Calculation of the chimney from the power of the boiler. Calculations when installing a chimney for a wood-burning stove and a domestic boiler

With an independent smoke exhaust structure, it is necessary to accurately calculate the cross-sectional parameters of the chimney, its overall height and the level of air circulation - thrust, which will support the combustion process of the fuel and remove toxic combustion products contained in the smoke into the atmosphere. Such calculations are quite complicated, but important for ensuring the efficient and uninterrupted operation of the thermal unit and the safety of residents.

For the normal functioning of heating appliances that generate heat by burning fuel, a chimney is required.

The smoke-removing design provides an influx of oxygen, without which neither gas nor solid or liquid fuel burns. In addition, smoke containing combustion products is removed through the chimney, which is the key to the safety of the heating system - after all, smoke in the premises is deadly for humans. This gas exchange is called thrust.

Internal combustion boilers are equipped with coaxial chimneys, which create draft forcibly, removing smoke through one pipe and sucking in fresh air through another. Wood stoves and most domestic boilers run on natural draft, which is formed due to the difference in temperature and pressure in the heating device and at the chimney outlet.

The principle of operation of the chimney is simple:

• the gases released during the combustion of fuel have a high temperature, low density and high pressure, and they become cramped inside the heater;
• smoke goes where there are no obstacles for it, that is, it moves in the direction where the pressure is lower, trying to fill the relatively free space, in addition, due to the low density, gases tend upwards;
• if the chimney is arranged correctly, then the cold air at the outlet of the pipe has low pressure and is not an obstacle to the exit of hot smoke;
• since the low pressure area is above the boiler, the smoke goes along the most convenient path - up the chimney to the street.

What are calculations for?

Natural air exchange, in which combustion products are removed into the atmosphere, occurs only if the flue structure has the correct shape and size.

If there are obstacles - turns, corners, sections of the smoke channel with low throughput - the smoke can go in another direction, where nothing will interfere with its spread. With a small pipe height, the temperature difference will not be sufficient to form a thrust, or a wind backwater will appear, which will prevent the smoke from leaving the pipe, practically driving it back.

Note! Defects in the chimney device will lead to the fact that the draft will either be insufficient for the normal operation of the heating device, or a reverse draft will appear and the combustion products of the fuel will enter the premises, which can cause poisoning or a fire.

However, it cannot be said about the dimensions of the chimney that the larger the better. Too long or too wide a chimney will increase the cost of building a chimney. A furnace or boiler with such a chimney will work for wear in conditions of excessive draft, burning fuel faster than it is necessary to warm up the premises. The heat received during combustion will partially fly away into the pipe, which will increase heating costs.

Therefore, in order for the thermal unit to work efficiently and not break down, it is important to accurately calculate the main parameters of the chimney, which will provide the optimal level of traction.

How to calculate the parameters for the chimney

For the construction of a smoke exhaust structure, it is imperative to carry out calculations:

• overall height and height relative to the roof,
• internal diameter of the chimney,
• generated traction.

All these parameters are interconnected. The geometric dimensions of the chimney must be calculated to draw up its project, and the amount of thrust - to determine the operability of the chimney in normal weather conditions for the area.

Calculation of inner diameter

The main regulatory requirement for the size of the chimney pipe is its compliance with the outlet pipe of the heat appliance.

Note! For factory-made heat generating units, it is enough to choose a pipe that has the same cross section as that of the outlet pipe, or a slightly larger size. The fulfillment of this condition will provide the necessary throughput of the chimney.

For a wood-burning stove or domestic boiler that does not have a factory outlet, it is necessary to calculate the parameters of the internal section of the chimney for which the chimney will have the required throughput.

To calculate the diameter of a round pipe or the width and length of a rectangular one, you need to find the area of ​​​​its internal section. The calculation is carried out in several stages.

First, the volumetric output of flue gases per unit time (Vg) is calculated:

Vg=Mt*Vt*(tg+273)÷273,

• where Mt is the fuel consumption per unit of time specified in the accompanying documentation of the heater,
• Vt is the smoke emission coefficient of the fuel used,
• and tg is the flue gas temperature at the chimney inlet, usually indicated in the documentation for the heater and equal to 120-150ºС.

