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I installed a smart dimmer switch that requires a neutral wire. It was in the junction box with the two ends wire-capped together.

My switch didn't come with pigtail wires and I didn't have any extra wire lying around, so I couldn't do the recommended approach (install a third pigtail wire coming out of the neutral wirecap, and connect that to my switch's neutral terminal).

Instead, I just connected the two ends of the neutral wire by putting them into the same neutral terminal on the switch, under the same screw (see photo). The switch appears to work normally.

neutral  wiring  image to illustrate problem

But some quick Googling around says I should never put two wires into the same terminal. Why is this? Is there anything dangerous about my approach? To me it seems logically equivalent to the pigtail approach, i.e. the current still has the same paths to flow through. What am I missing?

EDIT: adding two photos of the back of my junction box since some people asked. I know it's a little hard to see, but there are two bundles of cords entering from two ports at the top of the junction box. The bundle on the left has three wires: black, white, and unshielded copper. The bundle on the right has four wires: black, red, white, and unshielded copper. Before I installed my new smart switch, the two white (neutral) wires were connected together with a wirecap. Thank you for the help!

junction box (overview) back of junction box (close up of entering wires)

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  • Can you post a photo looking into the back of the box please? I'm 95% sure you're right, but there is a 5% chance you are in a situation where Code prohibits this, and I can't rule that out without another photo Oct 5 '20 at 23:55
  • @ThreePhaseEel sorry, just saw this - I added two photos and a description of the junction box. I'm also just super curious about what this special situation is - would love to hear more!
    – HuntedC
    Oct 14 '20 at 21:06
  • You're cool, based on the photos (2 switches and thus 2 switched-hots, leaving only 1 way for always-hot to get in out of the 3 possible hot wires, so no chance for an issue). The situation where this'd be an issue is where a multi-wire branch circuit (2 hots on opposite legs sharing a neutral, thus "stacking" loads and letting folks economize on wire) is involved, because breaking the neutral unbalances the "stack", so we can't let removing a device do that under those circumstances Oct 15 '20 at 1:24
  • I see! Thanks so much for the explanation :)
    – HuntedC
    Oct 16 '20 at 1:26
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"Never" is a bit strong.

This is not a plain "screw terminal" where that would be true. This is a "screw and clamp" and appears to be designed to correctly hold 2 wires, so you are good. That extra bit of brass between the screw-head and the back plate is what makes the difference, along with the two grooves to hold wires in place.

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    Agreed never is a bit strong, except with the exception of where NEC 300.13(B) prohibits device connections where the removal of the device would interrupt continuity of a multi-wire branch circuit, which is a circuit where the neutral is used on multiple out of phase or opposing hot legs. We can't see if this situation exists in this j-box. Oct 6 '20 at 0:09
  • @NoSparksPlease sorry, just saw this - I added two photos and a description of the junction box. I'm not sure how to tell if my neutral is used on multiple out of phase legs, so it would be awesome if you could let me know!
    – HuntedC
    Oct 14 '20 at 21:08
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    @HuntedC To determine that, which I suspect is not the case here, check back at your breaker panel. If everything is installed properly (a big "if") then if a single breaker turns this circuit off then it is not an MWBC. If the breaker is part of a pair (two breakers with a handle connecting them) then it is an MWBC and the "don't break the neutral" issue applies. Oct 14 '20 at 21:17
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    @HuntedC I still can't see completely, but it appears you have 2 blacks and 1 red, that seems like the only possibility is one hot, so there wouldn't be a 300.13 violation. Oct 14 '20 at 23:45
  • Super helpful explanation, thank you both! Yes, single breaker so it sounds like this situation is good.
    – HuntedC
    Oct 16 '20 at 1:27

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