So why is it called a 3-way (or a 4-way)?

[iceworm]

This is similar to the situation when you have to correct a homeowner when he incorrectly calls a 3-way switch, a 2-way switch. I've explained the reason numerous times, but they just seem to always get glassy-eyed after I tell them why it's a 3-way switch.

Ya know, that one has been bothering me for at least 35 years. And if there are 3, it's called a 4 way. Somtin ain't right there. What gives?

We can add another 200 posts by asking why we call a switch that is located in 2 places a 3 way switch. Let's not go there...

I'll bite:
Why is a SPDT called a 3-way?

Why is a DPDT with an internal cross connect called a 4-way?

Other than, "That's just the way we do it", I don't have a clue.

ice

 

[K8MHZ]

(I stole this from Bob:roll

One way is to just accept it, the other way takes 300 posts.

 

[K8MHZ]

Actually, 'way' is an obscure ancient engineering term for 'terminal'.

Now does it make more sense?

 

[kwired]

I'll bite:
Why is a SPDT called a 3-way?

Why is a DPDT with an internal cross connect called a 4-way?

Other than, "That's just the way we do it", I don't have a clue.

ice

A layperson might accept 3 way or 4 way more so than 'SPDT' or 'DP reversing', which are both more technically correct.

Technical scares people. You know how many people hook up 3 and 4 way switches on a regular basis that don't even understand how they work? They just learn black goes here, red goes here, and if they run into one configured in a different way than what they learned they are lost.

 

[K8MHZ]

OK, since this is the 'Instructors' section, I should probably be serious.

'Way' is used to indicate the amount of terminals, (ports) that are part of the switch (not including ground). It's the same in hydraulics and pneumatics. A '4-way' solenoid valve will have 4 ports for lines to connect to. Think about it, if there are four ways into the valve, wouldn't it make sense to call it a '4-way' valve? Early electrical designers just adopted the manner of description from the hydraulics field.

No matter how many switches are in a run, the ones with three terminals will be three-ways and the ones with four terminals will be four-ways.

When we use the standard definition of 'way', we think 'direction' or 'possibilities' and that is what makes the subject confusing. The definition we need to think of is 'passageway'.

 

[Gac66610]

Actually, 'way' is an obscure ancient engineering term for 'terminal'.

Now does it make more sense?

So a single pole switch should be called a 2 way?:lol:

 

[Gac66610]

man i type WAY to slow

 

[kwired]

OK, since this is the 'Instructors' section, I should probably be serious.

'Way' is used to indicate the amount of terminals, (ports) that are part of the switch (not including ground). It's the same in hydraulics and pneumatics. A '4-way' solenoid valve will have 4 ports for lines to connect to.

No matter how many switches are in a run, the ones with three terminals will be three-ways and the ones with four terminals will be four-ways.

When we use the standard definition of 'way', we think 'direction' or 'possibilities' and that is what makes the subject confusing.

Hydraulics is just as confusing. What is called a three way valve IMO should still be called two way valve. Incoming media can leave one of two ways. Again IMO. What is called a four way valve IMO should be called a reversing valve (Heat pump manufacturers got this one right).

 

[charlie b]

I have never had a problem with the two phrases. To me, it is similar to driving down a road, and coming to a fork that allows you to go either right or left, but does not have a "straight ahead" option. We call that a "3-way intersection."

 

[charlie b]

What is called a three way valve IMO should still be called two way valve. Incoming media can leave one of two ways.

But that media arrived at the valve via a path that is different from the two it can take as it leaves the valve. There are three "ways" fluid can flow: In, Out-to-the-left, and Out-to-the-right.

 

[K8MHZ]

So a single pole switch should be called a 2 way?:lol:

Yes.

But we don't, which adds to the confusion.

 

[K8MHZ]

But that media arrived at the valve via a path that is different from the two it can take as it leaves the valve. There are three "ways" fluid can flow: In, Out-to-the-left, and Out-to-the-right.

That is not why the term is used.

