The white is not a neutral. You have the incoming hot and neutral at the light. The hot at the light is fed to the switch via the white wire, so the two wire cable is a switch loop. The screws where the two black wires attach are your commons.

normel probably has analyzed it correctly, but the original description for Switch #1 leaves a lot to be desired. "Incoming" "outgoing" are not really that helpful. But the only red is in the 3-conductor cable so perhaps the 3-conductor cable and all it's conductors is considered to be "outgoing". If so, there is no mention of the connection for the white in the "outgoing" cable. I do have some other thoughts about possibilities, but more information would help. White(2) and white(3) would help identify the cable. Same for the black.

I will try to make this simple. One screw on a 3-way switch is bronze. That is the hot connection. Look at the wires coming into the box. There is a romex with two wires. Both of those are travelers regardless of color. There will be one wire by itself usually black. That wire connects to the bronze screw. The travelers connect to the two other screws and it does not matter which one goes where. Just remember, the hot wire will always be by itself. Once you understand which wires are which, you can wire 3-ways all day long as I have done at times.

Thanks for all the replies.

bus_driver: When I first wrote this inquiry, I wasn't too sure to use the "incoming" and "outgoing" nomenclature. I wasn't too how to describe it. Thanks for the hint.

I had looked at a few wiring diagrams and then looked at the number of cables coming into each receptacle box. I concluded it was a "You have the incoming hot and neutral at the light." -- as per normel's post.

texasredhead: I'll check for the colour of the wire on the bronze screw. In understand what you mean by "The travelers connect to the two other screws and it does not matter which one goes where.". I don't understand the sentences "There will be one wire by itself usually black." and "Just remember, the hot wire will always be by itself.". Do you mind clarifying the phrase "one wire by itself"?

Given the confusion, I should re-describe the question:

Hi,

I have a stairway light that is controlled by two three way switches at the top and bottom of my stairwell. Here is my wiring setup

Switch #1 has a two wire (black, white & ground) cable and a three wire cable (red, black, white & ground). I'm going to call these wires black(2), white(2) and red(3), black(3) and white(3), respectively.
-black(2) wire screwed to switch.
-white(2) wire is wire nutted to black(3) wire
-red(3) wire screwed to the switch

Switch #2 has one three wire cable (red, black, white & ground). I'm going to call these wires red(3), black(3) and white(3), respectively.
-red(3) wire screwed to switch
-black(3) wire screwed to switch
-white(3) wire screwed to switch

I'm not describing the ground wires as they are not pertinent for this question.

Everything works perfectly fine (nothing broken) right now and I have not unscrewed / disturbed any connections. I would like to replace the existing three way switches with newer three way switches.

Q: Given that this is a house built in 1964 to the Canadian electrical code, which wire is the common and which are the travellers?

It's really late right now and I'll turn off the power and check the colour of the wire on the bronze screws.

I am not familiar with the Canadian code. But look again at your description of switch #1. We are told that there are 5 distinct insulated conductors at that location. We are told how 4 of those are connected.

The very first response to this question is your answer. Connect one switch and test it. If it doesn't work(I think it will) then connect a different wire to the common of you new switch and try again. It will only take three tries to get it correct. Do not disconenct any wires that are connected togther and not connected to the switch. The only wires you need to deal are the three connected to the switch.
When you have one switch working then change the other one. It is much easier to troubleshoot one switch than two switches.

I'll stay with my original post: the black wires connect to your common terminals.

"Switch #2 has one three wire cable (red, black, and white) "

Red and black are travelers and the white is the hot to the light going THRU the first switch.

"Switch #1 has a two wire (black, white & ground) cable and a three wire cable (red, black, and white) "

White on two wire is hot feed from light fixture.
Black on two wire is hot return to the light itself and is connected to the white of the three wire.
Black and red from three wire are the travelers.

Stating it another way, we are not told by unix how white(3) is connected (or not) at Switch location #1. As described thus far by unix, this installation does not comply with the NEC and probably not with the Canadian code.

The colors of the wires is immaterial, it is how the wires enter the box. They may be black and white, white and red, whatever,but if they are in the same romex, they are travelers. The hot is by itself or may be pigtailed off another black or another color. Just remember, the hot is always by itself and is attached to the bronze screw. Maybe I don't understand what you are asking but there are only three connections on a 3-way switch.

He has the incoming hot and neutral at the light. The neutral connects to the light there.
He has a switch loop to switch #1 with the white carrying power to the switch box and the black carrying the switched power back to the light.
At switch #1, the black (switched power) is connected to the common screw. The hot (white) from the switch loop is connected to the black of the three conductor cable.
At switch #2 the black from the three conductor is connected to the common screw. The red and white in the three conductor are the travelers.
There is no "hot by itself"
And all of this assumes the white of the three conductor is connected to the third screw at switch #1.

Pretty simple to solve all this with a voltage tester. Make sure the light being controlled by the switches is OFF. Probe both switches. Only 1 screw terminal out of the 6 will be hot. That's your incoming hot from the power source. The other two wires at that switch are travellers. Note the traveller colors. Go to the other switch. Find the corresponding 2 colored travellers. The 3rd wire at that switch is the power out to the light.

If power comes to the light fixture box first, the only cable running to the switch locations would be a 3-conductor cable. 3 conductors for the 3 switch screws. Meets all NEC requirements. In this situation, if a neutral is desired at the switch locations for potential future use, a 4-conductor cable would be required per Article 300.3(B). If power enters at Switch #1 location, then the White(3) must be used for a 3-way circuit. Even if not important to anyone else, the information about White(3) is, in my opinion, important to properly understanding this existing installation.

Bigbird, you,ve got the right idea. Unfortunately, this is one of those 25 or 30 posts threads.

