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

Switch Wiring Methods

Introduction to Switch Wiring

• If you only need one switch to control a light, use a single pole switch.
• If you need 2 switches to control a light, use two 3way switches.
• If you need three switches to control a light, use two 3ways with one 4way.
• If you still need more switches just add 4ways. Need six switches? Use two 3ways with four 4ways. Weather you use one 4way or more, the 4ways are always wired in between two 3ways..

Understanding Circuit Current Flow.

The more you understand how electricity finds its way through a circuit, the easier it will be to make complex switch wiring connections.

Consider how electricity flows through the wiring in a simple flashlight circuit. Tiny electrons leave the end of the batteries that are touching a wire and flow through the wire to a metal switch. When the switch is moved it slides this electrified piece of metal until it makes contact with another wire that allows the current to flow through the light bulb.

The electrons leave the light bulb where it contacts the other end of the batteries. The current passes through the 2 batteries and starts all over again, following the same path over and over until the switch is moved breaking the metal to metal contact and stopping the flow of electricity.

Remember this saying,

✘ From the battery power source, through the switch, through the light and back to the source.

All of this movement through wires that are insulated to keep the electrons contained within the wire.

Notice that the switch controls the power before it enters the light bulb.

If the switch was placed after the light you could still turn the light off but the light would be full of electrical pressure waiting to zap its way back to the power source through any path it can find.

Not a big deal in a flashlight but dangerous in house wiring if that path… is you.

Current flows through house wiring differently but the basic concept is the same;

✘ From the power source, through the switches, through the light and back to the power source.

Over and over through a big circular loop until a switch is turned off. Instead of a battery, the power source is the utility transformer and the path from this source to the switch is filled with other items like circuit breakers and meters, that can stop the flow of electrons as shown in the schematic below;

A Circuit From The Transformer To The Light

Compare this AC schematic of a light in a building with the DC flashlight schematic above.

Very similar to the flashlight circuit. Power leaves the hot side of the transformer and flows through the electrical meter, the main breaker, the circuit’s breaker and stops at the switch. When the switch is closed (as shown above) the current of electrons move through the (purple) switch blade, through the wire to the light, through the light’s filament wire to the neutral wire and back to the transformer. Then the current passes through the transformer and starts all over again, following the same path over and over until the switch is opened stopping the flow of electricity.

The switch is not the only thing that can turn the light off; if any part of this circular path is opened, or loses its connection, it will stop the flow of electricity. If the filament inside the light bulb breaks open the light goes off. If the breakers are flipped open (off) the light goes off.

If the meter or transformer or even the red wire nut on the neutral is removed the connection is opened and the light goes off.

What about florescent lamps, they don’t have a filament wire. How do the electrons pass through them? Florescent and neon lamps have a gas that electron pass through causing the gas to glow. If the glass on the lamp cracks the gas escapes and the path through the lamp is opened.

Wiring schematics leave out all the other items like breakers and transformers and simply show L1 and N as the power source.

The Direct Current or DC in a battery powered flashlight circuit flows in one direction. The electricity in a house is AC or alternating current which flows in 2 directions alternating back and forth. In the first 1/120th of a second, the current of electrons are flowing in one direction from the hot to the neutral and the next 1/120th of a second current flows in the opposite direction from the neutral to the hot. All of this completes one cycle. There are 60 cycles in a second or 60 hertz (50 in Europe). AC current works an electrical load with this back and forth flow just like a hand saw cuts wood on the down stroke and the up stroke.

Electricians refer to the current as flowing from the hot to the neutral, that first 1/120th of a second, frozen in time. The red arrows, in the schematic above, show the direction of current flow during that first split second moment in time.

Inside a switch.

It’s not that you have to see the inside of a switch but you must understand which terminals are being connected and/or disconnected when the switch toggle is moved. The purple and red lines shown here identify the moving metal blades inside the switch that make or break connections between terminal screws which are identified as black dots.

The black lines that continue off the drawing represent electrical wiring.

S1) Two single pole switches, or S1’s, are shown on the left.

When the S1 is open the light is off. When closed the light is on.

S3) Two 3ways or S3’s are shown in the center. Notice how the purple 3way switch blade pivots on the common terminal so that the common is always in contact with one of the 2 travelers and the travelers never connect together on the same switch. Of course we connect wires from the travelers on one S3 to the travelers on another S3 but here we are talking about the connections inside a 3way switch. And those connections inside never connect the travelers together.

☛ You could say that the only thing the 3way switch traveler terminals have in common… is the common.

(To determine if the light is on or off in the S3 or S4 drawing above requires a completed circuit drawing)

S4) At the right are two 4ways or S4’s and they really do say IN and OUT on the back of the switch. The S4’s shown here have the “IN’s” on the top but some designs have the IN’s on the side. Either way the inner metal blades (shown here in red and purple) always connect the IN’s to the OUT’s but never IN to IN or OUT to OUT. (There is no electrical connection between the red and purple blade where they cross in the top S4.)

So to review, when talking about the terminals on switches and there internal connections;

The “traveler” terminals never connect together.

The “IN” terminals never connect together.

The “OUT” terminals never connect together.

Reading wiring schematics.

Wiring schematics are like road maps showing the routes that current will follow as it passes through the electrical wiring with symbols representing switches, lights and other items. Schematics are also an installation guide explaining how connections are to be made for proper operation.

The difficult part is transferring schematic plans to the real world. It is easy to look at a schematic and see a line that connects terminal C to a light. The hard part is trying to figure out where, in the real and 3 dimensional world, the light is and where terminal C is and how you are going to connect the two together with a wire. When professional electricians are confused about some complex switch wiring, they will make a rough schematic sketch to help them figure it out.

