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Ever since I dove into the electrical side of things with my project, I've encountered a bunch of code restrictions. One thing that wouldn't surprise me if it was a violation of code is what I've done here:

modified electrical box

I did this because I have to install five of these things and don't want to disturb my neighbors. To get the screw to fit without breaking the tabs, I drilled through them with a 3/16" bit. The screw goes through with just enough snugness to hold on to the plastic with the threads, but not too snug that it bends or breaks the tabs. I did a test install on a stud and it holds really tight.

I did this because I couldn't find any screw-in receptacles at the hardware store that would allow me to bring the face of the box out 1 1/4" inches from the stud so that it would be flush against a double layer of 5/8" drywall.

Update: Crap. This is not going to work. I need to bring it out too far from the stud. When I go to install the drywall, the drywall is going to run into the mounting assembly. I need a box with the assembly in the back. I won't delete this question, though, in case it will help someone else who is not trying to add one million layers of drywall.

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3 Answers 3

up vote 14 down vote accepted

Here's another type of adjustable box that you can use. Just mount the box approximately where you want it and after you find the correct depth you can move it, even after drywall has been installed.

F101

Here's the cut sheet on it. Here.

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That is absolutely awesome. It's too bad no place around here sells them and that I already bought a different model to suit my needs. What I like about it is that you can install it after you've cut the holes for it, at least that's what it looks like. –  oscilatingcretin Jan 23 '12 at 1:05
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According to NEC 2008 314.43, these boxes may not be up to code. –  Tester101 Oct 5 '12 at 17:55
    
I agree, Tester, there's a risk of the box not meeting either 314.23(B)(1) -or- 314.43. Which is too bad. That's much nicer than the adjustable depth boxes that I've been using. –  Karl Katzke Oct 5 '12 at 22:27
    
@Tester101 The concern with screws is that the threads might abrade the wire insulation. Provided you screw the screws all the way in, you should be compliant. The problem is, sometimes you'll hit a drywall screw or nail while trying to mount the box, and then you either move the box or leave screws exposed. (This problem goes away in new work, but can be a real problem for old work, since "move the box" means "make the hole bigger and have fun patching".) –  Jeremy W. Sherman Oct 7 '12 at 2:55
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@JeremyW.Sherman The concern with screws inside a non-metallic box, is that the the box itself cannot be grounded. This means if the ungrounded conductor shorts to the screw, there is no safe path to ground (and the breaker may not trip). If the box was metal and the ungrounded conductor shorts to the screw, there is a path to ground through the box (and the breaker will trip). –  Tester101 Oct 7 '12 at 21:33

For the record, they make adjustable depth junction boxes like this.

enter image description here

They allow you to mount the box to a stud, and then adjust the depth at which the box sits on the stud.

They also make Old Work boxes, that can be connected directly to the drywall using clamping tabs.

enter image description here

The tabs pinch the drywall, and hold the box in place.

Here is what NEC 2008 says...

314.23 Supports. Enclosures within the scope of this article shall be supported in accordance with one or more of the provisions in 314.23(A) through (H).

(A) Surface Mounting. An enclosure mounted on a building or other surface shall be rigidly and securely fastened in place. If the surface does not provide rigid and secure support, additional support in accordance with other provisions of this section shall be provided.

(B) Structural Mounting. An enclosure supported from a structural member of a building or from grade shall be rigidly supported either directly or by using a metal, polymeric, or wood brace.

(1) Nails and Screws. Nails and screws, where used as a fastening means, shall be attached by using brackets on the outside of the enclosure, or they shall pass through the interior within 6 mm (1⁄4 in.) of the back or ends of the enclosure. Screws shall not be permitted to pass through the box unless exposed threads in the box are protected using approved means to avoid abrasion of conductor insulation.

(2) Braces. Metal braces shall be protected against corrosion and formed from metal that is not less than 0.51 mm (0.020 in.) thick uncoated. Wood braces shall have a cross section not less than nominal 25 mm × 50 mm (1 in. × 2 in.). Wood braces in wet locations shall be treated for the conditions. Polymeric braces shall be identified as being suitable for the use.

