When operating a stove, fireplace or boiler, most owners of private houses and cottages note a significant deterioration in the combustion process.

Most often this is caused by a change in traction parameters. To improve the quality characteristics, you should install a chimney draft amplifier, which, due to the simplicity of its design, can be made independently.

Causes of deterioration in traction

First you need to determine the cause of the deterioration in traction. Therefore, first of all, the general condition of the chimney and all associated elements of the system is checked.

This is done very easily. First, the entire heating system is completely turned off, after which the amount of soot in the chimney is measured using a long probe. This value should not exceed 2 mm.

The reasons for insufficient draft in the chimney are conventionally divided into 2 groups: external factors and design features.

Among the design features:

• the use of tees, elbows along the smoke exhaust duct, bypassing obstacles that create aerodynamic resistance;
• incorrect installation and adjustment of the damper;
• incorrect height and diameter of the chimney, which does not meet the requirements of the manufacturers of heating or water heating boilers.

External factors mean:

• placement of the draft outlet below the roof ridge, which under certain conditions can lead to a draft “overturning”;
• the presence of large objects near the chimney, forming an area of ​​​​high pressure or, conversely, vacuum;
• the predominance of strong winds in the region or, on the contrary, calm,

All this can have a significant impact on the traction force and create additional resistance, thereby reducing its level. To avoid this, it is imperative that you take certain steps to increase or stabilize the draft so that your furnace or boiler operates more efficiently.

Methods and devices

For normal functioning of the chimney, the upward flow must have a pressure of about 10-20 Pa. To determine the level of thrust, anemometers are used, and based on their readings and the results of fuel burnout, a decision is made - to increase or decrease thrust.

There are various options for how to bring traction into compliance with standards:

1. chimney extension;
2. use of special devices;
3. use of electric smoke exhausters;
4. traction stabilizers.

Chimney extension

The easiest way to eliminate low draft is to lengthen the chimney pipe. Due to the increase in the difference between the levels of the chimney outlet and the boiler, the difference in pressure of the upward flow also increases. For a chimney, the most suitable height is 5-6 meters, subject to the minimum distance between the vertical section of the chimney and the stove or boiler, and the absence of all kinds of bends, narrowings and deviations of the shafts.

If you have a high roof or there are large objects nearby the house that significantly impair traction, this method makes it possible to achieve the best result. However, with a very high chimney, the draft level can greatly exceed the required value, as a result of which the bulk of the heat will be released into the environment rather than spent on heating the premises. To prevent such a situation, special dampers are used to reduce the volume of exhaust gas.

Deflectors

A deflector is a device that allows you to optimize air flows to enhance draft in a smoke exhaust or air duct pipe. The deflector is translated as a guiding device, reflector. The name, in principle, fully describes its purpose and functionality.

The simpler the design, the greater the efficiency, since the flows reflected from the roof and side winds increase the traction force and suck smoke from the chimney. The deflector, even in heavy winds, prevents the thrust from tipping over, but in calm conditions it is ineffective. The model of the chimney draft amplifier should be selected not only according to the size of the smoke exhaust duct, but also according to the expected wind load.

If you have the desire, a sheet of galvanized iron, a minimal set of tools, available materials and even minor skills in working with metal, you can make such a device yourself.

To make the device you will need:

1. square;
2. roulette;
3. metal scissors or grinder;
4. wooden hammer;
5. riveter;
6. hand electric drill;
7. set of drills;
8. drill-tip screws with a 15 mm press washer;
9. tin or galvanized 0.3-0.5 mm;
10. improvised material for fastenings.

After carrying out the calculations and drawing the contours of the parts onto the metal, we perform the following:

1. cut out all the necessary parts;
2. roll up the nozzle body and fasten the edges using self-tapping screws or rivets;
3. assemble and connect both cones of the device;
4. Before assembling the umbrella, you need to install pins in the lower cone to attach it to the common body, and if the installation will be carried out on legs, then they can be fixed from the outside with rivets.

It is worth remembering that all connections of the draft amplifier in the chimney must be strong, since it can be exposed to strong winds. The video completely shows the process of creating a deflector with your own hands.

Such chimney draft amplifiers not only tolerate flue gases and high temperatures well, but also have corrosion resistance and durability.

Vane

The weather vane is another draft amplifier with a fairly simple design without extending the smoke exhaust pipe, and also dependent on wind strength. However, this device, unlike the one described above, creates virtually no resistance in calm conditions. A small wing is installed on the head, which protects the edge of the chimney from the wind from only one edge.

