Why there is thrust in the furnace. Factors affecting traction. Use of a rotary turbine

   Thrust is the movement of flue gases up the chimney, from the area high blood pressure  in the region of low pressure. In the chimney (in the pipe) of the established diameter, not less than 5 m in height, a rarefaction is formed, which means that a necessary minimum pressure drop is formed between the lower part of the chimney and the upper one, the air from the lower part goes up into the pipe. This is called traction. Thrust can be measured with special sensitive instruments, or take a fluff and bring it to the pipe.

Accordingly, if you take a pipe of sufficient diameter, in which the air has the ability to move, and pull it up high, then the air from the ground will constantly flow upward. This is because the pressure is higher at the top, and the vacuum is greater, and the air tends to go there in a natural way. And in its place will come the air from other sides.

In the "firebox + chimney" system, the thrust is effective, even if the furnace does not work. When burning firewood creates an increased pressure in the internal combustion chamber and the flue gases that form during combustion require an outlet. All furnaces and furnaces have a construction that leads to the flue gas, The height of each chimney is selected so that the thrust is created, the initial rarefaction is created. When burning in a combustion chamber, heat and gases are released and an overpressure arises. Gases move in the chimney under the influence of traction, tend to go from the region of elevated to the region of reduced pressure. Laws created by nature work.

What is a "reverse pull"?

Reverse traction is the movement of flue gases from the area of ​​increased pressure into the region of the lowered, but not upward (as described earlier), but downward. The reverse thrust is formed by inversion of pressure - when the pressure is higher at the top than at the bottom. The reasons are the most common things: if the room is airtight, there are double-glazed windows, and together with the chimney, the extractor draws air from the room. Here and creates a reduced pressure relative to the surrounding terrain. Therefore, with a kindling, when the chimney is still cold, the air in the upper part of the chimney has a higher pressure than in the room. Smoke will certainly go where it is easier for him. This phenomenon is called a "cold pillar". When the chimney cools down, a column of cold air is formed inside, which presses downward, there is a reverse thrust. If the pressure in the room is not lowered, then the warm air will go up, into the chimney.

Thus, if there is no room in the room kitchen hoods  and it is not sealed, there will be no stagnation of cold air in the furnace. Check: if in winter before burning the fireplace, first set fire to the newspaper and bring it into the pipe (bypassing the furnace part), then the fire will not go into the room, whatever the column of cold air. The fire will burn and go out only in the chimney. This indicates that the pressure in the room is not lowered and warm air normally tends upward. When kindling a stove or fireplace, sometimes the smoke goes into the room. This is due to the fact that the resulting flue gases at the time of the initial heating have not yet heated up, and, when lifting upwards, coming into contact with the cold walls, immediately cool down. After that, they, naturally, will rush down. Again, there is a reverse thrust. To normalize the thrust in the furnace, it is important to melt properly, understanding the processes occurring there.

Traction control

Another emerging issue is overturning traction. In what cases is this happening? If the chimney is long and cold (often brick), and the pressure is reduced. If the ratio of the dimensions of the furnace and the section of the chimney correspond, if there is a normal pressure in the room, there is still a situation where when the fire is ignited, there is not enough force and the flue gases can cool down in the chimney and fall down. It happens in cloudy weather, wind. It happens that the fire normally flares up, but then smoke pours into the room. The air from the room is withdrawn, and the pressure is reduced, there is no air inflow. And the flue gases rise and cool down and crash down. What do you need to know in such situations? Open the window, if the room has double-glazed windows and is hermetically sealed. It is important to prepare firewood, their quality.

How to build a chimney correctly?

Prefabricated chimneys, sandwiches, collected by smoke and condensate. There is an opinion that it is more appropriate to collect the smoke. Explain that at the junctions of the pipes there are cracks, where the flue gases entering the pipe are blocked. In contrast, it is believed that if collected by smoke, then the smoke will stop coming out. Solve such a dispute is possible, if in the operating furnace to drill in any place of the chimney hole and see what will happen. The most interesting thing is to do this at the bottom. The hole drill any centimeter in diameter. What will you see? From this hole, no smoke will not go out (unless you close the chimney tightly from above).

What is more important to consider when assembling the chimney?

The main thing is to take into account the fact that in each chimney condensation can occur, especially when it is still cold and warm flue gases, rising very cold. Condensation may settle on the walls, which drains through the pipe. If the chimney is collected by smoke, the condensate easily penetrates into the cracks and moistens the insulation, completely depriving it of its heat-insulating properties. Here and before the fire nearby. Therefore, the assembly of modular chimneys is conducted only on the condensate. Chimneys are assembled on a clear joint, with a sealant to inner tube. However, the chimneys themselves must be of good quality so that no foreign gaps remain. If the cracks remain - through them the air will go, and it turns out that there will still be no thrust.

