Im looking to switch out an old rocker switch to a smart switch, but the wiring appears to be unconventional. Two black wires attached to the same screw, and a white wire, which I am trying to determing if it is neutral or not is attached to the bottom screw, and the ground on the opposite screw. Looking at the picture is there a way to see if this is a neutral wire, even though its connected to the switch.
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That ground wire is going to a green screw on the bottom of the switch, right?– JPhi1618Commented Oct 7, 2019 at 15:20
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Can you post a photo that clearly shows the back of this box, as well as a photo of the inside of the box for the light this switch controls?– ThreePhaseEelCommented Oct 7, 2019 at 22:54
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Yes it is. Thanks for the feedback. Helped alot– R4jenCommented Oct 7, 2019 at 23:07
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3 Answers
This is a switch loop. The unpainted whitee and black are always-hot and switched-hot.
You don't have neutral here. Further, the extra hot wire can't be on this switch.
Notice how the hot and switched-hot on this switch do not have any paint on them. They were added later, and are a switch loop to a different circuit. They were installed before NEC 2011 took effect, because that requires neutral on a switch loop. That would be the neutral you need and do not have.
The paint-speckled hot, however, is a dangerous interloper. It is stealing hot from this circuit, but returning neutral on another circuit, causing that neutral to be overloaded*.
Further, that invasion is totally needless. There are plenty of wires back there, so some must surely be hot for its own proper circuit. This needs to be fixed, by a pro if necessary.
Regardless, given the availability of power here, the switch loop might be "flipped", so the power at the lamp is not used by the lamp anymore, and the power comes out of this box. If that were done, the two extant wires would become switched-hot and neutral, and you would be able to install a smart switch here.
answered Oct 7, 2019 at 21:01
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When you have a white wire attached to a switch, it's pretty safe to assume that you are dealing with a "switch loop". There are several questions about that here, and lots of info in general. The white wire should be wrapped with a piece of black tape to show that it is a switched hot, but that is something that is often forgotten.
Also, when you have two wires connected to the same terminal (one in the screw and one in the push connector), that is just using the switch or outlet as a convenient way to connected two wires. Using the push connector and the screw is kind of frowned on, but it is done. A better option would be to bundle those black wires and run a single pigtail to the screw on the switch. Since you are installing a smart switch, it will probably have pigtails already, so these blacks will end up getting bundled "the right way".
If it's a neutral don't operate the switch. Like JPhil618 stated, it's a switch loop, not a neutral and should be taped to show it's a switched hot.
The picture doesn't show the back of the box clearly but it looks like there's a yellow wire nut back there but can't determine what wires go into it... (Don't ya love it when they prime your wires). If the wires going into that wire nut are white, there's a good chance they are your neutrals. good luck
