3 Way Switch Wiring Methods

► If the terms are new to you, go to the Key Page> http://s3switch.blogspot.com/p/key.html

► If you are trying to fix a 3 way circuit that is already wired but not working properly, go to the Fix Page> http://s3switch.blogspot.com/p/fix.html

► If you are about to pull the wiring for a 3 way switch and you just want a basic method then use this most simple 3way switch wiring method,  S3 Method #1.

       S3 Method #1     The Basic 3way          
This is the best and easiest method of wiring S3’s. If you only learn one S3 method, learn this one. To show the importance of the 6 terms described in the Key Page they are shown in red in the description of this method.

Rating  Excellent A+  ☺Most simple trouble free method.
Level  Intermediate
Also called a “Plain Jane 3way” or “Power at one end switch leg at the other”
Description
➣ A 2 wire (14/2, 12/2) feed is pulled from the nearest source of power, like a receptacle,

to the first 3way switch box. First, meaning the closest S3 to power.

   ➣ Then a 3 wire (14/3, 12/3) is run between switches from the first S3 to the second S3. This 3 wire is used for the travelers and the neutral.

   ➣ And finally a 2 wire switch leg is pulled from the second S3 to the nearest light and then to any other

lights that are supposed to come on with these switches.

Notes to the drawings below;

• The light is on in the Line Diagram. Current flows from L1 through the (purple) switch blade to the redtraveler wire through the 2nd switch blade to the black switch leg through the light to the neutral.
• The light is off in the Wiring Schematic because the second S3 (at the right) was flipped.
• The white wire (dashed line) in the 14/3 is used as a neutral and the neutral goes directly to the light.
• Notice that a hot and neutral are at the first 3way (at left) which could be tapped into to feed power to another nearby switch for a different light. This cannot be done at the 2nd 3way because the hot is switched and not energized all the time.

 https://docs.google.com/document/d/1MxgoNOrvlgXUzQnuy7MR5b6kvXH7pUIEwg_K4qvDFtA/pub

 

► Compare the Wiring Schematic with the photo;

This is a basic 3 way switch wiring method. It is the best and easiest method of wiring 3 way switches. The switches are shown in a horizontal position to make it easier to visualize. In houses, switches should always be mounted vertically (up and down). The only items not visible in the image are the switch blades, shown as purple in the wiring schematic, but hidden inside the switches. The letter “C” in the photo identifies the common terminals. Notice how one common has the black hot feed (L1) and the other common has the black switch leg to the light. The other 4 switch terminals are the traveler terminals interconnected with red and black travelers. The cord plug on the left illustrates power (L1 + N). If you plugged this into a hot receptacle the switches would function properly to control the light. To simplify the image and make it easier for you to visualize, the ground wire is left out and the boxes were laid sideways. Also the 14/3 between 3ways is missing its white sheathing and the wires are normally inserted into the back of the box.

When switch wiring becomes confusing to you, repeat our switch wiring motto;

✘ From the hot, through the switches, to the light and back on the neutral. 

Which means that you are going to create a wiring pathway that will allow electricity to flow ✘ from the hot feed, labeled L1 in the photo, ✘ through all the switches (L1⇒C⇒red wire ⇒C) and then ✘ to the light’s hot terminal and then connecting the light’s neutral terminal (gold screw⇒bulb filament wire⇒silver screw) and ✘ back to the neutral, the neutral in the feed labeled N in the photo. (white wire⇒red wire nut⇒white wire⇒red wire nut⇒white wire⇒N) All this creates a circular circuit.

If you have more than one light, you have a choice on where to connect your 2nd light. You can add additional lights by taping into the original light as shown here;

Or you can add additional lights by tapping into the switch leg at the switch as shown in the next method;

    S3 Method #1.1    A Basic 3way with 2 Switch Legs    

Rating  Excellent A+  ☺

Level   Intermediate
Also called a “Plain Jane 3way with 2 switch legs”

Description   Power at one end, 2 switch legs at the other. A 2nd light is connected to the switch leg at the switch instead of at the light.Notice that the black wires from lights connect to the common of the 2nd 3way. If they were connected to the first 3way’s common the lights would not turn off because L1 is hot all the time. So when you’re on a ladder pulling your 14/2 from the ceiling light down to your 3way, you have to run it to the 2nd 3way the one without L1.

