16.) The separation of Emergency System Conductors from other conductors.
700.9 Wiring, Emergency Systems (700.9 (B) Wiring)
Section 700.9(B) requires that wiring from an emergency source or emergency source distribution overcurrent protection to the loads be kept entirely independent of all other wiring and equipment unless it is otherwise permitted in 700.9(B)(1)-(4). These list items permit the emergency system wiring to be combined with: (1) the wiring from the normal source in transfer switches; (2) the wiring from another source in exit or emergency luminaires (light fixtures); (3) the wiring from another source in common junction box, attached to exit or emergency luminaries (light fixtures); (4) the wiring from a branch circuit supplying unit equipment in a common junction box where the emergency circuit wiring is supplied by the unit equipment.
There is often confusion related to the phrase "wiring from the emergency source to the loads or source distribution overcurrent protection to the emergency loads.." Although a much debated topic, this phrase means that we must keep the wiring from the emergency source to the emergency loads entirely independent of all other wiring or we must keep the wiring from the emergency source distribution overcurrent protection to the emergency loads entirely independent from all other wiring.
One of the common misapplications is to run a feeder from the source to one distribution panelboard and combining the emergency system overcurrent protection in the same enclosure with the legally required standby and/or optional standby overcurrent protection. Under this circumstance the "wiring" to the emergency loads has been combined in the same enclosure with legally required standby and/or the optional standby wiring. Therefore, the wiring to the emergency loads has not been kept "entirely independent of all other wiring." Note that none of the previously discussed items in 700.9(B)(1)-(4) permit this application. You would, however, be allowed to run two or more feeders from the source to separate panelboards. The first panelboard would contain strictly emergency system overcurrent protection and wiring and the other panelboard(s) could contain the legally required standby and/or the optional standby system overcurrent protection and wiring. In this case, the wiring to the emergency loads has been kept "entirely independent of all other wiring."
Where there is no overcurrent protection located at the source, it would be permitted to run one feeder to switchgear containing emergency, legally required standby and optional standby system overcurrent protection where the emergency source distribution overcurrent protection and wiring to the emergency load(s) is located in a separate section of the switchgear. Installed in this manner, the wiring from the emergency source distribution overcurrent protection to the emergency loads has been kept entirely independent of all other wiring.