Dead End and Radical S3

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Note, the following"Dead end" methods will have one of the 3 way switches missing a neutral which is now required at all switch locations. A 4 conductor (14/4 with ground or 12/4 wg)  can be used instead of the 3 conductor (14/3wg) to meet this code.

   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.

If the diagram is having trouble loading, here is another view

   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 1------------

------------ Method 2 -----------

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.

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