Moving to Maine as a master HVAC technician: every state's rule

Maine has no master HVAC, HVAC contractor, mechanical contractor or refrigeration license at the state or municipal level, and no general contractor license, so a business may install and service air conditioning, ductwork, ventilation and refrigeration without any state credential. The highest person-held credential in the heating trades is the Maine Fuel Board's Master Oil Burner and/or Solid Fuel Technician license ($200 plus a $21 background check, exam required, after four years licensed with at least two as a journeyman), which is the license that lets a technician work unsupervised on oil and solid-fuel burning equipment and supervise apprentices; propane and natural gas work needs the separate Propane and Natural Gas Technician license, which has no master tier. Under a 2013 memorandum of understanding between the Fuel Board and the Electricians' Examining Board, master and journeyman oil burner technicians may also wire mini-split heat pumps of 36,000 BTU or less in one- and two-family dwellings and existing multi-family dwellings with electric heat; larger units and other occupancies require a licensed electrician, and refrigerant handling requires federal EPA Section 608 certification. A master HVAC licensee arriving from another state gains nothing from that license in Maine: no Maine agency recognizes it, no reciprocity exists for any Fuel Board license, and the Fuel Board's rules only credit documented out-of-state employment toward the master oil burner qualifications before the applicant sits the Maine exam. A statutory licensure-by-endorsement route (32 M.R.S. s. 18142-A and 10 M.R.S. s. 8003-H) applies to Fuel Board licenses in principle, but the board has not published an endorsement procedure or a list of equivalent states.