I am in the process of hooking up 2 GE Z-wave light switches. I've hooked up multiple smart switches but ironically only one has needed neutrals (these 2). They are both going in a double gang box side by side. I had a few concerns: (BTW they both went to the same breaker switch)

  1. One of the wires was red going to the previous switch, I hooked it up like I would any normal hot wire and it worked...is it just another color for a hot wire? (They've always been black or grey in this house)

  2. Each switch required a neutral. I took both GE neutrals and tied it into the bundle of other neutrals (Which was like 2-3 wires in a wire nut). Sidenote: This made 4-5 wires in a wire nut...it fit fine but was a little tight. Is this ok? Is there a "max limit" or just whatever you can fit

  3. This is more of just me being paranoid but man with all the wires and how tight it gets in those gangboxes...it makes me feel like something is going to snap or come unhooked (even though I make sure everything is super tight). I guess if that was a problem though more houses would be burning down ha...just always makes me uneasy.

  • 4
    I'm not sure about the rest of your question but I do know that it is NOT permissible to stuff as many wires into a wire nut as will fit. If you look on the packaging for the wire nut, you should see a table with the allowable combinations of wires in that particular product.
    – jwh20
    Commented May 7, 2019 at 19:35
  • 1
    If I needed to split them up...how would I do that? IE: Can I actually split them up I guess is the question? This was just a wire nut in the wall it didn't come with any (It was a gray winged wire nut). I mean I would think whoever installed the wire nut would assume (or hope) that 2 neutrals might be added to the switches)
    – msmith1114
    Commented May 7, 2019 at 19:37
  • 1
    Wire nut capacity can get a bit complex, as it depends on the number and gauge of wires, and when mixed gauges are involved it may require resorting to small print sections of the documentation, or there may be a clear chart on the side of the box. If all wires are one gauge, it's generally easy to figure out.
    – Ecnerwal
    Commented May 7, 2019 at 20:29
  • 1
    Yeah im pretty sure these are all 14AWG since the fuse boxes are 15amp.
    – msmith1114
    Commented May 7, 2019 at 21:37
  • If you have many neutrals or grounds you would use a bar with a screw per wire (or modules interconnected). A wire nut is really not a good fit for larger wiring enclosures.
    – eckes
    Commented May 13, 2019 at 5:44

2 Answers 2


Wire nuts are color coded by size. A yellow nut would be fine for 3 wires, but at 5, you'll want to go to a red nut. If it won't stay together without tape, that is bad technique that will cause arcing and fire - fix the technique, don't tape it.

That "gray" wire you are seeing is actually black that is poorly tinted or faded. Actual Gray is a middle 50%-ish gray, and is legally reserved for neutral.

Hots can be any color but white, gray or green. However, in practice, using cable black is preferred for always-hot, and red is preferred for switched-hot. In practical practice, we are stuck with the standard colors that come in cable, but "red" for "switched-hot" often works out. Of course in a 3-way circuit, all bets are off...

As for box fill, there are rules on that. Count all grounds as 1 wire, all cable clamps as 1 wire, each "yoke" (switch, receptacle) as 2 wires, then count each non-ground wire entering the box. Do not count pigtails. Take that sum, multiply by 2.00 for 14 AWG ... or 2.25 for 12AWG ... And that is the number of cubic inches you need in the box. If the box is overfull, you need to fit a box extension of some kind.

  • What is the difference between unswitched and switched hot?
    – msmith1114
    Commented May 7, 2019 at 20:10
  • The side of the switch that goes to the light or device is the switched hot if the switch is on its hot if the switch is off its not. Many switches come with a red lead this is usually the output to the load the input is usually black. I think all the motion & dusk to dawn sensors I have installed have had a red wire to the load.
    – Ed Beal
    Commented May 7, 2019 at 20:33
  • 2
    Switched-hot is only energized when you want the light to be on. The switch has everything to do with that! Commented May 7, 2019 at 20:35
  • "As for box fill, there are rules on that." Interesting, I didn't know that. Do you have a link so I can read more on these formula?
    – bishop
    Commented May 8, 2019 at 1:44
  • 1
    @bishop the official source is the NEC (National Electric Code). Summaries are all over the place if you search "electric box fill". One such is currently here: jadelearning.com/blog/nec-2017-article-314-16 Commented Apr 6, 2021 at 18:28

Normally all the neutrals will get bundled together. Other answers:

  1. Red is a common color for hot wires in the US. Electrical cable comes with 2 wires or three wires (not including ground). The 2 wire kind is black and white. The three wire adds red. (This is the common, current convention and older wire might not follow). White is neutral, green or bare copper is safety ground, and other colors (blue, black, red, orange) can be hot.

  2. Yep, all the neutrals go together. When using an old wire nut, you can't easily tell how many wires it was designed for. Because of this and other reasons, you shouldn't use old wirenuts. Just consider them to be one-time use (within reason). When you buy new wire nuts, the packages will be labeled as to how many wires they are designed to fit. The common yellow wire nuts might only have a max of 3. Going up to the red nuts I think allows 5 wires, but again, that is brand specific so you just have to look at the label.

  3. Code actually specifies how many wires are allowed to be in a box. Search this site for "box fill calculations", we have several questions on it. Basically each wire uses up a certain number of "cubic inches" and once the box is "full", it won't support any more wires. Simple, example with made up numbers: Say you have a box whose interior is 14 cubic inches. Each wire might count as 2 cubic inches and the switch also counts as 2. So, you could have a max of 6 wires and one switch and the box would be full.

  • 2
    Good answer, but small correction: Grey is a neutral color, not a hot color (unless remarked).
    – Nate S.
    Commented May 7, 2019 at 19:47
  • Sounds like I should just go buy a bigger wire nut just in case. Since I think it was like 4-5 neutrals and was pretty damn tight. Im assuming it's all 14 gauge wire. For #3 I mean it's not like im putting anything extra in it? I'd assume a 2 gang box would account for having 2 switches with neutrals in them? I mean it fit...but as usual it's pretty darn tight..but I imagine most 2 gang boxes out there should support 2 smart switches that have neutrals?
    – msmith1114
    Commented May 7, 2019 at 19:52
  • @msmith1114, Extra wires that don't get used by the switches can pass through the box. If there are passthrough wires and two large smart switches or dimmers then it can get pretty tight. You may be able to install a deeper box if its a problem. You need to be able to fold the wires back into the box and have everything stay in place without screwing in the switches. If you rely on the screw pressure to push wires back into the box, it's probably too full.
    – JPhi1618
    Commented May 7, 2019 at 20:01
  • Ill fix it up when I get a new wire nut. It fit ok it was just the way it was arranged that made it annoying.
    – msmith1114
    Commented May 7, 2019 at 20:04
  • I'm not 100% sure, but I think larger than normal yokes might count as more than 2 wires. A standard toggle switch is not much larger than my thumb, while a GFCI receptacle (or smart switch) maxes out the height and width and extends much further back into the box, so it would make sense. Commented May 8, 2019 at 2:06

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