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Three-Way Switch Circuits - Which One Should I Use - Part VI
by Phil Kingery
Oh no! How will Captain Coupling get out of this one? Unfortunately, he
was ambushed by Dan Rather and a 60 Minutes camera crew where he was discovered engaging
(*g*a*s*p*) in a "3-way" ! (If you know what I mean, wink, wink, nudge, nudge!)
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Which One Should I Use, Part VI (Preamble)
Well, hello again, you gluttons for punishment. I can only imagine all
the nice email you have been sending me but, unfortunately, I have not been able to see it since my
old address is now kaput. Fear not, for I have a new email address. It is
pkingery@act-solutions.com
. Now that we here at ACT now have our own web site I don’t want you to completely abandon my
friend Bob here at
HTI
(Home Toys Inc.).
At the end of the last installment of this (seemingly never ending)
series, I wasn’t sure if I should continue with complex coupling or if I should let that rest for a
while. For months I have been promising to give you an article on "X-10 Three-Way Switch
Circuits". I guess this is as good a time as any. (For you surfers who have discovered
this section of HTINews for the first time, I urge you to back up and
review a few of the earlier chapters
or this one won’t make a lot of sense.) Therefore, this section is entitled:
Which One Should I Use, Part VI
(Three-Way Switch Circuits)
I need to get a few things off my chest before I get into this. Of all
the technical calls we get in my office, the overwhelming majority have to do with 3-ways (and I
don’t mean the kind that Captain Coupling was caught doing). Usually the underlying problem is that
the installer doesn’t understand standard 3-way circuits, let alone
X-10 3-way circuits. Often the caller will become angry at us because it seems that
we are incapable of visualizing what he needs. I have had more than one installer yell at me
saying, "...you are supposed to be the experts and you can’t tell me how to install
this?!?". We may be the experts, but we can’t see through the phone in order to tell what
kind of 3-way circuit he has. There are many variations in standard 3-way wiring and in most cases
the installer has no idea which one he has. It is unfortunate that he assumes that there is only
one kind. Believe me, nothing could be further from the truth. The many variations in 3-way
circuits dictate which X-10 3-way receivers will work and which ones will not.
Before we talk about "X-10" 3-way circuits, we need to
talk about "standard mechanical" 3-way circuits. Have you ever wondered why they
are called "3-way circuits" when there are only 2 switches? Well, it has to do with the
number of "drop points" and not the number of switches in the circuit. You see back in
the early days of electrical wiring, back in the days of Thomas Edison, the vocation of
"electrician" was brand new. These new electricians would base their cost estimates
partly on the number of "drop points" on each circuit. A drop point could be a switch, a
load or any junction point. In a sense a circuit with only 1 switch and 1 load would be a
"2-way". I suppose this was because the wires had to go "two different ways". A
circuit with 2 switches and 1 load would be "3-way". Incidentally, a circuit with 1
switch and 2 loads would also be a 3-way, but over the years, the label of "3-way" has
evolved into meaning any circuit with 2 switches in it.
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It
is rare indeed to find any house in North America that does not have at least one 3-way circuit.
Perhaps it is at the top and bottom of a stairway or at both ends of a long hall. In any case, it
enables the user to turn on or off the load (usually a light) from either location. It sometimes
seems confusing that the switches are made so that "on" can be either "up" or
"down" depending on the position of the other switch. How are these wired? Let’s look at
a standard mechanical 3-way circuit. Figure 1 shows a typical 3-way circuit. This is what I think
of when I think of a 3-way circuit: 2 switches with the load at the end.
This diagram is pretty good but it was a pain to draw. Besides it’s
hard to see where the wires go. Since I don’t want to draw complex drawings every time, and I want
you to be able to see where the wires go, I am going to simplify all the diagrams from here on.
Figure 2 is a much more practical drawing for the purpose of this article.
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(Let me get one more thing off my chest. Just because this drawing
starts with the breaker panel on the left, then the switches, and then the
light on 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.
It’s a good thing I wasn’t close enough to strangle him....)
Look
closely at the diagram. Please notice that the current for the
light
bulb must travel through both switches. If you remember nothing else from this article, please remember this:
How do X-10 3-way master receivers work? Some X-10 3-way master
receivers are standard 2-wire dimmers with a third "
control
" wire (figure 3). If you hook up just the line (black) wire and the load (
blue
) wire, it would work just like a standard X-10 dimmer
receiver.
