Help replacing 2-pole switch with Z-Wave Dimmer

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  #1  
Old 05-19-19, 04:24 PM
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Help replacing single-pole switch with Z-Wave Dimmer

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I have a 3 gang box in my bathroom with single pole switches. From left to right, the switches are Sink Light Fixture, In-Ceiling Fan, Shower Light Fixture. I want to replace the left most switch (which goes to the sink light fixture) with a GE Z-Wave Dimmer, which requires a neutral. I was hoping someone could help me determine if this is possible.

Each switch only had two connections... (A) to (B), with (A) being at the top. Testing voltages against my sink faucet using a multimeter, (A) to faucet is just about 0vac, and (B) to faucet is 120vac. I'm confused because the the black and ground wires (which were cut back inside the romex, but I just exposed them for testing) seem to be floating with voltages all over the place.

So in short... I'm not sure if I have a neutral here. Is this a "switch loop" where all I have is line and load? Thanks for the help in advance.
 

Last edited by edict; 05-19-19 at 04:59 PM.
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  #2  
Old 05-19-19, 04:38 PM
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Welcome to the forums.

You have three separate switch loops there. That means for each switch you have an always live to the switch and a switched line back to the light or fan. That also means there is no neutral in that box which is needed for the Z wave switch. With that present wiring.... you cannot install a z wave switch there.
 
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Old 05-19-19, 04:58 PM
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Thanks PJmax. Would this mean that there is likely a neutral present at the light fixture, which an electrician could run over to my switch box?
 
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Old 05-19-19, 05:12 PM
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Yes.... the neutral would be at the fixture. He could run a three wire cable over carrying the neutral.
 
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Old 05-19-19, 05:19 PM
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Yes, the neutral is at the light but you can't by cide run one wire.* You will need to replace the 2-conductor cable (black, white) with a 3-conductor cab,e (black, red, white)

*All conductors must be in the same raceway or sheath so you can't run/add just one wire.
 
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Old 05-19-19, 05:22 PM
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Strange that it looks like they are using two Romex cables to complete a single switch loop. And then using only the white wires at that.
The light fixture you want to control will have a neutral there, so you could check that fixture's box to see if one of the unused black wires on these two cables is also available there. If so you could reallocate one of the white wires on the two cables for a neutral connection.
 
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Last edited by engr3000; 05-19-19 at 06:26 PM.
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Old 05-19-19, 05:41 PM
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Cool idea engr. I'll do a conductivity check.
 
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Old 05-19-19, 06:16 PM
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As pointed out by Ray you can't just run a neutral in a cable by itself without a hot wire that completes the circuit in the same cable (so that the magnetic fields cancel).

But instead of the normal 3- wire cable, if you have two 2-wire cables you could do the following:
Route hot and neutral from the light fixture box to the switch box using one of the two-wire cables. Connect black wire of cable to hot and white to neutral in the light fixture box. On the other end of this cable tie the black hot wire to one terminal on the switch. Tie the black wire of the other 2-wire cable to the other switch terminal. Use a wirenut to connect the white wires of the two cables together along with a third white pigtail wire which is a neutral for your "smart" switch.
This will route a switched hot and a neutral back to the light fixture box on the second cable. Then disconnect the existing neutral connection to the light fixture itself, and reconnect it to the white wire of the second cable coming back from the switch box. Then of course connect the switched hot black wire on the cable to the light fixture.
With this you would no longer have a switch loop, but instead have a neutral in each 2-wire cable that carries a current in the opposite direction as the hot or switched-hot wire in the same cable, as code requires.
 
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Last edited by engr3000; 05-19-19 at 08:20 PM.
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Old 05-19-19, 08:27 PM
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Good catch.

Now that I look there are 6) two wire cables.
Some interesting wiring indeed.
 
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Old 05-19-19, 09:15 PM
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So I took down the light fixture, and now I'm scratching my head a bit. First off, whoever put this in did pretty horrible work... but that aside, here's the story. The light fixture has two parts to it (one above sink mirror to the left, the other above medicine cabinet to the right).

Testing voltage and conductivity showed me the following:
1) The white wire is what's running to the switch box, and is also the neutral connection in the second part of the light fixture (above the medicine cabinet).
2) The right most black wire is the hot connection in the second part of the light fixture (above the medicine cabinet).
3) The left most black wire is power for the fixtures (it was tied to the other black wire to feed power to the second part of the fixture). When I turn my power back on at the breaker, this is the only wire with 120vac.

So it seems like the switch box is interrupting the circuit on the neutral side of the fixture? Am I interpreting wrongly? Also, after reading the responses here about wanting to maintain hot and neutral side by side, I'm concerned with the way only 1 wire is being used inside of these sheaths... It's hard to see from my pictures, but those 3 wires are each coming from a DIFFERENT 2-wire+ground cable, with the unused wires cut back in the sheath.

Thanks again for the help.
 
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Old 05-19-19, 10:54 PM
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I performed some more conductivity tests to figure out if I could make use of the unused wires in the switch box by re-arranging the circuitry like engr had outlined above. I found that although the white wire is connected to the switch box, it isn't the same 2-wire cable... its black wire is not connected to the switch box's black wire.

So then I decided to pull away the second part of the fixture above the medicine cabinet. What I've found is that inside the wall is where all these white neutrals are being tied together, and I found the cable that is running to the switch box (conductivity shows it is the same unused black wire). This is all making me think that power is actually sourced at this part of the fixture, and fed to the other part.

Going to leave the power off and sleep on this one...

By the way, when you see exposed tips, that's my doing (they had been cut back and taped off with electrical tape, but I pulled them out and stripped them for testing). I'm going to make sure I terminate them properly before I finish this project.
 
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Old 05-20-19, 11:41 AM
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Wire connections like the neutrals you mentioned must be made inside of an electrical box, not just behind some drywall. Also, as it sounds like you already know, you're not allowed to switch the neutral and leave the other wire energized.
 
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Old 05-20-19, 12:02 PM
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seems like the way it's set up now is pretty bad then. I'll try to see if I can rearrange the wiring so that I'm using both wires in the same sheath as hot and neutral, as they're intended to be used.
 
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Old 05-20-19, 01:10 PM
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I'm not happy with neutral being switched either... With the switch off, can't I still form a connection to ground or something else just by reaching my finger into the light socket?
 
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