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  1. #1
    susan brown's Avatar
    susan brown Guest

    Default old 3 prong dryer receptacle to new 3 prong dryer receptacle

    I live in a very old building...I have a old 3 prong dryer receptacle that has a white wire, a black wire, and a bare copper wire...I need to change dryer receptacle...I am concerned about the copper wire...I know to place white where noted...and black can go straight across..my concern is the copper wire...can I place copper on bottom where outlet hole is different without any problems? receptacle is showing 247 on meter

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  2. #2
    Join Date
    Mar 2007
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    Spring Hill (Nashville), TN
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    Default Re: old 3 prong dryer receptacle to new 3 prong dryer receptacle

    Quote Originally Posted by susan brown View Post
    I live in a very old building...I have a old 3 prong dryer receptacle that has a white wire, a black wire, and a bare copper wire...I need to change dryer receptacle...I am concerned about the copper wire...I know to place white where noted...and black can go straight across..my concern is the copper wire...can I place copper on bottom where outlet hole is different without any problems? receptacle is showing 247 on meter
    The copper wire is the ground. I hope that you have a ground for the 240 circuit. If not, you really need to get with an electrician and have a ground installed for this circuit. It is dangerous to have an appliance like this ungrounded.

    Last edited by Scott Patterson; 05-25-2009 at 09:38 AM.
    Scott Patterson, ACI
    Spring Hill, TN
    www.traceinspections.com

  3. #3
    Join Date
    Mar 2007
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    Ormond Beach, Florida
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    26,248

    Default Re: old 3 prong dryer receptacle to new 3 prong dryer receptacle

    Quote Originally Posted by susan brown View Post
    I live in a very old building...I have a old 3 prong dryer receptacle that has a white wire, a black wire, and a bare copper wire...I need to change dryer receptacle...
    First, why do you need to change the receptacle? Installing a new dryer with a new dryer cord? If so, get a dryer cord which matches your existing receptacle.

    Second, do not change your receptacle to anything other than another 3-wire dryer receptacle DO NOT change it to a 4-wire dryer receptacle.

    receptacle is showing 247 on meter
    Nominal is 240 volts, which is 120 volts nominal each leg to ground, thus 240 volts between the leg. Reading 247 volt means you have 123.5 volts each leg, which is not a problem.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  4. #4
    Join Date
    Mar 2007
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    Charlotte NC Licensed in NC and SC
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    Default Re: old 3 prong dryer receptacle to new 3 prong dryer receptacle

    If you have a panel in that room or nearby you could have a new 4-wire cable pulled and install a new safer four prong outlet.

    Tell the building owner that he needs to have the whole building inspected (which I would be glad to do).


  5. #5
    Gerry Martin's Avatar
    Gerry Martin Guest

    Default Re: old 3 prong dryer receptacle to new 3 prong dryer receptacle

    Hi. If you only have three conductors (black, white and bare copper), the black and white are likely phase conductors and the bare is being used as a ground/neutral. This can be verified by a nominal voltage around 240 VAC between the white and black, and 120 VAC from black to bare and white to bare. If you must replace the outlet, use another 3 wire dryer outlet----it should be identical. DO NOT connect the existing wiring to a 4 wire outlet. Mr. Peck had the best advice, simply replace the cord on the dryer. If it is a new dryer, there should also be a bonding strap placed between the neutral and ground connections at the power connection area in the back of the dryer, if it is factory shipped with the jumper disconnected (4 wire connection). The installation literature should have instructions for this. Best wishes, GM


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