Gas Detection & Safety Instruments · Fixed Gas Detectors
A point gas detector in an explosion-proof cast aluminium housing for continuous monitoring of combustible gas, oxygen, hydrogen sulphide and carbon monoxide, supplied as a stand-alone unit or with a controller over wired or wireless links.
GQ-KL800-L4 ·
A fixed gas detector answers a different question from the instruments usually compared with it. A portable detector asks whether the atmosphere is safe for a person who is about to enter it. A fixed detector asks whether anything has changed since the last time someone looked, at a point where a gas would collect if it escaped, and it is expected to still be answering that question months later without attention.
That difference drives the whole specification. Because the instrument sits in the atmosphere it monitors continuously rather than briefly, where it is placed and how it survives become part of the engineering rather than accessories to it.
The detector is one device. Around it the material describes three arrangements, and the choice between them is a wiring decision rather than a measurement decision. In the stand-alone form the detector is supplied alone and plugged in, with the audible and visual alarm raised at the point and no wiring between units. In the wired form the detector and a controller are linked by four-core cable, which the customer provides, and one controller can serve several detectors. In the wireless form the two are linked without any wiring at all, with the controller run from 220 V and the detector supplied with a power adaptor that matches automatically once the detector is energised.
The controller is what turns readings into actions. It takes up to 99 detectors, annunciates alarms audibly and visibly, provides two relay outputs and holds 999 alarm events through a power failure. Its optional RS-485 interface speaks standard Modbus/RTU, which is the route to a PLC, a DCS, a GDS or a fire panel, and its relay contacts are what start a fan, close a valve or switch an alarm lamp.
The combustible channel burns a small amount of the gas on a heated catalytic element and measures the heat released, which reads directly as a fraction of the lower explosive limit. It needs oxygen to work and is permanently poisoned by silicones, leaded compounds and some solvents. The oxygen, hydrogen sulphide and carbon monoxide channels use electrochemical cells, each reacting its gas at an electrode and producing a current proportional to concentration; a cell is consumed by the gas it measures, so its life follows exposure rather than the calendar.
The material gives the recovery time, ≤10 s, rather than the response time. The two are not the same figure: one describes how quickly the reading falls back after the gas has gone, which is what makes the detector usable again after an excursion, and the other describes how quickly it rises when the gas arrives. On a fixed installation both matter, and only one is stated.
Where the detector is mounted decides whether it works at all, and it is decided before any instrument is chosen. A gas lighter than air rises and collects at the highest point of the space, so a detector for it belongs high. A gas heavier than air settles, which means it will be found first in pits, sumps, trenches and at floor level. A detector placed at breathing height for a heavy gas reads air, reports it as safe, passes its calibration and is in the wrong place - a failure that is harder to spot than an instrument that is plainly not working.
The housing is built for that duty. It is flameproof die-cast aluminium with a sealing ring at every joint and an IP66 rating, because the detector is installed inside the classified area rather than protected from it. Its own certification therefore forms part of the installation: the flameproof construction, the gas group it is valid for and the temperature class it is allowed to reach all have to match the area. The two temperature windows in the material - -40 to 70 °C for the combustible channel and -20 to 50 °C for the toxic channels - follow from the sensor technologies rather than from the housing, and they mean a mixed installation has to be checked channel by channel against the place it is going into.
The controller is where a detection point becomes part of a plant. Two relay outputs are available as standard, and what they operate decides how many are needed: an alarm that only has to be noticed is different from a contact that has to start ventilation or close a valve while the event is still happening. The material lists fans, solenoid valves, alarm lamps and a cloud platform among the possible interlock and monitoring options, with the optional host software offering record query, curve analysis, device monitoring and a large-screen display.
Two practical points belong with that. The first is that the lower limit of the controller’s operating temperature is quoted as 20 °C in the material, which its own note suggests may be a misreading of 0 °C, so the cabinet it lives in should be checked against the conservative reading until that is confirmed. The second is that the controller’s menu is in Chinese, which the material states plainly; whether an English menu is available is a question for the enquiry rather than an assumption.
