Choosing the optimal chimney for gas boiler– not an easy, but quite achievable task. After all, you want it to be an extremely simple design to install and operate, and also with high efficiency. The coaxial type meets all the requirements, the installation of which can become a bit of a “snag”. Do you agree?

We'll help you figure it out complex issues. We provide site visitors with extensive information about the rules for constructing a coaxial chimney, about the selection and arrangement of the optimal option. Here you will find valuable tips on decorating sections of canals laid inside houses.

The article we have proposed describes in detail the standards for installing a coaxial chimney. Given useful diagrams for its proper assembly and installation. The information is confirmed and supplemented by photo collections and video tutorials.

In the family of devices for removing combustion products, the coaxial chimney stands apart. This modern design much more efficient and safer than a conventional chimney. This system is ideal for boilers with closed camera combustion.

To make a coaxial chimney, you need to take two pipes different diameters and place the narrow pipe inside the wide one. You also need to connect the inside of the wide pipe and the outside of the narrow pipe with special jumpers so that the central axes of both pipes coincide. Well, the coaxial chimney is ready.

In practice, such a design is, of course, easier and more reliable to buy than to make. The cost of a coaxial chimney will be higher than the price of an ordinary pipe made of of stainless steel, but the costs will be fully recouped.

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• In air-flue systems for boilers that have a combustion chamber closed type, usually use coaxial channels. Combustion products are discharged through the inner pipe, and oxygen is supplied into the combustion chamber through the outer pipe. Such steel structures are much more convenient and cheaper than their ceramic counterparts.

  This chimney is equipped with two pipes: one for supplying fresh air from the street, the other for smoke exit. That is, this system is completely closed and air from the room does not participate in the operation of the boiler. By the way, it is not necessary that the exhaust and supply of air be carried out through a chimney, which is divided into two parts - there are also models with separate pipes. Horizontal is often used, although vertical can also be done if necessary.

  Coaxial chimney design: what advantages does it provide?

  The principle of its operation is as follows: through the external pipe, oxygen necessary for gas combustion penetrates into the system, and the combustion products are removed to the outside through the exhaust (internal) pipe. With the help of such a design it is possible to solve several issues simultaneously:

  • When cold air passes through outer pipe it warms up from the exhaust, which leads to an increase in the efficiency of the heating unit.
  • A high efficiency index leads to complete combustion of gas, increasing the environmental friendliness of heating equipment.
  • The internal channel, which is heated by the smoke coming up, cools the cold one going down through the outer channel, which contributes to an increase in fire safety chimney
  • The closed combustion system makes the heated room more comfortable and requires installation additional ventilation No.
  • Installation and installation of components takes place without additional structures, as well as overly complex operations.
  • Installing a chimney does not require multi-meter pipes on the roof. The channel is led out through the wall.
  • This technique can be used for boilers operating on gas, solid and liquid fuel. Combustion products, moisture-containing and dry, are removed without problems through such a dual-circuit module.
  • For a heating unit of any power, you can select a chimney with the required pipe diameter.
  • Installing a coaxial chimney takes up less usable living space than a conventional one. Its components are significantly, several times, lighter than standard ones and do not require any base. Considering the thickness of the walls (up to 0.8 mm), they quickly heat up to operating temperature– 250°. This helps to minimize the amount of condensate.

  The smoke exhaust duct will work efficiently only if it is correct location. The peculiarity of this type of system is that it can be installed both vertically and horizontally.

  • a standard vertical coaxial chimney is longer and more difficult to install,
  • horizontal air vent, in contrast, is more practical and cheaper,
  • There are also combined option, when air enters from the street through a short horizontal circuit and is discharged, respectively, through a vertical one.

  How to install correctly according to requirements
  

  Such structures can be assembled with your own hands, of course, if you know in detail how to install.

  Requirements
  

  The installation of the chimney takes place in accordance with SNiP and the rules specified in the instructions and technical documentation.

  • The pressure of the supplied natural gas should not be more than 0.03 kgf/cm2 (0.003 MPa).
  • The gas pipeline is introduced directly into the room in which the heating unit is located.
  • It is allowed to exhaust flue gases through the external walls of the building (for boilers with a power of up to 30 kW).

  Installation diagram: maximum length and other nuances

  Before starting work, calculations are performed, in which it should be taken into account that

  • the length of the coaxial chimney, unless there are special instructions in the instructions, starts from five meters, and horizontal sections - no more than one meter,
  • The height of the chimney should not be higher than the ridge of the roof.

  Even if the boiler is located at a considerable distance from the outer wall, the installation issue is resolved quite simply, since extending the coaxial chimney (up to 3 meters) is very simple - for this you need a special extension cord.

  Installation similar systems carried out using bell technology. High-quality sealing of joints using heat-resistant rubber prevents the penetration of combustion products into the room. That is, they are not only effective and practical, but also safe for the health of users.

