 In this video we're going to learn how to determine how many wires are going to a certain amount of devices in a three-way lighting circuit. So let's take a look what I'm talking about here. Here's a situation where we have a three-way switch on one side of a room, a three-way switch on another side of the room, we have a receptacle which is going to provide our power for the lighting circuits and we have a light here and we have a light here. So we have two lights that are being controlled from two different locations with three-way switches. For whatever reason we now have pipe from switch A to light A, we have pipe from light one to light two, from light two to switch B, and we have pipe from home run up to light one. Yes, this isn't a common situation but this is just to show how important it is that we can number our schematic, this is getting to a point here. So yes, I know that if you use Lumex this would be a completely different situation. But the point I'm getting at here is how you can determine the amount of wire that goes into the pipe using what's called a numbering system. So let's take a look what I mean. So the drawing that we had previous, I've converted to a schematic. So I have my three-way switch here, I have my three-way switch here, I have my two lights, and I have my receptacle down here. I have a hot and a neutral coming in here. So this is our schematic which shows how a circuit works electrically. Power comes into our common, then it goes up through the switch to a traveler. We have two travelers at a three-way switch, then our wire goes over to the second three-way switch where, again, we have two travelers, we have a common, and that common goes to the lights. So our common either brings power to the three-way switch or brings power from the three-way switch to the lights. Then as always we have the lights connected to the neutral. Down here we have a hot going to our receptacle and from the other side of the receptacle going back to our neutral. So when we're dealing with this circuit and trying to determine how many wires go in the pipes from the previous drawing, which I'll get to in a second here, the first thing we're going to want to do is we're going to want to number up our wires here. So what I'm going to do is this. I'm going to call this one, wire one, this is wire one. Anything attached to that wire is going to carry the same number. So this will be one there, that will be one there. Then whenever we have a node, one of these little black spots or if there's a break in the line or a device in the way, we change the number. So we're going to do that right now. So we're going to go over onto this side and we're going to say, okay, this is two and that's two because they're attached. Over here is three. That is attached to this side, three and three. On this side we have four and four. This goes all the way up to here. There's four there. And then if we look down here to the receptacle, we've got this four goes all the way back to this receptacle. There's nothing breaking it in the line. There's no node or anything in the way there. So this two will be the number four. We have one thing left. We have up here, we have a five and a five. So just to walk through again, a one here goes to this node. That's a one. Goes to this side of the receptacle. That's a one. A two here, which goes straight across to here. That's two. There's a switch break. So then we go to three. Three is attached to this as well as to this. Then we have the lights in the way. Four, four, goes up here, four there, four to this side. And then we finish this up with five, five. It doesn't matter which way you number it. This could be like one, two. You could go all over as long as at the end of this you end up with five wires in total. What we're going to do now is we're going to take this whole drawing over and we're going to place it right by our actual drawing that we have of the conduit. Now here we've got our actual drawing. So we're trying to determine how many wires are going in each one of these pipes. And I've moved our schematic over so we got something to work with. Our next step in this is to take the numbers that we figured out off of our schematic and move them over to the actual devices. So if I look here, I've got three-way switch A. We could say that it's got numbers one to the common, two to a traveler, five to a traveler. So the numbers attached to A is going to be one, two, and five. So we're going to write that up over on the side here. I look at the lights. The lights here are three and four. They're both going to be three and four because they're in parallel. So I'm going to take that and I'm going to put that number up beside these lights. Then I get down to the home run. The home run or sorry, the receptacle is a one and a four. So I'm going to put that by the receptacle. Three-way switch number two or B, sorry, has got the numbers three to the common, two to a traveler, and five to a traveler. So I make sure that I put those down there, two, three, and five. And the last thing I have here is my home run, which is my hot right here and my neutral right here, which is one and four. And I write that in there. So now I've got everything numbered up. Another thing I do and I tell my students to do all the time is I know I've got five wires in total. So what I'm going to do is I'm going to write the numbers out just so I have like a checkbox or something to work from here. So I'm just going to go one, two, three, four, five because I have five wires in total. Now comes the fun part because what we'll be doing is basically playing connect the dots. So I'm going to start with one and see where I can attach one to everything. So here I've got a one and I've got a one. So basically it's done internal into there. But I need to also take a one over to here. I don't have a one here. I don't have a one here and I don't have a one here. So I'm going to take the wires through and what I like to do is put a little hash mark on the pipe. So I'm going to do that right now. So we're going to take one. So this becomes one and a one there. And then I put the number one beside it just so I remember that I did it. I check off the one there. That's why I have that thing numbered off to the side so I don't forget. Because when you start getting into bigger circuits to get a little more complicated, you could lose track of your numbering. Then I look for two. I've got a two. I don't have a two down here. I have a two at this three-way switch. I don't have a two in the lights but I do have a two down here. So I've got to take a two from the first A all the way to B. So let's take that into consideration. So there's two, two because I've got to go through there, two. So I'm just going to write two there, two there, two there. And I give it the old check mark there. So that's taken care of. Three. I have a three at this light. I have a three at this light and I have a three at this switch. So I'm taking the threes just from the switch to this light and to this light. So let's just draw that in there. So there's a three and a three. There's no three over on this side or down here. So I don't have to carry that through. Four. Oh, let's don't forget to give ourselves the old check mark there. Three is taken care of. Four. I do have a four down here. I do have a four at this light and at this light. I don't have a four there and I don't have a four there. So I'm going to take the four through from there to there and there to there. So I've got my four, which is my neutral, going all the way through. And I got that's a check mark there. Oops, let's just get our pen color working. And there's my four. Last number, five. So I take a look here and I see, OK, I've got a five at three-way switch one or A and I've got a five at three-way switch B. So no other fives. I don't have a five here or a five here or a five here. So what I'm going to do is take my five through from A all the way through down to B. So I do that five, five and five. And I give that the check mark. And there you have it. We have determined right now that this wire here or this pipe will carry three wires. This pipe will carry four wires. This pipe will carry three wires. And this pipe down here, we don't really count because it's the home run. It's just going to have a hot and a neutral in it. Now, again, this isn't a very practical circuit because if you ran Lumex in a house, you would generally be using a two wire or three wire. So this wouldn't work having this four wire here. So you'd find another way to get your circuits laid out. And there's other ways to do that. This is just to show how we can use our schematic to determine how many wires are going into something like a piece of pipe. Or you could use this to determine that the layout that you've got here won't work because you've got four wires between light one and light two and that there's going to be a better way to connect this circuit up. So there you have it. It's so important to understand how your schematics work, get those drawn up, get them numbered, take those numbers and transfer them to the reality and then start kind of making your little hash marks to determine how many wires are in each pipe.