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What diameter of the chimney to choose for a gas boiler. Chimney device for a gas boiler: a professional approach. Do-it-yourself coaxial chimney for a gas boiler

The correct operation of heating gas equipment largely depends on the system that removes combustion products. Before you equip a chimney for a gas boiler in a private house, you need to have an idea about the types of equipment, the principles of its operation and the regulatory documents according to which it is installed. Regardless of who will carry out the work, the choice of device and installation should be taken with full responsibility.

Installing a combustion products disposal system on a gas boiler contributes to the efficient functioning of the equipment and the entire heating system, safe and comfortable heating, as well as trouble-free operation of the boiler. Before you buy a chimney for a gas boiler, it would be useful to get expert advice about the existing options for chimneys and the feasibility of their use.

Types of smoke channels to gas boilers:

• brick chimney - its construction is planned at the stage of building a house and a foundation is laid under it. A prerequisite is the smooth surface of the inner walls of the chimney. It should be noted that the structure must be resistant to the action of acid, which is formed due to the condensation of steam. Otherwise, there will be a rapid destruction of the brick pipe for the chimney. Used in combination with ceramic or steel liners. Brick chimneys for gas boilers are distinguished by their complex structure, the duration of construction and the costly cost. In terms of technical indicators, they are in many respects inferior to the modern chimney systems that have appeared;

• construction of stainless pipe - this version of the chimney is highly resistant to chemical environment and mechanical damage. The system is made in the form of a sandwich construction: when a pipe with a smaller diameter is inserted into the outer pipe. A fire-resistant material - basalt wool - is laid in the free space between them. Manufacturers offer a wide range of chimney models;
• coaxial chimney - the design is assembled according to the "pipe in pipe" principle: combustion air is taken in through one pipe, combustion products are removed through the other. Such a system has high technical characteristics that enhance the safety of all gas equipment and increase its efficiency. And due to the fact that the combustion cycle takes place outdoors, a boiler with a coaxial chimney is an environmentally friendly equipment;
• chimney made of ceramic pipes - is a ceramic blocks with thermal insulation, installed in a concrete frame. Such a flue system is resistant to temperature fluctuations, waterproof, fireproof and has high mechanical strength. The main requirement for installation is high-quality joining of ceramic modules.

Which chimney pipe is better to use - everyone decides based on their specific situation. The main thing is to highlight the strengths and weaknesses of any option. Regardless of which type of chimney you prefer, its design and installation must comply with SNiP 2.04.05-91 "Heating, ventilation and air conditioning". After studying these standards, you can learn how to properly install a chimney on a gas boiler.

Chimney for a gas boiler in a private house: basic requirements of SNiP 2.04.05-91

Measures for installing a chimney for a gas boiler, starting from the design stage and ending directly with the installation of the system, must comply with the requirements of the current regulatory framework, since improper installation and operation of gas equipment calls into question the safety of people using gas installations.

The main elements of the chimney design:

• flue - the channel leaving the boiler into the chimney pipe is connected by an adapter;
• chimney pipes;
• revision - attached to the bottom of the chimney and serves to clean the channel from combustion products and remove excess moisture;
• fasteners (brackets, clamps) - are used for fastening to the wall;
• other accessories for the system device.

As a rule, the location of a gas boiler in a private house is planned on the lower floor in a separate room (boiler room). All elements of the heating system must be interconnected strictly hermetically. The basic rules for installing chimneys for gas boilers, which regulate the technological order, are presented in the regulations SNiP 2.04.05-91 and contain the following requirements:

• proper draft - ensures complete removal of exhaust gases;

• resistance to high temperatures;
• tightness of docking points - all components along the entire length of the chimney system must fit snugly against each other;
• the pipe at the place where it passes through the ceiling must be solid, without joints;
• condensate collector - the design of this element must ensure the collection and removal of liquid;
• if there are turns in the structure, inspection hatches are arranged in these places to diagnose the state of the chimney, clean it and remove condensate;
• the length of the pipe branch to the side should not exceed 1 m;
• possible permissible number of turns on the chimney pipes - no more than 3;
• the height of the chimney pipe must exceed the height of the roof (at the highest point), so that good draft is ensured and no reverse occurs;
• the distance between the chimney pipes and the surface, which is made of non-combustible materials, can be at least 5 cm, and if the surface material is combustible - not less than 25 cm.

Helpful advice! Complete tightness of the chimney sections will not allow hot combustion products to go beyond the system.

The procedure for installing a gas boiler chimney in a private house

Depending on at what stage it is planned to install a chimney for a gas boiler, the exhaust system can be internal or external (remote). In cottages under construction, where the use of gas boilers is provided, internal chimneys are used, the placement of which is taken into account by the project. In old-built houses, when switching to heating by means of a gas boiler, the chimney is led outside.

You can compare the strengths and weaknesses of outdoor and remote chimneys by reading the table:

Chimney type
remote	Interior
Complete chimney insulation required	Thermal insulation is only necessary in the area that goes outside
Safe operation is guaranteed if the regulations are followed	The possibility of penetration of combustion products into the room is not excluded, a high fire hazard
The chimney device is made of the same type of elements and is characterized by ease of execution	Differs in complex installation, as there is a need for a large number of components and components of the chimney
Availability in carrying out any kind of repair work and maintenance	Difficulty in maintenance and repair of the chimney

The installation of the chimney of an internal type gas boiler is associated with the construction of a foundation and a protective channel made of bricks. Then the safety of operation will be ensured. Such systems are more efficient and the formation of condensate in them is minimal. In some cases, chimneys can be attached to the wall of the house behind which the boiler is installed.

The device of an external chimney requires high-quality fastening and mandatory maximum insulation, since condensate in such structures is formed in greater quantities.

The main stages of installing a chimney for an internal gas boiler:

• marking places for making holes in the ceiling and roof of the house;
• device opening under the chimney;
• connection of the boiler pipe with the flue;
• installation of revision, tee;

• building a chimney pipe;
• reinforcement of joints with clamps;
• fixing the structure with brackets;
• thermal insulation of the outer part.

Helpful advice! The location of the chimney system must be strictly vertical, without narrowing or expanding the channel.

