How to calculate the diameter of the chimney

We frequently pay attention to the insulation in our homes or the effectiveness of our furnaces when it comes to heating them. Nevertheless, the chimney is an important part that is occasionally disregarded. For the safe and efficient ventilation of the combustion gases produced by our heating systems, a chimney that is the right size is necessary. This post will discuss the significance of determining the chimney’s diameter as well as the proper method for doing so.

Let’s start by discussing why the chimney’s diameter is important. In a furnace or fireplace, burning fuel releases gases like nitrogen oxides, sulfur dioxide, and carbon monoxide. To keep these gases from building up inside, where they could seriously endanger people’s health, they must be safely vented outside. These gases escape through a chimney, but if the chimney is too tiny, it can cause backdrafting, poor ventilation, and even chimney fires.

So how do we figure out our chimney’s proper diameter? One way is to measure the flue’s area, which is the aperture in the chimney through which the gases travel. The amount of gas that can pass through a flue is directly proportional to its area. We can make sure there is enough ventilation by calculating the area based on variables like the kind of fuel being burned, the output of the heating appliance, and the height of the chimney.

The draft, or airflow through the chimney, is another important consideration. A chimney that is the right size will produce enough draft to remove combustion gases from a home efficiently. The draft can be influenced by elements like chimney height, the temperature differential between the air inside and outside the house, and any obstructions in the chimney. Determining the chimney’s diameter is essential to maximizing draft performance.

Although there are formulas and guidelines available for calculating chimney diameter, it is still advisable to consult a professional, particularly if you are unsure of the exact requirements for your heating system. To ensure efficiency and safety, a certified HVAC technician or chimney sweep can evaluate your needs and suggest the right size for your chimney.

Factor to Consider	Calculation Method
Heat Output of Appliance	Divide heat output (in BTUs or kW) by chimney efficiency percentage (typically 70-90%)
Chimney Height	Measure height from the appliance outlet to the chimney top, then add any additional height above the roofline

General provisions

• The height of the chimney from to the point of exit is about 5 meters. In the case of flat roofs, the chimney is built high at least 50 cm
• When the chimney is located relative to the ridge in a step of one and a half meters, the height of the chimney can be 50 cm in relation to the latter or to the barrier, this applies to pitched roofs. At Distance from 1.5 m to 3 m to the ridge, the height of the pipe shall not exceed its. At a distance of more than 3 m from the ridge line to determine the height of the chimney is drawn line at an angle of 10 degrees in relation to the horizon.
• If there are tall buildings nearby, the height of the chimney for wood heating is built higher than the roof of the next building.
• Air intake ventilation ducts located near the chimney should be of the same height as the chimney.

Regarding the installation and placement of the chimney stack, there are various suggestions. Chimneys should not be placed close to roof windows to prevent the entry of carbon monoxide into the room and the products that result from wind gust combustion. The stainless steel chimney’s outer section shouldn’t be fastened firmly to the roof or rafter structure because doing so could cause the entire roof structure to be damaged in a strong wind.

Smoke stack for boiler room construction and types of types

It is impossible to calculate the boiler room chimney’s height and other parameters without accounting for the unique features of its design, which are comprised of:

• foundation and support;
• gas venting shaft;
• thermal insulation;
• anticorrosion protection;
• a device for introducing gas ducts.

For the chimney device, pipes made of brick, ceramic, galvanized, or stainless steel are utilized.

After cooling to 60º C in the scrubber, the flue gas is cleaned in absorbers before being released into the atmosphere.

Useful tools for chimney construction include:

• brick. Brick construction, installed by a professional stove, practically does not accumulate soot. It is characterized by sufficient fire safety, mechanical strength and heat capacity. Due to the destruction of bricks by reactions that occur when sulfur oxides deposited on the walls come into contact with water, the use of brick structures has been drastically reduced;
• steel. Allows modeling of the pipe configuration. Will last about ten years if fuel with low sulfur content is used;
• ceramics. Resistant to condensation, fire resistant. But the construction, weighed down by metal rods, is inherently too massive, making installation difficult;
• polymers. They are used for installation on gas columns and in the boiler room with the temperature not more than 250º C.

Chimneys can be: Depending on the supporting structure’s characteristics

• self-supporting, made of sandwich pipes. Easily mounted on roofs with fixing inside the building and, if necessary, transported, but have significant limitations in application – on temperature (350º C), snow and wind load, the level of chemical aggressiveness of combustion products;
• columnar. It is possible to install a multi-stem steel structure with a diameter reaching up to three meters when connected to several boilers;
• (near)facade. The construction is considered to be the most economical, as it does not require a strong foundation and the use of supporting elements, and the use of modules provides easy replacement;
• truss. They are used, as a rule, in areas with increased seismic activity;
• mast. The use of steel straps gives additional stability to the support tower of three or four masts with attached chimneys.

Because high chimneys are vulnerable to wind loads, extra fastening is required.

Construction of boiler plant flue pipes

The chimney may be found next to the boiler or furnace on the heating apparatus or it may stand alone. The chimney needs to be 50 centimeters higher than the roof’s height. The cross-sectional chimney’s size is determined by taking into account the boiler room’s capacity and unique building features.

The chimney’s primary structural components are:

• gas outlet shaft;
• thermal insulation;
• corrosion protection;
• foundation and support
• design intended for gas duct entry.

Initially, the cleaning device known as the scrubber is filled with flue gas. Here, the temperature of the smoke is lowered to 60°C. The gas is then purified without going through the absorbers, and only then is it released back into the environment.

Crucial! The velocity of gas in the channel has a significant impact on a boiler power plant’s efficiency, so a professional calculation is clearly required here.

