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I recently wired a new laundry room for a family member's renovation project. He already had the electrical materials on hand and all of his boxes attached to the studs, so I ended up installing the electric clothes dryer receptacle (NEMA 14-30 using 10/3 NM-B) in a "deep" 1-gang wall box (22 cu in).

I'm not used to seeing this type of setup done using anything smaller than a 2-gang box, but the receptacle's screw holes were configured for use with either 1-gang or 2-gang. This family member is also a flooring/walling contractor and insisted he'd seen them installed in 1-gangs in new construction on numerous occasions.

The box fill calculations I did show that a single termination of 10/3 + ground is more than fine in a 22 cu in. box, but the receptacle itself takes up an impressive amount of space in the box (not sure if this actually affects box fill requirements, though).

Are there any formal requirements for box size/type for the installation of these receptacles aside from normal box fill requirements?

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  • Was there any manufacturer documentation supplied with the receptacle?
    – Tester101
    Jun 26, 2015 at 15:19
  • Unfortunately not, and I can't find any online either. Here is a link to the product
    – mjohns
    Jun 26, 2015 at 15:42
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    The only special requirement is that a device like this counts are four conductors as opposed to two when calculating fill. This is because it has a two-gang yoke. ....See page 138 in this .pdf from ©Mike Holt. .... mikeholt.com/instructor2/img/product/pdf/… Jan 1, 2016 at 13:58
  • @SpeedyPetey Interesting info. Code references that I have not seen before. If I understand correctly, 10/3 plus ground in this scenario would count as 7 conductors? That puts the minimum box size at 22.5 cu in-- 0.5 larger than the box installed.
    – mjohns
    Jan 1, 2016 at 15:43
  • @mjohns, actually 8. Three conductors, one ground, four for the device. 20 cu/in total.... So that box is barely legal. Jan 1, 2016 at 15:46

1 Answer 1

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It's fine in a single gang box if it meets fill reqs and the screws line up without modification. Cover plates may be difficult to find, but they exist.

Use electrical tape over the terminal screws if it makes you feel good. I do when the box is metal.

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    On these receptacles the screws are recessed, so tape will do nothing at all. Jan 1, 2016 at 13:52
  • A volume marked extension ring is a good idea if you run into box fill issues and don't mind the outlet sticking out from the wall a bit. Apr 30, 2016 at 15:04

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