Electrical wiring is the backbone of any building’s electrical system, ensuring the safe and efficient transmission of power throughout a structure. Whether you’re a homeowner, a contractor, or an aspiring electrician, understanding the different types of electrical building wire is crucial for making informed decisions about electrical installations.
In this blog post, we’ll discuss the key types of electrical wire used in buildings, their applications, and why selecting the right wire is essential for safety and efficiency. Read on!
1. THHN and THWN/THWN-2 Wire
Thermoplastic High Heat-resistant Nylon-coated (THHN) wire is one of the most commonly used types of wire in residential and commercial buildings, featuring a single conductor with PVC insulation and a nylon coating. THHN wire is suitable for dry locations and is commonly used in conduit systems for wiring circuits.
Moreover, Thermoplastic Heat and Water-resistant Nylon-coated (THWN) is a similar type of wire but includes resistance to moisture, making it suitable for both wet and dry locations. THWN-2 improves on this with higher temperature ratings (up to 90°C in both dry and wet locations). These wires are typically used in conduit and are often found in new construction and upgrades.
2. Non-Metallic Sheathed Cable (NM-B)
Often referred to by the brand name Romex, NM-B cable is one of the most popular wiring types for residential indoor applications. It consists of two or more insulated conductors and a bare ground wire, all encased in a plastic sheath.
NM-B cable is used for lighting, outlets, and appliances. It’s easy to work with, but it must not be used in damp or wet locations, nor run through conduit outdoors. It’s rated for temperatures up to 90°C but must be installed in accordance with its ampacity limits.
3. Underground Feeder Cable (UF-B)
UF-B cable is similar to NM-B but designed for underground and wet locations. Its conductors are encased in solid thermoplastic insulation, making it resistant to moisture, sunlight, and corrosion. It’s commonly used for outdoor lighting, garden features, or bringing power to detached buildings like garages or sheds.
Because UF-B can be buried directly in the ground without conduit, it’s a popular choice for exterior wiring. However, it is more rigid than NM-B, which can make installation slightly more challenging.
4. Metal-Clad Cable (MC)
MC cable is composed of one or more conductors insulated with THHN/THWN wires, encased in a metal sheath, typically aluminum. This type of cable is suitable for use in commercial buildings, especially where added physical protection is required.
MC cable can be used indoors in dry locations and may be permitted in areas where fire resistance is critical. It provides grounding through the metal sheath and is easier to route than conduit systems, while still offering a high level of durability.
5. Armored Cable (AC)
Also known as BX cable, AC cable features a similar design to MC cable but includes a bonding strip inside the armor that serves as the grounding path. AC is generally used in older homes and commercial applications where conduit is not practical. Unlike MC, AC cable typically has paper insulation rather than plastic, which can make it less heat-resistant. While still used today, it’s less common than MC due to these limitations.
Choosing the right electrical building wire is essential for ensuring safety, performance, and code compliance in any wiring project. Each type of wire has its own strengths and ideal applications. By understanding the differences and knowing where and how each wire should be used, you can guarantee a more reliable and long-lasting electrical system. No matter the size of the project, using the appropriate electrical building wire helps create a safer, more efficient environment for everyone.
