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Thread: Need Help with circuit issue.

  1. #1

    Default Need Help with circuit issue.

    Hi all. I started remodeling the kitchen a couple weeks back, and we took out a false ceiling so I've been moving electrical. I'm good at how to wire circuits, code, etc, but not good at troubleshooting. So...all my new stuff actually works just fine, it's an old circuit that's having issues, might just be coincidental. Anyways, I'll lay out the story best I can.

    First of all, this is how the circuit goes:
    It's a 12-3 coming from a 2-pole breaker, 2x20A, runs into a 3 gang box in the kitchen.
    Black wire (pole 2) feeds 2 switches, which feed kitchen lights and back porch light, commons from those lights tie back into the 12-3 common.
    Red wire (pole 1) feeds the top of an outlet, for the dishwasher, common tied into the 12-3 common, also feeds the bottom of that same outlet, via a switch, for the disposal, common back to the 12-3 common, and feeds a GFCI which then goes on to feed a wall outlet.

    So, the story.
    This all worked fine before. It's actually the only circuit I didn't touch yet (until the issues) but perhaps it got "jiggled"? Kind of coincidental it started happening after tearing stuff out.
    Anyways, after tearing out cabinets and some false ceiling, my wife said the dishwasher went off in the middle of a cycle. Does the disposal work? She turned it on, and it made a strange noise, like the motor was stuck or something so we turned it off right away. But hey, now the dishwasher came back to life! Well, all seemed to be working fine again.
    Roll forward a week. The kitchen lights start flickering now. I notice if I turn on the back porch light, they steady. Also, they don't always flicker when turning them on, but most of the time. Well, that next weekend I try troubleshooting it by using my trusty voltage detector wand and playing with turning those 2 breaker poles on and off, when I notice finally that when the lights are on, and the breaker (pole 2) is on, the breaker is buzzing/arching! So, I took it out, sure enough it was sort of burnt up so I replaced it.
    Problem solved? No. The breaker does not buzz again, and the lights don't flicker, but I still get the strange happenings with the dishwasher and disposal (btw I've been leaving that breaker off now unless trying to solve it). So, I figure maybe (dishwasher/disposal) outlet? Changed it out to a new one, part of the remodel anyways, no go. In fact now I notice both outlets are reading power with my wand even with the disposal switch in the off position.
    So, maybe a bad switch then? Well, I should have tried that first, but instead, I decided to label all the wires in the box and remove all the switches/outlets from the box, so I could first be sure which was the 12-3 from the breaker. This is where I now notice something that might indicate my problem (short?).
    When I turn only 1 of the 2 breakers on, I expect the one wire of the 12-3 to be hot and the other not. Well, they both read hot, even if 1 (either 1) of the poles is on. What else I notice is that the wire from the pole that is on reads hot when the wand gets within about 1 1/2 inches from the wire, as other hot wires elsewhere do, but the other from the pole that is off only read hot when I'm almost touching it. Before I put things back and try a new switch, is this normal for some power to perhaps be induced into the other wire in the 12-3 since the voltage is obviously lower in the one that is off, or does this mean the wires or breaker poles are arching between still?

    I know, long story, but I wanted to cover it all now instead of having a bunch of people asking for more details later! Thanks.

    ***EDIT***
    For my own sanity too, I drew up the circuit.
    Last edited by wesblake; 08-11-2010 at 08:19 PM.

  2. #2
    DIY Member Lightwave's Avatar
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    Sounds like the neutral ('common') is open somewhere in or before the 3-gang box. Check all neutral connections for loose hookups. Use a continuity checker or ohmmeter to check for neutral continuity back to the breaker panel.

    Leave both breakers off until you've found the problem. Loose connections and open neutral connections in split circuits are very dangerous fire hazards.

  3. #3

    Default

    Thanks, I'll try that. Question, how? I have a test light, and a multi-meter, but obviously the test leads won't stretch across the house! Thanks again.

  4. #4
    Retired Defense Industry Engineer jadnashua's Avatar
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    If there's a problem with the neutral, you might find 240vac in places you only wanted 120, or there might be low voltage between hot and neutral, but good voltage hot to ground. There should not be any voltage between neutral and ground (well, you might get a volt or two, but nothing major).
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  5. #5

    Default

    Ok, this is what I checked, and maybe things are good (my voltage detector wand just too sensitive?).
    I unhooked EVERYTHING in the 3 gang and capped it all off accept the 12-3 coming from the 2 pole breaker. I turned on 1 of the 2 circuits and used a multi-meter at the 3-gang end. Here's what I came up with:
    Red probe to pole 1 wire (ON), black probe to common = 120V
    Red probe to pole 1 wire (ON), black probe to ground = 120V
    Red probe to common, black probe to ground = 0V
    Red probe to pole 2 wire (OFF), black probe to common = ~0.5V
    Red probe to pole 2 wire (OFF), black probe to ground = ~0.5V

    So, is it just that a little power is induced into the other and the wand is sensitive enough to pick this up? Would all this mean the breaker and 12-3 from it to the box is safe? If so, I can move on to possible broken outlets, switches, etc. Thanks.

  6. #6
    Moderator & Master Plumber hj's Avatar
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    One thing you must not have done with the disposer/dishwasher outlet was remove the jumper between the two "hot" screws. Without doing that both of them are always hot, regardless of the switch position. Put everything back together again, and THEN use the multimeter. Your test probe is useless to diagnose the problem since you have to know HOW much voltage is in the wires, not that there is SOME voltage there. A bad neutral will backfeed into a "dead" circuit if there is something turned on. The GFCI 's circuitry will also backfeed if its neutral is interupted.
    Last edited by hj; 08-13-2010 at 05:42 AM.

  7. #7

    Default

    Thanks, I did indeed remove the jumper between the screws, so that's not the problem. However, I now know that the wand might have been a bad indicator, so I'm putting stuff back together one piece at a time today and testing with the multi-meter. I'll post if I get into something weird again!

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