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I'm a bit confused about the wiring in a light switch that I changed. I am accustomed to seeing black (hot), white (neutral) and green/bare (ground).

This box has TWO black, a red, and a green. No white! So, I connected the two black together in a wire nut and connected the hot (black) wire on the switch to wire nut. Then I ran the red to the bottom screw. And the green to ground.

It works, but where is the neutral?

Ryan
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    you might want to look behind the switch box, often there's an untapped neutral running back there, especially on work done from ~1970-2000 (US)... the big disadvantage to your setup is using power-consuming switches like motion detectors, lighted switches, etc; without the neutral, you need a good conducting bulb in the socket, and LEDs are so efficient that this zombie current flow is enough to dimly flicker the light when off. with a dumb (plain toggle) switch, the results are the same as with a ganged neutral. – dandavis Oct 01 '17 at 21:50
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    Oh. That's even simpler then; the neutrals are pushed up into the back of the box, since the switch does not use them. – Harper - Reinstate Monica Oct 01 '17 at 22:20
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    in different terms: The two black are logically one wire; a splice on the black bus, with the red T'ing off the bus, and being switched before running to the light; that sounds right. – dandavis Oct 01 '17 at 22:33
  • So it sounds like my setup (connecting the two blacks) and wiring black to hot screw and red to neutral screw, would be fine? And by fine, I mean safe. – Ryan Oct 01 '17 at 23:23
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    @dandavis - Your comment is interesting because the reason I replaced the switch is that my LED lights were flickering every once in a while. So I purchased a simple on/off toggle (instead of a dimmer) and installed that. That's when I found the odd wiring. – Ryan Oct 01 '17 at 23:28
  • @Ryan: oh man; well too late now, but many newer (late 2016+) high-quality LED bulbs (ex: phillips, ge) have a dummy load that prevents flickering with such older switches/dimmers... – dandavis Oct 02 '17 at 05:31
  • You didn't mention another switch location but if there is then you have a three way switch loop which is a different wiring configuration. In that case I would say the two blacks are the travelers and the red is the hot feed or goes to the load. You still don't have a neutral though. – ArchonOSX Oct 02 '17 at 14:05
  • What country is this in? – StayOnTarget Nov 11 '18 at 11:44

3 Answers3

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Up until just a few years ago, the neutral was not required at a switch location.

A standard switch loop consisted of the hot feed to the switch, the switched return leg, and a ground wire. With non-metallic cable you have a black wire, a white wire, and a bare wire for ground. The National Electrical Code requires that the feed to the switch be the white wire re-identified as any other color but white or gray. So, with cable, you would then have a black wire, another black wire (a white wire with black tape on it since that is what the electrician carries all the time), and the bare ground wire.

If you had conduit running to the switch box then they would just pull two black wires for the switch loop, and a green for ground.

The Code now requires a neutral at most switch locations which is usually a white wire but could also be gray. This was not the case when your wiring was installed and is still not required if the installation uses conduit.

So, your switch box most likely had one black for a hot feed, another black for return to a load (fan, light etc.), and a red for return to aother load. And of course the green ground wire.

It will work the way you have it but one of the wires is extra.

Good luck!

ArchonOSX
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  • Thanks Archer. Is the way I have it considered "safe"? – Ryan Oct 01 '17 at 21:49
  • Well, with the two blacks connected together there is probably something that is now wired "on" all the time. Unless the other black wire was discontinued. There is no safety issue unless that device being on all the time causes a problem. – ArchonOSX Oct 01 '17 at 23:30
  • If you are using the neutral as a hot (with black tape wrapped on the ends), how can you also provide an actual neutral? Is that setup no longer allowed? – BlueRaja - Danny Pflughoeft Oct 02 '17 at 06:59
  • First question: you can't there will be no neutral at that switch location. Second question: the code now (I believe beginning in 2011) requires the neutral at most switch locations but there are also many exceptions, e.g. closets, non-habitable rooms, switches installed with conduit to allow for adding a neutral later, cable wiring with access to the backside of the wall. – ArchonOSX Oct 02 '17 at 11:16
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You're thinking colors are functions. Often, they are not.

On a switch loop, there is hot and switched-hot. There is no neutral.