But the chimney is big, tall! Not understanding what the reason is for the masters. Masters use a simple method: they cover the chimney from above and look where the smoke comes from. There are all kinds of inconsistencies in the chimney, which lead to the fact that air is sucked into the chimney. Remember? The air tends upward, to where the pressure is lower. Therefore, the more slots, the worse the pull is below. The assembly of smoke, unfortunately, does not take into account the very essence of traction. As a result, the fire burns, and the smoke rushes in all directions. Although the logic here is not complicated - the smoke goes from the area of ​​increased to the area of ​​low pressure, where it is easier for him.

What is the measure of traction?

Norm of draft for a standard fireplace or stove - an average of 10 Pascal (Pa). The draft for the smoke pipe is measured, since it is there that the evacuation velocity of the flue gases is seen and the correspondence between the dimensions of the furnace furnace and the diameter of the chimney.

What else affects the amount of thrust?

First of all, the height of the chimney. The minimum required height is 5 meters. This is sufficient for the appearance of a natural rarefaction and the beginning of the upward movement. The higher the chimney, the stronger the thrust. However, in a brick chimney with an average cross section of 140x140 mm., With a height of more than 10-12 meters, the thrust no longer increases. This is because the value of the roughness of the walls increases with increasing height. Therefore, excessive height does not affect the traction. A similar question arises among those wishing to use chimney channels in houses. They are of a large height and narrow section, so a serious fireplace is rarely connected to such a chimney.

Factors affecting traction:

The temperature of the exhaust flue gases. The higher the temperature, the faster the flue gases are directed upwards, a greater thrust arises.

Heating of the chimney. The faster the chimney warms up, the faster the pull is normalized.

The degree of roughness of the chimney, internal walls. Rough walls reduce traction, with smooth walls traction is better.

Shape of the section of the chimney. A circular cross section is a sample; oval, rectangular and so on. The more intricate the form, the more it affects the traction, reducing it.

• It is important to note that the ratio of the dimensions of the furnace, the diameter of the outlet branch pipe and the diameter of the chimney is also influenced. With the excess height of the designed chimney, one should think about reducing the chimney cross-section by an average of 10%. On the furnace, on the smoke branch pipe, install the adapter (for example, from the 200th diameter to the 180th) and take the 180th pipe itself. This is allowed by the manufacturers. If, for example, we talk about "EdilKamin", it is clear that he writes in instructions to the firebox, what diameter to take the chimney, depending on the height.

   For example:
   height up to 3 m - diameter 250,

height from 3 m to 5 m - 200,

height from 5 m and above - 180 or 160. Strict recommendations.

Other manufacturers (for example, Supra) admit that changes are possible. Some do not at all. Therefore, guided by instructions, do not forget about the processes taking place in the chimney.

How is the thrust measured?

First, flood the stove or fireplace. Stoke for at least half an hour to normalize the processes. Then, having made a hole in the pipe just above the smoke branch, insert a special de-meter sensor there and measure the draft. Check if it is redundant or not enough. Factors affecting the craving, a lot, consider a few more.

Rose of Wind

The situation when the prevailing winds blow directly into the chimney and reduce the draft or unfold it. The chimney is set on the windward side, of course, if the wind direction is determined. If the chimney is located far from the ridge and below, you can not use the leeward side. Multi-storey houses and trees also affect cravings. To compensate for wind gusts and unsuccessful location of the chimney, anti-wind deflectors are used. According to the standards, the chimney is half a meter above the ridge. If the distance from the ridge is 1.5 m - 3 m, then it is displayed in one level with a ridge. If the distance is more than 3 meters, then they act further according to the formula: from the horizon, drawn from the ridge, 10 degrees down. In practice, the chimney is made above the ridge, or in one level with a ridge. It is important to use one chimney for one oven.

For the normal operation of the vast majority of modern heating appliances, the chimney must be arranged. Its functioning, in turn, is impossible without sufficient traction. The term "draft" means a directed airflow that forms in the exhaust structure due to a difference in the temperature of the smoke and outside air, and also because of the difference in their density. Because of insufficient or worse - reverse thrust, the combustion products do not go outside, but return to the room, which can lead to disastrous consequences. Today we will talk about reverse traction; we describe its main causes and ways to eliminate them.