The smoke emission coefficient varies for different fuels:

To calculate the cross-sectional area (S), it is enough to divide the obtained value (Vg) by the smoke removal rate (v):

S=Vg÷v.

The optimal speed is considered to be 1-2 m / s. At this speed, soot and condensate do not have time to settle on the pipe walls, but the heat remains in the room, and is not drawn out into the street.

Note! For accurate calculations, it is important to reduce all quantities to a single time parameter. If the speed for the calculation is used in m / s, then the fuel consumption must be converted to kg / s.

For example, if the standard flow rate for a wood-burning stove is 8 kg/h, then when converting, this value must be divided by 3600. Thus, the flow rate will be 0.0022 kg/s.

For a round pipe, the diameter (D) is calculated from the formula for the area of ​​a circle:

D=2√S÷3.14.

For a square, the width (a) is calculated from the formula for the area of ​​a square:

a≥√S.

For a rectangular section, the width (a) and length (b) are selected so that their product is greater than or equal to S:

S≥a*b.

Determining the height of the chimney

In order to create a sufficient difference in pressure and temperature in the boiler and outside, the minimum required height of the chimney pipe must be 5 meters. But in addition to the minimum value, it is necessary to calculate the height of the outlet above the roof.

These calculations take into account the type of roof, the location of the chimney in relation to the roof ridge and the presence of closely spaced buildings or other tall objects.

Note! When designing a chimney, it is necessary to take into account the location of the fasteners. Every 2 m of height, the pipe is fixed to the walls and ceilings, if the chimney rises more than 1.2 m above the roof, extensions are used for additional fixation.

Thrust calculation

To check the operability of the chimney, which will be erected in accordance with the calculations made for the height and internal section of the pipe, an additional draft calculation is carried out.

Draft, that is, the pressure difference at the inlet and outlet of the chimney (P) is calculated by the formula:

ΔP=hd*(ρv-ρg),

where hd is the height of the chimney above the heater,

c - air density in the street,

d is the smoke density.

The height of the chimney has already been calculated, but the density of air and flue gases will need to be calculated. Depending on weather conditions, the air density indicator changes.

ρin=ρin*273÷tin,

where n=1.29 kg/cu.m. is the air density under normal conditions,

and tv is the ambient temperature.

It is important! To calculate thrust, the most unfavorable climatic conditions in the region are taken - the warm season. For calculations, the temperature in Kelvin is used, so we add 273 to the temperature in degrees Celsius.

Flue gas density is calculated using a similar formula, based on the average flue gas temperature in the pipe (tg):

ρg=ρn*273÷tg.

Δtg=(tg+td),

where tg is the temperature of the gases at the outlet of the heater, indicated in the accompanying documentation,

and td is the temperature of the smoke at the exit from the pipe.

But the temperature of the flue gases emitted by the chimney into the atmosphere requires additional calculations and depends on the power of the thermal device (Q) and the height of the chimney (hd):

td=tg-hd*V*√1000÷Q,

where B is the heat transfer coefficient of the chimney, depending on the material from which the chimney is made and the level of its thermal insulation.

If, after carrying out all the calculations, the thrust level turned out to be in the range of 10-20 Pa, then the designed chimney will cope with its task and ensure uninterrupted operation of the thermal unit. Otherwise, it will be necessary to increase the height of the chimney or equip the head with a deflector or a smoke exhauster to create artificial draft.

Note! Thrust calculations require accuracy, so all intermediate calculations must be recorded so that they can be verified. To eliminate a possible error in the calculations, you can use an online calculator or contact a specialist.

Features of calculating the parameters of the chimney for domestic boilers

Factory-made thermal appliances usually do not require serious chimney calculations - the main parameters are indicated in the accompanying documentation. A distinctive feature of the calculations for household boilers is their simplicity.

• The height is determined according to general rules, taking into account the peculiarities of the location of the smoke exhaust structure relative to the roof of the house and nearby buildings.
• The diameter of the internal section of the chimney is chosen in accordance with the power of the heat generating unit, without taking into account either the type of fuel or the volume of gases emitted. Since factory devices are produced according to manufacturing standards, all parameters have long been calculated and collected in a table.