Chimneys for gas boilers made of stainless steel

Steel chimneys can have a single-walled and double-walled design. Single-layer chimneys can be installed in heated rooms and used to line brick chimneys. In three-layer systems, there is a heat-insulating layer between two pipes, which makes it possible to use them for both indoor and outdoor installation.

Due to the fact that sulfur impurities are contained in gas fuel, when the waste products are removed, its vapors have an aggressive effect, corroding the walls of the flue ducts. Therefore, in the production of stainless steel chimneys for gas boilers, heat-resistant and acid-resistant material AISI 316L is used. Its use greatly increases the life of chimney systems.

Of the weaknesses of the stainless chimney pipe for a gas boiler, a not entirely aesthetic appearance can be noted. The benefits include:

• resistance to corrosion and aggressive chemical composition;
• light weight, no need for a base device;
• incombustibility of the material - stainless steel does not melt even at a temperature of 500 ºС;
• modular design - factory production of a large number of tees, adapters and elbows allows you to build a chimney into any home;
• factory production of all elements of the steel chimney allows you to assemble and remove it at any convenient angle;
• absolutely smooth round inner surface - provides a minimum of obstacles in the way of the output of combustion products;
• the possibility of installation in an already built house;
• quite affordable price of a chimney for a gas boiler.

When installing an external chimney made of steel, there is a high probability of a dew point: if the outside temperature is low, the evacuated vapors form condensate and a water plug is created. It clogs the channel, preventing the products from escaping, and thereby blocks the combustion process. This can be avoided by placing the pipe in a lined chimney channel made of brickwork. This technique will also decide the aesthetic side of the structure.

Another option to avoid the formation of a water lock is to use a sandwich construction of two pipes, one of which is protected by a layer of basalt wool. Such a remote chimney system no longer needs additional insulation. The diameter of the chimney for a gas boiler is selected so that it matches the cross section of the outlet of the equipment.

Helpful advice! Stainless steel chimneys are easy to maintain, however once every 3 years it is necessary to have the system inspected by a specialist.

Rules for installing a chimney for a geyser

The key to the safe operation of a gas water heater is the correct exhaust system. Chimneys are used for the column, which output combustion products into the chimney duct or directly into the atmosphere. For the removal of exhaust gases, the following types of pipes are used:

• - easy to assemble, the flexibility of the material allows
  stretch it up to 2-3 m in length, and also lengthen it by connecting several pieces of corrugation;
• aluminum pipe - easy to install, resistant to condensate, needs additional thermal insulation;
• coaxial chimneys - the price of such systems can be reduced due to the possibility of pipe output through the wall. This reduces material consumption and installation costs. The main advantage of such a chimney is that the air from the room does not participate in the operation of all equipment.

Basic requirements for the installation of chimney pipes for gas water heaters:

• the operation of appliances is prohibited without a chimney securely fixed in it;
• draft inside the chimney system must be constant;
• pipe material must be non-combustible, resistant to corrosion, condensate and high temperatures;
• the outer section of the chimney must have a vertical arrangement;
• the design must be airtight to prevent carbon monoxide from entering the room;
• the chimney must be mounted in an open area for quick troubleshooting if necessary;
• the chimney must be located at least 0.5 m above the roof level;
• it is strictly forbidden to use ventilation systems, the space between floors, attics to remove combustion products.

How to check the draft in the chimney of a gas boiler

Draft is one of the main indicators of the correct functioning of the chimney. Its effectiveness depends on the following parameters:

• section of the chimney pipe - heated gases are removed faster with a smaller section, however, if it is too small, there is a threat of penetration of combustion products into the room. If the cross section of the chimney is unreasonably large, a reverse draft effect may be created;

• accumulation of a large amount of soot on the walls of the barrel - due to this, the working section decreases, which leads to a decrease in the rate of carbon monoxide removal;
• a large number of turns in the system - any of the turns of the pipe slows down the movement of exhaust gases;
• insufficient tightness of the chimney - the presence of small cracks, gaps contributes to the penetration of cold air into the system, which prevents the rapid removal of smoke;
• weather - high humidity and low atmospheric pressure can cause a decrease in thrust.

There are several ways to check the condition of traction. If the diagnosis is carried out by professionals, they use an anemometer - a device for measuring the speed of gases. In everyday life, they use the so-called folk methods:

• visual inspection - if there is smoke in the room, then there is a reverse draft;
• with the help of a thin sheet of paper - it is brought to the viewing window: the stronger the paper is attracted, the better the traction;
• candle flame - a lit candle is brought to the channel and the flame is blown out. The direction of smoke from an extinguished candle towards the chimney indicates good traction.

Important! Draft in gas boilers should be checked with the equipment turned off.

Depending on the reason for which weak traction is observed, measures are taken to improve it. Cleaning the channel from soot is carried out using a special device consisting of a ruff, a sinker and a rope. The device is lowered into the channel and cleaned along its entire length with translational movements. To achieve complete sealing of a brick chimney, it is necessary to eliminate all cracks resulting from the destruction of the masonry.

Coaxial chimney for a gas boiler: installation rules, advantages, installation

The main advantage of installing a coaxial chimney for a gas boiler is that such a chimney not only removes exhaust gases to the outside, but also provides the combustion chamber with air from the street. Thanks to this, the room does not need additional ventilation, and the air in the house remains able to maintain the health and performance of the people living there. Equipment with such a discharge of combustion products is called a gas boiler without a chimney.

The design of the coaxial chimney

The basis of the design of the coaxial chimney is two pipes of different diameters, one of which is inside the other. The inner pipe is designed to bring waste substances out. Through the outer pipe, or rather, through the space between the inner and outer pipes, air is taken from the outside, which is used to burn the gas. Thus, the chimney copes with several functions at once:

• increase in the degree of safety of the chimney - the incoming air from the street heats up, and the outgoing combustion products cool down;
• increase in boiler performance - the efficiency of the equipment increases due to the fact that the air enters the combustion chamber already heated;
• maximum gas combustion - due to the fact that the efficiency of the boiler increases, complete combustion of fuel is achieved;
• environmental friendliness of the heating system - the entire working cycle of gas equipment takes place outside, which ensures comfort and safety of heating.

