Manual transfer switch

[anbm]

This question to the folk working on hospital facility and design (NEC 517 and NFPA-99 related rule):

Will manual transfer switch be allowed to serve emergency - equipment power branch system? Thanks!

 

[roger]

This question to the folk working on hospital facility and design (NEC 517 and NFPA-99 related rule):

Will manual transfer switch be allowed to serve emergency - equipment power branch system? Thanks!

Yes and no for the equipment Branch, see 517.34(A), (B), and (C)

No for the Emergency system, it must be automatic.

517.31 Emergency System
Those functions of patient care depending on lighting or appliances that are connected to the emergency system shall be divided into two mandatory branches: the life safety branch and the critical branch, described in 517.32 and 517.33.

The branches of the emergency system shall be installed and connected to the alternate power source so that all functions specified herein for the emergency system shall be automatically restored to operation within 10 seconds after interruption of the normal source. [NFPA 99:4.4.2.2.2.1, 4.4.3.1]

Roger

 

[anbm]

Thanks, Roger. I just re-read 517.34 section again.

 

[roger]

You're welcome.

Roger

 

[kingpb]

I wonder how they figured 10 secs was quick enough that someone wasn't going to die?

 

[roger]

I don't think it has anything to do with someone dying, there are other safeguards that can be used for that. I would say it is more of a standardized time limit for EM Power pick up, see 700.12.

Roger