When installing underground service conductors to a building or structure, where the service conductors are installed in a trench that has 24 in. of cover, what marking is required at what distance above the underground installation? The underground service conductors are not encased in concrete.

  1. Marking is not required. Therefore, no distance is specified.
  2. A pressure-treated piece of lumber (2x4, painted red) is required to be installed directly over the underground installation.
  3. A red warning ribbon placed 24 in. above the underground installation is required.
  4. A yellow warning ribbon placed 12 in. above the underground installation is required.

Answer: D

When installing underground service conductors that are not encased in concrete and buried 18 in. or more below grade, you must place a yellow warning ribbon 12 in. above the underground installation. Note that this requirement applies only to service conductors.

The installation of warning ribbons above all underground conductors was once again proposed and commented on in the 2011 NEC cycle. However, no new requirements were approved by the Code-making panel members.

Owen is the owner and president of National Code Seminars and the holder of master electrician certifications in 46 states. He can be reached at necexpert@aol.com.