The concept of reverse traction. Traction control

Reverse traction is the exit of smoke streams not to the street, but their return to the heating appliance, whether it's a fireplace or a stove. If you find yourself experiencing this phenomenon, know that you should immediately stop the operation of the heating device and repair the malfunction.

There are cases when the air flow sharply and with an enviable regularity briefly changes its direction. This phenomenon was called "overturning traction".

The consequence of both of the above problems is incomplete combustion of fuel, which entails excessive smoke formation. Smoke enters the room and can harm the health of people living there.

According to experts, traction that fluctuates within 10-20 Pa is considered sufficient. If the thrust is lower, you need to determine the reasons for what is happening and bring the indicators back to normal.

You can check the traction in several ways.

1. Special instrument - anemometer, it provides accurate data of the speed of the directional air flow. If the device is not available, you can use the improvised means.
2. Using a sheet of toilet paper. Bring it to the door of the stove or fireplace and pay attention to which way it deviates. If in the direction of the room, there is a reverse thrust.
3. Smoke from a cigarette. If you smoke, you can use cigarette smoke as an indicator. The principle is similar to that described in clause # 2.
4. The color of the flame. If the flame has a yellow-golden color, then the draft is good.

Advice!   To check the direction and force of the thrust, bring a lit cigarette to the heater door and look at which direction the smoke will go.

Reasons for back pull

• The chimney pipe is too low. This leads to a difference in pressure, which entails a weak pull or its complete absence. The optimum height is 5 meters.
• Wind podpor, that is the phenomenon when in the immediate vicinity of the house there is a higher construction, preventing the formation of air flow.
• Incorrect chimney design.
• Problems with ventilation or its complete absence.
• The presence in the chimney of several narrow channels-smoke.
• Garbage in the chimney.

Elimination of reverse thrust

The process of eliminating the return thrust depends on the reasons that caused it. We will describe the most accessible and common ways to solve the problem.

Manipulations with a gate

Influencing the force and direction of thrust. Usually, during the construction of a stove or fireplace, two slats are installed. One is in the chimney, the other is in the stove or in its door. "Play" with the position of these dampers, this often increases traction, and the problem is solved by itself.

Advice!    If there is no traction, pay attention to. Perhaps it covers the chimney, because of which the smoke can not go out and comes back into the room

Application of the deflector

A deflector, also called a smoke pipe or a fluke, is a short pipe installed at the top of the chimney, designed to protect it from the wind, and to strengthen the thrust. Since the cause of the reverse thrust is often external factors, in particular, the air streams blown into the chimney by wind, setting the deflector is the easiest way to solve the problem.

Using the traction control (stabilizer)

it special device, creating air flows in the chimney and controlling their strength. It stabilizes the traction and, among other things, contributes to fuel economy, and also prevents the ingress of combustion products into the room.

Timely cleaning of the chimney

The cause of the emergence of reverse traction is often getting into the chimney of debris or accumulating there a huge amount of soot. Therefore, do not be lazy to systematically check the condition of the pipe and, if necessary, to remove clogging. today there are a wide variety.

conclusions

As you can see, the reasons for reverse traction can be very diverse, and the way to solve the problem directly depends on them. We strongly recommend that you monitor the operation of the heater and, if any malfunction is found, immediately take measures to eliminate it!

Related Videos

Backward draft

The reverse draft in the chimney is a process when the flow of gases from burning firewood does not go to the chimney outside, but in the opposite direction to the room. If we speak in scientific terms, then when fuel burns, an aerodynamic flow of flue gases arises in the exhaust structure.

The reasons for this phenomenon can be high buildings nearby, trees, as well as the location of the pipe below the roof ridge. There is a large number of such factors, so it is necessary to understand the problem that has arisen and to resolve the issue of strengthening traction with our own hands.

Reverse link detection

The reasons for the emergence of reverse traction can be several:

• Incorrect chimney design.
• Disturbance of ventilation.
• External factors.

Important! To notice the first signs of the return draft in the chimney is quite simple: the wood burns in an oven with a lot of smoke, the glass is quickly smoked on the door, and if it is opened, the smoke immediately spreads through the room.

If you do not understand how to increase the chimney draft, it can become not just bad, but also reverse. Check the traction in fairly simple ways:

• Bring to the open door of the furnace compartment a sheet of toilet paper, a burning candle or a lit cigarette and see which side the light paper, the candle flame or the smoke of the cigarette is deflecting, and with what force.
• If the furnace flame white, and a buzz is heard in the chimney, which means that it is required to reduce traction, since burning with such force firewood or other fuel will bring little benefit. Simply put, you heat the street.
• If the flame is yellow with a golden hue, the pull is good.
• Using a special device - an anemometer. On it you can get objective indicators if the wind speed is more than 1 meter per second.

