404.10 Mounting of Snap Switches. Box Mounted.
Code Change Summary: Code language was added to prohibit using fasteners such as sheetrock screws to attach a switch to a box.
A new switch will come from the factory with the proper attachment screws. Installing a box incorrectly can create the need for longer screws than what the switch came with. When a box is recessed too far behind the wall finish, sometimes the factory screws are not long enough to reach the mounting holes.
A common violation occurs when an installer uses longer screws with the wrong thread pitch, that were never intended to be used for switch mounting, such as sheetrock screws found on the job site that were dropped by the drywall crew. They may work but they are not code compliant.
Part of the issue is that 404.10(B) requires a flush-type snap switch to be installed so that the mounting yoke or strap of the switch is seated against the box. If using longer screws, it is likely that the mounting strap will never reach the box.
Now, specific code language in the 2014 NEC® requires the correct attachment screws to be used when attaching a switch to a box.
Below is a preview of the NEC®. See the actual NEC® text at NFPA.ORG for the complete code section. Once there, click on the “free access” tab and select the applicable year of NFPA 70 (National Electrical code).
2011 Code Language:
404.10(B) Box Mounted. Flush-type snap switches mounted in boxes that are set back of the finished surface as permitted in 314.20 shall be installed so that the extension plaster ears are seated against the surface. Flush-type snap switches mounted in boxes that are flush with the finished surface or project from it shall be installed so that the mounting yoke or strap of the switch is seated against the box.
2014 Code Language:
404.10(B) Box Mounted. Flush-type snap switches mounted in boxes that are set back of the finished surface as permitted in 314.20 shall be installed so that the extension plaster ears are seated against the surface. Flush-type snap switches mounted in boxes that are flush with the finished surface or project from it shall be installed so that the mounting yoke or strap of the switch is seated against the box. Screws used for the purpose of attaching a snap switch to a box shall be of the type provided with a listed snap switch, or shall be machine screws having 32 threads per inch or part of listed assemblies or systems, in accordance with the manufacturer's instructions.