Types of chimneys

Numerous kinds of flue pipes are employed in contemporary boiler power plants. Every one of them has unique characteristics:

• Columnar. It consists of an inner barrel made of stainless steel and an outer casing. To prevent condensation, thermal insulation is provided here.
• Near-facade. Attached to the facade of the building. The construction is in the form of a frame with gas discharge pipes. In some cases, specialists can do without a frame, but then anchor bolts are used and sandwich pipes are used, the outer channel of which is made of galvanized steel, the inner channel is made of stainless steel, and between them there is a 6 cm thick sealant.

Construction of the industrial chimney near the facade

• truss. It can consist of one or several concrete pipes. The truss is mounted on an anchor basket fixed to the base plate. The design can be used in earthquake-prone areas. Paint and priming is used to prevent corrosion.
• Mast. Such a pipe has ties, and therefore is considered more stable. Anticorrosion protection is realized here in the form of a thermal insulation layer and fireproof enamel. Can be used in areas with high seismic hazard.
• Self-supporting. These are "sandwich" type pipes, which are fixed to the base by means of anchor bolts. They are characterized by increased strength, which allows the structures to easily withstand any weather conditions.

Chimney diameter

The heat generator’s (furnace, boiler) capacity determines the chimney’s diameter. The complete removal of combustion products from the chimney cannot be guaranteed if the chimney’s cross-section is too small. If it’s too big, the cold air’s greater resistance to the exhaust gases will lessen the draught.

Regarding open fireboxes, the standard ratio is 1:10 for the width/height of the fireplace opening to the chimney cross-section. The best option in this situation is for the cross-sectional shape to be round. Swirls appear in structures that have a square or rectangular cross-section at a right angle, which hinders the removal of smoke to the greatest extent possible and causes soot to form. Should you still prefer a rectangular cross-section, you should select sides that are 1 to 1.5; even in this scenario, internal corners should be rounded.

When it comes to stoves, the chimney’s diameter needs to match or exceed the under-blower’sdiameter. A cross-section of 100 mm is the minimum. The cross-section is 140 x 140 mm when the heat output is less than 3000 kcal/h, and 140 x 270 mm otherwise, per the rules.

The flue shaft needs to remain vertical and unnarrowed. permitted a maximum of two deviations from the vertical at a maximum angle of 30 degrees and a maximum angle of one meter. In certain instances, a 45° angle of deviation and an attitude of up to 1.7 meters are permitted for the channel from the vertical.

Chimney material

The temperature of waste gases in contemporary gas and liquid fuel heating systems has dropped dramatically. Under these circumstances, the brick chimney cannot heat up rapidly, which causes a significant amount of condensate to appear in the chimney when the heating system is turned on. Consequently, it gathers on the flue duct walls and combines with the byproducts of natural gas combustion to create an acidic liquid that demolishes the brick.

Condensate issues do not arise with modular chimneys. These are structures put together using separate components. They are made from a variety of materials, including ceramics, aluminum alloy, carbon and polished high-alloy stainless steel. These devices can serve as independent systems that operate both inside and outside the building, or they can be installed inside brick chimneys that are already in place and rebuilt.

It’s crucial to install a condensate collector at the bottom, lubricate the joints with sealant, and assemble the modules of a steel chimney with the socket facing up.

The main signs of a good chimney are qualitative combustion of fuel, ideal draught, fast heating of the walls and fast overcoming of the dew point threshold. The second condition is met if the chimney system is well insulated. For this purpose, when installing a steel liner inside the brick channel, it is advised to wrap it with special mineral wool, or leave an air gap around it. It is not necessary to fill the space between the insert and the brick with mortar. In this case, in addition to the steel insert, it will be necessary to warm and the mortar, which, in addition, when heated, the concrete will expand and press from the inside on the wall.

Read the instructions carefully before attempting to install the chimney yourself. Your heating system’s operating parameters are the foundation upon which your calculations must be built. Use if you so choose. However, entrusting knowledgeable experts is the best course of action.

In figuring out the right diameter for your chimney, it"s crucial to consider several factors to ensure efficient heating and safe operation. First off, assess the size and type of your heating appliance, whether it"s a fireplace, wood stove, or furnace. Next, calculate the total area of all the flue outlets connected to the chimney. Then, determine the height of the chimney and its location relative to the roofline. Additionally, think about the type of fuel you"ll be burning, as different fuels require different chimney sizes for proper ventilation. Lastly, consult local building codes and regulations, as they may dictate specific diameter requirements based on your area"s climate and construction standards. By carefully considering these factors, you can calculate the chimney diameter that best suits your heating needs while ensuring safety and efficiency.

Chimney pipe diameters

There are two values for diameter for each type of product that is being considered: internal and external. When choosing products based on size, it’s important to consider the tools being used. The smaller the gas duct diameter required for its configuration, the lower the boiler output.

You can acquaint yourself with the primary measurements of stainless steel chimney pipes in the table below.

Sandwich pipe sizes for the chimney listed in a table. D is the pipe’s diameter, and H is the segment’s length.

It is crucial that the boiler outlet pipe’s cross-section and the gas duct’s interior size match. The starter pipe’s inner surface is where the majority of the exhaust gases are felt.

As a result, it needs to match the outlet pipe’s diameter. The SNiP requirements outline the primary characteristics of heating units.

Chimney pipe dimensions can be as follows:

• shaped parts – angle of tee: 135, 90, 45 degrees, outlet: 90 and 45 degrees;
• size of thermal insulation – from forty to sixty millimeters;
• length of the pipe product – from 0.5 to 1 meter;
• thickness of steel of the inner pipe (sandwich) – from 1 to 0.5 millimeters;
• outside diameter – from two hundred to four hundred and thirty millimeters;
• internal cross-section – 200, 150, 120, 115, 110 millimeters (there are variants up to 300 mm).

The installation of the chimney structure is made easier by numerous extra parts.

An extensive range of:

• stretchers, clamps and brackets;
• support platforms and protective aprons;
• headers, plugs and flue caps;
• roof seals;
• decorative overlays of passage assemblies;
• expansion joints, which are necessary to regulate changes in the linear dimensions of sandwich structures when changing temperature conditions;
• revision tees, designed to remove contaminants.

