(a) If there is a reduction of potential of the normal source by 15 to 40 percent, the loads under Sec. 112.15-1 must be automatically supplied from the temporary emergency power source.
(b) For systems in which a reduction of frequency of the normal source or final emergency power source adversely affects the emergency system and emergency loads, there must be means to transfer the loads under Sec. 112.15-1 to the temporary emergency power source upon a reduction in the frequency of the normal source or final emergency power source.