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Hello I’m replacing a lighting fixture and I’m finding that both white wires are reading 120V. To be clear - it doesn’t matter where I place the red and black leads of my multimeter - I get 120V either way. The wires are both neutral wires. There are two hot wires that are directly connected together. This is not something I’ve come across before and was hoping someone might have an idea of what’s going on here? Any guidance would be greatly appreciated.

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    120V between what and what? Measuring AC, it doesn't matter which color meter leads are attached to what.
    – fixer1234
    Commented Dec 9, 2018 at 21:46
  • @fixer1234 measuring between the white wires shown in the image. It doesn’t matter which leads are connected to which wire.
    – Jordan
    Commented Dec 9, 2018 at 21:50
  • Oh I think I see what you’re saying - I’ll try the extension cord to ground method :) 🙏
    – Jordan
    Commented Dec 9, 2018 at 22:12
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    The wiring completes a loop. If power is present and you break any part of the loop, you will measure voltage across the break. It doesn't matter what color the wire is. So you can get voltage between black and white, or voltage between black and black or between white and white. And as Harper's answer describes, white can be used in switch loops.
    – fixer1234
    Commented Dec 9, 2018 at 22:26

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That's not neutral

Normally, wires cannot be re-tasked. But there is an exception in Code which allows white wires to be used as hot. The white wire must be marked with tape or paint. Prior to that, marking wasn't required "if the usage is obvious".

This is most often seen in switch loops, which is the usage here.

On both sides, black is always hot. One side's white is neutral back to supply. The other side's white is switched hot returning from the switch. We don't know which is which, but also, don't really need to. If in doubt, connect the lamp to one black/white pair. If the lamp lights, that pair is supply and that white is true neutral.

Lamps connect to switched hot, and neutral.

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    Its expected if the switch is on. There isn't really a way to tell which one is neutral unless you bring an extension cord up the ladder and measure between the extension cord's hot and the candidate neutral. It will read 120V if it is genuine neutral. It will read 0V or 240V if it's another hot.
    – Harper - Reinstate Monica
    Commented Dec 9, 2018 at 22:12
  • Yeah I’ve mostly been doing receptacles and light switches with fairly obvious wiring. I haven’t used a multimeter for this sort of thing just just a live wire detector. Forgot the fairly obvious thing about AC voltage .. it goes back and forth 🤦🏼‍♂️. I tested by using a ground from extension cord and have used red heat shrink to identify the neutral and black electrical tape to identify the hot wire for future travelers (no yellow wire pun intended).
    – Jordan
    Commented Dec 9, 2018 at 22:33
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    @Jordan Good idea, but it is illegal to mark the neutral a color other than white or gray. The legal thing to do is mark the switched-hot wire, and red is a preferred color for switched hot. That technique will be recognized by any competent electrician.
    – Harper - Reinstate Monica
    Commented Dec 9, 2018 at 23:56

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