The cost of the structures that need to be built can be significantly decreased by the availability of a large variety of additional components. Sandwich chimneys are simple to put together. Their installation doesn’t require the assistance of experts and can be completed on your own.

Basic parameters of an industrial chimney

The process of creating the design documentation for industrial chimneys involves carrying out intricate calculations step-by-step.

Calculation of aerodynamic values

The structure’s minimum throughput capacity is established at this point in the design process. When the boiler room is operating at maximum loads, this parameter should have a value that permits unhindered passage and removal of fuel combustion products into the atmosphere.

Erroneous throughput computations may cause gas buildup in the pipeline or in any boiler.

Professionally done aerodynamic calculations of the chimney enable an objective evaluation of the blowing and drafting system efficiency as well as the air and gas path pressure drops.

The computations yield a professional determination of the ideal chimney height and diameter in addition to the most advantageous specifications for each section and component on the gas-air path.

The size of the structure in height

An environmentally sound method of calculating the boiler room chimney height must be used. This parameter is computed using data illustrating the atmospheric dispersion of toxic products generated during fuel combustion. Also read: "What should be the boiler room chimney: types, features, standards, and benefits of options."

For commercial and factory-type enterprises, it is necessary to adhere to specific Sanitary Norms and Rules when calculating the height of the chimney with a natural draft.

In this instance, the background concentration of hazardous emissions is given particular consideration. See also: "Norms and rules: What height of chimney is needed above the roof."

The following variables affect the final parameter:

• Meteorological regime of the atmosphere in a certain region.
• Air velocity.
• Terrain features.
• Temperature values of the vented gas.

These indicators are chosen during the building of a structure to remove hazardous byproducts of fuel combustion:

• Optimum height of the chimney.
• The maximum permissible value of the volume of harmful emissions into the atmospheric layer.

Indicators of strength and stability of the chimney

Appropriate calculations, which include a thorough evaluation of the ideal stability and strength of the structure, also influence the design of the pipe.

The following computations ought to be performed to ascertain the chimney’s resistance to the following influences:

• Seismic activity.
• Soil behavior.
• Wind and snow loads.

Additional functional characteristics of the pipe are also considered:

• Weight of the structure.
• Dynamic equipment fluctuations.
• Expansion under the influence of a certain temperature.

We can choose the ideal chimney design and shape by determining the strength characteristics. The foundation for the constructed structure is calculated based on the carried out calculations; its design, the volume of burial, and the footing area are established.

Thermal calculations

There is a reason why thermal calculations are done:

• Determine the expansion parameters of the original material under the influence of a certain temperature.
• Determine the temperature of the outer shell.
• Choose the type and thickness of insulation material.

Placement of sandwich chimney recommendations

Even a novice can install such a structure, but there are a few key guidelines that must be followed for a successful installation:

• The height of the chimney in relation to the vertical roof should not be less than 0.5 m;
• If the roof is made of flammable materials, the height of the structure should be higher – from 1 m higher;
• If the distance between the outlet pipe and the roof ridge is 1.5 m, the height of the chimney should not exceed 0.5 m;
• If this distance – more than 3 m, then the height of the chimney is calculated from such considerations – an imaginary line at an angle of 10̊ from the ridge of the roof to the horizon is drawn. Read also: "".

What parameters need to be calculated

The following parameters must be determined for the calculation:

1. Length. The first thing you need to be sure to determine the maximum height of the building, how many meters to the ridge of the roof in the very place where the output of the future pipe is supposed to be. Because the length will determine some of the most important characteristics of the future system. Take into account the fact that too high channels will simply "eat" the draught, as a result, it will reach the heat source at a slower speed, and therefore your furnace will burn much worse. In addition, "terrible" and too low chimneys in relation to the roof, about this will be more detailed below.
2. Diameter of the chimney (cross-section). As for this parameter, it is necessary to take into account not so much the dimensions themselves, but initially the shape of the pipe itself. Do not forget an important condition, if you want to get a quality chimney system, working according to all the rules, the pipe must be cylindrical. That is, the walls must be round, so that soot and grime are less retained in the channel. Thus, you repel the moment . As for the size (diameter), it should be chosen based on the cross-section of the main outlet pipe of the furnace or boiler. Use pipes with a diameter larger or smaller than the spigot, is not recommended. High probability of depressurization.

How the chimney is calculated

Understanding the heater’s specifications is essential for calculating the size of the flue pipes. Chimneys are primarily measured by height and cross-sectional diameter. These data can be found in the equipment’s corresponding documentation.

We advise looking over the information on our website about assembling a vermiculite chimney by hand.

How to calculate the height

The effectiveness of the calculations for chimney height is crucial since it directly affects how well heating devices operate. The documentation from SNiP states that a chimney must be at least five meters high. The chimney won’t have the required natural draught if it is smaller than this number. But an excessively tall chimney is also problematic because it will cause smoke to cool down more slowly as a result of reducing the draught.

Chimney height calculation

In industrial construction, chimneys are carefully calculated. In this case, a highly intricate computational system is utilized. However, the regulations are typically far less stringent in private construction, and the following guidelines must be followed when determining the chimney’s height:

• From the base to the highest point, the length should exceed 5 meters.
• When going out on a flat roof, the chimney should 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 to the roof ridge, the calculation of its height is carried out in the following way: the line connecting the roof ridge with the chimney and the horizontal line of the roof ridge should be located to each other at an angle of 10 degrees.

It is highly advised to avoid placing the chimney next to doors or skylights as this may cause sparks to fly throughout the building in the event of a strong wind.

How the cross-section of a chimney is calculated

The primary kinds of chimney cross-sections

The diameter of the chimney must be ascertained in advance in order to calculate the draught. You can use the following expert advice to avoid performing complicated calculations:

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

Advice: You can use the above-mentioned expert recommendations with safety if you are aware of the heater’s power. It will be necessary to perform the necessary computations in order to determine the ideal cross-section if the power is unknown.

