Sheetrock screws inside a PVC box to mount to a structure. Clarification needed!!

[Patpowers]

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 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 secure boxes by using brackets on the outside of the enclosure, or by using mounting holes in the back or in one or more sides 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. Mounting holes made in the field shall be approved.

This article has me under the impression that I can take a PVC Carlon Box and use Sheetrock screws to mount it to a structural member; ie 2x4.

It seems to imply that a mounting hole made in the field shall be approved as long as my screws are 1/4-in of the back or ends of the box.

However, I do not know of any PVC boxes that are listed or labeled to allow field made mounting holes. This would violate 110.3(B). Can I have clarification as to when a mounting hole made in the field would not violate the labeling and listing of an outlet box??

According to 110.3 (B) ;
(B) Installation and Use.

Equipment that is listed, labeled, or both shall be installed and used in accordance with any instructions included in the listing or labeling.

 

[Dennis Alwon]

Is this just a PVC junction box or a switch box. You can mount thru the back of the box. If you want to mount to the side of the studs then you need to screw the box all the way near the back of the box on the side wall.

 

[Dennis Alwon]

I missed the middle section of your post ...

Arlington makes boxes where you can mount to the side stud.

 

[Dennis Alwon]

I don't know the listing of the boxes but they may all be listed for mounting that way. It would be a weird rule otherwise. We used to just put screws in near the middle to front of the box and throw a dab of duct seal over it. Not code but there wasn't anything else.

I would like to see you get a screw in the side toward the back on a one gang box. Not easy..

 

[Patpowers]

I have some of those boxes. I do not use anything outside of the listing and labeling instructions. I especially love the 4-gang box they make. My argument to another electrician is that you can not originate a screw from inside a PVC box that would be mounting it in a way not approved by Carlon. He argues that the mounting holes made in the field would not be in the code if it wasn’t allowed. Regardless of making a mounting hole, it doesn’t say that the screw can originate from inside the box, but pass through the box. They are using new work boxes, cutting the nail mounts off and screwing them in like an old work box. I can’t see why the inspector passes this.

 

[infinity]

Since you're asking about PVC boxes this would apply not 314.23. So you can forget about drilling your own mounting holes.

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.

 

[Patpowers]

Thanks, I knew I read that somewhere. That’s what I get for not reading all the way through. And I’m the one to tell people not to make conclusions until you read the entire article. Need to take my own advice. Appreciate your time and diligence.

 

[retirede]

I wouldn’t use Sheetrock screws for anything but Sheetrock. The bugle head and brittleness make them inappropriate for general construction use.

 

[Dennis Alwon]

I wouldn’t use Sheetrock screws for anything but Sheetrock. The bugle head and brittleness make them inappropriate for general construction use.

I think they are fine for mounting a switch box. I wouldn't use it for mounting a large surface box but a small switch box is fine IMO

 

[tom baker]

I wouldn’t use Sheetrock screws for anything but Sheetrock. The bugle head and brittleness make them inappropriate for general construction use.

and sheetrock screws are brittle, easy to snap the head off, not good for loads. A better choice would be a pan head square drive tapping screw

 

[infinity]

IMO there is nothing wrong with sheetrock screws. If they're going to break it will happen during installation not after. There are videos on YouTube where they test them against other types of screws to debunk the myth that they're unsuitable.

 

[texie]

Since you're asking about PVC boxes this would apply not 314.23. So you can forget about drilling your own mounting holes.

Yep. AFAIK this has been in the code for a long time. Never seen anyone called on it though. I think there is good reason for it as an energized screw into wood could become a fire hazard over time. I for got what the fire guys call it. Pyro something combustion.

 

[Sea Nile]

"(1⁄4 in.) of the back or ends of the enclosure"

What is the definition of "ends" of the enclosure? I didn't think this was actually allowed at all in the code, I just know that I've seen it done and I've done it myself after my lead showed me. When I did it, I put electrical tape over the drywall screw head and around the device terminals.

I'm not endorsing using drywall screws, just following the lead of my lead as he is ultimately responsible for the residence passing inspection and has a better understanding of what the inspector will let slide