Dang, it works...sort of

Discussion in 'Shop Talk' started by Jena, Feb 9, 2005.

  1. Jena

    Jena Well-Known Member

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    I tested one circuit in my wiring project today. I was amazed that it did what I wanted it too for the most part. There are 3 outlets on the circuit. The middle one is controlled by a switch while the two on the ends remain hot all the time. When I test my middle outlet with the switch off, it shows 30 volts. When I turn on the switch it shows 120v as it should.

    This means that the black wire (which carries power to the end outlets, bypassing the switch) is "leaking" onto the red wire (which brings power from the switch to the middle outlet, bypassing the one of the end), right?

    So what do I do? Go back and look in all the boxes to check for nicked wires, bad connections, etc? Any tricks for narrowing it down?

    I'm still excited that it worked. I was afraid it would just do nothing or start a fire a something :)

    Jena
     
  2. agmantoo

    agmantoo agmantoo Supporter

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    Jena, are you using a digital volt ohm meter? Sometimes those meters are just too sensitive for simple tasks. The meter could be measuring some induced voltage from the wire running parallel to the other hot wire. Make yourself a test light using a lamp, plug said lamp into the one with the 30 volts and see if the lamp will glow. I doubt that it will. Turn the power on and then observe the lamp, all should now be OK. Probably everything is just fine as you have it wired. This is the subject that the "heated discussion" centered around in your original post. :)
     

  3. Rowdy

    Rowdy Well-Known Member

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    Well, it could be a couple of things, depending on how it is wired.

    1. I have seen cheap and/or used switches actually leak like that. You can kill the power, remove the switch, use a continuity test on both sides with the switch in the off postion to test.

    2. In the other post you mentioned wanting metal boxes. If you did use them, and if you were not careful in putting in the switch into the box, and if it was not grounded properly, it is possible the power is coming through the box. Make sure there are no bare wires in the box, make sure both the switch and the box is grounded, and wrap a bit of tape around the switch, covering the screws. If your switch has the plug ins in the back for the wires, do not use them, they are cheap, prone to slip and break.

    3. You might have a tight staple somewhere that has nicked the wire, causing the white (neutral) to carry a little current. Again, this will be more likely with improper grounding.
     
  4. Cosmic

    Cosmic Well-Known Member

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    Well you have gotten some excellent advice there. Always difficult to check from afar. Good techs are the product of their training and experiences.

    I do have something that is super for such situations. A little meter that clips in your pocket, requires no batteries and steals its power from the circuit under test. Duh, will even "Read" leakages and insulation failures, according to your skills. Shows it all on a little digital display.

    The prior advice focuses on the potential for your problem. Your meter is faulty, your method is faulty or you have an actual problem.

    It really is what is known as a "Megger Problem". Basically a test instrument that is a sort of little hand cranked generator and displays the resistance to ground of various points in a circuit. Is really how one isolates and identifies the actual source of such problems. Always done with the actual circuits de-energized under test. Anything else is guessing. Can be switches, components, wires, who knows. Typical tech troubleshooting type problem. Is how a tech "Rings Out" your type problem. I have been there, done it many times, never know the answer in advance.

    The little gizmo I mentioned before allows a very good tech to attempt to guessimate the problem without a Megger. If you want I will send you one as a freebie. I am in the process of moving. Anything that makes the load lighter is better. Doubt you see these around in most stores. I understood the advantages and bought several hundred and sold them at yard and flea markets. Maybe got ~50 left. Don't even have to complete the circuit under test, a techie's dream. In the right hands, so very, very nice. Results will vary with your ability to use it or even understand why it works.

    Amazing little critters in the right hands. You can never know the answer to your question completely without a Megger and the technical skills that are required to interpret the results.
     
  5. Jena

    Jena Well-Known Member

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    Hmmm....

    I did check the boxes after I found the extra volts. I just put the tester on the outside of all the boxes to see if any of them were hot. None of them showed anything. I was kind of hoping one box would be hot and thus tell me where to look.

    I did do a little bit of funny pig-tailing in one box. I needed to put 4 wires together, but the wire nuts only do 3, so I kind of linked them together. I will go buy bigger wire nuts and replace that mess. That may solve the problem. It is in the box with the extra volts.

    I don't know exactly what kind of tester I have. It's my husband's. He showed me how to use it and said "Be careful, don't lose that, it was expensive". It is digital. It has lots of buttons that he said I wouldn't need.

    As this is in my chicken barn, I really want to find the problem. I've had stray voltage in there before (due to a bad fan wire). I found the problem because the chicks wouldn't eat out of one feeder. It was on damp ground near the bad wire. I could barely feel the electricity in it, but those birds sure could. I don't know if this could cause the same kind of problems, but I'd just as soon have it perfect!

    I might change my mind about that after spending a lot of unproductive time accomplishing nothing.

    I will send a PM regarding the megger thingy. Thanks!

