300.3(2) Grounding and Bonding Conductors. Equipment
grounding conductors shall be permitted to be installed out-
side a raceway or cable assembly where in accordance with
the provisions of 250.130(C) for certain existing installa-
tions or in accordance with 250.134(B), Exception No. 2,
for dc circuits. Equipment bonding conductors shall be per-
mitted to be installed on the outside of raceways in accor-
dance with 250.102(E).
250.102(E) Installation. Bonding jumpers or conductors and
equipment bonding jumpers shall be permitted to be in-
stalled inside or outside of a raceway or an enclosure.
(2) Outside a Raceway or an Enclosure. If installed on
the outside, the length of the bonding jumper or conductor
or equipment bonding jumper shall not exceed 1.8 m (6 ft)
and shall be routed with the raceway or enclosure.