  Installation of external coaxial chimney

  The external version of the design is used for finished buildings that do not have heating.

  • First, determine the correct location of the heating system and the beginning of the chimney inlet, and make markings. The heating equipment itself can be installed later.
  • Adhering to fire safety standards, open the hole for the pipe outlet.
  • Areas with low heat resistance are insulated using special means, then remove the pipe.

  

  • The heating unit is connected to the chimney using a single-circuit sectional elbow, and subsequently, a double-circuit tee.
  • In the vertical direction, the chimney is fixed using a tee with a removable slope, and securely fastened to the wall with brackets.

  Installation of internal
  

  • A boiler with a chimney is connected to the equipment using a tee, pipe or elbow.

  On a note

  The diameter of the outlet of the heating device should be no wider than the diameter of the chimney itself.

  • When installing dual-circuit systems, an additional adapter unit is used.
  • The joints with other nodes are rigidly fastened with clamps.
  • Which elements will be needed depends on the location of the outlet pipe - on the side or at the top.

  

  • In the first case, horizontal assembly is carried out, having previously installed an adapter. The outlet should be located approximately 1.5 or higher than the level at which the pipe exits the boiler.

  If the installation is carried out in regions with heavy precipitation, it is located at such a distance from the surface of the earth that snow, hail, etc. do not get into the chimney.

  • The outer pipe should have a slight slope when exiting. This will allow the condensate to flow down by gravity. Decorative overlays on the wall to protect the holes from closing.
  • It is easier to remove the chimney if the outlet pipe is located at the top.
  • Using various brackets, the structure is brought into a vertical position.
  • If during installation it is necessary to bypass an obstacle, say, a beam, the direction of installation is changed. Before installation, select the desired elbow, and to increase the deviation, if necessary, even two.
  • When passing through the roof, special pipes are used to ensure fire safety. An air gap is left between the ceiling and the chimney and mineral non-combustible insulation is attached. The chimney outlet is completely sealed. The joint is securely covered with a special apron.

  Do-it-yourself installation of a coaxial chimney for a gas boiler is often done to optimize the functioning of the heating system. If it does not run on electricity, it must require smoke removal. Previously, standard chimneys were used for this, but today more advanced devices have appeared.

  What is a coaxial chimney

  Construction involves placing one object inside another. A similar chimney is made in the form of a double-circuit product. As building material pipes of different diameters are used. Such “structures” are divided into several types:

  1. External and internal. Devices are divided into these categories depending on their location. The first type is placed outside the building and fixed with special brackets directly to the facade. Distinctive feature appearance is convenience during installation and use. Internal types chimneys are installed in pre-prepared shafts. This type is quite difficult to install and maintain; moreover, strict adherence to safety precautions is required.
  2. Uninsulated and insulated. The second option is useful in the cold season, when the channel responsible for the entry of air masses into the system freezes with a high degree of probability. This leads to a reduction in the supply of oxygen to the combustion chamber, which reduces the efficiency of heating equipment. Insulated systems are able to ensure the functioning of the boiler even in extreme conditions. low temperatures. This type differs from a conventional chimney in the presence additional pipe, and the system consists of elements nested within each other. The space is filled with any type of insulation.
  3. Collective and individual. The second type is used when it comes to servicing one boiler. She represents simple design no branches. When it is necessary to ensure the removal of combustion products generated during the operation of several heating units, a collective type of chimney is used. It is a mine system with several branches.

  Each of the described varieties has its own characteristics and scope. Before installing one type or another, it is recommended to study in detail all the information about them.

  Components for a coaxial chimney can be purchased in specialized stores

  Design and principle of operation

  The design of such a device allows it to perform several functions, that is, to provide a stable flow of oxygen to “stimulate” the flame in the firebox and remove smoke. The device includes several modules, which include:

  1. Straight pipes. They are used to construct the main building.
  2. Decorative linings, which are flanges that cover the places where the chimney trunk passes through building structures.
  3. Tees that become part of the system if combustion products need to be removed from several heating units at once.
  4. Seals (are devices that ensure complete tightness of the housing at the points of passage through the wall).
  5. Connecting devices. They are 90° and 45° bends or couplings.
  6. Reinforcing elements, which include clamps and brackets.
  7. Devices designed to remove condensate. This structural element is located on vertical sections and is equipped with a water shutter that does not allow air pressure to decrease.
  8. Adapters. They are needed to connect the chimney system to the boiler.
  9. Components equipped with a special hole. Such a “viewing window” is needed to diagnose and remove contaminants from the chimney.
  10. Nozzles They are needed for the timely removal of smoky masses and air intake from the street.

  Functioning consists of external intake of air masses from the street through an external channel. While moving through the pipeline, the air is heated due to contact with the channel inside a special shaft for “transporting” smoke masses. Heated oxygen enters the firebox, which increases efficiency and reduces gas fuel consumption during boiler operation.

