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  1. #1
    Join Date
    Feb 2010
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    Wenatchee Wa
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    301

    Default 4 wire feeders for outbuildings

    Hey all,

    I have a general question on residential sub- subpanels (distribution panel). When was 4 wires feeds required for out buildings?

    If anyone has some dates on when this was implemented I would sure love to know.

    Thanks in advance.

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    Don Hester
    NCW Home Inspections, LLC
    Wa. St. Licensed H I #647, WSDA #80050, http://www.ncwhomeinspections.com

  2. #2
    Join Date
    Mar 2007
    Location
    Charlotte NC Licensed in NC and SC
    Posts
    597

    Default Re: 4 wire feeders for outbuildings

    Its not even required nowadays as long as no other metallic path is present between the detached building and the house. Determining this is beyond the scope and should be done by an electrician. A ground rod or equivalent is also needed unless <25 ohms can be proven on the main rod.

    Bruce King, B.A. King Home Inspections, LLC
    www.BAKingHomeInspections.com
    Certified Master Inspector, Independent Inspectorwww.IndependentInspectors.org

  3. #3
    Join Date
    Feb 2010
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    Wenatchee Wa
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    301

    Default Re: 4 wire feeders for outbuildings

    Quote Originally Posted by Bruce King View Post
    Its not even required nowadays as long as no other metallic path is present between the detached building and the house. Determining this is beyond the scope and should be done by an electrician. A ground rod or equivalent is also needed unless <25 ohms can be proven on the main rod.
    Bruce, I understand and should of made it a bit clearer/defined. I still want to know when it became effective.

    And just because it is beyond scope does not mean I can not know ; ) I am curious.

    And as you know sometimes the electrician do not even know

    Don Hester
    NCW Home Inspections, LLC
    Wa. St. Licensed H I #647, WSDA #80050, http://www.ncwhomeinspections.com

  4. #4
    Join Date
    Mar 2007
    Location
    Charlotte NC Licensed in NC and SC
    Posts
    597

    Default Re: 4 wire feeders for outbuildings

    Quote Originally Posted by Don Hester View Post
    Bruce, I understand and should of made it a bit clearer/defined. I still want to know when it became effective.

    And just because it is beyond scope does not mean I can not know ; ) I am curious.

    And as you know sometimes the electrician do not even know

    It also depends on whether or not the feeder has a metal conduit for the ground. I think 1996 had some clarifications and changes but basically a three wire feed without a metal conduit has been wrong for decades even though it was allowed by most AHJ's due to the cost or availability of 4-wire cable several years back.

    Maybe one of the code experts can chime in here.

    Bruce King, B.A. King Home Inspections, LLC
    www.BAKingHomeInspections.com
    Certified Master Inspector, Independent Inspectorwww.IndependentInspectors.org

  5. #5
    Join Date
    Aug 2008
    Location
    Maryland
    Posts
    1,898

    Default Re: 4 wire feeders for outbuildings

    Quote Originally Posted by Bruce King View Post
    Its not even required nowadays as long as no other metallic path is present between the detached building and the house. .
    The option of installing a 3 wire feeder was removed in the 2008 NEC regardless of other metallic paths between buildings. An existing 3 wire feeder can remain.

    All answers based on unamended National Electrical codes.

  6. #6
    Join Date
    Mar 2007
    Location
    Ormond Beach, Florida
    Posts
    26,243

    Default Re: 4 wire feeders for outbuildings

    Just repeating what Jim posted to make sure it is understood: the 3-wire option is *no longer allowed*, regardless of what does or does not connect the two structures.

    Also, as Jim stated, that change was in the 2008 NEC.

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

  7. #7
    Join Date
    Feb 2010
    Location
    Wenatchee Wa
    Posts
    301

    Default Re: 4 wire feeders for outbuildings

    Bruce, Jim and Jerry, Perfect this is exactly what I was looking for.

    Thanks

    Don Hester
    NCW Home Inspections, LLC
    Wa. St. Licensed H I #647, WSDA #80050, http://www.ncwhomeinspections.com

  8. #8
    Join Date
    Aug 2008
    Location
    Maryland
    Posts
    1,898

    Default Re: 4 wire feeders for outbuildings

    Thanks Jerry.

    All answers based on unamended National Electrical codes.

  9. #9
    Join Date
    Dec 2007
    Location
    Chico,Ca
    Posts
    423

    Default Re: 4 wire feeders for outbuildings

    Quote Originally Posted by Bruce King View Post
    Its not even required nowadays as long as no other metallic path is present between the detached building and the house. Determining this is beyond the scope and should be done by an electrician. A ground rod or equivalent is also needed unless <25 ohms can be proven on the main rod.

    If a rod is used for a grounding electrode, a 2d rod must be driven unless 25 Ohms of resistance or less can be proven. There is nothing about the "main rod" resistance exempting a GEC at a detached structure.

    Here is the text from the 2008 NEC.

    250.56 Resistance of Rod, Pipe, and Plate Electrodes. A
    single electrode consisting of a rod, pipe, or plate that does
    not have a resistance to ground of 25 ohms or less shall be
    augmented by one additional electrode of any of the types
    specified by 250.52(A)(4) through (A)(8). Where multiple
    rod, pipe, or plate electrodes are installed to meet the requirements
    of this section, they shall not be less than 1.8 m
    (6 ft) apart.
    FPN: The paralleling efficiency of rods longer than 2.5 m
    (8 ft) is improved by spacing greater than 1.8 m (6 ft).


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