Terrace heater, hall heater and BBQ hut heater – Airrex AH-300
Harry Mäkelä has an impressive terrace in his house. Mäkelä uses his grill a lot in winter, so the Airrex infrared heater may be switched on from Friday until Saturday. “We used to use this duct-shaped fuel oil heater. We found its flame and blast slightly dangerous in terms of heating a BBQ hut constructed of log beams with a diameter of 20 cm. A few years ago, when my son acquired an infrared heater and put it by the door of a 200-square metre maintenance hall as a kind of an air curtain, I decided to get these devices for our personal use as well. In temperatures of 20 degrees below zero, we consume around one litre of oil per hour in the BBQ hut. The 2-storey terrace is 17 metres wide and 5 metres deep. One Airrex AH-300 heater is in the lower terrace and one is upstairs. When we had to start refuelling the old heater with fuel oil, the tank of the new heater, in comparison, remains almost half-full,” Mäkelä describes his experiences. In Mäkelä’s experience, an exhaust pipe is not necessary in a big terrace or even in a BBQ hut. The heater does not emit any smoke at all because the oil burns so cleanly. Switching off the heater only causes a small fizzling sound, after which you can smell fuel oil for a while. Mäkelä, however, reckons that the consumption and odour emissions of older Airrex infrared heaters could be reduced if at least their filters were replaced. The heaters have been used for 3–4 years without requiring any particular maintenance. “I can warmly recommend these heaters to everybody, I have been very satisfied with them,” Harry Mäkelä says, summing up his experience. READ MORE ABOUT DIESEL HEATERS
Flower friendly Airrex AH-300 infrared heater solves greenhouse heating problem
Three years ago, at the Munkkivuori Garden, it was considered how the premises would be kept warm and the flowers happy. The gas heater didn’t work, but the diesel-powered Airrex AH-300 was chosen as the right heating solution. The garden has a smaller store section and a larger greenhouse. The entire space is about 5 meters wide and 30 meters long. Initially, they purchased one heater, but very quickly they bought another to the store section. The product has been very easy to use and working perfectly. Now the company has even bought a third heater. – We have been very pleased with these infrared heaters. Two of them are constantly in use and the third is used when needed. On the greenhouse side, the heat is kept at just under ten degrees Celsius and then at the store again at 13-14 degrees Celsius, says store manager Aki Lahtinen. ”Cost-wise, I can say that Airrex is much cheaper than gas heaters” The AH-300 has a charm of comfort and the flowers are happy. The device is almost odorless and produces carbon dioxide, which is great in such an environment. The 15kW / h heating output is just optimal and the low fuel consumption has brought the desired cost efficiency. Workers do not have to worry about using the equipment, just refuel and let the heater do its job. – Yes, these are easy to use, all you have to do is refuel. In terms of cost, I can say that it is much cheaper than gas-fired heaters, says Lahtinen. The Airrex AH-300 has many things that make it easy to use in such spaces. It can be easily moved and does not require a separate exhaust pipe. It is almost odorless and does not make any noise. Infrared radiation heats the material instead of the air. No fan is needed so dust or other contaminants do not rise from the floor. All in all, the Garden has been very satisfied with Airrex heaters. The thermostat-controlled heater is set at the desired temperature and then everyone can concentrate on the essentials. Read more about AH-300
Airrex AH-300 helped cut a garage’s costs significantly
Two years ago, Riku Turunen from Kontiolahti was considering the heating costs of his industrial hall. It consumed a lot of power and the bills really reflected that. Things had to change in a sensible manner. Riku’s garage hall is 135 square metres in size, and the highest point of the roof is at four metres. The large roll-up doors are prone to waste heat, so the task was a challenging one. Airrex AH-300 was selected as the heating device. AH-300 is an almost odourless, diesel-powered infrared heater with a 100% efficiency that is very well suited for industrial halls such as Turunen’s garage. Practice showed instantly that Airrex was a great solution because the device was easy to use as well as cost-efficient. “I must say that over the past two years, I’ve noticed how reliable and easy this device is to use. It’s mainly been in one place, and I’ve had no need to do anything to it although I’m using it all the time.” Besides convenience, savings are playing an important role now. “Earlier, if a period of, say, three weeks incurred an expense of a little more than €680, now I’m only spending €370, fuel included. Annually, that’s quite a big sum of money,” Turunen ponders. Once again, all that was needed was one device to solve issues. Airrex AH-300 reduced heating costs, and Riku Turunen can now focus on the essential – conducting his business – without any worries. READ MORE ABOUT AIRREX AH-300
Moisture and diesel infrared heaters