  It is important! The channel on the outside plays the role of a cooling device that lowers the temperature on the surface of the pipeline. Thanks to this, the chimney similar variety can be installed in a private (wooden) building without taking serious measures to ensure safety (fire safety).

  As mentioned above, the internal channel provides “transportation” of smoke masses. It is often equipped with special insulation, which makes it possible to increase traction in vertical structures. This type has three channels, one of them is intended for filling with basalt-based insulation. To ensure smooth operation homemade chimney, it is required to make calculations in advance and carry out the installation efficiently, taking into account the structural features.

  Chimney installation diagram

  Advantages and disadvantages

  The main advantage of the coaxial type chimney exhaust is that the air masses used in the operation of the boiler are taken not from the room, but from open air. This eliminates the need to create a powerful ventilation system; moreover, even a small room is suitable for use as a boiler room in such a situation.

  In addition to the described feature, positive aspects Similar devices include:

  1. High installation speed. The design of the chimney cannot be called complex, so installation can be done independently (it is not necessary to involve specialists and pay for their services).
  2. Possibility of use for removal of combustion products from the boiler room apartment building.
  3. Possibility of use to increase the operating efficiency of almost any type of heating equipment.
  4. A good indicator of traction, which is observed if the installation work is done efficiently.

  Thanks to the listed positive aspects, the coaxial chimney is popular among large quantity of people. In addition to the benefits, two-channel chimneys have a number of disadvantages.

  These include:

  1. The need to coordinate installation with the sanitary and epidemiological inspection service. This is due to the fact that during operation a lot of toxic condensate is released. Pouring this substance onto the ground is strictly prohibited, and disposal must be done in specially designated areas. However, if you use this type of chimney in a private house, then all claims will be reduced to the individual wishes of its owners. But when installing collective systems, obtaining permission from the service mentioned above is a prerequisite.
  2. The need to organize pipe insulation from coaxial condensate. Even small errors made during installation will lead to icing of the outlet, which will cause a decrease in traction.

  Despite the described disadvantages, chimney systems of this type are often installed both in private houses, cottages or dachas, and in multi-apartment buildings. However, the installation procedure must be treated with maximum responsibility and attention. This will help avoid unnecessary expenses in the future.

  Moreover, installation errors can lead to deformation of the chimney pipes during operation. Some problems can be solved by specialists, but if problems are ignored for a long time, it may be necessary to purchase new system and its installation.

  The diagram clearly shows how a coaxial chimney works

  Do-it-yourself installation of a coaxial chimney for a gas boiler

  There is nothing complicated in the installation algorithm, but there are features that have a significant impact on the functioning of the system in the future. Before purchasing a ready-made chimney system, you need to carefully study the diameter of the pipeline that will connect to the boiler.

  It is important! SNiP requirements play an important role in installation and further operation. Their observance is prerequisite, since neglect of such rules can lead not only to problems with sanitary and epidemiological supervision, but also to accidents.

  Regulatory requirements SNiP

  The rules for installing chimneys for a gas boiler, as well as the relevant standards established by the state, are described in detail in SNiP 2.04.08-87 and 2.04.05-91. Compilation individual projects, calculation procedures and installation are carried out in accordance with them. Violation of these rules will lead to failure of the gas service and will make legal installation impossible. SNiP is regulated by:

  1. Placement of the chimney on the facade. The head should be located at least two meters from the ground. The size of the hole in the wall should be 1 cm larger than the diameter of the chimney for a brick wall and 5 cm for a wooden wall.
  2. Maintenance. It should be carried out at the beginning and end of the heating season. It is necessary to remove condensation and check joints for leaks.
  3. The use of such systems in MKD. The structure should be mounted at least half a meter from the door and window openings. There should be at least 1 m to the window above the pipe.
  4. Installation. The chimney pipe must be at least 30 cm from the wall. If we are talking about turbocharged boilers - from 1 m. A constricting diaphragm must be installed, which is required to limit the flow of air into the closed combustion chamber.
  5. Fire safety standards. Minimum clearance between the chimney pipe and wooden wall should be 5 cm. This is due to the fact that during operation outer surface practically not subject to heating. Non-combustible materials must be placed between the wall and the pipeline. The best option is basalt insulation. The chimney pipe must be located at least 1.5 m from the windows and doors of neighboring houses. There should be no pillars, trees or other objects in this gap. It is prohibited to use a standard chimney to remove combustion products (only coaxial varieties).
  6. Restrictions on output through the facade. The ban on draining condensate onto the ground must be observed. Therefore, the pipeline must be installed at an angle to the boiler. If the design includes a special device designed to drain condensate, then a slope of the outlet pipe towards the ground is allowed (for the purpose of draining rainwater). If we are talking about using a collective type of chimney, then issues of condensate disposal must be coordinated with the sanitary and epidemiological inspection service.
  7. Features of each type of chimney system. It can be horizontal or vertical. It is strictly prohibited to connect to the same network of chimneys with forced and natural types of removal of combustion products.
  8. Features of laying a horizontal section. Laying through an adjacent room not intended for human habitation is allowed if the length of the pipeline section that will pass through it does not exceed 3 m. If we are talking about a turbocharged system with forced removal of combustion products, then it is allowed to increase the section of the pipe passing through non-residential premises, up to 5 m.

