The Honeywell 851 Series comprises intelligent plug-in addressable thermal heat detectors engineered for property protection across commercial, institutional, and industrial fire alarm installations.

• Make / Brand: Honeywell
• Series / Models: 851 Series (FST-851 Fixed Temperature, FST-851R Rate-of-Rise, FST-851H High Temperature)
• Operating Voltage: 15 to 32 VDC peak (two-wire SLC loop)
• Standby Current: 300 µA at 24 VDC maximum average (communication every 5 seconds with LED enabled)
• Alarm Current: 6.5 mA at 24 VDC (LED active)
• Thermal Ratings: FST-851 fixed setpoint at 135°F (57°C); FST-851R 15°F (8.3°C)/min rate-of-rise with 135°F (57°C) fixed setpoint; FST-851H fixed high-temperature setpoint at 190°F (88°C)
• Operating Temperature Range: -20°C to 38°C (-4°F to 100°F) for FST-851 / FST-851R; -20°C to 66°C (-4°F to 150°F) for FST-851H
• Operating Humidity: 10% to 93% RH (non-condensing)
• Addressing: Direct rotary decimal addressing (01 to 99 on CLIP systems, 01 to 159 on FlashScan systems)
• Visual Indicators: Dual LEDs providing 360-degree status and alarm visibility
• System Compatibility: Honeywell Notifier intelligent FACPs (NFS-320, NFS2-640, NFS-640, NFS-3030, NFS2-3030)
• Mounting Bases (Sold Separately): Compatible with B210LP(A) flanged, B501(A) flangeless, B200S(A) sounder, B224RB(A) relay, and B224BI(A) isolator bases
• Housing Material: Off-white Bayblend plastic meeting UL 94-5V flammability standard
• Approvals & Standards: UL Listed (S747), FM Approved, CSFM, MEA, BSMI, CCCF, USCG, Lloyd's Register; NFPA 72 compliant