For the manufacture of a chimney, round pipes are used: the outer pipe with a diameter of 100 mm is made of steel 1-2 mm thick, the inner pipe is made of aluminum alloy. The diameter of the latter is 60 mm. Pipes with this ratio of diameters are used in coaxial chimneys for wall-mounted gas boilers and floor-standing devices with a closed combustion chamber. To prevent the pipes from touching each other, jumpers are installed along their entire length.

According to the installation method, coaxial type chimneys can be horizontal and vertical. The horizontal version is more popular due to its easy installation. In the case when it is technically impossible to mount the system in a horizontal way or the distance from the boiler to the outer wall exceeds 4 m, they resort to installing a vertical coaxial chimney. It should be noted that its installation is more complicated.

Advantages of coaxial flue systems

Coaxial chimneys are used for various gas equipment in which the combustion chamber has a closed structure. These are floor and wall-mounted gas boilers, gas flow heaters (columns), convectors and other devices.

It is worth noting the main advantages of using coaxial chimneys over other types of flue systems:

• natural heat exchange - the heating of the incoming air and the cooling of the outgoing gases occurs due to the design of the pipe, which, in turn, does not allow the wall to become very hot;
• increase in productivity of the gas equipment itself;
• compactness - the chimney is neatly mounted and does not take up much space, which allows it to be used not only in private cottages, but also in high-rise apartments;

• safety of operation - in the air of the room where the boiler is installed, there is no lack of oxygen, since the contact of the air from the room with the excreted substances is completely excluded;
• ease of installation - allows you to reduce the cost of installing a coaxial chimney.

Helpful advice! If you have purchased a wall-mounted gas boiler for autonomous heating of an apartment, using a coaxial chimney for it is the safest, since combustion products are not removed into the ventilation duct, but directly into the atmosphere.

Requirements for installing a coaxial chimney

As with any gas equipment, the installation of coaxial chimneys is subject to specific requirements of SNiP 2.04.05–91, section 3 "Heating"; 2.04.08–87, as well as the instructions regulated by the “Safety Rules in the Gas Industry”. They can be different depending on the installation method of the coaxial chimney: horizontal or vertical.

For any type of installation, there is a general requirement for the maximum length of the coaxial chimney for a gas boiler: it cannot exceed 4 m. When it is required to carry out a chimney system at a considerable distance, special coaxial models with overall standards are used.

When passing a vertical coaxial chimney for a gas boiler through the ceiling and roof, an adapter is used, the design of which is provided by the manufacturer specifically for this system. This also applies to coaxial chimney extensions when it is required to install a system of the required length. Tightness in the places where pipes pass through the ceiling is provided by a special head - terminal. It also prevents precipitation from entering the system.

The horizontal method of installing a coaxial chimney is used, as a rule, for wall-mounted gas equipment. To avoid the ingress of condensate, it is necessary to maintain a downward slope of the chimney from the boiler, ranging from 3 to 5%. There are norms for the location of smoke channels for the chimney in the outer wall. So, if the hole is supposed to be in the wall next to the window, the distance to the window should not be less than 0.5 m, if above the window - not less than 0.25 m.

Many manufacturers of gas equipment include in the supply a pipe for the removal of combustion products. If you bought a coaxial chimney for a gas boiler along with the equipment, you need to check that the set includes a horizontal part of the pipe (usually about 1 m long), a branch, a terminal (head), a set of gaskets, a membrane. If, when installing a pipe through a wall, it is necessary to bypass any protrusions or fittings, elbows and bends are used.

Helpful advice! It is necessary to provide protection for all outputs and inputs on the coaxial chimney from foreign objects.

Coaxial chimney for a gas boiler in a private house: how to do it yourself

Before installing a coaxial chimney with your own hands, you must read the installation and operation manual for the purchased gas equipment. Due to the specific design of the coaxial pipe, the installation of a chimney for a wall-mounted gas boiler must be done with extreme caution. Avoid dents or other damage on the pipes leading to depressurization of the system.

To perform installation work, you will need the following elements of the system:

• pipe with flange;
• crimp clamps;
• coaxial elbow;
• adapter for connection to the boiler;
• extension with sealing cuffs (if required);
• decorative overlays.

According to the requirements for the installation of the chimney, a hole of the required diameter is arranged in the outer wall. If there is a window opening in the wall, it is necessary to place the opening at a distance not closer than 0.5 m from the window. When connecting a chimney to a gas boiler, first connect the adapter, and then all the links assembled into a single structure.

The pipe is brought out through a hole in the wall, observing the slope from the boiler. If it is necessary to bring the chimney to the wall, the structure is fixed with clamps. The gaps between the wall hole and the inserted pipe are blown out with foam or sealed with mineral wool. After that, these places are closed with decorative rings.

Do-it-yourself brick chimney device

The construction of a brick chimney is an exclusively vertical channel with a square or rectangular section. For laying a brick chimney, a full-bodied ceramic brick is used, which is laid on the mortar. The outer section of the channel is laid out with ordinary brick, corresponding in style to housing construction, which can be seen in numerous photos of brick chimneys. If the house is faced with stone or plastered, you can decorate the chimney in the same way.

Brick chimneys for gas boilers: installation requirements

Before laying the chimney for a brick boiler, it is necessary to build a foundation, the height of which must be at least 0.3 m. The dimensions of the base along the perimeter must protrude beyond the contour of the channel itself by at least 0.15 m. part of the outer wall, its foundation must be flush with its base. Do-it-yourself brick chimney laying (video instructions confirm this) begins at the stage of building the walls of the house.

Requirements for brick chimneys:

• the smoke channel must be vertical, without ledges, narrowed and expanded sections;
• the thickness of the masonry brick pipe for the chimney is taken taking into account the exclusion of freezing;
• the minimum allowable cross section of the chimney ducts is 14 x 14 cm, which corresponds to the size of half a brick, taking into account the seam;
• the size of the brick chimney, the height of which is less than 5 m, should be increased to a channel section of 14 x 20 cm;
• the construction of the chimney is carried out in the walls between the heated rooms, which will prevent it from cooling and reducing draft;
• tightness - the laying of a brick chimney is carried out with dressing so that the vertical seam of the previous row is blocked by the next brick;
• the inner surface of the channel must be smooth;

Helpful advice! To achieve a flat and smooth inner surface of the channel, use special templates when building a brick chimney with your own hands.

