LiftMaster Model MJ
LiftMaster Model MJ Commercial Door Operator is a medium-duty Logic jackshaft operator with a compact design. It is ideal for industrial sectional doors with high or vertical lift, as well as small rolling doors and grilles, delivering reliable performance in space-saving installations.
BY:
Performance
Control & Wiring
- Programmable C2 or B2 wiring options to meet commercial control requirements
- B2 wiring requires an installed Monitored Entrapment Protection Device
- Solid-state medium-duty operator/motor control circuit board
Motor & Power
- Powerful 1/2 HP single-phase motor with high starting torque
- Internal automatic reset thermal overload protection
- Motor removable without affecting limit switch settings
Safety & Protection
- Floor-level disconnect allows emergency manual operation
- Adjustable friction clutch helps protect the door and operator if an obstruction is encountered
- Integrated 90-second maximum run timer
Drive System & Components
- Drive reduction system with heavy-duty 4L V-belt (first stage)
- Second and third stages use #48 chain
- Heavy-duty oil-filled bushings
- Heavy-duty solenoid-actuated brake is standard
Installation & Construction
- Easily field convertible for right- or left-hand mounting
- NEMA Type 1 electrical box
- Heavy-duty 11-gauge steel frame
- Durable powder-coated finish
- Reduction sprockets drilled and pinned to shafts
Warranty
- Backed by a 2-year warranty
Safety
- Built-in 3-channel, 315 MHz radio receiver
- Accepts up to 20 LiftMaster® Security+ remote controls
- Supports an unlimited number of DIP switch remote controls
- 3-button remotes can be programmed for Open / Close / Stop operation
- Integrated Timer-to-Close (TTC) automatically closes the door after it reaches the fully open position
- Timer-to-Close is programmable from 5 to 60 seconds in 5-second increments
- Complies with UL 325 standards for monitored entrapment protection
Technical Information
- Control circuit: 24V NEC Class 2 control circuit
Important Notes
- The MJ operator is not recommended for large or high rolling doors without a chain hoist modification (see Model MH)
- For steel-insulated doors, a 24-gauge back panel is assumed
Recommended Capacities
- Maximum recommended duty cycle: 12 cycles per hour
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What types of doors are compatible with the LiftMaster Model MJ?
The LiftMaster Model MJ is designed for industrial sectional doors with high or vertical lift, as well as small rolling doors and grilles. Its compact jackshaft design makes it ideal for space-saving commercial installations.
What motor power does the LiftMaster Model MJ use?
It features a powerful ½ HP single-phase motor with high starting torque, providing reliable medium-duty performance for commercial applications.
Does the Model MJ include safety and entrapment protection features?
Yes. The operator complies with UL 325 standards and supports monitored entrapment protection devices. It also includes an adjustable friction clutch and a 90-second maximum run timer for enhanced safety.
Can the LiftMaster Model MJ be operated manually during emergencies?
Yes. A floor-level disconnect allows the operator to be disengaged for manual door operation during power outages or emergency situations.
What control and wiring options are available with the Model MJ?
The operator supports programmable C2 or B2 wiring configurations. B2 wiring requires a monitored entrapment protection device and is commonly used for commercial safety compliance.
Does the LiftMaster Model MJ support remote controls and timers?
Yes. It has a built-in 3-channel radio receiver and supports up to 20 LiftMaster Security+® remote controls, unlimited DIP switch remotes, and a programmable Timer-to-Close from 5 to 60 seconds.
What is the duty cycle and warranty for the LiftMaster Model MJ?
The maximum recommended duty cycle is 12 cycles per hour, and the operator is backed by a 2-year manufacturer warranty.