Thanks to the auxiliary blade, and its placement opposite the place where the weather vane is fixed on the chimney, the device constantly closes the mouth from air flows, which, flowing around it, create a vacuum at the outlet, thereby significantly increasing draft. Manufacturers advise using such devices for the chimneys of wood-burning fireplaces when there is insufficient or unstable draft, in the case of strong winds or when air vortices form above the smoke exhaust channel due to the unfavorable location of the pipe.

Rotary turbines

Rotary turbines are a mechanical device that uses wind energy to increase draft in a chimney. The turbine nozzle, regardless of the direction of the wind, always rotates in one direction, creating a vacuum above the smoke channel, which helps to increase thrust.

The design of such a draft amplifier allows you to protect the chimney from debris, leaves, precipitation and other things getting into it. A special feature of the turbine is that in calm weather it does not work; in the non-heating season, air is removed from the smoke channel, and in the presence of wind, high rarefaction is created and an increase in thrust.

It is not recommended to install such draft amplifiers on the chimneys of coal-fired stoves and wood-burning fireplaces. It is worth considering that the temperature of the flue gases should be no more than 150-250˚C. This device is effective for natural ventilation systems and smoke exhaust pipes of heating boilers operating on gas fuel.

Electric smoke exhausters

In some cases, for example when using wood-burning stoves or fireplaces, it is permissible to install special electric smoke exhausters. These devices are designed for use in conditions of elevated temperatures, the presence of ash, condensate and other combustion products. However, it is strictly forbidden to install them on the flue pipes of solid fuel boilers, in which the gas temperature can reach 650-800˚C.

It often happens that a newly installed stove or gas boiler does not want to burn well. This means that the reason is poor draft - the chimney was built incorrectly. And sometimes the stove, which has always been burning well, begins to act up. This means that the quality of the chimney has deteriorated. You can identify the reasons for this and fix the problem yourself.

Types of chimneys

The chimney is an indispensable part of any stove: Russian, Dutch, contrail, potbelly stove or gas boiler. The chimney removes the mixture of gases resulting from combustion from the room and ensures complete combustion of the fuel.

The correct chimney design, suitable for a specific heating device, helps it perform certain functions. Let's look at the types of chimneys for different heat generators:

Chimney draft

When a chimney is properly designed, built and maintained, it provides good draft.

Definition of traction

The physical meaning of draft is a vacuum that occurs due to the pressure difference in the upper and lower parts of the chimney and ensures the movement of smoke from the heating device into the atmosphere.

Craving can be natural or forced. In the first case, the chimney does not contain any additional technical devices, in the second it is equipped with a fan, deflector, stabilizer, and weather vane.

If the draft is poor, and therefore if combustion is incomplete, the stove, fireplace or gas boiler has low efficiency, smoke may occur in the room, a fire or, worst of all, carbon monoxide poisoning. This gas has almost no odor and immediately causes drowsiness, which is why the number of accidents from burning is so high.

This is why it is so important to be able to determine whether your chimney has enough draft.

Determination of traction force

There are different ways to measure traction force. Conventionally, they can be divided into “scientific” (using special instruments) and folk ones.

Measuring traction force using an anemometer

An anemometer, which was once called a “wind meter,” is a device for measuring the speed of movement of gases. The name comes from the Greek words ἄνεμος (wind) and μετρέω (measurement). Measurements with an anemometer can be made both with the heating device turned on and not working.

This simple device is inexpensive and quite accessible. Anemometers are:

If the anemometer shows a value between 10 and 20 Pascals, then your chimney is normal.

Since draft is caused by the difference in temperatures inside and outside the room, if we measure it in the summer, when the temperature is almost the same everywhere, we will get a lower value than in winter.

Traditional methods for assessing traction force

Since previously there were no specialized instruments, and thrust was somehow measured, several quite acceptable methods have been preserved that do not require any special devices:

Causes of poor and reverse draft

Backdraft is an extreme case of bad draft. Smoke is not only poorly removed, but is thrown into the room due to a change in the pressure difference at the inlet and outlet of the chimney in the opposite direction.

Backdraft

Reverse thrust usually occurs unexpectedly. Frequent causes of its occurrence are:

Video: reverse thrust - what to do

Poor traction

There are several reasons for poor traction:

All these phenomena are permanent, their correction is associated with certain costs. It is more or less easy to solve the problem of a steel chimney being insufficiently high or falling into the wind pressure zone - you need to install a new piece of the pipe on the roof. Other design defects can only be eliminated by using additional mechanisms and devices.