• the distance between adjacent flue ducts should not be less than 5 average outer diameters of the pipe;

• if ventilation ducts are located near the chimney, their height should be equal to the height of the chimneys.

To reduce construction costs, as many channels as possible should be located in the common chimney. In this case, the chimney and ventilation ducts located nearby will heat each other, which will generally improve the functioning of the chimney.

Preparation of mortar for laying a brick chimney

The composition of the mortar for laying a brick chimney is selected taking into account which section of the pipe is laid out: external or internal. For the construction of the external channel, the same mortar is used as for the laying of the bearing walls of housing construction. It is made from cement, sand, water and can harden in air and in water. The mixture is prepared in such a volume that it is worked out within an hour, as it sets quickly.

In order for the mixture not to be destroyed under the action of an aggressive environment, it is recommended to add special additives to it, which increase its plasticity, strength and acid resistance. Thanks to these additives, it is possible to improve the quality of the masonry itself, increase the speed of construction and the durability of the work performed.

The preparation of a mortar for a chimney from a brick passing inside the house is based on the use of refractory clay and fireclay in its composition in a ratio of 1: 1. Such mixtures do an excellent job with high temperatures, they are durable and do not emit harmful substances. To give the clay mixture strength, you can add table salt to its composition (about 120-150 g per bucket).

Helpful advice! The strength of the chimney masonry mortar can be increased by adding Portland cement in the proportion of 1 kg per bucket.

When laying a brick chimney with your own hands, you can purchase ready-made mixtures that are distinguished by heat resistance and acid resistance. Preparing the solution yourself can reduce the cost of building a chimney.

It is quite possible to build a brick chimney with your own hands - the video below will help you familiarize yourself in detail with the stages of construction, taking into account all the basic requirements.

The feasibility of using a brick chimney for a gas boiler

Given the advantages and disadvantages of brick chimneys, it is possible to draw conclusions regarding their use in combination with gas boilers. Their advantages include:

• the likelihood of using an existing chimney duct, which reduces the cost of the chimney;
• the possibility of operation in conjunction with gas equipment having an open combustion chamber;
• acceptable cost of materials for the construction and decoration of the structure.

The durability of brick channels is observed only when they are used for fireplaces or stoves. If they are used for gas boilers, due to the low temperature of the combustion products, condensate will form on the channel walls, and harsh operating conditions in an aggressive environment will lead to gradual destruction of the brickwork and deterioration in performance.

In addition, the requirements for such chimneys are more stringent:

• impeccable masonry - if skills are not enough, it will be necessary to invite a qualified bricklayer to work, which will cost a round sum. Prices for work: rough brick chimney laying from 6,000 rubles per 1 m³, facing masonry - 2,500 rubles. for 1 m²;

• the inability to perform a complex configuration of the channel (if you want to bypass, for example, a beam in the ceiling);
• the use of the old channel should be carried out using a sleeve;
• the need for thermal insulation.

The disadvantages of such a system include a decrease in traction during the heating of the brick. Thus, the correct chimney for a gas boiler will be a brick channel together with a steel or ceramic liner. The photo of brick chimneys shows that the liners are equipped during the laying of the channel. In this case, it is necessary to leave a gap between the liner pipe and the brick surface. This is necessary so that the pipe can move inside the channel.

Chimneys for gas boilers: prices for various types of pipes

When planning your budget when purchasing chimney pipes, you should take into account the length and diameter of the channel, the presence and number of turns, as well as the material from which the pipes are made. There are no fundamental differences in the design and cost of chimneys for floor gas boilers and wall-mounted appliances. A stainless steel chimney will cost more than a brick chimney, but a steel chimney is easier to install, making installation costs quite affordable.

You can buy a chimney for a gas boiler at specialized points of sale and in online stores that sell these products. A wide range of fittings, fittings, tees, adapters, plugs and other necessary construction details is also offered for sale. Given the convenient sorting of products by categories and models, you can quickly find and order the right product.

The cost of 1 m of a single-circuit stainless steel pipe with diameters of 100, 110, 115, 120 mm is 650 rubles, the same pipe with a diameter of 140-150 mm will cost 750 rubles. The price of a stainless steel elbow with an angle of rotation of 90° for a pipe with a diameter of 110-120 mm is 550 rubles. with a metal thickness of 0.6 mm. You can buy 1 m of a stainless steel sandwich pipe with a diameter of 140-230 mm for 1900 rubles.

Helpful advice! You can save on the purchase of high-quality and durable pipes for chimneys if you place an order during the discount period.

The price of a coaxial chimney for a gas boiler with a diameter of 60-100 mm and a length of 1 m, sold in a horizontal kit, is 3,500 rubles. The purchase of a coaxial chimney from Baxi, a global manufacturer of modern heating systems, will cost 4,200 rubles. A complete chimney kit for a wall-mounted gas boiler includes a pipe 75 cm long with a diameter of 60-100 mm, a 90 ° outlet and a tip. All products are guaranteed.

Competent installation of any household appliances is the key to its safe and long-term operation. Especially when it comes to gas equipment. Installation of a combustion products removal system for gas boilers requires preliminary engineering calculation and qualified implementation.

If gas is chosen for heating in the house, care should be taken to remove combustion products. This means that you need to choose and correctly install a chimney for a gas boiler. Compliance with the rules and regulations in this matter cannot be categorically neglected, since this can call into question not only the health, but also the life of the residents of the house.

One of the most dangerous products formed during almost all types of combustion is carbon monoxide. This is an insidious and very dangerous substance, the inhalation of which threatens with severe forms of poisoning.

During the operation of a gas boiler during the combustion of fuel, carbon monoxide is also formed in addition to other combustion products.

If the chimney that removes the products of combustion is not installed correctly or is damaged, this can lead to poisoning.

The danger should not be underestimated. Carbon monoxide (aka carbon monoxide) is odorless and colorless, so poisoning can occur completely unnoticed by everyone in the house.

Once in the human body, carbon monoxide molecules interact with hemoglobin. As a result, the so-called carboxyhemoglobin is formed, which prevents the entry of oxygen molecules into the tissues of the human body.

