Solera Home Improvements provides you with electrical wiring services in the greater metro area of San Jose, CA
Electrical Wiring – San Jose – How Switched Circuits Work
The first article in this series on electrical wiring acts as the table of contents for the series.
I apologize for the crudely drawn picture.
I could not find a good set of pictures to show how both configurations of a switched circuit works, so I drew one and scanned it and I’m not the best artist.
In any switched circuit, the permanent or un-switched power enters one of the junction boxes, and the wire run to the other is called a switch leg.
In a switch leg, the normal concepts of “hot” and “neutral” do not directly apply, which is explained further below.
Un-switched power in switch box
This is shown in the top picture.
The hot wire (black) is connected to one side of the switch.
The other side of the switch is connected to the black wire of the switch leg, which in turn connects to one side of the light fixture.
The white wire of the switch leg is connected to the other side of the light, and in the switch box, the switch leg white is joined to the neutral return.
In this configuration, when the switch is open, neither wire of the switch leg is hot, and when it’s closed, they both are.
Un-switched power in fixture fox
This is shown in the bottom picture.
The hot wire (black) connects to one side of the light fixture.
The other side of the light fixture connects to the black wire of the switch leg, which in turn connects to one side of the switch.
The white wire in the switch leg connects to the other side of the switch.
In the fixture box, the white of the switch leg is connected to the neutral return.
In this configuration, the switch leg black wire is hot all the time, and the switch leg white is hot when the switch is closed.
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