Chamberlain PD300DM Manuale Utente

5

Access
Door

Safety
Reversing Sensor

Safety
Reversing
Sensor

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

Door
Bracket

Straight
Door
Arm

Garage
Door

Header

Bracket

Curved
Door Arm

Chain

Emergency
Release
Rope &
Handle

Cable

Rail

Trolley Stop Bolt

Header
Wall

•  

Generally, a one-piece door does not require 
reinforcement. If your door is lightweight, refer to 
the information relating to sectional doors in 
Installation Step 11.

•  

Depending on your door’s construction, you may 
need additional mounting hardware for the door 
bracket (Step 11).

Safety Reversing Sensor

Access
Door

FINISHED CEILING

Support bracket
& fastening
hardware is required.
See page 16.

Safety Reversing 
Sensor

Header Wall

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

Wall-mounted
Door Control

Rail

Motor Unit

Slack in chain tension 
is normal when garage 
door is closed.

Header

Bracket

Trolley

Straight
Door
Arm

Emergency
Release
Rope & Handle

Door Bracket

Curved
Door
Arm

Header
Wall

Cable

Rail

Garage Door

Trolley Stop Bolt

Without a properly working safety reversal system, 
persons (particularly small children) could be 
SERIOUSLY INJURED or KILLED by a closing garage 
door.
•  The gap between the bottom of the garage door and 

the floor MUST NOT exceed 1/4" (6 mm). Otherwise, 
the safety reversal system may not work properly.

•  The floor or the garage door MUST be repaired to 

eliminate the gap.