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GS300Mc – Gas Detection Controller – 3 Channel

The GS300Mc – Gas Detection Controller is for various explosive and toxic gases. A wall or panel mounted with colour changing display. Compatible with the complete Duomo gas sensor range. The GS300M is a 3 Zone detector with a LCD Display.

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Quantity 1 - 4 5 - 9 10 - 19 20+
Price £438.94 £416.99 £395.05 £373.10



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The GS300Mc – Gas Detection Controller utilises a colour-changing display to immediately indicate the panel status, making it easy to notice. Users can take advantage of the override feature to have full control over outputs during sensor testing.

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The detector offers three-channel protection and operates on a 230VAC power supply. It accepts a 4-20mA signal sensor input and can be easily mounted on a wall or panel. Users can conveniently view information on the digital display, which features a colour change function for enhanced visibility. The device also includes emergency stop connections and a timed sensor test facility.

With the GS300Mc – Gas Detection Controller, users have the option to enable the positive safety feature for added security. It is capable of detecting toxic gases within the range of 0-300ppm, explosive gases within the range of 0-20%LEL, and oxygen levels within the range of 0-25%. It provides three alarm stages, including two pre-alarms and a main alarm.

During setup, users can easily configure the GS300Mc Gas Detector to meet their specific needs. They can choose the number of sensors to be connected (from 1 to 3), specify the type of gas to be sensed (explosive or toxic), decide whether to activate the positive safety option, and select the main alarm relay action (latching or auto-reset). The device also offers the option to enable or disable oxygen detection.

To ensure ease of use and reduce the risk of wiring errors, the GS300Mc Gas Detector features two LED indicators that display battery status and sensor wiring faults. It is additionally equipped with two plug-in terminal blocks, one for mains supply and alarm circuit wiring, and the other for sensor connections.

IP Rating

This gas detector has an IP44 protective rating, making it resistant to dust and water ingress. It is CE certified and approved to meet the standards of EN 61010-1, EN 50270, EN 50271, EN 45544-3, EN 60079-29-1, and EN 50104.


Users can feel confident in their purchase as the GS300Mc Gas Detector comes with a 3-year guarantee.

GS300Mc – Gas Detection Controller setup options

  • Number of sensors from 1 to 3
  • Type of gas to be sensed (explosive or toxic)
  • Positive Safety Option (on or off)
  • Main alarm relay action (latching or auto-reset)
  • Oxygen Detection (on or off)

Two LED’s show either battery or a sensor wiring faults. Finally, there are two plug in terminal blocks. One for mains supply and alarm circuit wiring. The second for sensor connections. This reduces the chance of incorrect site wiring.


Product Details

  • Three channel protection
  • 230VAC supply
  • 4-20mA signal sensor input
  • Wall or panel mounted
  • Digital Display with Colour change feature
  • Emergency Stop connections
  • Timed sensor test facility
  • Positive safety option
  • Detection of Toxic 0-300ppm / Explosive Gas(es) 0-20%LEL / Oxygen 0-25%
  • 3 alarm stages - 1st & 2nd pre-alarm and main alarm
  • IP44 protective rating
  • CE certified and approved to EN 61010-1, EN 50270, EN 50271, EN 45544-3, EN 60079-29-1, EN 50104
  • 3 year guarantee


Onsite Diagnostics

If you require onsite diagnostics or technical assistance with any of our products please contact us

  • This field is for validation purposes and should be left unchanged.


We recommend Duomo Gas Detection products are serviced at least annually to ensure efficacy and extend sensor life. Our qualified team of engineers are available Nationwide.



  • GS300Mc Datasheet

    1.79 MB | pdf



No LEDs are illuminated on the GS300MC controller.

Check that the electrical supply is reaching the device and that the plug in terminal rail is pushed into place.

One or all of the sensor fault LEDs are illuminated

Check that the plug is inserted correctly. Check that the sensor wiring is correctly terminated at both the detector and the sensor.

Check that 12V DC is present at the sensor. The green LED on the sensor should be illuminated.

By pressing the TEST button on the detector fascia it is possible to check the efficiency of the device and if the sensors have been connected correctly.

The connected sensor fault continues to alarm

Check the sensor wiring. If the red overload LED is illuminated then a short circuit or overload has occurred on the sensor or connecting cable.

The detector is subject to repeated alarms

Ensure that there is not an occasional gas leak. This may be due to a valve or joint which leaks under pressure.

The detector is in main alarm condition and the main gas valve is not closing

Check that the connections are correct and that power is supplied to the valve i.e. The valve is not stuck in the open position. The function of the alarm relays both the Pre-Alarm and the Main Alarm can be checked by pressing the TEST button on the detector fascia. Check that the main alarm action is configured for a latching alarm.
(Switch 2 on 5th DIP switch – See Configuring the GS300Mc in Datasheet)

There is no supply to the solenoid valve

The Main Alarm relay is a volt free contact, therefore you must connect the live supply to the common of the main alarm relay contacts terminal 10. A supply will then come from terminal 12 to the solenoid valve.

The sensor is connected but no LED is lit on the GS300Mc controller

Check that the DIP switch is set to the ON position for that sensor (Switch 1 on one of the first three DIP switches – See Configuring the GS300Mc in Datasheet)


Support & Service

If you require technical assistance or an annual service on this product please contact us and we will be happy to help. Our qualified team of engineers are available Nationwide.

Duomo (UK) Ltd

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