Fire rating of Electrical Room

[Scott Novotny]

If you have a dry type transformer Class 7420, 750KVA, 13800V/480/277V does the room have to be have a 3 hour rating. I need clarification from the standpoint of Article 110.31A if that just means a vault and not a room.
There is not a vault definition in Article 100.

 

[celtic]

Have you checked 450.21(B) and (C)?