Chamberlain 3280 1/2 HP Garage Door Opener User Manual


 
6
ASSEMBLY STEP 1
Attach the Rail to the Motor Unit
To avoid installation difficulties, do not run the
garage door opener until instructed to do so.
Remove the two washered bolts mounted in top of
motor unit.
Align rail and styrofoam over sprocket. Cut tape
from rail, belt and styrofoam.
REMOVE STYROFOAM.
Insert washered bolts through the rail into the
motor unit. Tighten bolts securely.
Use only these bolts! Use of any other bolts
will cause serious damage to door opener.
Position belt over the motor unit sprocket.
To avoid SERIOUS damage to opener, ONLY use
bolts/fasteners mounted in top of motor unit.
WARNING
CAUTION
WARNING
WARNING
ASSEMBLY STEP 2
Set the Belt Tension
By hand, thread the spring trolley nut on the
threaded shaft until it is finger tight against the
trolley (Figure 1). Do not use any tools.
Insert a screwdriver tip into one of the nut ring
slots and brace it firmly against the trolley
(Figure 2).
Place a 7/16" open end wrench on the square
end. Rotate about 1/4 turn until the spring releases
and snaps the nut ring against the trolley
(Figure 3).
This extends the spring for optimum belt tension.
Trolley
Threaded
Shaft
Spring/Trolley Nut
Nut
Ring
Trolley
Threaded
Shaft
Nut Ring
Slots
Square
End
Nut Ring Trolley
Nut Ring
Trolley
1" (2.5 cm) 1-1/4" (3.18 cm)
BEFORE AFTER RELEASE
Figure 1
Figure 2
Figure 3
USE ONLY THIS
TYPE AND SIZE
BOLT
Washered Bolt
5/16"-18x1/2"
Rail
Hole
Sprocket
Rail
Hole