With the increasing number of electrical devices being used in the home today, extending existing wall outlet circuits or installing new ones are common projects undertaken by the DIY electrician. There are several ways of getting power to the newly installed outlets: you can tap into an existing outlet circuit, you can run a new circuit from the service panel, or you can tap into a light switch circuit. The National Electrical Code permits this method as long as the point at which you make your connections contains a circuit neutral conductor. Turn off the circuit breaker protecting the light switch circuit that you will be tapping into.
Pick the diagram that is most like the scenario you are in and see if you can wire your switch! This might seem intimidating, but it does not have to be. With these diagrams below it will take the guess work out of wiring. Still looking for help?
Two, 2-wire cables C3 and C4 run between the fixtures, and a 3-wire cable C2 runs from the second fixture F2 to the second 3 way switch SW2. The hot source is connected to the common terminal of SW1. The neutral is spliced to the white wire feeding the first fixture, via cable C1,where it is spliced to the neutral of both lights.
In this video, I explain just how easy it is to add a three-way switch to an existing single pole one switch lighting circuit. Now if you are trying to install a completely new 3-way circuit please my video with an article on how to install a three-way. You can still save a few bucks by installing the wire yourself. The hardest part will be running the 4 wire from the existing switch to the new one. Take a look at my video and ask any questions if you need help.