Chamberlain GT Owner's Manual page 4

CAUTION: AT LEAST TWO PERSONS AND A STRONG, SAFE WORKING PLATFORM ARE REQUIRED
FOR THE INSTALLATION OF OPERATOR.
CAUTION
TO AVOID DAMAGE TO DOOR AND OPERATOR,
MAKE ALL DOOR LOCKS INOPERATIVE. SECURE
LOCK(S) IN "OPEN" POSITION.
IF THE DOOR LOCK NEEDS TO REMAIN
FUNCTIONAL, INSTALL AN INTERLOCK SWITCH.
DO NOT RUN THE OPERATOR BEFORE MAKING
LIMIT SWITCH ADJUSTMENTS.
FOR METAL BUILDINGS ONLY: A strong mounting
surface for the operator front header bracket is
needed. On the wall above the center stile, weld or
bolt a 2"x2"x1/4" piece of angle iron or another
suitable, heavy-duty material as shown in Figure 2.
6. Draw a vertical line on header (or reinforcement
material) above center stile of door.
7. Raise the door to its high arc point. Use a
carpenter's level to locate high arc point on wall
above door center stile as shown in Figure 3. Make
a horizontal line, intersecting the vertical centerline
mark.
2"
FIGURE 4
INSTALL OPERATOR
Header
Wall
Header
Bracket
High Arc
Point of Door
FIGURE 2
Building
Support
FIGURE 3
8. Close the door and refer to Figure 4. Position
operator chassis on the floor with the bottom edge
of header bracket 2" above horizontal mark and
centered on vertical line. Mark mounting holes.
FOR METAL BUILDINGS: Drill 3/8" holes for
fastening bolts. FOR CONCRETE BUILDINGS: Drill
3/8" holes for anchor bolts, following manufacturer's
instructions.
NOTE: Be sure header bracket is level before
tightening the bolts.
4
Vertical
Centerline
2"x 2"x 1/4"
Angle Iron
Center
Stile
Carpenter's Header
Level
Wall
High Arc
Point