What is a traveler wire and how does it work?
I have been doing little bits of electrical lately, mostly wiring up basic single pole switches and outlets and I have been trying to learn more as I go.
When looking at some diagrams for 3 way switches there is a so called traveler wire.
What exactly is a traveler wire and how does it work/what does it do?
Question from user matt. at stackexchange
Answer:
A traveler, in the context of the US terms 3-way and 4-way switches, is a wire between switches which sometimes carries power and sometimes does not, depending on switch positions.
The specific configuration is that there are two travelers in a switched circuit. Each 3-way switch selects one or the other traveler wire. A 4-way switch - which is any additional switch between the two 3-way switches that are at the ends of the switched circuit - switches between two pairs of travelers at the same time.
In a way, a traveler is a variant of a switched hot, which is the output of an ordinary single switch and is also the final output of a circuits of 3-way, and optionally 4-way, switches. A little more specifically, with a circuit containing just two 3-way switches, the first switch (with a common hot wire) selects one traveler of the pair to be switched hot and other traveler is not connected. However, the second 3-way switch (with a common load or switched hot wire which goes to the switched light or other device) is then selecting between connecting the common wire to either the switched hot from the first switch (in which case the lights turn on) or to the not connected wire (in which case the lights turn off).
The following animated image from Wikimedia, Author en:User:Cburnett; light bulb by User:Fastfission licensed under Creative Commons Attribution-Share Alike 3.0 Unported shows it nicely:.
Note that black and red here have nothing to do with the actual wire colors (though black and red are very popular wire colors in US 3-way switch cables) but rather black means "no power" and red means "this wire is currently live".
The third wire can actually vary in different parts of the circuit. In the example diagram in the question, the left part is labeled "Travelers" but really is "Travelers and neutral". The right part is correctly labeled "Switched 120V and travelers". That diagram shows: Power -> Switch 1 -> Light -> Switch 2. It is a little simpler to wire either Power -> Switch 1 -> Switch 2 -> Light or Power -> Light -> Switch 1 -> Switch 2, but as long as it is properly done, these different wiring schemes are functionally identical and safe.
In an actual 3-way switch configuration, there are two possible color-coding schemes:.
Conduit.
If you are using wires in conduit (required in certain places, optional in most places) then white is always neutral and travelers can be any color you want except green (ground), yellow/green (ground), bare (ground), white (neutral), gray (neutral). They can be the same color (e.g., two black, two red, two yellow, etc.) or two different colors (e.g., black and red, yellow and blue, etc.) If there is a neutral wire then it is white or gray (usually white) and anything else except ground (hot, switched hot, etc.) is any of the same group of colors as travelers (black, red, yellow, blue, etc.) though for identification purposes it is definitely best to have the travelers a different color from any other non-neutral wires. For example, you could use the Harper color coding of hot = black, red = switched hot, yellow = travelers.
Cables.
Standard US 3-wire (plus ground) cables are only available in black/red/white. If there is a neutral then that gets white, otherwise "anything goes" but white should be marked with colored (but not green) tape to indicate that it is not neutral.
In certain cases you may need a 4-wire cable to include 2 travelers, neutral and either hot or switched hot. In that case neutral gets the white wire.
You can mark black, red and white wires with colored tape for identification. Using the Harper color scheme, you would put yellow tape on each end of each traveler. The travelers are functionally identical so they don't need to be distinguished. Then if you replace a 3-way switch you would always know which wires to connect where.
Answer from user manassehkatz-Moving 2 Codidact at stackexchange
I have been doing little bits of electrical lately, mostly wiring up basic single pole switches and outlets and I have been trying to learn more as I go.
When looking at some diagrams for 3 way switches there is a so called traveler wire.
What exactly is a traveler wire and how does it work/what does it do?
Question from user matt. at stackexchange
Answer:
A traveler, in the context of the US terms 3-way and 4-way switches, is a wire between switches which sometimes carries power and sometimes does not, depending on switch positions.
The specific configuration is that there are two travelers in a switched circuit. Each 3-way switch selects one or the other traveler wire. A 4-way switch - which is any additional switch between the two 3-way switches that are at the ends of the switched circuit - switches between two pairs of travelers at the same time.
In a way, a traveler is a variant of a switched hot, which is the output of an ordinary single switch and is also the final output of a circuits of 3-way, and optionally 4-way, switches. A little more specifically, with a circuit containing just two 3-way switches, the first switch (with a common hot wire) selects one traveler of the pair to be switched hot and other traveler is not connected. However, the second 3-way switch (with a common load or switched hot wire which goes to the switched light or other device) is then selecting between connecting the common wire to either the switched hot from the first switch (in which case the lights turn on) or to the not connected wire (in which case the lights turn off).
The following animated image from Wikimedia, Author en:User:Cburnett; light bulb by User:Fastfission licensed under Creative Commons Attribution-Share Alike 3.0 Unported shows it nicely:.
Note that black and red here have nothing to do with the actual wire colors (though black and red are very popular wire colors in US 3-way switch cables) but rather black means "no power" and red means "this wire is currently live".
The third wire can actually vary in different parts of the circuit. In the example diagram in the question, the left part is labeled "Travelers" but really is "Travelers and neutral". The right part is correctly labeled "Switched 120V and travelers". That diagram shows: Power -> Switch 1 -> Light -> Switch 2. It is a little simpler to wire either Power -> Switch 1 -> Switch 2 -> Light or Power -> Light -> Switch 1 -> Switch 2, but as long as it is properly done, these different wiring schemes are functionally identical and safe.
In an actual 3-way switch configuration, there are two possible color-coding schemes:.
Conduit.
If you are using wires in conduit (required in certain places, optional in most places) then white is always neutral and travelers can be any color you want except green (ground), yellow/green (ground), bare (ground), white (neutral), gray (neutral). They can be the same color (e.g., two black, two red, two yellow, etc.) or two different colors (e.g., black and red, yellow and blue, etc.) If there is a neutral wire then it is white or gray (usually white) and anything else except ground (hot, switched hot, etc.) is any of the same group of colors as travelers (black, red, yellow, blue, etc.) though for identification purposes it is definitely best to have the travelers a different color from any other non-neutral wires. For example, you could use the Harper color coding of hot = black, red = switched hot, yellow = travelers.
Cables.
Standard US 3-wire (plus ground) cables are only available in black/red/white. If there is a neutral then that gets white, otherwise "anything goes" but white should be marked with colored (but not green) tape to indicate that it is not neutral.
In certain cases you may need a 4-wire cable to include 2 travelers, neutral and either hot or switched hot. In that case neutral gets the white wire.
You can mark black, red and white wires with colored tape for identification. Using the Harper color scheme, you would put yellow tape on each end of each traveler. The travelers are functionally identical so they don't need to be distinguished. Then if you replace a 3-way switch you would always know which wires to connect where.
Answer from user manassehkatz-Moving 2 Codidact at stackexchange