ECN Forum Forums General Topics of the Trade General Discussion Area A question

When you want to control lights from two different places (e.g. the top and bottom of a stairwell) you have two different ways of doing it (pic A and B). Some guy told me that B was the American way. Is that right?




[This message has been edited by Webmaster (edited 08-20-2001).]

Kent,

(I hope you don't mind, I had to edit your post to get the picture displayed)

A is the way I've always seen and done it.
(We call it 3 way switching)

I'd have to sit down and look at B for awhile to even figure out what's going on there! Gotta go for now though.

Bill

A is normal and correct. B is is unusual and confused me at first glance too. But see my follow up comments below.


[This message has been edited by Dspark (edited 08-20-2001).]

Kent, this may help; http://www.howstuffworks.com/three-way1.htm

Perhaps someone was just trying to insult Americans by making it far more complicated than it needs to be.

Diagram B looks like something you would see in a Knob & Tube installation. I've also heard it called a "California 3 way."

Tom

http://www.hometoys.com/htinews/apr98/articles/kingery/kingery8.htm

yuppy, Tom is right...

it would be a version of fig#7 in the above link. refered to as a 'french 3-way' .
I have heard it refered to as a 'Chicago 3-way'

actually Kent, the guy who told you it was an American version is right, but it has not been in use for a long time.
It would be hard, in fact, to find a field electrician that actually has installed K&T as a beginner, most are probably retired.

It's comical how these boo-boo's gain names of localities....



[This message has been edited by sparky (edited 08-20-2001).]

>yuppy, Tom is right...
Nopey. It is nothing like figure #7.

>Diagram B looks like something you would see in a Knob & Tube installation.
That could be.

>I've also heard it called a "California 3 way."
No, I think the [Chicago/California/French/etc] three-way is the one with the switched neutral.

I hereby retract my earlier comment that about a Code violation.

I have flattened out the diagram into four parallel lines (one runs only half way). Except for the fact that four wires are required rather than three, it has no problems that I can see.

I wish I could post my redrawing of it.

On a sheet of paper:

1. Draw three parallel horizontal lines and label them as L, T1, T2 from top to bottom.

2. Draw a fourth parallel line under line T2 from the left but of half the length of the previous three and label it N.

3. Install a luminaire between the mid-point of T2 and the end of N directly under this point of T2.

4. Install a three-way switch at each end of T1 (as the common) with each switching between L and T2.

5. Observe that there are no safety violations with this scheme. It simply requires about 1 to 33% more wire.

Both methods are in use in the U.K., depending mainly upon the physical wirng layout.

(A) is the "traditional" method, used almost universally in the past where junction boxes were used to wire up lighting circuits.

(B) is common now, as many houses have lights wired on the "loop-in" principle to avoid the jct-boxes (i.e. permanently live power is taken to the light fitting and a separate cable runs from there to the switch).

With this method an extra jct-box is avoided, as a 3-way (plus gnd) cable then just runs from one switch to the other. Less work in the roof space, but more cable.

It's also known as the "conversion" method here, as it's an easy way to change a normal single switch to 2/3-way operation.