Completed protection plan on 9 furnaces. Checked heat exchangers with camera, and tested operation of heat cycle. All 9 furnaces kicked on started well, will need to return with filters next trip, highly recommend changing all out. Some dated back to 2018. Filter sizes collected with furnace models and serials. Electrical checked out on furnaces. Made some notes of certain inducer or blower motors but nothing that isn’t within normal operation or needs immediate attention. Estimate for dampers presented today.