House Wiring Cable


Conductors

Conductor is the term used for wires that are in a cable. For example a 3 conductor cable has 3 separate wires inside the cable. The wires insulation are typically color coded for the sole purpose of identifying one wire from another. Now in residential wiring, it’s very common that one of those wires is just a bare copper wire with paper sheathing around it for protection as well as isolation from the other wires. This wire is used as a ground wire and is typically not counted as a conductor since most residential wiring calls for a ground wire at all times.


Sizing

The conductors inside the cable come in a variety of sizes. The purpose of this is due to the amount of current which has to travel through the conductor in order to operate the load. For example, a circuit operating a single light bulb will only carry a small amount of current because the light bulb only draws 1/2 an amp. But if that same circuit were to operate 100 light bulbs, now that circuit needs to carry 50 amps current. This would require a larger conductor size to handle the heat that is created. Therefore proper wire sizing is critical.




Most 120Vac household circuits are fine using a 12 or 14 gauge wire. The smaller the gauge Number the larger the conductor size.

So when your needing a three conductor cable to wire up a basic 2-way switch, you will need a 14/2 w/ground cable. What that number means is 14 gauge (wire size), 2 conductor which also includes a bare ground wire. The 2 conductor only refers to the insulated wires and not the ground.

So 14/3 w/ground represents 14 gauge wire, 3 insulated conductors and 1 bare copper ground wire.

Now some wire manufacturer’s will put a green insulation on their ground wires but then it will typically count as a conductor. Kinda confusing isn’t it. But try not to put too much thought into it. Most common house circuits are very basic and thats all we really care about for now.

Wiring a 2-Way Switch

When wiring a 2-way switch circuit, all you’re really doing is controlling the power flow (Switching off/on) to the load (a light, lamp, outlet, ceiling fan etc..).

The cable consist of a black wire, a white wire and a bare copper wire.

Black wire = Power or Hot wire
White wire = Neutral
Bare copper = Ground

When wiring a 2-way switch circuit, all we want to do is to control the black wire (hot wire) to turn on and off the load. This simple diagram below will give you a better understanding of what this circuit is accomplishing.

Now as for the ground wire. It is very important to connect the ground wire to the switch as well. The Green screw on the 2-way switch is for the ground so all ground wires should be connected as seen below.

All ground wires (bare copper) are all now connected (incoming ground, load ground and switch ground). This makes for a safe protected circuit by having all grounds intact.

So what have we accomplished. By wiring a 2-way switch, The circuit below shows the basic concept of electricity flow to the load. Let’s assume the load you are controlling is a light. The electricity flows from the hot wire (black) through the 2-way switch (shown in off position) and then to the light and returns through the neutral wire (white). This is a completed circuit.

Wiring a 3-Way Switch

How to wire a 3-Way switch. Wiring a 3-way switch is a little more tricky than wiring a 2-way switch.

When wiring a 3-way switch circuit, What were doing is simply controlling the power flow (Switching off/on) to the load (a light, lamp, outlet, ceiling fan etc..) from 2 different locations. a couple examples would be:


At each end of a hallway.
At the top & bottom of a stairway.


Each 3-way switch in these examples are controlling the power source to the same load.

The 3-wire cable consist of a black wire, a white wire and a bare copper wire, while the 4-wire cable has an added red wire which is hot as well.

3-Wire Cable
Black wire = Power or Hot wire
White wire = Neutral
Bare copper = Ground

4-Wire Cable
Red wire = Power or Hot wire
Black wire = Power or Hot wire
White wire = Neutral
Bare copper = Ground

When wiring a 3-way switch circuit, all we wantto do is to control the black wire (hot wire) to turn on and off the load from2 different locations. The diagram below will give you a better understandinghow this circuit is wired.


Notice that there is a 3-conductor cable coming into the first box, then a 4-conductor cable going from left box to right box, then a 3-conductor cable going from the right box to the load.

The diagram below will give you a good understanding of what this circuit is accomplishing.


Follow along with the mouse pointer as we go through this. The source power (black wire) is coming in from the left. It ties into the common on the left switch. When the left switch is toggled, it connects to the upper circuit and now the circuit is open at the right switch which turns off the light. Toggle the right switch and it connects to the upper circuit and now closes the path and turns the light back on and so on. Congratulations! on wiring a 3-way circuit.

If you’re simply replacing a 3-way switch, the diagrams below will show the different scenarios on how your circuit could possibly be wired.

Like the diagram above. Power-Switch-Switch-Light




Power-Light-Switch-Switch




Switch-Light/Power-Switch

What is common in the diagrams above and with any 3-way switch circuit is that the power hot wire coming into the circuit will always go to the common terminal of the first switch. The hot wire from light always goes to the common terminal of the second switch. The traveler wires go from switch to switch connected to the traveler terminals, it doesn’t matter which. As long as you keep this in mind, a 3-way circuit becomes really simplified. And of course the neutral will always go directly to the load. 

Allow Tim Carter from AskTheBuilder.com to show you some great tips for installing and wiring a 3-way switch.

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