Three lights, two switches, one headache

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  #1  
Old 12-31-04, 10:08 AM
tngoodguy
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Three lights, two switches, one headache

In a hallway, I've installed 3 light fixtures, all switched from either end of the hall. The instructions I followed said to run 3-conductor cable from the first (powered) switch to the first light, then 4-conductor cable between the first, second and third lights, then 3-conductor cable from the third light to the second switch. All done and drywalled. Now I'm installing the fixtures and 3-way switches and am stuck, because I think the instructions are wrong. They say to pass the black and red wires of all cables through from the first to second switch without connecting to the fixtures, then connect the black and white fixture wires from each light to the white wire of the four-conductor cable. Nor do they say what to do with the 3-conductor cable at the first and third fixture. There is no mention of the forth (blue) conductor. This couldn't be right, as it would cause each fixture to be in a series with one another, the blue wire would be unused and I'm not sure what else. Maybe all these years of good Tennessee whiskey has caused an arc fault in my problem-solving neurons, but I can't figure it out. I've looked at many similar questions in this forum, but none fit this situation or are understandable, at least to me. How should these wires be connected, at the switches and each fixture?

THANKS!
 
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  #2  
Old 12-31-04, 11:02 AM
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The system that you describe can be made to work. Usually in these forums we tell people to shy away from it because 4 conductor wire is harder to get, and the wiring is a bit more complex.

Call the various boxes:
SW1 switch with power coming in
L1, L2, L3 lights
SW2 switch and end of line
for the wires I will use the following symbols:
- to mean 2 conductor (white/black)
= to mean 3 conductor (white/black/red)
# to mean 4 conductor (white/black/red/blue)

Your circuit is connected:

power - SW1 = L1 # L2 # L3 = SW2

Please confirm the above. If it is not correct, then stop now.

In SW1:
All whites get joined.
black from power connects to three way switch common.
black to L1 connects to first three way switch traveler
red to L1 connects to second three way switch traveler

In L1:
connect white from SW1 to white to L2 and white on the light fixture.
connect black from SW1 to black to L2
connect red from SW1 to red to L2
connect blue to L2 to black on the light fixture.

In L2:
all whites together
black from L1 to black to L3
red from L1 to red to L3
blue from L1 to blue to L3 to black on the light fixture

In L3:
white from L2 to white on light fixture.
Black from L2 to black to SW2
Red from L2 to Red to SW2
blue from L2 to black on light fixture to _white_ from SW2. Use a magic marker to _code_ this white wire with a black ring.

In SW2:
white from L3 to switch common. Use a magic marker to _code_ this white wire with a thick black ring.
Black from L3 to first three way switch traveler
Red from L3 to second three way switch traveler.

Please note that there is a _slight_ color coding violation in these instructions. This is done on purpose to make the color code consistent through the circuit.

-Jon
 
  #3  
Old 12-31-04, 11:59 AM
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First of all let me say that what you have done is not the proper cabling configuration, but you can make it work.
At the switch box with the power coming in connect the black wire from the two-conductor cable to the "common" on the switch. (The common will be a different color screw than the other two)
Connect the two white wires together.
The remaining black and red wires connect to the remaining two screws on the switch, (it doesn't matter which way).

At the first light (after the switch box we just wired) connect the red-to-red, black-to-black. White to white but also connect a "pigtail to the two whites so you can connect this to the light fixture later. The blue will connect to the light fixture.

At the second light (middle) connect the red-to-red, black-to-black. White to white but also connect a "pigtail to the two whites so you can connect this to the light fixture later.
Blue-to-Blue but also connect a "pigtail to the two blues so you can connect this to the light fixture later.

At the third light connect the red-to-red, black-to-black. The white wire from the four-conductor cable will connect to the light fixture.
The white wire from the three conductor cable (coming from the switch box) will connect with the blue wire also connect a "pigtail" to the white and blue wires so you can connect this to the light fixture later.

