I have an existing switch that has a white wire at the top, a black wire at the bottom and I’m trying to replace it with a smart switch that requires 2 black ( hot ) wires and a white ( neutral ) wire how do I proceed ? There is an extra neutral wire coming from the bottom of the box as well this is a 4 switch box enter image description here

  • 1
    If there is a real neutral, not whites being hot.switch hot, in that box, and all are on the same breaker, you can use the neutral wires. There are a few buts and ifs. There are also a few smart switches that do not need neutral.
    – crip659
    Oct 27, 2023 at 14:22
  • 1
    There are also 'no neutral' smart switches now made by companies such as Lutron.
    – KMJ
    Oct 27, 2023 at 16:08
  • A larger photo, and/or multiple photos from different angles, may help us see better what's inside your box.
    – Matt S
    Oct 27, 2023 at 16:14
  • 1
    Chantal, wires with white insulation were formerly used not just as neutrals, but also as always hot or as switched hot in a so called switch loop to connect a switch to a light controlled by that switch. A mechanical switch does not need a neutral; a white wire attached to a switch is not a neutral but is one of the two hot wire that must be connected to a switch. Modern smart switches do require a neutral and so they will have to have a (white) neutral connected to the neutral contact. The two "hots" would be the line hot (from panel) and the switcched hot going to the light. Oct 27, 2023 at 17:42
  • 1
    Are the black and white wire going into the same cable and leaving the box? Oct 27, 2023 at 18:51

1 Answer 1


Presuming that the existing switch has worked as expected (turns the light on/off without tripping the breaker), you have a switch loop and no neutral in the box (for this circuit).

It's possible (but unlikely*) that the other neutral wires in this box are on the same breaker and could be used.

  • If the power to these other white wires goes off when you turn off the breaker that turns off the light, then you're in luck and you can proceed to wire up this switch.
    • Connect the black from this switch to one black of your new switch
    • Connect the white from this switch to the other black of your new one.
      • Note that some smart switches differentiate between "Live" and "load". If yours does (check the instructions and the labeling on the switch), you'll have to determine which wire on this switch (white or black) is the unswitched hot and connect it to the "Live" on the new switch, connecting the other to "Load".
    • Connect the white neutral from the new switch to the bundle of whites in the back of the box.
  • If the power remains on to the other wires in the box while the breaker turns off just this switch & light, then you do not have a neutral on this circuit that you can use. (Also, be very cautious of this situation as you may think you have all the power off to a box you're working in but make the painful to fatal discovery that you did not! If this is the case here, assume it's the case in other boxes you work in and double check everything before sticking your fingers in there.)
    • Take the new switch back to the store and get one that's labeled "No neutral required" and follow the instructions for wiring it.

*I can't imagine why an electrician would have wired power to the light, a switch loop to this box, then carried on unswitched power on the same circuit to the same box - it makes no sense to me, but I'm no licensed electrician. A homeowner doing DIY work may well have ended up in this situation, though, so who knows...

  • They not only need to be on the same circuit, but taking the same path back to the panel as the unswitched hot -- the chances of that are nil Oct 28, 2023 at 2:39

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.