D.C. Mun. Regs. tit. 17, § 403 – Classes of Licenses

403.1 The following classes of licenses shall be offered:

(a) Class 1 - Steam Engineer;
(b) Class 2 - Steam Engineer;
(c) Class 3 - Steam and Hot Water Heating Boiler Engineer;
(d) Class 4 - Steam Engineer;
(e) Class 5a - Steam Engineer;
(f) Class 5b - Miniature Boiler Engineer;
(g) Class 6 - Steam and Hot Water Heating Boiler Engineer;
(h) Class 7 - Portable and Construction Equipment Operator;
(i) Class 8a - Operating Engineer - Refrigeration; and
(j) Class 8b - Operating Engineer - Stationary Internal Combustion.

403.2 The total horsepower rating of all boilers and machinery installed and connected in a building or plant, except in the case of Class 3 Engineers as provided in §404.4, shall be the basis of determining the grade of license required. Machinery specifically exempted in §400.1, fractional horsepower motors, and electric motors used as prime movers of machinery not covered by this chapter shall not be included.

SOURCE: §§3.1, 3.2, 3.3, and 3.12 of Commissioners' Order No. 301, 945, 5M DCRR §§3.1, 3.2, 3.3, and 3.12.