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#127692 - 10/15/01 11:53 AM Four wire feed through 3way switching +
tdhorne Offline
Member

Registered: 03/22/01
Posts: 344
Loc: Maryland, USA
This is kind of a quiz question that I enjoyed learning the answer to. I posted it in another forum some time ago and folks there got some fun out of it.

You have been asked to install outdoor area lighting to light the walkway between the door to a farm house and a barn; or any house and outbuilding for that matter. Here is the situation that you find at the customers premise. There is a existing conduit between the two buildings and it contains four conductors not including any equipment grounding conductor. The second building has an outside light over the door that lights the area immediately around it. This outside light is controlled by 3 way switching at the house and barn. The circuit also supplies the interior lights in the barn and a few convenience outlets. The block heater for a tractor that is used to plow snow and power take off equipment when needed is plugged into one of the outlets. The convenience receptacle outlets must remain energized at all times. The interior lighting at the barn must be switched at the barn independently of the outside lighting. There is no need to control the interior lighting from the house. The customer wants area lighting at both buildings that can be turned on or off at either door. How do you wire the circuit without repulling the conduit or violating the US NEC. In order to make the issue really clear the customer has specified that the lighting must be instant on and you already have the flood light fixtures on the truck. The fixtures are screw shell, edison based, flood heads.
--
Tom
_________________________
Tom Horne

"This alternating current stuff is just a fad. It is much too dangerous for general use" Thomas Alva Edison

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#127693 - 10/15/01 02:50 PM Re: Four wire feed through 3way switching +
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
Hmm, already 4-wires house to barn. As there is permanently live power out there, two wires must be neutral and hot, and I assume the remaining two are the travelers for a conventional 3-way switching circuit.

I'm not quite sure whether you meant that the new outside lighting had to be switched separately from the outside lights already present, or whether all the outside lights can go on and off together on the same pair of 3-way switches.

The latter could be done thus:

Obviously the hot & neutral have to stay as they are.
Connect pos. 1 of house switch and pos. 1 of barn switch to hot wire. Use third wire in conduit to join commons of the two 3-way switches. Use fourth wire to join pos. 2 of one switch to pos. 2 of other, then wire the light fittings between this wire and neutral at each end (or anywhere else along the run as needed).

If the added lights are to be switched separately, I can see a way to do it, but it would result in the outer shell of Edison lamp-holders being hot in certain switch positions, which I assume would be in violation of the NEC.

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#127694 - 10/15/01 05:28 PM Re: Four wire feed through 3way switching +
sparky Offline
Member

Registered: 10/18/00
Posts: 5545
Tom,
can I cheat ???..........
A lev # HCS10-1SW & HCC10-1SW can operate as a 3-way with the same H & N at either end, maintaining the constant H & N for the garage interior & recptacles. so i can do it in 2 wires ( given a mettalic EGC raceway)

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#127695 - 10/15/01 06:01 PM Re: Four wire feed through 3way switching +
Redsy Offline
Member

Registered: 03/28/01
Posts: 2138
Loc: Bucks County PA
Pauluk,
It works, but I would hesitate to do it. I try to avoid unconventional configurations. It just doesn't sit well with me.

sparky,
Could you please elaborate on your devices and connections?

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#127696 - 10/16/01 09:42 AM Re: Four wire feed through 3way switching +
ElectricAL Offline
Member

Registered: 10/10/01
Posts: 615
Loc: Minneapolis, MN USA
Parts of this Metropolis are wired in old heavy wall flex, '50 - '75, (1975 was when the "all metal" local code was relaxed to allow NM, and I have found numerous hallway / stairway installations of this 4 - wire setup in high end homes.

When I was apprenticing I was taught this 4 -wire arrangement was called a "California Threeway".

Anyone got other names for it, or for that matter, the true meaning of California Threeway if this is not it?

Al
_________________________
Al Hildenbrand

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#127697 - 10/16/01 12:59 PM Re: Four wire feed through 3way switching +
tdhorne Offline
Member

Registered: 03/22/01
Posts: 344
Loc: Maryland, USA
pauluk
I have to admit that I am disappointed that you solved it so quick. I ran the same thing on a BBS with some pretty sharp electricians and it took two days to get that response.

Redsy
Every new technique we come up with is unconventional when first done. I have never met an electrician who was familiar with every technique in the industry but I have met some who thought they new it all.

Additional challenge! The customer is thrilled with the results and now wants additional switches at the side door to the house and a second door at the barn. Can it be done and how? Let's accept that you have a good supply of switches on the truck and even rolls of multi wire cable.
--
Tom

[This message has been edited by tdhorne (edited 10-16-2001).]
_________________________
Tom Horne

"This alternating current stuff is just a fad. It is much too dangerous for general use" Thomas Alva Edison

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#127698 - 10/16/01 01:12 PM Re: Four wire feed through 3way switching +
tdhorne Offline
Member

Registered: 03/22/01
Posts: 344
Loc: Maryland, USA
Sparky
No electronic controls allowed. The challenge is to do it with materials that you would normally have on the truck such as "snap" switches. I think it is fair to say that most of us do not normally carry expensive electronic controls on the service van or truck.
--
Tom
_________________________
Tom Horne

"This alternating current stuff is just a fad. It is much too dangerous for general use" Thomas Alva Edison

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#127699 - 10/16/01 02:36 PM Re: Four wire feed through 3way switching +
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
Tom,
I probably had an unfair advantage because the basic configuration I described has become increasingly common in England, although usually for feeding only one light.

Re "Additional challenge." Are we allowed to assume 4-wire plus ground cable and intermediate (4-way) switches are available in the truck?


[This message has been edited by pauluk (edited 10-16-2001).]

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#127700 - 10/16/01 02:52 PM Re: Four wire feed through 3way switching +
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
Al,

The "California 3-way" is sometimes called the "conversion method" here, as it' an easy way to change a regular 1-way light into 3-way switching. Just run a 3-wire (plus gnd) from the existing switch to the new position, change he 1-way for a 3-way and "Voila!"

It could be done othe conventional way with a wire joint in the box, but this configuation means that all wires teminate at switch terminals so no extra splice is needed.

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#127701 - 10/16/01 05:40 PM Re: Four wire feed through 3way switching +
sparky Offline
Member

Registered: 10/18/00
Posts: 5545
Redsy,
Tom bagged me with the fancy Leviton electronic switches , i assume that answers that...

Al,
why blame the Califorians? I've heard it called 'French 3-way'..

Tom;
would the American Electrical Handbook 4:34 figure #2 do? ( with appologies to Paul..)

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