This is usually a 120/240-volt service for a residential or small commercial consumer. These wires are buried in a trench 24 inches deep when installed, measured from the top of the conduit or service wire to the top of the trench.
Dig 24 inches. At 24 inches you can bury underground feeder cable, using PVC conduit to 18 in. below ground only where the wire comes up. If you're considering running a power lineunderground through your yard, you have four options.
3. Electrical Wire Encased in PVC Conduit. The National Electric Code (NEC) sets the required burial depth of electric wire in rigid, non-metallic conduit, such as PVC, at 18-inches. Cable in any conduit, including PVC, that is buried at this depth is not in danger of being severed or disturbed by normal digging.
Laying outside line. When you are digging the trench for your new waterline, be sure the waterline is 12-inches below the local frost depth, but in no case less than two feet underground.
In the Triad (as in most of North Carolina), water and sewer lines only need to be buried 12 inches deep. This is to accommodate the frost depth of the region, which rarely goes below nine inches. In the mountains, careful plumbers will install pipes closer to 18 to 24 inches, even though code only calls for 12.
Main lines are generally found at least 24 inches deep, while service lines are gener- ally found at least 18 inches deep. Keep in mind: existing grades can change and the current depth of an electric or natural gas line may be different than when originally installed.
How deep are your pipelines buried? The top of natural gas pipelines are at least 30 inches (2 ½ feet) below the ground's surface when installed.
|SERVICE ENTRANCE CONDUCTORS SIZE AND RATING|
|Service or Feeder Rating||Copper Conductors||Aluminum or Copper-Clad Aluminum|
|100 Amps||#4 AWG||#2 AWG|
|125 Amps||#2 AWG||#1/0 AWG|
|150 Amps||#1 AWG||#2/0 AWG|
The standard utility pole in the United States is about 40 ft (12 m) long and is buried about 6 ft (2 m) in the ground. However, poles can reach heights of 120 ft (37 m) or more to satisfy clearance requirements.
When working around buried facilities, remember that main lines are typically at least 2 feet deep while service lines are only at about 18 inches deep. Existing grades can change and the current depth may be different when it first was installed.
I live in Texas, where water lines are about 24 inches deep and gas lines are about 5 feet deep. The idea for water lines is to bury them deep enough they won't freeze in winter, so the further north you are the deeper they are under the ground.
Anywhere UF cable is exposed above the soil, it must be protected with conduit. Not all types of conduit can be buried in the soil. EMT (Electrical Metallic Tubing) and flexible “Raintite” are not considered suitable for burial. Aluminum Rigid will corrode away in certain soils, such as clay, or in moist areas.
THHN Wire. The most popular type is THHN wire. THHN stands for Thermoplastic High Heat-resistant Nylon coated. THHN can come in stranded or solid conductors depending on the size. It is either manufactured in copper or aluminum and covered in a PVC (polyvinyl chloride) insulation with a nylon jacket.
Gas: No standard depth; 24 inches average, 36 preferred. Sewage: 24 to 36 inches in most parts of the country. Water: 36 inches is national standard; can be any depth if not subject to freeze. Telephone: If line is in conduit, can safely be at any depth; without conduit, should be at least 24 inches.
Direct burial cable is a special type of electrical wiring, or cable, that is designed to be run in a trench underground. The electrical wires in the cable are encased in a thermoplastic sheath that seals out moisture and protects the wires within.
Intermediate metal conduit (IMC) is a steel tubing heavier than EMT but lighter than RMC. It may be threaded. Electrical metallic tubing (EMT), sometimes called thin-wall, is commonly used instead of galvanized rigid conduit (GRC), as it is less costly and lighter than GRC.
5 - Cable Depth. You should bury your cable around 18 inches deep. You should also call your city's building code office and see if there is a municipal code that specifies the depth for buried cable. Some municipalities require a 24 inch depth.
The NEC does not allow you to run CABLE in conduit unless it is to sleeve the conduit for protection and the conduit can't exceed 24 inches in length. UF cable is designed to be directly buried. Either that or run conduit and single THHN conductors.
Buried conduit and conduit installed in a wet location are considered wet locations. 7. You may use UF and MC cable in wet locations including outdoors and underground if it is not subject to damage. Use sunlight resistant NM and UF cable if the cable is exposed to direct sunlight.
Type UF-B may be installed as interior wiring in wet, dry, or corrosive locations at temperatures not to exceed 90°C (with ampacity limited to that for 60°C conductors) as specified by the NEC. Type UF-B may be used where exposed to direct rays of the sun or underground, including direct burial.