I am trying to upgrade my rocker switches to Smart Switches and ran into a problem identifying wires behind the old switches.

It seems that the old switch is connected with a ground and 2 white wires. There is a bundle of black wires capped and sitting inside the box. Everything I've read and have been told is that Neutrals are usually white and Blacks are hot.

What is going on with my wiring and are my hot and neutral colors just reversed? Or is the neutral connected to the switch and the hot capped? Or is there something else weird going on?

Thank you so much in advanced!

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Here is a photo of another box. I checked a few of them and they all seem to have the whites running to the switch and the blacks capped and left alone. Still perplexed. I will trace back the wires but could it be that they reversed all of the wire colors in the home?

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  • 15
    Who wired this thing? A harpsichordist? It was done exactly backwards. It cannot be used with smart switches until corrected. What's more, since it loks like the builder did it, the entire house could be full of defects just like this. Commented Dec 18, 2019 at 23:26
  • 6
    You can use a phase tester to see which of the wires is live. Don't trust the color code (but of course stick to the code when wiring it yourself). If you chose to fix the wiring you might need to look at at the whole house, every junction box and distribution panel. Get a pro to do that.
    – eckes
    Commented Dec 19, 2019 at 16:16
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    Your house was wired by someone incompetent to do the job, so it is very important that you assume nothing about the correctness of any subsystem until you have determined it for yourself. I have multiple times encountered wiring like this or worse and made the faulty assumption "well, this is wrong but surely this other thing is right..." and then gotten a surprise. Proceed with extreme caution and take notes as you go. Commented Dec 19, 2019 at 18:01
  • 5
    Also, despite what the top answer says here, the grounding is wrong in that box also. All ground wires need to be connected to each other. At the moment the ground wire for the left and centre devices is connected only to the switch, but not to the feeder ground from the incoming feed. No connection means no path to ground, so a fault in either of those two fixtures that energizes the ground will not trip the breaker but will leave your device box and switch shroud alive and well at 120V.
    – J...
    Commented Dec 19, 2019 at 19:49
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    What country is this? Colour conventions differ from one country to another. In USA, black is hot and white is neutral. But in Australia, and some other countries, black is always neutral, and other colours (including white) might be hot. Commented Dec 19, 2019 at 21:29

6 Answers 6


Your light switches are electrically upside down and backwards

Whoever wired your house clearly hadn't read, or decided to utterly ignore, NEC 404.2(B):

(B) Grounded Conductors. Switches or circuit breakers shall not disconnect the grounded conductor of a circuit.

As a result, you (or a friendly electrician, if you don't feel comfortable taking on a job this repetitive/long-winded yourself) need to switch things around so that the switches in your house have one screw pigtailed to the incoming always-hot black wire and the other screw connected to an outgoing black wire, with the white neutral wires all nutted together in the box, and the grounds all nutted together and pigtailed to all the switches. (If you run into a switch with more than 2 non-bare wires hooked to it, or with a white and a non-white/non-bare wire connected to it, stop and either consult an electrician or post a further question here, as that's a sign you either have a multi-way switch or a switch loop in play, which complicates things.)

What are the consequences?

While switching the neutral seems to work, as you have noticed by the fact all your lights seem to work fine, it's prohibited by the NEC due to the hazard it poses to clumsy lightbulb changers. You see, on an Edison (screw) base lamp socket, the "button" in the base is connected to the hot, and the screw-shell is connected to the neutral. This way, you won't get "bit" if you are trying to unscrew a bulb and accidentally make contact with the threaded metal part as you are doing so. However, it's possible for a bulb to bottom out in the socket with threads still exposed, so if you grab the bulb and get a finger on the threaded metal part, it's possible to get zapped through the bulb. Normally, this is only a hazard if the switch is on, and changing lightbulbs with the light switch on is a problem for several reasons, so it's normal common sense that one turns the light off before changing the bulb, no?

Well....bzzt! The wiring error in your house, with the neutrals to your lights switched, defeats that precaution, leaving the lightbulb and socket "live" and capable of shocking you, despite the switch being off! This is why switching the neutral has been prohibited by NEC 404.2(A) and (B) since the 1920s(!): it poses a clear shock hazard to anyone trying to use the switch as a disconnecting means to safely service a light fixture, or worse yet, a wired-in switched appliance!

How to figure out which wire is hot (for future reference)

The way a box like the first one can be decoded is using a multimeter; find whichever cable feeds the most switches with one of its wires, then take voltage measurements across all the wires in the cable. In a /2 cable like the OP's, one wire will measure ~120VAC to the other wires: this is the hot. We can then presume that the bare/green wire is a ground, and assume the other insulated wire is the neutral; checking to see if a ground actually is grounded is harder to do, though.

  • 4
    ...the grounds (which are thankfully fine) left alone Are they? They sure don't look fine to me. Each branch has its ground tied only to its respective switch - those grounds need to be tied together or there's no ground continuity in the electrical system. With a plastic box it doesn't even happen badly by accident.
    – J...
    Commented Dec 19, 2019 at 19:41
  • 1
    This answer makes a good point about switched neutrals, but should offer some way to identify if that is actually the case or if the neutral is simply misidentified with the black wire. The latter is still terrible but not nearly as unsafe. Commented Dec 19, 2019 at 21:20
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    @J... -- good catch, I missed that in the first box, thanks Commented Dec 20, 2019 at 0:23

30 years ago I used to find switched neutrals fairly often in houses built in the 60's. Might have been an older person, self built home. It works, but is against code since it exposes people working on the circuits to energized wires even when the light is off.

