13.) The improper supply for emergency unit equipment.
This problem is most common where battery units are used to supply power to emergency lighting and exit signs. Section 700.12(E) requires that a branch circuit supplying unit equipment must originate from the same branch circuit that feeds the normal lighting in the area where the emergency equipment is located. It also must be connected ahead of any local switches. The exception allows the branch circuit, supplying power to unit equipment, to be connected directly to a panelboard that is serving the normal lighting for an uninterrupted area that has at least 3 normal lighting circuits serving the area.
Example: Emergency lighting and exit signs have been provided for a small restaurant that has two separate dining rooms which are off of a common hallway. The hallway leads to the counter eating area where the main entrance/exit is located. The emergency power is supplied by a battery unit that is located in the hallway.
There are two heads on the unit for the hallway and remote heads and exit signs in each of the dining rooms and the counter eating area. The normal lighting for the hallway and one dining room is supplied from the same branch circuit. The normal lighting for the other dining room and counter eating area are supplied from another branch circuit. Both branch circuits originate from the same panelboard. An individual branch circuit has been run to the panelboard to supply power to the battery unit. The problem with this installation is that the battery unit is not supplied by the same branch circuit that is serving the normal lighting in the areas where the emergency lighting and exit signs are located. Two separate units, one unit connected to each normal lighting branch circuit, would meet the intent of Section 700.12(E). Even if the areas in the example were not separated by walls (uninterrupted area) an individual branch circuit would not meet Code because there are only 2 normal lighting branch circuits. Most often the exception, which allows for the individual branch circuit to be supplied directly from the lighting panelboard, comes into play in large office areas, telecommunication areas, assembly areas, etc..