Every wire,
where it goes.
Pick the box in front of you. You get the drawing with every wire in its real color, where each one lands in plain English, and the job in order. Every diagram is run through a circuit simulator before it is published.
What are you wiring?
- 01Light switchesSingle-pole switches, dimmers and smart switches, with power at the switch or at the light.
- 033-way and 4-way switchesOne light from two or three places: travelers, commons and where the power comes in.
- 05Outlets and GFCIEnd and middle of the run, half-switched outlets and GFCIs that protect the rest of the circuit.
- 07Ceiling fansA fan and light on one switch, or on two switches with a 3-wire cable.
- 09Wire size and voltage dropThe wire size for any amps and distance, checked for voltage drop.
The most common box: a light switch with power at the switch
Open this diagramEvery wire, its color and where it lands, box by box, is drawn on your job card.
What the colors mean
- Black: hot. Carries power from the breaker. Goes to brass screws and LINE terminals.
- White: neutral. Carries the current back to the panel. Goes to silver screws. Never switched.
- White taped black: hot. A white wire used to carry power, usually in a switch loop. Treat it as hot.
- Red: a second hot. A traveler between 3-way switches, or the switched leg to a fan light or half-switched outlet.
- Bare or green: ground. Ties every device and metal box to the panel's ground. Never carries current in normal use.
Every circuit on the panel
- Light switches 8 diagrams. Single-pole switches, dimmers and smart switches, with power at the switch or at the light.
- 3-way and 4-way switches 5 diagrams. One light from two or three places: travelers, commons and where the power comes in.
- Outlets and GFCI 7 diagrams. End and middle of the run, half-switched outlets and GFCIs that protect the rest of the circuit.
- Ceiling fans 2 diagrams. A fan and light on one switch, or on two switches with a 3-wire cable.
What size wire?
Enter the amps and the distance. The calculator sizes the wire for the amps by the NEC tables, then checks the voltage drop.
Size the wireWhen to call an electrician
Swapping a switch, an outlet or a fixture on wiring that is already there is a job many homeowners do. Adding circuits, working in the panel, aluminum wiring, and anything that smells hot or has scorch marks is not. The full list