Wiring Done Right

Electrical Wiring and Safety

Identifying the Correct Screw on
4-Way and 3-Way Switches

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3 WAY SWITCH

3 Way Switch

3 Way switches have 3 main connection screw on it. A screw that is called the common screw is distinctly different in color, perhaps as in the example above is darker in color than the other two.

Beware there are a variety of manufacturers of 3 way switches so it is possible on the switch you buy may have the common screw in a different location on the switch than in the example above.

When wiring a 3 way switch circuit it is important to correctly identify the common screw of the switch, the 3 way switch circuit will not work properly without the correct wire attached to the common screw. The other two main screws are used to attach what is referred to as traveler wires, that attach from one switch to the second 3 way switch.  (or in the case of a 4 way switch circuit there will be one or more 4 way switches between the two 3 way switches)

On the newer 3 way switches you may find an equipment grounding screw on the 3 way switch (may be green in color) it should be easy to identify as it is on the metal frame of the switch and if present the equipment grounding wire gets attached to it, and on most wiring cables that equipment grounding conductor is the bare wire in the cable.

4 WAY SWITCH

4 Way Switch

On 4 way switches there are 4 main connection screws, 2 matching pairs, it is important to identify each matching pair, in the above example you will notice the bottom 2 screws are darker in color than the top 2 screws, so you have a matching pair at the bottom left and right and another matching pair at the top left and right.  Also in the above example there is an equipment grounding screw that is green in color.

4 way switches are used in conjunction with 3 way switches in which you have a 3 way switch at the start and end of the switch circuit and one or more 4 way switches in between. They are used to switch on and off at 3 or more locations.

So the two traveler wires goes from a matching pair of screws to the next switch in the circuit, and the other matching set of screws attach wires going to a previous switch.

There are a variety of manufacturers of 4 way switches so it may be possible that the main screws may be allocated in different locations then illustrated on the diagram above therefore be sure to identify where the matching pairs are located on the switch that you buy.

By: Donald Kerr

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Donald Kerr / Wiring Done Right
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