Honeywell FS20X Flame Detector

Based on the foundation of the highly successful and reliable SS4 Flame Detector, the FS20X Flame Detector represents a quantum leap in integrating Infrared and Ultraviolet sensing technologies. The FS20X is a Multi-Spectrum and UV/Dual IR/VIS Flame Detector with a proven UV solar-blind sensor. The FS20X exhibits faster false-alarm free response to fires over a wider temperature range and with a much longer detection range compared to conventional UV/IR detectors.

Conventional and older technology UV/IR detectors, using narrow band 4.3 micron IR sensors, will not respond to smoky fires or if the detector lens is contaminated with oil and other substances since both UV and 4.3 micron signals are attenuated, obscured or absorbed by thick smoke or detector lens contaminants. Also, these old technology UV/IR detectors will not alarm to any fire if they are installed behind ordinary window glass.

Dual microprocessors provide a high level of fail-safe operation combined with fast and reliable performance. The Master Microprocessor performs high-speed digital sampling and signal processing calculations; while the slave microprocessor handles various sensor data, performs communications, self-diagnostics and provides interface versatility; and additional memory for storing Event Log and FirePic™ data.

The FS20X Flame Detector has a detection range in excess of 200 feet (very high sensitivity setting) for the detection of a one square-foot Heptane reference fire and has a cone of vision greater in volumetric coverage than most UV/IR detectors. This means fewer detectors can be used as compared to other manufacturers’ detectors.

Honeywell FS20X-Flame-Detector

Multi-Spectrum UV/Dual IR/VIS Fire and Flame Detector

The FS20 detector using advanced patented algorithms for signal processing and fire and flame analysis is designed to alarm to all types of fires in all industrial environmental conditions. If the detector’s UV signal is degraded due to heavy smoke or a contaminated lens, the FS20X’s patented WideBand IR™, Near Band IR and Visible sensors will still alarm to fire, albeit at a reduced sensitivity and slower response time.

Key Features of the Honeywell FS20X UV/IR Flame Detector

  • Patented WideBand IR Infrared combined with Ultraviolet
  • Detection range greater than 200 feet to 1 sq. ft. heptane fire
  • Patented Electronic Frequency Analysis
  • Visible Sensor for optimum false alarm rejection
  • Selectable detection sensitivities
  • Solar blind 90° full 100% cone-of-vision
  • Dual Microprocessors for reliable performance
  • Real-time clock for accurate time dating of events
  • FirePic — Up to 6 pre-fire event data storage
  • Event log — Up to 200 events with date and time stamp
  • Built-in RS-485 ModBus Communication
  • Built-in non-isolated 4-20 mA analog output (sink or source)
  • Alarm, Fault and Fire Verification relays.
  • Automatic Optical Path and Electronic Self-Test
  • Widest operating temperature range
  • Patented Electronics Module for components protection with plug-in terminations for easy field installation
  • Two ¾” NPT OR 25mm conduit entries
  • Low power consumption
  • High RFI and EMI immunity

Honeywell FS20X UV/IR Flame Detector Specifications

Field of View

90° Full 100% Cone of vision, ± 45° from on-axis


Very High, High, Medium and Low – Switch Selectable

Response Time

3-5 Seconds to 1 sq. ft. n-Heptane fire at 100 ft.

3-10 Seconds to 1 sq. ft. n-Heptane fire at 200 ft.

Spectral Sensitivity

Ultraviolet: 185 – 260 nanometers

Visible: 400 – 700 nanometers

Near Band IR: 0.7 – 1.1 microns

Wide Band IR: 1.1 – 3.5 microns

Operating Voltage

24 VDC nominal (18-32 VDC) – Regulated

Power Consumption

Operating: 83 mA @ 24 VDC nomina


133 mA @ 24 VDC nominal


155 mA – additional

Note: Heater will turn on at 0ºF (-17ºC)

Output Relays

Fire Alarm: SPDT (NO / NC) – De-Energized/Energized, Latching/Non-Latching

Fault: SPST (NO) – Normally Energized, Latching/Non-Latching

Auxiliary: SPDT (NO / NC) – De-Energized/Energized, Latching/Non-Latching

Contacts rating: 1 amp @ 24 VDC

Analog Output

0 – 20 mA stepped – Source or Sink User Selectable

Loop Resistance

50 – 400 OHMS


One of the following – User Selectable:

  • RS-485, Modbus Protocol
  • RS-485, FireBus II
  • RS-485 Special (optional)
  • HART, Optional plug-in module
Visual Indications

Blue LED: Power

Red LED: Alarm

Yellow LED: Fault

Temperature Range

Operating: -40 to +185ºF (-40 to +85ºC)

Storage: -67 to +230ºF (-55 to +110ºC)

Humidity Range

5 to 98% relative humidity, non-condensing


Meets or exceeds MilSpec 810C Method 514.2, Curve AW12


14 AWG (2.5mm2) to 22 AWG (0.326mm2); Shielded Cable Recommended

Conduit Entries

Standard: Two ¾” NPT or two M25

Enclosure Materials

Copper-Free Powder Coated Aluminum or 316 Stainless Steel

Enclosure Type

NEMA 4 & 4X, IP66


FM: Class I, Div. 1 & 2, Groups B, C, & D; Class II, Div. 1 & 2, Groups E, F, & G; Class III

ATEX: II 2 G D; Ex d IIC T4 (Ta: -40 to +110ºC), T5 (Ta: -40 to +75ºC), T6 (Ta: -40 to +60ºC)

CE: Complies with EN6100-6-4 & EN50130-4

Shipping Weight

Aluminum: 3.6 lbs (1.6 kg)

Stainless Steel: 7 lbs (3.2 kg)


Swivel Bracket Assembly – Optional


Three years from the date of shipping