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  1. #1
    Join Date
    Jul 2012
    Posts
    24

    Default 2 Prong to 3 Prong

    Hey Guys,

    Got a question for you. My recent 1953 cape has many 2 prong outlets. I am looking to switch them over to 3 prong outlets. I checked the metal boxes and they are grounded. When I switched over to a 3 prong outlet, I added a ground wire from the outlet to the back of the box. I flipped on the breaker and the outlet shorted out.

    I then decided to remove the ground I added and the breaker/outlet works fine. I even checked the outlet and the 3rd prong is grounded.

    Any thoughts would be greatly appreciated.

    Thanks,

    Pat

  2. #2
    Join Date
    Dec 2010
    Location
    Houston Texas
    Posts
    2,360

    Default Re: 2 Prong to 3 Prong

    Pat,
    Since the outlet is grounded to itself, it gets grounded when you screw the outlet to the metal box. No need for the extra ground wire. This is the typical wiring for commercial work with the ground in the metal of the box / wire.

  3. #3
    Join Date
    Jul 2012
    Posts
    24

    Default Re: 2 Prong to 3 Prong

    Thanks for the info. So it is fine the way it is now?

    Thanks,

    Pat

  4. #4
    Join Date
    Dec 2010
    Location
    Houston Texas
    Posts
    2,360

    Default Re: 2 Prong to 3 Prong

    Yes,
    Unless Maurice says differently

  5. #5
    Join Date
    Jan 2011
    Location
    Columbiana, Alabama
    Posts
    623

    Default Re: 2 Prong to 3 Prong

    Pat, if you conected a wire from the box to the green screw on the new 3 prong receptacle and it tripped a breaker you may have what we call a "bootleg ground".

    That is when someone with an ungrounded two wire system connects a green jumper wire from what they think is the neutral wire to the box. Then extends the two wire circuit with romex having a ground.

    Electrically it now appears that the house has a three wire grounded circuit.

    I suspect this is what happened in your case. The "hot" was tied to a metal box and energized it. This is very dangerous especially in a wet location. Say you plug in a toaster in a kitchen and touch it and the sink. You would get a very serious shock.

    There are ways to do what you want to do but, finding and removing that "bootleg ground is the first step. Then, there are two options:

    1) The best method: Run a green or bare wire (#12) to a good ground, such as a properly grounded panel or cold water pipe, to the circuit you would like to convert to three wire and use conventional 14-2 w/g or 12-2 w/g romex, from there.

    2) Install a GFCI receptacle at the first ungrounded box coming from the power panel and attach one of the labels that came with the GFCI that says "ungrounded receptacle" to the cover. Also, attach one to every downstream receptacle cover.

    You can now change out the two prong plugs to a three prong plugs dowstream and they will have a much higher level of safety. But, computers etc. will not be fully protected against static and lightning damage, as they should be.
    Good Luck from Columbiana, Alabama
    Maurice Turgeon, Hidden Content

  6. #6
    Join Date
    Jun 2007
    Location
    Fayette County, Ohio
    Posts
    5,557

    Default Re: 2 Prong to 3 Prong

    There should be no difference in connecting the ground wire to the box and the connection made ny the mounting screws to the box. If it cased the breaker to trip, you either shorted something out or connected to the wron screw.

    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  7. #7
    Join Date
    May 2008
    Location
    Pacific Northwet
    Posts
    1,360

    Default Re: 2 Prong to 3 Prong

    Check out this video that discusses bootleg grounds:

    https://www.youtube.com/watch?v=iLk-6pvSlWg
    The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.

  8. #8
    Join Date
    Jan 2011
    Location
    Columbiana, Alabama
    Posts
    623

    Default Re: 2 Prong to 3 Prong

    Quote Originally Posted by Fencepost View Post
    Check out this video that discusses bootleg grounds:

    https://www.youtube.com/watch?v=iLk-6pvSlWg
    Fencepost, good demonstration but saying the bootleg jumper from neutral to ground is OK, but may not be legal everywhere is wrong, dangerous and mis-leading.

    Also, the beeper probe is useful for safety reasons but should be used very carefully for trouble-shooting reasons.
    Having said that, I never leave home without one.
    Good Luck from Columbiana, Alabama
    Maurice Turgeon, Hidden Content

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