The most important gap on this page is that the material does not state the measuring range, the resolution or the alarm setpoints of the detector. For a gas detector those are the first figures normally compared, and they are listed as information required rather than filled in from a similar instrument. The controller’s own T90 < 30 s figure is its transmission and annunciation time, not the detector’s response time, and should not be read as one.
Three further points are worth stating. The material gives two sets of dimensions for the detector - 186 × 142 × 69 mm in the parameter table and 239 × 178 × 90 mm in the outline drawing - and keeps both; since the drawing is what a mounting bracket is made from, the discrepancy should be settled before installation. The humidity limits differ between the two devices, at 0-95 %RH for the detector and ≤93 %RH for the controller, so a system sharing one room should be assessed against the stricter figure. And the wireless form’s power arrangement is described in the material as containing a text misalignment, so the relationship between the detector’s battery and the adaptor it comes with has to be confirmed rather than inferred.
The items that fix the answer are the gas or gases at the point, where the point is and at what height, the classification of the area including the gas group and temperature class, the number of points and how far apart they are, whether a cable route exists or the link has to be wireless, what each relay output has to operate and whether that action is automatic, and which certificates the installation has to be signed off against. A plan with the points marked and a gas list is enough to issue a covering quotation, which can then be refined as the siting is agreed. Quantity, destination port and required delivery date complete the enquiry.
Every value below is taken from source documentation. Where a parameter is not stated in the available material it is marked as information required rather than estimated.
| Model | GQ-KL800-L4Standard |
|---|---|
| Gases monitored | Combustible gas, oxygen, hydrogen sulphide and carbon monoxide; other gases available to orderStandard |
| Default channel arrangement | Channel 1 combustible gas in %LEL; channel 2 oxygen in %VOL; channel 3 hydrogen sulphide in ppm; channel 4 carbon monoxide in ppmStandard |
| Detection principle | Catalytic combustion and electrochemicalStandard |
| Measurement range | Not stated in the materialInformation required |
| Resolution and alarm setpoints | Not stated in the materialInformation required |
| Response time | Not stated in the material; the figure the material gives is the recovery timeInformation required |
| Recovery time | ≤10 sStandard |
| Explosion protection | Ex db IIC T6 Gb, flameproof constructionStandard |
| Ingress protection | IP66Standard |
| Power consumption | 1.2 WStandard |
| Operating mode | 24 hour continuous operationStandard |
| Zero drift | ≤±1 % of full scale per yearStandard |
| Operating environment, combustible gas | -40 to 70 °CStandard |
| Operating environment, toxic gas | -20 to 50 °CStandard |
| Operating humidity | 0-95 %RH, non-condensingStandard |
| Dimensions | 186 × 142 × 69 mm in the parameter table; the outline drawing on the same page shows 239 × 178 × 90 mm, and the material keeps both without choosingInformation required |
| Net weight | Not stated in the materialInformation required |
| Storage temperature | Not stated in the materialInformation required |
| Mounting | Wall, pipe or flow-through, depending on the environment being monitoredStandard |
| Housing | Explosion-proof die-cast aluminium, with sealing rings at every joint against water and dustStandard |
|---|---|
| Sensor arrangement | Plug-in measuring cell module, so the cell can be serviced or replaced without dismantling the instrumentStandard |
| Display | LED display showing the live concentrationStandard |
| Indication | Power and alarm indicator lampsStandard |
| Parameter adjustment | Infrared remote control, so alarm parameters can be changed without opening the housing and without the static spark risk that opening it under power would bringStandard |
| Stand-alone | Detector supplied alone and plugged into a local supply. No wiring between units; audible and visual alarm at the point; the four gases can be combined freelyStandard |
|---|---|
| Wired | Detector and controller linked by four-core cable, which the customer provides. Alarms are annunciated at both the point and the controller, and one controller can serve several detectorsStandard |
| Wireless | Detector and controller linked without wiring; the controller is supplied from 220 V and the detector is supplied with a power adaptor and matches automatically once energisedStandard |
| Capacity | 1 to 99 detectors, with the channel count following the number of points connectedStandard |
|---|---|
| Display and operation | LED display with a Chinese-language menuStandard |
| Response time | T90 < 30 sStandard |
| Alarm | Audible and visualStandard |
| Supply | AC 220 V ±15 %, 50 Hz ±1 %Standard |
