Section R. 339.5113 - License classificationRule 113.
(1) A licensee who is seeking an additional mechanical license classification shall submit to the department an application provided by the department along with the nonrefundable application fee.(2) A boiler licensee who is seeking to upgrade his or her license to a higher classification shall maintain his or her current license in good standing for at least 1 year and take the prescribed examination. A boiler licensee may only upgrade his or her license 1 classification at a time.Mich. Admin. Code R. 339.5113