Modern gas boilers are reliable equipment that can provide us not only with heat in the house, but also with hot water supply. But for them proper operation and high performance must be installed special chimney. It must perform two main functions at once: supplying oxygen to the burner and discharging it outside the room. For this, a coaxial pipe is used. Let's talk about what it is and what its features are.
We will not talk about any design features heat generators. It is enough to understand that for them efficient work a chimney is required. The situation here is the same as with the most ordinary wood stove. Of course, the coaxial pipe for the boiler has a completely different design, and its installation is carried out with its own nuances, which will be discussed below. So, key feature of such a chimney is that it works on the “pipe-in-pipe” principle. It turns out that we have two pipes: one of smaller and the second of larger diameter (external and internal). One of them supplies oxygen to the combustion chamber, and the other removes combustion products into environment. Very effective solution, especially if you take into account the fact that such a pipe takes up very little space and is installed in one day.
Coaxial gas pipe has a number of significant advantages, thanks to which it has earned such popularity. Firstly, this is the localization of the combustion process, which is carried out by an isolated supply and exhaust of air and, accordingly, combustion products. As a result, there is no mixing of oxygen and gas mixtures. Consequently, the productivity of the equipment increases.
Another plus is that as the air enters the boiler, it heats up. This is achieved due to the fact that the pipe through which it enters is heated by waste combustion products. Overall very effective, especially in the cold season. Of course, one cannot ignore the fact that the “pipe-in-pipe” chimney design itself has smaller dimensions compared to a separate installation. At the same time, the number of fasteners is reduced, and the complexity of installation is significantly reduced.
Of course, there is no ideal system that would not have shortcomings. In our case, although there are disadvantages, some of them can be dealt with simply because they are insignificant, while others will have to be tolerated.
The main disadvantage of such structures is that their cost is ultimately 20-40% higher than the installation of separate systems. Another problem is the concentric arrangement of hot and cold air pipes. You have probably noticed icing on such pipes more than once. It is formed due to the accumulation of condensate and its freezing at sub-zero temperatures. You can combat this by installing additional drainage and insulation. But all this will increase the price even more.
Well, the last drawback is the limited length of the coaxial pipe. This is approximately 4-5 meters. Therefore, if your boiler is not installed near a window or there is no way to vent coaxial pipe for whatever reason, this option is not suitable for you.
It is necessary to understand that you cannot just take and install such a chimney, since the installation of a coaxial pipe is carried out taking into account existing requirements and standards. For example, there is a clear rule that states that chimneys can only be installed through the roof. But that doesn't concern individual heating, where it is possible to install horizontal coaxial chimneys. In general, horizontal systems for exhausting combustion products and supplying air can only be installed in private houses, and for multi-storey buildings Vertical structures are provided, which should rise 1.5 meters above the roof of the building.
All modern coaxial chimneys are divided into internal and external. First in residential buildings are practically not used. Such structures are installed in special shafts or old chimneys. But they must comply. In addition, installation of such systems is often very difficult, as is maintenance.
External coaxial chimneys do not have such disadvantages. By the way, they are also usually classified according to their insulation. So, there are insulated and non-insulated. In regions where the air temperature does not fall below -10 degrees Celsius, chimneys do not need to be additionally insulated. In other cases, there is a risk of partial or complete freezing of pipes. In addition, there are individual and collective chimneys. The first ones are designed to serve one gas boiler, and the second - for an entire multi-story building.
The coaxial system is modular and consists of a large number of assembled elements. This includes a gas boiler adapter, straight pipe sections, connecting elements such as couplings and tees, and much more. True, such components as a coaxial pipe extension, decorative overlays, may not be supplied in the kit - you need to purchase them yourself if necessary. But the mounting hardware and sealing gaskets that ensure the strength and tightness of the system must be included in the kit. When installing such a system, it is advisable to use jumpers. They are necessary to fix the inner pipe relative to the outer one.
As for the materials from which the coaxial pipe is made, most often it is galvanized and can easily withstand high temperatures and does not corrode for a long time. In some cases it is advisable to use heat resistant plastic or aluminum. Often, for the consumer, it makes no difference what material the pipe is made of; the main thing is to carry out the correct installation.
