2 wire and Light Fed S3

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   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.





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4 comments:

  1. I was doing an experiment in my basement to try and set up a makeshift 3way mounted on some wood planks so I could learn a bit about how a 3 way works. My power source is a 14-2 hanging loosely from my basement floor joists which is connected to the breaker via a 15 amp breaker. I didn't have any 12 or 14-3 wire bundle to wire my switches or light so I used 14-2 instead. My set up starts with the power entering the first box and connecting to the first switch, then to the light, then to the last switch. I used a white neutral and black hot that I spliced separately from a new spool of 14-2 to use as my travelers to the second switch, and ran the neutral from the existing 14-2 to my light between the two switches along with a ground. I used a black hot wire as my switch leg between the second switch and my light. This is just an experiment and in no way would I wire it this way behind drywall as a permanent fix. However, is this set up okay if I just want to test how a 3 way works? Every time I finish with it I disconnect my devices and shut off the breaker controlling the loose 14-2 rough in.

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  2. Yes this is OK but risky. Advanced Electricians understand the importance of keeping hot and neutral conductors close to each other because the opposing magnetic fields pulsating around them need to interact with each other.
    (Your travelers are hots and too distant from this circuit neutral)

    Please note that a white wire is not a neutral when used as a traveler, it is a switched hot with white insulation that should be identified with black tape or black marker near the switches to inform others it is not a neutral. ("I used a white neutral and black hot that I spliced separately from a new spool of 14-2 to use as my travelers")

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  3. Use a 15 amp breaker on #14 gauge wire and 15 or 20 amp on #12

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