What is Flame Sensor ?

Have you ever wondered how your home’s fire alarm and extinguishing system works? Well, it all revolves around a critical device – a flame sensor. It is among the topmost sensitive sensors to a standard light. Because of this, you will find it being in use in most flame alarms in residential and commercial establishments. So what does it involve, and how can you go about securing your home with this piece of a genius sensor?

Flame Sensor

It is a crucial sensor module for deployment in flame alarm systems in buildings. A flame sensor detects a flame within the wavelength of 760nm – 1100 nm from a specific light source. While effective as detection equipment, it can easily get damages when subjected to high temperatures. Because of this, always place it at a specific distance from the flame source.

A flame sensor’s typical flame detection distance is 100cm with a detection angle of 600. A flame sensor can have a digital or analog signal. It thus forms a crucial element in fire or flame fighting robots such as alarms (flame alarms).

A flame sensor comes as a special detector designed for sensing besides responding to flame or fire incidences. In most instances, the detection response to the flame depends on its fittings. For instance, it can include propane, natural gas line, alarm system, and a fire or flame suppression system. In addition, industrial applications like boiler systems provide authentication of whether it (boiler) works properly or not.

The response timeline of flame sensors proves more rapid and accurate than smoke/heat detectors due to its detection mechanism.


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How a Flame Sensor Works

The working principle of a flame sensor proves straightforward to anyone familiar with sensors. One has to develop it with an electronic circuit that uses a receiver such as electromagnetic radiation. Almost all of the flame sensors I know use an infrared flame flash approach, which allows the sensor to function without any coating of water vapor, dust, oil, or otherwise ice.

The Flame Sensor Module

A flame sensor has a configuration that entails four pins, especially when it is working with a microcontroller unit such as an Arduino. The pins encompass the following.

  • Pin1 comes as the VCC pin. It has a supply voltage of 3.3V to 5.3V
  • Pin2 come as a GND, which is the ground pin
  • Pin3 is the AOUT. It is the analog output pin commonly known as MCU.IO.
  • Pin4 comes as the DOUT. It is a digital output pin that we commonly call MCU.IO as well.

Types of Flame Sensors

Flame sensors are diverse and classified into IR single frequency, UV flame sensors, and UV/IR flame detectors.

IR Single Frequency FS

Infra-red single frequency flame sensors or detectors monitor a narrow radiation band of 4.5 microns. It is a predominant emission for hydrocarbon fires and a helpful band because the radiation from the sun gets absorbed by the atmosphere. Consequently, it makes the single-frequency sensors blind to solar.

Single-frequency infra-red detectors prove immune to optical contaminants. Besides this, it is also insensitive to welding, solar, x-ray, arcs, sparks, corona, and lightning. However, you cannot use this flame sensor for non-carbon fires. Additionally, ice or rain can inhibit the detector lens. Therefore, you will need to clean the lenses regularly.

UV/IR Flame Detector

A UV/IR flame sensor or detector combines infrared and ultraviolet flame detection technologies. It employs a solar-blind ultraviolet sensor with an infra0red sensor and filters matched to the anticipated type of fuel or fire.

The infra-red wavelength you select can determine the UV/IR flame detector’s response features. You will find this wavelength as 2.7 microns in most instances, especially for non-hydrocarbon flames or fires. However, for the hydrocarbon-based flames or fires, it is 4.5 microns.

What’s more? UV/IR flame sensors or detectors come with an unprecedented level of resilience to false alarms. It comes about because the IR and UV detection technologies share a few false alarm sources. However, diligence becomes crucial in handling the UV/IR sensors because of the countless factors that inhibit the response from the detector. For instance, airborne solvents, optical contamination, and ice or water on the optics of the detector can inhibit its proper function.


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UV Flame Sensors

It is a particular type of fire detector comprising a sensor tube that senses radiation emitted between 180nm to 250nm. The UV flame sensors have existed since the 1970s, and they can respond rapidly to fires owing to their detection mechanism. Its mechanism relates to light energy (photon number) received by the sensor or detector every second. On exceeding the set threshold, it immediately sounds the alarm.