Thrust is a separate process of an aerodynamic nature, in which combustion products move from an area with an increased pressure level to an area with a lower one. In this regard, the chimney draft is the most important parameter when calculating the entire heating system of a private house. If the calculation is incorrect, a reverse draft occurs, in which the combustion products are not removed, but enter the living room. On what factors does the level of traction depend? How to correctly calculate the parameter? In what ways can traction be increased in case of insufficiency? Read on.

What is traction

The process of formation of natural draft in the chimney can be described from the point of view of such a science as physics as follows:

1. gases heated by combustion in a furnace (boiler) of firewood or their analogues have a temperature of about 1000ºС;
2. according to the laws of physics, heated air always rises;
3. rising through a special pipe (at a speed of approximately 2 m / s), gases create an area of ​​\u200b\u200blow pressure;
4. the pressure is stabilized due to the influx of fresh air, which enters the furnace (boiler) through special blowers, grates and other similar equipment.

Based on the physical processes of the formation of natural draft in a pipe, it is possible to determine a list of factors affecting its magnitude. These include:

• chimney length. In accordance with current regulations, the length of the chimney duct should not be less than 5 m. The optimal length can be determined based on the location of the chimney on the roof;

• the material from which it is made. To facilitate the passage of gases as much as possible, it is recommended to make a chimney from materials with a smooth inner surface. And if this rule is not observed, then resort to periodic cleaning of the channel to remove soot and other deposits;
• presence/absence of insulation. If the smoke channel is not insulated from the outside, then when the gases cool, a large amount of condensate will form, which negatively affects the level of thrust;

The chimney can only be insulated with non-combustible materials.

• pipe section. It is from the correctly selected diameter of the chimney that the level of thrust depends.

The draft in the smoke duct is also determined by natural factors:

• temperature and humidity inside the dwelling;
• weather conditions (wind, precipitation, low temperature, and so on);
• the number of residents;
• frequency of ventilation and so on.

How to check the presence / absence of traction? You can check the level of thrust in the pipe using a lit match, candle or paper.

Thrust calculation

So, the draft calculation is the calculation of the section of the chimney for a gas boiler, fireplace, stove or other heating equipment. How to calculate the cross section? To do this, you need to define:

1. the volume of gas that will pass through the chimney in 1 hour;
2. cross-sectional area of ​​the chimney;
3. section diameter.

Gas Volume Calculation

To calculate the volume of gas passing through the flue channel, the following formula is used:

V = B x V1 x (1 + T/273) /3600 , where

B is the mass of fuel burned in 1 hour of heating equipment operation;

V1 - correction factor, which depends on the type of fuel used for heating;

T is the gas temperature determined at the outlet of the chimney.

Indicators V1 and T can be obtained from the table available in GOST 2127 - 47.

Section area calculation

After determining the volume of gases passing through the flue channel, you can calculate the size of the pipe section:

S=V/W, where

V is the volume calculated earlier;

W is the speed of gases passing through the smoke channel (this value is constant and equal to 2 m/s).

Diameter determination

The next step is to directly determine the diameter of the chimney. For this, the following formula is used:

D = √4 * S/ π, where

S is the cross-sectional area of ​​the smoke channel;

π is a constant equal to 3.14.

Example

For example, we will calculate according to the indicated formulas with the following parameters:

• in the stove installed in the bath, 10 kg of firewood is burned every hour;
• the temperature of the gases at the outlet of the pipe is 130ºС.

Calculate the volume of gases:

V \u003d 10x10x (1 + 130/273) / 3600 \u003d 0.041 (m³ / h)

Determine the cross section of the chimney pipe:

S = 0.041/02 = 0.0205 (m²)

We find the most suitable pipe diameter for the given parameters:

D \u003d √ 4 * 0.0205 / 3.14 \u003d 0.162 (m)

This means that for the stove used in the example, it is enough to install a chimney with a diameter of 165 - 170 mm.

How to make calculations and install a chimney on your own, look at the video.

