NM-B (Non-Metallic Sheathed Cable)
2. The Bread and Butter of Home Electrics
Ah, NM-B. This is the stuff you’ll probably see the most of in your home. It’s like the Toyota Camry of electrical wiring: reliable, widely used, and gets the job done. NM-B stands for Non-Metallic Sheathed Cable, and it essentially consists of two or more insulated wires wrapped in a plastic sheathing. Think of it as a wire burrito, keeping everything snug and protected.
The “B” in NM-B indicates its heat resistance rating, which is crucial. It’s typically rated for 90 degrees Celsius (194 degrees Fahrenheit), but the ampacity (current-carrying capacity) is usually calculated based on 60 degrees Celsius (140 degrees Fahrenheit) for safety reasons. In layman’s terms, this means it can handle a fair amount of heat, but you still want to be cautious. It’s used for most interior wiring, including outlets, lights, and switches. However, it’s strictly for dry locations. Don’t even think about using it in a damp basement or outdoors. That’s a recipe for disaster, and potentially a very shocking experience.
NM-B comes in various gauges (thicknesses), each suited for different amperage requirements. 14-gauge wire is typically used for 15-amp circuits (like lighting), while 12-gauge is used for 20-amp circuits (like outlets in your kitchen). Heavier appliances like refrigerators and washing machines often require even thicker wiring, such as 10-gauge or even 8-gauge. Using the wrong gauge is like trying to drink a milkshake through a coffee stirrer — it’s not going to work very well, and you might end up with a mess.
The ease of installation and relatively low cost of NM-B make it a popular choice for residential electrical projects. However, always remember to turn off the power at the breaker before working with any electrical wiring, and if you’re not comfortable with electrical work, please, please, please call a qualified electrician. Your safety (and your house) is worth it!