(C) Mounting in Finished Surfaces. An enclosure mounted in a finished surface shall be rigidly secured thereto by clamps, anchors, or fittings identified for the application.

(D) Suspended Ceilings. An enclosure mounted to structural or supporting elements of a suspended ceiling shall be not more than 1650 cm³ (100 in.³) in size and shall be securely fastened in place in accordance with either (D)(1) or (D)(2).

(1) Framing Members. An enclosure shall be fastened to the framing members by mechanical means such as bolts, screws, or rivets, or by the use of clips or other securing means identified for use with the type of ceiling framing member(s) and enclosure(s) employed. The framing members shall be adequately supported and securely fastened to each other and to the building structure.

(2) Support Wires. The installation shall comply with the provisions of 300.11(A). The enclosure shall be secured, using methods identified for the purpose, to ceiling support wire(s), including any additional support wire(s) installed for that purpose. Support wire(s) used for enclosure support shall be fastened at each end so as to be taut within the ceiling cavity.

(E) Raceway Supported Enclosure, Without Devices, Luminaires, or Lampholders. An enclosure that does not contain a device(s) other than splicing devices or support a luminaire(s), lampholder, or other equipment and is supported by entering raceways shall not exceed 1650 cm³ (100 in.³) in size. It shall have threaded entries or have hubs identified for the purpose. It shall be supported by two or more conduits threaded wrenchtight into the enclosure or hubs. Each conduit shall be secured within 900 mm (3 ft) of the enclosure, or within 450 mm (18 in.) of the enclosure if all conduit entries are on the same side. Exception: Rigid metal, intermediate metal, or rigid nonmetallic conduit or electrical metallic tubing shall be permitted to support a conduit body of any size, including a conduit body constructed with only one conduit entry, provided the trade size of the conduit body is not larger than the largest trade size of the conduit or electrical metallic tubing.

(F) Raceway-Supported Enclosures, with Devices, Luminaires, or Lampholders. An enclosure that contains a device(s), other than splicing devices, or supports a luminaire(s), lampholder, or other equipment and is supported by entering raceways shall not exceed 1650 cm³ (100 in.³) in size. It shall have threaded entries or have hubs identified for the purpose. It shall be supported by two or more conduits threaded wrenchtight into the enclosure or hubs. Each conduit shall be secured within 450 mm (18 in.) of the enclosure.

Exception No. 1: Rigid metal or intermediate metal conduit shall be permitted to support a conduit body of any size, including a conduit body constructed with only one conduit entry, provided the trade size of the conduit body is not larger than the largest trade size of the conduit.

Exception No. 2: An unbroken length(s) of rigid or intermediate metal conduit shall be permitted to support a box used for luminaire or lampholder support, or to support a wiring enclosure that is an integral part of a luminaire and used in lieu of a box in accordance with 300.15(B), where all of the following conditions are met:

(a) The conduit is securely fastened at a point so that the length of conduit beyond the last point of conduit support does not exceed 900 mm (3 ft).

(b) The unbroken conduit length before the last point of conduit support is 300 mm (12 in.) or greater, and that portion of the conduit is securely fastened at some point not less than 300 mm (12 in.) from its last point of support.

(c) Where accessible to unqualified persons, the luminaire or lampholder, measured to its lowest point, is at least 2.5 m (8 ft) above grade or standing area and at least 900 mm (3 ft) measured horizontally to the 2.5 m (8 ft) elevation from windows, doors, porches, fire escapes, or similar locations.

(d) A luminaire supported by a single conduit does not exceed 300 mm (12 in.) in any direction from the point of conduit entry.

(e) The weight supported by any single conduit does not exceed 9 kg (20 lb).(f) At the luminaire or lampholder end, the conduit(s) is threaded wrenchtight into the box, conduit body, or integral wiring enclosure, or into hubs identified for the purpose. Where a box or conduit body is used for support, the luminaire shall be secured directly to the box or conduit body, or through a threaded conduit nipple not over 75 mm (3 in.) long.