Types of designs to improve traction

To improve draft, devices that are mounted on the chimney are mainly used. Most of them are installed on the head of the pipe, but there are also devices that are built into the very beginning of the smoke channel.

Rotor or rotary turbine

The rotary turbine is mounted on top of the pipe, rotates and creates an air vacuum. It looks like a dome that protects the pipe from rain and pollution. Designed for boilers and conventional ventilation. Minuses:

• effective only in windy weather;
• can be used when the temperature of the gases leaving the chimney is no more than 200 degrees;
• can spontaneously create draft when the heating device is not working;
• not suitable for solid fuel heating appliances.

The rotary turbine creates the necessary vacuum at the outlet of the chimney due to rotation under the influence of wind force

The weather vane also rotates around the chimney and is a most ingenious and effective design. Unlike a rotary turbine, it reacts to the direction of the wind and adopts a position in accordance with the current air flow. The grates trap the wind and create a strong vacuum in the chimney. Using a weather vane allows you to reduce the length of the pipe above the roof and increases the efficiency of the heating device by more than 20%. When used with a gas boiler, the weather vane prevents its spontaneous extinguishing. But making such a device yourself is quite difficult: the design is quite intricate.

The weather vane not only shows the direction of the wind, but also creates the necessary vacuum at the outlet of the chimney and increases draft

Video: chimney weather vane

Fans are used to increase draft in fireplaces and wood-burning stoves. The steel body of this device is protected by a polymer coating, so it is able to work in an environment with aggressive combustion products. The grille protects the air duct from debris. The fan has a single-phase electric motor, removed from the zone of hot air movement. This is a high-tech device with built-in temperature and air flow sensors, which themselves regulate the speed of rotation of the impeller, creating the thrust required at the moment. The work is fully optimized and automated. The big disadvantage is the high cost. It is impossible to do it yourself.

The electric fan operates in automatic mode: it turns on and off based on signals from special sensors

Stabilizer

The draft stabilizer is built in between the firebox and the chimney. This is a valve that, when the draft increases too much, allows air from the room into the chimney, due to which the temperature of the gases in the chimney drops and the draft decreases. When the valve closes, the draft increases. The stabilizer can be manual or automatic. Pros:

• low cost;
• ease of installation;
• maintaining a constant temperature in the chimney.

The downside is that it is only suitable for heating appliances with an open pipe: for gas boilers and potbelly stoves. It's difficult to do with your own hands.

The draft stabilizer is a valve that opens or closes depending on the current draft force

Video: how the traction stabilizer works

Deflector

A deflector is also a device attached to the end of the chimney pipe. The name comes from the Latin deflecto - to deflect, and the action is based on Bernoulli's law: air currents flow around the deflector and create a rarefied area above the pipe opening. The stronger the wind outside, the greater the draft inside. Such simple-looking models of deflectors are intelligently designed from an aerodynamic point of view. The deflector is used for solid fuel boilers, stoves and fireplaces. Depending on the model, such products cost from 1000 to 9000 rubles.

• the likelihood of fire extinction due to a sharp increase in draft during strong winds;
• unsuitable for use with gas boilers;
• low efficiency in calm weather.

Plus - this is a relatively simple device, and it can be easily made with your own hands from a sheet of galvanized iron or stainless steel.

There are several types of deflectors. Let's look at them in more detail.

Video: effectiveness of the TsAGI deflector in strong winds

Making a deflector

The simplest version of a deflector such as a Volpert-Grigorovich device is quite easy to make with your own hands.

Required tools and materials

1. Marker or felt-tip pen.
2. Ruler.
3. Iron scissors.
4. Mallet.
5. Wooden beam for stand.
6. Riveting device.
7. Drill, metal drills (or drill-tip screws).
8. Galvanized iron sheet 0.3–0.5 mm thick (aluminum sheet or thin stainless steel is suitable).
9. Metal parts that are available: corner, studs, thick wire and the like.

Size calculation and diagram

Since the quality of the deflector depends on the accuracy of manufacturing, drawing up the correct drawing is the most important step in the entire process. The dimensions were verified by scientists in a wind tunnel, and they must be followed. The parameter to start from is the diameter of the chimney channel D.