When heating cold spaces, the moisture tends to condensate on windows, metal structures or other structures in the heated space. From where does this moisture actually come? As a rule, air contains humidity in the form of water vapour: the hotter the air, the more humidity there is in it. Cold air cannot hold as much moisture as warm air. Air that contains water vapour heats up quicker than solid structures. Warmer air gathers more water vapour, but the solid structures in the heated space remain cool. The air close to the structures cools down, and the amount of water vapour in the air exceeds 100% RH. When the relative humidity of air exceeds 100%, water vapour in the air starts to condensate into droplets visible particularly on windows and metal surfaces in the heated space. You can also witness the same phenomena on a frosty pint of beer on a terrace in the summer. Two measurement units for humidity The amount of water vapour in the air, or humidity, is described by two different concepts. One expresses the amount of water in the water vapour found in a cubic metre of air. This is referred to as absolute humidity. The other, relative humidity, expresses the percentage of water vapour contained in the air. Relative humidity may vary from totally dry air (0%) to saturated air (100%) that contains the maximum amount of water vapour possible. Oil heaters produce carbon dioxide and water vapour Airrex infrared heaters burn diesel or fuel oil extremely efficiently, using almost 100% of the energy contained in the oil for the heating of the space. In practical terms, this means that all of the 10 kW of (heat) energy contained in a litre of fuel is utilised. 10-kW heating capacity is enough to significantly raise the indoor temperature in most heated spaces. Once the desired working temperature has been achieved, Airrex heater’s thermostat steps in to control the heater, reducing fuel consumption and emissions. A litre of fuel or diesel oil burnt creates 2.7 kg of carbon dioxide and 560 grams of water. Heating dries the air The capacity of air to hold water vapour is almost directly proportional to the temperature of the air. The colder the air, the smaller the amount of water vapour it can contain. This explains why heating is the most effective way to dry out spaces. Even then, formation or entry of humidity from outside the heated space must be prevented. If the relative humidity in a largish hall space is 40% at 0 degrees Celsius, each cubic metre of air in the space contains 1.9 grams of water vapour (water). If additional humidity is prevented from entering the space, raising the temperature in the space from zero to +20 degrees Celsius reduces relative humidity to five (5) per cent. It does not take much to heat air The average heat capacity of air is 1.01 kJ/kg/°C, based on which it is possible to calculate the output needed to heat it. To raise the temperature of one cubic metre of air by one degree, you need approximately 0.00035 kWh of heating power. If the heated space is, for example, 300 m3 in size, the power required to heat the air in it from zero degrees to +20 degrees is just 2.1 kWh. In reality, however, the above figure is not enough because of the significant effect the structures and objects in the heated space have on the required heating capacity, not to mention any heat loss due to structural leaks and ventilation in the space in question. Humidity created by an oil heater is not a risk The fact of the matter is as follows: to heat a 300-cubic-metre space from zero to +20 degrees, you require about 10 kWh of power, or one litre of oil, at maximum. This translates into 560 grams of water vapour that is mixed with 300 cubic metres of air. The amount of water in each cubic metre of air is, then, increased by about 1.9 grams. If the initial amount of water vapour per cubic metre of air in the heated space was 1.9 grams, the figure after the heating would be approximately 3.8 grams. At +20 degrees Celsius, this translates into about 30% relative humidity, which will not cause a moisture damage risk to any structure whatsoever. Unique benefits of oil-fired Airrex infrared heaters Radiation heaters do not heat the air as such, but the objects in the way of the infrared waves. Thus, the structures and objects in the heated space will become warm quicker than the air. This efficiently prevents condensation of humidity in the air on the surfaces, minimising the risk of damage due to moisture. Another factor that reduces the moisture risk is fuel. Many infrared heaters use liquefied petroleum gas, or LPG, which, when burnt, produces carbon dioxide and water. It is, therefore, a very clean fuel. Airrex heaters are in practice just as clean, but they produce considerably less water than LPG heaters. One (1) kg of LPG produces approx. 12.8 kWh of energy when burnt. At the same time, 2.99 kg of carbon dioxide and 1.63 kg (1,630 grams) of water vapour are produced. Using diesel oil, the amount of water vapour produced to achieve the equivalent heating power is approx. 720 grams – less than half of that with LPG. This is a significant difference, at least for anyone wishing to minimise the risk of moisture damage. Infrared heat dries out structures As described above, infrared heating increases the temperature of the structures and objects in the heated space rather than the air. This prevents condensation of moisture on the surfaces of the structures. Infrared heaters can also be used to remove humidity in applications such as the drying of moisture damage from concrete structures, for example. If there is moisture in the structures of the heated space from the time of construction or for some other reason, infrared heaters can be used
What makes infrared heaters better than fan heaters?
