jar546
CBO
Alternate Power Source
Definition (NEC 2023)
One or more generator sets, or battery systems where permitted, intended to provide power during the interruption of the normal electrical service; or the public utility electrical service intended to provide power during interruption of service normally provided by the generating facilities on the premises. [99:3.3.4] (517) (CMP-15)
Explanation
The definition of “Alternate Power Source” in the 2023 NEC establishes that such sources include generator sets and, where allowed by the Code, battery systems. These systems are intended to maintain electrical continuity during an interruption of normal service. The definition also recognizes that a public utility electrical service can function as the alternate source when the premises are normally powered by on-site generation facilities.
This definition plays a critical role in healthcare facilities and other essential installations. Section 517.30(B) specifies the types of alternate power sources permitted to serve the Essential Electrical System (EES), ensuring reliability of critical life-safety and patient-care functions. Additionally, Section 517.31(B)(2) allows these alternate power sources to serve not just a single facility, but multiple contiguous buildings within a healthcare campus through a centralized alternate power plant.
In practical terms, this means the Code provides flexibility in how facilities can meet reliability requirements. A hospital, for example, may utilize multiple diesel generator sets, a large-scale battery system, or even an external utility feed depending on how the normal power is supplied. The ultimate goal of the definition is to ensure that power interruptions do not jeopardize critical services or life safety.
Definition (NEC 2023)
One or more generator sets, or battery systems where permitted, intended to provide power during the interruption of the normal electrical service; or the public utility electrical service intended to provide power during interruption of service normally provided by the generating facilities on the premises. [99:3.3.4] (517) (CMP-15)
Explanation
The definition of “Alternate Power Source” in the 2023 NEC establishes that such sources include generator sets and, where allowed by the Code, battery systems. These systems are intended to maintain electrical continuity during an interruption of normal service. The definition also recognizes that a public utility electrical service can function as the alternate source when the premises are normally powered by on-site generation facilities.
This definition plays a critical role in healthcare facilities and other essential installations. Section 517.30(B) specifies the types of alternate power sources permitted to serve the Essential Electrical System (EES), ensuring reliability of critical life-safety and patient-care functions. Additionally, Section 517.31(B)(2) allows these alternate power sources to serve not just a single facility, but multiple contiguous buildings within a healthcare campus through a centralized alternate power plant.
In practical terms, this means the Code provides flexibility in how facilities can meet reliability requirements. A hospital, for example, may utilize multiple diesel generator sets, a large-scale battery system, or even an external utility feed depending on how the normal power is supplied. The ultimate goal of the definition is to ensure that power interruptions do not jeopardize critical services or life safety.