Air-cooled/dry transformers encased in a room that is sprinklered are rated at __.

Air-cooled or dry transformers that are located in a sprinklered room are typically rated for a one-hour fire-resistance rating. This rating indicates that the transformers can withstand fire exposure for at least one hour without reaching a temperature that could compromise the structural integrity or the safety of the equipment.

The one-hour rating is essential for ensuring that, in the event of a fire, the transformer does not contribute to the spread of fire and that it can be safely maintained or operated after a fire incident. This rating is a standardized measure defined in codes and standards related to electrical installations, providing guidelines for fire safety in environments where electrical equipment is installed.

The other time frames offered (two-hour, three-hour, and four-hour) do not apply to air-cooled or dry transformers situated in sprinklered areas, as the requirements for those ratings pertain to different types of equipment, occupancy separations, or specific fire-resistive construction scenarios.