More Three-Way and Four-Way Switch Circuits

Which One Should I Use, Part VII

Phil Kingery

Which One Should I Use, Part VII:
More Three-Way and Four-Way Switch Circuits
by Phil Kingery

Well, Captain Coupling went to La$ Vega$ and lost all his money at the slot machines. But he did get to go to the big Consumer Electronics Show and looked at all the new neat Home Automation stuff !!

Which One Should I Use, Part VII (Preamble)

Welcome back to HTI. Even though you are reading this in February (most likely), I am actually writing this at the Las Vegas airport the day after the Winter 1998 CES convention. I have a few hours before my plane takes me back home so I am sitting on the floor next to gate #3 typing on my laptop. Bob Hetherington (HTI founder and all ‘round nice guy) sent me an email before I came to Las Vegas and reminded me that February is just around the corner. So here I am, sitting on the floor, writing as fast as I can.

First let me tell you about CES which ran January 8-11. As always, it was huge. Most of it was in the Las Vegas Convention Center, with a major part in the nearby Hilton (more on that later) plus the Sands plus a few other hotels. (A few years ago, they moved all the "adult" stuff to one of the hotels. Now I can no longer pretend that I just accidentally walked by.) All the X-10 guys were there; the regular X-10 booth in the big convention center plus the "X-10 Pro" guys over in the Hilton. I was able to talk to a few of X-10 Pro guys for a short time, but kept missing the other X-10 people. The big news, however, at this year’s CES was not X-10 (its been around for years), it was HDTV and DVD (that’s "High Definition TV" and "Digital Versatile Disk".).

Now back to the Hilton. Most of the Home Automation stuff was there, plus the Habitech Institute. I was asked to speak at this year’s CES in the "Habitech" section. I am pleased to report that we had standing room only. (I can only assume that either I was worth listening to, or they thought I was somebody else. Either way, once they inside the room, we wouldn’t let them leave.) If you were among the attendees, please drop me an email at and let me know what you thought of CES. (If you also went to the new "Star Trek Experience" at the Hilton, let me know what you thought of that, too. It was so cool!! I even had dinner in Quark’s Bar.)

Back in December 1997, we began this two-parter on 3-way circuits. It is my intention that this second part will finish up 3-ways and throw in a little 4-way information. Since this is the second of two parts, you will be very confused if you have not read the first one. Therefore, unless you already have done so, I strongly suggest you go back and read "Which One Should I Use, Part VI". There are obviously five more articles before that and while I think every one of them is worth your reading, only part 6 has anything to do with 3-ways (Editors Note: You can find all of Phil's articles in the HTINews Article Library). And now, without further adieu, we are ready to proceed into:

Which One Should I Use, Part VII
(More Three-Way and Four-Way Switch Circuits)

You may recall from the last part, that I said that we get a lot of technical calls on 3-ways (and I don’t mean the kinky kind). It is common to find that the installer doesn’t understand standard 3-way circuits, let alone X-10 3-way circuits.

Just what "is" a 3-way circuit? Perhaps I assumed too much when I failed to explain, in the most basic way, what a 3-way circuit is. I taught a class in Las Vegas and after going over all the main 3-way circuit variations, someone raised their hand and asked, "When would I ever see a 3-way circuit?". You may have seen them but simply did not realized what they were. Perhaps it was two light switches at the ends of a long hallway (like figure 1), or at the top and bottom of a stairway, or even a switch in the kitchen and one in the garage that both control the same light. A 3-way circuit has the ability of controlling a load from two different locations.

We intuitively know that a light switch that is "down" is usually "off" and one that is "up" is usually "on". You may have never noticed, however, that in the special switches made for 3-way circuits do not have the familiar "on" and "off" embossed into the plastic. That is because "on" can be up or down, depending on the position of the other switch.

There are many variations in standard 3-way wiring and in the last part, we went over four of them:

  • Standard 3-way circuit with the load at the end of the run.
  • Standard 3-way circuit with load in the middle of the run.
  • Standard 3-way circuit with the load at the beginning of the run.
  • Standard 3-way circuit with the load at the beginning of the run, switches split.

This installment will cover:

  • Standard 3-way with one switch at the beginning of the run and the second switch and load split.
  • Standard 3-way "coast" circuit.
  • Standard 4-say circuits (just a one example).

(Let me get one more thing off my chest. Just because my drawings usually start with the breaker panel on the left and then flow to the right, does not mean that yours will always be in this "left-to-right" pattern. Yours may be left-to-right or right-to-left, up-to-down or down-to-up. As long as the circuit is wired in this progression, it is the same. Got that? I had a guy tell me one time that his circuit was different because his panel was on his right and the light was on his left.)

Here are some other things to consider.

