What Is a Direct Burial Wire?


What Is a Direct Burial Wire?

Direct burial wire is a type of outdoor electrical wire that is buried underground, usually without conduit. Naturally, these cables have to possess distinct characteristics to withstand the environment of the ground. They are sturdier than other types of outdoor cables, pass crush-resistance and water-absorption tests, and are resistant to the impact of moisture and soil. They are also designed to withstand the effects of different temperatures. Some direct burial cables are enhanced with armor that protects them from rodents. Direct burial cables are approved to use in wet, dry, and moist conditions. They are used in underground power lines, post lights, sprinkler systems, connecting indoors to underground, and locating other buried pipes.

Why Choose A Direct Burial Cable?

Direct burial wires possess critical advantages over overhead SE lines, even if we are accustomed to believing otherwise. Overhead power lines run at an easy risk of becoming exposed or damaged by natural conditions. They are especially dangerous in natural disasters, which is a point that should be seriously considered in the coastal United States, where hurricanes and storms are a common risk. Direct burial cables do not have all these disadvantages by their installment, which makes them perfectly safe. Therefore, it is natural that direct burial wires currently possess a preference over overhead power lines, and new residential zones overwhelmingly rely on them. However, it should be noted that underground power lines are way more expensive due to their installation expenses. 

Things You Should Know About Direct Burial Wires

  • Conductors of underground cables are made both from copper and aluminum. While copper is considered superior by many due to its higher electrical conductivity, aluminum is often used because it is inexpensive. Given the overall high cost of underground power lines, reducing the price is a priority for most utility companies. Luckily, modern AA-8000 series aluminum alloys have properties that are quite similar to copper.
  • Common insulations used with direct burial cables are XLPE, PVC, and HMWPE. They are resistant to moisture, abrasion, and temperature changes.
  • While direct burial cables are most commonly buried without conduit, galvanized metal, metal, or PVC ducts can sometimes be used for extra protection in some cases, though this is not a legislative requirement. In particular, conduit ensures superior protection from rodents. However, installing wire in conduit runs with extra costs and challenges; therefore, you should proceed with caution.
  • Direct burial cables are buried 24 inches deep in the soil, and 18 inches deep when protected by concrete. However, you should check your local requirements before proceeding with installation, as the rules may differ depending on the state, type of soil, and other conditions unique to the place where you reside.
  • Few days before installing underground cables, you are legally obliged to inform utility services in your city or area by calling 811. 
  • You should consider upcoming landscaping projects for years to come before choosing a pace for underground cable work. Also, keep a detailed map of the area where underground cables are installed for future reference.
  • You may want to go a size up to minimize the power loss caused by voltage drops in case the project is large and cables are expected to run a long distance.

Types of Direct Burial Cables

Common types of cables with a copper conductor suitable for direct burial are USE-2, UF-B Underground Feeder Cable, and Tracer Wire. Aluminum URD Direct Burial Wire is the most commonly used direct burial aluminum wire. Let us focus on these cables in more detail to help you understand the difference.

USE-2, or service entrance transmission cables, are commonly used in underground power lines that carry electrical energy from transformers to residential buildings. They are not used for other underground purposes. These cables have durable XLPE insulation that withstands harsh conditions and a conductor made of annealed soft bare copper.

UF-B Underground Feeder Cable is suitable for both indoor and outdoor applications. Therefore, as a direct burial cable, it can connect the house with an outdoor power hub located outside, for instance, in the garden. UF-B cables have a stranded bare copper conductor and a PVC insulation resistant to moisture, grease, and corrosion. Additionally, this cable is well-protected against sunlight.

Copper Tracer Wire's goal is to help locate pipes and other underground cables. It is most commonly used by professionals in the utility industry, including the companies that deal with water, gas, and the installation of fiber optics. Tracer wires are insulated with HMWPE polyethylene that is waterproof and has superior abrasion resistance.

Aluminum URD Direct Burial Wire is used in direct burial electrical power distribution when secondary power distribution circuits are required. This cable is available in Single, Duplex, Triplex, and Quadruplex variations. The cables have 1350-H19 series compressed aluminum conductors and XLPE insulation, proven to be one of the best for underground use.

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