In most cases, a coaxial pipe is supplied together with heating equipment, that is, with a gas boiler. That is why almost all manufacturers of heat generators also produce chimneys of this type. The equipment installation instructions contain a clause that indicates the maximum permissible length of the chimney. This value must not be exceeded under any circumstances. Otherwise, the efficiency of the equipment is significantly reduced. If the chimney operates on natural draft, that is, the boiler does not have a fan, then a parameter such as the minimum pipe length is entered. If you install a chimney that is shorter in length, there will be no draft and combustion products will remain in your apartment or house. The diameter of the pipeline is written as 100/140, where the first value is the diameter of the inner pipe, and the second, respectively, the outer one.
The first thing you should remember is to have no more than 2 bends in your chimney. When installing a horizontal system, install the pipe with an inclination of at least 3 degrees. This is necessary so that the condensate drains on its own. If the coaxial pipe ultimately connects to a common chimney, then the angle must be changed in the opposite direction with a slope towards the boiler.
The most critical stage of work is drilling a hole in the wall. This must be done using diamond equipment. But it is advisable to carry out such work if the house is being renovated, since there will be quite a lot of noise and dirt. After the hole is ready, it is necessary to lay the pipe, insulate it, and seal it. In general, there is nothing complicated here. The main thing is that the chimney at the bends is well sealed. Also, do not forget about the minimum slope that is necessary for the outflow of condensate.
A vertical coaxial pipe is much easier to install than a horizontal system. But it is not always possible to bring the chimney to the roof. So, if you want the coaxial pipe to be installed correctly, you need to follow a few simple requirements.
Thus, the system cannot be installed below ground level. If the distance from the outlet to the ground is less than 1.8 meters, then a deflector grill is installed to protect the pipe from dirt. If there are any in your region strong winds, then it is quite possible that the boiler will go out and not work at full capacity; this problem can be completely and completely solved. Of course, it is advisable to entrust such work to the specialists who installed the heating equipment, but if this is not possible, then by observing these requirements, you can cope on your own.
We talked about what a coaxial pipe is. As you can see, this is a very efficient and practical chimney in terms of performance and space saving. It is quickly installed and serviced, which is without a doubt important point. If necessary, you can install a coaxial pipe extension, which will slightly increase the total length of the chimney. Special attention Pay attention to insulation, as such systems often freeze completely. There is nothing good about this. Moreover, this happens in the most severe frosts. Although the problem is solved quickly, it is still better that it does not exist. Now you can decide for yourself whether to use such a system or not. All the best!
Autonomous heating in Lately becomes not only a necessary condition living in a private house, but also a way to increase comfort and save money for owners of living space in multi-apartment buildings. The increased demand for heating devices has become the reason for the development of more powerful and efficient models. Modern equipment places increased demands on the safety of connection and removal of combustion waste through chimney ducts. For this reason, a coaxial chimney for a gas boiler has come into use, the design of which is fundamentally different from the usual one.
A coaxial chimney is a smoke removal channel, the design of which consists of two pipes of different diameters inserted into one another. Internal surfaces pipes do not touch each other, between the contours there is air gap. A coaxial chimney is assembled from additional elements: straight pipes, bends, tees, condensate collectors. It performs two main functions:
Important! This device is designed on the principle of dividing the function of the chimney. This allows for increased productivity and efficiency. Fuel combustion products, the temperature of which is quite high, heat the external circuit. And the outer pipe, through which atmospheric air passes, in turn cools the inner one. Thanks to this design, the temperature in the chimney is equalized, which prevents condensation and reduces the risk of fire.
The coaxial chimney is considered more advanced and effective way removal of combustion products from the furnace of the heating device. Elements for assembly are often supplied with the equipment. Most manufacturers recommend installing their products with chimneys of this type, as they have the following advantages:
Important! The coaxial chimney is suitable exclusively for gas boilers with a closed firebox and forced draft, operated by a small fan built inside the pipe. The design of a smoke removal system of this type must include a condensate collector and an inspection through which the pipe is cleaned.
