A switch leg is the conductor from the load side of a switch to the fixture, live only when the switch is on. Where power arrives at the light first and a cable runs down to the switch, the arrangement is called a switch loop, and because code requires a neutral at most switch locations, that loop is run in three-wire cable. Marking which conductor is the switch leg at rough-in saves confusion at trim.
Red is the switch leg to the fan, black goes to the light, both come off the two switches in the double gang.
Also heard as
- switched leg
- switched hot
Related terms
Traveler
One of the two conductors run between three-way switches, carrying power on whichever path is selected.
Hot
Ungrounded, voltage-carrying conductor of a circuit, and as an adjective anything that is live.
Home run
Part of a circuit running from the first box back to the panel, or the arrow on a drawing that shows it.