Chicago Circuit

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Mike01

Mike01

Senior Member
Location
MidWest
I know these types of circuits were used durring the depresion, and have been illegal for a long time now I believe 60+ years but having some conservations with a couple of old time retired electricians / engineers I herd the topic of a "Chicago Circuit" it was a way to wire a three-way circuit using only two conductors. Does this sound familiar to anyone, just from a curisoty stand point I have been trying to work this out (on paper, a diagram) but I am clueless anyone have any suggestions or experience with this type of circuit or even a wiring diagram I would like to see how they actually operated. thanks in advance.:)
 
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LawnGuyLandSparky

Senior Member
Very simple. At the bottom of the stair, bring a 2-wire from an outlet to a 3-way switch. Connect hot from the outlet to the 3-way common. Run a 2-wire from the 3-way to the second 3-way. Travellers only. From the 2nd 3-way to the light, connect the common to the light, then use a 2-wire from the light to find a neutral somewhere.

In the end, I don't think any of the installations I've seen saved one bit of copper. What it did save was the electrician from having to purchase any 3-wire cable. Back in the day, 3-wire cable was not common, as a typical home had maybe 4 circuits, and no 220v meant no 3-wire multiwire circuits.
 
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winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
At least the above approach doesn't switch neutral.

An approach used in the era of K+T wiring was as follows:

Run Hot and Neutral to each switch, meaning 2 wires from the receptacle circuit to the switch. Connect H and N to the _traveller_ terminals at each switch. Run a _single_ conductor from the common terminal of each switch to the light.

With both switches connecting N to common, the light is off.

With one switch connecting H to common, and the other switch connecting N to common, the light is on.

With both switches connecting H to common, the light is _off_, but both terminals of the light are energized to 120V.

Clever and evil all at the same time :)

-Jon
 
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haskindm

Senior Member
Location
Maryland
I believe that these were also referred to as "lazy Susan 3-ways", at least in this area. As they switch the neutral, they are no longer a valid wiring method. You have to admit that it is pretty creative!
 
cadpoint

cadpoint

Senior Member
Location
Durham, NC
Let me Blame the Chicago circuit

Let me Blame the Chicago circuit

Well I don't know if it was the the Lazy Susan or the Chicago Circuit.

I had a simple switch at the bottom of the Stair, no Problem my
Church friend says, I can wire you a three way switch with exiting service,
well that got me to think'n, well no I said, thank you just the same.

I found some vocational classes and took all they offered, after one
class year as a Teacher, I had my summer free so I hooked up with a
large EC service. Theres something about Big Pipe and Big Wire, I was hooked.

I just couldn't stand the fact that one, he offered to BS a rig on my
house, and two I didn't understand how he could get it to go on a 3 way
situation. Frankly I can only think that he was going to use the third wire.
I can't recall now, because I removed all the wire that that I could reach
It was 2 circuit Tar weave. circa' 40's.
 
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