How to increase traction in an already mounted channel

The above calculations make it possible to build a chimney with optimal parameters to obtain a normal level of natural draft. But what if there is a reverse thrust? Is it possible to increase the indicator and how to increase traction on your own? There are several ways:

1. cleaning the chimney. When soot and other types of deposits settle, the working diameter of the pipe is significantly reduced, which leads to a decrease in thrust. You can clean up:
   • using a metal brush - brush. To do this, you need to tie the ruff to a strong rope and supplement the structure with a load. Cleaning is done from the roof;

• special means such as log "Chimney sweep";

When using special products, it is necessary to strictly follow the instructions provided on the product packaging or a special insert.

• folk remedies. For example, peel from raw potatoes, aspen firewood, and so on;

1. elimination of design flaws made during the construction of the pipe (elimination of cracks, lengthening or shortening, elimination of excessive bends, insulation, and so on);
2. installation of additional equipment.

As additional equipment to enhance traction, you can use:

• regulator. The device is installed on the pipe and by opening / closing the damper allows you to adjust the traction force in;

• deflector-amplifier. The increase in thrust occurs due to the redirection of air flows formed due to an increase in the diameter of the device;

• vane. The draft stabilizer, as well as the deflector, is installed at the end of the chimney and serves to enhance draft due to the streamlining of air flows. In addition, the weather vane helps to stabilize the level of traction during strong gusts of wind;

• rotary turbine. When exposed to wind, the device begins to rotate, creating a low pressure area around itself, contributing to an increase in thrust.

Unlike other devices, a rotary turbine performs its functions only in the presence of wind. In addition, the device does not protect the chimney from clogging with leaves, small birds and other pollutants.

All additional devices require periodic maintenance: cleaning in the warm season and cleaning from ice in winter. If you do not clean it in a timely manner, then the performance of the device will be minimized and the desired effect will not be achieved.

The efficiency and productivity of the furnace depends on the optimal cross-sectional size and height of the chimney. The rules of SNiP and several calculation options will help you choose the right size for a wood-burning stove in the house.

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Why do you need to know the diameter?

Beginners do not understand how important the cross section of the chimney for the furnace is and why it is so important to correctly calculate not only the internal size, but also the height of the pipe. When developing an individual project for an autonomous heating system for a residential or industrial premises, the level of traction and the performance of the unit depend on the accuracy of the data.

Inexperienced builders can make a pipe with a large or insufficient section. In any such option, the operation of the heater is disrupted, and you are simply throwing money away. For optimal operation of the heating system at home, it is important to conduct an accurate calculation and familiarize yourself with the recommendations of regulatory documents.

Important! Fire safety at home, work productivity, comfortable temperature - the solution to all these issues depends on the correct determination of the size and length of the chimney.

What should be the diameter of the chimney for the furnace?

The size of the chimney can be calculated in several ways. The simplest is to determine the cross section of the chimney depending on the size of the combustion chamber. The consumption of solid fuel is determined by this characteristic, and based on these data, it is possible to determine the volume of exhaust gases.

If you have an open view of the firebox and the chimney is made of a steel round pipe, these values ​​\u200b\u200bshould be in the ratio of 10 to 1. For example, the dimensions of the combustion chamber are 50/40. Such a furnace should be equipped with a chimney with a cross section of 180 mm.

If we make a brick pipe, its internal size should exceed the size of the ash pan door or blower one and a half times. The minimum size of a square cavity for the removal of gases is 140/140 mm.

Payment Methods

Exact method + formula

Calculate the chimney for the stove, not for beginners. It is better to entrust such work to professionals. But if you decide to calculate this parameter yourself, you will need knowledge of basic data and several formulas:

• B is the coefficient of the combustion rate of solid fuel. This value is determined based on the data in table No. 10 of GOST 2127;
• V is the level of the volume of fuel burned. This value is indicated on the tag of the industrial device;
• T - the level of heating of exhaust gases at the point of exit from the chimney. For wood stoves - 1500.

1. The total area of ​​the chimney. It is calculated based on the ratio of the volumes of gases, this value is denoted by "Vr" and the speed of their movement in the pipeline. For a wood-burning household stove, this number is 2 m / s.
2. The diameter of a round pipe is calculated by the formula - d² \u003d (4 * Vr) / (π * W), where W is the speed of gas advance. All calculations are best done on a calculator and carefully enter all the values.