I would suggest you fix the switching problem with existing switches to verify function before retrofitting to smart switches.

You will need to get a tester and verify the black coming in the lower right corner is hot. If it is then take connections off all the switches, and connect all the whites together, connect the blacks leaving out the top as switchlegs (load connections), then pigtail that hot black to the line side of switches.

If you find the white coming in the bottom is hot then I would suggest it is time to call a seasoned professional to carefully correct the issues.

  • 1
    The decisive test is to measure the black from the bottom set, measure black to bare, if it is hot then you can visually trace the hot feed to the lights unswitched, and the white (the neutral) is switched. Commented Dec 19, 2019 at 2:07
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    Equally concerning though is the grounding wires. All grounding wires in a box must be connected to each other. And all switches/ outlets must have their ground connectors connected as well. I suspect this is a widespread problem. Ideally you should check every junction box for this, but at the very minimum check all of them with more than one switch/outlet. Commented Dec 19, 2019 at 15:51
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    However, for this box in particular: leave the coopers connected, but add a pigtail to each switch. Connect all whites together. connect the thee top blacks to one switch each (load side if the switch specifies one). Connect the bottom black to each switch with a pigtail. Once you have done that, you would then be in great shape to swap these out for smart switches. Commented Dec 19, 2019 at 15:53
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    everything has been working fine up to this point You need to be clear. Everything has been completely incorrect and unsafe up to this point. The occupants of the house have just been lucky so far. Don't assume your luck will hold forever!
    – Graham
    Commented Dec 19, 2019 at 21:01
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    @graham, absolutely. I had no idea the magnitude of the shit job going on back there. It is a top priority to remedy these switches throughout the house.
    – Tony
    Commented Dec 20, 2019 at 6:22

It definitely looks like someone got their wires crossed.. no pun intended. You have to straighten this mess out. Kill the breaker and start tracing the feed back to the main panel to determine where the problem started. Then you'll have to check each fixture that is controlled by the switches because they are all wrong too. Once you've determined the extent of the problem, you can start to correct it. Black wires should hot and switched, white should be neutrals. (Note that there are some situations where a white wire could be hot, but if so, it should have some black tape on it to identify it as hot.) Your ground wires in the box all need to be connected too. I wouldn't worry right now about the smart switches. Get everything corrected with the rocker switches, than deal with the smart switches

  • 2
    Good catch about the ground, I didn't notice that the cable leaving from the right side switch is the only grounded circuit. Commented Dec 19, 2019 at 0:17
  • Ground wires need to be connected from the wall with wire nut? then into each light switch?
    – Tony
    Commented Dec 19, 2019 at 1:06
  • @Tony If you have enough experience and are comfortable removing the cover on the main panel, please include a picture of the inside of it.
    – JACK
    Commented Dec 19, 2019 at 1:25
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    @Tony Test between uncapped black and uncapped white. Then test uncapped black to ground wire going into green wire nut, and then uncapped white to ground wire going into green wire nut.
    – JACK
    Commented Dec 19, 2019 at 2:07
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    @Tony based on those reading, black is the hot, and you're switching neutrals. The color codes are not reversed.
    – JACK
    Commented Dec 19, 2019 at 2:41

I would start with the electrical panel box to verify which wires are connected to the breakers ( should be black ) and which are connected to the neutral buss bar,( should be white ), then proceed with changing the switch wiring.

  • 2
    Hello, and welcome to Home Improvement. Thanks for the answer; keep 'em coming. And, props for taking our tour before posting; few newbies do. Commented Dec 19, 2019 at 13:34
  • Good point with checking the panel box (and house connection, too). It's possible that all the wiring is backwards. Commented Dec 20, 2019 at 12:54

This looks as if they are switching the neutral wire, which works but is dangerous to anyone who works on any fixtures controlled by those switches. Because you will always have power to the light. Have you checked inside your electrical panel to see how the wires are landed in there? Blacks should be landed in the breakers, white to the neutral bar and grounds to the ground bar, although on the main panel neutral and ground are common and sometimes share the same bar. Also you can get a plug checker and go around and see what the plug checker reads, such as hot neutral reverse or whatever it may be. But unless you are an electrician I wouldn't advise to start ripping apart the boxes and changing it all.


Your switch wired in one supply from consumer unit. You have 3 gang switch which supply with 4 individual wire with twin and earth cable. So the black wires that are Connected together are neutral and the white wire that are connected/capped are your live wire and the wire connected singly connected to switch are your switch live which coming from the light.

  • This might be true with UK wiring convention, but this is definitely not a UK installation (it uses wire nuts which is standard US practice but banned in the UK), and the color conventions are very different here -- here, black is always a hot color, and white is neutral.
    – Nate S.
    Commented Dec 20, 2019 at 22:10
  • Hello, and welcome to Home Improvement. Thanks for the answer, although it may not be applicable. And, you should probably take our tour so you'll know how best to contribute here. Commented Dec 20, 2019 at 22:16

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