Position The Opener - Chamberlain LiftMaster Professional Security+ 3850 Owner's Manual

INSTALLATION STEP 4

Position the Opener

Follow instructions which apply to your door type
as illustrated.
SECTIONAL DOOR OR ONE-PIECE DOOR WITH
TRACK
A 2x4 laid flat is convenient for setting an ideal
door-to-rail distance.
• Raise the opener onto a stepladder. You will need help
at this point if the ladder is not tall enough.
• Open the door all the way and place a 2x4 laid flat on
the top section beneath the rail.
• If the top section or panel hits the trolley when you
raise the door, pull down on the trolley release arm
to disconnect inner and outer sections. Slide the outer
trolley toward the motor unit. The trolley can remain
disconnected until Installation Step 12 is completed.
ENGAGED
ONE-PIECE DOOR WITHOUT TRACK
• With the door fully open and parallel to the floor,
measure the distance from the floor to the top of the
door.
• Using a stepladder as a support, raise the top of the
opener to this height.
• The top of the door should be level with the top of the
motor unit. Do not position the opener more than
4" (10 cm) above this point.
Trolley
Release Arm
RELEASED
WARNING
CAUTION
To prevent damage to garage door, rest garage door opener
rail on 2x4 placed on top section of door.
Rail
Door
Header
Bracket
Top of Door
11
2x4 is used to determine
the correct mounting height
from ceiling.
Top of Motor Unit
2x4 is used to determine
the correct mounting height
from ceiling.