To determine why the backward thrust has arisen, it is necessary to know the factors that cause it. In addition, it would be good to be able to solve the problem with your own hands.

Chimney design

The very design of the chimney is of great importance for traction. At too high a pipe draft always strong, and at low - small. The best option  is a product with a length of 5 to 6 meters.  In this situation, there is almost no problem with traction, and if a problem arises, it is clearly not because of the height of the structure.

In addition, it is necessary to pay attention to the area of ​​the chimney - it must correspond to the volume of the furnace. If this area is small and the volume of combustible fuel is large, the resulting combustion products do not have time to reach the narrow smoke hole of the pipe, so there is not enough draft. Disproportionately large chimney in relation to the size of the stove or fireplace leads to the fact that all the heat simply flies into the pipe. It is strictly forbidden that there are sections with different diameters on the chimney, since soot will accumulate on them, and there will always be problems with thrust.

A significant obstacle to the escape of smoke will serve as an uneven surface of the inner walls of the chimney. After all, any unevenness leading to deposits, as well as foreign objects that get into the chimney, reduce the diameter of the pipe, as a result of which it becomes increasingly difficult to melt the oven.

The shape of the smoke hole is another important point. The most favorable option is a round chimney, but a square or rectangular can create problems. After all, in the corners of a rectangular design, there are additional vortex flows of air. Very often, the reduction in thrust is associated with the pipe material. Metal chimneys are characterized by low thrust, as they instantly heat up and cool down quickly, and cold air falls down.Therefore, the most reliable in this respect are the classic brick structures.

Disturbance of ventilation

Pipe Location

The lack of ventilation in the room, where the furnace is located, can also lead to such a phenomenon as reverse thrust. It is necessary to check whether there are drafts in the room and how strong they are. If the wind is walking in the house, then it can knock down any direction of smoke.

For example, very often there are air currents, which are the result of the presence of stairs to the second floor. Therefore, it is not necessary to open the windows of the ladder, if it is located above the level of the furnace.

Important! With any design of the furnace or fireplace, a gas or solid fuel boiler in the chimney, an additional ventilation duct is laid. It helps to protect the operation of any heating unit.

Placing the chimney

This factor, like the location of the chimney, also has a large effect on the magnitude of thrust. For example, if it is located in the interior of the house, this not only positively affects the heating capacity of the furnace, but also maintains good traction even in severe frosts.

But the pipe placed on the outside of the building along the outer wall, with insufficient warming, warms up much more slowly, and it often forms condensate, which prevents the passage of smoke.

External factors

The cause of poor draft in the chimney - trees

Smoke can enter the room due to too high humidity in the street or in strong winds. Also, the reason may be a higher temperature on the street compared to the house, which creates a pressure difference. In this case, the owner of the house when igniting the oven will certainly hear the characteristic smell of burning. It should immediately open the window and ventilate the room well in order to remove the smell of smoke and simultaneously equalize the temperature.

A frequent cause of reverse thrust is the wind, causing turbulence over the roof. This can occur when in the immediate vicinity of the chimney there are tall trees or roof structures in the form of dormer windows and extensions, which are horizontal above the pipe itself.

Problem solving

To cope with the problem of reverse traction will help a special device - a deflector or a rotary turbine, mounted on top  chimney. These devices are a mechanical fan. Its main purpose is to suck smoke from the chimney's chimney at the expense of a special nozzle. Rotating due to the force of the wind, it creates a vacuum of air in the chimney, so that the thrust is improved.

Also worth checking the gate - a special damper, which regulate traction. One slide is located in the duct of the chimney, and the second is usually in the oven or in its door. Several times change its position, thereby increasing the pull in the pipe and, possibly, by that you will solve the problem.

In some cases, the return thrust can occur only for 1-2 days, for example, when the furnace has not been used for a long time, or because of the wet weather.

Eliminate the causes of poor traction

How to act in this case, and is it possible to solve the problem with your own hands? All is simple enough - find the reason and eliminate it. For additional safety, use the chimney draft stabilizer. To get rid of cold air in the pipe after a long break in the kindling, you can use ordinary paper. To do this, it is necessary to burn some of it, thus heating the air in the furnace and the chimney. Then, according to the laws of physics, he can rise upward, pushing cold masses out. After this procedure, you can safely melt the furnace - there will be no problems.

