trolley systems

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I'm certain among so many experienced electricians many of you have heard of a "trolley system". I live in an area with many older homes and knob and tube wiring is a daily sight. It is my understanding the trolley system is an "ancient" method for running three way lighting. I recently heard of this and was wondering if someone could explain the how it works, why it was used and is it legal by todays code standards. Thanks
 

infinity

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Journeyman Electrician
The only trolley system that I've ever heard of is on a type of busway. There are trolley type busway systems where the connection to the busway is movable.
 

mdshunk

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Right here.
The only trolley systems I'm aware of are overhead trolley conductors referenced in older versions of the code for actual power to streetcars and trolleys. The other one it the ITE/Bulldog trolley busway system, used for movable equipment power from an overhead trolley buss in a factory.

I think you might be talking about the "Carter System", sometimes called "Chicago 3-ways". Maybe?
 
Marc, your right, just after I posted that question, I was reading other posts, one was titled "switching question". It has two drawings and chicago 3-way is mentioned. I am slightly confused, it looks as though the two three ways are fed from seperate sources. Is that correct?
 

don_resqcapt19

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Illinois
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retired electrician
I am slightly confused, it looks as though the two three ways are fed from seperate sources. Is that correct?
Sometimes they were....I found out the hard way on a service up grade from 30 amp 120 volts to 200 amp 240...when we finished the the two circuits feeding the 3 ways were on opposite legs. Lamps don't last long at 240.
Don
 

donselec

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Location
Aurora, CO, USA
Ah, the Chicago 3-way. We always called the "Indiana 3-way" for some reason. It's been used here in Denver in the old days many times. You have a house and a detached garage. The only service entrance is on the house. There's a 3-way switch and one back porch light on the house, and there's a 3-way switch and outside light on the garage. There's an outlet in the garage that works all the time. Both lights go on and off together, and can be controlled from the house 3-way or the garage 3-way. There are 4 single conductors going overhead from the house to the garage, and none others. None of them is an equipment grounding conductor. I figured it out once but would have to sit down and figure it again. Maybe someone else has posted the solution. Otherwise it's a good mental exercise. Who can do it? :)
 

LawnGuyLandSparky

Senior Member
Neutral from house connects to house porch light, and then out to the garage receptacle neutral and the outside garage light neutral.

Hot conductor from house connects to house 3-way switch traveller #1, and continues on to the garage and connects to garage 3-way switch traveller #1 and the receptacle hot.

Conductor #3 connects the house 3-way common to the garage 3-way common.

Conductor #4 connects the porch light to the house 3-way switch traveller #2 and then out to the garage where it connects to 3-way traveller #2 and the garage light.
 

mdshunk

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Right here.
Animation of the "Carter System":

carter-1.gif
 

480sparky

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Iowegia
I've also heard them called "California three-ways" and "Farmer three-ways". I'm sure there's scores of other vernacular terms for it.
Maybe this drawing will help: (Any grounding conductors that may be present are deleted for simplicity's sake)
3way.GIF


Both the grounded and ungrounded are hooked to the 'traveler' terminals on both 3-ways. The 'commons' are run to the light. If one 3-way is positioned to connect to the grounded, and the other to the ungrounded, the light will turn on. If both switches are connected to either the grounded or ungrounded at the same time, the light goes off.
I can't begin to list the Code violations shown here.
 

480sparky

Senior Member
Location
Iowegia
LawnGuyLandSparky said:
The last 2 posts show systems that are violations. The 4-wire system I describe is code compliant.

Hence my disclaimer:
480sparky said:
I can't begin to list the Code violations shown here.

But we're trying to answer the OPs request for how these systems work. They're still out there, and I posted the image to not only inform the OP how they work, but for everyone to understand what can happen if you run across one. Imagine getting a service call to replace the fixture. You 'turn off' the light with one of the switches, buy you can have both wires energized with 120 volts.

I like mdshunk's animation better! Makes me wish I had thought of it.
 
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donselec

Senior Member
Location
Aurora, CO, USA
LawnGuyLandSparky said:
Neutral from house connects to house porch light, and then out to the garage receptacle neutral and the outside garage light neutral.

Hot conductor from house connects to house 3-way switch traveller #1, and continues on to the garage and connects to garage 3-way switch traveller #1 and the receptacle hot.

Conductor #3 connects the house 3-way common to the garage 3-way common.

Conductor #4 connects the porch light to the house 3-way switch traveller #2 and then out to the garage where it connects to 3-way traveller #2 and the garage light.
LawnGuy you're the only one who got it right so far. Your system is more legal, although it still violates some codes, disconnect on the garage, grounding conductor, etc. But back in the old days they didn't worry about that stuff. The other 2 sketches only show 3 wires, one light on the garage, and are illegal, even though they work. Here's a rough sketch I drew up of what your were talking about, and it seems to work. Congrats on getting it!
Indiana3-way.gif
 
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