  The safety requirements described may change over time, so before you begin, installation work specialist advice is required.

  Requirements sanitary standards and rules for distances between objects

  We carry out the installation

  If you need to install the chimney yourself internal variety, then all actions are performed in the following sequence:

  1. Check that the dimensions of the boiler pipe and the chimney pipe match.
  2. Prepare a hole through which the pipeline will be led out. Its diameter must be made slightly larger than that of the pipeline.
  3. Connect the corresponding element of the smoke exhaust system to the gas boiler pipe.
  4. Secure the connection with bolts and clamps.
  5. Consistently assemble the entire chimney system. Each element is installed in its “own” place, after which it is secured with clamps (they increase the level of reliability of the connection).
  6. Install overlays that perform decorative functions over the fastenings. They will help maintain the aesthetic appearance of the structure.
  7. Bring the chimney pipe outside.
  8. Ensure the joint is tight.
  9. Place a casing on the pipe that has protective properties. This will help improve the safety level of uncontrolled fires.

  After completing the described installation process, you need to check the tightness of the joints and cover them with a special apron.

  If we are talking about a chimney system outdoor variety, then the installation procedure has its own characteristics. When it is necessary to install such a chimney, you must adhere to the following algorithm:

  1. Determine the exit location and mark its location on the wall of the building.
  2. Make a hole where the mark is. The diameter must correspond to the cross-section of the pipe.
  3. Connect the chimney to the heating device. To do this, you need to use a double-circuit elbow and a special tee. It is needed to ensure the stability of the finished structure in a vertical position.
  4. Secure the “structure” to the wall using brackets.
  5. Seal the area where the chimney exits the wall and continue to assemble it to the desired height.
  6. Secure the structure to external wall using clamps.

  To ensure a reliable connection of double-circuit pipes, it is necessary to use adapter units.

  Transition units connecting double-circuit pipes - important elements device design

  Features of horizontal and vertical installation

  If we are talking about a horizontal installation option, then this procedure must be carried out taking into account technical features building. You need to calculate the following parameters in advance:

  1. Pipe height. The distance from the outlet pipe to the hole in the wall should be less than 1 m. Direct pipe outlet from the outlet pipe to the street is not allowed.
  2. Number of rotary couplings (less than three).
  3. The maximum length of the horizontal section. Should not exceed 3 – 5 m.

  An increase in condensate production is a feature of the operation of the chimney system during the cold season. Excessive moisture loss is caused by harsh operating conditions.

  When it is necessary to install a vertical chimney, you must remember that this procedure can be carried out in two ways:

  1. Cascading. It involves connecting several heating units to one pipe at once. A similar scheme is quite often used in MKD.
  2. Individual. Maximum length vertical elements is 7 m. This allows installation in a two-story private house.

  Options for installing a chimney in a private house

  If we are talking about a brick building, then the smoke exhaust system can be installed both inside and outside. However, effective thermal insulation is required in any case. This will allow you to avoid unpleasant consequences that are likely to arise during intensive use of the boiler if the insulation is neglected.

  Video: options for connecting a coaxial chimney to gas boilers

  Installing a chimney is a procedure that can be performed by any resident of a private or apartment building who has basic skills and knowledge in the relevant field. If these are completely absent, then contact specialists in the installation of such systems - The best decision. This approach will help avoid unnecessary costs, as well as problems with certain services associated with errors made during installation and their consequences that manifest themselves during intensive use.

  When installing heating equipment, it becomes necessary to organize the removal of gases burned during operation. Coaxial chimneys for boilers are the optimal system option for removing combustion products. What are the advantages of using a coaxial type chimney exhaust device and what are the features of its installation?

  The device has a two-channel circulating system, through which air masses are simultaneously supplied to the boiler and fuel combustion products are removed. A chimney of this type is usually used for turbocharged or condensing heating devices with natural or forced removal of burned gases.

  The operating principle of a coaxial chimney is quite simple:

  • combustion products pass through the inner pipe, heating it;
  • the air that enters through the external channel is heated by contact with the exhaust outlet that removes combustion products;
  • Warm air masses enter the fuel chamber, promoting complete combustion of the fuel;
  • the cold air flow passing through the external channel prevents the system from overheating.

  As a result of this process, the efficiency of the heating system increases significantly and the fire safety of the entire device increases. The presence of a device for collecting condensate protects against moisture entering the boiler, and the tip mounted on top of the system protects against precipitation from entering the channels.

