Chamberlain 1145-1/3HP - Manual (Page 12)

INSTALLATION STEP 3
Position the Opener
Follow instructions which apply to your door
type as illustrated.
TO PREVENT DAMAGE TO LIGHT WEIGHT
DOORS AND/OR DOORS WITH WINDOWS, DO
NOT REST THE OPENER ON THE DOOR.
INSTALLATION-SECTIONAL DOOR & 1-PIECE DOOR WITH TRACK
NOTE: A 2 x4 is convenient for setting an ideal door
to T-rail distance. It is not necessary where
headroom is insufficient.
PROCEDURE: Raise the opener onto a stepladder. Open
garage door. Place a 2x4 on the top section of door near
centerline as shown. Rest T-rail on 2x4 as shown.
INSTALLATION - 1-PIECE DOOR WITHOUT TRACK
PROCEDURE: Measure the distance from floor to top of
door (in fully open position and parallel to the floor). Using
a stepladder as a support, raise opener to the same
distance from the floor (it will have a slight angle as
shown).
The top of the door should be level with the top of
opener. For maximum efficiency, do not position opener
more than 2 inches above this point.
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