Romex Cable, A Brief Explanation.


The conductors inside the romex 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 a 60 watt 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.

Romex Cable Wire Gauge Chart

Go to my "Wire Gauge Calculator"

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

Romex Wire Color Code

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. Sort of 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.

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