In addition, carbon monoxide can have a very bad effect on other biochemical processes in the body. There were cases when carbon monoxide poisoning was detected too late, the person simply could not be saved.

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The calculation of the chimney for a gas boiler is influenced by a number of factors: the dimensions and layout of the room in which the installation is supposed to be, the model and technical characteristics of the device, the material and design of the pipes. From non-compliance with the installation requirements, fire safety standards are violated and the operational and power qualities of the boiler deteriorate.

Coaxial chimney for a gas boiler

Formula for calculating the optimal design

The formula for calculating the parameters of the chimney combines several conditions, each of which is calculated separately, analyzed and added to the marking scheme during installation. This formula displays:

• flue gas velocity;
• chimney length;
• sectional shape of the structure;
• channel area;
• room height;
• chimney material;
• average indicators of internal and external temperature;
• How fast is free fall?
• coefficient of smoothness of pipe walls.

For example, the calculation of the pipe section (F) in m2 occurs according to the following equation:

(КхQ)/(4.19х√ˉh)=F,

in which K is a coefficient (calculated empirically), Q is an indicator of the degree of productivity of a gas boiler (power, kW, indicated in the technical data sheet of the boiler), and h is the height of the chimney.

To calculate the value of self-draught (mm water column), the effective height of the chimney is multiplied by the difference in air density with flue gas density.

Calculation formulas reveal new parameters and check the correctness of the calculation. So check the correctness of the calculations of the dimensions of the length of the chimney according to the formula:

P*L>S,

in which P is an indicator of the perimeter of the section of a square pipe, L is the chimney length parameter, S is the area of ​​\u200b\u200bthe inner surface of the pipe. For a pipe with a circular cross section, the indicator P is replaced by I. I can be calculated using the formula I \u003d 2pR, where R is the radius of the pipe.

The remaining indicators regarding the technical characteristics of the boiler, the gas supply rate to the device, which will be needed for calculations, are in the passport documentation.

Dependence of length on boiler power and pipe section

Pipe Material Requirements

In addition to air supply to the burner and good draft, the chimney exhibits:

• resistance to corrosion;
• endurance under the influence of extreme temperatures;
• coating resistance to aggressive chemical environments.

The indicators of these quantities are taken into account in the calculations, affect the choice of chimney material and the features of the gas boiler. So the combustion products emitted by the device are at a low temperature (about 150 ° C compared to 300-600 degrees for solid fuel boilers) and the rate of their output through the chimney is also low. The smoke has time to cool down faster than it reaches the dew point mark, and forms condensate inside the chimney. Therefore, to calculate the dew point, the important quantities are:

• water vapor density in combustion products;
• fuel composition and moisture content;
• excess air and temperature in the coefficient.

In addition, information on technical data, materials and design of pipes can provide high performance to the chimney. The most preferred are:

• ceramic;
• steel (sandwich pipes);
• condensation.

It is impossible to use a brick chimney for a gas boiler: it poorly resists condensate and collapses under its action, is not airtight and provokes leakage of combustion products. It is undesirable to use pipes with a square section, they are inconvenient to use, accumulate soot, and distort the operation of the boiler. The optimal shape is a circle or oval with smooth inner walls.

sandwich tube

Installation location value

There is a difference between where the boiler is installed. The chimney is calculated for installation:

• in a private house;
• apartment building.

For private housing, vertical natural air circulation, forced draft are used. Another option for removing combustion products is to install a chimney with an outlet through the wall (coaxial). For an apartment in a multi-storey building, the use of a horizontal gas outlet is allowed.

Depending on the area of ​​the room:

• if the dimensions of the room are less than 80-100 m2, it is recommended to install bends with forced draft for them;
• in rooms with an area of ​​more than 100 m2, a natural and forced system for the removal of combustion products is used.

Boiler device in a private house

How does the calculation affect the installation work

It is important to calculate the chimney for installation, since this stage is fundamental and work begins with it. In addition to these nuances, several more points are put forward by the requirements of SNiP, which are taken into account when the combustion products are removed during installation. These include:

• 2 gas channels can be connected to one chimney at a distance of at least 750 mm;
• when assembling the pipe, a minimum number of narrowings, bends and horizontal sections is allowed (no more than 3 on one vertical riser), otherwise the draft will be disturbed;
• the cross-sectional diameter corresponds to the dimensions of the outlet channel of the branch pipe located on the gas boiler;
• the drainage system is made from a height of 5 meters and is insulated with insulating materials, the joints are treated with sealants;
• vertical deviations in the removal device are allowed no more than 30%;
• at the bottom is a condensate collector.

Norms for the location of chimneys relative to their height

Alternative calculation methods

Even when using the correct calculations, gas boilers are operated correctly: they do not overheat, they are not set to maximum power, they are cleaned once a year. It is recommended to rely on the help of professionals in cleaning, installation and calculations.

They use consultations in the centers where a gas boiler is purchased, which will provide detailed information with the installation requirements of the selected model, or resort to free online programs for quick calculation of chimney parameters (for example, EN13384, JEREMIAS).

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Installation of boiler equipment and its efficient operation is impossible without a chimney.

The right choice of materials, compliance with the rules when connecting is the key to your safety.

Gas services strictly control the commissioning process, they can fine violators or forcibly disconnect the user from gas supply.

Basic requirements for materials:

• fire resistance;
• anti-corrosion properties;
• resistance to acid, formed as a result of the interaction of condensate with combustion products;
• long period of use.

Brick chimney. It has low thrust and is prone to rapid destruction due to the formation of abundant condensate on the surface, which turns into an ice crust during the cold season. Ideal only for fireplaces or as a kind of stainless steel chimney cover.

stainless steel. It has a lot of advantages, which makes it one of the first in popularity among its fellows. It has good traction, fire resistance and anti-corrosion, long service life (especially double-circuit models). The modular assembly method allows you to create steel chimneys of various configurations and is accessible even to a non-professional. Compatible with high power boilers. Will serve you 15 years.

Chimneys made of galvanized steel behave much worse during use. Galvanized is prone to rust.

The service life is a maximum of 5 years.

