3-Way Switch = Blown Fuse. Did I create a short?

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  #1  
Old 10-29-12, 01:17 PM
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Thumbs down 3-Way Switch = Blown Fuse. Did I create a short?

Hey all,

I have a 3-way dimmer switch and 3-way toggle switch that operate a ceiling light in the dining room. I've found myself in a position where the switch now either 1: does nothing or 2: shorts and blows a fuse depending on how I have it wired.

Anyone have any ideas on what is happening, or have any good troubleshooting suggestions?

Background: I'm in an old building with existing wiring and replaced an old pendant. It's a simple process, but for whatever reason the new pendant did not operate. I reattached the old pendant, turned on the breaker, and blew a fuse. Thinking I killed the dimmer switch, I replaced it but still no go. I now suspect that I have a wire crossed somewhere.

I have drawn up what I've seen coming into each switch box and light fixture and two possible diagrams in the image below (also linked here: http://i8.photobucket.com/albums/a10/rcrhee/3-Way.gif). It looks like it should work, but I keep shorting or getting nothing at all no matter what configuration I try for the toggle and dimmer switch.

Here's some info to keep in mind when looking at the diagram:

B: black wire
R: red wire
W: white wire
WT: white wire marked with electrical tape (I assume this wire found at each switch box is the same wire)
The dimmer is the switch box near the living room
The toggle (I/O) is the switch box near the kitchen.

Both pendants are still operational (tested)
3-way switch is still good (tested via multimeter). No idea about the dimmer.



Thanks for reading! If you have any ideas or troubleshooting tips, I would really appreciate the help.



 
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  #2  
Old 10-29-12, 01:21 PM
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At the dimmer disconnect the dimer and connect one traveler to the common and test. Repeat with the other traveler.
 
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Old 10-29-12, 03:41 PM
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While we await your testing. There is no "up" and "down", so I refer only to your drawings. On the left switch, the "R" needs to go where the "WT" is and the "WT" needs to go where the "R" is. You have the "load" coming off a traveler screw in Scenario 1 and the "line" doing the same thing in scenario 2 for the right switch.
 
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Old 10-29-12, 11:00 PM
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Thanks for the suggestion to bypass each switch - I was able to successfully identify each wire by using your method. I bypassed the dimmer as advised and was able to get the black wire at the light fixture to be hot (I measured a 120V drop from the lead to the ground wire - not sure if that's the recommended method).

However, there is next to no drop (+/-30V) from the hot wire to the neutral wire at the light fixture, and I get no light when connecting the new fixture.

Am I hosed? FYI I believe that I can see the neutral wire from the light running through the switch receptacle nearest the kitchen (as shown in the first sketch).

Again, I really appreciate the help.

By the way, the dimmer (the switch shown on the left in the original post) is a Lutron and the common terminal is apparently in a weird location (lower right) - I tried to show it by making it dark on the first sketch. The two brass screws are on the lower left and upper right. With that in mind, is my schematic still messed up?

http://i8.photobucket.com/albums/a10...RICAL-TEST.gif


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Old 10-30-12, 04:39 AM
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As said before location has no meaning in reference to a switch. Function of the terminal is the way to identify each connection.

There should be a 2-conductor cable (black, white, ground) at one of the switches or at the light that measures 120 volts when disconnected from the circuit. Tell us where that cable is.light

However, there is next to no drop (+/-30V) from the hot wire to the neutral wire at the light fixture,
If you are using a digital meter you are only seeing induced voltage. Actual voltage is probably zero.
 
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Old 10-30-12, 10:29 AM
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Oh OK. The 2-conductor cable goes to the switch closest to the kitchen. The black wire from the cable is then capped with a red wire that bypasses the switch and heads straight to the dimmer. This red wire was confirmed 120V at the dimmer.

The schematic below lays out the basic location of everything. This is also the circuit I made last night that successfully got 120V to the black wire at the light receptacle (although still, no light).


http://i8.photobucket.com/albums/a10...2103008190.jpg


 
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Old 10-30-12, 10:37 AM
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Good diagram but you need to mark the terminals "T" for traveler and "C" for common. Can you give us a diagram of how it was originally connected using those designations.
 
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Old 10-30-12, 11:13 AM
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Sorry, I'm not as familiar with electrical symbols and nomenclature. The bolded terminals in all of the drawings are the common terminals, and the other terminals are traveler. I didn't bother showing the ground. I'll add C and T symbols where needed next time to eliminate any confusion.

Scenario 2 in the original sketch should be how it was originally wired. I am 100% positive about the wiring for the dimmer, but only 90% positive about the other switch - there were two identical black wires (one a traveler, one that goes to the lamp) that I didn't tag until after I removed the switch.

My best guess at this point is that the white wire at the light receptacle was somehow damaged when I first removed the pendant.
 
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Old 10-30-12, 11:30 AM
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Since it worked before that would be a good guess. It also happens when devices and fixtures are installed in a box the bare ground will touch a bare terminal.

but only 90% positive about the other switch
Key to all 3-way circuits is light hot to one common and power hot to other common.

I didn't bother showing the ground.
Good choice. I never show grounds in diagrams either. They aren't needed for understanding the circuit and add clutter.
 
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Old 11-01-12, 11:53 AM
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I have emerged victorious!

I nicked off some of the neutral wire insulation at the switch box to confirm that the break in the wire was in the ceiling. To my surprise, there was still no voltage drop between the hot and neutral wire, so I opened up another switch box on the opposite side of the wall and discovered that it had somehow jostled loose out of its connection. It must have been threatening to come undone for a while and then got jostled a bit when I first removed the old pendant.

I reattached the wire to a group of neutral wires and minus a burnt out dimmer, all is back to normal.

Thanks again for the help, I would not have been able to successfully locate the broken connection without the suggestion to bypass the dimmer.
 
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Old 11-01-12, 12:06 PM
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Glad you found the culprit. Thanks for letting us know you met him and victory is yours.
 
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