Metallic electrical boxes

Discussion in 'Electrical Forum discussion & Blog' started by Marcus Waddell, Oct 7, 2019.

  1. Marcus Waddell

    Marcus Waddell Member

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    Hi all. Never used metallic boxes before but need to put some on my basement wall. With regular non metallic boxes there are holes for screws for your device (outlet or switch). But at my local home center the metallic boxes seem to lack the holes for attaching devices. Am I looking at the wrong type of box or is there something else I need to add on to the base box?
     
  2. Reach4

    Reach4 Well-Known Member

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    IL
    Start with a steel box[​IMG] and top it with a "mud ring". [​IMG]

    Those mud rings come in different depths and styles. The one above is a 1-gang that goes on a 4 inch box. You might do that to give you lots of room in the box, or because you want to be able to easily expand to 2 gangs later.
    [​IMG]

    Of course you can get 2 inch boxes and mud rings for those.

    The mud ring system lets you mount the box and choose an appropriate mud ring when you know how thick the plaster (mud) will be.

    You can also choose diecast aluminum weatherproof boxes for indoors. Nice and rugged but nice looking for surface mount. They don't use the mud ring system.
    [​IMG]
     
    Last edited: Oct 7, 2019
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  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    For surface mount, say in a basement concrete wall, the boxes are designed more for use with conduit between them, and are a bit different.

    FOr a one-gang, surface mount on a concrete wall, you could use something like this:
    View attachment 56339
    You'd need to buy clamps if you wanted to use cable versus tubing to power it up.

    Here's a two-gang one:
     

    Attached Files:

    Last edited: Oct 8, 2019
  5. Luke M

    Luke M New Member

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    Device attachment is provided by a cover plate. You get a cover that corresponds to the device(s) you want to mount.

    (I wouldn't use a mud ring on a surface mounted box).
     
  6. Reach4

    Reach4 Well-Known Member

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  7. WorthFlorida

    WorthFlorida Black Belly Whistling Ducks

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    Another way is mount a 1x3” or 1x4” to the concrete wall and screw the boxes and clamps into the wood. Sometimes this is a little easier and neater.
     
  8. Marcus Waddell

    Marcus Waddell Member

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    Would I just use a standard plastic cover for the above ^^^?

    Same question as above, for a metallic box, would I use a plastic cover like you do for regular PVC boxes throughout the rest of the house?
     
  9. Reach4

    Reach4 Well-Known Member

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    I think you could, but I think I would opt for metal. [​IMG] [​IMG] [​IMG][​IMG]
     
    Last edited: Oct 10, 2019 at 9:17 AM
  10. Marcus Waddell

    Marcus Waddell Member

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    If I were to use a mud ring (local big box only has the plain boxes to be used with mud rings). How do those work?
     
  11. Reach4

    Reach4 Well-Known Member

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    The mud ring attaches to the box at two corners. Then the switch or outlet screws to that mud ring. Then a plastic or metal cover goes over the duplex outlets or switch. I think the cover plate that Luke M suggested is like a zero-depth mud ring.

    Some big box stores have a retired electrician working there at times. Ask for that person if you don't see what you need to do the job.
     
    Last edited: Oct 10, 2019 at 11:43 AM
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  12. Marcus Waddell

    Marcus Waddell Member

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    Hey all, Reach4 helped my find some reasonably priced 3 gang electrical boxes. Can you help me double check the box fill? Three 20Amp independent circuits with a receptacle attached to each. By my calcs, that is 12 conductors (six in, six out), 1 set of ground wires, 6 fixtures (3 outlets *2 per) all with 12 gauge wire, no clamps, so 19*2.25 = 42.75.
     
  13. Highlander

    Highlander Member

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    Ontario
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