Electrical wire carries power throughout every residential, commercial and industrial electrical system. Although different products may appear similar, conductor material, insulation, cable construction and environmental ratings determine where each type can be installed.
CAPO Supply carries copper and aluminum electrical wire in common sizes and configurations for branch circuits, feeders, service equipment, underground installations and other electrical applications.
Copper and Aluminum Conductors
Copper and aluminum are the two primary conductor materials used in modern building wiring. Both can provide safe, reliable service when the correct product is selected and installed according to its listing and application requirements.
Copper Wire
Copper is widely used for residential branch circuits, commercial wiring and equipment connections. It provides excellent conductivity and is available in solid and stranded constructions across a broad range of wire sizes.
Common copper-wire applications include:
- Lighting and receptacle circuits
- Appliance circuits
- Commercial branch wiring
- Equipment connections
- Grounding and bonding
- Control wiring
- Feeders and service conductors
Copper conductors are typically smaller than aluminum conductors carrying a comparable amount of current. Copper is also commonly selected where space is limited or where smaller branch-circuit conductors are required.
Aluminum Wire
Modern aluminum building wire is commonly used for larger feeders, service-entrance conductors and distribution applications. It is lighter and often more economical than copper, particularly in larger conductor sizes.
Common aluminum-wire applications include:
- Residential service entrances
- Main panel feeders
- Subpanel feeders
- Commercial distribution
- Large equipment feeds
- Multifamily construction
Because aluminum has different electrical and mechanical properties than copper, it generally requires a larger conductor size for the same application. Terminals, lugs and connectors must be identified for use with aluminum conductors, and connections must be prepared and tightened according to the equipment manufacturer’s instructions.
Common Types of Electrical Wire and Cable
The conductor material is only one part of wire selection. The product type determines where the wire may be installed and what protection it requires.
NM-B Cable
NM-B, often referred to generically as nonmetallic sheathed cable, is commonly used for residential branch-circuit wiring in dry locations.
Typical applications include:
- Receptacle circuits
- Lighting circuits
- Switch wiring
- Appliance circuits
- Interior residential wiring
NM-B cable contains insulated circuit conductors and an equipment grounding conductor inside a nonmetallic outer jacket. It is not intended for wet locations or direct-burial installations.
THHN and THWN-2 Building Wire
THHN/THWN-2 is an individual insulated conductor commonly installed inside conduit, raceways and approved wireways. Many current building-wire products carry both THHN and THWN-2 designations.
It is frequently used for:
- Commercial branch circuits
- Industrial wiring
- Panel and equipment feeders
- Conduit installations
- Service and distribution work
- Residential wiring installed in raceway
THHN/THWN-2 is available in multiple colors, conductor sizes and both copper and aluminum constructions. The exact environmental and temperature ratings should always be confirmed from the product markings.
XHHW-2 Wire
XHHW-2 is a cross-linked polyethylene insulated building wire used for feeders, services and distribution circuits. It is available with copper or aluminum conductors and is commonly selected for larger conductor sizes.
Typical applications include:
- Service-entrance conductors
- Panel feeders
- Commercial distribution
- Industrial equipment
- Wet or dry raceway installations
- Larger residential feeders
Its insulation provides resistance to heat and moisture, making it useful for demanding feeder and service applications.
UF-B Underground Feeder Cable
UF-B is designed for applications that may be exposed to moisture and is commonly used for underground residential wiring where permitted.
Typical uses include:
- Detached garages
- Sheds and outbuildings
- Outdoor lighting
- Pumps
- Underground branch circuits
- Exterior equipment
Unlike standard NM-B cable, UF-B has a construction intended for wet locations and direct-burial applications where permitted. Burial depth, physical protection and installation requirements still depend on the circuit and local code.
SER and SEU Service-Entrance Cable
Service-entrance cable is commonly used between service equipment, meters, panels and distribution points.
SER cable is frequently used for feeders to panels and subpanels. Its conductor arrangement can support applications requiring separate neutral and equipment-grounding paths.
SEU cable is used in specific service-entrance arrangements and other approved applications. It should not be treated as interchangeable with SER cable because its conductor construction and permitted uses differ.
The electrical system design and equipment configuration determine which service-entrance cable is appropriate.
MC Cable
Metal-clad cable contains insulated conductors inside a flexible metallic armor. It is widely used in commercial, institutional and industrial construction.
Common applications include:
- Commercial branch circuits
- Lighting systems
- Office construction
- Retail spaces
- Industrial installations
- Exposed work where permitted
- Projects requiring additional physical protection
MC cable can reduce the amount of field-installed raceway required in certain applications. Different versions are available for standard power, healthcare, fire alarm, lighting control and other specialized systems.
Solid and Stranded Wire
Conductors may also be solid or stranded.
Solid wire consists of one conductor and is common in smaller residential branch-circuit sizes. It holds its shape and is straightforward to terminate in many standard wiring devices.
Stranded wire is made from multiple smaller strands. It is more flexible and is commonly used in conduit, equipment connections and larger conductor sizes where pulling and bending solid wire would be difficult.
The appropriate construction depends on conductor size, installation method and terminal compatibility.
Selecting the Correct Wire
Wire should not be selected by color or conductor size alone. A complete selection considers:
- Circuit voltage
- Required ampacity
- Copper or aluminum construction
- Conductor size
- Insulation and temperature rating
- Dry, damp or wet location
- Indoor or outdoor installation
- Conduit or cable installation
- Direct-burial requirements
- Terminal temperature ratings
- Voltage drop
- Equipment and connector compatibility
- Local electrical-code requirements
A conductor’s insulation may have a higher temperature rating than the connected equipment terminals. The allowable ampacity must therefore be determined using the complete installation conditions rather than the wire insulation rating alone.
Wire Color and Circuit Identification
Insulation and jacket colors can help identify conductor function or cable size, but color should not be used as the only method of product selection.
Individual conductor colors commonly distinguish ungrounded conductors, grounded conductors and equipment-grounding conductors. Some manufacturers also use outer-jacket colors to help distinguish common NM-B cable sizes.
Always verify the printed conductor or cable markings before installation.
Quality Wire for Safe, Reliable Installations
The correct electrical wire supports safe operation, reliable connections and long-term system performance. Using an unsuitable cable type, undersized conductor or incompatible termination can result in failed inspections, overheating and premature equipment problems.
Whether the project requires residential NM-B, copper THHN, aluminum feeder wire, UF-B, XHHW-2, service-entrance cable or MC cable, CAPO Supply can help identify the proper product for the application.
Contact CAPO Supply for current wire availability, conductor sizes and assistance gathering the materials needed for your next electrical project.