Tag: Smart Switches

Dear Mr. Electrician:  What are the choices of light switch wiring diagrams to wire a light switch to a ceiling light? Answer:  Light switch wiring diagrams are below.  The choice of materials and wiring diagrams is usually determined by the electrician who installs the wiring and by the electrical and building codes in force at the time of construction. NOTE: Some text links below go to applicable products on Amazon.  As an Amazon Associate, I earn from qualifying purchases.  Using my Links helps to keep this website FREE. If you plan to install a ceiling fan, visit my Ceiling Fan Wiring Diagrams post by clicking here. The architects and engineers who designed the project sometimes determine the light switch wiring methods and materials in commercial and industrial construction.  Light switch wiring diagrams and wiring methods are sometimes furnished to the contractors doing the installation.  For WiFi smart switches, you must adhere to the manufacturer's wiring instructions. Table of Contents: Choices of Switch Wiring Diagrams WiFi Smart Switches and Digital Controls Before Working On Existing Switch Wiring AN UPDATE to the National Electrical Code (NFPA 70) in article 314.27(C) requires that all ceiling light electrical boxes in habitable rooms at possible ceiling fan locations be rated for ceiling fan support.  This means that a fan-rated ceiling electrical box must be installed whether or not you plan to install a fan. CHOICES OF SWITCH WIRING DIAGRAMS The two conductor switch wiring diagram at the top of this post is from older homes and is likely not used much anymore, depending on which code book is in force in each jurisdiction. The two-conductor cable from the ceiling box to the light switch should have the white conductor re-identified with another color because it is not being used as a neutral but as a hot wire.  However, in most cases, the white wire is not re-identified with another color. If you see a white wire on a wall switch, it is most likely not a neutral conductor.  Neutrals are rarely required to be switched. Re-identifying a wire is done using colored electrical tape.  Some electricians use a permanent marker. Although re-identifying a wire is the code requirement, it has not been implemented as much as it should.  Consequently, it is common to find a white wire in a switch box that is the hot LINE, and the black wire is the switch leg connected to the LOAD. You cannot connect a receptacle outlet to the above type of switch wiring because there is no neutral wire in the switch box, but you can at the ceiling electrical box, assuming there is enough room for the extra wires. It is required by the National Electrical Code (NFPA 70) that a neutral conductor be available in each light switch electrical box.  See Article 404.2(C). The neutral is needed for electronic dimmers, timers, and WiFi smart home devices that can be installed instead of an ordinary light switch.  This is why the above wiring diagram is not used much anymore.  All of Article 404 pertains to the installation of switches. It is...