Hospital Emergency Distribution System

[Sonny Stas]

I have been having a discussion with engineers about the design of hospital Emergency Distribution system. The engineer is using section 700 and refers to Exhibit 700.3(page 2 of attached is a project specific layout). I am using section 517.30 and informational note figure 517.30, No.1 (page 1 of attached is a project specific layout).

In short I am trying to determine the correct interpretation of two seemingly conflicting sections of the NEC 517 and 700. Which one is to be used and what circumstances would one apply to each diagram?

 

[steve66]

I have been having a discussion with engineers about the design of hospital Emergency Distribution system. The engineer is using section 700 and refers to Exhibit 700.3(page 2 of attached is a project specific layout). I am using section 517.30 and informational note figure 517.30, No.1 (page 1 of attached is a project specific layout).

In short I am trying to determine the correct interpretation of two seemingly conflicting sections of the NEC 517 and 700. Which one is to be used and what circumstances would one apply to each diagram?

I'm not sure what you see in 517.30 that would indicate exhibit 700.3 doesn't apply? If you are referring to the diagram, I would say it just doesn't have enough detail to show the separation required by 700.3. (That diagram has also been in the code longer than 700.10(B)5, so maybe the diagram could use some updating.)

In general, if you have over 150KVA, you need separate transfer switches. And the breakers that supply emergency transfer switches, legally required ATS's, and optional loads must be separated per 700.3.

There has been some debate over where the life safety, critical, and equipment branches fit into emergency or legally required.

I personally think that the splices give more chance for a problem than having the breakers in the same panel, but that's just my opinion. There are other ways to get the separation.

 

[RB1]

Sonny,

Exhibit 700.3 does not aply to health care facilities. During the development of NFPA 99-2012 the Technical Committee on Electrical Systems sought to distinguish the requirements for essential electrical systems for health care facilities from those of emergency systems as used in Article 700. This was accomplished by dropping the use of the term "emegency system" and including new language to Section 6.4.2.2.1.2 that provides the following: "The division of the branches shall occur at the transfer switches". Therefore, the separation requirements of 517.30(C) do not apply to the conductors from the generator to the essential system panelboard as shown in your drawing. The engineer's design doesn't violate the code, but separate enclosures are not required.

The prohibition of emergency system wiring from entering the same enclosure or raceway with other wiring, and extending this prohibtion all the way back the source, exceptions notwithstanding, is extremely problematical for hospitals, paricularly those with large remote central plants.

Your drawing actually was a common practice for small hospitals prior to CMP 13's interpretation of the separation requirements of Article 700 during the development of the 2002 NEC. The engineer's design is based on the life safety branch being considered part on an Article 700 emergency system. Article 700 does not apply to health care facilities.

RB

 

[Sonny Stas]

Thanks for your insight

Thanks for your insight

Thank you for your help to understand these sections. A concise explanation.