crazy old 3way

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jes25

Senior Member
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Midwest
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Electrician
Guys, I did a service change on a home built in 1925 last Thursday. I get a call on Tuesday that a light bulb is burning out. I find out this condition is because the light has 240v when 1 of the the?3ways is up. When it is down I have 120v on the shell of the light fixture. I was having a very hard time figuring out what the heck was happening and what it had to do with a panel change, if anything. After about 2 and 1/2 hours I figured this out, Both the 3ways have 120v across the traveler terminals and a single wire that goes to the light on the common, the 120v feed is on different circuits. The light functions like a normal 3way as long as the circuits are on the same phase. I don't know how to put drawings on here so draw it out yourself if you wish. Depending on the position of the 3way you have at the light one of these combinations 2 neutrals (off) 2 hots same phase (off) or 1 hot 1 neutral with polarity flip flopping. I put the circuits on the same phase as it worked as it did before. Hope I explained this ok. Has anyone ever seen this, I can think of a few hazards with this set up, I would like to know what hazards you guys can think of with this set-up and lastly what would you tell the homeowner?

Thanks in advance
 
Re: crazy old 3way

If you have two three ways and three conductors to work with, why can't you fix the wiring so that there is only one circuit? Am I missing something?
 
Re: crazy old 3way

EE bob, there is no wiring between the two 3ways and only a 2 wires at the light, There are no travelers just a hot and a neutral that comes from a plug hooked on where the travelers should go. Then we have a single red wire that goes to the light from each 3 way. Depending on the position of the 3way that red wire is hot or neutral. I dont know of anyway to make that work.
 
Re: crazy old 3way

Okay, now I understand what you are describing. Sorry for not understanding it sooner.

I would tell the customer what the problem is and why it is dangerous. of course, convincing someone something is unsafe that has been operating quite nicely is an uphill battle, but that is a battle you should undertake.
 
Re: crazy old 3way

Thanks for the reply, I would still like to here from maybe some old timers, Was this common practice back in the day. Has anyone seen anything like this before, it appears it was done this way when the house was built.
 
Re: crazy old 3way

I've seen it described but have not actually run into it. The commons from each switch go to the fixture. The contacts that we would normally use for the travellers on each switch are wired one to a hot and the other to neutral pulled from wherever the switch may be, apparently each switch is on a different circuit in your case. There are no travellers. Depending on the switch positions the shell, center contact or both will be hot (with the lamp "off") hence the problem.

-Hal
 
Re: crazy old 3way

The circuit is called a Chicago three-way. and was very common with knob& tube, in stairways and between the house and garage, haveing the hot and neutral at both locations gave the installer a way to feed the up stairs or garage. But now it is against code and dangerous. And will be hard to correct with out a way to get more wires up to the other switch.
 
Re: crazy old 3way

I have heard of this once before, glad you were able to figure this one out jes25. What should jes25 do from a contractors standpoint. He can only express in writing the problem he has found but can't make the homeowners change it. Should he just make note of it in his job invoice making it clear to the homeowners that he recommends the problem be fixed.
 
Re: crazy old 3way

Leggo, I must admit I had some help from my partner, without him I would probaly be still be staring at that stupid "chigago 3way" :) :)
 
Re: crazy old 3way

How do you get only 1 conductor leaving the switch box(s) and going to the fixture. What wiring method is employed? If it is any legit wiring/conduit/cable assembly there should be at least one other conductor run with it. No?

To prevent the hazards mentioned you could always set up a "virtual 3-way" with X-10 switches. Providing a constant neutral from switch "A" to the screw shell of the lamp holder, and switching the leg from switch box "B" only. That way there is no danger of the screw shell becoming energized and we are not switching the grounded conductor.

Out west we call this a "California 3-way". Some hacker from Chicago must have come installed a few of these out here too. :)
 
Re: crazy old 3way

Ronaldrc has done alot of work on his site, with some nice drawings!

Click HERE for a link to Ronaldrc's site and scroll down to "Chicago 3-way"

msd, around here, we always referred to a "California 3-way" as feeding a 3-way switch with 2cond., then taking 3cond. up to light box, then 3cond. down to dead-end other 3-way.
Oddly enough, an Amish 3-way uses absolutely no wires at all :D
 
Re: crazy old 3way

jes25,

Good troubleshooting skills! Catching the voltage swings at the fixture is the key.

I'll second Hurk27's comment. This is a three way circuit that was used alot on Knob & Tube wiring. If the house gets back to the Teens and the Aughts and was wired at construction, there's an excellent chance that the installer chose to wire the stairwell in this configuration.

I see 2 to 5 of these a year. There are a lot of dwellings "of this certain" age in the core of The Twin Cities where I work.

I learned when I apprenticed, on a service upgrade, to identify any core K&T circuits and to tag and maintain the bus connections. And if the original 120 Volt 30 Amp service is what's being upgraded, to connect the original circuits back up to only one side of the bus. New circuits would be used to balance the load on the service.
 
Re: crazy old 3way

Yep that link was just like it what I encountered, only difference is my job it was on different circuits, which is how I found out the problem. It is hazardous not only because of reverse polarity but because with my job you can overload the neutral not to mention the shock hazard from servicing it( you think its off but it is just switcing off the neutral)

I like the idea about tagging old wiring and installing them all on same phase. I will make this habit from now on, I would advise we all do.

P.S. This was not K&T wiring. It was cloth wrapped copper inside of a piece of 3/8 steel flex. I see this method a lot in 20's homes here in and around the motor city :)
 
Re: crazy old 3way

This same thread came up a while ago.We concuded that since the shell alternated polarity it was now illegal,grand fathered in but illegal now.Same as using 2wire NM and using the ground as the return and having 2 sw legs it works but....... :D
 
Re: crazy old 3way

Posted by jes25: This was not K&T wiring. It was cloth wrapped copper inside of a piece of 3/8 steel flex.
Click to expand...
That's an interesting one. Since part of what makes this circuit attractive is that only one conductor runs from each threeway switch to the luminaire, I am compelled to ask, are you describing a single conductor in the 3/8 steel flex?
 
Re: crazy old 3way

Al if he didn't look in the attic he might be seeing a BX tap brought down to the switch. I have seen this many times where it will be K&T in attic and between floors and BX taps to outlets and switch's. Very common in city's on older house's around 1920-1940. He will probably have a K&T wires ran close to light then change over to BX at the last knob. same thing close to switches. Strang way of doing it but I have seen it alot
 
Re: crazy old 3way

Wayne,

I've seen my share of BX extensions off K&T, for sure. But all that I recall were wiring added some time after the initial installation of K&T.

Do you recall if any of the K&T / BX installations you've seen looked like they were done at one time? That is, the BX was part of the work done by the guy that placed the K&T?
 
Re: crazy old 3way

Several houses did look like the work was done at the same time and even one that I remember I was told that they had the house built and lived in it ever since and never had any wiring done to the house. Still had the combo gas/wood burning stove in the kitchen. The only addition I could see was a pole barn that had feeders ran from a pole mounted service that also now feed the two 15 amp fuses in the house. well until we upgraded it so it could be sold.
But the most surprising thing was the stairway and up stairs hall was switch/wired like a tunnel setup you flipped the switch at the bottom of the stairs and the stairway light would come on then flip the switch at the top of the stairs the stairway light would go out but the hall light would come on flip the switch at the other end of the hall all lights would be off. any one coming up the stairway again could flip the switch at the bottom and again the stairway light would come on again. This one through me for a loop. I just rewired two 3-ways at the top of the stairs to allow both lights to work independently.
 
Re: crazy old 3way

The thing that impresses me, about the use of BX in the manner that you are describing, is the number of extra splices that would be required when the BX is run only to the knob closest to the outlet. Do you recall how the end of the BX toward the knobs was treated? Were monkey faces used, or just friction tape?

As for the tunnel switching of the stair / hall. . .WOW. I'm jealous. I hope to see things of that caliber.
 
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