3 way switch for a single light mystery

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  #1  
Old 03-09-16, 12:21 PM
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3 way switch for a single light mystery

I am replacing a wall of switches that were installed in 1950 with z-wave switches for my home automation setup. One of the switches controls an outside pathway light and as far as I know is the only switch for the light. The strange thing is that it is a 3 way switch (or what looks like one).

Here is the setup from what I can see....

- I have a romex wire with black and white coming into the box
- I have confirmed that the white wire is connected to the outside light's white wire
- Unless my tracer isn't working correctly the black wire doesn't correspond to the black wire on the light - I can't figure out where it goes
- the black is connected to the traveler terminal on the switch
- the white is on the top of the switch across from the black traveler
- a hot black wire (always hot) is connected below the white on the switch

When I have all the wires disconnected and put a hot wire on the white that goes to the switch the light goes on.

At the outside light itself there is a single romex wire with a white and black connected to the light.

Anyone have any ideas for me to figure out what is going on here? I don't want to just cap off the black wire that is going to a mystery location and put the new switch on the white wire. Its also strange that i'd use a hot switch on a white wire.

Thanks!
 
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  #2  
Old 03-09-16, 12:52 PM
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I have a romex wire with black and white coming into the box
That would be cable. A wire is a single conductor.
- the black is connected to the traveler terminal on the switch
- the white is on the top of the switch across from the black traveler
- a hot black wire (always hot) is connected below the white on the switch
Are you saying there are three wires at the switch? If this is cable there has to be another white wire. Please post a picture. http://www.doityourself.com/forum/li...rt-images.html make the width of the picture 1000px or less.
a hot black wire (always hot) is connected below the white on the switch
If you used a non contact tester you don't actualy know if it is hot.
 
  #3  
Old 03-09-16, 01:55 PM
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here is a picture of the switch with the 2 wires that are leading to the romex cable. The white wire in the cable I've confirmed is connected to the white wire at the outside light. The black wire I can't seem to locate anywhere.

The picture is not showing a black hot wire that was connect at the bottom right (under the white) of the switch. I have it removed for now as i'm working on this but it appears to be a hot wire that was connected to each of the switches in the box. But yes - I used one of those "wands" that beeps if the wire is hot...

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Old 03-09-16, 03:29 PM
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You must always tell us about all the wiring and devices in the box so we can understand how it is wired. Your first post doesn't do that. I see probably three 2-conductor cables and one 3-conductor cable. Please give us a picture that shows the whole box. including where the cables come in and and both switches. Multiple pictures of the switches if needed to show how the wires are connected. Are there any wires wire nutted together in the box?
 
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Old 03-09-16, 03:58 PM
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Never mind. I didn't fully read the post.
 
  #6  
Old 03-09-16, 05:06 PM
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Hi - the wiring in the box is currently a mess since I have taken it all apart as I've been working on each switch. I've attached a picture here but not sure if that is going to help much. I have also attached a schematic that I drew up to document how everything was hooked together. Hopefully the schematic is clear enough for everyone to help me.

If it helps understand the diagram here are some points...

- there is 1 single pole switch (switch A)
- there are 3 individual 3-way switches (Switches B-D)
- there are 5 romex cables
Cable #1 - 3 wire with the red going to the light from the switch and the black going to an outlet in the room. The white connects to the light and the outlet. The black and white wires are connected to the panel via cable #2
Cable #2 - 3 wire with the red that connects between the 3 way switch and a light. The black and white go to the panel via the box near the light.
Cable #3 - 2 wire that connects the 3 way switch in this box with a 4 way switch at another location. The 4 way then connects to a 3 way before heading to the panel.
Cable #4 - 2 wire that connects to a 3 way in this box and then heads to my garage and connects to the other 3 way before heading to the light.

Cable #5 - 2 wire and I've confirmed the white connects to the outside light. The black wire I can't seem to locate where it goes.