The dimensions of all parts of the deflector are set in proportion to its diameter

Table: dimensions of deflector parts relative to its diameter

Instructions for making a deflector with your own hands

The deflector may not be very beautiful, but you will immediately feel its usefulness: the draft will increase by a quarter, the roof will be protected from sparks. The pipe with it can be one and a half to two meters lower.

Video: DIY production of a TsAGI deflector

When installing any traction booster, you will immediately feel the benefits. But a deflector made with your own hands will also create a compelling reason to make you proud of yourself.

Draft is the natural movement of air from a heating unit into the external environment when removing fuel combustion products from the residential area. The process of burning fuel in a furnace depends on its strength: if it is insufficient, the fuel will burn slowly; if the draft is too strong, a significant part of the thermal energy will be released into the atmosphere.

Lack of draft is also dangerous because some of the combustion products can enter the living space, causing serious poisoning among residents, even death. In addition, violation of the chimney exhaust conditions can cause a fire. The temperature of the flame when burning soot is such that even heat-resistant bricks burn out.

Controlling the hood is an indispensable condition for safe, comfortable living in the house.

Poor hood - reasons

Before we talk about the use of forced draft devices for chimneys, let us dwell on the essence of the process, as well as the reasons for the drop in draft in the pipe.

The set of factors influencing the efficiency of chimney exhaust can be divided into three groups:

1. Internal conditions in the house;
   • Conditions for the movement of air flows indoors.
   • Air temperature in the heated zone of a residential building.
   • The total volume of air inside the rooms, which are connected to the combustion chamber of the furnace through the ash pan.
   • The number of other oxygen consumers living in the house - people or animals.

The draft of the chimney can be influenced by side factors that depend on the design of the house, as well as the changes made to it. For example, installing double-glazed windows instead of conventional windows leads to a drop in traction force, since the latter are more airtight and reduce the flow of oxygen from the atmosphere into the house.

1. External factors:
   • Humidity and air temperature.
   • The size of the atmospheric pressure.
   • The activity and strength of rising air currents.
   • The intensity of inversion air currents in the direction from top to bottom.
   • Energy and direction of wind flows.

The combined effect of the above factors leads to constant changes in chimney draft; this process must be constantly monitored to ensure optimal removal of combustion products from stoves, fireplaces and other heating units.

The influence of the factors in the first section can be conditionally controllable when it does not concern a ready-made chimney. The factors indicated in the second section are absolutely independent, but you can easily adapt to them by using them to improve the hood.

The factors of the third section are completely dependent on the person and can be influenced starting from the design stage, and upon receipt of the finished hood, the shortcomings can be eliminated during repairs - installing a round liner inside the pipe, insulating the walls of the chimney, changing its external structure.

Preventing the condition of the chimney

To avoid the need to use means of forced exhaust of a chimney made of heat-resistant material, it is necessary to use preventive means to maintain it in working condition.

Since the main reason for reducing the intensity of flue gas extraction is the reduction in the passage of the pipe by soot accumulated on the walls, we will consider means of combating this phenomenon.

These methods could be:

1. Burning about half a tablespoon of naphthalene in the furnace firebox. Naphthalene vapors decompose soot into loose components, large ones fall inside the firebox and are subsequently removed with the ash, and small ones fly out through the pipe along with the furnace gases. This product cannot be used for smoke removal from a fireplace and for pipes of open hearths - it leaves a characteristic suffocating smell in the rooms.
2. From time to time, burn potato peelings in the firebox. They are pre-dried. Starch vapors loosen the soot deposit and it will fall into the firebox. Pure starch acts similarly, which is fed into a well-lit firebox in the amount of one tablespoon.
3. A good way to remove soot from pipes is walnut shells. It burns at a high temperature, burning off soot deposits on the inner walls. A single dose of shells should be no more than three liters. Frequency of application - as accumulation occurs.
4. Aspen firewood has a similar effect on soot. One or two logs are burned at the end of the last stack of firewood. They burn at high temperatures.

The frequency of use of high-temperature products should be regular, at least twice a week, so that soot does not have time to accumulate. Otherwise, you can cause a serious fire, since the soot burns and releases a very large amount of heat.

In addition to those listed, there are many anti-soot agents on the market for both chemical and thermal decomposition of soot. The use of preventive measures can eliminate the need for forced measures to improve the exhaust hood on the chimney.

Forced exhaust by additional means

The need to install additional means of forced exhaust may arise for natural reasons, for example, trees have grown on the site, which has changed the direction or intensity of wind flows.

Watch the video

You can, of course, rebuild the house or redo the chimneys, but this path is very expensive and labor-intensive. It is easier and cheaper to use forced ventilation devices. To improve the hood, the following additional devices are used.

