When it comes to residential wiring, NM-B wire—short for Non-Metallic Sheathed Cable, Type B—is one of the most common and trusted choices used by electricians and contractors across North America. But what exactly is NM-B wire, and why is it so widely used in homes and light commercial buildings?
In this article, we’ll break down everything you need to know what does nm b wire mean, including its structure, uses, benefits, and how it compares to other types of electrical wire.
NM-B Building Wire
🔍 What Is NM-B Wire?
NM-B wire is an electrical cable that contains multiple copper conductors (usually two or three) individually insulated with thermoplastic material and enclosed within a PVC jacket. It also includes a bare ground wire.
The “NM” stands for non-metallic, indicating that the outer jacket is made of a plastic material rather than a metal sheath. The “B” indicates that it is rated for 90°C (194°F) in dry locations.
Key characteristics:
Voltage Rating: 600 Volts
Temperature Rating: Up to 90°C in dry locations
Application: Indoor residential wiring
Conductors: Copper only (solid or stranded)
🏠 Where Is NM-B Wire Used?
NM-B wire is primarily used in residential and light commercial buildings for:
Lighting circuits
Electrical outlets
Switches
Appliances (e.g. dishwashers, garbage disposals)
Branch circuits running through wood framing inside walls, ceilings, and floors
It’s designed for indoor, dry locations and must not be used outdoors or in wet environments. For outdoor use or direct burial, UF-B (Underground Feeder) cable is the proper alternative.
🧰 NM-B Wire Construction
A typical NM-B cable consists of:
Copper conductors (usually 14 AWG to 6 AWG)
Individual thermoplastic insulation (often THHN)
Bare ground wire
PVC outer jacket (color-coded by gauge: white, yellow, orange, black)
Example:
A 12/2 NM-B cable includes two 12 AWG copper wires (hot and neutral), a bare ground wire, and a yellow PVC sheath.
✅ Benefits of Using NM-B Wire
Easy to install: Lightweight and flexible for fast wiring in wood-framed structures.
Cost-effective: Ideal for standard 120V and 240V branch circuits.
UL listed and NEC compliant: Meets safety standards for home wiring.
Color-coded jackets: Helps electricians quickly identify wire gauge.
🔄 Common NM-B Wire Types
| Cable Type | Wire Gauge | Applications |
|---|---|---|
| 14/2 NM-B | 14 AWG | Lights & low amp circuits |
| 12/2 NM-B | 12 AWG | Standard 20A receptacles |
| 10/3 NM-B | 10 AWG | Clothes dryers |
| 6/3 NM-B | 6 AWG | Electric ranges, large appliances |
⚠️ Important NM-B Wire Usage Guidelines
Dry indoor use only (walls, ceilings, floors)
Not allowed in wet or damp environments
Do not run NM-B in conduit outdoors
Follow NEC installation codes and local building regulations
🛒 Where to Buy NM-B Wire?
At TOT Wire & Cable, we supply a wide range of NM-B wire sizes, available in bulk reels or custom lengths. Whether you're a contractor working on a new residential build or a wholesaler looking for reliable inventory, we offer:
Competitive pricing
Fast delivery
Technical datasheets
OEM packaging options
📞 Contact us today for a custom quote on NM-B wire.