At the last switch connect the white wire to the "common" of the switch then connect
the remaining black and red wires to the remaining two screws on the switch, (it doesn't matter which way).The white wire should be colored black at both ends (switch box and light fixture) to denote it as a hot wire and not a neutral wire.

Please make sure you have your work inspected by the proper authorities in your area.
Good luck.
 
  #4  
Old 12-31-04, 12:34 PM
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The post by WINNIE is correct except that you must revesrse the use of the black ond white wires between L3 and SW2. The light switched power must not be on the white wire.

Connect the black from L2 to the white to the SW2.
Connect the White atSW2 to the traveller screw.
Black goes to the common screw at SW2.
 
  #5  
Old 12-31-04, 01:26 PM
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joed:
If you read my post you will notice it is exactly the same as Winnies, it was just worded differently to give another perspective to tngoodguy.

Also to make it easier for tngoodguy you will notice that winne posted:
QUOTE: Please note that there is a _slight_ color-coding violation in these instructions. This is done on purpose to make the color code consistent through the circuit. End Quote.
I followed winnie's lead on this so as not to confuse tngoodguy.
 
  #6  
Old 12-31-04, 01:34 PM
tngoodguy
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Winnie, Buzz and Joed -- Thank you so much for your advice. It all makes sense, really. I will study on this and then try it out. And, what a popular and useful site this is -- thanks again for your help, and I hope you have a happy and safe New Year.

P.S. to Winnie, we hope to get final electrical inspection scheduled for next week -- that is when we'll see how this all went.
 
  #7  
Old 12-31-04, 05:26 PM
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Please do not recommend code violations, slight or not, in this forum. Jon's and Buzz's instructions are wrong (and they said so). So please do not do it this way. Please accept the modification mentioned by joed. There is no excuse for creating a code violation on purpose, especially when doing it in the code-compliant way is just as easy.
 
  #8  
Old 01-01-05, 07:17 AM
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Sorry,

I need to step back and explain myself a bit better. First to be clear, we all agree on the actual circuit layout. The only point of discussion here is the _color code_ for that layout, specifically the use of a 'reidentified' white conductor. I had to go back and re-read the code, and on re-reading I've decided that the instructions that I gave are totally code compliant.

The bit of code of interest is 200.7(C) of the 2002 NEC, which says that the white conductor may only be used as the _grounded_ conductor (the 'neutral') with the several exceptions.

200.7(C)(2) is one of these exceptions, which explicitly says that a white conductor in a cable assembly _may_ be used as the supply to the switch but _not_ as a return conductor from the switch to the 'outlet' (light fixture), with the additional requirement that you permanently re-identify the white conductor everywhere it is accessible with a different color. This bit of code is written as a permission. You are not _required_ to use a white conductor in a switch loop at all. If you wish, you can go out and get special custom NM cable made up that doesn't have a white conductor, or you can use NM cable with an extra conductor and simply not use the white conductor in your switch loops. But if you wish to use the white conductor in a cable as part of the switch loop using exception 200.7(C)(2), you have to follow the rules of the exception.

Look at 200.7(C)(1). This is a _different_ exception. It simply says that a white conductor in a cable assembly _may_ be used as an ungrounded conductor if permanently re-identified (marked) at each accessible point. It doesn't say anything about switch loops at all. It doesn't say 'except for switch loops'. It simply says if you want to use it, you gotta mark it.

In this application, I believe that it is a better design to use the re-identified white conductor as the return to the light fixture. Remember that the traveller conductors are themselves switched conductors, and somewhere in this particular set-up there will have to be a re-identified white conductor connecting to a conductor of another color.

I thus stick by my original advice, claim that it is not a code violation because of 200.7(C)(1), and promise to never advocate something that I believe to be a code violation...and to re-read the code if I feel that the best installation would be a code violation, so that I can reconcile the two.

