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Three Way Switch Q&A

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Dear NH,

I am currently working as a commercial electrician in Springfield, OH. I got a service call to an old house in Urbana, OH a few weeks ago, to repair a three way switch which had been replaced by their in-laws.

After looking at it for two hours, unable to find but one traveler, I excused myself, and returned later with help. What we found, and I suspect some of your readers may find, was a VERY strange, way to connect the switches, but it worked!

The traveler I had found was in fact the common, or white, wire. As opposed to the normal way of connecting, these switches had hot and neutral on the non-common terminals (at both ends), and the load (the room light) between the common terminals. It Works! But I doubt any sane inspector would approve it! If both switches are switched to the neutral side, the light is off. It is also off when both sides are HOT! Only when one side is at neutral, and one at hot, would there be current flow, and the light, connected between the common terminals, would light!

We would have run new wires, and correctly wire the circuit, but one of the switches was located in the stairwell, on an outside wall, and we could see no way to get a cable to it! You should also consider that the house probably has knob and tube wiring, and NO GROUND wires. So the room light could well become HOT, but with no accessible place to find a ground (in the middle of the dining room), the homeowners are probably safe, or as safe as can be in a knob and tube wired house!

I mention this only for your benefit, since some of your readers may have this odd wiring on their 3-way switches, and will have no better luck than I originally did in troubleshooting them. I certainly don't want to encourage anyone to wire a new installation this way, but you might want to somehow include it on your 3-way circuits page, maybe as a footnote, to help the next guy who blindly runs into this!

BN

BN,

Quite an interesting story. I can see why this wiring method would work, and I think it is an ingenious solution to a difficult problem. There is no more danger posed by this wiring setup than the standard setup… especially considering that there is no ground available. Whether it would be code acceptable is another issue... since there is no power going to the fixture when the switch is in the off position, and you don't have two different circuits serving the fixture (even if on the same leg of the service, this would be unacceptable), I think it just might pass inspection with an explanation.

I know all our readers will not understand this discussion, but it really is not necessary. Rather, it presents a valuable concept concerning electrical work that is worth repeating. Many homes have unusual and sometimes dangerous wiring, done by inexperienced folks and never inspected by a professional. When in doubt about your wiring, don't be cheap… hire a licensed pro to troubleshoot the problem! Sometimes there is no textbook answer, so it takes an experienced hand on-site to find the answer!! Unlike most home repair goofs, which may cause a bump, bruise, or hurt egos, electrical wiring errors can KILL!


Dear NH,

A switch that controlled the chandelier in my dining room recently broke. I accidentally purchased a three-way switch instead of a single pole switch. I returned the three-way switch but I wonder if I wasted gas! Could have somehow wired it to work correctly?

BB from Tampa, FL

BB,

First, a little background for our readers. Three-way switches are used when a fixture is controlled by more than one switch. A common example would be the switches at the top and bottom of a stairway (or at opposite sides of a room) that control the same overhead fixture. On the other hand, single-pole switches are used when a fixture has a single switch controlling it.

Normally, you wouldn't use a three-way switch for a single-pole application because (1) there are no "on-off" labels on the switch (admittedly a weak argument since the labels are virtually unreadable) and (2) they are a little more expensive. However, in a pinch you can use one IF you wire it correctly.

Three-way switches have four wire terminals. One is for the ground wire... usually indicated by a green "hex-head" screw. The "common" terminal is "differently colored"... usually copper-plated. The other two are what I fondly call the "uncommon" terminals.

To use a three-way switch in place of a single pole switch, connect the wires as follows: 1) Connect the ground wire to the ground terminal on the switch. 2) Connect either one of the two switch wires to the switch's common terminal. Connect the other switch wire to either of the remaining "uncommon" terminals. Whichever uncommon terminal you choose will determine which switch position is ON and which is OFF. Since vertically mounted wall switches usually are ON in the "up" position, stick to this convention so you don't confuse your visitors... or yourself.

If you were to inadvertently attach both switch wires to the uncommon terminals, heaven would not fall from the sky or fire rain on your head... the switch would just not work! But careless mistakes like this are why only the most conscientious people should do their own electrical work!

It is also interesting to note that some companies are now selling dimmer switches that go both ways... single-pole or three-way. More space on the hardware store's shelves for other goodies! Hallelujah!

NH

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