Fires emit radiation in the region of 180nm – 250nm. However, there is absorption of the sun’s radiation into the atmosphere, and consequently, the flame sensor becomes blind to solar. UV detectors prove sensitive to many fire types, including metal (magnesium), hydrocarbon (gases, liquids, and gases), Sulphur, hydrazine, ammonia, and hydrogen.

However, UV flame sensors or detectors are primarily useful in gas turbine acoustic enclosures. The reason behind this entails UV detectors proving insensitive to the generated heat within the turbine. While useful for general-purpose applications or devices, you can face many false alarms with lightning, sparks, x-rays, welding, and arcs.

Triple IR Flame Sensor/Detector

The triple IR flame detector came about after advances in microprocessor speeds in the 1990s—the advances allowed for more complex spectral band analysis and quick calculations. Triple IR detectors possess three sensors, with each sensor sensitive to a specific IR wavelength. For instance, one sensor will prove sensitive to the intense wavelength produced by a standard hydrocarbon fire (4.5 microns). The other two sensors will monitor adjoining spectral bands for a false alarm. However, it is never the case with other radiation sources such as sunlight, lamps, and heaters. Electronic circuitry within the detector translates whatever information that gets gathered into analyzable data. The analysis encompasses flame flickers, the energy signal threshold comparison, and the mathematical correlations and ratios between diverse signals.

Triple IR sensors come immune to false alarms besides having long detection distances to specific fire types. However, the flipside with triple IR detectors entails the wide variations in performance from one brand to the next. It is especially true regarding response times and detection distances. Thus, you should consult a gas and fire design engineer to review your detector’s performance to their application carefully.

Aspects to Consider before Picking a Flame Sensor Type

It is always crucial to select a detector type for your application. However, it is prudent to understand the installation and application process as the designer before you do. Because of this, consider the following.

Area Classification: it is essential to interrogate where one will install the units. Is it a hazardous area? What are the required approvals for such an installation?

Fire Risk: you need to assess the potential things that can burn. Ask yourself what the escalation potential is and what size of the fire needs to get detected.

Operating Conditions; it is always crucial to maximizing the flame detector’s uptime owing to its status as the primary safety gadget. Comprehending the minimum and maximum operating temperatures thus becomes essential.

Undesired Alarm Sources consider whether there exists something that might cause a false alarm (alarm sounding without any presence of a hazard). One of the most apparent and unwanted sources entails ground or elevated flare. But it is also prudent to understand that various stimuli can adversely influence diverse detection or sensing technologies.

Function Testing and Maintenance: every flame detector type needs routine testing and periodic maintenance, especially in highly contaminated atmospheres. Therefore, if possible, try and ensure access becomes available without any need for scaffolding, though this may not always prove possible.


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Attributes and Specifications of a Flame Sensor

  • It has high photosensitivity, making it ideal for detecting flames and fire outbreaks in your building.
  • A flame sensor has a rapid response time making it practical for fire alarm systems and extinguishing fires.
  • It is simple to operate than other sensor types
  • The flame sensor or detector has a detection angle of 600, which unprecedented for sensors
  • It proves responsive to the range of flames. As such, it can sense and deal with varying intensities of fires
  • You can adjust the accuracy of the flame sensor
  • It has an operating voltage of 3.3V to 5V
  • It has a printed circuit board size measuring 3cm by 1.6cm, which you can comfortably get from RayMing PCB and Assembly.
  • The flame sensor has a digital switch and analog voltage o/ps
  • It also contains a power indicator beside the digital switch o/p switch
  • Whenever the flame’s intensity is lighter but within 0.8m, then the activation of the flame test happens. However, when the flame’s intensity is higher, an enhancement of the detection distance happens.

