Transformer Vault Fire Rating

[jbt260]

450.42 states that walls need to have a minimum fire resistance of 3 hours (or 1 hour with fire suppression). However, in 450.43, only INTERIOR doors are required to have a minimum fire resistance of 3 hours (or 1 hour with fire suppression). Exterior doors are not required to have a fire rating unless AHJ requires it.

My question is: Would an exterior wall of a transformer vault be required to have a minimum fire resistance of 3 hours?? 450.42 does not differentiate between interior and exterior walls. But it wouldn't make much since for an exterior wall to be rated for 3 hours if the exterior door is not rated at all.

Looking forward to everyone's insight!

Thanks,

 

[david luchini]

My question is: Would an exterior wall of a transformer vault be required to have a minimum fire resistance of 3 hours?? 450.42 does not differentiate between interior and exterior walls. But it wouldn't make much since for an exterior wall to be rated for 3 hours if the exterior door is not rated at all.

450.43(A) doesn't really say that an exterior door isn't required to have a fire rating. It says that the AHJ can require that the exterior door be rated for 3 hours.

The initial rating of the door would be based on your building or fire codes. For instance, the International Building Code would require a 1.5 hour rated door in an exterior 3 hour rated wall. Per 450.43(A), the AHJ can require a 3 hour door instead of the 1.5 hour door.

On the flip side, 450.45(E) only requires a 1.5 hour minimum rating on fire dampers at the ventilation openings. But the IBC requires a 3 hour minimum damper on a penetration of a 3 hour or greater rated assembly.

So yes, I'd say the code language requires the exterior wall of the vault to be 3 hour rated.