230.50 Protection Against Physical Damage.
(B) All Other Service-Entrance Conductors. All other
service-entrance conductors, other than underground ser
vice entrance conductors, shall be protected against physical
damage as specified in 230.50(B)(1) or (B)(2).
(1) Service-Entrance Cables. Service-entrance cables,
where subject to physical damage, shall be protected by any
of the following:
(1) Rigid metal conduit
(2) Intermediate metal conduit
(3) Schedule 80 PVC conduit
(4) Electrical metallic tubing
(5) Reinforced thermosetting resin conduit (RTRC)
(6) Other approved means
(2) Other Than Service-Entrance Cables. Individual open
conductors and cables, other than service-entrance cables,
shall not be installed within 3.0 m (10 ft) of grade level or
where exposed to physical damage.
Exception: Type MI and Type MC cable shall be permitted
within 3.0 m (10 ft) of grade level where not exposed to
physical damage or where protected in accordance with
300.5(D).