To accurately compute the chimney’s cross-section, the following information is required:

• The amount of fuel burned in the appliance during an hour. Most often this parameter can be read in the characteristics of the equipment.
• Indicators of gas temperature at the inlet of the chimney pipe. This parameter can also be found in the characteristics of the equipment. Most often it ranges between 150-200 degrees Celsius.

The determination of a fireplace’s pipe cross-section based on its height

• Chimney height.
• Gas velocity through the pipe.

Note: This parameter has a default value of 2 m/s.

• Indicators of natural draught. Usually this parameter is taken as 4 Pa for each meter of the chimney length.

The quantity of fuel burned is the primary factor used to determine the chimney’s cross-sectional area. The formula F=(π*d²)/4 should be applied to determine the chimney’s diameter. Therefore, using this formula as a base, we derive a new formula to find the diameter: d²=4*F/π. You can already use it to calculate the pipe’s cross-sectional area that your heating equipment needs.

Basic fuel combustion rates vary based on the fuel type.

Brief characterization of the calculation methodology

The primary unknowns in the computation, which is based on the finite element method, are the rotations and displacements of the design scheme’s nodes. In this regard, the structure is idealized in a way that is tailored to the application of this technique, specifically: the system is depicted as a collection of standard-type bodies (rods, plates, shells, etc.), referred to as finite elements, that are connected to the nodes.

The physical law defining the relationship between internal forces and internal displacements, the set of parameters (stiffnesses) included in the description of this law, the geometric shape of the finite element, the rules defining the relationship between the displacements of the finite element’s nodes and the nodes of the system, etc., all determine the type of finite element.

A node in the displacement method’s design scheme is depicted as a perfectly rigid body with minuscule dimensions. The coordinates of the center and rotation angles of the three axes that are rigidly attached to the node determine the node’s location in space during the system’s deformations. Three linear displacements and three rotation angles give the node six degrees of freedom as an object.

Every component and node in the design scheme has a number. Only names that enable the required references to be made should be understood from the numbers that have been assigned to them.

The fundamental mechanism of the displacement method is chosen by enforcing a prohibition on any nodal displacements in every node across all links. The displacements of these links are the primary unknowns in the displacement method, and the conditions of zero forces in these links stand in for solving equations of equilibrium.

Generally speaking, all six movements can be found in the node’s spatial structures:

1-a displacement that is linear along the X axis;

2-a displacement that is linear along the Y axis;

3-a displacement that is linear along the Z axis;

4-rotation around the X axis, or rotation angle with a vector along the X axis;

5- rotation around the Y axis (rotation angle with vector along the Y axis);

Six is the angle of rotation about the Z-axis with a vector along it.

The nomenclature X, Y, Z, UX, UY, and UZ are used to indicate the values of the corresponding linear displacements and rotation angles, respectively. The numbering of displacements in the node (degrees of freedom), as previously stated, is used throughout without any special reservations.

The true shape of the displacement field inside the element is approximated by a variety of simplified dependencies, in accordance with the philosophy of the finite element method (apart from rod-type elements). In this instance, the error in calculating the stresses and deformations is of the order of (h/L) k, where L is the area’s characteristic size and h is the maximum grid spacing. Degree k determines the convergence rate, or the rate at which the approximate result error (stresses) is reduced. Different displacements and internal force components have different values for degree k.

Types of chimneys

Characteristics of the modern chimney device

The chimney’s main function is to remove smoke and combustion byproducts from stoves and other heating appliances that are outside of rooms. In a typical home chimney, traction develops on its own without the aid of any extra equipment.

Chimneys of today can be made:

• Brick. Since such a construction has a significant weight, it is necessary to build a strong foundation for it.

Experts recommend mixing lime into the bricklaying mortar to prevent condensation, which can be harmful to the building’s walls.

Brick chimney configuration

• Sandwich pipes, which are made of two layers of metal with insulation between them. As a material for the manufacture of such pipes, stainless steel is most often used. Insulation in most cases is basalt.
• From polymeric materials. Such pipes should not be exposed to excessively high temperatures, so use such chimneys can be used for gas stoves and boiler rooms of small size. At the same time, polymer chimneys are very durable, easy to install and are characterized by a low price.
• Made of ceramic. Such pipes are characterized by high durability, but they also cost a lot. Therefore, they are most often used for the arrangement of chimneys of industrial type. Due to its considerable weight, such structures, as well as brick, require the laying of a foundation.

We suggest that you thoroughly review the information regarding a gas boiler’s coaxial chimney.

Block-style ceramic chimney that is external

Crucial! Combinations of chimney materials are feasible in certain circumstances. Brick lining is one way to line a chimney made of metal or polymer.

Readers find these materials useful:

• Installation of ceramic chimney with your own hands, tips and recommendations

How the diameter of the chimney is calculated

In order to compute the draught, the required diameter of the chimney must be determined. If the heating unit’s capacity is known, the following guidelines can be used as a guide:

• If the power is less than 3.5 kW, it will be enough chimney cross-section 0,14×0,14 m;
• at a power of four or five kW optimal will be a cross-section of 0,14×0,2 m;
• at a power of five to seven kW – 0,14×0,27 m.

The following information is needed to calculate the chimney’s cross-section:

• the amount of fuel consumed per hour (information is contained in the passport of the equipment). This parameter is considered as the main parameter;
• the temperature of the gas entering the pipe (also passport data, about 150-200º C);
• Chimney height;
• gas velocity in the pipe, usually taken as 2 m/s;
• the natural draught indicator, which is generally taken as 4Pa.

Multiplying the chimney’s height by the difference in air and flue gas densities makes the calculation easy to do.

You can use the following formula:

D2 = 4V/πW, whereby:

V is the gas volume; W is the gas movement speed in the pipe; and d2 is the required value of the cross-sectional area.

