3-way Light Switch Confusion...

[Robert Coats]

so for years, this has been the way to wire a pair of 3-way wall switches, usually so you can use use either switch to flip on a light, then the other to flip it off. Usually one at the top and another at the bottom of a stairs, or hallway. Mostly, I understood regardless of either switches' toggle (up or down), if the light was OFF, either switch would turn it back ON (and likewise for turning it off, e.g., either switch will do it). The magic traveler wire makes it work...Am I right about this?



My Little Slice Of Lasagna and I have been living away from home for a while, and I've noticed in both a hotel and now apartment (both < 8 years old) that their 3-way switches (hallways, both) don't work as described above, but work like this:

condition a: Left Switch = UP, Right Switch = UP, Light = ON
condition b: Left Switch = UP, Right Switch = DOWN, Light = ON
condition c: Left Switch = DOWN, Right Switch = DOWN, Light = ON
condition d: Left Switch = DOWN, Right Switch = UP, Light = OFF

The only things that come to mind are:

1. Code changed, and all of 'em are wired this way? IF so, how is it different from the image above?

2. Is there some funky logic about if one switch is at the entrance to a hallway, and another is at the end / entrance to a bedroom? How the fark does that work?

3. I am no over 60 and just need to be retrained

--Confused in Cobb County....

[dad911]

Should work as in 1st paragraph. 3 (or more) way any switch should toggle the state.

[A930Rocket]

All I know is, they should work like you first described. If they don’t they are mis-wired.

[peppy]

Is there a 3rd switch? Is one of the switches mounted upside down?

[Robert Coats]

Originally Posted by peppy

Is there a 3rd switch? Is one of the switches mounted upside down?

No 3rd switch, just the two, and they control a single bulb light on the ceiling. I too, thought one might be upside down, but even if that were true, I would expect both to either turn the light ON or OFF, as have every other 3-way switches I've used in the past.

Pretty sure it was just not wired properly, but still managed to pass code inspection. I suspect the inspector might have just overlooked it.

Mostly wanted to confirm there was/was not some kind code change that required a different wiring configuration.

Thanks to all for the help!

[svandamme]

I would start by representing it logically

this is what it should do electrically

[cabmandone]

Originally Posted by A930Rocket

All I know is, they should work like you first described. If they don’t they are mis-wired.

Yep! I have wired a few 3 way switches wrong in my day..

[svandamme]

I would start by representing it logically

this is what it should do electrically






Each switch should have 3 contacts 1 in 2 out

The 2 outs are connected.. and you alternate between 1 of 2 wires.
Both switched to the same wire : light works

[svandamme]

a 3 switch setup is also possible, but then you need a cross switch in the middle
that one just flips the contact

[Jolly Amaranto]

One way that could happen is if one of the wires circled here was disconnected.


This is a simplified diagram showing how the wiring should be. The white wire diapered but should go to from the light to neutral.

[MBAtarga]

Regardless of UP/DOWN position for either switch, if the light is off, toggling either switch should turn the light on and vice versa. If it DID work at some point, one of the switches has failed - and/or wiring connections have been altered or have come loose.

[MBAtarga]

And wiring is not always done with the light in-between the switches as per your diagram. Sometimes wiring to the light is from only 1 of the switches.

https://www.electrical101.com/3way-switch-wiring-using-nm-cable.html

[Jolly Amaranto]

Originally Posted by Jolly Amaranto

One way that could happen is if one of the wires circled here was disconnected.

I got that wrong. That would make the light on in only one of the combinations instead of off. This is a puzzle.

[911 Rod]

I went through this last week. I wired the new one exactly like the old one and it was messed up.
Read the instruction with the new switch and viola!

[Jolly Amaranto]

Another possibility is that they did not use three way switches and wired it like this.

Basically two single pole switches wired in parallel driving the same light. Both have to be off to shut it off.

[svandamme]

Originally Posted by Jolly Amaranto

Another possibility is that they did not use three way switches and wired it like this.

Basically two single pole switches wired in parallel driving the same light. Both have to be off to shut it off.

seems like a really complicated wiring plan with zero advantage??

why would you want 2 switches to turn 1 light off?

vs
2 switches on 1 wire that both need to be on to turn it on?


I understand it's the opposite outcome but What is the use case???
All it does.. is force you to go to 2 places to turn off the light.
It's probably worse the the single wire where you can turn it off from either side.. and might have to walk to the 2nd spot to turn it on if somebody at the other end flipped the switch when it was already off

[Jolly Amaranto]

Originally Posted by svandamme

seems like a really complicated wiring plan with zero advantage??

Really quite simple circuit.
Advantage: You don't have to run the extra wire between the switches. Three conductor + ground is more expensive. And you use less expensive simple wall switches.

Disadvantage: While you can turn the light on from either switch, both have to be off to shut it off.

[svandamme]

sure but it's a pain in the hole to turn the light off isn't it.
in the long run; for the duration of the installtion at current energy costs.. the price of the wire is not going to add up


besides, you still need 2 wires, single wire and to ground is not going to be up to code
so you still need to run the wire back to the box else the amp leak loss will trip.
Cannot see it done with less wires unless you do things like they wired up houses in the victorian age; when they hadn't figured out overload fires yet.

if you wanna cut costs on wires , go wireless !
Hue LEDs for instance

All my lights are permanently on 220volt
they turn on and off via digital switches

[MBAtarga]

Robert - do the switch toggles have labels of ON/OFF?
If they are 3 way - they will NOT have any labels as the label would be irrelevent.

[Jolly Amaranto]

Originally Posted by svandamme

besides, you still need 2 wires, single wire and to ground is not going to be up to code
so you still need to run the wire back to the box else the amp leak loss will trip.
Cannot see it done with less wires unless you do things like they wired up houses in the victorian age; when they hadn't figured out overload fires yet.

That was over simplified circuit diagram just showing the current carrying wires. I did not show the ground. In actually wiring a house in North America, (well the US anyway), the standard wire these days is a plastic sheathed cable containing two current carrying conductor plus a ground wire so really three wires in all. You can buy it in bulk and get a better price on it. To run a proper 3-way circuit you need three conductor + ground or four wire cable which costs more and you only need it for that one circuit. Therefore if you are cheap and lazy, you just use what is on hand. And if you are a cheep guy you go for the standard light switches which are less expensive too. A simplified house wiring for a three way light circuit would need standard cable to the light box from the breaker or fuse box and extra conductor cable from the light box to each switch box. This illustration shows a cheap way of doing it. Or you could run it more like the original posters diagram and run the power to one of the switch boxes and still have the same outcome in the end.