LiftMaster LM21XP Fire Door Release with Alarm Delay

Programmable Fire Door Release for Rolling and Sliding Systems 

The LiftMaster LM21XP is a UL-listed fire-rated door release device designed for use with rolling steel, sliding, and center-parting doors. Engineered to respond to fire alarms or fusible link activation, it enables controlled release of fire doors in emergencies while supporting compliance with NFPA 72 and 80. The unit features a normally energized fail-safe design, programmable delay-on-alarm, and compatibility with up to four smoke detectors. Integrated LED diagnostics, relay outputs, and audible alerts provide enhanced system feedback and reliability for commercial and industrial applications.

Key Features

• Fail-safe design with mechanical reset
• Selectable alarm delay of 10, 20, 30, or 60 seconds via DIP switches
• Supports up to 4 smoke detectors (2-wire or 4-wire)
• Integrated alarm and trouble relays for fire panel signaling
• Close-door detection logic reduces nuisance releases
• Diagnostic LEDs for power, alarm, trouble, and grounding status
• Audible trouble buzzer for rapid diagnostics
• UL 864 and UL 1481 compliant when powered by listed supply with battery backup
• Compatible with manual or motorized doors using fusible link systems

Technical Specifications

• Model: LM21XP
• Voltage: 24VDC regulated (UL 1481 listed power supply required)
• Current Draw: 100mA standby, 150mA in alarm
• Alarm Delay Options: 10, 20, 30, or 60 seconds
• Load Rating: Releases loads up to 40 lbs
• Relay Outputs: Form C alarm and trouble relays
• Dimensions: 9.7" H × 7.5" W × 5" D
• Environment: Indoor dry locations only
• Compliance: UL 864, UL 1481, NFPA 72 & 80

Compatible Accessories

These accessories enhance system performance and ensure full NFPA compliance:

Smoke Detectors:

• LM2W-B – 12/24VDC 2-Wire Photo
• LM2WT-B – 12/24VDC 2-Wire Photo with Thermal
• LM4W-B – 12/24VDC 4-Wire Photo
• LM4WT-B – 12/24VDC 4-Wire Photo with Thermal & Relay
• LM1424 – 24VDC Ionization
• LM1412 – 12VDC Ionization
• LM8100 Series – 120V detectors (Photo, Ion, with Thermal options)

Heat Detectors:

• LMTH135 – 135°F Fixed Temperature
• LMTH194 – 194°F Fixed Temperature

Supervision & Reset Parts:

• LMEOLR1224 – End-of-Line Relay (12/24VDC)
• LMEOLR120 – End-of-Line Relay (120VAC)
• LMEOLRES-10 – 10k Ohm End-of-Line Resistor
• LM56A – Door Position Proximity Switch
• LMRK – Mechanical Reset Knob
• LMELH – End Link Assembly
• LM2AG3AMP – 3A Fuse

Conclusion

The LiftMaster LM21XP offers reliable emergency door release functionality with advanced diagnostics and programmable settings. Whether integrated into motorized fire-rated doors or manual drop systems, it ensures code-compliant operation for high-risk facilities seeking dependable, monitored fire protection.