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#5540 11/24/01 02:53 PM
Joined: Jun 2001
Posts: 25
Does someone have an idea how the 4 way switch works?

#5541 11/24/01 04:08 PM
Joined: Nov 2000
Posts: 2,236
Likes: 1
A four way has four screws, usually labelled in pairs as "in" and "out".

For sake of explanation, we'll call the four screws a name, "in-left and "in-right", and "out-right" and "out-left", going clockwise... (follow me so far?)

Think of the internal connections between "in-left and "out-left",and "in-right" and "out-right" as an =, and the connections between "in-left" and "out-right", and "in-right" and "out-left" as an "x".

The travellers will either connect to one side or the other on the "out" side as the toggle is thrown.

As far as wiring, put the hot travellers on the "in" side and the load travellers on the "out" side, you may keep the black to black and red to red (or any other color other than white, green, natural grey, or green with a yellow tracer) for courtesy's sake, but they'll work fine reversed.

Don't be confused with the screw colors, black screw to black wire, silver screw to white wire would be incorrect and the device won't do its job this way.

Internally, I've never dissected one, but I imagine it to be relatively simple mechanically.

[This message has been edited by sparky66wv (edited 11-24-2001).]

Residential/Commercial Inspector
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Member IAEI
#5542 11/25/01 04:00 PM
Joined: Oct 2000
Posts: 2,722
Broom Pusher and
Here's a Schematic drawing of a 4 Way Switch, which can be used as a visual aid to reference Virgil's explanation above.

He has posted avery nice description of the 4 way switch's function and internal circuitry [good job, Virgil!].

Schematic - 4waydtl1.gif: 4 way toggle switch internal circuitry detail...

[Linked Image]

If you view the two sections [the "A" part and the "B" part] as two separate "3-way switches", connected together at the handles so they both toggle together, the circuitry becomes a little more simpler to grasp.

Point "Ax" and "Bx" are connections to travelers - "Ax" being one traveler, "Bx" the other. For this example, refer to "Ax" / "Bx" as the Incoming travelers [from the "Hot" 3 way switch].

Point "Ay" and "By" are the output connections to the travelers, which will run to the other 3 way switch [at the "load" end of the loop].
If more than one 4 way switch is used in the switch loop, then the "y" output points will run to the "x" input points on the next 4 way switch [and vice verse].

There's no limit to how many 4 way switches can be in a loop - as long as they are set between the 3 way switches - with the 3 ways on the "Ends" of the loop.
There must be two - and only two 3 way switches within any normal switch loop of this type, with the exception of special / custom type circuits. Those type are beyond the scope of this thread, so I will not include their criteria.

If a standard type 3 way dimmer is used in the loop, just swap one 3 way switch for the dimmer.

Hope this is helpful!

Scott SET

Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
#5543 11/25/01 08:31 PM
Joined: Oct 2000
Posts: 5,392

#5544 11/26/01 01:39 PM
Joined: Oct 2001
Posts: 19
Is it me, or is that site missing the case when the feed comes in at a 4 way switch in the middle and the fixture is connected at a different 4 way switch in the middle?

#5545 11/30/01 03:36 PM
Joined: Nov 2001
Posts: 20
Think of 4 terminals in a square pattern. A 4-way switch internally will connect either the top left terminal to the bottom right, or the bottom left to the top right. It's like one half of an X which flip-flops back and forth.

What's confusing to many people, in my opinion, is that 3-way and 4-way switches are misnamed. A 3-way switch is actually a 2-location switch (having 3 terminals, and 2 switching states), and a 4-way switch is actually a 3-or-more-location switch (having 4 terminals, and 2 switching states).

In a circuit, use the following rule:

Switched from 1 location = 1 2-way switch
Switched from 2 locations = 2 3-way switches
Switched from 3 locations = 2 3-way switches
1 4-way switch
Switched from 4 locations = 2 3-way switches
2 4-way switches

For n locations, where n >= 2, the number of 3-way switches is always 2, and the number of 4-way switches is always n - 2


#5546 11/30/01 05:16 PM
Joined: Aug 2001
Posts: 7,520

Just to add to the confusion, what you call a 3-way switch is known as a 2-way in England. A 4-way is generally called an "intermediate."

#5547 11/30/01 05:55 PM
Joined: Oct 2000
Posts: 5,392
............which brings the always fun Q, why is it called a 3-way???
[Linked Image]

#5548 11/30/01 07:13 PM
Joined: Dec 2000
Posts: 4,289
Sparky (aka the Riddler)I think already knows the answer to this. I'm going to venture a guess (sacrifice bunt) [Linked Image]
One up, one down
Both up
Both down

#5549 11/30/01 08:58 PM
Joined: Aug 2001
Posts: 7,520
Hmm, by counting the possible switch combinations couldn't you also call it a 4-way?

A up, B up
A up, B down
A down, B up
A down, B down.

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