If you need to bury some electrical wire, the appropriate kind must be used. So, what type of wire can you bury underground?
Direct-burial cable (DBC) is designed to be buried underground, either with or without a conduit. This electrical cable has a protective plastic sheath that shields the internal wires from:
- corrosive soil particles
These features make DBC safe and reliable for outdoor use.
Do you need to run some wire underground? If so, the following information will give you the knowledge you need to select the correct type of wire.
Direct-Burial Cable: The Right Wire For Burying
There are myriad types of electrical wires, but only certain kinds are suitable for burying. The optimal wire for burying is a direct-burial cable (DBC), which is designed and manufactured for safe and reliable electricity transmission when buried underground and is sold on Amazon.
DBC consists of a dense collection of wires bound by a thermoplastic sheath. The protective outer layer provides an impenetrable seal that prevents the wiring from damage or corrosion by:
Note: This post may contain affiliate links which will take you to online retailers that sell products and services. If you click on one and buy something, I may earn from qualifying purchases. See my Affiliate Disclosure for more details.
- soil minerals
- temperature fluctuations
Due to its design, DBC has a formal rating for conditions that are:
The wires inside DBC are usually composed of copper or aluminum. Copper DBC is relatively expensive and can be bought on Amazon. The electrical conductivity of copper DBC is high because of the bronze-colored metal’s molecular properties.
In contrast, aluminum DBC is cheaper than burial cable made from copper and has lower conductivity, and is also sold on Amazon. However, recent technological innovations have produced a new class of aluminum DBC called AA-8000 is nearly as conductive as copper wiring.
Direct-Burial Cable For Home Use
The most widely-used DBCs are underground service entrance (USE-2) and underground feeder (UF-B) cables. Underground service entrance cables are black and connect homes and other buildings to electricity utility stations. This type of DBC is only for professional electricians.
NOTE: If you’re wondering if you can remodel a kitchen without a permit, read my article here to learn everything you need to know about it, from planning to finish.
In contrast, underground feeder DBC is for residential applications. This type of DBC is gray and resembles indoor non-metallic sheathed electrical wiring. Underground feeder DBC is for indoor and outdoor applications.
The wires inside underground feeder DBCs are individually wrapped in a robust sheath. The sheaths prevent the wires from touching each other and ensure their protection from dirt and moisture. Underground DBC also has UV resistance and can handle exposure to the sun in outdoor settings.
How to Bury DBC
As with any electrical work, it is essential to follow the correct procedure when burying wires. Here are some guidelines for installing DBC safely and effectively.
#1: Locate Service Lines
Before installing the DBC, the first step is to contact your local municipal authorities or utility providers to ascertain the location of service lines like underground water and sewerage pipes. The relevant officials or representatives will confirm the position of the service lines.
#2: Dig To The Proper Depth
Once you’ve identified where it is safe and permissible to bury the wiring, it is time to dig. When laying DBC, the trench must be sufficiently deep to prevent hazards and save the wiring from environmental damage.
If you bury the DBC with PVC conduit, the trench must be a minimum of 18 inches deep. The hole must be at least 24 inches if the DBC is buried without conduit because the wire lacks additional protection.
NOTE: Some jurisdictions have specific requirements about the depth to bury electrical wiring, so check the local codes to ensure you are legally compliant.
#3: Account For Voltage Drop
The amount of electricity that wires conduct decreases as their length increases. This phenomenon called voltage drop results from resistance in the wires, and the power consumption from the connected devices. It is crucial to account for voltage drop when burying DBC.
To calculate the voltage drop for a DBC, read the voltage meter at the breaker box (generally 120V) and the cable’s connection point. The difference between these two readings gives you the voltage drop for that particular cable, which is expressed as a percentage of total voltage at the start of the circuit.
For example, if the total voltage is 120V and the reading at the end of the circuit is 110V, the calculation would be 120V – 110V = 10V. This answer translates into a voltage drop of roughly 8%, which exceeds the National Electrical Code’s recommended maximum voltage drop of 3%.
When accounting for the voltage drop, it is essential to choose the correct size of DBC for the circuit. When burying a long stretch of DBC to connect two distant points, select a cable with a wide diameter to compensate for the voltage drop. Wider (or thicker) wires offer less electrical resistance than thinner wiring.
#4: Map The DBC’s Location
After the DBC is buried, it is essential to precisely map the location of the wiring. By mapping out the DBC’s position, you can avoid the risk of damaging the cable in the future. Drawing a map of the DBC’s location makes it easier to find the wiring if you need to assess or repair it.
FAQs About Burying Electrical Wiring
Here are the answers to some frequently asked questions about burying wires underground.
#1: Can I Bury An Extension Cord Underground?
It is not wise to bury extension cords underground because they are not fit for this purpose.
These cables don’t have protective sheaths. If you bury an extension cord in the ground, moisture and abrasive soil particles will damage it over time.
Once damaged, the cords won’t conduct electricity effectively and may pose safety risks. For these reasons, you should select the appropriate type of cables that are for underground burial.
#2: Do I Have To Put Direct-Burial Cable In a Conduit?
Placing DBC in the PVC conduit before laying it in the trench is not essential. As its name suggests, DBC is meant to be buried and has an outer layer that protects its wiring from the elements. As a result, DBC is typically buried without conduit.
Having said this, burying DBC with conduit offers additional protection. Using conduit might be advantageous if the DBC is in an area exposed to:
- potential water leaks
- construction earthworks
- other damaging activities and events
However, using conduit is not a prerequisite when burying DBC.
The safest and most reliable type of electrical wire for burying is DBC. This wire has a tough plastic sheath that protects it from being damaged by moisture and the surrounding soil.
You can bury DBC with a conduit to provide extra protection. However, DBC is so robust you can bury it without conduit.
You might also be interested in: