LiftMaster 3255 3255 Manual - Page 4

Planning Identify the type and height of your garage door. Survey your garage area to see if any of the conditions below apply to your installation. Additional materials may be required. You may find it helpful to refer back to this page and the accompanying illustrations as you proceed with the installation of your opener. SECTIONAL DOOR INSTALLATION Horizontal and vertical reinforcement is needed for lightweight garage doors (fiberglass, steel, aluminum, door with glass panels, etc.). See page 19 for details. Header Wall FINISHED CEILING Support bracket & fastening hardware is required. See page 12. Slack in chain tension is normal when garage door is closed. Motor Unit Vertical Centerline of Garage Door Extension Spring OR Torsion Spring Wallmounted Door Control Access Door --- --- -- Safety Reversing Sensor Safety Reversing Sensor Gap between floor and bottom of door must not exceed 1/4" (6 mm). ONE-PIECE DOOR WITHOUT TRACK Header Wall Slack in chain tension is normal when garage door is closed. FINISHED CEILING Support bracket & fastening hardware is required. See page 12. Motor Unit Wallmounted Door Control Access Door ONE-PIECE DOOR WITH TRACK Slack in chain tension is normal when garage door is closed. Access Door Safety Reversing Sensor Gap between floor and bottom of Safety door must not exceed 1/4" (6 mm). Reversing Sensor 4 Safety Reversing Sensor Safety Gap between floor Reversing Sensor and bottom of door must not exceed 1/4" (6 mm).