Applications of Flame Sensors

  • Due to the diverse types and their corresponding attributes, a flame sensor can find application in different sectors. But some of the most notable application areas include the following.
  • It is predominantly useful in the detection of fires
  • You will also find flame sensors incorporated in firefighting robots to sense and fight any fire outbreaks in buildings
  • Fire detection is another area where a flame detector finds application
  • It is essential in industrial heating, especially boiler systems
  • Additionally, it is useful in domestic heating systems and industrial gas turbines
  • Flame sensors also work in drying systems and gas-powered cooking equipment

Goodman Flame Sensor

For anyone conversant with furnaces and HVAC systems, you understand the importance of a flame sensor. Therefore, if you have a Goodman furnace, you must install a flame sensor to protect it against the inappropriate burning of fuel. Additionally, it has to work properly for the proper functioning of your Goodman furnace. All this means encompass periodic maintenance and cleaning of the flame sensor. But before going into the maintenance and cleaning, what does a Goodman flame sensor entail?

Furnace Flame Sensor: What it Is

It is a flame sensor positioned on your Goodman furnace. It is a critical component that ensures the complete burning of the gas and does not accumulate in the system’s vent. You will always find a furnace flame sensor as a thin metallic rod located on the furnace’s burner assembly. The furnace ignitor relies on a recognition system. It recognizes the flame burning in the furnace. However, it turns off the furnace in its absence so that no gas gets out into the vent system without undergoing complete combustion.

However, frequent use of the Goodman furnace implies that the sensor will get dirty at some point, which will hinder its ability to detect a flame. It, therefore, becomes prudent to clean the sensor to restore its proper functionality.

The Location of the Flame Sensor on Your Goodman Furnace: How to Get to It

  • The Goodman’s furnace has a flame sensor mounted next to the burner assembly. If you want to clean or access it for repair or maintenance, you should follow the guidelines below to access it.
  • Shut off the power source to safeguard your safety before removing the panels
  • It is equally prudent to shut off the gas supply to avoid endangering yourself.
  • Slide up the lower or upper compartment access panel to detach it from the furnace
  • Search for the flame detector or sensor near the burn enclave
  • You need to pull the detector carefully from out of its housing or enclave. However, it is essential to remember that you may sometimes need to disconnect the cables from the sensor first before removing the sensor from its enclave.


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How to Spot a Bad Goodman Flame Sensor

You may often clean your Goodman flame sensor but still find it malfunctioning. To avoid all this hustle, always watch for these signs to identify a faulty flame sensor.

  • When the Goodman furnace lights yet it shuts down
  • If the flame sensor’s metallic rod has a fissure or crack
  • When there is corrosion of the flame sensor

If you identify a problem with your sensor, it is always advisable to contact a licensed HVAC contractor to service your Goodman furnace and replace the flame sensor. After all, everyone wants an expanded lifespan for their Goodman furnace, and I bet you do too.

RHEEM Flame Sensor

A flame sensor on the RHEEM gas furnace gets the alternative name as the RHEEM sensor. The design of RHEEM gas aims at durability. It contains simple-to-service panels, exciting designs, features, and diagnostic systems. However, among the fundamental elements of the RHEEM furnace entails its flame sensor. Therefore, it is prudent to understand how it works and where it is located within the furnace to ensure easy maintenance for proper functionality.

There is mounting of a thin metallic rod outside the burner assembly through porcelain insulation. The jutted end sticks out into the flame. To clean or repair your RHEEM flame sensor, you must know its location within the furnace and how to reach it. Some of the critical steps you need to follow encompass the following.

  • Extricate the furnace cover by removing the knobs or screws that hold the cover. You will find the RHEEM furnace flame detector immediately after removing the furnace’s access cover.
  • You then need to check the burner assembly to see the flame sensor, which ordinarily gets mounted on the burner assembly’s exterior. In most cases, it is attached using a wire. Further, the sensor sticks up from its enclave and into the burning flame.

Cleaning your RHEEM Flame Sensor

You can always clean your RHEEM flame sensor yourself, provided you adhere to the following steps.

Firstly, ensure that you have all the tools like the ¼” hex wrench, a little light grit sandpaper, emery cloth, and steel wool. Further, also get some dry and clean paper towels.

