F found it!
It is the Emermency Power Systems in NFPA-110 section 7.2.2.
The EPSS equipment shall not be installed in the same room with the normal service equipment where the service equipment is rated over 115V and is equal or greater than 1000A.
I call this room the Life Safety Room. Pretty much all of the equipment being fed from the generator that if for life safety.
thank you