Calculate the optimal amount of thrust

This operation is performed to control the calculation of the optimal height and section of the chimney. Such a calculation can be carried out using 2 formulas. We will give a basic but complex one in this chapter, and we will give a basic, simple formula when performing a trial data calculation:

• C is a constant coefficient equal to 0.034 for wood-burning stoves;
• letter "a" - the value of atmospheric pressure. The value of natural pressure in the chimney - 4 Pa;
• the height of the chimney is indicated by the letter "h".
• Т0 is the average level of atmospheric temperatures;
• Ti - the value of heating of the exhaust gases when they exit the pipe.

An example of calculating the cross section of a chimney

We take as a basis:

• the potbelly stove runs on solid fuel;
• within 60 minutes, up to 10 kg of hardwood firewood burns in the oven;
• fuel moisture level - up to 25%.

Here is the basic formula again:

We carry out the calculation in several stages:

1. We perform the action in brackets - 1 + 150/273. After calculations, we get the number 1.55.
2. We determine the cubic capacity of the outgoing gases - Vr \u003d (10 * 10 * 1.55) / 3600. After calculations, we obtain a volume equal to 0.043 m 3 / sec.
3. The area of ​​the chimney pipe is (4 * 0.043) / 3.14 * 2. The calculation gives a value - 0.027 m 2.
4. We take the square root of the area of ​​the chimney and calculate its diameter. It is equal to 165 mm.

Now we determine the thrust value using a simple formula:

1. According to the power calculation formula, we calculate this value - 10 * 3300 * 1.16. this value is - 32.28 kW.
2. We calculate the level of heat loss per meter of pipe. 0.34*0.196=1.730.
3. The level of gas heating at the exit from the pipe. 150-(1.73*3)=144.80.
4. Atmospheric pressure of the gas in the chimney. 3*(1.2932-0.8452)=1.34 m/sec.

Important! Using the data of your furnace, you can independently perform the calculation, but for safety, it is better to consult with specialists. The safety of your home and the efficiency of the operation of heating devices depend on the correct calculation.

Swedish calculation method

The size of the chimney for the stove can also be done using this method, but the main purpose of the Swedish method is to calculate the chimneys of fireplaces with an open firebox.

In this method, the size of the combustion chamber and the volume of air in it are not used for calculation. To determine the correctness of the calculation, a graph is used:

Here it is important to match the ratio of the area of ​​​​the combustion chamber ("F") and the opening of the flue pipe ("f"). For example:

• furnace dimensions 770/350 mm. We calculate the area of ​​​​the compartment - 7.7 * 3.5 \u003d 26.95 cm 2;
• chimney size 260/130 mm, pipe area - 2.6 * 1.3 = 3.38 m 2;
• calculate the ratio. (338/2695)*100=12.5%.
• look at the bottom of the table the value 12.5 and see that the calculation of the length and diameter is correct. For our furnace it is necessary to build a chimney, 5 m high.

Let's look at another calculation example:

• firebox 800/500 mm, its area - 40 cm 2;
• the cross section of the chimney is 200/200 mm, the area is 4 cm 2;
• we calculate the ratio (400/4000)*100=10%.
• according to the table we determine the length of the chimney. In our case, for a round sandwich pipe, it should be 7 m.

What to do if the cross section of the chimney is square?

Cylindrical chimneys, especially after the appearance of sandwich pipes, are the most common types of devices. But when building a brick oven, you have to lay out a square or rectangular shape.

In such chimneys, turbulences are formed that prevent the normal passage of exhaust gases and reduce draft. But for wood-burning stoves or fireplaces, rectangular chimneys remain the most sought-after shape. In such devices, an increased level of exhaust gas extraction is not required.

The calculation of the chimney for a wood-burning stove with a square or rectangular section is made taking into account the ratio of the dimensions of the pipe to the size of the blower hole on the stove. This proportion is 1 / 1.5, where 1 is the internal section of the pipeline, and 1.5 is the dimensions of the blower or ash pan.

What should be the height of the chimney pipe for the stove?

