LiftMaster LM21XP Fire Door Release Device

Liftmaster LM21XP Release Device 

The LiftMaster LM21XP is an extended performance release device designed for use with rolling steel, sliding, and fire-rated doors. This UL-listed unit responds to fire alarm signals or heat-triggered events to safely release doors in emergencies. Powered by a 24V DC regulated supply, it supports up to four smoke detectors and features programmable delay settings, audible trouble alerts, and diagnostic LEDs. Suitable for manual or motorized doors equipped with fusible links, it’s ideal for high-risk environments requiring NFPA-compliant fire protection.

Key Features

• Normally energized fail-safe design with mechanical reset
• 10-, 20-, 30-, or 60-second programmable delay on alarm
• Supports up to 4 smoke detectors (2-wire or 4-wire configurations)
• Integrated alarm and trouble relay outputs for fire panel signaling
• Close-door detection logic prevents false drops
• Diagnostic LEDs for power, alarm, trouble, and grounding faults
• Audible trouble buzzer and end-of-line supervision
• For use with manual or motorized doors with fusible link systems
• UL 864 and UL 1481 compliant (requires listed power supply with battery backup)

Technical Specifications

• Model: LM21XP
• Voltage: 24V DC regulated (from UL 1481 listed supply with battery backup)
• Alarm Delay Settings: 10, 20, 30, or 60 seconds (DIP switch adjustable)
• Current Draw: Standby: 100mA | Alarm: 150mA
• Load Rating: Supports and releases up to 40 lbs.
• Operating Temperature: Indoor dry location only
• Dimensions: 9.7" H × 7.5" W × 5" D

Conclusion

The LiftMaster LM21XP offers dependable and programmable emergency door release functionality, meeting stringent fire code requirements. Its fail-safe design, flexible alarm integration, and diagnostic capabilities make it a trusted choice for commercial and industrial fire door systems.