Thread: Why "3-way" if only 2 switches?

I know we call two switches on a light 3-way, and yes the switches have 3 terminals. It just bugs me to have to explain the term, yes there are two switches, not three.
I want to call it "Two-way switching", but then Sparkys will laugh at me and that is bad for my ego and makes me look like an amateur.

So the condo from a couple of days ago had "4-way" switching. There are 3 switches on an L-shaped hall operating two hall lights. If the switch by the entry is in the 'on' position, the other 2 switches operate. If the lights are switched off at either of those switches, none of the switches work. If the entry switch is in the off position, none of the switches work.

I'm pretty sure two wires are crossed and it's an easy fix. The common wire is being switched off. Rather than say "you got 4-way switches" (only one of the 3 switches has 4 terminals. The other 2 have 3. Get it?), I said "There are 3 switches for the hall lights."
I can't call it "3 way switching", because that would mean 2 switches. Get It? It's all stupid.

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Originally Posted by John Kogel

If the switch by the entry is in the 'on' position,...
... If the entry switch is in the off position,...

Is the "on position" up or down?
What about the "off"?

John,
Try explaining 3 way switching as counting 1on + 1 off + 1 on (for each additional switch).

So 3-way is: 1on+1off+1on=3ways,,,,
.....4-way is: 1on+1off+1on+1on= 4ways.
and so on...

Something people can understand

Originally Posted by John Kogel

I know we call two switches on a light 3-way, and yes the switches have 3 terminals. It just bugs me to have to explain the term, yes there are two switches, not three.
I want to call it "Two-way switching", but then Sparkys will laugh at me and that is bad for my ego and makes me look like an amateur.

So the condo from a couple of days ago had "4-way" switching. There are 3 switches on an L-shaped hall operating two hall lights. If the switch by the entry is in the 'on' position, the other 2 switches operate. If the lights are switched off at either of those switches, none of the switches work. If the entry switch is in the off position, none of the switches work.

I'm pretty sure two wires are crossed and it's an easy fix. The common wire is being switched off. Rather than say "you got 4-way switches" (only one of the 3 switches has 4 terminals. The other 2 have 3. Get it?), I said "There are 3 switches for the hall lights."
I can't call it "3 way switching", because that would mean 2 switches. Get It? It's all stupid.

John,

For three (or more) location switching to work, you require a 3-way switch at the both the beginning and the end of the switching loop (the origination and the termination of the "traveler" conduductor for the switch loop circuit) and 4-way switch(es) (at least one in the center) in between those 3-way switches. 4-way switches have two traveler terminals - the traveler must be wired through the intermediate switch(es) between the originating and terminating 3-way switches in the switch loop. The traveler (in the switch loop) and the switch loop itself must make or break the HOT, not the common (neutral).

Think of the number of contacts for the switch device (not including ground): 3-way has 3-contacts (plus ground), 4-way has 4 contacts (plus ground).

The "common" or neutral should not be being switched the traveler should be the conductor being switched. Modern rules (here, at least) require supplying a common (or a neutral) to (and if necessary through) all switch locations (to provide for lighted switches, occupancy sensors, etc.) gone are the days of "re-identifying" a neutral (or common, or 'return) of 2-wire plus ground multi-conductor cable for use in 3-way plus (two locations or more) switch loops, there are a host of multi-conductor cables available on the market which accomodate legal (and no re-identifying) multi-location control switch loops.

HTH.

Originally Posted by Rick Cantrell

Is the "on position" up or down?
What about the "off"?

"ON" is up here, but why does it matter to anyone that doesn't live there?

Originally Posted by Garry Sorrells

John,
Try explaining 3 way switching as counting 1on + 1 off + 1 on (for each additional switch).

So 3-way is: 1on+1off+1on=3ways,,,,
.....4-way is: 1on+1off+1on+1on= 4ways.
and so on...

Something people can understand

I don't understand.

Originally Posted by H.G. Watson, Sr.

The traveler (in the switch loop) and the switch loop itself must make or break the HOT, not the common (neutral).

Thanks. HG. I got my terms crossed up last night. Easy to do.

We don't need to know how to wire the thing, just how to inspect it and then describe the problem. I'm just wanting to find a shortcut, my bad.

Originally Posted by Rick Cantrell

Is the "on position" up or down?
What about the "off"?

If they are 3-way and 4-way switches there is no "ON" position or "OFF" position as they change . That's why 3 way and 4 way switches do not have on and off stamped into them

The neutral is not needed at all areas as stated above even using the most recent NEC. It also does not apply retroactively either.

Originally Posted by Jim Port

The neutral is not needed at all areas as stated above even using the most recent NEC. It also does not apply retroactively either.

Since THAT was NOT "stated above", not sure what your point was or is.

The neutral is not needed at all areas as stated above even using the most recent NEC. It also does not apply retroactively either.

Originally Posted by H.G. Watson, Sr.

Since THAT was NOT "stated above", not sure what your point was or is.

Originally Posted by H.G. Watson, Sr.

