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Thread: "Open Ground" Reading on GFCI Circuit

  1. #1
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    May 2012
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    Sanger, Texas
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    "Open Ground" Reading on GFCI Circuit

    Hi all...first time poster... long time lurker, but I come with a serious concern. When I bought my house a few years back, it came with a detached 2-1/2 car garage, perfect for the wood shop I've always wanted. The previous owner had a GFCI installed that has 4 outlets behind it. I've never had a problem with any of the outlets powering anything I've plugged into them, including my refrigerator, TV, & cable box.

    As I was rearranging my shop today, I unplugged my weather radio from a separate outlet and plugged it into a GFCI-protected outlet, and it wouldn't turn on. I plugged it into its original outlet and it still wouldn't turn on. I chose to plug in a circuit tester to see if the GFCI protected outlet was faulty and came up with a reading that there was an open ground. All this despite the fact that the TV & reefer were still working.

    I hit the Test button on the GFCI and it tripped like it was supposed to. I then went into my kitchen in the house and plugged the circuit tester into the GFCI protected outlets there, and got a normal reading...as I did in the bathroom.

    So I've spent the last two hours searching this forum to get some info and have finally decided to just ask...have I got a serious problem here? My background is in electronics so I know the basics of electricity, but after lurking around these forums I have come to the realization that I know nothing about wiring a house. Should I be calling in a professional to look at this or am I just misreading the signs?

    Any help would be greatly appreciated,

    John

  2. #2
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    Placerville, CA, USA
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    Quote Originally Posted by gaftech View Post
    Hi all...first time poster... long time lurker, but I come with a serious concern. When I bought my house a few years back, it came with a detached 2-1/2 car garage, perfect for the wood shop I've always wanted. The previous owner had a GFCI installed that has 4 outlets behind it. I've never had a problem with any of the outlets powering anything I've plugged into them, including my refrigerator, TV, & cable box.

    As I was rearranging my shop today, I unplugged my weather radio from a separate outlet and plugged it into a GFCI-protected outlet, and it wouldn't turn on. I plugged it into its original outlet and it still wouldn't turn on. I chose to plug in a circuit tester to see if the GFCI protected outlet was faulty and came up with a reading that there was an open ground. All this despite the fact that the TV & reefer were still working.
    I hit the Test button on the GFCI and it tripped like it was supposed to. I then went into my kitchen in the house and plugged the circuit tester into the GFCI protected outlets there, and got a normal reading...as I did in the bathroom.

    So I've spent the last two hours searching this forum to get some info and have finally decided to just ask...have I got a serious problem here? My background is in electronics so I know the basics of electricity, but after lurking around these forums I have come to the realization that I know nothing about wiring a house. Should I be calling in a professional to look at this or am I just misreading the signs?

    Any help would be greatly appreciated,

    John
    The GFCI receptacle will work just fine, including tripping from its own test button, without having a ground (EGC) connection.
    This is allowed by code if the original receptacle was a two wire receptacle which was legal at the time it was installed.
    By Code, the receptacle must be marked that no equipmentground is present.
    Or it may be that the wire EGC or raceway EGC is simply not connected properly somewhere in along the way back to the panel.

    The reason that the built-in test button works but the tester cannot trip it is that the internal test button can route current around the sensor to create a known imbalance. The external tester mustt be abl
    e to divert some current to the EGC to create an imbalance
    .

  3. #3
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    Sanger, Texas
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    OK, So why am I reading an open ground on the GFCI circuits in the shop, and not in the house?

  4. #4
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    Quote Originally Posted by gaftech View Post
    OK, So why am I reading an open ground on the GFCI circuits in the shop, and not in the house?
    Because there is no ground run to the outlets in the shop but there is in the outlets inside the house.
    Either the wires to the first shop outlet are incorrect or the ground connection to the shop sub-panel is incorrect.
    If the shop and the house were both wired without grounds (and were old enough to allow that) the wiring in the house may have been updated at some point.

  5. #5
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    NE Nebraska
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    You possibly have no equipment grounds in the shop at all. Either the EGC with the feeder is missing, damaged, etc. Or if permitted to not run a separate EGC or if supplied via a service the bonding jumper is not installed in the main panel.

  6. #6
    Join Date
    Dec 2004
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    Fort Collins, CO NEC: 2014
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    Chances are very good you have an open neutral. Call an electrician.

  7. #7
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    May 2012
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    Sanger, Texas
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    Thank you for your input. At the time that I bought the house, I wasn't aware of this forum, so as a typical homeowner, pretty much blew off anything the inspectors report said, as long as the sale of the house went through. Here is a portion of what the inspector's report said:

    II. ELECTRICAL SYSTEMS
    A. Service Entrance and Panels - Comments
    oService drop is loose and/or pulling away ¨Service line is less than 10 feet above the ground
    Main Disconnect Panel Type of Wire:
    þCopper ¨Aluminum
    ¨Panel(s) are not labeled properly ¨Panel has more than 6 main disconnects
    ¨Panel(s) are loose at the wall ¨Panel inner safety cover is loose or missing
    ¨One or more knockouts are missing ¨Ground wire/rod could not be verified
    þGrounds and neutrals on same bus bar (typical of older home installations)
    ¨Ground wire not connected correctly to grounding rod
    ¨Incorrect size of breakers/fuses ¨Incorrect wire on breakers/fuses
    ¨Double lugged breakers/fuses in use ¨Electrical line not properly shielded through panel
    þA/C condensing unit #1 specifies max amp breaker of 45 and a 60
    ¨Pointed screws used to secure panel ¨One or more screws missing from panel
    ¨Some breakers are loose in panel ¨Some breakers overheating in panel
    þRecommend a licensed electrician evaluate the system to determine what, if any, repairs may be necessary.

    hClick image for larger version. 

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    I will contact a qualified electrician to make sure my shop is up to code. I know that the ground has been isolated from the neutral in the subpanel, but I don't know if it's been done properly. Thanks again, for the advice.

  8. #8
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    Apr 2008
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    Quote Originally Posted by George Stolz View Post
    ... Call an electrician.
    Good advice.

    This may be a NEC 406(D)(3) installed replacement missing the required "No Equipment Ground" label.
    Last edited by jeremysterling; 10-19-13 at 11:32 PM.

  9. #9
    Join Date
    Dec 2004
    Location
    Fort Collins, CO NEC: 2014
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    15,488
    Plug testers are not foolproof. An open neutral can read as an open ground, and the smoke escaping the radio supports that conclusion. An open ground would not effect the operation of the radio.

    Don't plug anything else in, and shut the power off to the shed while you wait for the electrician.

    Quote Originally Posted by gaftech View Post
    I've never had a problem with any of the outlets powering anything I've plugged into them, including my refrigerator, TV, & cable box.

    As I was rearranging my shop today, I unplugged my weather radio from a separate outlet and plugged it into a GFCI-protected outlet, and it wouldn't turn on. I plugged it into its original outlet and it still wouldn't turn on. I chose to plug in a circuit tester to see if the GFCI protected outlet was faulty and came up with a reading that there was an open ground.

  10. #10
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    May 2012
    Location
    Sanger, Texas
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    5
    Quote Originally Posted by George Stolz View Post
    ... and the smoke escaping the radio supports that conclusion.
    I'm not sure where you got the impression that there was smoke, but I've had no indication that anything was wrong until I moved the weather radio from a non-GFCI protected receptacle to the GFCI protected receptacle. I've run the reefer, TV, computer, and many power tools off the GFCI circuit for over a year with no indication of a problem. It wasn't until I plugged in the circuit tester that I even suspected a problem.

    That said, I will get an electrician out here to check everything out.

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