There are many significant differences between an infrared heater and a traditional fan heater. For instance, instead of blowing, infrared heaters radiate heat. Infrared radiation heats materials, not air. To learn more about infrared radiation, visit, for example, Wikipedia. You can feel the heating effect of an infrared heater even outdoors in windy weather because the heat will get through instead of being whisked away with the wind. The warm air blown from the fan heater will disappear in the wind right out of the heater. Airrex infrared heaters are an excellent choice for, for example, service tasks that have to be performed outdoors, e.g. changing a tyre of a car or repairing machinery (forest harvester, tractor, etc.) in field conditions.
Large space heaters and exhaust management
Not many enjoy the exhaust gases produced from burning diesel or fuel oil. A lot of people have found that the gases cause unpleasant symptoms in the respiratory system, mouth and throat, or even eyes, as the most sensitive people have reported.Exhaust management is not a problem for users of Airrex large space heaters that burn the fuel so efficiently that a separate exhaust outlet to the outside is not needed. If the combustion is incomplete, the exhaust will contain various harmful compounds. Unburnt hydrocarbons, carbon monoxide, various particulates, nitrous oxide and, of course, carbon dioxide. In case of high-quality hydrocarbon-based fuel, such as diesel, it is possible to achieve near-perfect combustion, meaning that the exhaust emissions consist mostly of carbon dioxide that is not dangerous as such, and water in the form of water vapour. Perfect combustion is the reason why Airrex infrared heaters do not require separate exhaust piping. Kymenlaakso University of Applied Sciences (KYAMK) is one of the few institutes in Finland that perform emission measurements. Marko Piispa, leader of the emission measurement unit, recalls that the emissions from the Airrex heaters were low. He does not comment on their safety when used in sealed spaces: this can be determined by studying the guidelines and limit values set out by the authorities. Airrex infrared heaters and exhaust gases According to the Decree of the Ministry of Social Affairs and Health on concentrations known to be harmful (HTP) and the Ministry of the Environment procedure on carbon dioxide levels in indoor air, the maximum allowed concentration of carbon dioxide during normal weather conditions and while the room is occupied is 1,200 ppm. The acceptable exposure limit at workplaces during an 8-hour workday is 5,000 ppm. Correspondingly, the amount of carbon monoxide in the air during an 8-hour workday should not continuously exceed 10 mg/m3. The limit for nitrogen dioxide concentration known to be harmful is 6 ppm, or 11 mg/m3, over 15 minutes of exposure. Operating at full capacity, Airrex AH-300 produces one milligram of carbon monoxide per cubic metre of air, meaning that the recommended limit value would not be reached during 10 hours of working. As heaters rarely operate at full capacity all the time, the maximum working time is much longer. And, if normal ventilation is ensured, carbon monoxide creates no risk whatsoever. Harmless as such, carbon dioxide is, in fact, very important for the human body. According to the emission report by KYAMK, exhaust gases from Airrex AH-300 contain 10% of carbon dioxide that is very quickly mixed with the air in the room space. This is why the carbon dioxide emissions are not considered significant. Nitrogen oxides created when burning diesel and fuel oil are considered hazardous to health. Noteworthy in the emission measurement report of an Airrex AH-300 operating at full capacity is that the nitrogen oxide emissions with biodiesel were 201 mg/m3 while those with regular diesel were 183 mg/m3. If exhaust gas is inhaled directly from the end of an AH-300 exhaust pipe, nitrogen oxides cause more stress on the body than recommended (6 ppm, or 11 mg/m3, 15 min of exposure), but the concentration decreases significantly when the exhaust