Weather vanes or wind vanes for forced draft

This is a device to protect the chimney from wind. Its principle of operation is that, like any weather vane, it turns in the wind, protecting the head of the chimney from the wind flow. Flowing around this device, the wind itself creates a vacuum above the mouth of the chimney, thus creating a forced draft of the chimney.

The heat-resistant material for the manufacture of such a weather vane is usually stainless steel with a thickness of 0.5 millimeters. Rotation around the axis occurs on closed type support bearings that do not require maintenance. There is no condensation and no soot deposits on the device body.

However, it requires maintenance to clear the ice. The disadvantages of the design include unstable operation in strong winds. Under normal conditions, the vane fan operates steadily and efficiently, creating forced draft inside the chimney.

Rotary turbines for forced draft

These are mechanical devices installed on the chimney and use wind energy to produce rotation. Produced by industry under the name Turbovent, Turbomax and others. The direction of rotation does not depend on the direction of the wind. Thanks to the design - a ball formed by a system of petals, the turbine rotor reliably protects the chimney outlet from contamination by debris and leaves, as well as from nesting birds during breaks in the heating season.

The disadvantage of rotary turbines is that they do not operate in calm weather and continue to rotate when there is no need for it - during the non-heating period. Often used for ventilation devices.

Smoke exhausters or smoke fans

These devices are heat-resistant fans installed in the chimney duct to forcefully increase draft. A smoke exhaust fan should not be confused with fireplace fans, which are designed to increase draft in a fireplace or hearth and are installed in a room to supply air to the firebox. Fireplace units are designed to distribute heated air evenly in a room.

The smoke fan is a 220-volt electric motor with an impeller. It is designed to create additional draft forcibly inside smoke channels from a fireplace with a reduced cross-section.

Now there are new models of smoke exhausters in combination with a turbovent. In such a unit, it works in the absence of wind, and when the wind rises again, the smoke exhauster turns off. When the wind speed is insufficient or absent, the fan turns on and creates the necessary draft forcibly.

High-temperature chimney fans can easily withstand heating of furnace gases up to a temperature of 600 degrees.

Deflectors

The chimney deflector is a device that operates using the laws of aerodynamics. When air flows around the deflector body, a vacuum of air is created above the mouth of the chimney, due to which the exhaust is forcibly enhanced.

What is simple is perfect. This statement applies entirely to deflectors. Side horizontal wind and air flow reflected from the roof surface increase the draft of the smoke channel. Deflectors prevent the draft from tipping over due to strong winds, acting as a smoke exhauster for the chimney, but in calm weather they do not work.

Initially, deflectors were developed for ventilation systems, but then they began to be successfully used as draft amplifiers in chimney hoods. Stainless steel products resist corrosion and successfully withstand high temperatures of furnace gases.

In the absence of wind, the deflectors act as caps, reducing the chimney draft.

Umbrellas, chimneys and hoods for forced exhaust

Smoke umbrellas, caps with skirts made of debris mesh, fungi and other superstructures over chimneys are the subject of creativity of blacksmiths and tinsmiths. Of course, they successfully cope with the protective functions of the chimney, preventing clogging with debris. But any of such devices becomes an obstacle to the exit of hot gases from the chimney and, under certain conditions, especially in calm weather, they reduce the amount of draft and can be one of the reasons for its overturning.

How to make forced exhaust yourself

Most weather vanes and deflectors can be made independently using sheet steel and ordinary fasteners. The calculation procedure for linking to pipe sizes and drawings of these products are abundantly presented on the Internet. To make it yourself, you do not need any special tools or devices, and an average level of plumbing skills is sufficient.

Watch the video

From the above, we can draw an unambiguous conclusion: not every device is suitable for improving draft in a chimney. When deciding on a method to improve traction, you must adhere to the following rules.

Inspect the chimney to determine the causes of insufficient draft. These could be:

1. Clogging of the chimney walls with a large amount of soot.
It is precisely this circumstance that can worsen draft up to the point of complete obstruction of the chimney of a gas boiler. The reason may be the use of firewood from resinous wood for heating, waste from furniture production (plywood, chipboard, fiberboard and the like). Cold chimney due to lack of pipe insulation.

2. Excessive number of chimney turns (one turn and no more than two bends are allowed). You may need to take it outside and install a wall-mounted version. It is also permissible to use a chimney fan.