But why run 2 switch legs to the switch instead from switch to light to light?
Answer; to save wire. In the wiring methods above, the white wire, contained in the 14/3, was used as a neutral. In the next 2 methods the white wire will be used as a traveler wire not a neutral. Travelers carry the hot feed from 3way switch to 3way switch.

   S3 Method #2   Dead End 3way With Extended Switch Leg

Rating  Above Average B ☺ Commonly used by professional electricians.

Level   Intermediate

Description   Power and switch leg at one end, dead end of a 3 wire at the other.

The line diagram looks the same as a Basic 3way…

…But the wiring schematic is very different. The switch leg and the feed are both pulled to the same box and then the black wire switch leg from the light is extended over to the common on the dead end 3way as shown here;

►   Compare the Wiring Schematic above with the photo below. #1 and #6 are the common terminals , L1 is the incoming hot feed;

Wiring diagrams and photo by Jim Morelli. You may copy for classroom instruction or personal use.

A “Dead End 3 way” switch wiring method. This method is commonly used by professional electricians. There are 2 variations of Dead End 3ways; extending the switch leg over to the common as shown in the photo above, or extending the hot over to the common as described below. You can copy this photo and any part of this site for classroom or individual use.

S3 Method #2.1    Dead End 3way With Extended Hot

Rating   Above Average B ☺ Commonly used by professional electricians

Level  Intermediate

Description   Power and switch leg at one end, dead end of a 3 wire at the other.

Again, the same line diagram…

..but different use of L1 and the switch leg from the light. The only change in wiring has to do with which common terminal will receive the hot wire and which common will receive the switch leg wire. In this method the hot is extended over to the dead end 3way’s common instead of the switch leg.

We just learned 2 different  methods of wiring a dead end 3way. Many electricians are unaware that there are 2 dead end methods. They think there is only one method, the one that they learned either extending the hot or extending the switch leg. Troubleshooting a bad light will be easier if you are aware that the common on the dead end 3way can be either;
➪ hot all the time (extended hot) OR
➪ a switched hot (extended switch leg).

   Look at both  “dead end” methods again in this side by side comparison.
Notice the different roles of the solid black wire in between the switches.
Method #2 extends the black switch leg from the light.
Method #2.1 extends the black hot L1.

Method 2

Method 2.1

This 3 wire is called 12/3 MC Cable. It has a metal jacket that requires a small red bushing to protect the wires from the sharp edge and also uses a special connector to attach it to a box. MC is more common in commercial buildings than residential. It also comes in 14 and 10 gauge. Photo courtesy http://www.lowes.com

S3 Method #2.2   Dead End 3way with Travelers at Light
Rating  Below average D – ☹
A 2 wire switch leg is the only connection that should be at the light yet this method requires cutting and reconnecting the travelers at the light. Notice the 2 red wire nuts on the travelers in the wiring schematic below and compare that with no wire nuts on travelers in the methods above. The extra connections in this method mean you have to; get a ladder, go up the ladder, raise your hands to the ceiling, strip, twist together, connect and cap the traveler wires. All of this is unnecessary in the previous methods.

Level   Advanced

Description   Power at one end, 3 wire run from first S3 to light and another 3 wire run from the light to the dead end S3 (at the right in the wiring schematic). All wires junction at the light box. Except for a change in wire color on one traveler, the line diagram looks the same as the previous method but the wiring schematic is totally different.

S3 Method #3    Radical 3way

Rating  Poor F – ☹ Not typical, not recommended.
A 4way cannot be added to this method. Only traveler wires should be on traveler terminals, yet this method has a traveler and a hot on the same terminal and, on another traveler terminal, both a traveler and the switch leg. Bad idea but shown here to help you recognize it if you ever have to work on it.

Level  Advanced
Also called a “California 3 way”

Description  Power and switch leg at one end, dead end of a 3 wire at the other. The hot and switch leg are extended over to the traveler terminals on the dead end 3way. The common terminals of each S3 are connected together and to nothing else. 2 traveler terminals, one from each S3, are connected together and connected to the hot. The 2nd set of traveler terminals are connected together and connected to the switch leg of the light. Power and switch leg have to be at one end for this method otherwise a 4th wire would be needed for the neutral.