The calculation of this parameter allows you to avoid the occurrence of reverse thrust and other possible troubles. This issue is regulated by the rules of SNiP and other documents.

Why is this parameter needed?

In order to understand the importance of this factor, let's take a closer look at several physical laws and the consequences of improperly made chimneys. As heated gases pass, the temperature drops, but warm air or gases always rise.

At the outlet of the pipe, the temperature decreases even more. Exhaust gases located in a pipeline with a reliable layer of thermal insulation have a high temperature and a column of heated smoke, rising upwards, increases draft in the furnace.

Let's analyze the situation - we reduce the internal section of the pipe and increase the height of the pipe above the roof ridge. If you think that the volume of heated gas increases, the cooling time of the smoke increases and the thrust increases - this statement is only half true. Traction will be excellent, even with a large excess. Firewood will burn quickly and the cost of buying fuel will increase.

An excessive increase in the height of the chimney can cause an increase in aerodynamic turbulence and a decrease in the draft level. This is fraught with the occurrence of reverse thrust and the release of smoke into the living quarters.

SNiP requirements

The length of exhaust gas exhaust pipelines is regulated by the requirements of SNiP 2.04.05. the rules prescribe to observe several basic installation rules:

• the minimum distance from the grate in the furnace to the protective canopy on the roof is 5000 mm. Height above the flat roof covering level 500 mm;
• the height of the pipe above the roof slope or ridge should be as recommended. We will talk about this in a separate chapter;
• if there are buildings on a flat roof, the pipe should be higher. In this case, with a high pipe height, it is unfastened with wire or cable extensions;
• if the building is equipped with a ventilation system, their height should not exceed the cap of the flue gas outlet pipe.

Self-calculation technique

How to independently calculate the height of the smoke channel, for this you will need to perform the calculation according to the formula:

• "A" - climatic and weather conditions in the region. For the north, this coefficient is 160. You can find the value in other areas on the Internet;
• "Mi" - the mass of gases passing through the chimney in a certain time. This value can be found in the documentation of your heater;
• "F" is the settling time of ash and other waste on the walls of the chimney. For wood-burning stoves, the coefficient is 25, for electrical units - 1;
• "Spdki", "Sfi" - the level of concentration of substances in the exhaust gas;
• "V" - the level of the volume of exhaust gases;
• "T" - the temperature difference between the air entering from the atmosphere and the exhaust gases.

It does not make sense to give a trial calculation - the coefficients and other values ​​\u200b\u200bare not suitable for your unit, and extracting square roots will require you to download an engineering calculator.

Table "Height of the chimney above the ridge"

The table of the height of the chimney above the roof structure will help determine the dimensions of the pipes without carrying out complex calculations. First, we will analyze the selection of the length of the pipe for flat roofs.

Conclusion

By performing a calculation or determining the size according to the table, you will not only protect your home from fires, but also significantly save on fuel. The main thing is to carefully and responsibly carry out the installation and comfort and coziness in the house will be provided.

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In order to install the chimney correctly, it is necessary to carry out a number of design works, which include both the calculation of the chimney and the choice of material for its manufacture. And if for industrial-scale work it would be best to attract professionals, then in private construction you can limit yourself to it. Below we will consider how to calculate the chimney.

Types of chimneys

The purpose of the chimney is to remove combustion products and smoke from the stove or any other heating device outside the room. The draft in any household chimney is formed naturally and does not involve the use of any additional devices.

Modern chimneys can be made:

• From brick. Since such a structure has a significant weight, it is necessary to build a solid foundation for it.

Advice! Experts advise adding lime to the composition of the mortar used for brickwork, which will avoid the formation of condensate, which has a detrimental effect on the walls of the building.

• From sandwich pipes, which are made of two layers of metal with a heater laid between them. The most commonly used material for the manufacture of such pipes is stainless steel. In most cases, basalt acts as a heater.
• from polymeric materials. Such pipes should not be exposed to excessively high temperatures, therefore such chimneys can be used for gas water heaters and small boiler rooms. At the same time, polymer pipes are very durable, easy to install and have a low price.
• From ceramics. Such pipes are characterized by high strength, but they cost a lot. Therefore, they are most often used for arranging industrial-type chimneys. Due to their significant weight, such structures, like brick ones, require laying the foundation.