| Environment | Stated as 20 to +55 °C and ≤93 %RH in the material, which also notes the lower figure may be a misreading of 0 °CInformation required |
| Alarm outputs | Two relay outputs; RS-485 bus interface optionalStandard |
| Communication | RS-485 bus interface, optional, standard Modbus/RTU protocol, for connection to a host control system for remote monitoringOptional |
| Standby battery | 30 VDC, 2000 mAh, optionalOptional |
| Alarm records | 999 alarm events, retained through a power failureStandard |
| Dimensions | 250 × 60 × 350 mmStandard |
| Model designation | Not stated in the materialInformation required |
| Ingress protection | Not stated in the materialInformation required |
| Relay contact rating | Not stated in the materialInformation required |
| Host system connection | PLC, DCS or GDS, and fire alarm panelsStandard |
|---|---|
| Interlock options | Fans, solenoid valves, alarm lamps, and monitoring by phone or tablet through a cloud platformOptional |
| Panel indications | Polled address, concentration, fault address, reset, and status indications for mains power, standby power, alarm, communication and interlockStandard |
| Host monitoring software | Optional, with record query, data monitoring, map monitoring, device monitoring, curve analysis, system configuration and large-screen display, showing connected devices, normal operation, alarm and fault counts, offline devices and an exception summaryOptional |
| Certificates | Not supplied in the materialInformation required |
| Model | Configuration | Key ranges | Availability |
|---|---|---|---|
| GQ-KL800-L4 | Fixed four-channel detector, flameproof die-cast aluminium housing, IP66, 1.2 W, 24 hour continuous duty, infrared remote parameter adjustment, plug-in measuring cell | Combustible gas, oxygen, hydrogen sulphide and carbon monoxide; -40 to 70 °C for the combustible channel and -20 to 50 °C for the toxic channels; zero drift ≤±1 % of full scale per year | The detector itself. The controller it reports to has no model designation in the material, and the measurement range and alarm setpoints of the detector are not stated there either |
Certifications are only published once a certificate copy can be produced, so this section is deliberately empty rather than populated with assumed approvals. Tell us which approvals your application requires and we will confirm what is available for this instrument.
The following are required for a complete specification but are not stated in the documentation supplied to us. They are listed rather than estimated:
The first decision is not the instrument but the point. A fixed detector watches one place continuously, so where that place is decides everything that follows - the gas it will see, the height it has to sit at, the classification of the area it sits in, and how it will be reached for calibration. The second decision is what happens when a limit is exceeded, because a relay that starts a fan or closes a valve changes the controller and the wiring rather than only adding an alarm. Both are answerable from a plan and a gas list, and without them a quotation can only be a covering one.
Because the material does not state it. It gives the gases, the detection principle, the recovery time, the drift figure, the temperature limits, the protection ratings and the power consumption, but not the measuring range, the resolution or the alarm setpoints of the detector. Those are the figures a buyer normally compares first, so they are listed as information required rather than filled in from a similar instrument. The controller's own response time is given as T90 < 30 s, which is the transmission and annunciation time rather than the detector's.
Both connect a detector to a controller that annunciates the alarm and provides relay outputs; the difference is the cable between them. The wired form uses four-core cable that the customer supplies and that has to be run and glanded by an electrician, and it can be arranged as one controller to several detectors. The wireless form removes that cable: the controller runs from 220 V, the detector is supplied with a power adaptor, and the two match automatically once the detector is energised. Which is right depends on the distance, the obstacles and whether a cable route is available - the wireless form is generally the simpler answer across a finished building, and the wired form where a route already exists.
The measuring cell is the consumable. The material describes it as a plug-in module, which means the cell can be changed without dismantling the instrument, and that matters because a detector whose cell cannot be reached becomes a gap in the coverage rather than a maintenance task. A catalytic element for the combustible channel is not consumed in normal use but is permanently poisoned by silicones, leaded compounds and some solvents, so it is the atmosphere rather than the calendar that shortens its life. The zero drift figure is given per year, which sets a calibration interval, and the infrared remote means the parameter check can be made without opening the housing under power.
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