Set The Tension; Installation - Chamberlain WHISPER DRIVE Security+ HD900D Owner's Manual

ASSEMBLY STEP 5

Set the Tension

• Insert a screwdriver tip into one of the nut ring slots and brace
it firmly against the trolley.
• Place a 7/16" open end wrench on the square end. Rotate the
nut about 1/4 turn until the spring releases and snaps the nut
ring against the trolley.
This sets the spring to optimum belt tension.
You have now finished assembling your garage door opener.
Please read the following warnings before proceeding to the
installation section.

INSTALLATION

IMPORTANT INSTALLATION INSTRUCTIONS
To reduce the risk of SEVERE INJURY or DEATH:
1. READ AND FOLLOW ALL INSTALLATION WARNINGS AND
INSTRUCTIONS.
2. Install garage door opener ONLY on properly balanced and
lubricated garage door. An improperly balanced door may
NOT reverse when required and could result in SEVERE
INJURY or DEATH.
3. ALL repairs to cables, spring assemblies and other
hardware MUST be made by a trained door systems
technician BEFORE installing opener.
4. Disable ALL locks and remove ALL ropes connected to
garage door BEFORE installing opener to avoid
entanglement.
5. Install garage door opener 7 feet (2.1 m) or more above
floor.
6. Mount emergency release handle 6 feet (1.8 m) above floor.
7. NEVER connect garage door opener to power source until
instructed to do so.
Square
End
WARNING
WARNING
WARNING WARNING
8. NEVER wear watches, rings or loose clothing while
installing or servicing opener. They could be caught in
garage door or opener mechanisms.
9. Install wall-mounted garage door control:
• within sight of the garage door.
• out of reach of children at minimum height of 5 feet
(1.5 m).
• away from ALL moving parts of the door.
10. Place entrapment warning label on wall next to garage
door control.
11. Place manual release/safety reverse test label in plain view
on inside of garage door.
12. Upon completion of installation, test safety reversal
system. Door MUST reverse on contact with a 1-1/2"
(3.8 cm) high object (or a 2x4 laid flat) on the floor.
13. To avoid SERIOUS PERSONAL INJURY or DEATH from
electrocution, disconnect ALL electric and battery power
BEFORE performing ANY service or maintenance.
11
Nut Ring Slot
Square End
Trolley
Nut Ring
BEFORE
1"
(2.5 cm)
Nut Ring
AFTER RELEASE
1-1/4"
(3.18 cm)