Types of Building Wires
News 2025年4月1日 12
Building wires form the fundamental electrical infrastructure of residential, commercial, and industrial structures. These conductors carry power throughout buildings, connecting electrical panels to outlets, switches, and fixtures. Understanding the various types of building wires is essential for proper electrical system design, installation, and maintenance. This guide examines the major categories of building wires, their specific applications, and distinguishing characteristics.
- Non-Metallic Sheathed Cable (NM)
Description:
– Commonly called “Romex” (a popular brand name)
– Contains 2-4 insulated conductors plus a ground wire
– Protected by an outer PVC jacket
Types:
– NM-B: Standard version for dry, indoor locations
– NMC: Moisture-resistant for damp locations
– NM-B-90: Higher temperature rating (90°C)
Applications:
– Residential branch circuits
– Commercial office wiring
– Lighting circuits
Advantages:
– Easy to install
– Cost-effective
– Flexible for routing through framing
- Underground Feeder Cable (UF)
Description:
– Similar to NM cable but with moisture-resistant design
– Solid plastic sheath encases conductors
– Direct burial rated
Applications:
– Outdoor lighting circuits
– Garage/shed power feeds
– Landscape wiring
Key Features:
– UV-resistant for outdoor exposure
– Doesn’t require conduit when buried
– Resists moisture and soil chemicals
- Thermoplastic-Insulated Wires (THHN/THWN)
Description:
– Single conductors in PVC insulation
– Common types:
– THHN: Heat-resistant nylon-coated
– THWN: Water-resistant version
– THWN-2: Improved water/heat resistance
Applications:
– Conduit wiring systems
– Service entrance conductors
– Panel feeders
Benefits:
– Higher temperature rating than NM cable
– More protection in conduit systems
– Available in wide range of gauges
- Metal-Clad Cable (MC)
Description:
– Insulated conductors in flexible metal armor
– Contains aluminum interlocked armor
– Includes grounding conductor
Types:
– Standard MC: Aluminum or steel armor
– MC-HL: High-temperature version
– MC-Lite: Reduced weight design
Applications:
– Commercial building power
– Industrial facilities
– Exposed installations
Advantages:
– Physical protection without conduit
– EMI/RFI shielding
– Suitable for exposed runs
- Service Entrance Cables (SE)
Description:
– Heavy-duty cables for main power feeds
– Two main types:
– SER: Round service entrance
– SEU: Flat underground service
Construction:
– Aluminum or copper conductors
– XLPE or PVC insulation
– Weather-resistant jacket
Uses:
– Main panel connections
– Meter base to panel runs
– Overhead service drops
- Specialty Building Wires
Low-Voltage Wiring:
– Category 5e/6/6a for data
– Coaxial cables for video
– Speaker wires
Fire Alarm Cables:
– FPLP: Power-limited fire protective
– FPLR: Riser-rated version
– FPL: Plenum-rated
Appliance Wiring:
– Flexible cords (SJ, SV, etc.)
– Range and dryer cables
– HVAC wiring
- Selection Considerations
Key Factors:
– Voltage rating: Match to system requirements
– Ampacity: Proper conductor sizing
– Environment: Indoor/outdoor/moist locations
– Temperature: Ambient and conductor heating
– Codes: NEC or local regulations
Installation Methods:
– Conduit vs. cable systems
– Concealed vs. exposed runs
– Plenum vs. non-plenum spaces
Building wires come in numerous specialized types to meet the diverse needs of modern structures. From basic NM cables in homes to robust MC cables in commercial buildings, each type serves specific purposes in electrical systems. Proper selection requires understanding the application environment, electrical requirements, and applicable codes. By choosing the appropriate wire type for each application, electricians and engineers can ensure safe, reliable, and code-compliant electrical installations that will serve buildings effectively for decades.