I'm replacing a regular 2 plug outlet with a Leviton Z-Wave Outlet [Instructions].

The old outlet had 2 screws for black, 2 screws for white wires going into it. This new outlet only has 1 screw for black and 1 for white.

Both of these seem like possibly correct wirings to me but I wanted to confirm and see if one was better:

  1. Introduce a 3rd black pigtail wire, join the 3 blacks together with a wire nut, and only plug the 1 pigtail black wire into the outlet. Repeat for white (shown in picture).

  2. Don't introduce a 3rd black wire, but rather insert the 2 black wires into the top/bottom slots of the same screw. Repeat for the 2 white wires on the other side.

It would be much easier to do (2) especially since space in the box is tight, however I was concerned since the instructions say "either hold may be used" (emphasis mine).

So my questions are: a) Are both of these valid options? b) Is one a "better" solution than the other?

outlet instructions

  • Can you post a photo of the inside of the box you're installing this outlet into? Also, I take it this is an unswitched outlet, correct? Dec 11, 2016 at 19:02
  • Unswitched, correct. I have the wall closed up right now but it looked basically like this: graph.darren-criss.org/2016/03/20/…
    – philfreo
    Dec 11, 2016 at 20:46
  • Step 3 of the installation instructions appears to be inconsistent with the actual picture of side terminals used, which appears to be more like the rear terminals shown just to the right in step 3. The terminals in the actual picture appear designed to accept two conductors, one on each side of the screw.
    – Tyson
    Dec 11, 2016 at 22:02
  • Correct, the sides of the outlet look more like Step 3 [back wire picture] and less like Step 3 [side wire picture]. I figure they are just using that left picture as an example of screwing a wire around a screw. The question is, on the right side picture, is if you can+should include two wires since it has two "openings", even though it doesn't mention doing so.
    – philfreo
    Dec 11, 2016 at 23:11

1 Answer 1


I can't quite tell from the documentation above whether the receptacle is listed to take 2 wires via clamp. When it says "either side" does it imply "both"? If not, why have 2 slots? If listed, that is a fine solution.

Pigtailing is an elegant way to do that. However a pigtail requires more box fill. Aside from having to fit as a practical matter, it counts as an additional wire for the statutory rules on box fill.

I'm a big fan of stranded wire for its flexibility (i.e. in pigtails), and I'm irked that this receptacle is listed only for solid wire. That would have to be pigtailed to solid wire if you were working THHN in conduit with stranded wire.

  • Another way to ask the same question - is there actually some practical reason on why I shouldn't include both wires on each side? Since it seems like they'd be touching via the screw, how is that actually different than pigtailing with a 3rd wire? I have solid wires.
    – philfreo
    Dec 12, 2016 at 2:59
  • @philfreo pigtailing tends to be a better solution. If that outlet fails, the rest of the circuit still has power if the wires are pigtailed.
    – user4302
    Dec 12, 2016 at 5:39
  • 1
    @philfreo yes, they are conductive. However, if that little bit of metal overheats and breaks (say, because you are loading the circuit at capacity and it is not engineered for amount of use) that would be a failure. A failure that is unlikely to happen using wire nuts and the proper size wire.
    – user4302
    Dec 12, 2016 at 22:00
  • 1
    If the threads fail on a screw, and it comes loose, you could experience arcing in that outlet wiring box even if nothing is plugged into that outlet. However. Threads don't just fail like that. And manufacturer support sounds fine with it. I'd feel plenty comfortable to put two black wires under that brass screw, and two whites under the silver screw. Pigtails are nice.... if someone else does em. Not worth my time to do em myself personally, box fill limits aside. Dec 12, 2016 at 22:01
  • 1
    @philfreo sounds fine with me. It's clearly designed with 2 wires in mind; the only issue was the confusing "either" word in the docs. (which you do have to take seriously in case the design failed testing with 2 wires and they revised the docs as an expedient.) Dec 12, 2016 at 22:23

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