The formula for figuring out the diameter is:

S = m/ρw, where:

S stands for cross-sectional area; m for fuel value used in an hour; and ρ for chimney gas density. It is typically assumed to be equal to the air density; w is the chimney’s gas velocity. This simplifies computations. It is preferable to enlist the assistance of experts who meet the requirements when determining the diameter of the chimney with a high degree of accuracy. For private residences, it will be sufficient to arrange chimneys in accordance with the broadest guidelines.

If the chimney’s aerodynamic calculation is done correctly, you can expect the heating system to operate successfully for many years. You don’t need to be concerned that the chimney will become blocked with soot and need repairs because you have managed to achieve a good natural draught and high throughput. Accurate computations will guarantee that the boiler equipment functions in complete accordance with the demands of environmental laws. Two things will come together to guarantee an existence that satisfies the requirements of contemporary society: a temperature that is comfortable in heated rooms and no harm is done to the environment or public health.

Why a chimney calculation is required

The flue venting system needs to be configured correctly for your furnace to function properly. This is greatly influenced by two fundamental parameters, which are explained in more detail below.

They will ascertain the type of draft and the efficiency of the smoke extraction from the stove. The safety of the occupants of the room as well as the system’s functionality will determine how to calculate the chimney pipe correctly.

In order to easily learn and determine how to calculate the chimney yourself, pay attention to any subtleties and study the theory.

Which chimney is better

A stainless steel cylinder is thought to be the ideal shape. Metal chimneys with the necessary diameter pipes are integrated into brick chimneys as well. The cylinder is the best choice for maximizing draft because the products of combustion move upward in a spiral.

Swirls within brick chimneys, whether square or rectangular, lessen the draught. This type of chimney is particularly useful for stoking wood-burning fireplaces and stoves since it lets you reduce the heat output and the shape of the chimney improves appliance efficiency. Only two heating appliances can be served by a single chimney, and even then, only if the size of its internal cross-section permits it to operate them in parallel.

For stoves and fireplaces, stainless steel chimneys are more affordable and far stronger than brick ones. Unlike brick chimneys, which have the potential to collapse during operation, stainless steel chimneys are impervious to corrosion and temperature changes. Because the entire structure is made of modules, these chimneys are simple to operate and replace any broken parts. Installing a stainless steel chimney for a stove or fireplace will be considerably simpler.

Complex air intake branches with varying lengths can be created. In terms of area, stainless steel chimneys are 40–50% smaller than brick chimneys. You can use online calculators, which are found on portals and profile sites, to determine the chimney height in relation to the ridge on a pitched roof, or you can hire an expert to do it for you.

Example of calculating the cross-section of the chimney and choosing its shape

Assume that we own a fireplace. Its portal is three masonry units wide and eight masonry units high. This measures roughly 75 x 58 centimeters in centimeters. In this instance, the channel’s size is equivalent to a brick’s area. It measures 12.8 by 25.8 cm.

We take note of the fact that the dimensions may vary for products made by different factories; therefore, the information should be clarified before laying, after ordering and taking precise measurements, and after careful consideration. Let’s do the math now:

1. The letter F denotes the area of the fireplace portal, it is equal to 75 x 58 = 4350 square centimeters.
2. The small letter f denotes the cross-sectional area of the chimney, meaning its internal passage part. That would be 12.8 x 25.8 = 330.24 square centimeters.

Let"s take the ratio F/f = 7.6%. Now let"s look at the graph to see what we get… From drawing We can see that the rectangular chimney in these conditions will not work, that is, it is necessary to choose a round chimney of the same cross-section, and the height of the pipe should not be lower than 17 meters. Too big for a private cottage? Then make the area of the chimney a little more, so that the percentage fit into the calculated height or replace the round cross section. Chimneys with a diameter of 80 mm, for example, have an area of 50.24 square centimeters, this will not be enough. Then it is better to proceed from the inverse condition of the minimum required diameter. It can be easily found from the given height. (See. also: Making fireplaces with your own hands)

For instance, a two-story mansion with a height of 11 meters from the fireplace to the chimney cap is intended to be constructed. In this instance, the area percentage ratio shouldn’t be any lower than 8.4%. We select a chimney diameter that works well for the fireplace because you probably won’t want to change the design. Specifically, the chimney’s area will be the same:

F = Fx 0,085 = 370 cm2, from which the diameter can be calculated:

D is equal to -4 x f / P, or -4 x 370 / 3.14, or 21.7 cm.

Depending on the size of the portal, you can compute the chimney’s cross-section in this way. It is best to use caution when taking it. Here’s one more thing to consider. The following substances are utilized to make chimneys:

1. Glass.
2. Ceramic.
3. Steel.
4. Asbocement.

Using bricks to construct a circular chimney will be challenging. In this regard, select the suitable material, keeping in mind that glass chimneys are highly costly and that asbozem should be set aside when burning gas or diesel fuel in the furnace. Steel is the better choice in this situation because it can withstand the effects of harsh media. (See. additionally: )

How to choose the shape of the internal cross-section of the chimney

Understanding the fundamentals of the chimney’s operation is essential to determining its ideal shape. The smoke twists along the center axis as it rises due to the uneven heating of the walls. This makes it simple to conclude that a cylindrical chimney is the most appropriate shape.

When using a chimney with a rectangular cross-section will inevitably occur swirls, serving as an obstacle to the normal draught, and sometimes even appears . In this case, the greater the speed of the draught itself, the stronger swirls are formed, and the worse is the process of gas propulsion. This nuance should be taken into account when calculating the chimney draught, because in principle the rectangular shape is acceptable, but only for those heating devices that do not require a strong draught for operation. Moreover, such chimneys have their own advantage – they retain heat longer than cylindrical chimneys, so when properly designed for traditional stoves and fireplaces, rectangular chimneys are the best choice. At the same time, for modern heating boilers operating on the principle of "stop-start" it is advisable to install cylindrical pipes. When using such boilers, savings are achieved due to faster heating of the system to the required temperature, because after that they go into standby mode. And faster heating is ensured by a strong draught, which is possible just in the case of cylindrical chimneys.

