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#182474 - 11/28/08 03:55 AM Three way switches  
pdh  Offline
Joined: Jan 2005
Posts: 354
I generally dislike three way switches. The reason I have frequently stated in the past is the accidents that can occur while trying to flip a switch while carrying things in both hands. Last week the power went out (strange story) and it reminded me of another reason I dislike three way switches. Due to the power situation, I was going around the house unplugging critical things (computer first, happily running on UPS, so it was the UPS that got unplugged), and switching off lights.

The problem with three way switches is that I cannot tell from the switch whether the lights are actually on or off. The switches were not wired consistently.

It would be helpful if the switches were wired so that when all switches are in the down positions, the controlled circuit is down. My house (my mother had built) was definitely not wired very well (had it been properly inspected, there should have been a dozen or more red tags). So I have a project to rewire these three ways so there is at least a way to make sure the lights are off when there is no power.

I still don't like three way switches because I don't like any instance of a switch being reversed from up-is-on and down-is-off. I'd rather use those switches that make momentary contact in the up and down positions and then have a spring pressure return to the middle, controlling a contactor that controls the light circuits (most would be magnetically held on, but the few lights I want to normally stay on would be the latching type).

Our street was having the MV feeder rewired for some reason (the crews doing the work don't know why, as the new cable is the same capacity as the old). It's all underground. Apparently they switched one of the pad transformers down the street to the new cable. But there was a problem with the new connection and it was arcing. They didn't discover it until after the crew that connected the new cable hot had left for the day. So the crew that was still on site (not authorized or trained or geared up to work MV hot, I guess) had to pull the fuse on the whole street to remake the end of the cable going into the transformer, since it was now damaged by the arcing. Once I heard part of this story while the power was still out, I decided to play it safe and unplug stuff at home, even though this work was not on the transformer feeding me (that connection may come in the next week or two). Given mistakes this crew has made already on this project (slicing through a water main and damaging a gas line), I decided that disconnecting would be better, in case they managed to cause an underground equivalent of the Harford Event (video 1 - video 2).

Work Gear for Electricians and the Trades

#182475 - 11/28/08 04:27 AM Re: Three way switches [Re: pdh]  
gfretwell  Offline

Joined: Jul 2004
Posts: 9,069
You have put your thumb on the issue. When 3 ways are wired it is a good idea to verify that off is all down. All you have to do is flip one of them to make this true if it isn't. The "flip" side of that is they will also be off with both switches up.
These represent a logical "exclusive or".

This gets a little more complicated when you put 4 way(s) in the middle but you can still set them up so all down is off. Dr Boole says an even combination of "up" switches is off and an odd combination is on.

It always amazes me that an electrician will make sure all the cover screws are aligned in the same direction but they don't bother to coordinate how the 3 ways are set up. A lot of them just seem happy that they work right in all 4 states.
There is no code issue here.

Greg Fretwell

#182478 - 11/28/08 02:28 PM Re: Three way switches [Re: gfretwell]  
renosteinke  Offline
Cat Servant
Joined: Jan 2005
Posts: 5,316
Blue Collar Country
I'd say you have problems other than switch issues.

Sure, you can instal the switches so that 'down is off.' That will last right up to the first use. Do things 'out of sequence' just once, and all bets are off.

For example ... you enter the hallway, the lights are off, and all switches are down. You flip a switch up, and you have lights.
Now you walk the length of the hall, reach the other end ... and you flip that switch 'up' to turn the lights off.

They DO make illuminated 3-way switches, where the toggle is lit when the lights are off. They probably also make 'pilot' versions, which are lit when the lights are on.

Otherwise, there is a role for timers, motion sensors, and contactors. For example, overseas it is common for stairwell lights to operate for a timed interval from a push button at each level.

#182480 - 11/28/08 03:07 PM Re: Three way switches [Re: renosteinke]  
gfretwell  Offline

Joined: Jul 2004
Posts: 9,069
You can (should?) still have them oriented so with all switches down the light is off.

Greg Fretwell

#182482 - 11/28/08 04:19 PM Re: Three way switches [Re: gfretwell]  
renosteinke  Offline
Cat Servant
Joined: Jan 2005
Posts: 5,316
Blue Collar Country
Greg ... in the example I just gave ... you can see that it's just not possible to do that!

Let's look at it once again:
You enter a dark stairwell, lights are off, all switch handles are 'down.' So far, so good.
You flip one switch up, and you have light. You proceed down the stairs.
As you exit the stairwell, you want to turn the lights off. This switch has remained 'down' from the start. To turn off the lights, you have to flip the switch 'up.'

On your return trip, you would eventually return things to a 'down is off' state. If you exited the area by another route, however, it's anyone's guess what position the switch will be in.
For example, the next person to repeat your exact trip would turn the lights on by flipping the first switch 'down,' then turn off the lights by flipping the second switch 'down.'

In short, the orientation of the switch has absolutely no connection to the way it was installed.

#182484 - 11/28/08 04:57 PM Re: Three way switches [Re: renosteinke]  
Active 1  Offline
Joined: Feb 2003
Posts: 687
Grayslake IL, USA
They do make 3 ways with indicator lights in togal and decora. Needs a load to work.

Myself I would try to put most switches in so off is all one way. On resi jobs I might even make sure the switches are left in a uniform position when the job is done. Otherwise some people think you put the switch in upside down. Proving the customer wrong is not always the best idea.

#182490 - 11/28/08 09:20 PM Re: Three way switches [Re: Active 1]  
Texas_Ranger  Offline
Joined: Dec 2001
Posts: 2,393
Vienna, Austria
I think Greg is just talking about having them all the same orientation (i.e. both down = off, both up = off).

Anyway, what do three way switches have to do with having both hands full? What's the difference between a three way and a single pole switch under these circumstances? Yeah, you might have to try switching twice (if you expect it being down while it is actually up or vice versa), but I think that's acceptable. Spring operated switches or push buttons operating contactors just make the whole thing unnecessarily complex, adding potential error sources.
The whole stairway contactor thing only exists for power saving reasons - landlords don't trust their tenants to switch off the light after walking up or down the stairs.

#182493 - 11/28/08 09:31 PM Re: Three way switches [Re: Texas_Ranger]  
luckyshadow  Offline
Joined: Jan 2005
Posts: 305
Maryland USA
I wish all I had to worry about was the orientation of the 3 ways in my house.
Install motion detectors

Last edited by luckyshadow; 11/28/08 09:33 PM.

#182497 - 11/28/08 11:31 PM Re: Three way switches [Re: luckyshadow]  
twh  Offline
Joined: Mar 2004
Posts: 905
Regina, Sask.
I like a 3 way switch that controls a light that isn't visible from the switch. You just can't tell without going for a walk.

#182498 - 11/29/08 01:01 AM Re: Three way switches [Re: twh]  
gfretwell  Offline

Joined: Jul 2004
Posts: 9,069
I have eliminated a lot of this "3 way" confusion in my house with motion/occupancy detectors. You seldom turn on a light switch unless you want task lighting. The motion system makes sure you always have "walking around" light everywhere, inside and out. It is all fairly soft light. This started years ago when I figured out the girls were using the fridge for a night light. My first motion light was in the kitchen/dining area that also gets you from the front and back door. It went on from there. Now the light just follows you around the house.

Greg Fretwell

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