Another point - you need to clean the chimney in time, and if possible, then install a special tee in the chimney for its quick and high-quality cleaning.

Conclusion

The safety and efficiency of the heating devices depends on the draft in the smoke channel.  As soon as the first signs of problems with this design are noticed, it is immediately necessary to check the patency of the pipe and to decide the issue of improving the draft in the chimney. Penetration of carbon monoxide into the house is very dangerous for people living in it. All repair work  it is quite realistic to do it yourself. But if you do not have the skills, you can invite specialists who will solve the problem and make the operation safe.

To the house was warm - you need to build an oven, a fireplace or install a gas boiler. And that the fire in the hearth is always gay, the room was cozy and the air in the house is clean, you need to take care of the chimney equipment. The design and construction of smoke removal systems should be treated with due attention, and not leave it at the end, otherwise various unpleasant surprises are possible.

The purpose of the chimneys - the removal of combustion products and the creation of traction in the furnace - just seems like a simple job. In fact, this is a hard work - after all, the chimney has to constantly withstand a frenzied onslaught of fire and smoke. And the task of correctly building it is not so simple as it might seem. Although over the centuries people have mastered the intricacies of taming the fire, the chimney remains that part heating system, the construction of which must be approached very responsibly. Incorrect operation of chimneys can lead to a fire at home or poisoning of its inhabitants with carbon monoxide. Especially a lot of trouble conceals a chimney, built in the old manner by a self-taught master, combined with modern systems  heating.

Tip

The right choice makes the operation of the chimney a safe and carefree process, and also guarantees the most complete combustion of fuel, provides an ideal traction, resists the effects of condensate and aggressive acids.

Secrets of traction

The principle of operation of the chimney is based on the draft - the ventilation effect in furnaces, which arises from the difference in air temperatures outside and inside the pipe. With increasing this difference and the height of the tube, the effect increases. Often, through the ventilation holes in the door of the stove, air is sucked in with great force, creating in it real fire vortices. The density of warm air is less than that of cold air, which leads to a difference in pressure inside and outside the pipe. Since the house where the furnace is located is not sealed, due to the difference in pressure at the foot of the building and the top of the pipe, a flow of air is directed inwards. At the same time, warm smoke exits through the pipe at the top of the building, and cold air penetrates through the inevitable crevices at the bottom. Occurs natural ventilation  air. Thus, the furnace is not only a source of life-giving heat, but also a means of providing ventilation to the building. Even in the recent past, countryside  and small towns, furnace heating was the main type of heating of the home and the proper arrangement of furnaces was given serious attention. Until now, in places where there is no gas, the stove for heating and cooking in the house is as important as it was many years ago.
Chimney draft depends on channel section and height chimneys. There is a special table for the dimensions of the smoke channels. For example, to create a normal draft in the fireplace, the section of the exhaust barrel must be at least 1/10 of the area of ​​the inlet of the furnace. On the other hand, excessive large section the pipe also reduces the draft: gases exit at low speed and have time to cool down, their density rises, and the thrust drops. To improve the combustion, it is customary to increase the height of the chimney, but to a reasonable limit, since the higher the pipe, the greater the resistance the flue gases experience. When constructing stoves and fireplaces, an altitude of 5 m from the level of the grate is considered optimal. This should be enough to ensure reliable traction at any time of the year in all weather conditions. However, excessive traction is not economically viable, since it leads to accelerated combustion of fuel. It affects not only the height of the pipe, but also its length - after all, when laying the chimney, you also have to build horizontal sections. Therefore, it is recommended to increase the chimney height by 1 m per meter of the horizontal pipe section. The length of such horizontal sections should not exceed 2 m, since they accumulate soot and reduce the draft of the chimney. If the dimensions and shape of the room allow, it is necessary to move from horizontal to areas with a slope of 45 degrees - while reducing aerodynamic losses and traction increases.

Ideally, for an efficient operation of the flue system, each furnace must have a separate gas outlet. Connection to one smoke channel of two furnaces is undesirable. This is done in exceptional cases and only as a forced measure. But if one can not do without it, then the following rule is observed: the distance between connections of furnaces on solid fuel should be not less than 0,75 m, and for working on gas - 0,5 m. After all in case of connection of several furnaces to one chimney their work may vary. The higher the smoke channel, the stronger the thrust, and this can be a significant disadvantage if the furnaces are located on different floors. With simultaneous combustion, the draft of the lower furnace will be much stronger, which will prevent the free exit of gases from the upper stove. As a consequence, the upper furnace can have a worse draft, which leads to smoke in the room.
Nowadays modern cottages are rarely heated with ovens, they are successfully replaced by various boilers. But thanks to fashion fireplaces became an integral part a country house. And if in one house it is planned to build two fireplaces, for example, one on the first floor, the other on the second, it is better for everyone to have their own, separate chimney. The use of a common chimney is permissible only in exceptional cases and provided that the fireplaces connected to it are owned and controlled by one owner, and even then with many reservations.
When building a house and laying ovens, remember that the smoke and ventilation ducts  are made separate and must have a high-quality performance, i.e. without cracks and unevenness in the trunks. The exhausted combustion products from one furnace must not enter another flue or ventilation duct.