How the diameter of the chimney affects its height

SNiP controls the height of all flue ducts; the internal form and cross-section should also be taken into account. These factors have a significant impact on the efficiency and functionality of heating systems.

Since warm air is heated, it rises, and the closer it gets to the outside exit, the more it cools, creating a draught. The air cools down more quickly in very large internal cross-sections of the chimney, forming a, which is detrimental to the actual draught.

What actions are possible? By decreasing its cross-section, the chimney’s height can be increased. In this scenario, the draught will intensify to the point where the heating boiler, stove, or fireplace loses efficiency. The heater won’t heat up properly since there will be a significant increase in the amount of cold air entering from below. due to the necessity of using more fuel and taking longer to heat.

A small internal cross-section and a tall chimney will also not provide a sufficient draught for the stove or fireplace to operate properly. Both smoke and carbon monoxide can enter the room itself. It is preferable to get professional assistance or use a calculator to determine the height of the chimney pipes in order to avoid running into this kind of situation.

Types of chimney products

Currently, a variety of stainless steel flue ducts are manufactured.

Products made of pipes are:

• corrugated;
• smooth single-walled;
• sandwich.

The first and last product variants are uniquely circular in cross-section due to their structural design. Products with a single wall can be oval or rectangular in shape.

Rectangular-shaped products are hardly ever used. They are intended to be installed within chimneys made of brick. These products are typically made exclusively upon request.

A variety of metals are used to make chimney pipes.

The steel grades most in demand are:

• AISI 304;
• AISI 310;
• AISI 316.

High resistance to acids characterizes the first steel grade on the list. It operates at temperatures as high as 250.000 degrees Celsius without failing to perform flawlessly. This material is capable of withstanding temperatures as high as 600 degrees Celsius when used with non-aggressive gases. It is typically used to outfit single-wall buildings or sandwiches that are meant to be serviced by low-temperature heating units.

Steel grade AISI 310 is resistant to heat. It is resistant to heats of up to 1,000 degrees. A tubular product composed of this metal maintains its shape at the same time. This material has a moderate level of resistance to acids. However, the arrangement of solid fuel boilers is its intended use.

The best steel grade is AISI 316. This substance is used to make different kinds of chimney channels. It has strong heat resistance and an excellent indicator of resistance to acidic environments. Nine hundred degrees Celsius is not a problem for this grade of steel. It is compatible with all kinds of boilers.

Pipe products that are used to arrange chimney channels frequently have extra insulation against heat. All of the previously discussed pipe types share this feature. Manufacturers typically provide product variations with and without extra thermal insulation. In the second scenario, basalt fiber mats play that role.

The simplest calculation of the size of the chimney opening

Chimney diameter calculation.

Naturally, it can be challenging to perform accurate calculations when building a furnace by hand without the aid of plans or instructions. This is especially true for Russian stoves, where it’s crucial to consider not just the section but also the pipe’s height and the existence of a blowpipe for air inflow. In this instance, a fairly straightforward formula is applied; however, measurements of the firebox’s area are first required for computations, which is crucial since more fuel can be accommodated there, increasing power.

The cross-section of the chimney is 1:1,5, which is directly proportional to the furnace’s size. In addition, the chimney’s cross-sectional area must not be smaller than the under-blower’s.

You can independently ascertain the chimney’s cross-section with such basic computations. By the way, the height of the chimney affects the quality of the stove or fireplace and how well it operates. However, in this case, you can follow another rule: the higher it is, the better the heater’s draft properties, regardless of whether you built it yourself or bought it ready-made from the manufacturer.

Furthermore, you do not need to create a chimney opening with a larger cross-section than necessary because an increase in the cross-section of the chimney opening directly correlates with an increase in the draft properties, which in turn increases the rate of fuel combustion.

It is best to seek professional assistance when calculating the chimney opening for large buildings and structures. This is required to ensure that the entire building or room is heated by your heater, not just a portion of it. Furthermore, the chimney in a multi-story building needs to be properly planned, which requires knowledge and experience. However, you can perform all of the computations on your own or with the assistance of your contacts if you have experience with them or know someone who does. The most crucial thing to remember is to create designs and schemes for the chimney opening device.

Can a chimney be universal

The choice of material used in the design and construction of a chimney is one of the most crucial factors to take into account. Many businesses today sell contemporary chimney systems, claiming that their products can be used with any type of heating equipment and in any environment, regardless of the fuel source. But in actuality, this is just a marketing gimmick because there is no way that such universal systems could exist. Individual chimney systems can, of course, operate fairly effectively in a variety of situations and with a variety of fuels, but in this instance, adhering to all regulations and specifications is not an option.

Description of loads and their characteristics

Both static and dynamic loading must be considered in the structure’s design.

The system’s dynamic calculation is carried out by breaking down the natural vibrations into their component parts. The utilization of the maximum number of forms listed below in this computation:

Six forms of wind flow pulsation according to SNiP 2.01.07-85*

"Wind flow pulsation according to SNiP 2.01.07-85*" is computed for dynamic loading using a methodology that adds the static and pulsation components of the wind load to determine the wind pressure on the structure. Due to a random pulsation rate, the latter is a random function of time. The inertial forces corresponding to each type of natural oscillation and the static component of the wind load are distinct from the forces in the system’s elements and displacements of its points (generalized – the reaction of the structure X). The formula gives the total reaction value.

Which shows that the oscillations are centered on the shifted equilibrium state that corresponds to the loading’s static (average) component. The computation’s outcomes display the distinct elements of the dynamic response Xid as well as the sum of the values for all dynamic and static components. The dynamic additive’s sign is identical to that of component X c.

