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I searched on this site and also google and couldn't find anything definitive on this.

My GC installed a single-gang outlet box behind the range for a NEMA 14-50R outlet. Most of the 14-50R outlets require a two gang box, but I found this one by Preferred Industries that says it works with a one-gang:

https://www.wilmar.com/Sku/35-57070/preferred-industries-3-pole-flush-mount-range-receptacle-straight-blade-4-wire-nema-14-50r-black-125250-volts-50-amp-076335241999

Is this ok? I know there is a way to calculate the fill requirements to get minimum cubic inches of an electrical box but am not sure how to do it for this type of outlet.

Here is a matching one-gang wall plate: https://www.wilmar.com/Sku/94-7470/flush-mount-1-gang-wallplate-white-078477836781-80528-w

  • How deep is the 1-gang box in question? – ThreePhaseEel Jul 25 '18 at 11:41
  • I'm pretty sure it won't fit just from looking at it because I just installed two of these outlets (one 30A one 50A) and I had to use a metal 4"x4" box which isn't really 1 OR 2 gang – The Evil Greebo Jul 25 '18 at 11:43
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    It's OK to use that device with a single gang cover plate, but that doesn't mean a single gang device box is allowable. You would use a single gang device ring on a 4x4 (or larger) box with this receptacle if you want to look at a single gang cover rather than a two gang. – batsplatsterson Dec 18 '19 at 14:23
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Box fill calculations say you need a volume of 5 in³ per AWG 6 conductor that lands in, or is spliced in the box, plus an allowance of 2 wire volumes (5 in³ each) for the receptacle itself. For a 14-50R receptacle, you will have 4 conductors, plus 2 for the receptacle, means that 30 in³ is required.

A 2g remodel box is only 25 in³, which is not legally large enough, but is exactly what we use for every Tesla charger we install. It's a bitch to squeeze the wires in and get the receptacle screwed down, so I recommend installing the whole assembly before mounting the box in the wall so you don't break the drywall with the force of the screwdriver pressing against the screw head.

I'm starting to reconsider this practice and may start using a 4"x2-1/8" square box, which is the minimum actually approved for this application...

  • Hello, and welcome to Home Improvement. Thanks for the answer; keep 'em coming. And, you should probably take our tour so you'll know how best to contribute here. – Daniel Griscom Dec 18 '19 at 12:23
  • I always use a self contained box for tesla/ev chargers... You can mount them over a single or double gang and bring wires in through the back if you aren't running conduit... amazon.com/Talon-LGP1S-Enclosed-Outdoor-Receptacle/dp/… – T Taylor Dec 18 '19 at 18:51
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Most 14-50 nema outlets look like they need a two gang... but they don't. They can fit in either. However we use a two gang for those behind a range typically. If you need more room and have the space behind the range, you can install an adapter box which is a metal 4 square box that would mount over the single gang box, you would need a metal industrial cover for it with a nema 14-50 size opening.

Such as this.... https://www.garvinindustries.com/electrical-junction-boxes/4-square-junction-boxes/2-1-8-in-deep-extension-rings/53171-sub

and this...

https://www.garvinindustries.com/covers-and-device-rings/4-square-covers-device-rings/industrial-covers/g1934

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