The cost of labor, material, and expenses incurred in the maintenance of a steam plant. Includes furnaces; boilers; coal, ash-handling, and coal-preparation equipment; steam and feed water piping; and boiler apparatus and accessories used in the production of steam, mercury, or other vapor to be used primarily for generating electricity. The point at which an electric steam plant is distinguished from an electric plant is defined as follows:

1. Inlet flange of throttle valve on prime mover.

2. Flange of all steam extraction lines on prime mover.

3. Hot well pump outlet on condensate lines.

4. Inlet flange of all turbine-room auxiliaries.

5. Connection to line side of motor starter for all boiler-plant equipment.