  When installing coaxial type chimneys for a gas boiler, the following parameters are taken into account:

  • power heating unit;
  • level of thermal insulation in the room;
  • average monthly air temperature outside the building;
  • type of fuel used;
  • general boiler performance.

  Such factors are taken into account when selecting the size of pipes for installing a chimney.

  Types of coaxial smoke exhaust pipes

  Installation of chimney ducts is carried out in two ways - vertically and horizontally. In the first, the pipe is passed through the roof, and in the second, the outlet is made through a window opening or wall. Most often, horizontal installation of the device is used.

  The technical characteristics of a coaxial chimney and its service life largely depend on the material from which the pipes are made.

  Aluminum

  The material is quite light. Its main advantage is resistance to temperature changes and good anti-corrosion characteristics.

  Due to its inability to withstand high temperatures, aluminum is rarely used in a coaxial chimney system. It is mainly used in combination with plastic.

  Stainless steel

  Stainless steel pipes are the most popular. They do not deform under the influence of sudden temperature changes and can withstand heating up to 550 degrees. The material is highly resistant to aggressive substances and can be used as a smoke exhaust system for 30 years.

  Two types of stainless steel pipes are used for the coaxial system for exhausting combustible gases:

  1. Insulated. Mainly used for installing vertical chimneys. Such a pipe greatly improves the aerodynamic qualities of the device and is installed during the construction of the building.
  2. Not insulated. It is used for both domestic and industrial coaxial type chimney structures. Differs in service life
  
  

  The disadvantages of using uninsulated pipes include high vapor condensation.

  Plastic

  Chimneys made of heat-resistant plastic are used for condensing gas boilers. In addition to being light in weight and able to withstand heating up to 205 degrees, the material has a relatively low cost.

  Plastic coaxial pipes are easy to install. But still, unlike stainless steel products, the duration of their use is short. Such chimneys are used exclusively in gas exhaust systems with low temperature conditions.

  
  

  When selecting pipes, you should pay attention to the manufacturer’s recommendations for the type of heating device.

  Technical requirements for installing coaxial pipe

  Installation of a flue coaxial system for gas heating devices with a closed combustion chamber is carried out in accordance with regulatory documentation. If you deviate from the required standards, the gas service does not give permission to operate the boiler.

  According to the rules established by SNiP, the following technical requirements are prescribed for coaxial chimneys:

  1. Coaxial smoke exhaust structures can be placed in vertical and horizontal positions. Their installation, regardless of the type of installation, is carried out after approval of the provided project by the gas service.
  2. It is not allowed to connect heating units with different types of outlets - forced and natural - to the same network.
  3. The placement of the chimney pipe on the facade should not be below the level of 2 meters. The diameter of the hole for the chimney outlet in the wall must be made 1 centimeter larger than the pipe. For houses made of wood, it is recommended to increase the opening by 5 centimeters and protect it with non-combustible materials.
  4. In multi-storey buildings, the distance from the pipe to the window opening located above it should be maintained at least 1 meter. If the doors and windows are on the same level as the smoke exhaust system, then a distance of 50 centimeters is maintained.
  5. The outlet of the coaxial pipe should be located above top point heat generator at 1.5 meters.
  6. A distance of more than half the diameter of the outer pipe is maintained from the gas pipeline to the chimney.

  When the chimney is brought outside the building, the joints should not be in the wall. All structural parts must completely match each other in diameter. Chimneys for thermal systems with a capacity of no more than 30 kilowatts are allowed to be exhausted through the walls. Under no circumstances should smoke escape through the connections of the combustion product exhaust device.

  To avoid problems with the assembly of parts and the tightness of the entire structure, it is recommended to purchase a complete chimney device from one manufacturer.

  Installation of additional equipment for gas appliances heating is carried out exclusively by specialists in this field. Also, every year a full maintenance of the system is carried out - checking connections for leaks, removing condensate accumulations, and inspecting the integrity of the structure.

  Installation options for coaxial chimneys

  Coaxial type boiler smoke removal systems are quite safe to use, provided correct installation. The length of the horizontal elements of the chimney must be more than 1 meter, and the pipe itself must be more than 5 meters. The height of the device itself at the outlet is set below the roof ridge. The size of the pipes is calculated so that there are no joints in the wall opening.

  Installation of chimneys is carried out in two ways - external and internal. Each option has its own installation features.

  Outdoor Unit Installation

  This method is used for finished buildings that have not yet been heated. Initially, the location of the chimney is marked on the wall of the room. The installation of the device itself is quite simple:

  • a hole is made in the wall to remove the pipe;
  • areas with low heat resistance are insulated with basalt insulation;
  • a pipe is inserted into the prepared opening;
  • using a single-circuit chimney pipe outlet of 90 degrees and a double-circuit tee, the device is connected to the heating unit;
  • the elbow is used as a connecting element, and the tee with a removable slope for vertical fixation of the structure;
  • the connected system is attached to the wall with brackets.
  