-Jon
 
  #9  
Old 01-01-05, 09:36 AM
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Wow, that's an interesting interpretation. 200.7(C)(1) predated the 2002 NEC, but 200.7(C)(2) was added in 2002. Using your interpretation, there would be no reason to add 200.7(C)(2), since 200.7(C)(1) is more generous. Although I think a lawyer might agree with your interpretation, the intent of the code is clear and I don't believe that any electrical inspector in the U.S. would accept your interpretation.

Actually, I think the 2002 code writers goofed up by not editing 200.7(C)(1) when they added 200.7(C)(2).
 
  #10  
Old 01-03-05, 08:55 AM
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This was an interesting thread...I didn't even know 12-4 existed!

Just a question for my learning:

Would code allow the running of two 12-2 cables instead of the 12-4?

The circuit would be like this:

power - SW1 = L1 - - L2 - - L3 = SW2

Where "-" is 12-2, "=" is 12-3, and "- -" is two 12-2's

Actually, the 12-2 with the two travelers could completly bypass L2.
 
  #11  
Old 01-03-05, 09:58 AM
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This exact point has been debated. If you were to run two 12/2 NM cables side by side, I believe that it would be permitted. However it would not be permitted for any sort of metal armored cable, and you would need to use cable clamps rated for _two_ cables, or you would need to use non-metallic boxes. There are enough things that could go wrong that even though it is arguably 'to code', I would strongly recommend against this approach. Furthermore it is sketchy enough that an inspector might balk, and even if it meets the letter of the code, it is simply not worth the head-ache.

If you want to do this install using 'normal' materials, then the way to do it is to run 12/3 between the switches, just like a normal 3-way circuit, and then run 12/2 to the lights, and not try to share the switch legs with the cables powering the lights. The technique used above with the 12/4 cable is more complex, but does actually use less copper and is thus (slightly) more efficient. It has the additional benefit that if you use 12/4 all the way (between the switches and the lights, not just between the lights), then you can have unswitched power for the entire length. It is the way that I would do this installation if there were no difficulties getting materials. It might end up being more expensive, however, since 12/4 is hard to get.

-Jon
 
  #12  
Old 01-03-05, 10:02 AM
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If no part of the system is metal (boxes, clamps, etc), then you could indeed use two 12/2 instead of the 12/4. I still consider this a very poor solution since it makes the boxes overcrowded by including a lot of wires you don't need in the boxes. And it's downright confusing. If you do use two 12/2, don't even bother running one of them through the first two light fixture boxes.

Several other cable routings are better in many respects. Power - switch = switch - light - light - light is best by far. But a number of other options are also better than what you propose.
 
  #13  
Old 01-03-05, 10:04 AM
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Thumbs up

This explanation is predicated on this arrangement--------

2-wire B/W "Feed" cable into 3WS#1---- 3-wire B/W/R cable, 3WS#1 to LF#1----4-wire cable, B/W/R/Bl LF#1 to LF#2---- 4-wire cable, B/W/R/Bl cable LF#2 to LF#3--- 3-wire B/W/R cable LF#3 to 3WS#2.

"Neutral' connections---- White-to White @ 3WS#1-- White-to-White-to White fixture-lead @ LF1---- White-to-White-to White fixture-lead @ LF#2---White of 4-wire B/R/W/Bl cable to White fixture-lead of LF#3.

Black-wire fixture lead(FL) connections--- Black wire FL to Blue wire @ LF#1--- Black wire FL to two Blue wires of 4-wire cables @ LF#2---- Black wire FL to Blue wire of 4-wire cable and Black wire of 3-wire cable @ LF#3.

Two "Selected" wires in a "pair" arrangement-- each 3WS will "select" one of these two wires for "On/Off" operation---- Black & Red wires of 3-wire B/R/W cable to the 2 "S" teminals of 3WS#1---- Black-to-Black, Red-to-Red @ LF#1--- Black-to Black, Red-to-Red, LF#2------ Black of B/W//Bl 4-wire cable to White-wire of B/W/R 3-wire cable, Red-to-Red @ LF#3---- Red & White wires to the 2 "S" terminals of 3WS#2

3WS "Common" terminal connections--- Black wire of 2-wire B/W "Feed" cable to "C" teminal of 3WS#1------- Black wire of B/W/R 3-wire cable to "C" terminal of 3WS#2

Good Luck & Enjoy the Experience!!!!!
 