3. Incorrect elevation of the head above the roof ridge, as a result of which the draft is “pinched” by air currents.

4. Chimney height. The distance from the firebox to the upper end should not be less than 5 meters.

5. There are no trees near the house to block the flow of wind.

Only after making sure that there are no such obstacles can you decide to install a device to create forced draft.

The draft in the boiler chimney can be improved by installing a round liner inside a square or rectangular pipe. Such products are produced purposefully and can be purchased on the construction market. If the resulting cross-section is not enough for good draft, you can install a duct exhaust fan inside for a round chimney of suitable diameter.

It is not advisable to use deflectors as a smoke exhaust for a stove chimney if the climate has many windless days. At the same time, the weather vanes at least do not interfere with the escape of smoke by natural draft.

Watch the video

For any case, a heat-resistant chimney fan installed in its duct will be effective.

Posts

From time to time, fireplace owners notice a deterioration in the performance of their heating device. Naturally, they don’t know what this is connected with. Experiments with changing fuel usually also lead to nothing. Experts say that the cause of poor fireplace performance is poor draft.

"Classic problems":

1. The pipe diameter is too large or small. The pipe must be the correct size. If its diameter exceeds certain standards, then reverse draft occurs. Bring the fan close to the chimney, if its blades begin to move, it means you have backdraft. A pipe that is too narrow leads to a reduction in thrust to critical levels.
2. Rotating elements and bends in the pipe. The chimney must be straight, otherwise you will have to install a chimney draft amplifier. Extra turns and bends significantly reduce this parameter.
3. Lack of tightness. This problem often occurs in brick fireplaces as a result of poor construction technology. When a small hole appears in the wall, it begins to work on the principle of a black hole, sucking in air due to the pressure difference. The presence of additional air negatively affects the traction force. This is the same as placing a fan to the side of the upward air.

If none of the above problems are similar to yours, then an amplifier will help solve your traction problems.

Smoke draft deflector

Types of amplifiers

Deflectors- These are aerodynamic devices that specialize in deflecting air flows. With their help, you can adjust the traction force to the required parameters. The deflector fan works on a very simple principle: it sucks air from the atmosphere and directs it inside the chimney. The disadvantage of the device is its absolute helplessness during a quiet hike without wind.

The most common and effective deflectors are the designs of Grigorovich and Volpert. Modern improved deflectors are based on their prototypes. The most common designs are: round chimney nozzles (“Woppers”), star-shaped (“Shenards”) and H-shaped (multi-tiered). When choosing a deflector, carefully look at the material from which it is made. It should be stainless steel - a material that is durable and reliable.

Rotary flue turbines

Rotary turbines- these are mechanisms that are placed on top of the chimneys. The principle of operation is similar to a fan, since they use wind energy to increase the pressure inside the pipe. Advantages of rotary turbines: they cover the chimney pipe and prevent the entry of precipitation. The device does not work in calm weather.

The most popular brands: Turbomax, Turbovent and Rotowent. Turbovent products are not suitable for installation on ducts for removing flue gases from furnaces.

It is also necessary to ensure that the temperature of the outgoing gas does not exceed a threshold of 250 degrees (these are standard requirements, which may differ for different models). Rotary pipes are installed for gas heating boilers.

Chimney weather vanes

Chimney weather vanes- This is a device for protecting the chimney on the leeward side. The model is characterized by good resistance to the negative effects of precipitation, a long service life and the presence of protective mechanisms for smoke exhaust. During the operation of weather vanes, one drawback was noted: they cannot cope with strong winds, and weather vanes also require careful maintenance - regular lubrication (especially in winter) and cleaning of soot and flue gases.

Smoke weather vane Duck and Dog – video review

The weather vane fan works on the principle of a stabilizer: it reduces the effect of strong wind on the draft in the chimney or enhances it in the absence of movement of gas masses in the atmosphere. The type of device in question is perfect for wood-burning fireplaces.

Chimney smoke exhausters

Smoke exhausters is an electric heat-resistant fan for smoke exhaust. It is recommended to install these devices for adjusting the traction force only for narrow pipes. For its operation, access to an electrical network with a power of 220 V is required. Modern smoke exhausters have several upgrades, thanks to which the problems of reverse and weak draft are solved. The electric mechanism has no drawbacks; it works perfectly in calm and windy weather.

Caps and umbrellas- These are decorative elements for the chimney that do not solve the problem of weak draft. After their installation, owners of heating devices noted additional problems: the formation of condensation on the surface of hoods and umbrellas, as a result of which the fan of the above devices quickly became unusable.