Others have a neutral wire. These are usually called "3-wire"
dimmer receivers. You may have inadvertently misread that last sentence. I didn’t say
"3-way", I said "3-wire" receivers. These are not
the same thing but if you are scratching your head right now, you should go back to the earlier
chapter "Which One Should I Use?" and possibly "Which One Should I Use
- Part 2" to see what I’m talking about. A 3-wire dimmer with a fourth wire (
control
) is a 3-wire, 3-way dimmer receiver. Again, if one of these are wired using just the line (black)
wire, the neutral (white) wire and the load (
blue
) wire, it would work just like a standard X-10 dimmer receiver. So what makes them a 3-way master?
If voltage is applied to their
control
lead they will change state. That’s where the slave switch comes in.
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Figure 3 also shows how the "slave" switch (or
"auxiliary" switch if you want to be politically correct) is connected to the 3-way
master. All the 3-way masters use the same slave switch. (We here at ACT sell five different 3-way
masters: RD101, RD161, RD123, RS101 and the RS301). If you are only familiar with mail-order X-10
or Radio Shack slaves switches, they still do the same job but they may look different. The X-10
and Radio Shack versions have wires while our slave switch (part number AS001) has screw terminals
(like our 3-way relay receivers, RS101 and RS301, shown in figure 4).
 Slave
switches (oh, all right, "auxiliary" switches -- happy now??) are just high voltage
momentary push buttons. They are, in a sense, fancy doorbell buttons. When the button is pressed,
line voltage is applied to the
control
lead (but please don’t try to use a doorbell button, okay?).
The single biggest mistake made by installers trying to retrofit a
pre-existing 3-way, is that they don’t know which kind of 3-way circuit they have. (Most may not
even know that there are different kinds.) In order to change an existing 3-way into a X-10
3-way, the installer must first identify how the circuit was originally wired. Once that is done,
choosing and installing the appropriate X-10 3-way receiver is relatively simple. In this
installment, I am going to present four different ways that a standard 3-way might be wired. (There
are a few more but four is all I’m going to tackle in this edition.)
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Here are some things to consider.
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. (Believe me, I have
seen people try that.)
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. We at ACT sell
these under our part number RD101. (And yes, Leviton has similar units but since I work for ACT,
I’m only giving you our part numbers.)
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. We at ACT sell
these under our part number RD161 (and our 2400 watt version, RD123). I know that this is somewhat
confusing but that’s the way it is.
All relay receivers require a neutral wire (our RS101 and
RS301).
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.
1. Standard 3-way circuit with the load at the end of the
run.
Look back at
figure1
and especially
figure 2
. (This article is already so long that Bob would kill me if I duplicated the same diagrams again
so you’re just going to have to scroll up and look at them....
[The editor gremlin makes Phil happy by adding a quick link back to the
figures :-)]
Good, now you’re back.) To convert this version to an X-10 3-way, simply replace the first
mechanical switch with a slave switch (as shown), then replace the second mechanical switch with
the appropriate X-10 3-way Master. (Figure
5.)
If the load is incandescent and less than 500 watts, a 2-wire dimmer (I
know, 3 wires if you count the
control
lead) can be installed. If you have read my previous words of wisdom, you know that when ever there
is a neutral wire available, I always recommend a 3-wire dimmer. They just work better. In this
example, we are extremely lucky to have a neutral connection available in the j-box, so I suggest a
3-wire dimmer (our RD161). If the load is greater than 500 watts, or is something that you just
don’t want to "dim", then a relay receiver (ACT’s RS101, for instance) can be installed.
Both the relay receiver (RS101) and the 3-wire dimmer (RD161) require a neutral connection.
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2. Standard 3-way circuit with load in the middle of the
run.
 Figure
6 shows another common method of wiring a 3-way circuit. In this version the switches are at both
ends of the circuit run and the load (a light, in my example) is in the middle j-box. To convert
this to an X-10 3-way, simply replace the first mechanical switch with a slave switch (as shown in
figure 7), then replace the second mechanical switch with a 2-wire, 3-way master dimmer receiver
(like the ACT RD101).
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 This
is where the plot thickens. If the load exceeds 500 watts, or is non-resistive, we have a problem.
Look closely at figure 7. Neutral is available only in the first two j-boxes. The 3-way master is
sitting in the third box and there is no neutral wire there. Can you swap the slave and the master
in order to use a 3-wire dimmer or a relay receiver? Nope! There aren’t enough wires. You are
stuck. If you are trying to convert this kind of pre-existing 3-way circuit to an X-10 3-way, you
are limited to using a 2-wire dimmer. If your load is greater than 500 watts or is something other
than a regular incandescent light, you must abandon the use of a true X-10 3-way and instead use a
single relay receiver (like the ACT RS121) in the first position and a wall-mount transmitter (like
the ACT TB100 with a keypad) in the last position (as shown in figure 8). Also please note that you
will have to get up on a ladder and do some rewiring in that middle box to accommodate the
electrical needs of these devices.