Tip

The configuration of the metal chimney can be different: from the so-called "straight", to a complex structure, which allows to bypass the bearing elements of the ceilings and roofing. The brick chimney, as is known, is exclusively vertical.

Design Features

Before starting the stoking of the furnace or installing the boiler, it is first of all necessary to decide how to arrange the chimney and where to install it. There are three main types of pipes - in the first place this classification refers to brick chimneys. In the place of their installation the chimneys are divided into indigenous, perforated and wall chimneys. The root chimney is installed on its own foundation in the form of a separate brick riser. Root pipe can combine several furnaces located on one level. The chimneys are supported directly on the furnace, preferably not on the brickwork, but on the ceiling made of reinforced concrete slab with a thickness of at least 50 mm. In this case, you can repair the stove without disassembling the entire structure.
In rooms with capital walls, most often put wall chimneys. They are economical and convenient, because they are laid out together with walls, often close to ventilation ducts. Use a common wall chimney for two stoves installed on different floors, is not allowed, since the furnaces have different traction, which depends on the height smoke channel. Therefore, with simultaneous combustion, the lower furnace will have a stronger thrust, thereby worsening the work of the upper one, which will smoke and suffocate. The wall chimney can not be laid on a clean cement mortar. It is very dense and does not let air through. On the cement joints, soot particles will accumulate to form streaks, which can later appear from the outside of the wall. Therefore, it is better to spread the wall chimney on a clay or lime mortar.
Chimneys are better placed in the inner walls of the building. Passing through the channel, the smoke gives its heat to the walls, which can serve as an additional source of space heating. If the channels are in the outer wall, then because of the low external temperature, the gases are cooled. This has a negative effect on the thrust in the furnace. In addition, from the gases are released resinous substances that are deposited on the walls of the chimney. Sometimes these deposits can penetrate through the masonry, appear on the outer walls of the building. Therefore, in the outer walls chimneys are located only in exceptional cases. In addition, when the riser is mounted at the outer wall, it is necessary to increase its thickness. The most economical and expedient method is the installation of chimneys in the capital brick walls  simultaneously with the construction of the house.

Sometimes in the layout of the house the oven is not located at the wall, but in the middle of the central room. To smoke from the furnace got into the chimneys of the inner wall, mount a hose sleeve, the length of which should not exceed 2 m. In the case of erecting the walls of a house from combustible materials, for example, a bar, it is recommended to use root pipes. It is preferable to combine the smoke stacks into one array, in this case one chimney is laid out on two-three chimneys. It is necessary to construct one ventilation duct.
Choosing a place to install a chimney on the roof of the building is also a difficult task. If the chimney is located below the roof ridge, the draft will depend on the direction of the wind, and the swirls behind the roof will reduce the chimney draft. To solve the problem, it is necessary to increase the chimney in such a way that it is above the ridge. Here, too, there are certain rules, and the height and diameter of the pipe is not least dependent on the height of the skates and the shape of the roof.
The structure of the chimneys depends on the design of the furnace, its location and power. Depending on these primary indicators, decisions are made on constructive device  overlapping and walls located near the furnace. To ensure a good draft of the pipe and to clean its internal surface from soot, which is often the cause of fire, a special hole is made in the pipe wall to clean it.

Tip

To prevent the spread of fire to other floors, in case of fire from the outside, the chimney must remain static for at least 90 minutes. At the same time, it is impossible to allow the transfer of heat through the outer shell of the chimney and the increase in the temperature of its surface on other floors to dangerous values.

Difficult choice of materials

Chimneys are built of solid ceramic (clay, red) bricks, asbestos-cement or pottery (ceramic) pipes, metal and heat-resistant concrete blocks. Pipes used for removing combustion products of fuel have a significant advantage over the chimneys laid out of the stone. Their internal surface is smooth, which provides minimal resistance to the movement of the gas flow and helps to reduce the deposition of soot. In addition, this design is often superior to brickwork and in terms of service life.