Methods of calculations

Exact method + formula

Determine the chimney length for a stove—this is a task best left to experts. It is preferable to let experts handle this task. However, you will need to be familiar with the following formulas and basic data if you choose to calculate this parameter yourself:

1. To determine the cubature of the outgoing gases, it is important to know the power of the heating unit. For calculations we apply the formula:, where:

• B is the coefficient of solid fuel combustion rate. This value is determined based on the data in Table 10 of GOST 2127;
• V – the level of the volume of fuel burned. This value is indicated on the tag of the industrial device;
• T is the level of heating of exhaust gases at the place of exit from the chimney. For wood stoves – 1500.

1. Total area of the chimney. It is calculated based on the ratio of the volume of gases, this value is denoted "Vr" and the speed of their advancement in the pipeline. For a household stove, working on wood, this number is equal to – 2 m / sec.
2. The diameter of the round chimney is calculated by the formula – d² = (4 * Vr) / (π * W), where W is the velocity of gases advancement. All calculations are better to perform on a calculator and carefully enter all values.

Calculate the optimal value of draught

This process is carried out to regulate the computation of the chimney’s ideal height and cross-section. Two formulas can be used to perform this calculation. In this chapter, we will provide the basic, complex formula, and when calculating the trial data, we will provide the basic, simple formula:

• C is a constant coefficient, equal to 0.034 for wood stoves;
• literature "a" – the value of atmospheric pressure. The value of natural pressure in the chimney is 4 Pa;
• the height of the chimney is denoted by the letter "h".
• T0 is the average temperature level of the atmosphere;
• Ti – the value of heating of exhaust gases when they leave the pipe.

Example of chimney cross-section calculation

We start with:

• the bourzhuika works on solid fuel;
• within 60 minutes in the stove burns up to 10 kg of hardwood firewood;
• Fuel humidity level – up to 25%.

Let’s repeat the fundamental formula:

The computation process is divided into multiple phases:

1. We perform the action in brackets – 1+150/273. After calculations we get the number 1,55.
2. We determine the cubature of the exhaust gases – Vr= (10*10*1,55)/3600. After calculations we get the volume equal to 0,043 m3/sec.
3. Area of the chimney pipe – (4*0,043)/3,14*2. Calculation gives the value – 0,027 m2.
4. We take the square root of the area of the chimney and calculate its diameter. It is equal to 165 mm.

We now use a straightforward formula to calculate the draught’s value:

1. According to the formula of power calculation we calculate this value – 10*3300*1.16. this value is equal to – 32,28 kVt.
2. Calculate the level of heat losses on each meter of the pipe. 0,34*0,196=1,730.
3. The level of gas heating at the section of the pipe outlet. 150-(1,73*3)=144,80.
4. Atmospheric pressure of gas in the chimney. 3*(1,2932-0.8452)=1,34 m/sec.

Crucial! You can do the calculation on your own using the furnace’s data, but it’s best to get professional advice just to be sure. The efficiency of heating appliances and the security of your house depend on accurate computation. Swedish computation technique

Swedish method of calculation

The Swedish method is primarily used to calculate the chimneys of fireplaces with an open firebox, but it can also be used to determine the size of the chimney for a stove.

The calculation in this methodology does not take into account the flue compartment’s size or air volume. Utilizes the graph to assess whether the computation is accurate:

Here, it’s crucial to match the chimney opening ("f") to the furnace compartment area ("F"). As an illustration:

• firebox dimensions 770/350 mm. Calculate the area of the compartment – 7,7*3,5=26,95 cm2;
• chimney size 260/130 mm, chimney area – 2,6*1,3=3,38 m2;
• calculating the ratio. (338/2695)*100=12,5%.
• look in the lower part of the table value 12,5 and see that the calculation of length and diameter is correct. For our stove it is necessary to build a chimney, the height of 5 m.

Let’s examine yet another calculation example:

• firebox 800/500 mm, its area is 40 cm2;
• chimney cross-section 200/200 mm, the area is equal to 4 cm2;
• calculate the ratio (400/4000)*100=10%.
• Use the table to determine the length of the chimney. In our case, for a round sandwich – pipe it should be 7 m.

When it may be necessary to calculate the cross-section of the chimney

Usually the task is for the design organization that is working on the order of a stove, fireplace or other similar appliance. But in this case, most often there is a ready-made set of arrangements. Moreover, such schemes can be found by anyone on the Internet. For example, one stoveman from Izhevsk posted a long instructive video on YouTube, where he describes all his actions in detail. The same applies to grills, barbecues and everything else in the world. Instead of racking your brains, just type in a query on the net, such as ordering . That is: (See. also: How to build a fireplace with a firebox)

• stove layout;
• fireplace masonry;
• barbecue stove layout and everything in the same vein.

It’s highly likely that something essential will be discovered. For instance, the Izhevsk stove manufacturer has hundreds of ready-made designs on his website, osnovaremonta.ru, that are just waiting to be made into reality. The resource is actually full of helpful videos that will show you how to do masonry in this or that case; we’re not sure why it has such an odd-sounding address.

Take note of the meticulous joint tying that is done, and the explanation of how to split the brick and how many halves, quarters, and other pieces will be required. I really love this course.

Additionally, the option is excellent.

We selected the most compelling moments from our perspective from the resource so that readers would only bother to search if they had beforehand prepared. The guidelines for choosing the cross-sectional area of the chimney of different designs are shown in full and exact detail in the diagram below. This is not limited to closed systems that get their air supply from outside sources, like the street. However, in this instance, using forced oxygen injection—as in condensing boilers—or replicating the current factory design is the easiest course of action.

