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sirsparksalot 05-29-2011 02:23 AM

learning purposes: 3-way switching
I don't remember where I found the image, but the first one shows routing of the wires without connections at the light. The second is my attempt to make those connections (in blue); is it correct? Visualizing 3-way switches is a thorn in my side.

frenchelectrican 05-29-2011 02:46 AM

Let me help vous on this one .,

If I did read this one correct that you have a dead end three way switch loop if so .,

The white conductors from the luminaire and from the first switch box will be wirenutted together on this part.

Now hook the black conductor from the luminaire junction box { power source only or unswitched power source } to the switch box.

Leave the red one alone for a moment you will see the result in a minuite.,

At the first switch box the three conductor from the luminaire location wirecap the white conductor that is a legit netural which you may have to use it { it will be required per 2011 NEC code anyway } but the white conductor from switch box to the other switch box it have to be REMARKED this is very important SVP., ( tape or marker any colour beside not white or grey or green they are off limit colour to remarked }

anyway take the black conductor from the luminaire conductor that will go on the " Common " or dark coloured screw while the red one from the luminaire cable to tie up to the other three way cable { switch to switch only } red cable as well wirenutted and set it back in the box.

Now take the remarked white and the black { from the switch to the switch } use them on light colour brass screws that is shuttle or traveller conductors { a tip twist them few turns so you know this is for three way traveller } then do the same thing with other three way switch the remarked white and black on the light brass coloured screw then finally take the red one to the " common " and ya are done with it.

Keep in your mind there will be no netural in second switch box at all with cable { if this in conduit or 4 conductor cable then it will be not a issue }

Hope that help ya.


Saturday Cowboy 05-29-2011 05:17 AM

joed 05-29-2011 09:52 AM

It is also important to note which wires are on the common terminals of the switches. In the first switch the black goes through with no connection and goes to common of #2. The remarked white goes to the common of #1.

sirsparksalot 05-30-2011 01:48 AM

So basically, in all of the different configurations of 3-ways, a 3-wire cable is needed only between the switches?

Saturday Cowboy 05-30-2011 02:14 AM


Originally Posted by sirsparksalot (Post 657507)
3-wire cable is needed only between the switches?

that is the first rule of three ways. there are some exceptions, but thats doing it the hard way.

sirsparksalot 05-30-2011 02:44 AM


Originally Posted by Saturday Cowboy (Post 657517)
that is the first rule of three ways. there are some exceptions, but thats doing it the hard way.

hang with me a min, I'm gonna rework this booger :eek:

sirsparksalot 05-30-2011 02:54 AM

1 Attachment(s)
Per Joed's comments (if I've gotten them right) this switch doesn't appear to work.

SD515 05-30-2011 08:11 AM

In this 2nd diagram, the lower switch has the 2 lower connections reversed. The wire to the load goes on the common terminal.

SD515 05-30-2011 08:15 AM

Some info for 3-way switching...

White from the source goes directly to the load.

Black from the source goes to the common terminal of one of the 3 way switches.

Black of the load goes to the common terminal of the other 3 way switch.

The travelers get hooked to the remaining terminals.

If you have to use a white as 'hot', it has to feed a switch and be re-identified at both ends. I usually use a black "Sharpie" marker.

Use 14 gauge wire on a 15 amp circuit, 12 ga on a 20 amp circuit.

I found that if you want the lights to be off when both switches are down (or both up), you reverse the travelers. I made my own rule of thumb, and call it "Red on Right". If I'm using cable and both 3-way switches are identical, I put the red traveler on the right side of the first 3-way switch, and then on the left of the second switch. Mount them both using the same orientation.

itin1200 05-30-2011 08:34 AM

I found the illustrations on this page very helpful with a lot of the 3-way circuits I wired last fall.

Good luck.


SD515 05-30-2011 08:37 AM


Originally Posted by sirsparksalot (Post 657507)
So basically, in all of the different configurations of 3-ways, a 3-wire cable is needed only between the switches?

Before the 2011 code, yes. Now that the neutral is needed at the switch boxes, things can get a little more complicated.

In essence, yes, 3 wires are needed to run to the 3-ways switches. Depending on the layout of switches versus where the load is and where the source is...sometimes 3 wire cable would run from a sw box to the load box then another 3 wire from load box to other sw box. In this example, there are 2 wires in between the switches (3 physically), and have a junction in between them (the load box). The 2 wires are going to pass through the load box (travellers)...switch to switch. The 3rd physical wire leaving each sw box is going to be a constant hot, switched hot, or a neutral.

drtbk4ever 05-30-2011 11:29 AM

All I can say is if I ever need to wire a 3 way switch, I'm calling one of you guys.

joed 05-30-2011 03:56 PM

With the requirement for neutral at switch boxes a 4 wire cable would be needed between the switches in the above diagrams.

The last diagram is wrong. the wrong wire is on the common of the bottom switch.

sirsparksalot 05-31-2011 01:24 AM

1 Attachment(s)
Thanks to everyone for their help; all of you contributed. I hope the following is correct (I seem to be able to trace the current flow), and hope you'll let me know if I missed something.

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