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 If
dimming is desired, yet the use of a 2-wire dimmer (RD101) is inappropriate, a 3-wire dimmer
(RD161) can not be used in place of the 2-wire dimmer (in figure 7) since there is no
neutral. You can, however, use a 3 wire dimmer or a relay receiver (figure 8) but not as a true
3-way masters. There are not enough wires from one j-box to the others.
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3. Standard 3-way circuit with the load at the
beginning of the run.
 Okay,
we’re half way there. Figure 9 shows another wiring version of a standard 3-way circuit. In this
example, the load (or light) is first and then the two switches are in the second and third
positions. If you thought the last one was difficult, this one is a killer. Since neutral exists
only in the first j-box, the choices of X-10 master receivers is limited only to the 2-wire dimmer
versions since they operate on the trickle current through the load.
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 To
convert this version to an X-10 3-way, simply replace the first mechanical switch (second position)
with the 2-wire, 3-way master (like the ACT RD101) and then replace the second mechanical switch
(third position) with the slave switch (AS001) as shown in figure 10. The load must be incandescent
and 500 watts or less. Can you imagine how frustrating it can be for an installer who orders a
3-way relay receiver and a slave switch and then tries to install them into this kind of a
circuit? Sorry, it won’t work. (Of course, then he calls me and wants me to "fix it" over
the phone.)
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If the load exceeds 500 watts, or is non-resistive, then the only
option is to abandon the use of a true 3-way and install a fixture receiver and two transmitters
(as shown in figure 11). It ain’t pretty but it’s the only option I can give you for this one. In
commercial buildings we can pull more wires through the conduit, but in a house, you are usually
stuck with whatever is already there.
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4. Standard 3-way with the load at the
beginning of the run and the switches split.
 This
is the last one we will do in this edition. Look at figure 12 and you will see a 3-way circuit
where the light is actually in the first j-box and then the 2 switches are split off on either end.
Unlike most of the previous examples, converting this type of 3-way will require
significant wiring changes in the load j-box.
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 Since
neutral exists only in the first j-box, the choices of X-10 3-way master receivers is limited to
the 2-wire variety since they operate on the trickle current through the load. To convert this
version, simply replace either mechanical switch with a 2-wire, 3-way dimmer (like
the RD101) then replace the other mechanical switch with the slave switch (as shown in figure 13).
The load must be incandescent and less than 500 watts.
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 If
the load exceeds 500 watts, is non-resistive, or the use of a 2-wire type dimmer is inappropriate,
the installer must then abandon the use of a true X-10 3-way and instead use a relay receiver and a
wall mount transmitter (as shown in figure 14). Remember, with this version, a significant amount
of rewiring will be required in the load j-box to accommodate the electrical needs of these
devices.
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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. ACT’s RD101 dimmer is rated for
500 watts, incandescent only. The RD161 is also rated for 500 watts, for resistive and non-linear
loads. Both the RS101 and the RS121 are rated for 20 amps on 120v. ACT’s RF100 fixture receiver is
also rated for 20 amps on 120v. This article was written for the Home Automation market in mind and
so it implies only 120v circuits, however, ACT also offers a 277v version of the RS101. It is the
RS301. The AS001 is rated for 277v and 120v. And most importantly, Never use the ground wire for
anything other than ground!
Well, we have come to the end of another chapter in this "Which
One Should I Use" series. I knew when I started this one that it would be big and I was right.
In the next chapter (February 1998) we will look at two more 3-way wiring scenarios (one is the
most complicated one I have ever seen, the other is the easiest) plus 4-way wiring. If time
permits, we will also get into some 3 & 4-way troubleshooting.
Like everyone else who puts their work out on the web, I love to hear
your comments. (It strokes my ego.) If you have any questions on this or any previous article in
this series, please email me. If you have any suggestions for future discussions, please let me
know. Have a nice Christmas and New Year and I hope to see you at the Consumer Electronic Show in
Las Vegas in January . I will be teaching a class there so please stop by and say
"Hey".
What is a "California 3-way"? (Sounds kinky, doesn’t
it?)
What is the "simplest" 3-way to install?
What about 4-way circuits?
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
pkingery@act-solutions.com
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The Smartest DIY Home Improvements
