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GC803 Catalytic Combustible Gas Detector

Product Literature

  • Combustible Gas Detector
  • Catalytic Sensor
  • Built-in 4-20mA transmitter
  • Explosion-proof
  • Aluminum or Stainless Steel housing

Keywords:  Combustible Gas Detector, Flammable Gas Detector, Hydrocarbon Gas Detector, Methane Detector, Butane Detector, Propane Detector, Hydrogen Detector, Catalytic Gas Detector, Catalytic Sensor

Features and Benefits

  • Catalytic sensor with excellent long term zero and sensitivity stability and high poison resistance
  • Built-in 4-20 mA output for connection to external equipment
  • User programmable LOW and HIGH alarm settings
  • Voltage-free dry contact relays for local control
  • Explosion-proof approved electronics housing for Class I, Div I, Groups A, B, C, D
  • Sensor in stainless steel explosion-proof housing, ATEX or ATEX and CSA listed
  • Available up to IP66 rating
  • 24 volt DC nominal operating voltage
  • Shipped fully assembled and pre-calibrated
  • Suitable for connection to any 4-20 mA input device, including SST NOVA-5000 modules, PLC’s, SCADA or distributed control systems
  • Use this model in applications where no gas concentration display and relay contacts are required (please see our GC804 if you require relay contacts within the detector/sensor)
  • Suitable for on-shore, off-shore, petrochemical, refineries, turbine engines, natural gas storage tanks, natural gas pipelines, tunnels and mining, cogeneration, refrigeration, and other industrial facilities requiring combustible gas sensors
  • 5 Year Warranty
  • Made in the USA

Product Summary

GC803 Catalytic Combustible Gas Detector is an economical industrial combustible gas sensor. Save money by installing this model in locations where the gas concentration display and relay contacts are not required. Provides 4-20 mA output signal.  Compatible with the NOVA-5000 control panel as well as other control panels.  Available up to IP66 rating. Catalytic sensor responds to all combustible gases such as:  methane, propane, butane, ethane, pentane, hexane, hydrogen, heptane, octane, ammonia, gasoline (petrol), acetone; ethanol, toluene, iso propyl alcohol, cyclohexane, methyl ethyl ketone, hydrocarbon vapors and ethyl acetate. 5 Year Warranty.  Made in the U.S.A.


The SST Model GC803 Combustible Gas Sensor is used to determine the concentration of gas accumulated in a protected area and transmit this information to a central control point. The SST sensor use the “catalytic” method of gas detection. Located inside a stainless steel flameproof housing, the sensing element is exposed to the detected gas through a sintered stainless steel flame arrestor. The actual detector consists of a matched pair of elements, each consisting of a fine platinum wire embedded in a bead of alumina material. Flammable gases in low concentrations will not burn by themselves, but when in contact with a suitable catalyst, it is possible to burn (or oxidize) any concentration of gas. One of the element pairs in the SST sensor is treated with such a catalyst, while the other element is protected with a similar, non-catalytic material. The platinum wires within the elements are heated by passing a suitable current through them. When the gas is oxidized on the surface of the catalyst, additional heat is released, which causes a temperature rise on the catalytic surface. This change in temperature is measured and converted to determine the amount of gas present.

The SST Combustible Gas Sensor has been designated with a special “poison-resistant” sensing material, and provides accurate measurements in atmospheres where traces of silicone or other poisoning agents may be present. Readings are unaffected by humidity or carbon dioxide. The concentration of combustible gas is measured in terms of the Lower Explosive Limit (LEL).

The Model GC803 Combustible Gas Sensor includes an electronic “transmitter”, which is installed in the associated explosion proof junction box. This transmitter converts the signal from the catalytic element to a standard 4-20 mA signal. This signal may be connected to a suitable SST NOVA-5000 Gas Detection/VulcanGuard Module, or to any other device with a standard 4-20 mA input. Connections to the combustible gas are normally made with 3 conductor shielded cable. The Model GC803 is suitable for the most demanding applications. A large body mass ensures excellent vibration characteristics when used in large machinery applications. Corrosion resistant materials permit uses in most environments, including offshore oil platforms.


Architect's and Engineer's Specifications

Combustible gas sensing capability shall be provided by poison-resistant catalytic gas sensors, contained in stainless steel explosion proof housings. The sensor shall be installed with a transmitter card which converts the measured gas concentration in percent LEL to the industry standard 4-20 mA signal. The sensor shall be suitable for offshore use, and the manufacturer’s data shall so state. Three conductors shall he required between the sensor/ transmitter and the associated control device. Safety Systems Technology Model GC803 Combustible Gas Sensor, complete with part number 860 Transmitter Card and part number 850 Junction Box, or approved equivalent, shall he supplied.

Technical Specifications and Ordering Information

Technical Specifications

Sensor Type: Catalytic bead (pellistor) with excellent long term zero and sensitivity stability
Poison Resistance: Highly resistant
Gases Detected: Most combustible gases and vapors
Sensor Life: Typical 5+ years
Measuring Ranges: 0-100% LEL
Accuracy: +/- 1% LEL (CH4)
Zero Drift: < +/- 1/2 mV/Month
Linearity: Effectively linear to 100% LEL (to within 5%)
Response Time: T90 < 30 seconds
Modes: Normal operation, set-points, calibration, and set-up
Warranty: 5 Years
Country of Origin: USA
Approvals: Explosion-proof approved housing
Class I, Division I, Groups A, B, C, D; Class I Zone I, AEx d IIC; Type 4X
ATEX:  II 2G Ex d IIC Gb
Electrical Specifications
Operating Temperature: Electronics -40°F to 185°F (-40°C to 80°C)
Sensor -40°F to 266°F (-40°C to 130°C)
Operating Humidity: 0-100% RH, non-condensing
Ingress Protection: IP40 to IP66
Mechanical Specifications
Dimensions: 6.4 x 5.7 x 4.3 inches
(163 x 145 x 109 mm)
Controller Housing: Aluminum or Stainless Steel
Input Power: 24 VDC nominal, 16 to 32 VDC
92 mA standby, 120 mA alarm
Relay Contact Ratings: 6 amps @ 28 VDC or 300 VAC resistive
1/8 HP @ 120/240VAC
Analog Signal: 0-20 mA current sink (600 Ohms or less)
0 mA  Malfunction
4 mA  Zero Reading
4-20 mA  0-100% LEL
>20 mA  Over-range
Field Connections: 4-20 mA output and power – three-wire shielded cable or three conductors in metal conduit
All connections:  22 AWG (.35 mm²) to 12 AWG (4.0 mm²)
Wireless Communication: Available with optional wireless transmitter with text, e-mail notification features

Ordering Information

803-4-AL Model GC803 Combustible Gas Sensor; Aluminum
803-4-SS Model GC803 Combustible Gas Sensor; Stainless Steel
800-4 Replacement catalytic sensor
851-1-4 Rain shield
851-5-4 Water spray shield
852-1-4 Dust cover
854-1-4 Duct mount
859-1-4 Gas collection cone
857-01 Calibration kit (test gas sold separately)
10121 Spare calibration/test key