  

  After this, the entire structure is assembled. All parts are fastened with clamps. The section of the opening for the chimney outlet is sealed, and the pipe is protected with a special casing. The joints of the opening are covered with an apron.

  Installation of internal chimney

  Before installing the combustion exhaust system, the compatibility of the diameters of the outlet pipe of the heating unit and the smoke exhaust is checked. The size of the tube at the boiler outlet should be no larger than the volume of the gas outlet pipe.

  Installation is carried out in the following sequence:

  1. A connecting elbow and a tee are attached to a special chimney pipe on the boiler. For dual-circuit units, an adapter unit is also installed. All joints are fixed using clamps.
  2. An opening is made in the wall to lead the chimney pipe outside.
  3. If the chimney pipe is located on the side of the boiler, then after installing the transition elements, a horizontal chimney structure is assembled. In this case, the hole for leading the pipes to the street is located from the fastenings to the heating device at a distance of 1.5 meters.
  4. In order for the condensate to randomly flow down the channel into a special collection tank, the outer pipe is fixed at a slight slope.
  5. The upper location of the outlet pipe on the boiler greatly facilitates the installation of the chimney structure. Vertical assembly carried out using special brackets. At the outlet of the chimney roof it is left air gap and material with non-combustible properties is laid. The joints are covered with an apron.

  After assembling the structure, the tightness of all joints is carefully checked.

  Pros and cons of coaxial smoke removal systems

  Coaxial type chimneys for boilers have many advantages:

  1. Productivity increase heating system. Due to the heated air masses coming from the street to the firebox, complete combustion fuel, which, thanks to air masses, is not consumed to heat the boiler. Therefore, the efficiency of coaxial devices is significantly higher than that of simple chimneys.
  2. Safety of use. Air, penetrating from the street into the channels, does not allow the system that removes gases to heat up too much, thereby increasing the fire safety of the entire structure. The hole in the wall through which the chimney is discharged may not be additionally insulated.
  3. Universal application. Coaxial devices for exhausting combustion gases can be used for turbocharged units operating on any type of fuel.

  One disadvantage of such chimney systems is the possibility of ice forming on the pipes at low air temperatures. This occurs due to the presence of condensate in the channels. It is formed due to the fact that the temperature of the exhaust combustion products falls below the dew point level.

  Coaxial chimneys are much more productive than conventional smoke exhaust devices. They are easy to use, safe, practical and installation of the system is completely simple. The relatively high price of the product is fully justified by the effectiveness of its application.

  Heating equipment operating on solid or liquid fuels requires the installation of a complete system for removing combustion products. Previously, a classic single-wall chimney was used as an exhaust device. steel pipes, which has a lot of disadvantages. Nowadays more practical and effective solutions based on a coaxial pipe.

  What is a coaxial chimney

  The concept “coaxial” is used to designate any structure consisting of two objects located around common axis. In the case of a coaxial type chimney, this is a smoke exhaust channel consisting of pipes of different sections.

  The distance between the pipes is the same along the entire length of the chimney, including rotary elbows, bends and other elements. This is achieved through special jumpers, which are located along the entire length of the chimney.

  The coaxial chimney is made of two pipes with a common central axis, separated by special internal jumpers

  The principle of operation of a coaxial chimney

  The channel between the inner and outer pipes ensures a constant supply of fresh air, which is necessary to maintain combustion processes. Inner pipe is a channel for excretion flue gases and other combustion products. In fact, the special design of the coaxial pipe allows the chimney to perform two functions at once: output harmful substances and supply ventilation.

  Flue gases are removed through the internal channel, and fresh air enters the combustion chamber through the inter-tube space

  The main area of ​​application of coaxial chimneys is wall-mounted and floor-mounted gas boilers with a closed combustion chamber, geysers and convectors. With equipment running on solid fuel, coaxial type chimneys are not used.

  Advantages and disadvantages of the coaxial chimney design

  Among the advantages of coaxial type chimneys are:

  
  

  Despite many advantages, the design of a coaxial pipe is not without drawbacks. At temperatures below -15 o C, the coaxial chimney can freeze severely.

  This is due to the fact that, in fact, this is an advantage of the design in question - cold air It is heated by the temperature of the flue gases escaping outside. The combustion products cool greatly and can condense at the outlet of the chimney, which leads to severe icing on the chimney head.

  One of the main advantages of a coaxial chimney turns into its main disadvantage - at low temperatures outside, combustion products condense and ice freezes on the pipe head

  To prevent icing, you should choose special devices, designed to operate at subzero temperatures, and also calculate the cross-section more carefully chimney.

  Types of coaxial chimneys

  Depending on the method of laying the chimney, coaxial type chimneys are divided into two types:

  1. Vertical - the chimney is located strictly in a vertical position. Gases and combustion products rise from the fuel chamber and are released into the atmosphere above the ridge level. Mostly vertical structures are used in residential buildings and provide a good level of natural draft.
  2. Horizontal - the main chimney channel is represented by a structure located in a horizontal position, which is discharged through a load-bearing wall. In this case, flue gases come out in the immediate vicinity of the heating equipment. It is most often used in private homes where closed heating systems are installed.

