LiftMaster LM21AFCB Advanced Fire Control Release Device
The LiftMaster Fire Control LM21AFCB Release Device is a UL/ULC-listed normally energized, fail-safe device incorporating state-of-the-art electronic control circuitry.
This release device is designed for manual doors or motorized doors incorporating a reversing electric safety edge to create an automated door closing system, and in conjunction with a temperature fuse link system.
The high-performance control panel responds to emergency conditions generated from an automatic initiating device. Upon activation, the device will then automatically close a motorized door or mechanically release a door in the absence of motorized operation.

Features
- UL 864 Revision 9 compliant.
- 3 count obstruction cycling.
- Selectable 10, 20, 30, or 60-second delay on alarm.
- Test key switch – Floor level testing.
- Motor voltage sensing.
- Form C relay output.
- Lower limit detection.
- Safety timer.
- Battery support for release device logic, smoke detectors, and standard annunciator.
- Trouble diagnostic capabilities (does not support operator).
- 2-wire or 4-wire smoke detector wiring.
- 120Vac operating voltage.
Also known as
- LiftMaster CN21-AFCB
- LiftMaster OH21-AFC
Product Literature
Find answers to our most frequently asked questions below. Got more questions? Reach out to our friendly customer service team, they will be more than happy to assist you.

