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    dechabot's Avatar
    dechabot Posts: 5, Reputation: 1
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    #1

    Jan 13, 2013, 01:53 PM
    Maximum number of conductors in receptacle box
    Hello. If you have two 14/2 with ground cables coming into a 3"x2"x2-1/2" electrical box with a duplex receptacle and internal clamps, is this acceptable by NEC code? All the outlets in my house are wired this way.

    Here is my calculation for required electrical box volume:

    8 (4 conductors)
    2 (ground)
    4 (receptacle)
    2 (internal clamps)
    -------------------
    16 cu in.

    The 3" electrical box with a duplex receptacle and internal clamps, is this acceptable by NEC code? All the outlets in my house are wired this way.

    Here is my calculation for required electrical box volume:

    8 (4 conductors)
    2 (ground)
    4 (receptacle)
    2 (internal clamps)
    -------------------
    16 cu in.

    The 3"x2-1/2" box would seem to have inadequate volume. Am I misinterpreting the NEC code? Can someone help me to understand? Thanks.
    donf's Avatar
    donf Posts: 5,679, Reputation: 582
    Printers & Electronics Expert
     
    #2

    Jan 13, 2013, 02:36 PM
    Just a quick look -

    Regardless of the number of grounds - use 1
    The duplex receptacle is "one Yoke" - use 2
    Cable clamps - use I

    I take a look at the code later and correct any mistakes. Just so you know, the multiplier for 14 AWG is 2.0
    dechabot's Avatar
    dechabot Posts: 5, Reputation: 1
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    #3

    Jan 13, 2013, 02:57 PM
    Hi Donf. Thanks for your reply. Those are the multipliers I used in my calculation, as follows:

    (4 conductors x 2.0 cu. in. each) = 8
    (grounds x 2.0 cu. in.) = 2
    (1 receptacle x 4.0 cu. in) = 4
    (clamps x 2.0 cu. in.) = 2

    Total capacity required = 16 cu. in.

    Given that the code says that a 3" x 2" x 2-1/2" box has a min capacity of 12.5 cu. in. it would seem that the boxes used in my house are under the required capacity, which is hard to believe.
    donf's Avatar
    donf Posts: 5,679, Reputation: 582
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    #4

    Jan 13, 2013, 03:18 PM
    4 conductors X 2.0 = 8.0
    Ground X 2.0 = 2.0
    1 Yoke X 2.0 = 2.0
    clamp X 2.0 = 2.0

    14.0

    Are you sure you don't have 3" X 2" X 2 3/4"?
    dechabot's Avatar
    dechabot Posts: 5, Reputation: 1
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    #5

    Jan 13, 2013, 03:24 PM
    Quote Originally Posted by donf View Post
    4 conductors X 2.0 = 8.0
    Ground X 2.0 = 2.0
    1 Yoke X 2.0 = 2.0
    clamp X 2.0 = 2.0

    14.0

    Are you sure you don't have 3" X 2" X 2 3/4"?
    Hi Don,
    They are 2-1/2" deep. I guess it Is possible that the code requirements are different in Canada (where I reside). When you say "yoke", do you mean the receptacle? I thought the receptacle counted as 2 x 2.0 cu. in.
    donf's Avatar
    donf Posts: 5,679, Reputation: 582
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    #6

    Jan 13, 2013, 03:41 PM
    Hey Canada, how stands your great nation.

    I believe that the box fill code would be the same. It's more likely the builder just shaved the box size by a tad, if he even thought about it at all.

    If the home is an older home, I'd just leave it alone.

    By the way a "Yoke" is what the receptacles mount onto.See NEC 314.16(B)(4)
    dechabot's Avatar
    dechabot Posts: 5, Reputation: 1
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    #7

    Jan 13, 2013, 03:47 PM
    Quote Originally Posted by donf View Post
    Hey Canada, how stands your great nation.

    I believe that the box fill code would be the same. It's more likely the builder just shaved the box size by a tad, if he even thought about it at all.

    If the home is an older home, I'd just leave it alone.

    By the way a "Yoke" is what the receptacles mount onto.See NEC 314.16(B)(4)
    Hey Don. I appreciate your help. It doesn't sound like anything to worry about. That's the main thing. All the best. Daniel
    stanfortyman's Avatar
    stanfortyman Posts: 5,598, Reputation: 279
    Electrical & Lighting Expert
     
    #8

    Jan 13, 2013, 03:52 PM
    It's really nothing to worry about. In the US they used to use crazy small boxes. Over the years the code cycles have taken this into account. This is one of the things that makes working in older homes a pain.
    dechabot's Avatar
    dechabot Posts: 5, Reputation: 1
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    #9

    Jan 13, 2013, 03:57 PM
    Quote Originally Posted by stanfortyman View Post
    It's really nothing to worry about. In the US they used to use crazy small boxes. Over the years the code cycles have taken this into account. This is one of the things that makes working in older homes a pain.
    Thanks stanfortyman. Daniel

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