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Thread: Stray voltage on ground wire in townhouse

  1. #21
    Join Date
    Jun 2010
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    1,905
    Quote Originally Posted by WestCascadesElec View Post
    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
    That's unnecessary waste of time. Disconnect electronics from coax so it no longer provides secondary ground path. Set up the two sockets with light bulbs I mentioned earlier. It doesn't take much load to notice an effect for a very loose or lost neutral. It'd take a high inrush such as a vacuum cleaner to produce noticeable brightening if it's only slightly loose. Provided that connection is good at the panel lug, the problem is outside of the homeowner's. You'll need to make impeccable documentation since there will be a question over who pays for appliance damage as well as replacing the section of damaged coax.

    Check voltage between the neutral bar in the panel and a small part of feeder neutral with a line-to-neutral load in place. Aluminum wire issues can look fine to the eye when it is not fine electrically.

    Ground does not carry current under normal conditions. Main breaker off. You should see 0v between incoming neutral and ground at breaker panel.

    Check ohms between incoming neutral and ground. It should have a resistance indistinguishable from leads shorted together. No response on meter means open. Some resistance (higher than leads shorted together to couple thousands of ohms) means loose connection which means you have to call the power company which you people call the hydro.
    Last edited by Electric-Light; 09-14-17 at 04:12 AM.

  2. #22
    Join Date
    Aug 2017
    Location
    Vancouver, Canada
    Posts
    5
    I did read post 13 but that is not practical. I will need over 400' of extension cord and I will also need to open up the main meter stack and disconnect switch as well. Strata will not let me do all of this and leave the electrical room open with cords running out and exposed equipment. I will try the two lamp method and see what happens. Coax line already shows melting on the incoming

  3. #23
    Join Date
    Dec 2012
    Location
    Placerville, CA, USA
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    17,978
    Quote Originally Posted by WestCascadesElec View Post
    I did read post 13 but that is not practical. I will need over 400' of extension cord and I will also need to open up the main meter stack and disconnect switch as well. Strata will not let me do all of this and leave the electrical room open with cords running out and exposed equipment. I will try the two lamp method and see what happens. Coax line already shows melting on the incoming
    Assuming (always a big if, but probably justified in this case) that the other end of the coax is really at earth ground and probably has a metallic path to the POCO MGN, you surely have an open neutral somewhere. Find it. Start at the service!

  4. #24
    Join Date
    Apr 2008
    Location
    Ann Arbor, Michigan
    Posts
    6,189
    170914-1953 EDT

    WestCascadesElec:

    Since a 400 ft wire is a problem, then try these possibilities.

    1. Assume the power company transformer is grounded, and there is no major ground current problem (current in the earth), then put a screw driver in the earth near your main panel, shouldn't require as much as 100 ft, or use a metallic water pipe as a transformer neutral voltage reference. Your voltmeter measuring current is very small (10 megohm at whatever applied voltage).

    The ground reference test lead could be #40 or smaller, but that is not practical, so #20 insulated hookup wire would work. You do not need extension cords, just in some cases an extension cord is a convenient way to get a long test lead. Also 400 ft of hookup wire would work. 400 ft is not a long distance.

    2. Unless there is a major earthing problem the approach of 1. should allow you to find the problem at the voltages (10 V) you are seeing.

    3. Go to an adjacent townhouse and reference from one of their EGC points.

    It is dark out presently, but in the dark, I made a measurement over about a 125 ft distance just below my primary lines and from close to the pole transformer ground rod to another point. This voltage was 120 millivolts (0.12 V) unfiltered using screwdrivers at both ends with a Fluke 27.

    There are many ways to study your problem, just be inovative.

    .

  5. #25
    Join Date
    Jun 2010
    Posts
    1,905
    I would say it's isolated to his place if lights are not going haywire in the electrical room and neighbors are not scrambling as well and the cabinet in the electrical room is probably at proper potential. I'd say it's an aluminum wire connection at a lug or the meter base. Why wouldn't you get the poco to check it out already??

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