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.

Thanks for your help. A good thing with B is that you have a “unbroken” phase at both ends. It can be useful when doing a exposed installation using cables. We often mount a socket together with the switch so we also need a neutral and a ground wire. With this variant you can do that with a standard 5-wire cable. Otherwise you need 6 wires which practically means 2 cables (or some sort or special cable).

Can you tell me more about this a Knob & Tube method? I remember seeing a picture in our Union paper. It looked like 2 bare cooper wires which run over a attic.

>[knob and tube] looked like 2 bare copper wires which run over a attic.

I've never seen them bare indoors though the insulation may be rather deteriorated, that was not intentional.

Even outdoors, they usually started off insulated/covered, at least the hot wire was.

Kent:

I assume from this that you follow the usual European (& American) practice of mixing lights and sockets on the same branch circuit.

Would I be right in thinking that you use 16A fuses or breakers for each branch?

Do you have rules specifying the maximum number of outlets per branch, or is this left to the discretion of the electrician?

Pauluk

I assume from this that you follow the usual European (& American) practice of mixing lights and sockets on the same branch circuit.

You assume just right.


Would I be right in thinking that you use 16A fuses or breakers for each branch?

16 Amp is a very common size for main fuses. If you have a house which in heated with electrical radiators you may have 20. 10A are the standard fuse for light branches. Thanks to the 3-phase system we don’t need more. I get a bit confused when you say fuses or breakers. Do you sometimes use breakers (breaker is a type of switch in my World) instead of fuses?

Do you have rules specifying the maximum number of outlets per branch, or is this left to the discretion of the electrician?

It’s up to you. But you don’t want to blow the fuse when the whole branch is used so you have to spread them.

You're referring to the main service fuse for each phase, right? If so, this sounds like some of the houses I've seen in France with a max. of just 15 or 16A per phase.

If this is normal, I can certainly understand why most cookers, stoves, etc. are designed for 3-phase supply over there. I imagine you have to be pretty careful about assigning phases for big appliances such as washing machines as well.

I take this to mean that your general-purpose sockets are also fused at 10A. I thought the Schuko sockets you use were rated 16A.


Sorry, maybe I'm confusing you by using abbreviated English. What I'm referring to here are "circuit breakers," often written as "C/B." These are overload protection devices used instead of fuses, and which when tripped are reset by pressing a button or switch handle. I'm sorry I have no idea what the Swedish name is for these!

The types used in homes here are called MCB (Miniature Circuit Breaker). They have been available here for decades, but have only become widely used in residential panels in the last few years.

Pauluk

You're referring to the main service fuse for each phase, right?

Yes, 16 A per phase is the most common size for a ordinary Swedish house. If 16 isn’t enough you can raise it to 20 or 25. But this will cost you more. Bigger fuses equals higher rate.

I imagine you have to be pretty careful about assigning phases for big appliances such as washing machines as well.

Not so much in the domestic sector. You can come across some Water pumps (if the house have it’s own well), bigger types of radiator pumps or ventilation fans. Otherwise it’s mostly in the industries you have to think about it. You mentioned washing machines. Washing machines built for 3-phase 400V (which are becoming more and more rare) have single phase motors so direction of rotation it’s not a problem. Overall, appliances that used to be 3-phase 400V are now often made for single phase use (a adjustment to the rest of Europe I think). It’s s both good and bad.

I take this to mean that your general-purpose sockets are also fused at 10A. I thought the Schuko sockets you use were rated 16A.

They are approved for 16A. But it’s not common that you actually run 16 A over them. Only if they are intended for some special use.

Circuit breakers. Now I get it. They are very common here to. Joe public calls them Automatic Fuses (every type of fuse are automatic if you thinks about it). Dwarf Breaker (direct translation) is the more correct term. They can be rather tiresome to work with. It’s not so easy to change them (change size) compared to a “melt fuse”. They are more sensitive and can sometimes start to malfunction and it’s so easy to “flip” them over with your arm when working in a “hot” panel.

That sounds like France too. We don't have higher charges for a larger service here. To us, it just seems a little strange, because we're used to having 60 to 100A available on a single phase.


I've been noticing the opposite with cooking appliances here. Our stoves used to be always wired for 1-ph. input. Now that we're seeing models which are sold right across Europe, many have provision for 3-ph. input. We just strap all 3 line terminals together, of course.

By the way, if you used to have 3-phase washing machines, I assume that they incorporate a heating element. Most machines here have a 3kW heater, but I think the majority of American washers rely on getting hot water from the house system. (Maybe one of our U.S. friends can confirm?)


Non-technical people here often call them "trip switches."

>many have provision for 3-ph. input. We just strap all 3 line terminals together, of course.
Basically the elements are wired in parallel. Our electric dryers and water heaters use the higher voltage found between phases.

>American [clothes] washers rely on getting hot water from the house system.
Correct.


[This message has been edited by Dspark (edited 08-23-2001).]