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Thread: Weight rating 4 square boxes

  1. #31
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    Quote Originally Posted by jumper View Post
    What is a bracket box? Box with a bracket/strap for mounting?

    Attachment 21443
    Yes, that is the style of box I am referring to and not for purposes of hanging a fan, only luminaires with a mud ring that says it is rated for 50lbs. Obviously it would be irresponsible to attach the tabs with some #6 screws or wimpy nails or staples or something. What gets me is that there is not a clear answer on this one. Seems way more stout than a cheesy carlon plastic nail on. Or, is the weight rating on the mud ring itself the part that actually matters?

  2. #32
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    Quote Originally Posted by tom baker View Post
    A device box uses 6-32 screws and can be used for a wall mount luminaire the weight limit is 6 pounds 314.27
    Outlet boxes uses 8-32 screws and are rated for 50 pounds, 314.27

    So a box with 8-32 is good for 50 pounds

    Tom, I think this is the answer. Thank you. The mud ring is attached to the box with number 8s and we always use 8s for securing the bracket.

  3. #33
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    Quote Originally Posted by tom baker View Post
    A device box uses 6-32 screws and can be used for a wall mount luminaire the weight limit is 6 pounds 314.27
    Outlet boxes uses 8-32 screws and are rated for 50 pounds, 314.27

    So a box with 8-32 is good for 50 pounds
    Don't know how you reached that conclusion. I see the part about ceiling boxes having to support a maximum of 50 Lbs, I see nothing about screws.

    2) Ceiling Outlets. At every outlet used exclusively for
    lighting, the box shall be designed or installed so that a lu-
    minaire or lampholder may be attached. Boxes shall be re-
    quired to support a luminaire weighing a minimum of 23 kg
    (50 lb). A luminaire that weighs more than 23 kg (50 lb)
    shall be supported independently of the outlet box, unless
    the outlet box is listed and marked for the maximum weight
    to be supported.

    The Hand Book explanation is the only place screw sizes are mentioned and that refers to wall boxes:

    The exception to 314.27(A)(1) permits luminaires such as
    wall-bracket types or sconces weighing less than 6 lb to be
    supported by a device box using No. 6 or larger screws. De-
    vice boxes designed for the mounting of snap switches,
    receptacles, and other devices usually have 6-32 screws (No
    6 screws with 32 threads per inch). Generally, device boxes
    are not suitable for supporting other than lightweight wall-
    mounted luminaires.

    So my conclusion is that if a box isn't marked with a 50 Lb or more weight rating it can't be used to support a ceiling fixture. The mud ring has nothing to do with it and neither do the screws, however a box with a 50 Lb rating or better will have 8/32 or larger screws. 8/32 screws do not mean the box is 50 Lb rated though.

    -Hal

    Last edited by hbiss; 10-29-18 at 03:31 AM.

  4. #34
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    Quote Originally Posted by hbiss View Post
    Don't know how you reached that conclusion. I see the part about ceiling boxes having to support a maximum of 50 Lbs, I see nothing about screws.

    2) Ceiling Outlets. At every outlet used exclusively for
    lighting, the box shall be designed or installed so that a lu-
    minaire or lampholder may be attached. Boxes shall be re-
    quired to support a luminaire weighing a minimum of 23 kg
    (50 lb). A luminaire that weighs more than 23 kg (50 lb)
    shall be supported independently of the outlet box, unless
    the outlet box is listed and marked for the maximum weight
    to be supported.

    The Hand Book explanation is the only place screw sizes are mentioned and that refers to wall boxes:

    The exception to 314.27(A)(1) permits luminaires such as
    wall-bracket types or sconces weighing less than 6 lb to be
    supported by a device box using No. 6 or larger screws. De-
    vice boxes designed for the mounting of snap switches,
    receptacles, and other devices usually have 6-32 screws (No
    6 screws with 32 threads per inch). Generally, device boxes
    are not suitable for supporting other than lightweight wall-
    mounted luminaires.

    So my conclusion is that if a box isn't marked with a 50 Lb or more weight rating it can't be used to support a ceiling fixture. The mud ring has nothing to do with it and neither do the screws, however a box with a 50 Lb rating or better will have 8/32 or larger screws. 8/32 screws do not mean the box is 50 Lb rated though.

    -Hal

    Ya, I see what you mean, went back and re read 314.27 and nothing about screws. 314.23 talks about solid attachment to framing but no specifics. Back to seeking a solid answer.

  5. #35
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    What the code is saying is that all ceiling boxes intended to support a lighting fixture has to be at least 50# rated and if the location is such that there is the possibility of someone installing a ceiling fan, the box has to be fan rated.

    I'm just as guilty of this as anybody I guess. I can't tell you how many times I have done just as you describe with a 1900 bracket box and mud ring because I didn't think there would be any problem with the little ceiling fixture that weighed probably 2 pounds. Never had a problem with inspections either.

    -Hal

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