Actually three terminals will test hot when the light is off: the incoming hot, one traveler at that switch, and one traveler at the other switch, which will be the other end of the traveler wire from the previous switch.

Only 10 to go.

Normel is absolutely right. I should have added that you need to disconnect the 3 wires from the switch. Only one of the 3 will be hot. That's your power "in". If none of them show power, you are at the second switch that feeds the light. Repeat this test at the other switch if none of the wires shows power at the first switch. Sorry for forgetting that.

Since nobody asked, is one of the wires curled around the other two? If so, the wire with the curls goes to the dark colored screw.

bus_dirver: Sorry I forgot to mention white(3). At switch #1, white(3) is screwed to the switch.

All: Sorry for causing such a ruckus. It's getting late. I promise to check tomorrow and determine which wire is on the bronze screw. I'll check all three terminals and determine which are hot.

The original wiring is not to NEC requirements, as I stated earlier. In your installation, the power comes in to Switch#1 location via the 2-conductor cable. The White(2) is the neutral. It should be spliced to the White(3) for the neutral to the fixture. The Black(2) is the supply to Switch#1 and one must assume that it correctly is installed at the darker screw on Switch#1. The Black (3) and the Red(3) at Switch#1 should be used for the travelers. At the light fixture box, the Black for Switch#1 should be spliced to the White that goes to Switch#2- travelers. Red spliced to Red- travelers. Black at Switch#2 goes to the dark screw and Black from SW#2 is connected to the light fixture. This meets NEC requirements. Black cannot legally be used for a neutral in this situation. I know that all the other comments differ from mine regarding this installation. I take responsibility only for my comments.

Unix should post the wires at the light fixture.

Bus driver assumes the travelers pass through the light fixture.

If they do not the original post with the black and white wirenutted together is correct where the white can be used as hot but the black cannot be used as neutral.

My assumption is that this was a professionally done job, works correctly, and is properly installed.

Hendricus, please explain how a 3-conductor cable is present at each switch location and the conductors in that cable serve that fixture, but some of those conductors do not pass through the fixture box. Where do those conductors go? And how would the explanation you describe comply with NEC Article 300.3(B)? Where are the other accessible junction boxes that would be necessary? And why use such other boxes at all? Note that Black(2) is connected to the switch. From the original post:"-incoming black/hot screwed to switch". Please explain it so that I can understand my error.

2 #-2 wires at fixture: One is power in, other is a switch leg. PI nuetral is tied to fixture White. PI Black is tied to SW White(Hot). SW Black is tied to fixture Black.
At Three-way at the top of the stairs: SW Black is landed on the Common screw. Three wire Red and White are travellers. The SW White(Hot) is tied through the three wire Black. Three wire runs directly to the downstairs Three-way switch.
Three-way switch downstairs has Three wire Red and White as the travellers and Black(Hot) is the common.

The original post has two cables at one of the switch locations, one 2-conductor cable and one 3-conductor. The explanation posted Thu, Jan 17, 08 at 15:31 does not match that cable arrangement.

Sure it does: 2 conductor cable is switch loop from the fixture; 3 conductor cable is between the two switches. This was my explanation way back in post #2.

"Unix should post the wires at the light fixture." I strongly agree with this and fault myself for failing to mention that. That information will help clear the air quickly.

Here are the pictures, as requested:

The light at the bottom of the stairs looks like

There are three cables, all two conductors and the light itself. I will attempt to describe the connections. I'll call the top left cable as cable #1, the cable to its right cable #2, the bottom cable as cable #3.

-white(1), white(3), and white of light wire nutted.

-black(1), ***white(2)***, and black(3) wire nutted.

-black(2) and black of light wire nutted.

Switch #1 looks like:

(I took lots of pictures, but none of them were really "easy to understand", like the fixture picture.)

It looks like the bronze screw is in the middle and the adjacent screws are brass.

Switch #2 looks like:

It looks like the bronze screw is in the middle and the adjacent screws are brass.

As far as I know, the job was professionally done. It works correctly, inasmuch as both switches can turn on the light. Given the age of the fixture, the style of the fixture, and the layers of paint, I would guess that this was the original fixture when the house was built.

Does this help? I didn't do the voltmeter measurements, as I was confused by the instructions.

Here are my guesses (based on other people's comments):
1) At the light fixture, the supply cable is the bottom cable. Cable #3, in my description.
2) At the light fixture, the cable going to switch #1 is the top right cable, Cable #2.
3) At the light fixture, the cable going to feed other things is the top left cable, Cable #1.

4) Normel pretty much summed it up in:
"2 conductor cable is switch loop from the fixture; 3 conductor cable is between the two switches. This was my explanation way back in post #2." and

"The white is not a neutral. You have the incoming hot and neutral at the light. The hot at the light is fed to the switch via the white wire, so the two wire cable is a switch loop. The screws where the two black wires attach are your commons."

Texasredhead: The black wires are attached to each of the bronze screws.

So, am I close in my guesses?

Unfortunately, I have a followup question. I was looking at my book "Electrical code simplified house wiring guide, based on the 20th edition of the CEC and the BC admendments, 2006 to 2010" and saw this picture:

In this picture, the middle switch shows the white wire going to the common terminal.

Newbie/dummy question: Why is this diagram different from the way my setup is done? Am I missing something fundamental in my (mis)understanding?

Look at the middle switch and remove the white from the common, take the wire nut off the black and attach the 2 cable black to the common and wirenut the white to the black. Now it's the same as yours and works exactly the same.

28 and counting. Never ceases to amaze me how something so simple is made so complicated.

It wasn't complicated... he had the answer in post #2. Everyone else just mudddied the waters :).

And that makes 30. Good call Red!