Experienced electricians, unaware of the Radical method would have a hard time troubleshooting this mess. Normally, in all other methods, only one traveler wire is energized while the light is on but here all 3 wires are energized as shown in the “Line Diagram Light On ” above.

Another major problem with the Radical method is that a 4 way switch cannot be added into the travelers. The 2 diagrams below shows a 4 way added into the traveler wires and yet the light stays on even after the 4 way switch is flipped.

   S3 Method #4 Two Wire Traveler
Rating  Below average D ☹

There are 2 important concerns with 2 wire travelers;
1) There is a danger of overloading a neutral if 2 different circuits, on the same phase (service hot or transformer winding), are used. Be certain the 2 receptacles are on the same circuit.
2) This method can create unwanted impedance since the neutral or returning hot is not in the same 14/2 cable as it would be in a 14/3 cable the magnetic fields circulating around the hot or traveler are not canceled out by the opposing magnetic fields of those missing conductors. Try to keep the 2 wire traveler cable bundled close to the cable with the hot and neutral. Run the traveler 2 wire through the same holes as the receptacle feeder 2 wire instead of alone across the attic.

Level   Advanced
Description   Power at both ends, switch leg at one with a 2 wire (14/2 or 12/2) used as travelers. Since power (one hot and one neutral) is at both ends, the hot at one end is connected to the common while capping off the unused neutral and at the other end the neutral from the power feed is connected to the light’s neutral while capping off the unused hot.
Using 2 wire travelers is a common practice by construction electricians for 2 reasons;
1) To save money since 14/3 cost more per foot than 14/2
2) To save time. If they run out of 14/3 on the job, they can avoid a trip to the store by using the 2 wire traveler method.

Question; Why would you run a wire that you don’t even use?
Answer; The “cable” going from the receptacles to the switches contains 3 wires; a black, a white and a ground. These 3 wires are wrapped in a sheathing. Since only one wire and the ground are used, the other unused wire is capped off and saved for possible future use. Running only an individual wire without a ground or sheathing or conduit, is not permitted.
Notice that there is an unswitched hot and neutral at both switch boxes. In the future a person could add another receptacle by running a 2 wire cable from either switch box to the new receptacle.

S3 Method #5 Four Wire 3way

Rating  Below average D  ☹
As mentioned in method #4 above, there are 2 important concerns with 2 wire travelers;

1) There is a danger of overloading a neutral.
2) This method can create unwanted impedance
Level  Advanced
Description   Power at one end, switch leg at the other end with a 2 wire (14/2 or 12/2) used as travelers. Keep this method in mind if you don’t have any 3 wire with you.

S3 Method #5.1 Four Wire 3way with a light at both ends.
Rating   Average C
Level   Advanced
Description   Power at one end, switch leg at both ends with a 2 wire (14/2 or 12/2) used as travelers and a 2nd 2 wire used as a switch leg.

S3 Method #6 Light Fed 3way

Rating   Poor F – ☹
Unfortunately this method of connecting travelers inside the light box, instead of inside the switch box, makes it very difficult to access the traveler connections if any troubleshooting is required.

If you were given a choice to move your computer keyboard to one of 2 locations which would you choose;
1) Upside down, up on the ceiling by the light or…
2) On the wall by the switch.
It would be easier to work on your keyboard (and electrical connections) at a switch location rather than up on the ceiling. If you have a choice, choose the switch box for feed and traveler connections with only the switch leg connections at the light.
This method also creates an electrical hazard; beginners will think the wiring in the light box is dead when the light is switched off, but one traveler wire will still be hot unless the circuit breaker is turned off. If you miswire the travelers you might have to go back up a 12 foot ladder and take down a 50 pound chandelier to access the connections in the ceiling light box unaware that one of the wires will still be hot.
Level  Advanced  Also called “Power at the Light 3way” or “Commercial 3way”
Description   Power at the light’s box with 2 dead end 3ways. The hot is extended from the light’s box to one 3way and the switch leg is extended from the light’s box to the other 3way.

This article is a back up version of this updated article  http://s3switch.blogspot.com