Lighting question

[depcdivr]

This may be a simple question for many of you to answer but its got me stumped.

I have the following situation:
Hall light with three switches. The two end switches are 3-Way and the middle is a 4 Way. I am not sure how they are wired at the moment because It was existing in the house.

This is how it operates. If the lights are On then any of the three switches can turns the lights on/off. If you turn the light off by a 3 way switch then the center(4 way) switch will not turn the lights on again. Either of the 3-way switches will turn the lights on if actuated. Then when the lights are on the 4 way can turn the lights off and on again. Until it is turned off by a 3-way... and on and on it goes.

I understand how the wires are travellers are supposed to run and how it is supposed to operate but I can't wrap my head around how the circuit is actually connected to give the results above. Anybody have any thoughts on this schematic?

 

[synchro]

In order to provide more clarity on the switch behavior, I suggest the following be done:

Construct a "truth table" for all 8 possible positions of the three switches. For example, have all the Up and Down positions of the switches listed under three columns that are headed 4-way, 1st 3-way, and 2nd 3-way. And then have a fourth column giving the ON or OFF state of the light for each of the 8 sets of switch positions.

 

[Fred B]

One thing I've seen is related to the 4W switch is differences in configuration between MFGs. Not all do the cross over the same, simplest description is use of NM 3 wire example. Some mfg will cross over with both "reds" on top 2 terminals and both "blacks" on bottom 2 terminals, other mfg will have both "reds" on right side terminals and both "blacks" on left terminals.

This is the most common trouble call I get from a HO or handiman wiring up the switches. I'll even get "but I took a picture and wired it up like the old one". But they never bothered to look for the MFG instructions on the 4W switch.

Have also seen some one having put a DPST switch into the 4W switch box and returned to store or a mfg miss mark.
One way to test if mfg instructions missing is pull the switch and using continuity tester ring out the switch in various positions, you will get an X configuration in one position and a straight thru (either side to side or top to bottom) in the other position. Confirm travelers are in correct configuation.

Another thing I've seen is someone has put the common on the traveler terminals on the three way effectivily turing the one switch into a strictly on/off when the one switch is in a particular position.

 

[Seven-Delta-FortyOne]

Ugly’s has several diagrams drawn out, including with various locations for power input.

 

[ptonsparky]

Remove the 4 way, and make sure the 3 ways work, or open up everything and start over.
Yes, the 4 ways vary.

 

[Little Bill]

4-way could also be bad, I've replaced many, or bypassed them.

 

[LarryFine]

It's easy to confuse. You always go by the terminal colors, not by their position on the switch body.

On a 4-way, the two dark terminals go to one 3-way's travelers, and the two light terminals go to the other's.

 

[James L]

It's easy to confuse. You always go by the terminal colors, not by their position on the switch body.

On a 4-way, the two dark terminals go to one 3-way's travelers, and the two light terminals go to the other's.

I recently installed switches from legrand and the 4-ways had four brass screws and no indication of where to put each traveler pair.

 

[James L]

.....have a fourth column giving the ON or OFF state of the light for each of the 8 sets of switch positions.

There are actually 12 different combinations

 

[James L]

Really the best place to start might be with the year the house was built. I can't count the number of times I've had somebody call me on the phone to help troubleshoot a 3-way or 4-way system, only to find out it's knob and tube wiring. That process can be a little bit involved.

Otherwise, unscrew the switches from the wall and make a note of every wire that's connected to the switch, what color screw terminals they are on, and any wires that might be wiring noted in the back of the box. All three boxes

But honestly, my quick guess is that somebody changed one of the 3-way switches and got a traveler mixed up with a common

 

[hillbilly1]

One thing I've seen is related to the 4W switch is differences in configuration between MFGs. Not all do the cross over the same, simplest description is use of NM 3 wire example. Some mfg will cross over with both "reds" on top 2 terminals and both "blacks" on bottom 2 terminals, other mfg will have both "reds" on right side terminals and both "blacks" on left terminals.

This is the most common trouble call I get from a HO or handiman wiring up the switches. I'll even get "but I took a picture and wired it up like the old one". But they never bothered to look for the MFG instructions on the 4W switch.

Have also seen some one having put a DPST switch into the 4W switch box and returned to store or a mfg miss mark.
One way to test if mfg instructions missing is pull the switch and using continuity tester ring out the switch in various positions, you will get an X configuration in one position and a straight thru (either side to side or top to bottom) in the other position. Confirm travelers are in correct configuation.

Another thing I've seen is someone has put the common on the traveler terminals on the three way effectivily turing the one switch into a strictly on/off when the one switch is in a particular position.

The first four way I wired when I was a teenager, was exactly like that. I wired it like the box it came in said. Wouldn’t work. Took my ohmmeter and figured out how it worked. It was not like the box said! LOL!

 

[depcdivr]

One thing I've seen is related to the 4W switch is differences in configuration between MFGs. Not all do the cross over the same, simplest description is use of NM 3 wire example. Some mfg will cross over with both "reds" on top 2 terminals and both "blacks" on bottom 2 terminals, other mfg will have both "reds" on right side terminals and both "blacks" on left terminals.

This is the most common trouble call I get from a HO or handiman wiring up the switches. I'll even get "but I took a picture and wired it up like the old one". But they never bothered to look for the MFG instructions on the 4W switch.

Have also seen some one having put a DPST switch into the 4W switch box and returned to store or a mfg miss mark.
One way to test if mfg instructions missing is pull the switch and using continuity tester ring out the switch in various positions, you will get an X configuration in one position and a straight thru (either side to side or top to bottom) in the other position. Confirm travelers are in correct configuation.

Another thing I've seen is someone has put the common on the traveler terminals on the three way effectivily turing the one switch into a strictly on/off when the one switch is in a particular position.

Thank you this makes sense. I did the "took a picture" route but never occurred to me they could be different. Doh!

 

[depcdivr]

4-way could also be bad, I've replaced many, or bypassed them.

I replaced all three switches with new because old switches failed(would not turn lights off in any combination)

 

[wwhitney]

There are actually 12 different combinations

3 switches, each with two states, to 2*2*2 = 8 states for the switches.

Cheers, Wayne

 

[James L]

3 switches, each with two states, to 2*2*2 = 8 states for the switches.

Cheers, Wayne

You're right. I don't know what I was thinking of.
Go back to sleep now

 

[depcdivr]

You're right. I don't know what I was thinking of.
Go back to sleep now

Yes it would make sense that there are 8 BUT and this is the part that I don't understand based on the condition of the two 3 way switches the 4 way will either work or not work. This is not a simple as when switch one is up the 4 way works and when its down it doesn't. Because you can change the state each 3 way switch with the other 3 way switch. Therefore if I build the true table starting with switch one then I get two different states of the output based on the last switch to change state. Therefore there are more than 8 states because it has to do with not only the position but which switch is change state. I hope that I explained that properly.

 

[wwhitney]

Yes it would make sense that there are 8 BUT and this is the part that I don't understand based on the condition of the two 3 way switches the 4 way will either work or not work.

That is still true with just 8 states.

Because you can change the state each 3 way switch with the other 3 way switch.

You're conflating the light state (on or off) with the switches states.

Therefore if I build the true table starting with switch one then I get two different states of the output based on the last switch to change state.

That can not be true with regular 3-way and 4-way switches.

Cheers, Wayne