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OT - Sudden, Mysterious Loss of Electric Circuit.

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  • OT - Sudden, Mysterious Loss of Electric Circuit.

    A 15amp circut to the overhead lights in a couple of my closets just suddenly lost power yesterday..
    The lights worked in both closets early in the day, but a few hours later did not. Naturally I thought a bulb had just burned out, but that was not the case.

    There was absolutely nothing that took place that would explain any disruption in the circuit, e.g. a carpentry or improvement project, nor was the circuit breaker tripped. I flipped the circuit breaker on/off a couple of times, to no avail. I also exposed the connections at the switches and fixtures for visual inspection, and all appeared to be in good order.

    So..., the only two conclusions I can reach are: (a) something (rat, mouse, oppossum, badger, etc.) severed a wire; or (b) the circuit breaker itself just spontaneously failed. likely is that?

    Am I missing, or overlooking anything?

    How do you pull out a circuit breaker? I've popped them in before, but never took one out, and can't remember just how they're configured, or which end to pry out. This is a Siemens box and breakers

  • #2
    If it only happened to a couple of circuits I would not think it is the breaker as others would be affected?
    But the best way is a methodical testing using a meter, first see if you have a live conductor at the switches, you should have a ground to test to.
    Also the output of the breaker could be tested same way if you feel you need to.
    Then drop the light fixture and if you do have a live at the switch, check from switch live to the light neutral, if this is OK then check continuity (with breaker off) of the switch wire from switch to light fixture.
    The secret is the methodical testing, rather than going off in all directions.
    If two circuits are affected then it points to a common live or neutral open circuit.


    • #3
      Check and see if you have voltage after the breaker when it is in the ON position - e.g. stick your probe on the screw that is holding the wire in the breaker terminal and stick the other probe on the neutral bus. If there is no voltage, then you have a bad breaker. That doesn't happen often, but it does happen - especially if it is an old installation. Usually when they fail, they fail safe and the "breaking action" feels "squishy" like it won't latch or snap to the fully ON position. Breakers come out just like they go in; rock it away from the cluster of breakers and pull it out. The pivot is on the "outside" and the clip/contact is on the "inside".

      If the breaker is not the problem, then you have some sleuthing to do. You'll have to determine approximately where in the circuit you lost power before making any decisions about how to proceed.

      All the normal precautions should be taken, e.g. make sure you have the main breaker in the OFF position etc. It's, of course, possible to replace breakers hot and not kill one's self, but it's not a good practice, particularly if you are unsure how the breaker is removed.

      :Edit: I like to start at the source and work forward in a situation like this. It helps me simultaneously trouble shoot and "map" the circuit. Once I have the circuit mapped, I take notes/draw a picture and tape it to or near the breaker box. I just purchased a home a couple of months ago and I've been updating the electrical and a big challenge is just sorting through the mess of Romex and figuring out what everything controls. If you already have a clear map of the circuit in question, then start at the problem and work backwards from there.
      Last edited by Fasttrack; 11-06-2012, 01:19 PM.


      • #4
        First off, there's only one circuit that's dead.
        Secondly, I've already determined (with a meter) that there's no voltage at the switches (one is a wall switch, the other is a pull string switch). Also, for the wall switch, I checked the continuity with the switch both open and closed, and it checks out correct, so I'm confident the switch is not defective.

        There are three items not getting power: two overhead closet lights, and one bathroom vent. So i think it's safe to say that the problem is somewhere 'upstream'.

        The circuit breaker involved does not feel squishy or mushy. It operates with a crisp "snap" when flipped either way.

        The breaker box is recessed into the wall, so I have no access other than by removing the panel cover, which I haven't done yet, but will in a while.

        This house is about 20 years old; we bought it new, and this is the first electrical issue we've had.


        • #5
          Hmm ... well, I would definitely start at the breaker because it's the next easiest place to check. If it's good, then I'd say it's time to get up in the attic!

          What kind of house do you have? Do you have Romex or THHN in conduit? Is it run from above or below (presumably from above). Assuming it's like my house with an unfinished attic and Romex from above:

          Have a helper shut off the breaker and crawl up into the attic. If you haven't been up there yet, bring a good flashlight, some planking, long sleeved shirt/pants/gloves and dust mask to protect yourself from the insulation. Crawl over to the approximate location of the breaker box and look for a bunch of Romex coming up. You should be able to extrapolate one of these leads to the bathroom fan (also presumably located in the attic). Once you are reasonably sure you've found the correct line, pop a cover off of the junction box closest to the breaker box and have your helper flip the breaker on. Test with voltmeter. Work your way along the line visually inspecting it and testing junctions. You may have to pop some wire nuts off; the helper isn't really necessary, but it will make things much easier and safer. This is really unpleasant work, by the way. It's typically hot, dusty, cramped and itchy. The Romex is usually buried in insulation and it's dark so it's tough to find and trace. Plus you have to constantly worry about falling through the ceiling.