Important! In some situations, combinations of materials intended for the manufacture of chimneys are possible. For example, a polymer or metal chimney can be lined with bricks.

How is a chimney calculated

In order to calculate the dimensions of the chimneys, it is necessary to navigate in the parameters of the heater. The main dimensions of chimneys are the cross-sectional diameter and height. This data is in the accompanying documentation of the equipment.

How to calculate height

The performance of heating devices directly depends on this parameter, therefore, calculating the height of the chimney is very important. According to the SNiP documentation, the minimum height of the chimney is 5 meters. If the pipe is less than this value, then the necessary natural draft will not occur in it. However, a too high chimney is also bad, because in this case, the smoke will slowly pass through the system and cool down to reduce the draft.

A serious calculation of chimneys is used in industrial construction. It uses a very complex system of calculations. In private construction, the requirements are usually much less, and the calculation of the height of the chimney involves following the following rules:

• From the base to the highest point, the length must exceed 5 meters.
• When exiting to a flat roof, the chimney must rise above it by at least 50 cm.
• If the chimney is erected on a pitched roof with a distance of more than three meters from the roof ridge, then its height is calculated as follows: the line connecting the roof ridge to the chimney and the horizontal line of the roof ridge must be located at an angle of 10 degrees to each other.

The method of aerodynamic calculation of chimneys was developed to determine the resistance and selection of chimneys. A good aerodynamic calculation should take into account possible pressure drops in sections of the gas-air paths, also taking into account the resistance that occurs in a certain section.

How is the section of the chimney calculated

In order to calculate the draft of a chimney, it is necessary to first determine its diameter. In order not to carry out complex calculations, you can use the following recommendations of specialists:

• If the power of the heating equipment does not exceed 3.5 kW, then a chimney with dimensions of 0.14 by 0.14 meters will be enough for you.
• If the heating boiler has a power in the range of 4-5 kW, then in this case the optimal dimensions of the chimney will be 0.14 by 0.2 meters.
• When using powerful equipment with indicators in the range of 5-7 kW, the cross section of the chimney should be at least 0.14 by 0.27 meters.

Advice! If you know the power of the heater used, then you can safely use the recommendations of the experts above. If the power is unknown, then appropriate calculations will have to be carried out to determine the optimal cross section.

• The amount of fuel burned in the appliance per hour. Most often, this parameter can be read in the characteristics of the equipment.
• Indices of gas temperature at the inlet to the chimney. This parameter can also be found in the hardware specifications. Most often it fluctuates between 150-200 degrees Celsius.

• Chimney height.
• The speed of gas passing through the pipe.

Note: The default value is 2 m/s.

• Indicators of natural traction. Usually this parameter is taken as 4 Pa ​​per meter of chimney length.

The main parameter in calculating the pipe section is the amount of fuel burned. When calculating the diameter of the chimney, you should use the following formula: F \u003d (π * d²) / 4. Thus, to find out the diameter, we derive a new one based on this formula: d²=4*F/π. Using it, you will already be able to determine the pipe section required for your heating equipment.

Conclusion

In order to ensure the correct operation of the heating system, it is necessary to make a competent calculation of the parameters of the chimney. Only in this case will an effective natural thrust be created. And if complex calculations are usually carried out in an industrial environment, then every home master will be able to independently determine the parameters of a domestic chimney.

The main function that a chimney for a boiler room should perform is to remove flue gases from boilers into the atmosphere and disperse them in this space. She also has an additional function: they must create natural draft resulting from the difference between the temperature in the furnace and outside.

We will introduce you to the types of smoke channels, the classification of which is based on the design features and material of the pipes. Here you will learn how the calculation of geometric parameters is carried out using a specific example. Our advice will help determine the type and size of the chimney.

In large boiler rooms, natural draft cannot provide full-fledged combustion; here it is created forcibly with the help of smoke pumps. The combustion process and the discharge of its products into the atmosphere should bring as little harm to the environment as possible and not cause emergency situations as a result of the pressure in the furnaces exceeding the norm.