  A vertically oriented coaxial chimney, despite some advantages, is a more expensive and difficult to install system. The total length of the smoke exhaust duct usually exceeds 5 meters, which significantly complicates the process of installation and fixation of the structure.

  To manufacture a coaxial type chimney, various grades of steel and plastic are used. In accordance with this, several types of chimneys can be distinguished:

  • galvanized - the most affordable option chimney of coaxial type. The average service life of the product does not exceed 5–7 years, after which the structure partially rusts or becomes damaged. The cost of the product depends on the manufacturer and technical parameters, but rarely exceeds 2–2.5 thousand rubles;
  • made of plastic and aluminum - a combined option for private use. The internal chimney channel is made of aluminum up to 2 mm thick. The outer pipe is made of high-strength heat-resistant polypropylene. Such chimneys are used only in the private sector for collaboration with boilers of low and medium power;

    Coaxial chimneys made of galvanized steel are designed to last 5–7 years, plastic products will last much longer

  • stainless steel chimneys are more reliable and durable than galvanized ones. They are designed for 10–12 years of use. The cost is almost the same as stainless steel products. They are not used in industry and collective smoke exhaust systems, since “stainless steel” does not withstand high concentrations chemical substances;
  • made of high-alloy steel - the most durable and durable option for a coaxial chimney. High-alloy steel is not afraid of exposure to high temperatures and chemicals contained in flue gases. The average service life is at least 15 years.

    A coaxial chimney made of high-alloy steel, unlike stainless steel, is not destroyed by aggressive chemicals contained in combustion products and lasts at least 15 years

  The range of some manufacturers (Electrolux, Viessmann, Schiedel) includes models of coaxial chimneys with an additional thermal insulation layer. This is a classic design with two channels, which is located in another pipe. The voids between extreme pipes filled with non-flammable thermal insulation material, preventing freezing and blockage of the air channel.

  Video: coaxial pipe for parapet gas boilers

  Basic elements of a chimney

  A coaxial chimney consists of various elements that make it possible to produce a chimney of the desired configuration for specific operating conditions and structural features.

  The coaxial chimney kit contains everything needed for its installation.

  Fittings, connecting elements, nozzles and other structural elements are manufactured according to a certain standard, which simplifies the process of assembling and installing the chimney. The range of leading manufacturers includes more than 80 elements of various configurations.

  A ready-made coaxial chimney kit from the manufacturer includes the following elements:

  
  

  To ensure the tightness of all connected parts of the structure, special sealing rings made of heat-resistant material (thermoplastic) are used. When heated to high temperatures, the ring expands into a more elastic form, which allows it to maintain a seal even at high pressure.

  Making a coaxial chimney with your own hands

  In order for the chimney to cope with its tasks throughout its entire service life, it must be correctly calculated and correctly installed.

  Calculation of chimney parameters

  When designing a chimney, attention should be paid Special attention calculation operations, since the performance of the system as a whole will depend on the parameters of the chimney. The cross-sectional area of ​​the outlet channel of the coaxial chimney should not be less than the cross-section of the connecting pipe of the heating equipment.

  The cross-section of the smoke duct of the coaxial chimney is selected to match the dimensions of the heating equipment pipe

  In collective systems, when connected to two or more heating devices, the channel cross-section increases in proportion to the size of their pipes. This is necessary in order to ensure sufficient throughput of the smoke exhaust channel when several boilers are operating simultaneously.

  Table: dependence of the cross-section of the chimney channel on the rated power of the heating device

  The cross-sectional diameter of the outlet hole is calculated by the formula - F = (K * Q) / (4.19 * √H), where:

  • K - constant coefficient equal to 0.02–0.03;
  • Q (kJ/h) - maximum power of the gas boiler specified in the device specification;
  • H (m) - design height of the smoke channel.

  For example, let’s calculate the cross-section of the chimney outlet for the Ariston CLAS B gas boiler. Maximum thermal power in heating mode it is 24.2 kW. The height of the smoke channel is 8 m.

  1. To convert power from W to kJ/h, we will use one of the online programs that are easy to find on the Internet. We get that Q = 87 120 kJ/h.
  2. We find the cross-sectional area using the above formula: F = (0.02 * 87,120) / (4.19 * √ˉ8) = 147.03 mm.

  After calculations, the resulting value must be compared with the data in the table. It indicates optimal area chimney sections round section for domestic gas boilers. If necessary, the value is adjusted up or down. In our case, you can use a pipe with a diameter of 130 mm.

  Necessary tools for installing a coaxial chimney

  To install a ready-made coaxial chimney kit you will need:

  
  

  For self-made a coaxial chimney will require two pipes of a suitable diameter, which are connected using stainless steel jumpers. Used for connection steel rivets or self-tapping screws.