According to statistics from the Ministry of Emergency Situations and manufacturers, coaxial smoke exhaust ducts are considered safer and more efficient. However, when installing them, certain requirements must be observed:
Note! Professional builders arguing about the effectiveness of using coaxial chimneys on the territory middle zone Russia and more northern regions, claiming that they were developed for use at temperatures down to -15 degrees. Where in winter most of the time the temperature drops below this mark, they freeze. Manufacturers explain the problems by incorrectly calculating the diameter of the outer and inner pipes and the length of the chimney.
Unlike traditional methods of smoke removal, a coaxial type chimney is simply installed. To complete the installation, you must strictly follow the manufacturer's instructions gas equipment and requirements fire safety. Experienced craftsmen We advise you to pay attention to the following points:
Comfortable living in your home depends on the efficiency of your heating system. Heating a home involves the use of open fire devices, which reduces the oxygen content in the atmosphere inside the house. Vicious circle? Not at all. The problem is solved by using coaxial chimneys for removing combustion products. What is it and how to build it yourself?
An autonomous home heating system for any device requires complete removal of combustion products. Traditional chimney systems are still used today. However, they are being replaced by new devices that solve several problems simultaneously - coaxial chimneys.
Their appearance is associated with solving the problem of fuel combustion in a furnace, which occurs with the participation of oxygen from the heated room. If concentration is not restored by ventilation, the room becomes stuffy and uncomfortable. The conclusion is obvious - isolate the fuel combustion device (boiler) and supply oxygen to the furnace from the outside. For this purpose, two-layer pipes were used, in which combustion products are removed from the inside, and air from the street is discharged through the gap between the inside and outside.
Coaxial chimney device
They are as follows:
These include the tendency of the inner pipe to freeze. This becomes possible due to the low temperature flue gases already at the exit from the oven. As a result, condensation forms, which freezes when the outside air temperature is below -15 degrees, which is not at all unusual for Russia. The degree of freezing can completely block the channels of gas and air movement, which means an emergency situation.
Attention! The pipe must not be allowed to completely freeze, as this will damage the boiler equipment.
As practice shows, such phenomena often arise from the desire to maximize the efficiency of the system by reducing the diameter of the internal chimney pipe, which leads to a decrease in the temperature of gases down to the “dew point”, increased condensation and, accordingly, to the formation of ice.
Devices for removing combustion products of this type are divided according to several criteria.
Internal systems are located in shafts specially constructed during the construction of the house. In no case do they come into contact with the living space. In some cases, such devices are installed as standard brick chimney, but it should be noted that such chimneys are inconvenient for maintenance and repair.
Methods for installing a chimney in the house
External chimney systems are installed directly on the wall of the house with outside. There is an opinion that they spoil the design of the house, so they are placed with access to the patio. This device design is easy to install and convenient to maintain and repair.
Exiting a coaxial chimney through the wall of a building
As noted above, in our harsh winters the chimney freezes. To avoid this effect, you need to insulate the chimney. There are several ways to do this:
Coaxial designs were originally designed as purely horizontal devices. But this is a theory, but in practice the decisive factor is the location of the heating unit, which in some cases requires a combined design.
Vertical outlets are used only for boilers without forced draft.
Internal vertical and external combined coaxial chimney
The coaxial pipeline kit includes a different number of parts depending on the design of the chimney exhaust device.
Design of a coaxial chimney
The main ones are:
The operating principle of a chimney of this design is that when fuel burns, flue gases are formed and immediately rush into the chimney. Emerging zone low blood pressure filled with outside air through the channel between the walls of the pipes. Warming up along the way from the inner pipe, it enters the firebox and the heated oxygen actively reacts with the fuel. At the same time, the efficiency of the device increases significantly. The cooled outer wall is favorable for the fire safety of the device.
The completeness of the chimney depends on the location of the heating unit. The device consists of a number of standard units that allow the construction of chimneys of any configuration. The modules are modified, which makes it easy to equip the device necessary details and simplifies installation work. When creating a coaxial chimney, the following components are used:
The material for the manufacture of chimney elements can be:
The general requirement for them is resistance to temperatures of at least 250–300 degrees.