The three different cross-sectional types are displayed at the top of the graph:

1. Round.
2. Square.
3. Rectangular.

Let’s now collaborate on thought! What cross-sectional form does the great majority of boilers, convectors, and hoods share? Round is the right response. And this diagram shows why the designers chose to lay it out this way rather than another. Let’s clarify the items that we have arranged both vertically and horizontally: (See also: Manually constructed stove chimneys)

1. On the abscissa axis, we see some kind of ratio that results from dividing the area of the chimney by the area of the portal. To get the percentages, multiply the partial by 100.
2. On the vertical axis is placed the minimum height of the chimney at which the structure will be wealthy.

It is now evident to readers that the pipe’s minimum height will coincide with its circular cross-section. Rectangles are the worst option when it comes to guaranteeing system performance. The sides of a stove chimney typically match the length of the bricks. These are 25 cm x 13 cm, 25 cm x 25 cm, and t.д., roughly. To better understand how to calculate and select the shape of the chimney cross-section, let’s probably jump right into the example. (See. additionally: )

Why do you need a chimney calculation

The following situations call for the calculation of a chimney for a stove, boiler, fireplace, or other heating equipment:

• ensuring proper draught, by means of which all substances harmful to human health, formed as a result of combustion, were discharged outside the living space. If unacceptable substances enter the house, a person can get severe poisoning, which can be fatal;

Reverse draught in the chimney: potentially dangerous

• optimizing the heat received in relation to the fuel consumed. If most of the warmed air is vented to the chimney, more wood will be needed to warm the room. With the correct ratio of fuel to heat produced, the warmed air will maximize the heating of the furnace and chimney walls, reducing the resources expended;
• The chimney calculation is also required to maximize the possibility of providing a fire protection situation. Strongly heated air coming out of the chimney or low draft can lead to sparks on combustible surfaces, which will inevitably lead to a fire.

A heating appliance with a chimney that is properly measured and installed

By calculating the pipe’s parameters, you can not only conserve fuel but also guarantee the well-being and security of those residing in the living area.

Collective chimney correct connection

The size of the chimney, when utilized for multiple heating appliances at once, is a different conversation topic.

In the event that smoking from multiple heating sources is required, the chimney’s calculation takes into consideration each heating source’s type, power, and fuel consumption.

• For example, in a house with a single chimney several heating devices are installed, a boiler of a common heating system and a fireplace.
• It is immediately clear that we have completely different systems in front of us. The diameter of the chimney of the fireplace does not correspond to the diameter of the boiler chimney at all.
• Typically, fireplaces run on wood fuel and home heating boilers run on natural gas.

Can these two entirely different systems be combined? Indeed, we are able to. Furthermore, if the heating appliances are positioned correctly, they will not only not cause issues, but also work in harmony with one another.

How does it occur?

• One chimney includes a boiler and a fireplace. During operation, the boiler periodically switches off and goes into standby mode. We have a fireplace running at the same time. Therefore, the chimney maintains a normal temperature, the gases do not cool down.
• Hence no condensate and good draught at the subsequent start of the boiler.
• But the size of the chimney for a fireplace must be much larger than for a boiler. And in case we use only the boiler without starting the fireplace, we may have problems with excessive draught leading to improper operation of the boiler.
• As we know, the diameter of the chimney for a fireplace is calculated by the ratio of 1:10 to its firebox. It becomes clear that such a diameter of the chimney is very large for the boiler. People use the fireplace infrequently, and the heating boiler works constantly in winter time.
• So we have to make a smaller chimney with a smaller diameter, suitable for the boiler? No, this would be a big mistake. When the boiler works independently, everything will be fine. When the fireplace starts up, there will be increased aerodynamic resistance in the chimney. A two-pass chimney. Rice. 1

• improper operation of heating devices;
• Carbon monoxide entering the room.

Life is already in danger because of it. Poisoning with carbon monoxide is frequently fatal.

Two-pass chimney – the solution to the question

How can this problem be resolved?

Utilizing a two-pass chimney is what we advise.

The benefit of a chimney with two passes:

Chimney that is bidirectional. Rice 2.

• The possibility of using different thermal appliances simultaneously and separately in one chimney;
• stable operation of each appliance;
• savings in construction and installation;
• space saving.

It is vital to meet all requirements for each appliance’s correct operation before installing such a chimney. Should the fireplace operate flawlessly with a brick chimney, the boiler needs to be covered. By doing this, the brick will be shielded from the condensate’s alkaline effects.

Become familiar with each heater’s operating parameters before installing a chimney for multiple systems. Investing in an industrially manufactured special two-pass chimney is the best course of action. You will protect yourself from potential design errors in this way. It is a challenging task to connect various heating devices in one chimney, even for an experienced specialist.

One of the most important steps in making sure your home has effective heating and ventilation is calculating the diameter of a chimney. Homeowners can maximize their heating systems by making informed decisions by knowing the factors that affect chimney diameter.

The kind of fuel being used is an important factor to take into account when determining chimney diameter. In order for combustion byproducts and smoke from different fuels to properly vent, different chimney sizes are needed. For instance, larger chimneys are usually needed for wood-burning stoves than for gas or oil heaters.

The chimney’s height is another crucial component. Stronger drafts produced by taller chimneys aid in better ventilation and keep smoke from backing up into the house. Achieving a balance is crucial, though, as overly tall chimneys can result in significant heat loss and draft problems.

Chimney diameter is also influenced by the heating appliance’s dimensions and design. Greater heat output from larger appliances will necessitate larger chimneys to handle the higher volume of exhaust gases. Similar to this, the quantity of bends and offsets in the chimney pipe can influence airflow and call for changing the diameter.

To guarantee adherence to safety standards, it is imperative to refer to pertinent building codes and regulations when determining the diameter of a chimney. These codes frequently outline minimum chimney size requirements based on variables like building height, appliance size, and fuel type.

To sum up, determining a chimney’s diameter requires taking into account a number of variables, including the kind of fuel, the height of the chimney, the size of the appliance, and building codes. Homeowners can choose the ideal chimney diameter to guarantee secure and effective heating and ventilation in their buildings by carefully weighing these variables.

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