Identifying the Correct Screw on
4-Way and 3-Way Switches
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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
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.
Written: Dec 2, 2011
Revised: June 18, 2013
Proof Read / Released: July 12, 2013 Diagrams redrawn with Transparency:
Sept. 20, 2013
By: Donald Kerr
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