Cable Construction
Building Wires (THHN/THWN)
Single Conductors
Individual insulated conductors for conduit and raceway installations. Most common in commercial and industrial wiring. Color-coded for phase identification. NEC Article 310.
Insulation
PVC/Nylon
Cable Types
6 types
Cable Type Specifications
NEC Article 310| Code | Full Name | Temp Rating | Location | Voltage | Notes |
|---|---|---|---|---|---|
| THHN | Thermoplastic High Heat-resistant Nylon-coated | 90 °C | Dry | 600V | Most common building wire |
| THWN | Thermoplastic Heat/Water-resistant Nylon | 75 °C | Wet/Dry | 600V | Wet location rated |
| THWN-2 | THWN upgraded rating | 90 °C | Wet/Dry | 600V | Modern standard, replaces THWN |
| XHHW | Cross-linked Polyethylene High Heat/Water | 90 °C | Wet/Dry | 600V | XLPE insulation, better heat |
| XHHW-2 | XHHW upgraded | 90 °C | Wet/Dry | 600V | 90 °C wet or dry |
| USE-2 | Underground Service Entrance | 90 °C | Underground | 600V | Direct burial, sunlight resistant |
Selection Guidelines
- • THHN vs THWN-2: THWN-2 is wet location rated at 90 °C; preferred for modern installations
- • XHHW: XLPE insulation provides better heat resistance and thinner walls
- • Ampacity: Use 75 °C column for terminations unless marked 90 °C (NEC 110.14)
- • Colors: Black/Red/Blue (hot), White (neutral), Green/Bare (ground)
Cable Construction
Armored Cables
Metal Sheathed
Cables with metallic armor for physical protection. Used in industrial, commercial, and exposed residential applications. Provides equipment grounding path in some configurations.
Insulation
XLPE/PVC
Cable Types
5 types
Cable Type Specifications
NEC Article 310| Code | Full Name | Temp Rating | Location | Voltage | Notes |
|---|---|---|---|---|---|
| AC | Armored Cable (BX) | 90 °C | Dry | 600V | Flexible steel armor, bonding strip |
| MC | Metal Clad Cable | 90 °C | Wet/Dry | 600V | Interlocked metal tape or wire |
| MCI-A | MC Cable - Interlocked Aluminum | 90 °C | Wet/Dry | 600V | Aluminum armor, lighter weight |
| TC | Tray Cable | 90 °C | Cable Tray | 600V | Industrial cable trays only |
| PLTC | Power-Limited Tray Cable | 60 °C | Cable Tray | 300V | Low voltage control circuits |
Selection Guidelines
- • AC (BX): Bonding strip required for grounding; older residential construction
- • MC: Modern replacement for AC; includes equipment grounding conductor
- • Wet locations: Must be marked for wet location use; standard MC is dry only
- • Support: Every 6 ft and within 12 inches of boxes (NEC 330.30)
Cable Construction
Underground & Direct Burial
Burial Rated
Cables designed for direct earth contact without conduit. Moisture and corrosion resistant. Used for service entrance, feeders to outbuildings, and landscape lighting.
Insulation
XLPE/PVC
Cable Types
4 types
Cable Type Specifications
NEC Article 310| Code | Full Name | Temp Rating | Location | Voltage | Notes |
|---|---|---|---|---|---|
| UF-B | Underground Feeder (with ground) | 60 °C | Underground | 600V | Residential underground, sunlight resistant |
| USE-2 | Underground Service Entrance | 90 °C | Underground | 600V | Service entrance to building |
| URD | Underground Rural Distribution | 90 °C | Underground | 600V-35kV | Utility distribution, triplex/quadplex |
| MV-90 | Medium Voltage 90 °C | 90 °C | Underground | 2.4kV-35kV | Utility and industrial distribution |
Selection Guidelines
- • UF-B: Integrated ground wire; sunlight resistant for exposed sections
- • Cover depth: 24" for UF, 18" for RMC/PVC with GFCI (NEC 300.5)
- • USE-2: Service entrance only; cannot be used inside building (except short transition)
- • Warning tape: Install 6" above underground cables for future excavation awareness
Cable Construction
International Standards (IEC)
European/IEC Cables
Cable designations per IEC 60502 and harmonized European standards. Common in international projects and equipment. Different coding system from NEC.
Insulation
PVC/XLPE
Cable Types
6 types
Cable Type Specifications
IEC 60502| Code | Full Name | Temp Rating | Location | Voltage | Notes |
|---|---|---|---|---|---|
| NYM-J | PVC insulated, PVC sheathed (with ground) | 70 °C | Dry | 450/750V | European building cable |
| NYM-O | PVC insulated, PVC sheathed (no ground) | 70 °C | Dry | 450/750V | Without protective conductor |
| NYA | PVC insulated single core | 70 °C | Dry | 450/750V | Single conductor, conduit use |
| NYY | PVC insulated, PVC sheathed power cable | 70 °C | Wet/Dry | 0.6/1kV | Underground or indoor |
| N2XH | XLPE insulated, PVC sheathed, low smoke | 90 °C | Indoor | 0.6/1kV | Halogen-free, fire resistant |
| H07RN-F | Rubber flexible cable | 60 °C | Industrial | 450/750V | Flexible, oil resistant |
Selection Guidelines
- • NYM-J: "J" indicates protective conductor (ground); "O" without ground
- • NYY: Heavy-duty power cable; can be direct buried or in conduit
- • N2XH: Low smoke zero halogen (LSZH); required in public buildings
- • Voltage: U0/U notation (e.g., 450/750V) = phase-neutral/phase-phase