The choice of a particular material and design depends not so much on the architectural style of the house as on the type of furnace, fireplace or boiler from which smoke is diverted and the type of fuel used. The consequences of incorrect choice of chimney can be very different - thrust failure and unstable operation of the combustion unit due to improper selection of the section, geometry or type of chimney; smoke in the living area and possible carbon monoxide poisoning due to non-compliance with the norms of construction and installation, and even fire.
For example, brick pipes, most recently the most common ones, do not work well with the features of modern boilers operating either on gas or liquid fuel, or combined. These automated boiler houses usually operate in "transient" modes - starting, heating the coolant to a specified temperature, then stopping and starting when the coolant temperature decreases. Such a boiler operating mode leads to constant changes  temperature in the chimney. In addition, when using them, much more water vapor is generated than when burning, for example, firewood. And this drastically changes the living conditions of the chimney. Condensate (vapor deposited on the walls of the upper part of the chimney), connecting with the combustion products of the fuel in the boiler, forms aggressive acids or their mixtures. These processes lead to a strong and rapid destruction of chimneys, the formation of microcracks and the penetration of flue gases from the boiler into the living quarters. After the formation of cracks in the chimneys, the process of their destruction is avalanche-like and causes concomitant destruction of the internal finish.

Tip

Chimneys and ventilation ducts must be maintained at all times. For this, there are regular preventive maintenance, inspection and cleaning of the walls, which will prevent emergence of extreme situations.

The stainless steel chimney system with internal ceramic pipe can be installed in a country house  after graduation construction works  and does not require any additional finishing. In addition to its technical purpose, it is a composite element of the interior

In cottages with a large living area, where they use a powerful boiler equipment, signs of destruction of brick chimneys under constant operation may appear in 13 years, depending on the type of fuel used. Besides, in brick chimneys, as a rule, it is difficult to provide a smooth surface of the channel, as a result of which the soot deposits on the unevenness, which over time reduces the aerodynamic section of the chimney and the draft. Despite all of the above, the brick chimney  is still relevant, for example, when burning solid fuel  (firewoods and bath ovens are heated with wood, and boilers adapted to it). Moreover, the brick is traditionally well combined with the architectural appearance of any building.

To avoid negative phenomena help inserts from corrosion-resistant stainless steel, manufactured under the existing channel of the chimney. Installation of the inserts is performed using high-temperature sealant, which ensures complete insulation of the chimney. The very smooth surface of the inserts makes it possible to increase the draft of the chimney at the same cross section, which has a favorable effect on the operation of the boiler room equipment. In the case of pipes passing through residential or fire-hazardous premises (attics or attics), chimneys with a double wall with a thermal insulation of the "sandwich" type based on fiberglass or basalt insulation are usually used.
A good alternative to brick is the ceramic chimneys. They have less weight, smooth walls, almost perfect shape of the smoke channel, easier to assemble, do not require such careful insulation as metal pipes, provide absolute safety and are suitable for all types of fuel. In this case, ceramics - a high-quality material, resistant to high temperatures, insensitive to condensing moisture and acid. Ceramic chimneys are suitable for all types of fuel and are characterized by a long service life, in which they have no analogues.

Schiedel UNI - universal chimney system, suitable for all types of fuels and all types of boilers. It has a three-layer construction: high-quality inner ceramic tube, perfectly fitted insulation and a stone shell made of lightweight concrete.

Asbestos cement pipes significantly increase the strength and durability of the entire structure. Sometimes used prefabricated pipes. They, together with prefabricated furnaces, are mounted on cement mortar from separate blocks of heat-resistant concrete directly on site. Prefabricated pipes, depending on the construction of the building, installed as separate risers or built into the walls of the room.
According to the mass application, in terms of the number of variants and the number of company manufacturers, steel modular structures far outstrip other varieties of modular chimneys. They come in three types: single-walled, made of either heat-resistant stainless steel or enamelled non-alloy steel; double-walled (double-circuit, insulated - with a layer of insulation between the outer and inner contours, playing the role of heat insulator); Flexible (in the form of a corrugated hose).

Steel chimneys have many advantages. They are not afraid of the effects of condensate, they can be mounted inside existing chimneys, as well as inside and outside the building as a stand-alone structure. They are produced in fairly wide ranges of dimensions along the internal diameter of the smoke channel and the thickness of the pipe material, which allows selecting the appropriate option for the furnace of any system. They are relatively light, therefore do not require a special foundation, provide a high speed of installation and are highly decorative. Of course, there are also no shortcomings: a tendency to transmit noise, a low self-supporting ability. It is also important that high-quality steel is used in the manufacture of the chimney. However, it is easy to determine when buying - suppliers of quality chimneys usually give a guarantee of 10 years of service life.

