why is a 3way sw called a 3way not a 2way

[K8MHZ]

Do not get me wrong schooling is important, and on this issue you might be right. But so many of the young apprentices have misconceptions about the trade that originate with misinformation provided by their instructors.

Yeah, like Edison invented the light bulb and Marconi made the first radio.

Edit: And you can't have a step up or step down transformer using DC.

(Swan invented the light bulb, Tesla made the first radio and take a look at the coil in your car....)

 

[CCCI]

It is from England

It is from England

I was told many years ago that we got the name from England. In England they call a "WIRE" a "WAY", so they used the name 3 WAY or what we should be calling it is a 3 WIRE switch.
England = 3 Way
America = 3 Wire

 

[iaov]

I was told many years ago that we got the name from England. In England they call a "WIRE" a "WAY", so they used the name 3 WAY or what we should be calling it is a 3 WIRE switch.
England = 3 Way
America = 3 Wire

This is about the most likely/logical explanation I've heard for the nomenclature of these devices.:smile:

 

[dwcaveney]

Delete 2 way switch

 

[dwcaveney]

blah....blah....blah

blah....blah....blah

The reason a three way is called a 3-way is because, 2 SPDT switches can be connected in a fashion to form either a two way or a three way switch. (both controling one load with two switches)


THE INFORMATION BELOW DESCRIBES A TWO WAY SWITCH
An unrecommended method of controlling a load with two switches:

The unrecommended way using the hot and neutral directly. If there is a hot (a unique phase) and a neutral wire in both switches and just one wire between them where the light is connected, you can then solve the two way switch problem easily: just plug the hot in the top from switch, the neutral in the bottom from switch and the wire that goes to the light in the middle from the switch. This in both switches. Now you have a fully functional two way switch.

There are four possibilities and just in two of them there is a hot and a neutral connected in the poles of the light. In the other ones, both poles are neutral or hot and then no current flows because the potential difference is zero.

The advantage of this method is that it uses just one wire to the light, having a hot and neutral in both switches.

The reason why this is not recommended is that the light socket pins may still be hot even with the light off, which poses a risk when changing a bulb. Another problem with this method is that in both switches there will be hot and neutral wires entering a single switch, which can lead to a short circuit in the event of switch failure, unlike the other methods.

This method is in defiance of the NEC and the CEC. In nearly any and all applications, neutral conductors should never be switched. Not only is this a shock hazard due to mistakenly believing that a hot conductor is switched off; it is also a fire hazard and can destroy sensitive equipment due to excessive and unbalanced current flowing on hot conductors that would outherwise flow back to ground on the neutral conductor.

DON'T MESS WITH A+

 

[480sparky]

The reason a three way is called a 3-way is because.

If I'm reading this right, this is what you have:

We call them California-, Indiana-, Farmer-, etc- three ways.

I see nothing in your description that give a reason why they're called a 3-way.

 

[dwcaveney]

NO sparky!

The OP was "why is a 3way sw called a 3way not a 2way"
First you have to understand what a two way switch is.

Change your picture and control a load with two SPST switches, not two SPDT switches. OK?

Regards, I like your picture

 

[480sparky]

NO sparky!

First you have to understand what a two way switch is.

Change your picture and control a load with two SPST switches, not two SPDT switches. OK?

Regards, I like your picture

I don't see how it would work with two SPST switches. If one is open, then the circuit is open.

You also state to hook up one wire to the top of the switch, the other to the bottom, then the wire that goes to the light in the middle. That makes three terminals. SPST switches only have two.

 

[dwcaveney]

Oh sorry sparky,
The SPST was wrong, darn it.

I meant to say a three way switch is a three way switch. And a two way switch is a two way switch, which I describe in my first post.

But I made a mistake because, I said "a two way switch is a two way switch"
And I should have said that, "a two way switch is a two way switch"

Let me put it another way: It's the method in which two SPDT switches are wired that make a two way switch versus a three way switch.

And because a two way switch is no good, the correct method to control a load with two switches is a three way switch.

A dog can have the name "Cat" but it's still a dog.

DON'T MESS WITH A+

 

[480sparky]

And because a two way switch is no good, the correct method to control a load from two switches is three way switch.DON'T MESS WITH A+

Now I'm thoroughly confused. What is a 'two-way' switch then?

 

[mivey]

dwcaveney,

When you edit your posts, it would be nice if you noted what you changed if it has been posted long enough to get an edit note: Someone may have already read your pre-edited post. Little things like spelling errors aren't such a big deal, but if you change the content, make a note of it or just type something new in an edit section.

This way, someone will know if they need to re-read your post. Also, someone's response may be based on your original content and it can confuse those who read the thread later.

 

[dwcaveney]

Now I'm thoroughly confused. What is a 'two-way' switch then?

Post #65 describes a two way switch.

 

[480sparky]

Post #65 describes a two way switch.

A SPDT? Then that's what we call a 3-way.

 

[mivey]

Now I'm thoroughly confused. What is a 'two-way' switch then?

I'm not sure what he means.
pole = # contact sets
throw = # conducting positions
way = # conducting paths

 

[mivey]

A SPDT? Then that's what we call a 3-way.

I guess if you can flip the switch THIS way, then THAT way, he is saying it is 2 ways = 2-way switch?

[Add: THIS & THAT way with something being connected through the switch]

 

[dwcaveney]

DELETE

 

[480sparky]

A three way switch is a system that controls a load with two switches.

It just so happpens that two components of the switching system are SPDT switches.

But I'm still confused!​

You call a switch with 3 terminals a two-way switch. If it's not a SPDT (3-way), then what is it?

Please understand I'm not being argumentative, but I'd just like to get my brain wrapped around what you mean by 2-way.

I know a lot of DIYers call 3-ways two-ways, because our terminology confuses them.

 

[jerm]

offtopic

offtopic

GO AHEAD MESS WITH A+

Does anyone know what that means?

[edit: post 69 is useless.]

[edit: please note your edits. your posts aren't making any sense.]

 

[jerm]

If it's not a SPDT (3-way), then what is it?

I thought a single pole double throw switch had four points on it. A threeway only has three points. Wish I had a good graphics program, I'd draw a little picture.

 

[roger]

dwcaveney, it is not proper etiquette to edit your posts after they have been replied to. When a post appears after one of yours your post is what it is and should be left alone.

Roger