Attach The Cable Tension Monitor (Required) - Chamberlain Liftmaster Security+ 3900PLD Owner's Manual

INSTALLATION STEP 4
Attach the Cable Tension Monitor
(Required)
This operator comes standard with the cable tension
monitor. It is supplied as a device to monitor the
cables for ANY slack that may occur and will reverse
the door when excessive slack is detected, eliminating
service calls.
The cable tension monitor MUST be connected and
properly installed before the door operator will move
in the down direction.
NOTE: The cable tension monitor is shipped for left side
installation. It is preferred that the cable tension monitor be
installed on the same side of the door as the operator.
If required, it can be mounted on the opposite side of door.
Remove the snap-ring holding the roller in place and
reassemble it on the opposite side of the cable tension
monitor.
1. Position the cable tension monitor as shown
(Figures 1 and 2). The cable tension monitor should be
located as close to the drum as possible.
NOTE: There must be no obstructions in the installation
area that prevent the cable tension monitor or the cable
itself from closing completely when slack is detected.
2. Make sure cable tension monitor is located over a wood
support member.
NOTE: If the cable tension monitor can not be mounted
into wood with the lag screws provided, it can be mounted
into 1/2" or greater drywall using the wall anchors (2) and
the #8 hex head screws (2) provided in the hardware bag.
3. Mark and drill 3/16" pilot holes for screws (pilot holes
are not required for anchors).
4. Attach the cable tension monitor to the wall using the
hardware provided. Make sure that the roller is on top of
the cable.
5. Run bell wire to operator. Use insulated staples to
secure wire in several places.
6. Connect bell wire to the green quick-connect terminals
(polarity is not important) (Figure 3).
NOTE: Cable must have tension through entire travel.
Make sure there is no slack in cable on opposite side of
door during normal operation. If this condition exists,
adjust cables as required.
HARDWARE SHOWN ACTUAL SIZE
#8 Hex Head Screw (2)
Screw #6 (2)
Staples
Wall Anchor (2)
9
Figure 1
Operator
Cable
1/8"-1/4"
(3 mm-6 mm)
With Door Closed
Preferred Orientation
Figure 2
Drum
3/4" Min.
(18 mm Min.)
Figure 3
Torsion Bar
Drum
2"-6"
(5 cm-
Cable
15 cm)
Tension
Monitor
Cable Tension
Monitor Roller
Wall
Cable
WHT/GRN
Cable Tension
WHT/GRN
Monitor
7/16" (11mm)
Strip wire 7/16" (11mm)
To insert or release wire,
push in tab with
screwdriver tip