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|Home 'Switch and Outlet Wiring Made Easy'|
3 Way Switch Circuits
Power Source and Fixture Feed at Same Switch [NEC 2011 compliant]
new rule 404.2 (C) Compliant)
For more information on this new rule read
2011 NEC New Rule 'Switch Connections'
Read the legal disclaimer page - click the legal link in the menu at bottom of page
For Preparation Instructions Click HERE
STEP 2 - Make the box openings (if a existing home)
STEP 3 - Feed / Route the wire cables.
STEP 4 -Mount / Install the Electrical Boxes (make sure the electrical boxes are secured as some fixtures are heavy and may require additional support) [The electrical box should not extend beyond the edge of the finished wall or ceiling so that the fixture can mount flush to the ceiling and the wall switch cover will mount flush - but it also should not be recessed too far into the wall or ceiling]; then feed the wire cables into the electrical boxes. Sometimes because of tight openings in existing homes, the wire cable may to be feed into the electrical box then the box put in position and secured.
STEP 5 - Connect the wires...
At the Fixture box...
At switch 1 box...
* a) using an insulated wire nut connect / join the white wire coming from fixture
+ the white wire coming from switch 2 + the white
wire coming from 'circuit power supply cable'.
At switch 2 box...
One cables entering this box coming from switch 1.
* a) connect the black wire coming from switch 1 to the
common screw of switch 2.
By electrical codes you MUST have at least 6 inches of wire in the electrical box itself, and also the wire must be able to reach at least 3 inches outside the box, it can fail an electrical inspection if the required min. wire length is not met. You may have the wires a bit longer (within reason) but they cannot be shorter. Also see the note on box fill further down in this article.
If the fixture has screw type connectors, the switched ungrounded conductor (hot) is connected to the brass color screw, and the grounded conductor (neutral) is connected to the silver color screw. If it has black and white wires coming from fixture, then just connect black to black and white to white. Use wire nuts of the correct size to join wires together.
The wire cable running between switch 1 and switch 2 has 4 wires in it - black / red / blue / white (plus the bare equipment grounding wire). There is some notes in the article called '2011 NEC New Rule 'switch connections' regarding 4 wire cables.
What is not shown in the drawings to avoid confusion, is that each wire cable also has a bare equipment grounding wire included. This wire is connected to a equipment grounding screw in each electrical box (if the box is metal), joined either through the equipment grounding screws in the box itself or via a wire nut to the bare wire of the next cable entering / exiting the box, it is also connected to any equipment grounding screw (if there is one) on the switch itself, as well as any equipment grounding screw at the fixture (green wires that attach to the fixture are grounds). Now if using a plastic box, it is made of a material that is non conductive, however some plastic boxes have a metal strip inside that can still be used to connect equipment grounding wires, in the event that it does not use wire nuts to join the bare grounding wires together. The equipment grounding wire (bare in most cables) must be electrical conductively joined throughout the circuit. Green wires are also equipment grounding conductors.
At the switch itself there are 3 main electrical screws, one of these 3 screws is distinctly different in color (perhaps darker) than the other 2. This screw connection is called the common screw. It is very important that in order for the 2 switches to work as they are intended to that the correct wire is attached to the common screw. Basically as depicted in the drawings one switch has the ungrounded conductor (hot) from the 'circuit power supply' cable attached to the common screw, where the other switch had the switched ungrounded conductor (hot) feed to the light fixture itself.
Please also note that there are a variety of manufactures out there that make 3 way switches so it is possible that the switch you buy may have the common screw located in a different spot or side of the switch then depicted in the drawings in this article, just make sure that the wire depicted to go to the common screw of each of the switches is actually connected to the common screw of the 3 way switch you bought. The other 2 wires going between the remaining screws of one switch to the other switch does not matter as long as one wire of the 2 remaining wires go on each of the remaining 2 screws of the screw.
If there is an equipment grounding screw on the 3 way switch it may be green in color and be separated away from the main connections of the switch and likely part of the metal frame that is also part of the mounting structure of the switch.
By: Donald Kerr
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