Text: Victor Beskrovny
Consultant: Schiedel chimney systems

"Country building", No. 2 (30),2008

The directional movement of combustion products along the smoke pathways is a fundamental factor for effective and safe work  almost all heating devices. There is a movement air masses  in a chimney at a difference of pressures, temperatures and density, between air in a smoke channel and atmosphere. Warm air  in the chimney has a lower density, and strive upward, and its place is taken by cooler air masses.

But there is such a thing as a reverse pull. The manifestation of this effect can be seen immediately and with the naked eye - the smoke from the combustion of the fuel, goes not so much as it is put in the chimney, but moves into the room, thus creating the danger of poisoning the person with combustion products and carbon monoxide. Why is the return draft in the chimney and how to deal with this phenomenon, we will consider in this publication.

The causes of this phenomenon

Reverse traction, as it became clear from the foregoing, there is an effect, and there may be several reasons for this. And above all, the main cause of poor draft in the chimney, and correspondingly the appearance of this effect, is the incorrect design of the heating system and failure to comply with the rules for the use of building materials for the arrangement of the smoke removal system. Among other reasons, the most common are:

• Banal clogging of the chimney.
• Wrong calculation of the cross section of the chimney.
• Non-observance of the height of the smoke removal system.
• Availability of horizontal and narrow sections  in the chimneys.
• The location of the chimney in the zone of "wind".
• Incorrectly organized ventilation system of the room and insufficient supply air.

But it often happens that the phenomenon of reverse traction occurs suddenly, on previously normally operating equipment. This can occur due to unfavorable weather conditions, such as strong wind, fog or high air temperature in the street during the summer. Each of these causes is able to deploy the direction of the combustion products, thereby stopping the normal process of smoke removal from the heating devices.

How to determine the insufficient draft in the chimney system

If the reverse traction is visible to the naked eye, then a bad draft in the chimney should be determined, and it must be done before each start of the heating devices. Several basic methods are used for this.

Tip:
  If suddenly the draft in the chimney is gone, then, first of all, it is necessary to determine the cause of what is happening. Visual inspection of the smoke channel is the first thing to do. Often, you just need to clean the chimney, and the effect of reverse traction in it will disappear.

Reverse draft and ventilation

Many users of stoves and fireplaces, especially after repairs in the house, say that: "There was a return draft in the chimney, what to do about it." All immediately interested in solving the problem, but few people wondered why it was after repair in the room that this phenomenon appeared.

Very often, the effect return traction appears in homes, with installed plastic windows and high-quality doors. Most often, when replacing windows and doors, the owners of premises do not think that after such alterations the normal functioning of the ventilation system ceases.

Strangely enough, the appearance of this effect is directly associated with ventilation, or rather, with its absence. Warm air has a lower density and therefore tends to rise. Warming up in heating device, the air masses rise along the chimney, and the colder air rushes into its place. But in the process of work, it may happen that in a sealed room a region will gradually appear low pressure  and the discharge becomes so strong that it starts pulling fresh air out of the chimney, "overturning the draft," and turning the smoke in the opposite direction. The better the draft in the chimney, the longer there will be no effect of the reverse movement of the combustion products, but without sufficient supply air this process is inevitable.

In order to solve this problem, it is necessary to organize the influx of air masses from the street. This can be solved in several ways:

• Creating an influx of air masses through loosely closed windows, doors or windows.
• Installing the inlet wall valves.
• Mounting inlet valves  on the PVC windows.

Each of these measures will facilitate the penetration of street air masses into the house, preventing the reduction of pressure in the room and the formation of the effect of reverse traction. What a way to choose, it is best to consult a specialist.

Ways to improve the removal of combustion products

Do not forget that even with the best ventilation system, the removal of smoke will be ineffective if the chimneys are blocked or incorrectly designed. With the wrong project, there is only one way to fight, the chimney dismantling and complete rework.

If there is a defect in the chimney ducts that reduces the flue gas discharge, several devices can be used that will improve this process.

Reverse traction is a very dangerous phenomenon, and not only by the appearance of carbon monoxide in a residential building, but also by a spark directed into the room. At the first manifestations of this effect, you should stop using the stove or fireplace, try to determine and eliminate the cause yourself, and if this does not give a positive result, immediately contact the specialists.