Please help me figure out this crazy wiring!

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Old 09-03-13, 12:18 PM
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Please help me figure out this crazy wiring!

We have a mid-century ranch with some old wiring and some new wiring. This scenario deals with the pre-existing old wiring. We have two (potentially three-way) switches at either end of our hallway. One of the switches is a dimmer switch. The other is not. The switches control three separate ceiling light fixtures.

Current switch behavior: The switch at the entrance to the hallway, the dimmable one, will turn on the light. Then, we go to the end of the hall, and turn off the light. If we go back to the entrance and flip the dimmable switch, it won't turn on the light again. Moreover, if after flipping the dimmable switch in this way, we go back to the end of the hall and flip the other switch, it won't turn on the light again. It doesn't work like a normal 3-way switch would.

The only way we can control the lights is to either turn them on or off from the entrance dimmable switch, or if we turn it off at the other end, then we have to turn it back on from that end to keep the connection alive.

I am trying to convert the switches to motion sensing ones and bought a couple from Home Depot (Levitron, I think). When I open up the switchboxes, here is what I see:

Wiring for the dimmable switch: When I opened up the box, I found one cable (Cable A) with three wires coming out - black, white, and red. I also found a second cable (Cable B) in this box, with 1 black and 1 white wire. On top of that, the black wire from Cable A has been connected to the white wire from Cable B. In sum, the current switch has inserted into it, the black wire from Cable B (seems to be hot), the white and red wires from Cable A.

Wiring for the non-dimmable switch: Inside is a cable (Cable C) with three wires - black, white, and red - connected to the switch. The white wire seems to be hot. No secondary cable.

No ground: I did not find any ground wires with the old wiring (expected). The new motion sensing switches appear to require a ground wire for proper functioning, but I did not see any in the two switchboxes. I have read elsewhere, however, that there is a way to make the switches work without the ground wires.

That's it. Anybody have a clue about what's going on and what I can do???

Thanks in advance.
 
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  #2  
Old 09-03-13, 12:33 PM
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What I would do first is substitute a regular 3-way switch for the dimer just to eliminate one variable.

On top of that, the black wire from Cable A has been connected to the white wire from Cable B.
That sounds like you have a switch loop.
  • I would expect to see the black of the 3-conductor (Cable A) connected to the common terminal of the second switch (no dimmer switch).
  • At the place where the dimmer is currently located I would expect to see the black of the two conductor cable (cable B) connected to the common of the switch in that box.

Not sure about your dimmer, if it has three wires or even if it will work with a regular dimmer switch so the above is really based on two regular 3-way switches.
 
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Old 09-03-13, 12:52 PM
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Welcome to the forums!

Two things are going on here. One is that this pair of switches is wired with a 2-condustor switch loop from the light. That means that you don't have a neutral in either box, and that means that, if the motion sensors you bought require a neutral, they won't work.

The other is that the wires aren't connected properly.

Wiring for the dimmable switch: When I opened up the box, I found one cable (Cable A) with three wires coming out - black, white, and red. I also found a second cable (Cable B) in this box, with 1 black and 1 white wire. On top of that, the black wire from Cable A has been connected to the white wire from Cable B. In sum, the current switch has inserted into it, the black wire from Cable B (seems to be hot), the white and red wires from Cable A.
The power from the panel comes to one of the light fixtures. From that fixture, a 2-conductor cable is installed that takes the hot power to the switches on one wire and takes the switched power back to the lights on the other. That's the switch loop.

At the fixture, the hot power from the panel should have been connected to the white wire in the switch loop and that white wire should have been marked with electrical tape or permanent marker, in any color except gray or green, to show that it is carrying ungrounded current. It sounds like the proper connection was made but the marking was not. If so, the ungrounded, unswitched power is going through this box and connecting to the second switch first. You can test with an analog multimeter to verify this, but let's try straightening out the wiring first.

Every 3-way switch, dimmer, etc. has one common terminal and two traveler terminals. The common terminal should be identified by being a different color. Often it is black and the two traveler terminals are brass. The common terminal on one of a pair is connected to the hot feed, The common terminal on the other is connected to the feed wire for the load. The two traveler terminals on one switch are connected to the two traveler terminals on the other switch.

Wiring for the non-dimmable switch: Inside is a cable (Cable C) with three wires - black, white, and red - connected to the switch. The white wire seems to be hot. No secondary cable.
With the power off, terminate the black wire to the common terminal and the red and white wires to the two traveler terminals. Use the screw terminals, not any push-in holes. Remount the switch.

Wiring for the dimmable switch: Terminate the black wire going to the light (Cable B) to the common terminal. Terminate the red and white wires from Cable A to the two traveler terminals. Use the screw terminals, not any push-in holes. Remount the switch. Turn the power back on and see what you have.

If you now have the 3-way switch pair working properly we can move on to talking about ways to get motion sensors to work here.
 
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Old 09-03-13, 01:42 PM
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Nashkat1 - I will try that suggestion and report back. Thanks for the promptness, both of you.
 
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Old 09-03-13, 01:59 PM
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You're welcome. Ray and I said the same thing, BTW. I was just more long-winded.
 
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Old 09-03-13, 03:10 PM
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Dang, usually I'm the long winded one but lunch was in the oven.
 
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Old 09-04-13, 05:56 PM
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Awesomeness.

Wow. That totally got the lights to behave like they should. Thanks so much!!

I'm hopeful that you guys can also help with the next phase - putting in the motion sensing switches. If it helps, I got the Lutron Maestro MS-OPS2H-LA.

Thanks, again!!
 
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Old 09-04-13, 06:28 PM
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Does that switch require a neutral?
 
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Old 09-05-13, 08:07 AM
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I don't think so. Also, the model is actually MS-OPS5MH-LA. It has two black wires, a blue wire, a green wire, and a bare wire. There is also a short yellow wire that is not connected to the switch, but included in the package.
 
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Old 09-05-13, 09:31 AM
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They do not below show it used with a switch loop but I think it can be. But my brain needs brunch first so I post this for the pros.

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Old 09-06-13, 06:14 PM
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Those diagrams don't look like the installation instructions that I found for the Lutron MS-OPS5MH. Am I missing something?
 
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Old 09-06-13, 06:24 PM
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Maybe I found the wrong directions. Just ignore mine.
 
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Old 09-09-13, 09:17 AM
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Those are the right instructions, Nashkat. Let me know if you have any idea what I should do next. I'm still quite happy that the current switches are working now.
 

Last edited by Anuj Desai; 09-09-13 at 09:17 AM. Reason: Detail
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