Wiring schematics come in 2 different styles; Line diagrams and wiring schematics.

➳ Line Diagrams are a simplified view of a circuit showing current flow from left to right, with the hot at the left and the neutral at the right.

➳ Wiring Schematics are more complex drawings that try to represent the positions of circuit items as they would be in the real world.

Important Terms for Wiring Switches.

Common terminal. The only terminal screw on a 3 way switch that can connect (internally) to either of the 2 traveler screws. Identified with the letter “C” or the word “common” and normally with a black screw or a color different from the 2 terminal screws. There is no common on a 4 way switch or a single pole.

A Side Note;

The term “Common” refers to a common terminal screw only, not a wire because the wire connected to a common can be a hot feed or a switch leg.

The term “Traveler” can refer to a traveler terminal screw OR a traveler wire because only traveler wires should be connected to traveler terminals.

Load. A light or fan or other electrical items that consume electricity

✔Feed, Hot or Power. Electricians often use these 3 terms as if they have the same meaning but they do not. All 3 terms refer to wiring that can be turned off by a circuit breaker but NOT a switch;

Feed refers to both an unswitched hot and neutral that are “incoming” to provide electricity to a switch or receptacle. Imagine you are about to plug together 2 extension cords, the other end of the cord in your left hand is plugged into an outlet so it is feeding power to the 2nd cord in your right hand that is heading to your saw. Only the left hand cord is called the feed because it is “Incoming” The cord in your right hand is not called a feed until you walk over to the other end where your saw is and plug your saw into the feed.

Hot has 2 meanings 1) something that is electrified and 2)an unswitched wire or wiring that is connected to a circuit breaker. Hot is often used to describe a feed which has a hot and a neutral but in switch wiring the word Hot refers only to those wires that will be energized when the circuit breaker is on and stay on even if a switch is turned off. With our extension cord example, only the black wire in both cords would be called a Hot (if the cords were used in switch wiring)

Power means watts but in switch wiring it means an unswitched hot and a neutral that is

“incoming” or “outgoing”. Both extension cords would be called Power.

✔Traveler wires or “travelers”. A pair of wires of any color, except green, that connects 3way and 4way switches together at their traveler terminals. Electrical current will flow through one of the 2 traveler wires until one of the 3way or 4way switches are flipped.

Traveler terminals. A pair of same colored screws on a 3way or 4way switch where the traveler wires are connected. Electricity flows through the common terminal to only one of the traveler terminals until the switch is flipped then current flows through the common terminal to the other traveler terminal.

Pigtail. A 6 inch piece of wire with one end attached to a terminal screw on a switch and the other end connected to a group of wires. You might have 3 hot wires in a box that all need to tie together and your switch also needs a hot. All 3 will not fit under the switch terminal screw but one pigtail will. After the pigtail is added to the switch, all 4 (the 3 hots + the added pigtail) can be twisted together and capped with a wire nut.

Power source. The place where you will get your power (hot + neutral) to feed the switch. Normally a nearby receptacle or a smoke detector or a home run from the electrical panel.

Neutral is the wiring that electricity follows to return to the source. In switch wiring the neutral goes directly to the light, never to a switch. The neutral is a white wire that is paired with a hot. Not all white wires are neutral. A white wire used for a traveler is not a neutral but a switched hot. ✔Switched leg. The wire that connects the switch to the light and becomes energized when the switch is closed or flipped on.

Single Pole Switch or S1. A switch with 2 terminals. Only single poles say “ON” and “OFF” on the toggle.

3way Switch or S3. A switch with 3 terminals. 1 “common” terminal normally a black screw and 2 other traveler terminals both identified with the same color screws normally gold.

4way Switch or S4. A switch with 4 traveler terminals, 2 traveler terminals identified as “IN” both “IN’s” with the same color screws normally black and 2 traveler terminals identified as “OUT” both “OUT’s” the same color screws normally gold. The 2 traveler wires coming “in” from one 3way are connected to the 2 “IN” terminals. The 2 traveler wires going “out” to the other 3way (or another 4way) are connected to the 2 “OUT” terminals. A common mistake with 4ways is to take the 2 travelers coming in from ONE 3way and connect one wire to the “IN” and the other to the “OUT” You can connect both to “IN’s” or both to “OUT’s” but not one to “IN” and one to “OUT”

Key Points

✶ The code requires the metal frame on all switches to be grounded. Ground wires (not shown in this study) are twisted together along with a pigtail that is connected to the green ground screw on the switch.

✶ Switches are placed on the hot wire never the neutral wire.

✶ If it is too dark to read the “On” “Off” writing on the toggle, remember that the position of terminal screws on a single pole switch is always on the right side (your right as you face the wall with switch mounted in place) A single pole switch is right side up when it reads ON and the terminal screws are on the right side. It is upside down when it reads NO and the terminal screws are on the left side.

✶ A 3way switch can be used as a single pole by using only one traveler terminal and the common. Be sure that the switch is up when the light is on.

✶ On 3way and 4way switches, properly identify your terminals by looking at the color of the screws and reading the terminal labels. Don’t go by the terminal’s position. Different manufacturing designs can reposition the terminal locations. Compare the different terminal locations on a standard 3way with a decora style 3way.

✶ Inside a 3way switch, a connection is made from the common to 1 traverler. The 2 traveler terminals never connect together.

✶ Inside a 4way switch, a connection is made from 1 “IN” to 1 “OUT” and another connection is made from 1 “IN” to 1 “OUT” The 2 “IN” terminals never connect together and the 2 “OUT” terminals never connect together.

✶ There are no 4way dimmers. Plan your wiring in a way that a 3way ends up where a dimmer is planned.