I've got the rest of the box all figured out and working - its switch D that has been confused. I'm using a tracer tool to try and see where it goes but because its outside I can't trace it too far. This is all from the 50s so perhaps at one time my house had another light switch somewhere that was removed and the black line was capped off. But something doesn't seem right.

I can put 120V on the white wire on cable #5 and the light turns on - but I don't want to just ignore this black wire and cap it in the box. Seems dangerous to leave that without knowing what i'm disconnecting.

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  #7  
Old 03-09-16, 05:47 PM
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Based on your diagram there should have been several whites connected together because the diagram indicates there should be a 2-conductor cable that when disconnected shows hot to ground or neutral when measured with a multimeter (a non contact tester won't work). Is that correct?

Here is basically the wiring ignoring the other switches.

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Last edited by ray2047; 03-09-16 at 06:22 PM.
  #8  
Old 03-09-16, 06:00 PM
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There are only 2 white wires connected in the box - the whites from cables #1 and #2 are connected. Cable #2 goes to a junction box that I'm pretty sure is fed directly from the panel. Cable #1 has 3 wires with the red being used to control a lamp. The white and black on that line then goes to power an outlet.

The rest of the cables (#3-#5) have the white wires connected to 3 way switches directly.

I have a MM and have been using it to trace some of the wires. Not sure what I get your question about hot or neutral to ground. I know what those mean but not sure what you suggest I measure with the wires disconnected.

Would they have used a 3 way switch for a lamp that wouldn't have another switch location back in the day? I could just connect the white wire on cable #5 and control the light in question - but then i'd have to cap the black wire and something doesn't feel right about not knowing where that goes.
 
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Old 03-09-16, 06:16 PM
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Would they have used a 3 way switch for a lamp that wouldn't have another switch location back in the day?
May have been all they had. It will work with one wire on common and one on either traveler.
I could just connect the white wire on cable #5 and control the light in question - but then i'd have to cap the black wire and something doesn't feel right about not knowing where that goes.
Wrong if there is only two wires at the light (or like at the switch are there other wires you didn't mention).
At the switch:
  • White of cable from light to neutral of power in.
  • Black of power in to one side of the switch.
  • Black of cable to light to the other side of the switch
Please look at the diagram I posted again.

Attachment 63800

Not sure what I get your question about hot or neutral to ground. I know what those mean but not sure what you suggest I measure with the wires disconnected.
One cable is power in. According to your diagram the black of that cable powers switch A, C, and D. The white of that cable is neutral to the whites of the power out cables for A, C, D. You are looking for that power in cable by checking each two conductor cable to see which reads ~120v.
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  #10  
Old 03-10-16, 07:20 AM
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Very much appreciate the help Ray - I may be getting closer.

According to your diagram the black of that cable powers switch A, C, and D. The white of that cable is neutral to the whites of the power out cables for A, C, D. You are looking for that power in cable by checking each two conductor cable to see which reads ~120v.
Yep - I've used the multi-meter and also was able to physically trace the cables and confirmed that the power in cable is #2. The thing is...the power in does provide power out to A, C, and D. However, the neutral from cable #2 is NOT connected in any way to C or D.

Somewhere in my old house that has been renovated many times over the years there is either a hidden switch or a junction box that is connected to cable #5 and switch D. Cable #4 goes out to my barn so perhaps it shares a conduit with Cable #5 and the power line from my panel to the barn sub-panel?

If that is the case then perhaps at the base of the lamp there is a junction box that uses the neurtral from the barn power line for the neutral at the lamp. Cable #5 then uses the white wire for the switched hot. None of this explains what happens to the black line in Cable #5.

So...I have an old 3 way switch that we can't locate its companion switch. I do know the white of cable #5 goes to the lamp and the lamp must get neutral from somewhere.

Any more diagnostics you'd suggest to figure out how to safely replace switch D with a simple SPST switch. I can follow your diagram but i'd be left with the black wire of Cable #5 with nowhere to go....
 
  #11  
Old 03-10-16, 08:28 AM
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My solution in a situation like this is to disconnect and abandon in place then run a new circuit.
 
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