  • In a mechanical 3-way, the current must flow through both switches.
  • In an X-10 3-way, the current flows only through the 3-way master switch.
  • A standard 3-way circuit can not be converted to an X-10 3-way circuit by replacing only one switch. Sorry, that simply does not work.
  • If a dimmer receiver is designed to work without a neutral connection (it only needs "line" and "load" wires) then I call it a "2-wire" dimmer. While it’s true that the control lead makes it a total of 3 wires, I still consider it a "2 wire" dimmer
  • If a dimmer receiver is designed with a neutral connection (it needs "line", "neutral" and "load" wires) then I call it a "3-wire" dimmer. While it’s true that the control lead makes it a total of 4 wires, I still consider it a "3-wire" dimmer
  • All relay receivers require a neutral wire.
  • Also, please note that in many of the diagrams that follow, the wire colors seems to change color. Believe me, they will not magically change colors as you connect them to various X-10 units. I simply chose the wire colors to show those most commonly used in standard 3-way wiring scenarios and then I changed them to show the wire colors of the X-10 receivers.

Lets begin this with a 3-way arrangement that is my favorite but unfortunately it is not as common as most of the others. Figure 2 shows a standard 3-way circuit with the switch at the beginning of the circuit and then the second switch and the load are split. Although this circuit arrangement may appear the most difficult, it is actually one of the easiest to change to X-10.
Figure 3 shows the best way to install the X-10 receiver and slave switch. Because of the availability of all the needed wiring, any of the X-10 3-way master receivers can be installed. That means that if you choose to use a 3-wire, 3-way dimmer (one that requires a neutral connection), you can. If you choose to use a relay receiver (which also requires a neutral connection), you can do that, too. That is because neutral is available in the junction box.
If you are sure that you will only need a 2-wire, 3-way dimmer, you can swap the locations (figure 4) and it should work just as well. If you do, however, you won’t be able to change your mind later and use a 3-wire, 3-way dimmer or a relay receiver because there is no neutral in that box and no way to get it there. If it were up to me, I would put the master receiver in the middle box (the first one in the circuit). It just makes things easier. Like many of the previous examples, converting this type of 3-way to an X-10 3-way requires no wiring changes in the load j-box.
Figure 5 is just about the strangest 3-way arrangement I have ever seen. It is called a "coast" or "California" 3-way. I’m sure that there is a great story about how this first came about, but unfortunately, I don’t know it. (If you do, please email me at .) Often, this same basic arrangement is wired in such a way as to accommodate two loads, one at the beginning and one at the end of the run (figure 6).
Since line and neutral wires exist in every box, this is one of the easiest ones to convert to an electronic 3-way.
The example (figure 7) shows the installation of the slave switch in place of the first mechanical 3-way and then a 2-wire dimmer in place of the second one. Since both boxes have the same wiring available, the slave and master is easily swapped. Since neutral exists in both junction boxes, a 3-wire, 3-way dimmer or a relay receiver can also be used.
Although not as common as 3-ways, a 4-way switched circuit can also be converted to an X-10 4-way. Figure 8 is a typical 4-way circuit diagram. Bear in mind that there are as many variations in how 4-ways can be wired as was shown in the 3-way circuits (but I am way too lazy to draw all of those variations). Only one example will be shown here. The diagrams previously shown on 3-ways can be used as reference should this example not be exactly as is needed.
Figure 9 shows the arrangement of two slave switches and one 3-way master receiver. Since this example is lucky enough to have a neutral in every box, it is quite flexible in the arrangement and what receivers can be used. Believe me, your luck runs out rather quickly when the 4-way circuit is wired in one of the many other ways that it can be wired.

BIG NOTE: All electrical work should be done by a qualified and licensed electrician adhering to all national and local electrical codes. Although circuit breakers are not shown, appropriately sized breakers are required on all circuits. And most importantly, Never use the ground wire for anything other than ground! (Editors Note: Please read Tony Stewart's letter to the NEC about this important safety issue.)

As the sun slowly sets in the west, I see that we have come to the end of another chapter in this "Which One Should I Use" series (which seems to go on and on and on and on....). I really hoped that this would not turn into a three parter, but it is clear that this is pretty long and to go into any troubleshooting would make it unbearable huge. I had hoped to get into some other variations in 3-ways. Charles Sullivan ( ) has taught me something new about residential 3-ways that I did not know (believe me, no one knows everything about X-10). Perhaps we will discuss it in the next part. The next chapter (April 1998) we have the option of finishing up 3-ways, looking at some slight, but important variations plus troubleshooting, OR we can drop this subject and go on to something new. I will let you decide. Depending on your votes, the next episode will be:

3- & 4-way troubleshooting

Noise and filtering

The basics of the X-10 binary codes

...or suggest your own topic.

You are going to have to let me know what you want, however I will only take votes until the middle of March. You know what they say in politics: Vote soon and vote often! Cast your vote through email:

I hope to see you at the Home Automation Association Convention in Orlando Florida, February 7-10. I will be teaching two classes (both on Monday, February 9th) at the convention so please stop by and say "Hey". I will also be teaching a full two-day course for our representatives. Remember, if you have already attended one of my classes, I need you to stand at the back and laugh at all my jokes and applaud wildly at the appropriate places. Well, children, until next time....

Can I use the slave switch any differently than these examples?

Why do some light bulbs just not work with 3-ways?

My new X-10 3-way will come "on" okay, but why can’t I can’t turn it "off"?

What will become of Captain Coupling?

Will we ever return to finish complex signal coupling?

Stay tuned, children! Same Bat Time, same Bat Channel!

Phillip Kingery is the representative of Advanced Control Technologies, Inc. and teaches X-10 related classes around the country. Email him at

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