Less than flammable liquid filled transformer over 600/1000 Volts

[Ctrusdall]

I’m trying to interpret the code and what is the appropriate wall construction of two 4160V 2500 KVA transformers installed in a building. They are FR3 liquid filled (less than flammable). They have oil containment. The room has automatic fire sprinklers.

My question is; is it acceptable for the wall construction to be stud and wallboard? Or should it be a 1 hour rated reinforced concrete/CMU wall?

 

[don_resqcapt19]

it appears that would comply with 450.23(A)(2) with just general construction for the walls.