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How Does Light Switch Wiring Work?

Dec. 15, 2021

Being a smart homeowner means knowing what's going on in your home and how it works, including the electrical components. Behind your walls, there are wires running up and down that allow a light switch on the first floor to turn on a tall chandelier hanging from the ceiling. The switches are usually located near doorways, allowing us to control ceiling fixtures, wall sconces, and even some electrical outlets with a simple flick or tap. While this may seem amazing, it's just a matter of understanding how light switch wiring works.

Smart Light Switch

 Smart Light Switch     

Especially if you plan to complete any DIY electrical work, such as repairing or replacing a switch or adding a new light fixture, it's important to understand the basics of how these switches control your electricity. By taking the time to understand how your switch wiring system works, you can reduce the risk of electric shock or fire when using your switches. Check out our comprehensive guide below for the ins and outs of light switch wiring, including information on energizing and terminating switches.


A switch is an electrical device used to manually or automatically break or turn on a circuit. The operation of a switch depends on the ON/OFF mechanism. Various electrical or electronic circuits use switches to control or trigger owl circuits. The type of switch depends on the connection of the circuit they are made for. Two basic components (such as poles and through-holes) define which types of connections a switch can make.


How does light switch wiring work?

The way a light switch is wired depends on whether power enters the light box or the switch box first. These two types of electrical switches are called energized and endline switches.


Straight-through switch

With feed-through wiring, power enters the switch box directly. The feeder cable (hot wire from the service panel) reaches the switch before it enters the fixture. Two cables enter the switch box: one to supply power and one to connect the fixture. The neutral wire is spliced, and a black wire connects to each switch terminal. (Ground wire not shown.)

Smart Light Switch

 Smart Light Switch     

If power enters the switch box first, the neutral white wire from the service panel is spliced to the white wire leading out of the light. The hot black wire from the power supply goes through the switch and from there to the lamp. Toggling the switch interrupts the current flow to the lamp, which turns it off and on.


End-Line Switches

If power is applied to the fixture before going to the switch, you have "end wire" wiring. There is only one cable going into the switch box, from the fixture. The white wire to the switch should be marked black to indicate that it is hot. (Ground wire not shown.)


If the line carrying the power enters the light box first, the circuit must still be wired so that the switch interrupts the black wire. The white wire from the service panel is connected to the side of the light. The black wire is connected to the black wire in the cable that connects to the switch. The white wire from that cable also connects to the switch and returns and connects to the lamp. Flipping the switch interrupts the current, and the switch will function.


Because the white wire from the switch to the lamp is now hot, it must be marked to indicate that it is hot. Wrap a piece of black electrical tape around the ends or use a marker to paint the end black to show that it is energized.If you want to get more information about the switch, welcome to contact us today or request a quote.  

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