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I just opened my ceiling light to replace it with another mount. I see a white wire connected to 2 black wires, is that right?

The middle switch controls this ceiling light.

  • Do you know where the three cables in the open box go to? The answers below make sense for two, but you have three. – K.A Mar 17 at 15:59
  • Location would good since each country has different wiring codes – UKMonkey Mar 17 at 18:12
  • @K.A: The third cable almost certainly goes to the next light fixture on the same circuit. See the question I linked above for another very similar example (except with a switched outlet instead of a ceiling light). – Ilmari Karonen Mar 17 at 19:08
  • @K.A Black = hot, white = neutral, copper = ground, I assumed. I wired all three as they were in the old mount. However, the light is flickering a bit and I believe that's because my dimmer light switch is incompatible to the new LED lights. So, i'm in the process of replacing the switch. – konyak Mar 18 at 15:25
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The cable with the white wire that's connected to the two black wires is a switch loop:

switch loop

Normally wires with white insulation are used only for neutrals, but code makes an exception to allow for use of the white wire in a cable used as a switch loop as a hot rather than a neutral.

If you'll look closely in the drawing, the whites used as hots are wrapped with black tape to indicate they are being used as such. The wiring in the picture in the question lack this, which is a code violation. Of course the electricity can't see the tape so it's not intrinsically unsafe. However, it can be a hazard if someone working on the wiring makes a mistake because it's not labelled as clearly as it should be.

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    Should be noted more clearly in your post that a black piece of electrical tape should be wrapped near the end of the white wire in situations like this, so it's easily identified as a live wire. – stevieb Mar 17 at 14:39
  • This gives me a comfortable feeling that it's ok, but the diagram above does not look like my wiring setup. – konyak Mar 18 at 15:32
  • @konyak - you have one more cable in your box; it's just continuing the circuit - maybe for example to the light in the next room. – batsplatsterson Mar 18 at 20:54
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    @stevieb - your suggestion certainly can't hurt, I will add it. – batsplatsterson Mar 18 at 20:55
  • ++ The black tape identifier missing is all well and fine when everything is wired together per OP's photo, the problem arises after the wires have all been disconnected for a rewire. Neutral or hot? – stevieb Mar 18 at 21:17
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The fact that the white is with the blacks is very important. Most of what you need to know is in the positions of the existing wires; don't be in a hurry to tear it all apart, or you lose that critical info.

Color-coding is not by wire function, it's how cables are made.

That white has been reversed to be a hot. This is because it's in a switch loop, and no neutral is provided, so the neutral is re-tasked. (Today it's required to provide neutral). Because the neutral is re-tasked to be a hot, it must be marked with a few wraps of tape.

White is used for always-hot because another rule requires this. That's so when you're at the other end, it's easier to detect that the white Is hot, because it's always hot.

Once you have identified the neutral bundle(s) (all white), a white that's with mostly blacks is one of these. The fact this is in a lamp makes this most likely a switch loop.

Most likely its partner black is the switched-hot. The lamp will want this switched-hot, and actual neutral.

  • Perhaps this answer could also add the fact that a black piece of electrical tape should be wrapped around the end of a white-hot wire so that it's clearly identifiable, particularly after all wires are disconnected for work. (when I pretended to be an electrician back in the 90's in Ontario, Canada, this was code... don't know about now, but I digress). – stevieb Mar 18 at 21:25
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    @stevieb. It was in there, but the language was so obtuse it was hard to read. I cleaned it up. – Harper Mar 18 at 22:51
  • I'm pretty pedantic on this point. I'm only doing my own electrical nowadays so I'm unsure if one is still allowed to use white-live or not, but a label to identify should be used and enforced, even if the situation isn't even legally allowed any longer (regardless of locale). – stevieb Mar 19 at 0:20
  • Yes, marking wires is Code as of 2005 or so, before that it could be omitted "if the usage was obvious". This stack shows the problems with that. "White must be always-hot" has been Code for longer. It's still legal to convert white to a hot, which you would do for a water heater or EV charger. As of 2011 real neutral is required in switch loops, so you won't be marking white in a switch loop anymore; you have to run /3. – Harper Mar 19 at 0:28
  • Thank you for the full definition/explanation. /3 for switch loops; despite the cost differences, I comprehend the why, and I'll keep it in mind. – stevieb Mar 19 at 0:35

protected by Community Mar 17 at 21:37

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