Ceramic chimney. Outwardly, it is as massive as a brick one. Installation option - only strictly vertical. Austrian manufacturers have developed models of ceramic chimneys with an external contour not only from ceramics, but also from metal. They are much lighter, but during their installation it is necessary to calculate the load on the foundation and walls. Warranty up to 30 years.

Asbestos cement pipes. Short service life (5 years), installation complexity, environmental friendliness. Even the low price of the material cannot be a good reason for choosing such a chimney. From overheating, the pipe can simply break. As an option for occasional use in the country is suitable.

coaxial- made of aluminum in the form of two sandwich tubes with different diameters, located one inside the other. The outer one is designed for air supply, and the inner one is for removing combustion products. Team structure. The arrangement is most often horizontal.

Advantages of a coaxial chimney:

• Safety
• Increased efficiency of the heating system
• Environmental friendliness

Chimney elements

Regardless of the material, the design includes the following elements:

1. Tee with revision- a condensate fitting is installed at the bottom of the tee
2. Adapter for connecting the pipe of the gas boiler and the chimney
3. Mounts- brackets and clamps
4. cone tip
5. Elbows- they are installed no further than 2 meters from the beginning, otherwise the boiler draft is reduced;
6. spigot
7. Telescopic tubes

Size Requirements

• smoke channel should not contain ledges and be located strictly vertically. With a narrower section, there is a significant decrease in thrust, and when using pipes with a large diameter, blowing into the boiler chamber is possible, with its subsequent attenuation.
• Cross-sectional area of ​​the flue pipe must not be smaller than the area of ​​the branch pipe with which the chimney is connected to the boiler.

How to calculate the diameter of the chimney

Key parameters- cross-sectional area (outlet F cm2).

The calculation is made according to the formula F = (K ∙ Q) / (4.19 ∙ √ˉ H), Where:

K- coefficient calculated empirically (0.02-0.03);

Q- performance indicator of the gas appliance (indicated in the technical characteristics of the boiler);

H- chimney height.

The resulting number is adjusted by building codes and regulations.

For example, if a brick is used, then the cross section is 0.5 x 0.5 of the material.
With asbestos cement - a diameter of at least 10 cm.

Round chimney diameter with a boiler power of 24 kW, it should be 120 mm, 30 kW - 130 mm, 45 kW - 170 mm, 55 kW - 190 mm, 80 kW - 220 mm and 100 kW - 230 mm.
The minimum cross section of rectangular ducts depends on the heat output of the boiler:

• Up to 3.5 kW - 14 by 14 cm.
• 3.5 to 5.2 kW - 14 by 20 cm.
• From 5.2 to 7.3 kW - 14 by 27 cm.

Device rules for boilers with natural exhaust of combustion products

• • The chimney must be located above the roof ridge, at least 0.5 meters above it, provided that its axis is close to the ridge or parapet (less than 1 m and not more than 1.5 m).
  • If the pipe is located further from the ridge (from 1.5 m to 3 m), then its height should be flush with the ridge.
  • When the chimney is located at a distance of more than 3 m, its height must not exceed the boundary of the line laid down from the ridge at an angle of 10 ° to the horizontal.
  • With a flat roof, the height of your chimney should also have a minimum limit of 0.5 m, and in the case of a combined roof, 2 m.

A smoke exhaust pipe outside the building cannot be erected without insulation: the resulting condensate will destroy the chimney.

• The system for ejection of combustion products must be fixed to the wall with a gap of no more than 2.5 meters, in areas with a slope - every 1.5 meters.
• clamp must be used on any connecting section of the insulated chimney.
• Chimney elbow must have a slope angle of at least 15 ° and not more than 90 ° (no more than three rotary elbows in the system are allowed). The vertical section following the turn must be clearly fixed with a mount. It is forbidden to load the inclined sections of the pipe or its branches.

• It is obligatory to equip the chimney with a condensate drain, which must be available for maintenance.
• The chimney must be isolated from flammable materials using brickwork or asbestos board. The distance from the connecting pipe to flammable surfaces must be at least 25 cm, and if a protective layer is applied, from 10 to 5 cm.
• Stable traction can be provided if the pipe is erected above the zone of wind backwater.

• Smoke exhaust systems built inside the building do not need to be additionally insulated, but it is necessary to take care of the tightness and the ventilation system. Poisonous smoke can easily seep even through the brickwork of the protective casing.
• The areas located outside the building are insulated. In the absence of thermal insulation, the gases cool rapidly, the draft decreases, and the boiler power drops. Condensation forms on the walls.

Requirements for the installation of coaxial chimneys

When installing the smoke channel of such boilers, it must be borne in mind that:

• When the length of the coaxial pipe is not more than 1 meter, it is required to install a converging diaphragm on the air duct. The power of the fan in the chimney is designed for a certain length of the pipe and, if it is less, there will be a loss of draft with all the ensuing consequences.
• The pipe is located in a horizontal plane, but still should have a slope of 1 cm per meter of total length and no more than two knees.
• pipe head can protrude outward no more than the length of its tip - to protect against freezing, and not lower than 2 meters from the ground.

What do SNiPs say

The device of chimneys for gas boilers is regulated SNiP 2.04.05-91, and DBN V.2.5-20-2001

Subject to all the requirements during the installation work, you can be sure that the gas service specialists will not have any questions for you. On cold winter evenings, your family will be warm and safe.

For information on how to choose and install a chimney, see the video:

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How to make a chimney calculation - 4 important points to consider when installing a chimney

To heat private houses in the cold season, most often they use either ordinary brick stoves and fireplaces, or household heating boilers for solid, liquid or gaseous fuels. An indispensable condition for the normal operation of such heaters is the free flow of a sufficient amount of fresh air into the flame combustion zone, and the rapid removal of spent fuel combustion products into the atmosphere. To ensure compliance with these conditions, before installing the stove chimney, it is very important to perform a competent calculation of the chimney with natural draft, since not only the efficiency of the heating devices, but also the safety of the residents of a private house will depend on this.

Due to what natural draft is formed in the furnace

Most heating and cooking stoves and boilers for autonomous heating are not equipped with a system of forced fresh air intake and removal of exhaust flue gases, so the process of fuel combustion in them directly depends on the presence of natural draft in the chimney pipe.

