Chamberlain 248754 - Manual (Page 4)

4
Safety Reversing Sensor
Header Wall
Access Door
— — — — — — — —
Safety
Reversing
Sensor
Gap between floor
and bottom of door
must not exceed 1/4" (6 mm).
Extension Spring
Horizontal and vertical reinforcement
is needed for lightweight garage doors
(fiberglass, steel, aluminum, door with
glass panels, etc.). See page 24 for details.
Support bracket &
fastening hardware
is required.
See page 16.
FINISHED CEILING
Motor unit
Wall-
mounted
Door
Control
OR
Torsion Spring
Vertical
Centerline
of Garage Door
SECTIONAL DOOR INSTALLATION
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.
Depending on your requirements, there are several
installation steps which may call for materials or
hardware not included in the carton.
• Installation Step 1 – Look at the wall or ceiling above
the garage door. The header bracket must be securely
fastened to structural supports.
• Installation Step 5 – Do you have a finished ceiling in
your garage? If so, a support bracket and additional
fastening hardware may be required.
• Installation Step 11 – Depending upon garage
construction, extension brackets or wood blocks may
be needed to install sensors.
• Installation Step 11 – Alternate floor mounting of the
safety reversing sensor will require hardware not
provided.
CLOSED POSITION
Header
Wall
Garage
Door
Header
Bracket
Trolley
Straight
Door
Arm
Emergency Release
Rope & Handle
Door
Bracket
Curved
Door
Arm
Garage
Door
Spring
Belt
Trolley
Stop Bolt
• Do you have an access door in addition to the garage
door? If not, Model 7702CB Emergency Key Release
is required. See Accessories page.
• Look at the garage door where it meets the floor. Any
gap between the floor and the bottom of the door must
not exceed 1/4" (6 mm). Otherwise, the safety reversal
system may not work properly. See Adjustment Step 3.
Floor or door should be repaired.
SECTIONAL DOOR INSTALLATIONS
• Do you have a steel, aluminum, fiberglass or glass
panel door? If so, horizontal and vertical reinforce ment
is required (Installation Step 12).
• The opener should be installed above the center of the
door. If there is a torsion spring or center bearing plate
in the way of the header bracket, it may be installed
within 4 feet (1.2 m) to the left or right of the door
center. See Installation Steps 1 and 12.
• If your door is more than 7 feet (2.1 m) high, see rail
extension kits listed on Accessories page.