gases mix with the air in the heated space. As regards an Airrex AH-300 operating at full capacity, the value will remain below the concentration known to be harmful (HTP) determined by the authorities when the volume of the heated space is approximately 200 cubic metres. This translates into a room that is approximately 8 x 10 x 2.5 metres in size. If the ventilation of the heated space is in line with the recommendations, i.e. a complete air change per every two hours, Airrex AH-300 can be used in spaces smaller than 100 cubic metres in size without risk of any health hazards due to nitrogen dioxide. With a capacity of 13–15 kW, Airrex AH-300 warms up such a small space very quickly, after which full capacity is no longer needed. This means less nitrogen oxide emissions and, subsequently, negligible health hazards thereof. Emissions in summary In summary, Airrex infrared heaters do not produce dangerous amounts of carbon monoxide – and no separate exhaust piping is required. The carbon dioxide that is created is no more a health hazard than carbon dioxide normally found in the air. During initial heating in a small space, the level of nitrogen oxides created may rise to concentrations determined hazardous by the authorities. The risk can be reduced by staying away from the (small) space during the initial heating and ensuring normal ventilation thereafter. The risk can be eliminated entirely by leading the exhaust gases outside the heated space. The smaller amount of nitrogen oxides created during the less capacity-intensive continuous heating keeps the level below the concentrations known to be hazardous. In a nutshell: a well-designed diesel heater can achieve such perfect combustion that there is no need for a separate exhaust pipe. After reviewing the calculations, this is also confirmed by Marko Piispa, who performed the emission measurements: “Emissions from the Airrex heater were quite low. They do not present a health risk in a large hall with appropriate ventilation.” Visit our webstore to read more about the safe and efficient Airrex heaters .
Considering a diesel heater? Tubular fan heater or a safe infrared heater?
The energy contained in diesel or fuel oil can be used for heating by burning the oil. Simple traditional auxiliary heaters consist only of an oil burner and a fan that is used to direct the heat from the oil burner to the desired spot in the form of hot airflow. Airrex infrared heaters also include an oil burner, but instead of a naked flame, the heat is formed in a heat generator doubling as the exhaust system. From the heat generator, the heat is radiated to the surrounding atmosphere in the form of infrared waves. The heat radiation can be directed using the heat reflector structures in the heater. Single- or multi-stage combustion diesel heaters The forced airflow of traditional oil heaters with a burner and fan transfers all particles of the burned oil, including exhaust gases and unburned particles, directly through the heater into the heated space. Even with an efficient burner, the exhaust gas will contain small amounts of unburnt hydrocarbons and any contamination in the fuel. This will cause different kinds of smoke and odour emissions. Basic tubular heaters simply use the fan to circulate the air in the heated space pass the oil burner. This means that unburnt hydrocarbons from the oil burner “supplement” any impurities already in the heated space air. The amount of unburnt hydrocarbons increases significantly if the diesel or fuel oil does not burn efficiently. This is usually the case during the starting or stopping of the heater or if there is a problem with the fuel supply to the burner. Airrex infrared heaters burn the diesel or fuel oil very efficiently because, after the oil has been burned in the burner, practically all the remaining hydrocarbons are burned in the 3-stage exhaust system that doubles as the heat generator. In practice, the exhaust is left with only harmless carbon dioxide and water without any unburnt hydrocarbons causing unpleasant odours and/or health hazards. Airrex