UF-B Direct Burial Cable vs. USE Direct Burial Cable: What Is The Difference?

USE and underground feeder cable UF-B are some of the most popular direct burial wires worldwide. The wire and cable industry establishes strict rules for direct burial; however, USE and UF-B are often confused.

The main difference between the two is that USE/USE-2 cable connects utility power to service panels, while UF-B is for outdoor residential and light commercial applications.

 Want to settle the UF-B vs. USE debate once and for all? Read this blog.

Understanding USE Cables

USE cables are mainly designed for utility applications, carrying power between utility transformers and individual homes. The power is carried from a utility company's power supply to the main service panel of a building. The term "USE" stands for an underground service entrance cable. 

These electrical service cables are outdoor-friendly, moisture-resistant, and designed to withstand all environments. USE cables typically have a rubber-based or cross-linked polyethylene insulation. As a rule, they are only used under the ground for direct burial. USE/USE-2 are less flexible than UF-B and more difficult to install.

USE cables are mostly installed and handled by the representatives of the utility companies. 

USE/USE-2 cables are usually color-coded in black. There are different, less commonly available colors on the US market; however, black insulation provides a much-needed resistance to sunlight, so most aim for a black cable. 

Unlike UF-B, which always has a copper conductor, USE/USE-2 can have an aluminum conductor.

One of the most important things about USE-2 is that it is banned for interior wiring by the National Electrical Code because it does not have a flame-retardant covering. Installing USE cable within residential walls for internal wiring could lead to a fire hazard if the cable overheats or is exposed to a short circuit. USE and USE-2 are also never used above the ground, aside from when utility professionals must discharge the service equipment. 

According to the National Electric Code, if the USE/USE-2 cables have a gauge of 4/0 AWG or smaller, they can be used for underground electricity applications, for which UF-B cable is a common choice. However, they are not used above the ground or to connect interior and exterior wiring. Utility applications are the main ones for USE cables, and it is rare for someone to decide to use them for another underground purpose besides utility applications. 

USE/USE-2 cables connect the power supply from the utility's distribution system to the service panel of a building. This includes the run from the transformer to the building's meter and from the meter to the primary service panel.

USE/USE-2 cables are covered in NEC articles 310 and 338.

USE vs. USE-2 Cables: Temperature Concerns

USE-2 is an upgraded version of USE, even though it has the identical purpose of connecting the service entrance to a distribution point. Regular USE cables are rated 75C, whereas USE-2 is rated 90C. USE-2 has better environmental and heat resistance than USE. The insulation of USE is usually double-rated as RHW or XHHW, whereas the insulation of USE-2 is double-rated as RHW-2 or XHHW-2. Both cables are rated for 600V.

Understanding UF-B Underground Feeder Cables

Like USE, UF-B cables are applied outside and for direct burial. UF-B cables are designed for direct burial and supply power from buildings to outdoor fixtures, structures, and equipment without additional conduit protection. They are commonly used in residential and light commercial applications due to their versatility and ease of installation.They carry the energy from the residential and commercial buildings to the outdoor constructions. 

The design of UF-B is the most similar to that of the NM-B wire, and it is only for outdoor underground applications. F-B cables typically have thermoplastic insulation with a rugged outer jacket. The name "UF-B" means underground feeder cable, type B. Similar to USE, the cables are resistant to moisture and sunlight. In UF-B cables, each conductor is individually insulated before being bundled within the outer jacket.

Standard UF-B cables are rated for a maximum operating temperature of 60°C, lower than 75°C for USE and 90°C for USE-2. The cables are rated for 600V and always have a copper conductor. 

Unlike USE, UF-B cables are permitted to be used in exterior constructions above the ground by the National Electrical Code; however, they need to be in conduit for extra protection.

Aside from direct burial purposes, they can be used as the NM-B wire inside the house if they comply with NEC 2020 requirements. Homeowners often use them to connect the outdoor constructions in their homes, such as garages, pumps, or lighting fixtures, with the interior wiring. UF-B cables are often colored in gray, though it may vary depending on the manufacturer.

UF-B cables are covered in NEC Article 310.

