There are two general styles of NEMA 14 receptacle in wide use -- one is the conventionally yoked style that is used with a separate junction box in flush mount applications, but can also be used in a suitable surface-mount j-box:

Leviton 278

while the other is a surface-mount-only style that comes with a specially-fitted metal junction box with a non-standard hole pattern and conduit knockouts in the back and bottom:

Leviton 55054

In a case where the grounding conductor for the circuit is a conduit, the former type of receptacle can be grounded in any way possible for a regular duplex NEMA 5 -- either through the yoke if permitted by Code, or by way of a bonding jumper from the receptacle ground screw to the box. However, the latter style of receptacle does not appear to have facilities in the box for a grounding jumper to be screwed to the box, and I am not sure if there is a "yoke" per se in that design that provides earthing continuity from the receptacle earth terminal to the box. This leaves me with the question: short of pulling a redundant ground wire through the EMT, how can I ground an integral-box-type NEMA 14 to a run of EMT? Or is the ground prong already set up to be electrically continuous to the backbox in such a receptacle design?

  • I can’t find a Leviton pdf that I remember from a few years ago, we had to prove as I remember. As such, I’m 99% certain that the yoke of the recessed model and the metal backplate/bottomplate of the surface mount model are electrically connected to the ground pin internally. We don’t stock anymore, it’s ordered per job only and I didn’t find one, new or used, in our shop to test with an ohm meter. My recollection is that the recessed model requires a pigtail ground screw to box since the mount screw does not have a self-grounding clip. – Tyson Apr 9 '18 at 19:12
  • BTW: leviton generally answers quick: leviton.com/en/support/contact-us/technical-support/… – Tyson Apr 9 '18 at 19:13

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