When assembling a chimney, the simplest tools are used to install fasteners, such as screwdrivers and keys. To attach the brackets to the walls you will need an electric drill and plastic inserts - dowels. Hole in brick wall can be done with a bolt and a chisel.
Despite the apparent simplicity of the chimney assembly process, it must occur according to a certain algorithm:
Before you begin assembling the chimney, you need to clearly understand the basic regulatory provisions:
When assembling the chimney, you must adhere to the following rules:
Installation of a horizontal coaxial chimney
Compliance with these rules will allow for safe operation of the heating device with high-quality removal of combustion products.
Installation of a horizontal coaxial chimney is carried out as follows:
Upon completion of assembly, it is necessary to check that the assembled device complies with all the rules outlined above. Something to remember! The use of sealing gels and sealants in coaxial chimneys is prohibited.
Installing a coaxial chimney vertically is usually forced measure, due to the impossibility of performing horizontally without violating the installation rules. The peculiarity of the design is that such combustion product outlets cannot be installed in a straight line from the furnace due to the formation of a large amount of condensate. With this design, it will fall directly into the firebox, which is extremely undesirable. Therefore, you need to make an elbow from the stove for the horizontal component. Next, a second elbow and a condensate collector are installed. After this, the chimney is mounted vertically. Intersection with the ceiling and roofing pie performed using cups - insulators. On the roof, the pipe is equipped with a sealing umbrella to prevent leaks.
Attention! A vertical coaxial chimney is not used for closed boilers with forced draft.
First of all, you need to pay attention to the noticeably more high efficiency furnaces with such devices for removing combustion products. The efficiency increases due to optimal mode fuel combustion.
With normal heating of a home, the air in it does not deteriorate, remaining clean, since oxygen from the outside air is used for combustion. There is no need for mandatory organization of supply ventilation, although it is usually created anyway; it will not be superfluous.
Coaxial chimneys are characterized by long-term operation because the pipes, which are constantly cooled by an influx of air, do not overheat.
The device requires virtually no special maintenance. At the beginning of the heating season, you need to inspect all fasteners and ties, and tighten loose connections.
A regular maintenance activity is periodic draining of condensate from the storage tank. Moreover, the frequency of such an operation is determined by the weather, which affects its formation.
The need to clean the inner pipe wall is determined by a visual inspection through the inspection window before the start of the heating season. The procedure is performed with a special brush equipped with stiff bristles. Chemical agents are used to soften carbon deposits and soot.
Coaxial chimneys should be considered the most advanced for saving heating costs, decreasing by 15–20%. At the same time, living conditions in the house improve.
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.
Construction involves placing one object inside another. A similar chimney is made in the form of a double-circuit product. Pipes of different diameters are used as building materials. Such “structures” are divided into several types:
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
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:
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, a chimney of this type 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 the uninterrupted operation of a homemade chimney, it is necessary to make calculations in advance and carry out the installation efficiently, taking into account the structural features.
Chimney installation diagram
The main advantage of the coaxial type of chimney is that the air masses used in the operation of the boiler are taken not from the room, but from the 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:
Thanks to the listed positive aspects, the coaxial chimney is popular among a large number of people. In addition to the advantages, two-channel chimneys have a number of disadvantages.
These include:
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
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 finished system chimney, 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. Compliance with them is a prerequisite, since neglect of such rules can lead not only to problems with sanitary and epidemiological inspection, but also to accidents.
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:
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
If you need to independently install an internal chimney, then all actions are performed in the following sequence:
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:
To provide reliable connection double-circuit pipes, it is required to use adapter units.
Transition units connecting double-circuit pipes - important elements device design
If we are talking about horizontal version installation, then this procedure must be carried out taking into account technical features building. You need to calculate the following parameters in advance:
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:
Options for installing a chimney in a private house
If we are talking about brick building, then the chimney system can be installed both inside and outside. However, effective thermal insulation is required in any case. This will avoid unpleasant consequences, which are highly likely to occur during intensive use of the boiler if the insulation is neglected.