  It is important to understand that completely repeat the design of finished chimneys industrial production it won't work. You can only make a straight section of coaxial pipe yourself.

  Preparatory work before installing the chimney

  According to statistics, coaxial type chimneys are the safest. The rules for their assembly and installation are described in detail in SNiP 2.04.08–87, SNiP 2.04.08–87 and PB 12–368–00. Before installing the chimney, you should carefully study the attached instructions and become familiar with the requirements outlined by the manufacturer of the structure.

  In general, when installing a coaxial chimney, the following rules must be observed:

  
  

  When installing a coaxial type chimney in wooden houses, the place where the pipe meets load-bearing wall or the ceiling is sheathed with non-combustible material. Usually an asbestos pipe or a box made of asbestos-cement slabs is used.

  Step-by-step instructions for installing a coaxial chimney

  Before installing the chimney, you should carefully check the completeness of the purchased device. If any parts are missing, the chimney assembly should be postponed. In addition, it is imperative to check the diameter of the outlet pipe and the cross-section of the internal channel.

  The technology for assembling a coaxial type chimney consists of the following steps:

  1. In the designated location, markings are applied for the exit of the smoke duct to the street. For a floor-standing gas boiler, the chimney outlet should be located 1.5 m above the combustion chamber. For wall-mounted installations, it is possible to remove the pipe immediately after installing the rotary elbow.

     The chimney of a wall-mounted boiler can be removed immediately after installing the rotary elbow on its pipe

  2. After applying the markings, a hole is drilled using a hammer drill with a crown attachment required diameter at an angle of 3° to the wall surface. It must be taken into account that in addition to the pipe, an insulating gasket is installed in the hole.
  3. An adapter is connected to the outlet pipe of the gas boiler, onto which a straight section of pipe or a 90° coaxial elbow is mounted. To connect the elements, a crimp clamp is used, which is tightened with a Phillips screwdriver.

     A special adapter is used to connect the chimney to the gas boiler

  4. An asbestos pipe and a sealing collar are installed in the wall hole. Next, the straight section of the chimney is led outside. From the inside, the pipe is connected to a rotary elbow or extension nozzle and secured with a crimp clamp.
  5. The hole in the wall is additionally insulated using special pads. To do this, the contact point is treated with heat-resistant sealant, and the nozzle is screwed onto galvanized screws. If necessary, a deflector or blow-out protection is placed on the end of the pipe.

     The deflector protects the boiler from blowing out through the chimney

  During installation vertical design hole in ceiling cut using a grinder with a wood disc. A box of asbestos-cement slabs is installed at the junction point. In this case, the distance from the outer pipe to the ceiling should not be less than 20 cm.

  A similar condition is met when the pipe exits through the roof. To do this, a special passage element is mounted at the junction point, which is attached directly to the roofing material using galvanized self-tapping screws.

  Video: coaxial chimney in a private house

  Chimney insulation

  Freezing and icing of the head of a coaxial chimney is associated with condensate entering the air intake duct. To prevent moisture ingress, you should check the slope of the coaxial pipe relative to the combustion chamber. If the slope angle is at least 3 o, then freezing of the tip will only occur at temperatures below -15 o C.

  The main mistakes when installing a chimney are related to incorrect inclination of horizontal sections

  Additionally, a special element can be installed on the head, which extends the internal channel by 10–40 cm relative to a pipe of larger diameter. In addition, several holes can be drilled in the lower part of the outer pipe. This will allow air intake even when the tip is partially frozen.

  If the slope is insufficient, freezing cannot be eliminated, since the condensate will not flow towards the combustion chamber, but, on the contrary, towards the outlet, which will lead to the formation of icing and icicles at the end of the pipe. Insulation by covering with heat-insulating material with outside pipes won't help.

  Video: removing condensation from the air supply pipe in winter

  Chimney cleaning and periodic repairs

  For operation of heating equipment with a closed combustion chamber, it is used natural gas- methane. During the combustion of gas, harmful aromatic hydrocarbons, toluene, benzene, etc. are formed. The formation of soot and burning does not occur as such.

  Almost all gas combustion products are discharged through a coaxial chimney. At the same time, complete cleaning of the smoke channel is not required even with daily use. Enough once every heating season check and clean the condensate collector. Once every few years, it is recommended to inspect the smoke duct using special video inspection equipment.

  A highly sensitive thermal imager is used to inspect and inspect the chimney

  To repair a chimney, you will need to dismantle all elements of the smoke exhaust channel down to the damaged area. After replacement, the structure is assembled taking into account regulatory requirements.

  The coaxial chimney is a highly efficient and practical design that significantly increases the efficiency of heating equipment. Subject to the rules described in regulatory documents, a coaxial chimney does not require periodic repairs and reliably removes all flue gases.