Chamberlain 3840 Manuale Utente

4

Horizontal and vertical reinforcement
is needed for lightweight garage doors
(fiberglass, steel, aluminum, door with
glass panels, etc.). See page 19 for details.

Support bracket & 
fastening hardware
is required.
See page 15.

 — — —        — — —        — —

Header Wall

Safety 
Reversing Sensor

Safety Reversing Sensor

Gap between floor and bottom 
of door must not exceed 1/4" (6 mm). 

FINISHED CEILING

Torsion
 Spring

Access Door

Motor Unit

Wall-
mounted
Door 
Control

Rail

Extension
 Spring

OR 

Vertical
Centerline
of Garage
Door

Safety Reversing 
Sensor

Support bracket
& fastening
hardware is required.
See page 19.

Safety Reversing 
Sensor

Access
Door

Gap between floor
and bottom of door 
must not exceed 1/4" (6 mm).

Wall-mounted
Door Control

Header Wall

Motor
Unit

Rail

FINISHED CEILING

Safety 
Reversing Sensor

Safety 
Reversing Sensor

Access
Door

Gap between floor
and bottom of door 
must not exceed 1/4" (6 mm).

Header Wall

15.

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.