Most people are already familiar with three-way switches, they just don’t know what they are called. The paired switches at the top and bottom of a run of stairs, or opposite ends of a long hallway, that control the same light are three-way switches. Unlike a standard switch, where the up position is “on” and the bottom is “off,” three-way switches simply toggle between on and off at each switch throw from either end.
A three-way switched light requires an extra wire in the circuit, called a “traveler,” that enables both switches to function together. Occasionally we see three-way switch circuits that have been wired incorrectly, with the result that one of the switches only functions when the other one is set at one of its two positions.
Also, see our blog post How does a three-way switch work? for a complete explanation of how it functions.
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Here’s links to a collection of our other blog posts about ELECTRICAL WIRING:
• Which house appliances need a dedicated electrical circuit?
• Can a short circuit cause a high electric bill?
• What is the maximum spacing requirement for securing NM-cable (nonmetallic-sheathed cable)?
• Is it alright to just put wire nuts on the end of unused or abandoned NM-cable or wiring?
• What causes copper wires to turn green or black in an electric panel?
• What are typical aluminum service entrance wire/cable sizes for the electrical service to a house?
• Why is it unsafe to bond neutral and ground wiring at subpanels?
• Should I get a lightning rod system to protect my house?
• Why is a strain relief clamp necessary for the cord connection to some electric appliances?
• Does a wire nut connection need to be wrapped with electrical tape?
• What is the minimum clearance of overhead electric service drop wires above a house roof?
• What are the requirements for NM-cables entering an electric panel box?
• What is the color code for NM cable (Romex®) sheathing?
• Why is undersize electric wiring in a house dangerous?
• What causes flickering or blinking lights in a house?
• Why are old electrical components not always "grandfathered" as acceptable by home inspectors?
• How can I find out the size of the electric service to a house?
• Can old electrical wiring go bad inside a wall?
• What is an open electrical splice?
• What are the most common electrical defects found in a home inspection?
• What is the life expectancy of electrical wiring in a house?
• What is an "open junction box"?
• How dangerous is old electrical wiring?
• What is a ground wire?
• I heard that aluminum wiring is bad. How do you check for aluminum wiring?
• What is "knob and tube" wiring?
• What is the code requirement for receptacle outlets in a closet?
Visit our ELECTRICAL page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.