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.
Everyone knows that performance heating systems, which uses the principle of fuel combustion, is impossible without oxygen to support combustion and proper removal of exhaust gases. Today, to create autonomous heating systems, various gas equipment is in great demand. It is compact and safe, easy to use, perfectly automated and does not require constant intervention by the owner in the work process.
This device looks more like a motorcycle exhaust pipe. In fact, this is a specially designed structure, a pipe in a pipe with different diameters, which are inserted one inside the other and rigidly fixed to each other. Combustion products are removed through the inner tube, and the air necessary for combustion of the fuel enters the combustion chamber through the space between the inner and outer tubes. A coaxial chimney for a gas boiler solves two main problems at once: removing exhaust gases and supplying air to the device.
Such chimneys are made from pipes round section, and the internal one is most often made from aluminum alloy, and the outer one is made of steel, thickness 1; 1.5 or 2 mm. The ratio of internal and external diameters for wall and floor heating devices is 60 to 100 mm. For condensing boilers, chimneys with a diameter ratio of 80 to 125 mm are used.
There are two types of coaxial chimneys: horizontal and vertical. The easiest to install, and accordingly, the most common smoke removal system of this type is horizontal chimney. A vertical coaxial chimney is quite difficult to install and is therefore used if horizontal installation not possible or from the heating device to street wall more than 4 m.
As mentioned above, this type of smoke exhaust system is used only for gas equipment with a closed combustion chamber, namely:
The main advantages of such an air intake and smoke removal system are:
The most attractive for using chimneys of this type are apartment buildings, since the emission of carbon monoxide and fuel combustion products is not produced in ventilation shaft, but directly into the atmosphere.
Such chimneys also have disadvantages, namely: rather expensive insulation to prevent freezing of the chimney head. The possibility of freezing of the pipe head is quite high. This happens because the temperature of the exhaust gases is too low and is not able to melt the ice formed when moist air escapes. The consequences of icing can be quite serious: repair of burners, combustion chambers and turbocharging.
As mentioned above, there are two main schemes for installing a coaxial chimney: vertical and horizontal. During installation, you should adhere to certain rules for installing a coaxial chimney, regulated by SNiP 2.04.08–87; SNiP 2.04.05–91.3, as well as the set of “Safety Rules in the Gas Industry”.
The total length of the coaxial chimney cannot be more than 4 m. If a larger length of the smoke exhaust system is required, then a larger coaxial chimney should be used.
When installed vertically, the chimney passes through the ceiling and roof. In order to install the system in a vertical position, a special adapter is used. 
It should be noted that such an adapter is not a universal device and each manufacturer produces this device strictly for its own equipment. To achieve the required length of the chimney, special extensions are used.
To ensure tightness when the chimney passes through the roof and protect it from precipitation, a device called a terminal is used.
When installing a vertical smoke exhaust system, you should be guided by the rules that regulate its height, depending on its location in relation to the ridge of the pitched roof. 
Most often, a vertical coaxial chimney is installed in private houses. But there is another option for a vertical smoke exhaust system - collective, which is designed for apartment buildings. General coaxial chimney in apartment building makes the use of individual gas heating devices completely safe.
Horizontal exhaust gas outlets are most often used for wall-mounted heating equipment. Horizontal scheme implies the exhaust of the chimney through the outer wall to the street.
During installation, you should take into account the slope of the chimney of 2-3° to prevent condensate from entering the boiler unit.
To pass through the wall, two types of devices are used: basic or horizontal. The only difference between these kits is the connection adapter to heating device. If, when passing through a wall, it is necessary to go around a beam, reinforcement, etc., then special bends and elbows are used.
Installing a coaxial chimney with your own hands is quite simple and anyone can do this work House master with basic skills in using power tools. 
To complete the work, you will need a kit that includes: a pipe with a flange, a clamp, an adapter for connecting to the boiler unit and a coaxial elbow. If necessary, you should purchase a special coaxial chimney extension.
It should be noted that with each turn of the chimney by 90°, the maximum length coaxial chimney by 0.5 m.
