The Model MJ is a medium-duty door opener, as manufactured by The Chamberlain Group, Inc. and is for use on vertical or high lift sectional doors or small rolling doors and grilles. It is rated for 12 cycles per hour during peak periods. Up to 50 cycles/day.


  • Voltage/phase : 115 V/1 ph
  • Horse power : ½ h.p.
  • Minimum sideroom required: 18″
  • Solid-state Medium-Duty Logic circuit board.
  • High-starting torque operator with instant reverse.
  • Capacitor start on single-phase.
  • Motor is removable without affecting limit switch settings.
  • Heavy-duty solenoid brake
  • First-stage heavy-duty 4L V-Belt; second and third stages #48 chain.
  • Heavy-duty oil-filled bushings.
  • Adjustable friction clutch helps protect against damage to the door and opener should the door meet an obstruction.
  • Provides emergency manual operation using an electrically interlocked floor level disconnect
  • NEMA 1 type electrical box, heavy-duty 11-gauge steel frame with baked-on powdercoat finish, all reduction sprockets drilled and pinned to shafts.
  • Integrated Timer-to-Close (TTC) allows programming from 5 to 60 seconds in 5-second increments. Allows for timed automatic door closure after the door reaches the full open position (Requires monitored safety devices, with CPS-U, CPS-UN4, or CPS-EI).
  • Integrated 90-second maximum run timer
  • UL and CSA listed.
  • 2-year warranty.

    Your security, our priority!

    CPS® Commercial Protector System®

    The presence of primary entrapment protection is standard CPS-U for all modes.  Primary entrapment protection devices are monitored continuously to insure safe operation of the door and limit door opener functionality should an obstruction be detected or in the event of device failure. Optional LiftMaster Monitored Entrapment Protection devices,  CPS-UN4, CPS-RPEN4 and CPS-EI, are designed to work in conjunction with LiftMaster commercial door openers to provide enhanced door safety and a broad range of modes and features to end users. Either monitored photo-sensor or monitored 4-wire sensing edge (in conjunction with the CPS-EI Edge Interface) protection may be selected, but one must be detected by the LiftMaster Logic 4.0 or Medium-Duty Logic circuit board in order to unlock full functionality.



    Garage doors and garage door openers can be dangerous if not installed and verifed by a professionnal and not used properly . Chidlren must be supervised by an adult when they are inside or in proximity of the garage.

    Included with the LiftMaster MJ opener

    • LiftMaster MJ opener
    • Chain Tensioner
    • 3-Button Control Station
    • Receiver included (transmitter in option)
    • Hardware bag for installation (includes all necessary hardware for installation)