The "common" or neutral should not be being switched the traveler should be the conductor being switched. Modern rules (here, at least) require supplying a common (or a neutral) to (and if necessary through) all switch locations (to provide for lighted switches, occupancy sensors, etc.) gone are the days of "re-identifying" a neutral (or common, or 'return) of 2-wire plus ground multi-conductor cable for use in 3-way plus (two locations or more) switch loops, there are a host of multi-conductor cables available on the market which accomodate legal (and no re-identifying) multi-location control switch loops.

HTH.

As I said it does not apply to ALL as was stated.

Bold by me.

Originally Posted by Garry Sorrells

John,
Try explaining 3 way switching as counting 1on + 1 off + 1 on (for each additional switch).

So 3-way is: 1on+1off+1on=3ways,,,,
.....4-way is: 1on+1off+1on+1on= 4ways.
and so on...

Something people can understand

John,
Will try to explain in a better way. Do not confuse with referencing pole switch terms.
Describing 2 way switch, three way switch, four way switch, etc.
The first switch has a function of both on and off, thus = 2 way (think of it being left in the off position).
Each subsequent switch will turn on the light, thus = 1
# way switch = 2 + (total number of switches - 1)
Light with two switches is a 3 way switch: 2 + 1 = 3
Light with three switches is a 4 way: 2 + 1 + 1 = 4
OR as another formula : (# of switches) + 1 = X way switch.

Originally Posted by Garry Sorrells

John,
Will try to explain in a better way. Do not confuse with referencing pole switch terms.
Describing 2 way switch, three way switch, four way switch, etc.
The first switch has a function of both on and off, thus = 2 way (think of it being left in the off position).
Each subsequent switch will turn on the light, thus = 1
# way switch = 2 + (total number of switches - 1)
Light with two switches is a 3 way switch: 2 + 1 = 3
Light with three switches is a 4 way: 2 + 1 + 1 = 4
OR as another formula : (# of switches) + 1 = X way switch.

OK, thanks, Garry. Can my clients call you for the explanation?

Kidding.
I don't want to say more than one sentence about the light switches, and I don't want to give them a math test. "There are 2 switches for the hall light".

BTW, in electronics, those are single throw switches, on/off is one throw. There are two ways to switch the light, over there and over here.

Single switch, it"s on or it"s off. 2-ways

Two switches, it"s on or its off or it's able to be changed by other switch. 3-ways.

Three or more, (middle sw's) it's on or off but able to be changed from both directions. 4-ways.

I personally prefer single pole, single pole-double through, and double pole-double through. I guess that was too much for electricians though.

Originally Posted by John Kogel

It just bugs me to have to explain the term, yes there are two switches, not three.

If I can tell it's one those clients I need to keep it real simple for, I tell them 3 way is a type of switch not the number of locations.

Originally Posted by John Kogel

BTW, in electronics, those are single throw switches,

In electronics, those are single pole, single throw, no center off, switches ... but I knew what you meant.

Haven't had to even think about this for a long time
Hope I get this right

SPST Ordinary light switch
SPDT 3 way light switch
DPDT 4 way light switch

Originally Posted by Rick Cantrell

Haven't had to even think about this for a long time
Hope I get this right

SPST Ordinary light switch
SPDT 3 way light switch
DPDT 4 way light switch

The DPDT does have some internal wiring not found in the standard DPDT switch used in electronic hardware to make it easy to install as a 4 way.

Why not just put down that a particular light has switching from multiple locations, and leave off the 3,4 way terminology? Just a thought, no more need for explaining.

Originally Posted by J. Renner

Why not just put down that a particular light has switching from multiple locations, and leave off the 3,4 way terminology? Just a thought, no more need for explaining.

Unfortunately too many home owner handymen think wiring lights is just that simple. That is why we find so many dimmer switches installed in a multi-switched light that don't work. Knowing there are 3 & 4 way switches lets the buyer know that there is a little more to it. (Might need an electrician?)

Originally Posted by Robert Meier

Or what Vern said.

It's not often I can out type someone

They are called "three way" because it takes three times as long to explain how they work.

Fun stuff. I will start with what Watson said and what Robert said. The "Three" reference is to the three terminals on the switch. Ditto "Four" way. Any time you switch the same lights from two or more places, two three way switches are necessary. After the two three way sws you can have as many four way switches as desired and they will all be the same and perform the same function. If 10 sws control the same lights, two will be three way and 8 will be 4 way. As Robert pointed out, a Double Pole switch is very different from a 4 way. The easiest way for a non-electrician to tell the difference is that 3 and 4 way switches have no on/off labeling. A DP switch would say on and off. A DPDT switch should have three positions with off usually the center position. BIG DPDT switches are sometimes used for manual control of panels with stand-by generators.

Originally Posted by Garry Blankenship

A DPDT switch should have three positions with off usually the center position.

Nope. DPDT switches are in abundance with no center off. The can be used for many things ... such as the example you gave for the standby generator.

The power to the building would be the center terminals, the utility power terminal are another set, typically at one end of the switch back, and the other set could be for the generator - flip the switch one way and the building is on utility power, flip the switch the other way and the building is on generator power ... no center off needed or present.

The worse case I had was when the seller was at the inspection and insisted that nothing was wrong because "one of the switches was just a master switch". I explained to them that no, it has a problem, either a switch is miswired, a switch is bad or a traveler wire is missing. They were used to the problem being there so they did not understand it. Then to make it worse their 'electrician" called me for help a few days later.