Lift-master 90 827 User Manual

VARIABLE SPEED

MODIFICATION ADDENDUM

MODELS: GH & GT (1/2 - 1HP, 1PH. ONLY)

Variable Speed DC Motor

DC Controller

Safety equipment MUST be used with operators

employing this modification.

WARNING

WARNING

APPLICATION

This operator is equipped with a variable speed
modification. The AC motor and control circuit in a door
operator has been replaced with a DC variable speed drive
control and permanent magnet DC motor. May be provided
for either 115 or 230VAC single phase power. Allows
adjustment of the door speed over a wide range, up to 4
ft/sec on some applications. Acceleration adjustment gives
“ramp up”, or soft starts to allow operation of very heavy
doors. Dynamic brake and current limit circuits replace
mechanical brake and clutch respectively, minimizing the
number of moving parts that may wear out. Suitable for
continuous duty and high cycling applications.

Refer to the wiring diagram included with this addendum in
lieu of diagrams included with owner's manual.

VARIABLE SPEED WITH DECELERATION (OPTIONAL)

PART NUMBER: 90-827

When present, provides a adjustable “ramp down” or soft
stop at the full open and full close position.

NOTE: This modification will usually affect the horsepower
selection for a given model. Higher speeds require higher
horsepower for the same door. If you have concerns,
consult your representative for specific horsepower rating
information on your application.

VARIABLE SPEED MODIFICATION

SCHEMATIC DIAGRAM

1211

2

SEE NOTE

NOTE: When equipped with a Timer to Close the yellow wire will connect from terminal R2 to terminal 1
and the radio will only open and set the timer.