You should shut off the electrical power that gets into your RHEEM furnace. It is possible to switch it off by toggling the on-switch or through its circuit breaker without a control system.

The next step entails locating the RHEEM flame sensor. Mostly, you will get it at the furnace’s back right in the path that holds the burner.

Remove all the hex screws that hold the flame sensors in place before sliding the flame sensor out. It usually gets enclaved within the assembly or burner bracket.

You should detach the wires connecting the sensor to the furnace, especially on some RHEEM furnace models. Such a detachment provides adequate room to clean the sensor and ensure its proper function.

Make a visual check of the flame sensor and ensure it has no corrosion, carbon, or soot buildup. While necessary, it also proves a simple step that you can execute using simple tools readily available at home. It is essential to rub the probe using an emery cloth to remove the carbon deposits.

Also, watch out for any visible cracks or damage to the insulation (porcelain). If you notice any, then it becomes wise to replace the sensor.

Finally, you need to check whether the problems go away or persist. If it works properly, then you can relax. However, if it fails to work by depicting the same symptoms, it is wise to call for an HVAC specialist to check it out.


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Carrier Flame Sensors

It is a type of flame sensor you typically find in Carrier furnaces. The name of the furnace gives it its name – Carrier furnace. You will find this flame sensor on your Carrier’s burner assembly as a thin metal rod. It comes bent and sits in front of your pilot flame within the furnace. Like the RHEEM and Goodman flame sensors, you must ensure its in an excellent state to function correctly. You, therefore, should service it periodically besides cleaning it to avoid problems with ignition detection on your Carrier gas furnace.

Carrier flame sensors come in different brands and series because continuous enhancements happen to the technology like most electronic and electrical parts. However, it becomes prudent to ensure that your Carrier furnace is compatible with the carrier flame sensor you wish to replace it with, especially if you have a problematic carrier flame sensor. Always check the specifications vis-à-vis your furnace specs to ensure compatibility. It is also advisable to consult an HVAC specialist whenever you don’t feel so sure.

The Process of Accessing and Replacing your Carrier Flame Sensors

If you notice a hitch with your Carrier furnace, it is always prudent to check the flame sensor. However, to reach and visually inspect it, you need to follow the steps below.

Turn off the Carrier gas furnace’s electrical power source, either at the electrical box or at the Carrier furnace.

Ensure that you have closed the gas valve to safeguard your health and limit any chances of accidental exposure

You then need to remove the mounting screw on the flame sensor before gently pulling it out from its enclave.

At this point, you visually inspect it to determine whether it needs a simple cleanup or will need a replacement. For example, if the flame sensor’s insulation seems intact yet looks sooty or burned or with some corrosion, it may need a simple cleanup. However, if the porcelain insulation has inconsistencies like cracking or missing pieces, you will need to replace the Carrier flame sensor with a new one.

You then need to mount a new replacement Carrier flame sensor or remount the cleaned flame sensor.

Turn on the power source and the furnace before opening the gas valve. Then, if the light comes on without shutting off again, you can smile again.


The Purpose of Cleaning your Flame Sensor

You must clean your flame sensor periodically to ensure the proper functioning of your furnace. Cleaning helps sand away the corrosion and dirt and restore the metallic rod to its clean original surface status. You can always use a fine grit or emery cloth for cleaning. Further, a finer grit works better than a courser one. Therefore, it can help to check and go for the finest to prevent grooves that gather carbon emitted from the flame.


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What You Need to Do When the Sensor Fails to Work

Sometimes, you can clean the sensor, try and fail, before replacing it with a new one. However, it can still fail to work, which depicts a more significant issue than the flame sensor. Based on the type of gas furnace you have, you should call for an HVAC specialist to check and advise further.


Final Remarks

Heating systems or gas furnaces are crucial to the operations of your home or business. It is thus vital to understand what a flame sensor entails, the different types, and how to locate and replace them. Hopefully, this piece not only educated you about the diverse kinds of flame sensors but equally informed you on what can work best for your furnace.


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