auxiliary heaters utilise practically all the energy contained in the fuel, meaning that they are highly efficient and consume very little fuel. Exposed or protected oil burner? Basic fan-equipped diesel and fuel oil heaters have their oil burners in direct contact with the outside air, exposing them to any impurities and humidity in the air. This can result in corrosion or dirt build-up in the burner structures, decreasing the performance and reliability of the burner. If you use a fan-equipped auxiliary heater with an oil burner as the heat source, you must always make sure that the air going inside the heater does not contain any combustible material, such as dust, straws of hay or any combustible material that can be carried by the airflow. Another thing to remember when using this kind of a heater is that you also must consider the fire hazard caused by the hot air coming from the heater and any smouldering particles carried in it. In Airrex infrared heaters, the oil burner is enclosed inside the device and has its own separate air intake channel. All air coming to the burner is burnt, and the resulting exhaust gases are directed to a long exhaust system that doubles as the heat generator. The flame of the burner is not in contact with the surrounding space, and exhaust gases and any sparks cool down and die out harmlessly in the exhaust system. The long exhaust system also protects the burner against damages due to any impurities and humidity in the air. Difference between heating by airflow and heating by radiation In case of a traditional oil burner, the hot naked flame heats the air directed past it by the fan. This means that the air in front of the auxiliary heater may be very hot. The heating effect becomes more even when the hot air mixes with ambient air. The heating effect of the heated air circulated by the fan can only be felt in places where the air can reach. In a large space with obstacles or structures blocking the airflow, there will be “nooks and crannies” where the heat cannot get. Heat energy radiated by an infrared heater does not heat the air but the objects with which it comes in contact. Therefore, you can be close to the heater without feeling uncomfortably hot. Heat radiation spreads evenly in the space, literally warming up the objects in its path from the inside out. Once the objects and structures in the heated space warm-up, they also warm up the space evenly. Do you want to circulate dust and air contaminants? Fan-boosted air circulation always circulates contaminants, dust and other impurities in the space as well. This spreads air contaminants everywhere, including people’s skin and lungs and from there further in the body. Heat radiation from an infrared heater does not cause any superfluous air movement that would cause dust or any contaminants in the heated space to migrate to the workspaces or supplies or in the bodies of people there. Humming fan and buzzing burner – or not? The humming sound of an efficient oil burner is familiar to all who have been around one. Traditional auxiliary heaters only have sound damping structures on the sides of the burner. And to ensure safe heater operation, the heated air must be made to move efficiently. This requires a fan that inevitably produces noise. Today, some high-end traditional auxiliary diesel heaters already have reasonably silent fans. In case of the fully enclosed Airrex infrared heaters, the air to the oil burner is conveyed via a separate sound dampening channel. The exhaust system located downstream the burner utilises any energy left from the burned oil and also dampens the “exhaust noise” down to a very moderate level. Airrex infrared heater’s noise level is 48 dB, corresponding with that of a quiet speaking voice. Burner requires electricity – a fan easily doubles the need for power Traditional auxiliary oil heaters have some components that require electric power: fuel pump, oil burner with the associated control electronics and the fan that
Fuel-fired large space heater – how much supply air is needed, and other questions.