          Again, all the necessary safety precautions should be taken. Crawling around in an attic messing with electricity isn't something that everyone is comfortable with (and there's probably a fair number who are comfortable with it but still shouldn't be doing it!)
          Last edited by Fasttrack; 11-06-2012, 03:10 PM.


          • #6
            OK. I took the panel cover off the breaker box, and with a meter did get about 123 volts between the breaker terminal and neutral buss bar when the breaker is on, and zero volts when the breaker is off. So, I'm eliminating the breaker as the problem.

            Next question: I've determined that several wall outlets are also dead. Are they wired such that if a wire connection to one of those happened to vibrate loose, it would kill the power to everything else downstream from there? i.e. are they wired in series? Or are they parallel drops from the circuit?

            Fortunately Fasttrack, it's a pretty cool day here, so the attic temperature will not be unpleasant. Nevertheless, I don't really relish being up there prowling around. But I'm no stranger up there, so if need be that's what I'll have to do.

            This is all romex. I did wire some additional circuits in my garage, aka "shop", some years ago, and used THNN in metallic conduit for those circuits. But the house wiring is all romex.


            • #7
              Check for a GFCI in the bathroom that has tripped. The GFCI is wired such that it acts like a circuit breaker for all the wiring downstream of it.

              Most wiring is not in in series, but does use the outlet boxes to daisy chain the circuit from point to point. The light switch is in series with the lamp, but you may find a second romex in the switch box that feeds the next outlet on the chain.

              I always use the end-end-halfway trouble shooting technique. Check each end to find the fault, then halfway between the last known good spot and the end, then 1/2 way between those two points and so on. You will find the bad spot fairly quick that way.

              At the end of the project, there is a profound difference between spare parts and extra parts.


              • #8
                Do any of the wall outlets have ground fault protectors on them? It is possible one of these was inadvertantly tripped. They sometimes do control a circuit depending on how they are wired.
                Jim H.


                • #9
                  No, I had looked for a GFI outlet in the bathrooms. There are none. There is a GFI outlet down by the kitchen sink. I tripped and then reset it. The only other GFI or GFCI outlets I know of is one outside on the deck and one in the garage where I have an old refrigerator plugged in, but it's still operating.


                  • #10
                    Good thoughts on the GFCI! Lynnl, the outlets are wired "in series" but the loads are in parallel. If you look at a typical outlet, you will see it has two straps, each with two screws. One screw corresponds to the hot leg "in" and the other corresponds to the hot leg "out", so if one of those gets disconnected, everything down stream will die.

                    Since there is a bathroom fan on the circuit, there is a pretty good chance there is a GFCI tripped somewhere since it's only a 20 year old house. In fact, the GFCI may have just gone bad and opened up. In my house (built in 1960) everything was 2 wire with no ground. Luckily, electrical code allows the use of GFCIs in place of safety ground, so I find the first outlet in the "daisy chain" and replace it with the GFCI. Now all the outlets (or lights or fans or etc) down stream have GFCI protection.

                    :Edit: I see you already checked for outlet GFCIs, but I should point out that they don't need to be an integral part of an outlet. They can be stand alone devices or built into circuit breakers at the panel. There is still a chance that there is an internal GFCI in the fan - although that may be unlikely. I don't have any experience with bathroom fans...


                    • #11
                      Well problem solved! ...or at least isolated. WHOOOPIE!

                      I had not previously pulled out that switch to the bathroom vent/fan. When I did, and put the meter on it, I was elated to find it had voltage. So I switched it on and voila! ...the fan started! Looked into the closet, and lo and behold the previously non-operative ceiling light was now glowing as pretty as you please.

                      Ahh! Life is good once more.

                      So now, I don't know if there's just a loose connection in (or to) that switch, or what. That box seems to contain more than its fair share of connections. I didn't pull out any other than the two hot wires attached to the switch itself. But I now know that somewhere in that box lies the problem. Will now pursue further.
                      I'm pleased to report, I've generated no smoke or sparks, least up to this point.


                      • #12
                        If you have aluminum wiring, this is a good time to make sure the wire nuts are tight and any coper to aluminum connections coated with "no-ox" or similar stuff.

                        At the end of the project, there is a profound difference between spare parts and extra parts.


                        • #13
                          That was my thought also, Aluminum and copper wire connected together.

                          Agree with danlib, i'd check that thoroughly.


                          • #14
                            This is all copper wiring. Thank goodness!


                            • #15
                              Had the same problem last year. Called a electrician. He found out I lost the neutral in a plug socket. He told me that all of the sockets he took apart and their were a bunch ,that the wires were just pushed in the little grippers and that it is a lot better to hook the wires around the terminal screws and tighten. So for the next few weeks I went around room to room and pulled all the sockets and connected the wires to the screws in stead of how they were hooked up 40 years ago when the house was built . they had just stuck the wires in the back of all the wall sockets in to the little grippers. Which is not a good way to do it over time.
                              Every Mans Work Is A Portrait of Him Self