NMC cable (also written as NM-C cable or Type NMC cable) is a special type of nonmetallic-sheathed electrical cable designed for moisture-prone, corrosive, and damp environments—places where standard NM-B cable cannot be used.
nmc wire
If you search for “nmc wire,” “type nmc,” or “what is nmc cable,” this guide gives you a full explanation, plus a comparison of NM vs NMC cable to help you choose the right type.
⭐ What Is NMC Cable?
NMC wire, or nonmetallic sheathed cable, type NMC, is a type of electrical cable with a corrosion-resistant, moisture-resistant, flame-retardant, and fungus-resistant jacket that is suitable for use in both dry, damp, and wet locations. It is an upgrade from standard NM cable, which is restricted to dry locations. NMC is used for both exposed and concealed applications, but its specific usage in certain environments may have restrictions depending on local codes.
NMC cable (Type NMC) is a moisture-resistant nonmetallic-sheathed cable that includes:
Thermoplastic insulation
Moisture-resistant, corrosion-resistant outer jacket
Two or more insulated conductors
One bare or insulated grounding conductor
NMC is basically an upgraded version of NM-B, engineered for areas exposed to moisture, condensation, or potential corrosion.
✔ Rated for 600V electrical systems
✔ Approved for damp or corrosive environments
✔ Permitted in agricultural buildings, barns, and exterior walls
⭐ Where Is NMC Cable Used?
Type NMC cable is designed for locations where NM-B cable is not allowed.
Common NMC cable applications include:
Agricultural buildings (barns, stables, poultry houses)
Utility buildings
Damp basements
Exterior walls and cavities
Carports and garages
Greenhouses
Food-processing areas
Light commercial buildings
Coastal or corrosive environments
If the installation may face moisture, chemicals, or corrosion, NMC is often the correct choice.
⭐ Construction of Type NMC Cable
NMC cable has three protective layers:
1. Moisture-resistant insulation
Each conductor has insulation formulated to prevent absorption of water.
2. Additional polymer jacket around conductors
Adds corrosion protection and strengthens the cable.
3. Waterproof, corrosion-resistant outer jacket
The main difference between NM-B and NM-C is the outer jacket, which is thicker, denser, and moisture-blocking.
⭐ NMC vs NM Cable (NM vs NM-C Cable)
Keywords: nm vs nmc cable
Here is the simplest comparison:
| Feature | NM-B Cable | NMC Cable (NM-C) |
|---|---|---|
| Moisture resistance | ❌ Not moisture-resistant | ✅ Moisture-resistant |
| Corrosion resistance | ❌ Limited | ✅ Excellent |
| Allowed in damp locations | ❌ No | ✅ Yes |
| Allowed in barns, agricultural buildings | ❌ No | ✅ Yes |
| Outer jacket | Standard PVC | Thick, moisture-blocking PVC |
| Common use | Dry indoor walls only | Damp, wet, corrosive locations |
| Cost | Lower | Slightly higher |
✔ If the space is dry → NM-B
✔ If there’s moisture risk → NMC
⭐ Is NMC Cable Indoor or Outdoor?
NMC cable is approved for damp or corrosive indoor areas, but not typically used as direct-burial outdoor cable.
For outdoor trenches, UF-B or direct-burial-rated cable should be used.
⭐ Code Requirements (NEC)
The National Electrical Code (NEC) allows Type NMC in:
Damp locations (NEC 334.10(B)(4))
Agricultural buildings (NEC 547)
Corrosive environments where NM is not permitted
The cable must be:
Protected from physical damage
Secured with staples or clamps
Installed per the manufacturer’s guidelines
⭐ Available Sizes of NMC Cable
NMC cable is manufactured in typical residential sizes:
14/2 NMC
14/3 NMC
12/2 NMC
12/3 NMC
10/2 NMC
10/3 NMC
Large conductor versions for agricultural/industrial use also exist.
⭐ When Should You Use NM-C Cable Instead of NM-B?
Use NMC when:
The wall cavity may get damp
The building has high humidity
The environment has ammonia or corrosive chemicals (barns, stables)
Code requires moisture-resistant cable
You need extra protection from corrosion
Use NM-B when:
The space is completely dry
You’re wiring interior walls, living rooms, or bedrooms
You want the most economical option
⭐ Summary: What Is NMC Cable?
NMC cable is a nonmetallic, corrosion-resistant electrical cable rated for damp or chemically active environments. Compared to standard NM-B, it offers better moisture protection, stronger jacketing, and expanded installation locations.
Use NM-C when:
Moisture is present
Corrosive chemicals exist
Installing in agricultural or utility buildings
Use NM-B when:
All installation areas are dry and non-corrosive