Theoretically, the method for calculating the chimney is quite simple. To make it clear to the reader where natural thrust comes from, then I will try to briefly explain the physics of thermal and gas-dynamic processes that occur in the furnace during fuel combustion.

1. The furnace chimney is always installed vertically (with the exception of certain horizontal or inclined sections). Its channel starts at the top of the firebox vault, and ends on the street, at some elevation above the roof of the house;

1. Hot flue gases in the fuel combustion zone have a very high temperature (up to 1000 ° C), therefore, according to the laws of physics, they quickly rush upwards;
2. Rising up the chimney at a speed of about two meters per second, the flue gases create an area of ​​​​low pressure in the furnace;
3. Due to the natural rarefaction in the furnace, fresh air is supplied through the blower and the grate into the flame burning zone;
4. Thus, it is easy to understand that for the formation of good natural traction, several conditions must be met at once:

• The chimney must be located strictly vertically. In addition, the ode should be of sufficient height and as straight as possible, without unnecessary bends and turns at an angle of more than 45 °.

• The internal section of the smoke channel must be designed in such a way that it allows the entire volume of flue gases that are formed during the combustion of fuel to freely pass into the atmosphere;
• In order not to create significant aerodynamic resistance to the movement of smoke, the inner walls of the pipe should have the most even and smooth surface with a minimum number of transitions and joints;
• As you move along the pipe, the flue gases gradually cool down, which leads to an increase in their density, and a tendency to form. To prevent this from happening the chimney pipe must be well insulated.

A significant positive effect on the force of natural traction is exerted by the wind on the street. This is due to the fact that a continuous flow of air directed perpendicular to the axis of the chimney creates a reduced pressure in it. Therefore, in windy weather, good draft in the furnace is always observed.

Moment 1. The choice of material and design of the chimney

The normative and technical construction documentation does not stipulate any strict requirements for the arrangement of furnace chimneys, so each homeowner makes a chimney at his discretion. At the same time, I must say that all types of chimneys differ from each other not only in terms of design and external features, but also in terms of heat engineering, weight and gas-dynamic characteristics.

1. The masonry chimney is characterized by high strength and durability, it can withstand long-term exposure to high temperatures, but it is poorly resistant to aggressive smoke condensate. Due to the massive brick walls, it has a high heat capacity and satisfactory thermal insulation properties. As for the issue of water vapor condensation and gas dynamics of a brick chimney, not everything is so good here.

• Massive brick chimney has significant weight, therefore, its installation requires its own foundation, which, in turn, also requires separate calculations;

• The rectangular or square cross-sectional shape of the flue ducts, combined with uneven and rough inner walls, creates significant resistance to the movement of flue gases, so the cross section of such chimneys should be selected with a small margin;
• Lack of additional thermal insulation can lead to condensation inside the chimney, therefore, its walls must be of sufficient thickness so that the temperature of the flue gases inside does not fall below the dew point.

1. Asbestos-cement and ceramic pipes are sold ready-made and are easy to install with your own hands, so they are often used in the construction of private houses to connect gas or solid fuel boilers. Many homeowners are attracted by their not very low price, but I want to remind you that when installing a chimney from asbestos-cement pipes, the following points should be taken into account:

• Asbestos-cement pipes have high thermal conductivity and do not retain the heat of flue gases well., due to which condensation can form inside, which will quickly lead to the destruction of the walls;
• To prevent this from happening, when installing an asbestos-cement chimney, it is important to choose the right heat-insulating material and calculate its thickness so that the temperature of the flue gases at the outlet does not fall below 110 ° C;
• At temperatures above 350° C, asbestos cement can crack and break down, therefore, between the inlet pipe of the chimney and the outlet pipe of the boiler, I advise you to install a remote spacer from an insulated metal pipe;
• Its length should be calculated in such a way that the temperature of the flue gases at the inlet to the asbestos-cement pipe does not exceed 300-350 ° C;
• Asbestos-cement pipe, in itself, has sufficient rigidity. Despite this, for better thermal insulation and protection against mechanical damage, I recommend installing such a chimney inside a protective jacket made of brickwork half a brick thick.

1. Stainless steel metal sandwich pipes, in my opinion, are the most successful option for a home chimney, which is equally well suited for both a massive brick slab and a modern compact heating boiler. They are recruited from separate sections, so they allow you to make an external or internal chimney of almost any configuration with your own hands.

• The inner sleeve made of heat-resistant stainless steel has a perfectly smooth surface and a round cross-section, therefore creating a minimum aerodynamic resistance to the flow of flue gases. For this reason, the internal diameter of the smoke channel must correspond to the minimum value of the design characteristics;

• Insulated metal sandwich pipe has good thermal insulation properties, and does not need additional insulation, therefore, heat engineering calculations, in this case, are not necessary;
• When installing and assembling the chimney, each section must be mounted in such a way that it is attached to the inner wall or facade of the building at least in two points. In this case, the distance between the mounting brackets should be no more than 1200 mm.

1. Prefabricated insulated ceramic chimneys have similar characteristics, and can also be used almost without restrictions, in combination with any type of stove, fireplace or domestic heating boiler.

• They are designed and manufactured in the factory, in compliance with all necessary heat engineering calculations and the requirements of fire safety rules;
• This makes it possible to mount them in the form in which they are, without thinking about your own additional calculations;
• Despite this, I want to remind you that such a sandwich made of expanded clay concrete blocks, mineral wool insulation and a ceramic pipe insert, as an assembly, can have a lot of weight, so it is also necessary to calculate and make a separate foundation for it.

1. Recently, a relatively new type of polymer chimney, better known under the trade name "Furan Flex", has begun to appear on the building materials market. It is a flexible reinforced hose that is installed in an existing smoke channel and then filled with high pressure hot steam. Under the action of pressure and high temperature, the sleeve straightens and polymerizes, as a result of which it completely fills the lumen of the smoke channel, and strengthens the pipe walls from the inside.

• Installation of such a polymer insert requires the use of special equipment. and strict observance of technological regimes, therefore, it can be performed exclusively by qualified specialists;
• Based on this, in this case, I do not recommend filling your head with complex formulas, and entrusting the performance of all calculations to the engineers of the contracting organization that will perform the installation.