Thus, a wide variety of mechanisms for increasing traction cope well with the problem posed. The above models, in addition to smoke exhausters, have one drawback in common: they are too dependent on weather conditions. Therefore, to increase draft in the chimney, it is better to choose an electric smoke exhauster.

Manufacturing of devices to enhance traction

Making devices to enhance traction with your own hands

It’s good when a person has money and can buy himself several nozzles for the chimney, but what to do when there is no opportunity to get a modern mechanism, however, there are tools and several metal plates in the garage? The answer is simple - design it yourself.

Among the tools you will need: a square, metal scissors, a tape measure, a hammer, pliers, a drill, self-tapping screws (15 mm), a galvanized sheet of metal with a thickness of 0.3-0.5 mm and several improvised materials for fastening and an old fan, more precisely, its blades.

Draw a layout of devices to enhance traction

The first thing you need to do is draw a layout of the future device. Circuit drawings can be found on the Internet. After accurately transferring the dimensions onto a galvanized steel sheet, the following actions are performed in strict sequence:

1. Using a grinder or metal scissors, the main parts of the weather vane are cut out;
2. The constituent elements of the weather vane are assembled according to a diagram in strict sequence and secured with rivets or self-tapping screws;
3. Next, you need to secure both cones (in most schemes this point is skipped because the “masters” believe that it can be ignored). In fact, it is highly recommended not to ignore this point, so as not to provoke ruptures of the cones in strong winds;
4. Now all that remains is to attach the fasteners and the fan to the device. Using fasteners, the device is attached to the base of the chimney. The fan also performs the function of increasing traction.

Wind vane

At this stage, the manufacture of the weather vane is considered complete; all that remains is to attach it to the chimney. It is fastened with self-tapping screws or rivets. Remember that this device requires regular maintenance: from time to time it must be cleaned of soot and accumulated condensation if you do not want the accumulated moisture to fall on the waterproofing layer inside the pipe.

Video: Draft amplifier for stove, boiler and chimney

The key factor influencing the efficiency of the boiler is the draft in the flue duct. When it increases, for solid fuel boilers, the combustion of coal or firewood improves, which increases the efficiency of the installation. For gas boilers, the draft must be strictly stabilized to ensure normal combustion and not blow out the flame. When constructing a chimney, especially when it is not possible to use the most optimal route, it becomes necessary to use a chimney draft amplifier. What can affect cravings and how to implement this, we will consider further.

Installing a solid, liquid or gaseous fuel boiler, stove or fireplace necessarily involves installing a chimney exhaust system. The main parameters of the chimney are the draft level and the volume of exhaust gases. Structurally, it is an insulated channel, a pipe laid from the exit of the firebox to the external environment outside the building. The draft is created due to the difference in pressure at the chimney inlet and outlet, which is caused by the temperature difference and the difference in levels between the inlet and outlet. The higher the chimney, the stronger the draft. The thicker the channel, the greater the volume of gases it can remove from the boiler.

However, there are a number of reasons why the draft in the chimney may decrease, or even “overturn” when air is sucked from outside into the chimney and combustion products enter directly into the room.

Causes of poor traction

Conventionally, two large groups can be distinguished: the design features of the chimney and external factors that affect the level of draft.

Design features include such points as:

• Using elbows and tees along the chimney, avoiding obstacles that create aerodynamic resistance.
• Using the wrong chimney section and height, different from the boiler manufacturer's requirements.
• Incorrect installation of the damper (damper) and its adjustment
• Availability of chimney head, umbrellas, spark arrester, etc.

External factors mean:

• The location of the chimney outlet is below the roof ridge, which, in a certain wind direction, can cause the draft to “overturn.”
• The presence of large objects near a chimney, a neighboring building or other structure that creates a vacuum zone or, conversely, increased pressure in the chimney area.
• The predominance of strong winds or, conversely, the dominance of calm weather.

All of this affects the level of traction, often creating additional resistance and reducing it. In any case, you will need to find an adequate way to increase the draft or stabilize it in order to ensure the most efficient operation of the boiler or furnace.

Methods and devices

During normal operation of the chimney, the pressure of the upward flow should be in the range of 10-20 Pa, which corresponds to the optimal flow of exhaust gases from the combustion chamber. To find out the real state of affairs, anemometers are used that can show the level of thrust. Based on the instrument readings and the result of fuel burning, you can accurately say whether it is necessary to increase or decrease thrust, or use stabilizers that will automatically maintain the ideal air flow rate in the channel.

