How to Install an Underground Power Cable


The difficulty of installing underground power cable depends on the size of the cable being installed. Very small installations, such as installing a 120V line, can be done by hand. Large installations, such as a 7.2kV line, require additional equipment to meet the National Electrical Code's depth requirements. Check this code before beginning any electrical installation.

Things You'll Need

  • National Electric Code
  • Method of digging such as a shovel or trencher
  • Electrical cable
  • Contact your permitting department and request an electrical permit. The electrical inspector will come out and inspect each part of your installation.

  • Mark the path the electrical cable will take by spray-painting the ground. Call your state's "one call" number to have the utilities on your property located. The "one call" number notifies all of the utilities in that area that you will be digging around their equipment and cable. They will then come out and mark where their material is so you can avoid hitting it when digging.

  • Check the National Electric Code (NEC) for the depth of your installation. The code gives specific depth requirements for different types of electrical installations. For example, 120V wire cable can be placed about 18 inches deep if part of the area above the wire is concrete.

  • Begin digging the ditch or trench between points A and B. This is usually easier with a trenching machine when long distances are involved. Once the trench is dug, use a tape measure to measure the trench depth. It must be greater than or equal to the value required by the NEC. Call the electrical inspector to inspect the trench. He will either pass or fail the trench. If it fails, he can tell you how to proceed.

  • Lay the cable along the bottom of the trench. Once all the wire is in the trench between points A and B, cover the cable with dirt or cement, if you are encasing the wire. Another option is to place conduit in the trench. Once that is done, pull the wire through the conduit.

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