Emergency is emergency is emergency, right? If it is from the generator distribution system, then it must all constitute as emergency power. Well, no. I cannot tell you how many times I have walked into an existing health care facility and seen the dreaded “E” power. “E” power constitutes all things generator supplied — together with no separation of systems. Unfortunately, there is still confusion regarding the code-required separation of systems in a health care facility. It is different from other types of occupancies.
To confuse matters from the start, the 2014 Edition of NFPA 70 (National Electrical Code) now refers to the three branches of generator power as “essential systems.” The term “emergency” is no longer referenced as a defining quantification in Art. 517. However, other sections of the NEC still reference “emergency” power.
The essential systems in a health care occupancy consist of life safety branch, critical branch, and equipment branch. Life safety branch is what it sounds like; it is the power required to safely egress the building and includes egress lighting, exit signs, powered doors in the path of egress, and the fire alarm system. To add confusion to the limitations of this branch of power, the NEC also includes elevator controls and lights, generator set accessories, medical gas alarms, and other communications and notification systems required to egress the building. This does not include elevator power, medical gas pumps, or the public address system that plays the lullaby when a baby is born in the hospital.
The critical branch is more straightforward with its requirements, but also leaves some room for interpretation. The intent is power for “direct patient care.” If it directly affects the wellbeing of a patient, it is on critical branch. The basic definition is receptacles and lighting in patient care areas. There is also a “catch all” section of the NEC [517.33(A)(9)] that allows “additional task illumination, receptacles, and selected power circuits needed for effective hospital operation.” The code does not provide any additional guidance regarding this section. As electrical designers, we need to use our judgment on what this specific part of the NEC constitutes that is not already indicated in the previous eight subparts of Sec. 517.33(A). Be mindful that other portions of the Code require normal branch, or an alternate critical branch, source of power in most locations that require critical power. You cannot only serve patient care areas with a single source of critical branch power.
The final choice for the essential systems is equipment branch power. This, again, is rather intuitive regarding what is required on this source of power. This is where our medical gas equipment and other mechanical systems reside. The items required to be either on automatic or delayed equipment branch power include systems such as operating room HVAC, heating for patient rooms, or cooling for data rooms. But fear not, those items that are not in the “required” equipment branch power list still have the opportunity to receive generator power. They are permitted to be on the “optional” branch of power. Often we see radiology equipment, non-patient care HVAC units, and chillers on this branch of power.
Each system is required to be separated from other sources with a few exceptions. Even after all the years I’ve been designing electrical health care infrastructures, I still find myself going back to Art. 517 to confirm the current requirements for the more unique systems in the facility. It is always best to refer back first to the word of the Code and then the intent of the Code to assure a compliant essential systems distribution.