There are many ways to increase draft or bring it into compliance with the standards and requirements of the boiler manufacturer:

• Increasing the height of the chimney;
• The use of deflectors, weather vanes, rotary turbines as a chimney head;
• The use of smoke exhausters powered by electricity;
• Traction stabilizers.

Increasing the chimney height

The simplest and most often reliable way to cope with a low draft level is to increase the height of the chimney. As a result of an increase in the level difference between the boiler and the chimney outlet, the pressure difference also increases, the upward flow of hot gases significantly increases the draft. The optimal height of the chimney is 5-6 meters, provided there is a minimum distance between the boiler and the vertical part of the channel and the absence of various deviations, bends and thinning of the channel.

Calculation of the height of the chimney, depending on the location from the roof ridge

In the case of various external factors, such as a high roof profile, ridge, nearby buildings or other objects that worsen the situation, this gives a better result. However, if the chimney is too high, the draft can significantly exceed the required threshold, causing most of the heat to simply go outside, heating the environment, and not the working fluid in the heating system. The fuel will burn worse. To prevent this effect, dampers or draft stabilizers are used, which can be used to reduce the volume of exhaust gases.

Deflectors

Special devices attached to the chimney head. Their shape and design are selected so that the air flows directly near the chimney outlet do not interfere with the exit of gases, but, on the contrary, contribute to this. The action of the deflector is based on Bernoulli's law. If there are air currents, they flow around the main part of the deflector and create a vacuum in the area directly above the chimney exit. An excellent option for use in conjunction with solid fuel boilers, where increased draft ensures proper burning of coal and briquettes.

The deflector cannot be installed with gas boilers. Strong wind can significantly increase draft, as a result of which the burner flame can simply go out.

The effectiveness of deflectors directly depends on the presence of wind, so they are virtually useless in calm conditions and even create additional resistance.

Vane

Another means of increasing draft without increasing the height of the chimney and also depending on the wind. However, unlike a deflector, a weather vane does not actually create resistance in calm weather. Its design is extremely simple. A small wing is attached to the chimney outlet, covering the head from the wind on one side.

With the help of an additional blade and its location on the other side of the chimney axis from the weather vane mount, it is always turned so as to close the mouth from air flows. They flow around it and create a vacuum at the outlet, increasing thrust.

Reviews from owners of this device indicate its unsuitability due to jamming of the rotating part by smoke deposits or freezing of precipitation.

Rotary turbines

A special design consisting of rounded blades located at a certain angle to the axis of rotation. The turbine, under the influence of exhaust gases and external flows, always rotates in the same direction, maintaining and increasing thrust. The advantages and disadvantages are the same as for deflectors.

Electric smoke exhausters

In some situations, for example, for use with wood-burning stoves or fireplaces, it is possible to install special electric duct exhaust fans. They are designed to operate in environments with elevated temperatures and the presence of ash, condensate and other combustion products. However, it is unacceptable to install them on the chimney of a boiler operating on solid fuel; the temperature of the gases in it can reach 650-800°C.

Such smoke exhausters are capable of automating the operation of the chimney. A special temperature and flow sensor regulate the activity of the electric drive, thereby always maintaining optimal traction in the system.

Traction stabilizers

A whole class of devices for automatic regulation of gas pressure. They are primarily designed to work in systems with known good or increased traction. Their task is to regulate the volume of exhaust gases depending on the efficiency of the main chimney. In fact, they replace ineffective dampers that constantly require attention and manual adjustment.

The principle of operation of stabilizers is based on mixing cold air from the room into the gases leaving the furnace. This allows you to reduce the temperature of the total mixture, which enters the vertical channel and reduces the flow rate.

Structurally, this can be a device assembled on the basis of a chimney tee, which has an intake valve on the branch. The movable curtain, mounted on a free axis, opens only when the pressure in the system is exceeded, which is regulated using a counterweight.

How to determine the best option

The choice of a specific solution depends on the structural features of the chimney in each individual case. The use of elements such as deflectors, weather vanes, turbines or smoke exhausters is only relevant in the presence of certain factors, such as windy weather or the impossibility of arranging a full height chimney.

The best solution remains, as always, to increase the height of the chimney and use various stabilizers, which, in combination with increased draft, can ensure optimal operation of the boiler. In this case, the influence of external factors is reduced and all possible obstacles to the creation of a natural flow of combustion products are eliminated.