(G) Enclosures in Concrete or Masonry. An enclosure supported by embedment shall be identified as suitably protected from corrosion and securely embedded in concrete or masonry.

(H) Pendant Boxes. An enclosure supported by a pendant shall comply with 314.23(H)(1) or (H)(2).

(1) Flexible Cord. A box shall be supported from a multiconductor cord or cable in an approved manner that protects the conductors against strain, such as a strain-relief connector threaded into a box with a hub.

(2) Conduit. A box supporting lampholders or luminaires, or wiring enclosures within luminaires used in lieu of boxes in accordance with 300.15(B), shall be supported by rigid or intermediate metal conduit stems. For stems longer than 450 mm (18 in.), the stems shall be connected to the wiring system with flexible fittings suitable for the location. At the luminaire end, the conduit(s) shall be threaded wrench tight into the box or wiring enclosure, or into hubs identified for the purpose. Where supported by only a single conduit, the threaded joints shall be prevented from loosening by the use of setscrews or other effective means, or the luminaire, at any point, shall be at least 2.5 m (8 ft) above grade or standing area and at least 900 mm (3 ft) measured horizontally to the 2.5 m (8 ft) elevation from windows, doors, porches, fire escapes, or similar locations. A luminaire supported by a single conduit shall not exceed 300 mm (12 in.) in any horizontal direction from the point of conduit entry.

EDIT:

More useful information.

314.43 Nonmetallic Boxes. Provisions for supports or other mounting means for nonmetallic boxes shall be outside of the box, or the box shall be constructed so as to prevent contact between the conductors in the box and the supporting screws.

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I use the new work box on the wall I floated on furring channels. I use the adjustable ones on another wall that I soundproofed so that I could add one more layer of drywall if I needed to. The box I am talking about now will never have to be extended, so I want to mount a static box so I can save my remaining new work and adjustable boxes. My main question is does the modification I made to the nail-in box violate any known codes. –  oscilatingcretin Jan 22 '12 at 18:31
    
@oscilatingcretin I don't think this would be against code (though you may get some funny looks from the inspector), as long as the box is securely attached to the stud. –  Tester101 Jan 22 '12 at 18:35
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I'd be more concerned that the drilled out mounts aren't strong enough. –  DaveNay Jan 22 '12 at 18:41
    
@oscilatingcretin As MatthewPK points out in response to Skaperen's answer, you might instead be violating the box's listing, and since it would then be unlisted, you'd be using an unlisted box, which would be violating Code. Roundabout, but there you go. –  Jeremy W. Sherman Oct 7 '12 at 3:01
    
Those screw-wing old work boxes (the second photo above) work great with thick drywall. The screws that hold the wings are nice and long, so they accommodate deep walls. –  Jeremy W. Sherman Oct 7 '12 at 3:02

It is very plausible to have a box which allows nails but not screws. The general code requirement is that devices be installed as specified under their UL listing. The tabs that fit the nail or screw might not be thick enough (just guessing since I don't have the box or can see its UL listing report) to handle a screw. Screws too small would not hold it firmly and screws too large might rupture the tab. Because screws do have threads, there may not be a sufficient sweet size of screw that works just right. But I do know lots of boxes work fine with screws, as produce illustrations do show (here, and many other places). It's a matter of making sure you have a box rated to use screws (and, of course, use the size it is rated for).

I like lqlarry's box.

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+1, the UL Listing may require you to use specific fasteners and not to modify the mounting hardware. –  Matthew Oct 5 '12 at 19:58
    
@MatthewPK Is there anywhere you can actually view the UL documents without forking out cash? I know with enough clicks I've gotten to see TOC and scope, but never the full text. Without seeing them, I feel like we're shooting in the dark. –  Jeremy W. Sherman Oct 7 '12 at 2:59

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