  #14  
Old 01-03-05, 11:24 AM
tngoodguy
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OK folks, I gotta say this makes me dizzy. I wish I had asked BEFORE drywalling. Anyway, please let me confirm with you what I understand to be the least controversial solution. I was able to draw out a diagram based on Winnie's solution. Couldn't figure out how to apply Joed's modifications though, because it seemed like something was missing, but probably just my mis-read. But now after changing my diagram based on PATTBAA's description, I think I've got it, and it also looks like what Joed is saying. I would include it here, but it will not copy and paste. All of you commenting on the 4-conductor cable solution seem to be saying the same thing until we get between L3 and SW2.

Here we go. At L3:

Connect the white wire of the 4-wire from L2 to the white wire on the fixture. The white wire from power source, SW1, L1 and L2 ends here.

Connect the black wire of the 4-wire to the white wire of the 3-wire leading to SW2.

Connect the blue wire of the 4-wire, the black wire of the fixture and the black wire of the 3-wire together.

Connect the red of the 4-wire to the red of the 3-wire.

At SW2, the black of the 3-wire connects to the common terminal, the red and white of the 3-wire connect to the travelers.

Whew.

Thanks so much for your help on this. I'll wait for your response, and if I'm correct, finish the job. Then, after all this, I probably will need a bit more of that Tennessee whisky I mentioned earlier. If you are ever in the Chattanooga part of the country, stop by and we'll have one together.

Thanks again.
 
  #15  
Old 01-03-05, 12:38 PM
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By jove, I think you've got it!
 
  #16  
Old 01-12-05, 08:39 AM
tngoodguy
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I took all of the above and drew a wiring diagram so I could better understand visually. I have checked my diagram against the descriptions several times, so I'm sure I have it right. Now, understanding I am usually stumped by 3-way issues such as this, something doesn't seem right.

If I follow the description, I have black from the power source connected to the common terminal on SW1, and the white connected to the white of the 3-wire. I have the the red passing by all light fixtures from a traveler on SW1 to a traveler on SW2. I have the black from the other traveler on SW1 passing by all fixtures, connecting to the white of the 3-wire going to a traveler on SW2. I have the white of each fixture connected to the white of the 3-wire and 4-wire, ending at L3. I have the black from L1 connected to the blue of the 4-wire (which starts at L1), and the black from L2 connected to the blue of the 4-wire. At L3, I have connected together the black from the fixture, the blue from the 4-wire and the black from the 2-wire going to the common terminal on SW2.

So from this, it appears to me that power will go from one or the other traveler (black or red) from SW1 to one or the other traveler on SW2. But, the power ultimately coming out of the common terminal at SW2 (black) will go to the black at L3 AND the blue connected at L3, thus energizing BOTH the black and white wire at each fixture. I don't see how this could work.

Is there a way I can post my diagram (an MSWord document) for your review? Or, is my description clear enough to see if this is right or wrong?
 
  #17  
Old 01-12-05, 09:45 AM
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Take a look at this diagram I just created using your description of your diagram:

http://lccofc.com/picstemp/3l2s1h.pdf


I see absolutely no problems with wiring this circuit as per this diagram.
 

Last edited by chirkware; 01-12-05 at 10:09 AM.
  #18  
Old 01-12-05, 03:31 PM
tngoodguy
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Thank you for the confirmation. Our diagrams are identical with respect to the way this should be wired (except yours is a lot prettier), so I think I have done it properly. This is what all respondents have been saying, as well. I mentioned earlier that three-way arrangements and I don't get along well, which led to my uneasiness. Thanks again.
 
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