For air-cooled/dry transformers not located in a sprinklered room, what is their fire rating?

The fire rating for air-cooled or dry transformers not located in a sprinklered room is indeed three hours. This rating is based on the fire safety requirements set forth in various relevant codes and standards, such as the National Electrical Code (NEC) and the National Fire Protection Association (NFPA) guidelines.

Typically, air-cooled or dry-type transformers are classified in such a way that they can withstand exposure to fire for a period of three hours without allowing flames or heat to penetrate to adjacent areas or fluids. This is particularly important in installations where there may be combustible materials nearby, ensuring an adequate margin of safety and reducing the risk of fire spread in case of transformer failure or overheating.

This three-hour fire rating requirement offers enough time for firefighting efforts to be initiated in case of an incident, thereby improving the overall safety of the facility and its occupants. This standard reflects the industry's commitment to fire prevention and safety management in environments where energy equipment is present.