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I'm working on a small cabin. All black wires are run directly to lights. The white wires are run to the switches then lights... so each switch has only white wires.

Would the circuit still work? Why or why not?

It's the exact opposite of the black white being routed to the switch.

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ALL lights and switches are wired this way in the cabin. ALL walls are covered so getting to wiring will require ripped out walls.

If it's unsafe, couldn't we just hook up to power in the reverse order (so white is hot)? Would that work? Why or why not?

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    possible duplicate of Light switch setup using only white wire. Will it work?
    – Ecnerwal
    Aug 6, 2015 at 0:41
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    Instead of asking a new question when a question is closed, editing the original question is the "proper" procedure. Doing so will automatically move it to the "reopen" queue, so users can vote to reopen it.
    – Tester101
    Aug 6, 2015 at 3:10
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    When you say the black wires are run directly to the lights, you're saying that the black wires don't run through the switch boxes at all? Or are you saying that you have black, white and grounding conductors entering the switch box, and the black is connected straight through to the light, while the white is connected through the switch? If that's all it is, it's easy enough to just wire the neutral through and connect the black wires to the switch. Yes, this circuit will function. No, it is not safe for all the reasons listed here and in the answer to the earlier version of your question. Aug 6, 2015 at 4:36
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    Color codes are country-specific, I learned from my Chinese wife. Apparently green is "hot" in Yunnan... british plugs have brown and blue. So where is this cabin? Maybe it was built by someone expecting two totally different colors and found black/white/bare at the local store.
    – JDługosz
    Aug 6, 2015 at 5:29

3 Answers 3

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If the black wire in this situation is the ungrounded (hot) conductor, then it's a possible code violation and unsafe. If the black wire is the grounded (neutral) conductor, then it's a possible code violation but safe.

If the black wire is the ungrounded (hot) conductor, then you're switching the grounded (neutral) conductor. This is a code violation, and is not safe. In this situation, the fixture will always be energized. Touching the wrong part could deliver a fatal shock, despite the position of the switch.

If the white wire is the ungrounded (hot) conductor, then the circuit is wired in a "safe" manner. However, it's a possible code violation, depending on what code you follow. And could be confusing for anybody working on the wiring, which could lead to a potentially dangerous situation.

To determine what's going on, you'll have to take some measurements with a multimeter or voltmeter with the power on. Always use caution when working with wiring, especially live wiring.

  • Set the meter to measure voltage.
  • Touch one probe to the ground wire or terminal, and the other to an exposed portion of the black wire or a terminal where the black wire terminates.
  • Note the reading.
  • Touch one probe to the ground wire or terminal, and the other to an exposed portion of the white wire or a terminal where the white wire terminates.
  • Note the reading.

If you measured 120 volts (or whatever line voltage is) between the black and ground wires, then the black wire is the ungrounded (hot) conductor. If you measured 120 volts (or whatever line voltage is) between the white wire and ground, then the white wire is the ungrounded (hot) conductor.

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Whoever wired your cabin was an idiot -- this quite unsafe (it's a great way to find yourself doing the 60 cycle shuffle mid-lightbulb-change) is a clear NEC 404.2(B) violation:

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

(The exception is for dual-pole switches that switch hot and neutral at the same time, so it doesn't apply to your case.)

The "hot on white" case I'd be willing to accept in one or two cases, but for a house to be uniformly wired against Code like this would be rather, well, bizarre. A spot check of wiring to verify that white is indeed neutral (simply measure voltage between the white and bare wires) would be in order, though, yes.

Fixing this requires swapping the black and white wires both at the panel and the lights/outlets.

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    Not all "neutrals" are white wires, and not all white wires are "neutrals". While I agree that it's a code violation either way. The only way to know what's what, is to test.
    – Tester101
    Aug 6, 2015 at 1:45
  • @Tester101 -- his diagram makes it clear that whoever wired the place dun goofed. Aug 6, 2015 at 2:25
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    The diagram doesn't show how it connects in the panel, so there's no way to say that for sure based on the information.
    – Tester101
    Aug 6, 2015 at 2:27
  • I agree that you're probably right. But when it comes to crappy wiring, it's often dangerous to assume.
    – Tester101
    Aug 6, 2015 at 2:30
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If your sure you have no power at the switch, then whom ever did the electrical is switching the neutral and that was at one time (A LONG TIME AGO) okay but not anymore. The switching neutral it is not safe, even with the light switch off you still have power going to the light fixture and or socket, so when it comes time to change it you will need to find out which breaker it is on and turn it off. I have ran in to this about 3 times in my career and it only took the first time to know that it was not a safe thing to do. If you're going to leave it this way I would put a label on each switch to remind you of this. The BEST thing to do is to fix it and bring it up to code.

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