How does three way switch work

Normal sheathed cable runs from the right switch to the light. Assume that, with the switch up, terminals 1 and 3 are connected as shown above. If the switch is down, then terminals 2 and 3 are connected. You can see if you trace through the wires and the switches that in the previous figure, the light is off. You can also see that if you flip either switch, the light will turn on.

And if you flip either switch again, the light will turn off. It is actually a very simple arrangement once you see it all exposed like this! There are several other ways to wire three-way switches to a light. For example, the power from the fuse box could come in at the light fixture and there could be two switches in series running from there.

The light goes off. I operate the switch on the right again, and the light goes back on. However, the current now flows through traveler wire T1.

Electrical Word Warrior aka Electrical Glossary 3-Way Switch — a 3-way switch has 3 terminals: 2 brass terminals for the 2 traveler wires, and 1 common black terminal for the common wire. A 3-way switch circuit is always comprised of two 3-way switches that control light s or device s from two different locations.

Can you guess why? You can soon impress your friends with your 3-way switch troubleshooting skills. To compound the problem, a traveler wire is then usually connected to the common terminal as illustrated below.

Deceptively, the 3-way switch appears to work properly when you operate the switch. See below that when I flip the switch on the left, the light goes on. When I double-check my work by operating the switch on the right, the light goes off just as I expect.

I think I nailed it. I decide to go back and operate the switch on the left one more time. I expect the light to go back on. Current does not have a path. The moral of the story is, never be content operating 3-way switches just a couple times. To confirm you wired them correctly, check back and forth between switches at least 3 times.

This circuit also shows rough-in boxes, wire nuts, and proper color code. Note that the light can be placed anywhere in the return wire, shown above as white. It may be as shown at the end of the run, but it may be between any pair of switch boxes as shown in a later figure , or even between the panel and the first switch box.

You can use as many 4-way switches as you like. For the official word, consult the National Electric code. Here I will try to describe a bit of what the color coding is about, and how wires should be colored in lighting circuits and why. Common practice in wiring a multiswitch circuit is to use two-conductor black and white cable from panel to the first switch, and then three-conductor black, red, white cable between pairs of switches.

White denotes neutral, a current carrying wire that is bonded to ground in the circuit breaker panel. Black and red are used for "hot" conductors volts with respect to ground. The previous figure shows a circuit that follows this convention. The NEC allows certain exceptions to this in lighting circuits, so that standard two-conductor black and white and three-conductor black, red, and white can be used, and used efficiently. In particular, it is often convenient and efficient to place a light between two switches or between the panel and the first switch.

In such cases, it is convenient and permissable to bring volts to a switch via a white wire. If you place a light in such a location, please be aware of the confusion that can occur from this wire color. In the above picture, white is always neutral, while black or red may be hot.

If the light is located between the middle two switches, then the white wire leading from the light to a switch is, in fact, sometimes hot. To avoid confusion and to conform to code, use a black marker to mark any "hot" white wire feeding a switch. Unfortunately, not all 3- way switches are wired the conventional way.

If you have any problems with these switches, it may be best to call an electrician. All of the switches shown below are 3- way. With conventional wiring, the common wire from one switch connects to line, the common wire from the other switch connects to the load lights.

The pair of travelers on one switch connect to the pair of travelers on the other switch. Usually, the common wire is wrapped around the traveler wires for identification in the 3- way light switch electrical boxes.