Summary
Highlights
Article 300.5, 'Underground Installations,' has two primary changes in the 2023 NEC: the addition of cover/burial depth requirements for EMT in column 3 of Table 300.5(A) and expanded requirements for warning ribbons.
The central theme of 300.5 is the required cover depth for cables and raceways. For 'all locations not included below' (general requirements), rigid and IMC require 6 inches of cover. Direct buried conductors (like UF cable) need 24 inches, and non-metallic raceways (PVC, fiberglass) require 18 inches.
While EMT has always been permitted underground with corrosion protection, its specific burial depth was previously unaddressed. The 2023 NEC now specifies that EMT should be buried 18 inches deep, similar to non-metallic conduits like PVC and fiberglass, due to its comparative strength. EMT also requires corrosion protection, typically a four-mil tape.
Section 300.5(D) 'Protection from Physical Damage' now applies to all underground cables and conductors, including those within raceways, not just direct-buried ones. Conductors emerging from grade must be protected by an enclosure or raceway extending at least 18 inches below ground and 8 feet above.
A significant change is that service conductors, buried 18 inches or more, require a warning ribbon placed at least 12 inches above them in the trench. This applies to service conductors not under the exclusive control of the utility. This rule specifically applies to installations in a trench, not to methods like directional boring.
If a raceway protecting conductors is subject to physical damage, it must be made of suitable material, such as EMT, rigid metal conduit, IMC, RTRC-XW (extra wall), or Schedule 80 PVC or equivalent.