The asbestos-cement pipe has a rough inner surface, which contributes to the rapid adherence of soot and soot. Over time, the growing layer of soot reduces the internal sectional area and increases the aerodynamic resistance of the smoke channel, so I do not recommend using such pipes for stoves and boilers for solid and liquid fuels.

Moment 2. Calculation of the inner diameter of the chimney for solid fuel stoves and fireplaces

In order to perform a correct calculation of the chimney draft, it is first necessary to determine the required internal cross-sectional area. In this section, I will tell you how this is done, using the example of calculating the cross section of a chimney for heating stoves and solid fuel fireplaces.

1. First of all, it is necessary to determine what volume of flue gases will be produced when a certain type of fuel is burned in a furnace in one hour. Such a calculation is performed according to the following formula:

V gas \u003d V * V fuel * (1 + T / 273) / 3600, Where

• V gas- the volume of flue gas that will pass through the pipe in one hour (m³ / hour);

• B- the maximum mass of fuel that burns within one hour in the furnace (kg);

• V fuel- coefficient of the volume of flue gases that are emitted during the combustion of a certain type of fuel (m³ / kg).

• This value is determined according to special tables, and its value is: for dry firewood and lump peat - 10 m³ / kg, for briquetted brown coal - 12 m³ / kg, and for hard coal and anthracite - 17 m³ / kg;

• T– flue gas temperature at the outlet of the pipe (°C). With a normally insulated chimney, its value can be from 110 to 160°C.

1. Having the obtained value of the total volume of gas passing through the pipe per unit time, it will not be difficult to calculate the required cross-sectional area of ​​​​the chimney channel. It is defined as the ratio of the received volume to the flue gas velocity, and is calculated using the following formula:

S smoke = V gas / W, Where

• S smoke- cross-sectional area of ​​the smoke channel (m²);
• V gas- the volume of flue gases per unit of time, which we received in the previous formula (m³ / hour);
• W is the reduced velocity of the upward movement of the gas-smoke flow inside the pipe (m/s). Here I must say that this is a conditionally constant value, and its value is 2 m/s.

1. In order to understand what pipe diameter we need to make a chimney, based on the obtained value of the circle area, we need to determine its diameter. For this, the following formula is applied:

D = √ 4 * S smoke / π, Where

• D- the inner diameter of the round chimney pipe (m);
• S smoke- the area of ​​​​the internal section of the chimney obtained in the previous calculations (m²)

To make it clear to the reader, I propose to consider a simple example of calculating a chimney for a stove, if it is known that during heating, 8 kg of dry firewood burns in it per hour, and the temperature of the flue gases at the outlet is 140 ° C.

1. According to the first formula given, we determine the maximum amount of smoke that can be released in one hour of burning 8 kg of dry firewood: V gas = 8 * 10 * (1 + 140 / 273) / 3600 = 0.033 m³/hour;
2. According to the second formula, you need to calculate the required cross-sectional area of ​​​​the smoke channel: S smoke = 0.034 / 2 = 0.017 m²;
3. The last formula allows you to determine the desired diameter of the pipe, based on the known area of ​​\u200b\u200bits cross section: D = √4 * 0.017 / 3.14 = 0.147 m;
4. Thus, we determined that for this furnace, a chimney with an inner diameter of at least 150 mm is required for the bath.

If during the calculations you get a non-integer number, then I advise you to round it up to an integer value, but such rounding is allowed within reasonable limits, because in this case, a very large diameter does not mean very good.

Moment 3. Calculation of the chimney pipe for domestic boilers

In this article, I deliberately did not give separate calculations for factory-made household solid fuel and gas boilers, since any instruction for the use of boiler equipment already contains all the necessary technical information.

Knowing the nameplate thermal power of your gas boiler, it is easy to choose the diameter of the chimney, in accordance with pre-calculated parameters.

1. For small heating boilers with a maximum heat output of not more than 3.5 kW, pipes with an inner diameter of 140-150 mm will suffice;

1. For household boiler equipment of medium power (from 3.5 to 5 kW), chimneys with a diameter of 140 to 200 mm will be required;
2. If the power of the heating boiler is from 5 to 10 kW, then pipes with a diameter of 200 to 300 mm will need to be used for it.

If the gas boiler is equipped with a built-in turbine to create forced draft, then the diameter of the exhaust pipe can be much smaller than the above values. In this case, the recommended pipe size must be indicated in the product data sheet.

Moment 4. Determining the height of the pipe and the location on the roof

The strength of natural draft largely depends on the height difference between the level of the grate of the firebox in the lower part of the furnace, and the wind deflector or the mouth of the smoke channel in the upper part of the chimney.

In order for the heated flue gases to use their energy as efficiently as possible to create natural draft, it is very important to correctly calculate the height of the chimney relative to the grate and relative to the roof ridge.

1. The relative height of the furnace chimney, from the level of the grate to the mouth of the chimney, must be at least 5000 mm;

1. On residential buildings with an exploitable flat roof, the mouth of the chimney must be located at least 500 mm higher than the maximum height of the side parapet or roof railing;
2. On houses with a gable or hip sloping roof, the mouth of the chimney must be located no lower than 500 mm from the level of the roof ridge;
3. If on a sloping roof the chimney is located on one of the slopes, at a distance no further than 1500 mm from the roof ridge, then it must also rise 500 mm above the level of the ridge;

1. In the event that this distance is from 1500 to 3000 mm, the smoker's wind deflector can be located at the level of the roof ridge;
2. On gently sloping roofs with a small slope angle, the chimney can be located at a distance of more than 3000 mm from the ridge. In this case, its optimal height is calculated in accordance with the diagram in the figure below.

Incorrect choice of the height of the pipe or its location relative to the roof ridge, with an unfavorable wind direction, can cause the formation of reverse thrust. This phenomenon is very dangerous, since it can lead to the release of burning coals and poisonous carbon monoxide from the blower or firebox into the living space.

Conclusion

Summing up, I want to note that when choosing materials, dimensions and configuration of the chimney, first of all, one should proceed from the maximum heat output of the heater. At the same time, you also need to take into account your financial capabilities, and what types of fuel your stove or heating boiler is designed for.

You can learn more about all the described types of chimneys from the attached video in this article, and if you have any questions or comments, I suggest discussing them in the comment form.

September 14, 2016

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