How is it possible to have a large space heater without an exhaust pipe? It is made possible by using pure high-quality fuel that ensures perfect combustion. Of the exhaust, more than 99% is carbon dioxide and water vapour that are parts of the air that we breathe. There is practically no soot or other fine particles, not even carbon monoxide. Exhaust from clean-burning high-quality fuel contains very low nitrogen oxide levels that do not constitute a health risk. To learn more, read this article. Water vapour is in no way hazardous to health, and the moisture in the exhaust gas of Airrex infrared heaters does not harm the structures of the heated space. Oil heater and carbon dioxide load There are two stages in warming up enclosed spaces, such as halls and warehouses: initial heating and continuous heating. During the initial heating, the fuel heater blows or radiates heat at maximum power, producing the maximum amount of exhaust gases. Once the space is heated, continuous heating only requires a fraction of the heater’s heating capacity. In this stage, Airrex infrared heaters typically use only a small amount of fuel per hour. Due to the two heating stages, the exhaust load in the heated space also varies greatly. Therefore, the ventilation performance required to ensure an appropriate amount of supply air and a level of carbon dioxide suitable for people to breathe varies. Load on full heating capacity Airrex infrared heaters are offered in three capacity classes. The heating capacity of the smallest Airrex AH-200 is 13 kWh, the heating capacity of the medium Airrex AH-300 is 15 kWh, and the capacity of the largest AH-800 is up to 22 kWh. The capacity is achieved by burning approximately 1.0–2.5 litres of fuel per hour. Burning 1.5 litres of fuel or diesel oil produces approximately four kilograms, or 4,000 grams, of carbon dioxide. The burning process requires approximately 22 cubic metres of air. Correspondingly, to burn 2.5 litres requires approximately 36 m3 of air and produces approximately 6,600 grams of carbon dioxide as a combustion product. The carbon dioxide produced by the heating makes working in the heated space more stressing. But when does it become a health risk? Carbon dioxide is not dangerous as such, but large concentrations are considered harmful Carbon dioxide is one of the normal gases in the air and, as such, not dangerous at all. On the contrary, the human body needs carbon dioxide to work. If the level of carbon dioxide in the air increases, we feel like we are “running out of breath” and the body reacts by automatically increasing the rate of breathing. A high level of carbon dioxide in the air is reported to cause headache, fatigue and a feeling of stuffy air. The amount of carbon dioxide in the air is expressed in ppm, or parts per million. The amount of carbon dioxide in the open air is approximately 380 ppm. According to the Decree of the Ministry of Social Affairs and Health on concentrations known to be harmful (HTP) and the Ministry of the Environment procedure on carbon dioxide levels in indoor air, the maximum allowed concentration of carbon dioxide during normal weather conditions and while the room is occupied is 1,200 ppm. The acceptable exposure limit at workplaces during an 8-hour workday is 5,000 ppm. This translates into carbon dioxide concentrations of half a per cent (0.5%) mixed in the air. Something about the level of stress caused by carbon dioxide on the human body can be deduced from the fact that submarine crews work and live in an atmosphere that contains approximately one per cent (10,000 ppm) of carbon dioxide. Even a concentration of 2%, or 20,000 ppm, has not been found to cause adverse health effects during short-term exposure. How much does an auxiliary oil heater increase the carbon dioxide concentration in a hall space? The specific weight of air varies according to the temperature and humidity of the air, the average used in these calculations being 1.225 kg/cubic metre (at sea level). Of this figure, the amount of carbon dioxide is 0.038% = 0.0004655 kg, or approximately 0.47 grams. The 5,000 ppm carbon dioxide exposure limit allowed at workplaces translates into approximately 6.125 grams of carbon dioxide per cubic metre of air. Considering the amount of carbon dioxide already in the air (0.47 grams/m3), the amount of extra carbon dioxide allowed to be mixed in the air is 5.655 grams. If we now presume that there is no ventilation whatsoever in a heated space with Airrex AH-300 infrared heater blasting away at full capacity, how big must the space be in order to avoid any health hazard due to the exhaust? The four kilos, or 4,000 grams, of carbon dioxide produced per hour requires a space of approximately 710 m3to dilute below the 5,000 ppm concentration level. The area of a hall space that is four (4) metres high should, then, be approximately 180 square metres. Using the more powerful Airrex AH-800 for an hour at full capacity would require a hall space of approximately 1,150 cubic metres to keep the increase in the carbon dioxide level below the recommended 5,000 ppm limit. Continuous heating requires only one-third or significantly less fuel compared to full capacity heating. This means that carbon dioxide emissions are only one-third or less by comparison. Subsequently, the volume of the heated space only needs to be 230–380 m3 to keep the carbon dioxide level below the recommended workplace exposure limit. The floor area of a 2.70-metre high hall space with a volume of 230–380 m3 is 85–140 square metres. The significance of ventilation The above examples are theoretical in nature because there are not that many heated spaces that are completely sealed. On the other hand, a combination of a particularly low ventilation setting and use of a fuel-fired heater will result in continuously increasing indoor air carbon dioxide levels, something that should be considered. If the heated space is ventilated in a normal manner in compliance with the regulations, meaning a