Types of Wire Used in Underground Construction

Underground Subway Tunnel With Wiring

Underground wiring and electrical infrastructure offer several advantages. There is less visual clutter along streets and between buildings, the wiring is protected from impact damage, and power suppliers can create more organized systems for power, communications, and more. However, underground electrical infrastructure faces unique challenges, such as moisture from the soil, exposure to harsh elements, and risks of electrical leakage. This is why underground construction projects need specialized wiring materials and robust electrical insulation.

Learn more about common underground electrical wire types and what materials to choose for your next project.

Why Insulation Matters

In underground wiring, choosing the right insulation material is as important as choosing the right wire or cable conductor. Different insulation materials protect against corrosion, contaminants, electromagnetic interference, and other hazards based on the wiring’s intended application. The electrical insulation acts as a mechanical barrier or conduit between the soil and the wire, preserving the integrity of the wire and preventing electrical leakage.

Types of Wire Used in Underground Construction

Compare some of the most common underground wire types to choose your preferred construction wiring solution.

USE-2 Cable (Underground Service Entrance, Type 2)

USE-2 are commonly used for underground wiring and applications such as connecting residential service panels to the utility supply. These cables are specifically designed for direct burial in the ground or in conduit. They’re black cables with an outer layer of cross-linked polyethylene (XLPE) insulation.

The conductors used in USE-2 cables are typically:

  1. Aluminum Conductors:
    • Aluminum Alloy (AA-8000 series): These conductors are lightweight, cost-effective, and have good conductivity. They are treated to resist corrosion and meet the requirements of the National Electrical Code (NEC) for underground installations.
  2. Copper Conductors:
    • Bare or Tinned Copper: Copper conductors are more conductive than aluminum and are often used in environments where higher conductivity or durability is required. Copper is also more resistant to mechanical damage during installation.

UF-B (Underground Feeder and Branch Circuit) Cable

UF-B cables are designed for underground applications and direct burial without requiring a conduit. They are commonly used for supplying power to outdoor or underground structures, such as outdoor lighting, pumps, and detached garages. UF-B cables are made with trapped bare copper wire surrounded by a durable polyvinyl chloride (PVC) insulation layer. This construction ensures the wire remains effective in environments with high moisture or UV exposure.

The conductors used in UF-B cables are:

  1. Copper Conductors:
    • UF-B cables almost exclusively use solid or stranded copper conductors because of copper’s superior conductivity and resistance to corrosion in underground and outdoor environments.
    • Conductors are often bare copper or tinned copper, depending on the specific requirements for conductivity and environmental protection.
  2. Aluminum Conductors (Less Common):
    • While less common, aluminum conductors can be used in some UF-B cables, particularly for cost savings in larger wire sizes.
    • These are typically AA-8000 series aluminum alloy conductors, which are treated to resist corrosion and comply with the NEC standards for underground feeder applications.

Copper Tracer Wire

Copper Tracer Wire, also known as locator wire or locating wire, is specifically designed to be buried alongside non-metallic underground utilities (such as plastic pipes or conduits) to aid in their detection and mapping using electronic locating equipment. These products are commonly used for fiber optics, utilities, and commercial or municipal projects. Part of what makes this product an ideal choice for more powerful installations is the high molecular weight polyethylene (HMWPE) insulation layer. This material is waterproof and even more resistant to scratches and abrasions than other electrical insulation options.

The conductors used in Copper Tracer Wire are:

  1. Solid Copper:
    • Most tracer wires use solid copper conductors because they provide excellent conductivity and durability, ensuring reliable signal transmission for utility locating.
    • Solid copper is the preferred choice due to its resistance to corrosion in buried applications.
  2. Copper-Clad Steel (CCS):
    • In some cases, copper-clad steel conductors are used as a cost-effective alternative. These conductors consist of a steel core with a copper cladding, combining the strength of steel with the conductivity of copper.
    • CCS tracer wire is less conductive than solid copper but is still effective for shorter runs and applications where mechanical strength is a priority.

Common Sizes:

  • The wire sizes typically range from #10 AWG to #14 AWG, with #12 and #10 AWG being the most common for long-distance signal transmission.

Aluminum URD (Underground Residential Distribution) Cables

Aluminum URD cables are specifically designed for distributing electricity to residential areas, often buried underground. They are commonly used in secondary distribution systems to connect the utility transformer to individual homes or buildings. This type of wiring is made from compressed aluminum with cross-linked polyethylene (XLPE) insulation.

The conductors used in Aluminum URD cables are:

  1. Aluminum Alloy (AA-8000 series):
    • The most commonly used conductor material in URD cables is AA-8000 series aluminum alloy.
    • These alloys are designed to meet the requirements of the National Electrical Code (NEC).
  2. Compact-Stranded or Concentric-Stranded Construction:
    • The aluminum conductors in URD cables are typically compact-stranded or concentric-stranded to ensure flexibility and durability during installation.

Best Materials for Underground Wire

Across the multiple underground wire types available, there are two main metals chosen for the wires: aluminum or copper. Copper, while more expensive, is more conductive. To mitigate these costs, AA-8000 aluminum alloys are a cost-effective solution to create wiring that behaves similarly to copper wires.

Copper

Copper’s main characteristics include:

  • High conductivity
  • Up to 40% higher tensile strength than aluminum
  • High ampacity without overheating
  • Manufacturability for creating everything from heavy gauge wiring to very fine wiring
  • Reliable long-term performance without ongoing maintenance requirements
  • Easy recyclability

Aluminum

Some projects may benefit from aluminum wiring because of its lighter weight and flexibility, which streamlines installation since wire pulls are easier over longer runs. Aluminum is also cheaper than copper, which can significantly reduce the cost of installations over larger areas.

Underground Electrical Wire Products From International Wire

At International Wire, we design and develop the wiring solutions builders and manufacturers need to create long-lasting installations. We serve aerospace, security and data, automotive, electrification, consumer manufacturing, oil and gas, and medical industries with high-performance wiring solutions. Contact us to learn more about our wide array of underground electrical wire types for different construction wiring projects.