panel or sub-panel (which is right next to the main panel). I didn’t have a circuit breaker finder tool, so I had to resort to turning off (and back on) each breaker sequentially while someone waited at the light and told me when it went off. After going through almost all of the breakers, I eventually found the right one and turned it off. This turned off that fixture as well as a number of other lights in the bathroom. Then I removed the fixture, capped the wire, put it in the wall, and turned the breaker back on. All of the other lights that had been turned off (because of the off circuit) all came back on as expected. Everything seemed normal until I noticed that the lights and plugs in two other rooms in a different part of the house didn’t work. Note that the other lights on the circuit with the light I removed were all working, so I know the non-working lights/plugs are on a different circuit. I suspected that one (or more) of the other breakers that I had turned off and on must not have switched completely back on (I didn’t know which one, since they aren’t labeled). So I went through all of them and made sure they were all in the on position (they were). But still the other lights/plugs didn’t work. So I went through all of them again and turned them off and back on, but still no luck.

    Next I thought it might be possible that a GFCI had tripped (or gone bad), although it would be strange to have two entire rooms wired after a GFCI. But despite extensive searching I couldn’t find any GFCIs that weren’t working. It’s possible that there is a GFCI hiding somewhere I haven’t found, but I don’t think that’s the problem.

    At this point I suspected that one of my breakers had gone bad (triggered by my initially switching it off and back on). So I took off the covers to my panel and sub panel and used my multimeter to check the voltage between each breaker and the neutral. I went though all 48 breakers and found two 15A breakers in the sub-panel that weren’t showing any voltage (the others were all 120V as expected). So I thought that those two must have both died, so I went to the store and bout two new ones and replaced the bad ones. But still no voltage coming from those breakers, and no lights/plugs. I did a continuity check on the “bad” breakers that I had taken out and found that they were actually both still good.

    So that’s the situation I’m in. Also, in the course of doing this diagnosis I bought a circuit breaker finder tool and was able to label just about all of the other breakers, however I can’t use the tool on the dead plugs/lights since the tool requires the circuit to be energized. None the less I’m pretty confident the breakers for the dead lights/plugs are the two that I’ve identified as not having any voltage. My question is, what can cause a breaker to show no voltage between the breaker and the neutral, assuming the breaker is good and properly installed? Is there something in the house wiring that can cause this? Is there other testing that I can do to diagnosis where the problem is? Thanks in advance for any help.
     
  2. ScottWang

    Moderator

    Aug 23, 2012
    4,855
    767
    I think you need to take some clear pictures and draw the block diagram, and label the in out, the members may easy to give some suggestions.
     
  3. #12

    Expert

    Nov 30, 2010
    16,304
    6,814
    I think the problem is inside the circuit breaker box. A photo of the pins that the circuit breaker plugs into might reveal the problem.
    Yes, it is normal to find a weak breaker when you flip them all off and back on. If you had not measured for voltage, I would be sending you to do that.
     
  4. bradsmith74

    Thread Starter New Member

    Jun 21, 2015
    3
    1
    Thanks guys. When the sun comes up around here I'll turn off the main, pop out the problem breakers (and the surrounding ones) and take some pictures.
     
  5. bradsmith74

    Thread Starter New Member

    Jun 21, 2015
    3
    1
    Sorry for the slow response, but when in the process of taking out the breakers to take the pics I figured out what was going on and it took me a few days to confirm it. The two bad breakers were in the same row of my sub panel, and it dawned on me that if one the lines from the main panel that feeds sub panel was bad, that could be causing my problem. So I tested the two breakers (tandem) in the main panel that were feeding my sub and sure enough one of them was putting out 25V. So I replaced the tandem breaker in the main panel and now everything is working agin.

    Thank for your suggestion to pull out the breakers, which got me thinking about the problem in a different way.
     
    #12 likes this.
  6. #12

    Expert

    Nov 30, 2010
    16,304
    6,814
    'snot the first time...but then, that's why you asked us. :p
    Once upon a time, I saw a circuit breaker box wherein the fins that go up the backside of the circuit breakers had completely melted.:eek:
    The only way to find that is to pull the breakers out!
     
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