In a boiler plant where there are two 250 horsepower boilers connected to the same common header, what engineer's license would be required to be in charge of the plant?

In a boiler plant with two 250 horsepower boilers connected to a common header, the appropriate license required to be in charge is a First Class Engineer's license. This is primarily because the combined capacity of the boilers reaches 500 horsepower, which exceeds the limits typically governed by lower-level licenses.

A First Class Engineer's license signifies that the individual not only has comprehensive knowledge of boiler operations but also possesses the necessary skills to manage larger boiler systems safely and effectively. This includes understanding complex operations, troubleshooting potential issues, and ensuring compliance with safety regulations and standards.

In contrast, other levels of licenses, such as a Chief Engineer or Second Class Engineer, may not encompass the specific requirements and competencies needed for the management of higher-capacity boilers, whereas a Special Engineer's license typically pertains to more limited or specialized roles that may not provide the same breadth of responsibility or authority over large boiler systems. Thus, for effective management of a plant with such a capacity, the First Class Engineer's license is the appropriate credential.