ATU Maintenance Entity Training Homeowners! Learn to become a maintenance entity for your own ATU system. Contractors! Become a maintenance entity for certain systems used in Florida.*Systems eligible for training are limited. The classes do not count for CEU credit. Homeowner Registration Contractor Registration Example of permit Example of Site Plan SYSTEMS NOT PARTICIPATING: AquaKlear (601-936-7711), CajunAire (225-665-2949), Norweco (419-668-4471), and Orenco (541-459-4449)