'Way' (the way we use it for switches) is from the Old English word 'weg' or the road to a town. The term 'highway' is derived from that particular use of 'way', so is roadway, passageway and particularly, entryway (portal).

It really makes more sense with valves. It may have been a poor choice for switches but that is what we are stuck with and how it came to be.

 

[K8MHZ]

Hydraulics is just as confusing. What is called a three way valve IMO should still be called two way valve. Incoming media can leave one of two ways. Again IMO. What is called a four way valve IMO should be called a reversing valve (Heat pump manufacturers got this one right).

If you have had some training and experience in hydraulics you would find that it's not that confusing.

I remember starting out as a maint. tech in a foundry that a bunch of presses. Looking at the hydraulic schematics was like looking at hieroglyphics. I had a grumpy boss that knew all about the valves and started teaching me about them. I also went to Parker-Hannefin's course on industrial hydraulics. After that, I could look at the schematics and know exactly what I was looking at.

It's really not rocket surgery.

 

[texie]

OK, since this is the 'Instructors' section, I should probably be serious.

'Way' is used to indicate the amount of terminals, (ports) that are part of the switch (not including ground). It's the same in hydraulics and pneumatics. A '4-way' solenoid valve will have 4 ports for lines to connect to. Think about it, if there are four ways into the valve, wouldn't it make sense to call it a '4-way' valve? Early electrical designers just adopted the manner of description from the hydraulics field.

No matter how many switches are in a run, the ones with three terminals will be three-ways and the ones with four terminals will be four-ways.

When we use the standard definition of 'way', we think 'direction' or 'possibilities' and that is what makes the subject confusing. The definition we need to think of is 'passageway'.

Interesting explanation. I also am involved in hydraulics from time to time, but I never thought about the connection to electrical terms. Makes sense. In the hydraulic world the terms always seemed intuitive, but now that you mention it I see the connection to 3 and 4 way switches.

 

[K8MHZ]

Interesting explanation. I also am involved in hydraulics from time to time, but I never thought about the connection to electrical terms. Makes sense. In the hydraulic world the terms always seemed intuitive, but now that you mention it I see the connection to 3 and 4 way switches.

I probably would have stayed with hydraulics except they are so nasty to work on. And, they CAN kill you. We ran intensifiers that could deliver 11,000 psi into a 1 inch pipe or hose. Working pressure was 5 to 6 thousand. I saw a hose blow up that would have cut a person in half one day.

I remember coming to work one day wearing a brand new pair of steel toed work boots. I was on second shift taking over for first. I was helping about three other guys trying to pull off a 4 inch fitting from the bottom of a die cast unit. Finally, when it broke loose, about 35 gallons of glycol based hydraulic fluid came shooting out, soaking one of my boots, actually immersing it, with glycol.

Glycol doesn't evaporate like water does.

 

[480sparky]

From an early 'teens Arrow-Hart catalog:

 

[ritelec]

Why is it said to be a 3-way system or 4-way system.

Would not a 3-way system be a 6-way system and a 4-way system an 10 way system.


What would the switching system be called after 4-way (3 switches)........4 switches....5 switches....6 switches...and so on???

 

[K8MHZ]

Why is it said to be a 3-way system or 4-way system.

Would not a 3-way system be a 6-way system and a 4-way system an 10 way system.


What would the switching system be called after 4-way (3 switches)........4 switches....5 switches....6 switches...and so on???

Did you read post #5?

Also, we are talking about switches, not systems.

 

[ritelec]

No matter how many switches are in a run, the ones with three terminals will be three-ways and the ones with four terminals will be four-ways.

post #5. Yes...



Can we talk about switches in a run now? eg. system?

Actually can you talk.............I'll listen...........?

 

[dkeaux@gmail.com]

I'll bite:
Why is a SPDT called a 3-way?

Why is a DPDT with an internal cross connect called a 4-way?

Other than, "That's just the way we do it", I don't have a clue.

ice

Terminal count on the switch