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Thread: Stray voltage on ground wire in townhouse

  1. #11
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    Aug 2017
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    Thanks for all the responses, I will be starting this next week as its just so busy right now. For the previous response saying that the neutral and ground should be connected that is not allowed up here in our cec. Bonding screw has to be removed on this panel as it is considered a sub panel since there is a main meter stack in the electrical room for each bank of townhouses. I believe its called division of currents which van cause a ground loop.

  2. #12
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    Dec 2012
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    Placerville, CA, USA
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    Quote Originally Posted by WestCascadesElec View Post
    Thanks for all the responses, I will be starting this next week as its just so busy right now. For the previous response saying that the neutral and ground should be connected that is not allowed up here in our cec. Bonding screw has to be removed on this panel as it is considered a sub panel since there is a main meter stack in the electrical room for each bank of townhouses. I believe its called division of currents which van cause a ground loop.
    The proper term is objectionable current over the EGC wires (which are in parallel with that section of neutral and so will end up carrying normal current) rather than ground loop.
    One way a true ground loop can occur is where two or more EGCs are connected at equipment end (or anywhere but the panel bus) forming a loop in which magnetic fields can induce unwanted currents, which in turn can cause voltage offsets.

  3. #13
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    Apr 2008
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    170831-1640 EDT

    WestCascadesElec:

    At your main panel measure the voltage between between neutral and EGC.

    From your other information it is quite probable that this will be large, like a moderate percentage of your 10 to 12 V.

    Go find where neutral and EGC are bonded together. Use this as the reference point for your long test lead. Relative to this said reference point measure the voltage drop to neutral at the main panel, and to the EGC at the main. With these voltage drops known they should lead us to where the principle problem is located.

    .

  4. #14
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    Aug 2017
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    Currently working on this today. What has happened so far, shut off main and no more stray voltage. Measured neutral to ground and began turning on breakers one by one. Voltage slowly starts creeping up from 0.5v to the 8.1v by the time all breakers are turned on. Is there any possibility that this could just be induced voltage. We are currently opening up boxes and looking for anything out of the ordinary one circuit at a time

  5. #15
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    Quote Originally Posted by WestCascadesElec View Post
    Currently working on this today. What has happened so far, shut off main and no more stray voltage. Measured neutral to ground and began turning on breakers one by one. Voltage slowly starts creeping up from 0.5v to the 8.1v by the time all breakers are turned on. Is there any possibility that this could just be induced voltage. We are currently opening up boxes and looking for anything out of the ordinary one circuit at a time
    The neutral and ground (GES/GEC/EGC) are supposed to be metallically bonded. There is no way that you could get a voltage of 8.1 volts with a solid metallic connection.

    More likely is that the two wiring meshes are not in fact bonded together AND you have a high resistance neutral somewhere which is causing the neutral to get farther and farther from ground the more unbalanced current it is carrying.

    The only way you might possibly be seeing induced (phantom) voltage on the EGC is if it is not in fact connected to either the neutral or the ground electrodes.

  6. #16
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    May 2014
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    To get a better understanding of the neutral situation I would start with turning off the main breaker and carefully remove the service neutral and the from terminal and the grounding electrode conductor and isolate both of them.
    Then see what you get for voltages between the hot legs, hot to neutral, and neutral to the EGC.

  7. #17
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    Jun 2010
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    1,923
    Where does ground and neutral merge in Canada?

    Turn off every single breaker and disconnect the coax that's getting hot.

    I prefer keyless lamp sockets with built-in recep setup as MWBC (or N, L1, L2 and L3 if you work 208Y/120 often). You connect neutral to neutral, one socket to L1, the other socket to L2 and fit incandescent in both. Find empty breakers or vacate them and energize just these two sockets.

    Plug something into the side socket that draws a few amps. A loose neutral make the loaded one dim and the other one brighten. After you check the feeder neutral connection from feeder to panel is good you've ruled it out as problem before his panel. This is a utility problem now. No need to open every box at this point.

    An isolated 1-2kVA 240 to 120 (not auto transformer) can be used to provide power for refrigerator from L-L until utility can come by but everything else should be left off to avoid damage.

    The entire length of coax going back to the bonding point, as well as the Romex that supplied current to the branch connected to TV may need to be replaced if you see signs of heat damage.
    Last edited by Electric-Light; 09-12-17 at 09:57 PM.

  8. #18
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    Aug 2017
    Location
    Vancouver, Canada
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    Ground and neutral are connected at the main panel coming from the meter base. For the townhouse I am working on the ground and neutral are connected in the electrical room for the bank of townhomes being served. All panels downstream must have the bonding screw removed from the neutral bar to the panel frame. Didn't find anything today, will be working on Saturday to hopefully find this. Plan to disconnect everything in the panel and test each incoming wire individually to try and pinpoint what circuit and hopefully find which area of the house is the cause

  9. #19
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    If neutral and ground are bonded together, you shouldn't have anything between them, if close to the bonding point.

    As you get further away from that bonding point, the chance of measuring voltage between them increases because of voltage drop on the neutral (it will have voltage drop if there is current flowin in it)

    Voltage to the coax cable - you need to figure out which is closer to true ground the cable or the power system grounding. You could have current trying to come into the premises via the coax cable rather then having premises power system leaking to the coax, meaning the problem may be coming from outside the premises.

  10. #20
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    170913-2431 EDT

    WestCascadesElec:

    Did you pay any attention to what I wrote in post #13, and/or did you not understand what I said?

    Go find the point where neutral and EGC are supposed to be bonded together. Measure the voltage between the actual wires (neutral and EGC) (this means put your meter probes directly on the wires and not the terminals. or lugs). This voltage should be quite close to zero, obviously with no load it should be zero, but even with a full totally unbalanced load the reading should be close to zero.

    If this bond is good, then use this bonded location as the voltage reference to your meter to investigate were the large voltage drop is occurring. Don't worry about the bonded point to earth at this time. If there is a problem relative to earth solve that later. At this time don't use some earthed point as a reference, just use the bonded location.

    .

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