    Jena
     
  6. Cosmic

    Cosmic Well-Known Member

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    Meggers are what actually are used to find the source of your problem. Lots of different types. They measure the resistance to ground across insulation or any part of a circuit. Normally you hook up and then disconnect parts or break up the circuit to isolate the faults. Megger the entire circuit and then break it down to find where the fault is by isolation of the ground or bad part. The megger generates the voltage, the circuit is always de-energized.

    http://www.byramlabs.com/megger_insulation_resistance.php

    You can do a bit of the same thing with an ohmmeter, just not as good. Ohmmeter gives a static type measurement, megger is a dynamic type measurement.

    Your gizmo tester is on the way. Not a true megger but can be used a bit in the same way to find insulation breaks / faults. Only with the gizmo the circuit is powered.
     
  7. aaatraker

    aaatraker Well-Known Member

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    Before tearing into all the boxes, eliminate the most likely
    componet that is different in that circuit, the switch, as being the problem. replace it, then check the voltage.
    make sure the power is off before doing the switch replacement

    kurt
     
  8. Jena

    Jena Well-Known Member

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    10-4.

    The power is not hooked up yet, so it is always off. I tested it by having hubby make me a by-pass. He scares me....he hooked up some wire, stuck it in the live fuse box and told me to start checking. He tried to get me to hold the wires in the fuse box, but I gracefully declined :)
     
  9. John Hill

    John Hill Grand Master

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    I suspect that your work is OK and that the meter is just a bit too sensitive.

    What you are likely seeing with your meter is voltage without current, once any current starts to flow the voltage will likely drop to practically zero. Your meter is so sensitive that it can measure voltage with almost no current flowing. I hope that makes sense?

    The test lamp advice is good advice. All you need is a lamp socket with two wires.

    I suspect if you were to connect your test lamp across the probes of your meter then do your test the 30V would disappear.

    Be careful.
     
  10. Cosmic

    Cosmic Well-Known Member

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    John is probably right on.

    A lot of digital meters are screwy, especially on AC readings under no load conditions. Some refuse to do VAC well at all.

    The best is the old meters with a needle type movement. That or maybe the Gizmo, if you don't have a Megger handy.

    BTW - Jena, Fordy will put your Gizmo in the mail tomorrow. No sense asking any more, they are all gone. Talk about a crying need. Always knew I had the good eye for a gadget. :rolleyes:
     
  11. fordy

    fordy Well-Known Member

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    ..............Cos , Thank You . I will be Mo' than happy to pay Da postage fer that device , please just let me know . fordy.. :eek: :)
     
  12. Rowdy

    Rowdy Well-Known Member

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    Just bumping the post, wondering if you ever found the problem....
     
  13. Jena

    Jena Well-Known Member

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    As a matter of fact...

    I wired the other two circuits that were basically the same thing. All of them did the same thing. 30v when the switch was off. A test lamp does not come on though.

    Since they all are doing it, I assume it is the cheapo switches I bought and will replace them at some point.

    Thanks
    Jena
     
  14. John Hill

    John Hill Grand Master

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    I dont think you cheapo switches are at fault, in fact I suspect everything is OK.

    Where are you measuring the 30V between? I mean, exactly where do you put the two probes of your meter when you do the test?
     
  15. Jena

    Jena Well-Known Member

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    When the circuit is hot, but the switch is off, I get the 30v from sticking the probes in the outlets controlled by the switches. I can also get it by sticking the probes on the ground screw and "out" screw of the switch itself.

    Jena
     
  16. agmantoo

    agmantoo agmantoo Supporter

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    You did not try the lamp suggestion did you? :rolleyes:
     
  17. John Hill

    John Hill Grand Master

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    Jena, I suspect their it absolutely nothing wrong with those switches! But you can test for this by, after taking the power off of course, removing the hot wire right off the switch and taping it safely out of the way then put the power on again and do your meter test. I think you will find the volts are still there.

    Although I feel you have no problems and have done a good job of the installation I must say that electricity has the potential to spoil your whole day and you are quite wise to be cautious. As already suggested the megger test is the orthodox way of proving your circuit is safe.

    While trying to avoid getting too 'technical' the easiest way I can describe what I think is going on is that the wires to your outlet are acting as a sort of 'aerial'** and are picking up the mains voltage that is in the air all around us. But this is voltage only, there is no appreciable current and without current there is no power and that is why the test lamp does not light.

    **For technical folks: The phase wire from the switch to the outlet is insulated from everything when the switch is open and either by inductive of capacitive coupling it becomes charged enough for the very high impedance meter to show a reading.

    On the top floor of our house we have 75V showing on a high impedance meter under a similar test conditions but nothing on a moving coil multimeter, our mains are 240V.
     
  18. aaatraker

    aaatraker Well-Known Member

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    Hi Jena, sounds like your almost done, with your project. Remember to mark the circuits in the panel, you could also mark the outlets with the circuit, for ease of troubleshooting in the future.

    Well done and I hope you had fun

    kurt
     
  19. Jena

    Jena Well-Known Member

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    Hmmm...that non-technical stuff makes sense. All the outlets showing voltage are up in the rafters. It seems height makes a difference?

    Jena
     
  20. Jena

    Jena Well-Known Member

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    Yes I did! The lamp did not light :)

    :slap: "Don't you roll your eyes at me!!!" I have teenagers, I get enough of that at home! Hehehe

    Jena