Weird (and Illegal !) 3-way Switch

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kwired said:
. . . whether or not the intent for prohibiting small parallel conductors is limited to paralleling them for the purpose of making an effective larger current carrying ability conductor or if it is allowed for certain control schemes - which this "parallel" is for control scheme more so then for current carrying ability. . .
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This is all confusing. NEC language is all we have, and it, by itself, gives no exception (in my humble opinion), especially because, in every real world case of finding the California (Traveling Bus) switching scheme, the Hot and Neutral have extended on into the room at the end of the hallway, or extended to the additional lights and receptacles of the garage. . . so the use is not purely "control".

I'm torn, 'cause the engineer in me really likes the gimmickry of the California (Traveling Bus). I've liked using this scheme in the past.
 
flashlight said:
So is the three-way I described (and 480sparky drew) called a Chicago 3-way ?
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:thumbsup:

Yes. Some also call it a Carter.

Carter%203%20Way_zpsllzulti0.jpg
 
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electricalist said:
If there is a 4 way involved does it function as a 4 way or can the hot and neutral be introduced there?
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Thinking about the image I just posted. . . I believe you could use a 4 way, or 4 ways. They would be placed OUTSIDE the 3 way to 3 way connection of the Common - Light - Common.

Now, that said, I am leery what the real world experience would be with real 4 way switches. The 4 way switch is reversing the connection of the hot and neutral travelers, and all it takes is for the switch mechanism to momentarily connect traveler to traveler to get a plasma arc. I doubt the 4 ways are tested (or even designed) with this in mind, and have to wonder if putting the hot and neutral on travelers isn't a 110.3(B) or NRTL violation for the 4 way switch.

In the real world of all the K&T installations I've worked on, I have never seen a 4 way used in a Chicago (Carter) 3 way switching scheme.
 
K that's what I was needing to know.
Customer has house that was wired by a supposed electrical guru and I'm not sure what era. Al ser ,copper branch,2 wire plugs,switches that are push button.
If breaker A is off and lights on breaker B are off ,,breaker A light light up dim.
Switches are 1 3 way & 4 way other room the same.
Both breakers same phase.
 
I was just kidding on the last 2 posts.
I took a pic of the 4 way. It had a neutral to one screw and the black taped unused. The cable was coming in the bottom of the box by its self.
 
Al,that's a nice illustration for the Carter 3-way--
Do you know the source and what year it is from ?
 
flashlight said:
Al,that's a nice illustration for the Carter 3-way--
Do you know the source and what year it is from ?
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All I did was Google "Carter 3 way" in the images section of Google and the mock up with the two physical switches was the one that caught my eye. It is of uncertain provenance and is used by an "Ask the Electrician" type of site that you can find by clicking here.

As for its age, it can't be all that old. What I liked about it is that the Hot and Neutral at each switch are not tied together, which, in my experience, is the core of what to watch out for when landing branch circuits in a new panel.
 
I checked out that linked "ask the electrician" website--

Looks a little dangerous, sounds like the questioners don't really have a clue.
 
al hildenbrand said:
Now, that said, I am leery what the real world experience would be with real 4 way switches. The 4 way switch is reversing the connection of the hot and neutral travelers, and all it takes is for the switch mechanism to momentarily connect traveler to traveler to get a plasma arc. I doubt the 4 ways are tested (or even designed) with this in mind, and have to wonder if putting the hot and neutral on travelers isn't a 110.3(B) or NRTL violation for the 4 way switch.
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I would have no problem using the 4 way switches. I have used miniature toggle switches for motor reversing before and if they can handle it I don't see why your typical 4 way wall switch can't handle it. If it fails it trips overcurrent device just like it does when a single pole switch is closed into a fault. (the switch may need replaced afterward though).
 
The OP wiring, I guess it's the Carter, only works with old push-button switches because they are break-before-make. My original employer told me this was because they were designed to open both AC and DC circuits so they have a strong snap. Modern switches are designed with weaker springs because they open the AC current at the lower end of its cycle, when the fields are weak. So they are "make-before-break" and will thus blow up when they switch this arrangement.


The first time we ran into this on a job (old victorian , 1980's in San Francisco) when I was an apprentice was completely confusing.
 
edlee said:
The OP wiring, I guess it's the Carter, only works with old push-button switches because they are break-before-make. My original employer told me this was because they were designed to open both AC and DC circuits so they have a strong snap. Modern switches are designed with weaker springs because they open the AC current at the lower end of its cycle, when the fields are weak. So they are "make-before-break" and will thus blow up when they switch this arrangement.


The first time we ran into this on a job (old victorian , 1980's in San Francisco) when I was an apprentice was completely confusing.
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I haven't taken any three way switches apart in a long time but all those I recall taking apart I don't see how it is physically possible for it to make the new connection before it breaks the old one - unless something is damaged - then you have problems anyway.

I can see a issue if contact clearance is minimal and maybe having a flashover event - particularly if a carbon coating has accumulated over time.

Four way switches - I can see being a bigger problem if both "poles" are not close enough in sync with one another and one makes before the other breaks
 
In my experience, working with various manufacturers 3 way switches, when the travelers are hooked up to an unswitched hot and a neutral, the normal flipping of the toggle would occasionally blow the overcurrent protection. No rhyme, nor reason from the outward appearance. The arc in the switch tended to turn the switch into a useless electrical state.

In my work area, Honeywell Controls was a big deal. Honeywell marketed a silent toggle switch, the mechanism of which centered on a metal and glass ampule partially filled with mercury. Other manufacturers made similar switches and they were heavily marketed to the do it yourself community.

Silent%20Mercury%20Switch%20Innards_zpsmbkdwjtu.jpg


The mercury ampule is in the lower left of the photo, between the copper bus straps.

Those suckers ALWAYS blew when someone attempted to use them with a Chicago (Carter) 3 way.
 
kwired said:
I haven't taken any three way switches apart in a long time but all those I recall taking apart I don't see how it is physically possible for it to make the new connection before it breaks the old one - unless something is damaged - then you have problems anyway.

..........
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You are probably right and my employer was probably wrong. I just took his word for it and never gave it much thought! Likely there aren't any toggle switches that are make-before-break, except maybe those mercury-filled silent ones. Which are nice BTW!

So my guess is that the problematic sparking is due to the softer spring mechanism of the modern AC switch, compared to the old AC/DC PB switches.
 
edlee said:
You are probably right and my employer was probably wrong. I just took his word for it and never gave it much thought! Likely there aren't any toggle switches that are make-before-break, except maybe those mercury-filled silent ones. Which are nice BTW!

So my guess is that the problematic sparking is due to the softer spring mechanism of the modern AC switch, compared to the old AC/DC PB switches.
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Arcing is normal during make or break, but extinguishing the arc after breaking contact is a bigger issue for DC then it is for AC.

AC has zero voltage crossing every half cycle and this helps with arc extinguishing, where a steady DC voltage is has no zero voltage crossing.
 
flashlight said:
So is the three-way I described (and 480sparky drew) called a Chicago 3-way ?
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Monikers include Chicago, Carter, California, Farmer, Handyman, Illinois, Power Beyond, Homeowner, DIY, Hot-wired, Husband, Three-Wire-Hot, Switchback, and my personal favorite, Who-cares?-It works,-and there's-no-inspection!.
 
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