Wiring methods

The primary wiring method used in homes is NM cable, or Romex. This cable is manufactured with ground, and two or more wires, in order of color: white, black, red, and blue. (And sometimes white with red stripe). You don't have any choice what colors come in Romex.. Because of that, you sometimes must use white as a hot.

A rare wiring method in homes is "loose wires in conduit". In this case, a pipe is laid between junction boxes, and individual wires are worked down the pipe. Electricians can choose any color of wire they please. I own 9 colors myself, because I like clarity. Also, they are not allowed to use white or gray as a hot wire in this wiring method.

Thinking about function

Really, most wires have a function.

  • Equipment Safety Ground of course
  • Neutral (the current return, and near ground potential).
  • Always-hot, a wire expected to be energized at all times.
  • Switched-hot, only hot when a switch is turned on, i.e. For a lamp.
  • Messengers, in 3-way switch circuits, a pair where one or the other is energized

Wouldn't it be nice to use different colors for all these?

Color codes

In most of the world, ground is green, green/yellow, yellow/green, or bare.

In North America, neutrals must be white or gray.

Wires which are hot or may be energized hot can be any other color. (Black brown red orange yellow etc.)

In conduit, I use black for always-hot, red for switched-hot, yellow for messengers, etc. In Romex cable, I tape the conductors to match the colors I want.

Color codes collide with the reality of Romex

A switch loop needs 2 wires: hot and switched-hot (ideally black and red). There is no neutral on a switch loop**. So it's 1999, you run out to the truck to grab your /2 red-black-ground Romex... and guess what. That doesn't exist. You don't have a choice what colors come in Romex.

So you are forced to run a switch loop with black and white. The two wires are still hot and switched-hot. This is legal if you mark the white wire black (or other appropriate color). However most people don't bother marking wires in switch loops. This is why you are accustomed to seeing white in switch loops.

So here, what you are seeing is correct wire colors in use: black and black are legal for hot and switched-hot. You may be in conduit where they are not allowed to remark white wires.

** Normally neutral is omitted entirely from a switch loop. The new smart switches do need neutral. Because of this, there has been a change in the Electrical Code. Nothing changes in the conduit wiring method, because it's fairly easy to add a neutral wire. However in the NM/Romex wiring method, adding a wire to a cable is impossible, so new installations are required to use cable with an extra wire for neutral. White is reserved for neutral, usually switched-hot is red.

Harper - Reinstate Monica
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  • From both answers, and OP post, shouldn't we concern ourselves with the solution he has, since he is asking if it is safe. It makes more sense that there is a white in the box - since he has two black and a single red. A signle green? Thats not a /2 or a /3 ...... (He never said he had conduit) – noybman Oct 01 '17 at 22:28
  • @noybman -- if he has MC cable, then he'll get greens; also, premade grounding pigtails use green wire. – ThreePhaseEel Oct 01 '17 at 22:52
  • Yes, there is definitely NO white. There are 2 black, 1 red, 1 green. I tied the two black together in a wire nut, and then put the black on the switch into the same wire nut. The red wire was connected to the neutral wire on the switch. And green connected to ground. – Ryan Oct 01 '17 at 23:01
  • If that was a neutral wire of a smart switch that you connected the red wire to it should not be connected through a load. It may still work but it is not right. – ArchonOSX Oct 01 '17 at 23:39
  • But no white? In the US? even MC? – noybman Oct 01 '17 at 23:39
  • @noybman -- a single green could also be explained by a "spur" conduit with a green in it, or by a grounding pigtail to the box. – ThreePhaseEel Oct 01 '17 at 23:55
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    @Ryan stop saying "neutral on the switch", there is no such thing as that. Switches don't get neutrals, they only want 2 wires: hot and switched-hot. Unless you're dealing with a smartswitch, those take neutrals but there is still a switched hot to account for. And red is a common switched-hot color, but it would never, ever, ever, ever be used for neutral. Ever. – Harper - Reinstate Monica Oct 02 '17 at 01:31
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What you have is a 3-way switch run. 2 blacks-power in and feed for light, red is the runner to/from other 3-way. Switch boxes do not use/need a neutral in them. If the installer use NMC, then he tapped black tape on the white. See NEC 404.2.

EricEB
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    What year is the book you are using as I read it neutrals are required in most cases for the last 2 code cycles – Ed Beal Nov 23 '18 at 02:46