UF-B vs. UF: Do Not Confuse Them

UF-B cables are often confused with UF cables, which are underground feeder electrical wires. However, the letter B indicates the cable is suitable for direct burial. The regular UF cable can be buried in a conduit. It does not have the same robust outer jacket that UF-B does. The difference is that UF-B construction indicates better water and corrosion resistance. UF cables are less common today; you are more likely to encounter UF while shopping.

UF-B vs. USE Applications Compared

Let's delve into more details on the applications of USE and UF-B cables:

USE/USE 2 Applications

• USE and USE-2 cables are primarily used to connect the utility company's power supply to the main service panel of a home or building. This includes the run from the transformer to the building's meter and from the meter to the main panel. 
• Both USE and USE-2 are suitable for direct burial without additional conduit or protection. This makes them ideal for installations where cables need to run underground over long distances, such as in rural or large residential properties.
• USE-2 cables, in particular, are enhanced to withstand various environmental conditions, including moisture and heat. They can be used in damp locations.
• USE and USE-2 are generally not used inside buildings because they lack specific safety ratings, such as flame resistance required for indoor applications.
• Some potential specific use cases of USE/USE-2 cables are service entrances in individual housing, especially in rural areas, commercial building power supply, or outdoor power supply on a farm.

UF-B Applications

• UF-B cables often supply power to outbuildings like garages or barns from a main building. They can be used above ground when protected by conduit or directly buried beneath it.
•  UF-B is also suitable for running power to exterior lighting fixtures, security systems, and other outdoor applications.
• UF-B is suitable for use in basements and wet/dry areas.
• In addition to external uses, UF-B cable can be used inside buildings for wiring fixed appliances, receptacles, and other circuits.
• Actual residential use cases of UF-B are supplying power to a detached garage, installing outdoor lighting, power  

UF-B vs. USE vs USE-2 Ampacity Table

Recommendations For Direct Burial of UF-B and USE Cables

The National Electrical Code (NEC) provides specific recommendations for the minimum burial depth of electrical cables. Here are the general NEC guidelines for the direct burial depth of USE and UF-B cables:

• Both USE and UF-B cables must typically be buried at a minimum depth of 24 inches (610 mm) below grade for residential applications. This depth protects from physical damage and is a common standard for general installations. This is specified in NEC Article 300.5 on underground installations.
• The burial depth can be reduced if the cable is installed under a minimum of 2 inches (51 mm) of concrete or equivalent protection. The depth can be reduced to 18 inches or even less in such cases.
• Another method to reduce the required burial depth is to use a rigid or intermediate metal conduit or nonmetallic conduit rated for direct burial. 
• Both USE and UF-B cables buried at insufficient depths are more susceptible to damage from routine yard maintenance like digging or aeration. This can lead to cable exposure or damage, causing short circuits, ground faults, or electrocution. A common example of this mistake is being electrocuted while gardening because you installed a UF-B cable just a few inches below the ground.
• Additional precautions like deeper burial (potentially more than 24 inches) or enhanced protective encasements might be necessary in areas where the cable might be subjected to vehicular traffic or similar risks. This ensures that the cables are shielded from potential damage from such environmental stresses.

UF-B vs. USE Direct Burial Cables: The Bottom Line

All in all, USE is a utility service entrance cable that is used exclusively outdoors and underground, whereas UF-B is a more versatile direct burial cable that is used for mixed interior and exterior applications. If you are an individual user installing cables on your property, you are way more likely to encounter and use UF-B than USE. USE cables have way less versatility and are usually managed by utility experts. Since USE cables have an aluminum conductor, they are slightly cheaper than their UF-B counterparts. When working with USE and UF-B direct burial wiring, knowing the difference between USE/USE-2 and UF/UF-B is essential. 

Nassau National Cable offers you a choice of Aluminum RHH/RHW-2/USE-2 90°C XLPE Insulation 600V, XLP USE-2 RHH RHW-2 Copper Conductor Building Wire, or Underground Feeder Cable UF-B Copper 600V. All of these are excellent underground electrical wires made from the best materials by the top manufacturers.