Replacing Old 3-way Switch

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Old 01-16-07, 09:35 AM
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Replacing Old 3-way Switch

I need to replace a 3-way switch. The terminals on the new switch are not in the same locations as those on the old. Here's what in the box: 1. Two black wires joined with a pigtail that connects to a terminal at one end of the switch body. Oddly, the pigtail connected to the two black wires is red. 2. Two white wires joined with a pigtail that connects to a terminal at the other end of the switch body. 3. A single red wire that connects to a third terminal that's next to where the white pigtail connects. None of the terminals are labeled.

Two of the terminals on the new switch are at one end of the switch body, on opposite sides. They are not labeled. The third is at the other end and is labeled "Common."

So how do I hook up the new switch?
 
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Old 01-16-07, 09:49 AM
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Yes, the terminals are labeled, you just don't know how to "read" the labels. Two of the screw terminals are the same color, and the common terminal is a different color.

There is nothing odd about a pigtail being a different color than the wires it is connected to.

What is unusual is that you have two sets of wires pigtailed to the switch. You don't typically see this with a three way setup, but sobe it.

If you forget how the wires were connected to the old switch and did not make make notes (which you should always do when removing wires) you can guess. There are only six ways to connect the three wires. Two of these ways will work fine, four of them will not work completely. Try until you succeed.

Of the two that work fine. one will have the switch oriented in the same manner as the old one, the other will have the switch upside down from the way it was previously oriented. By this I mean that the two three way switches will or will not work together in the same orientation as they previously did.
 
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Old 01-16-07, 10:03 AM
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Thanks for the info. So I assume the red wire (not the red pigtail) goes to the common terminal?
 
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Old 01-16-07, 10:20 AM
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Why would you assume that? I certainly would not make that assumption. I would go by how the wires were connected to the old switch.
 
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Old 01-16-07, 12:17 PM
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I suppose you're right, but that's the problem that brought me here in the first place - I can't correlate how the wires are on the old switch to how they should go on the new. I just looked again, and the old switch has no markings whatsoever on it and all three terminal screws are the same color (brass).

I'm not fond of trial and error when it comes to electricity but perhaps I'll have to give it a try. I'll check again too and make sure I've correctly identified what wires go where in the box.
 
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Old 01-18-07, 08:55 AM
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[QUOTE--- "Here's what in the box: 1. Two black wires joined with a pigtail that connects to a terminal at one end of the switch body. Oddly, the pigtail connected to the two black wires is red. 2. Two white wires joined with a pigtail that connects to a terminal at the other end of the switch body. 3. A single red wire that connects to a third terminal that's next to where the white pigtail connects."-----

It's POSSIBLE at the 1st 3WS ( 3WS#1 )there is a 2-wire ( Black & White ) "Feed-In" cable , and a 3-wire ( Black-Red-White) cable to the 2nd 3WS (3WS#2), with the with the Black & White wires of this cable connected as a "Feed-Out" circuit to 3WS#2, being connected to the Black & White wires of the 2-wire "Feed-In" cable. This connection is done when a "Feed" is needed at 3WS#2, and there is only 3-wires between 3WS#1 and 3WS#2. This connection is a Code violation.

The Red wire connects to the "C" terminal of the the first 3WS (3WS#1 ) and is switched to either the Black wire or the White wire of the "Feed-in" cable which are connected to the other 2 terminals of 3WS#1. Note there is a 120 volt "Feed" across these 2 terminals. The "far end" of the Red wire goes to the 2nd 3WS (3WS#2) ,where it connects one lead of the switch-controlled fixture.

This is how this connection operates--- We will presume there is a 2-wire cable, Black & White wires, between the fixture and the 3WS#2. The Black wire of this "fixture-lead" cable connects to the "C" terminal of 3WS#2 and the White wire connects to the Red wire from 3WS#1. The Black & White wires of the 3-wire cable from 3WS#1, which is a "Feed-In" circuit, 120 volts Black-to-White, connect to the other 2 terminals of 3WS#2.

These are the switching "combinations" in "Off-ON" sequence---

3WS#1, Red ("C" terminal ) to White , 3WS#2, Black ("C" terminal ) to White; --- fixture "Off"

3WS#1, Red to Black, 3WS#2 Black to White -- fixture "ON", 120 volts across Black & White wires to fixture

3WS#1, Red to Black, 3WS#2, Black to Black --- fixture "Off"

3WS#1 Red to White, 3WS#2 Black to Black--- fixture "On"
 
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Old 01-18-07, 10:11 AM
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Thanks for the detailed explanation. I think I'll print it out and try to correlate it to what's in the box.
 
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Old 01-18-07, 10:16 AM
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The dreaded Chicago (or California, or wherever) three way.

I'm not sure we should mention it here.
 
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