312.8 Switch and Overcurrent Device Enclosures with
Splices, Taps, and Feed-Through Conductors. The wiring
space of enclosures for switches or overcurrent devices
shall be permitted for conductors feeding through, spliced,
or tapping off to other enclosures, switches, or overcurrent
devices where all of the following conditions are met:
(1) The total of all conductors installed at any cross section
of the wiring space does not exceed 40 percent of the
cross-sectional area of that space.
(2) The total area of all conductors, splices, and taps installed
at any cross section of the wiring space does not
exceed 75 percent of the cross-sectional area of that
space.
(3) A warning label is applied to the enclosure that identifies
the closest disconnecting means for any feedthrough
conductors.
