Coaxial chimneys for wall-mounted gas boilers in Lately have wide application for modern heating equipment. This perfect solution for a private house in which there is no chimney pipe, as well as for apartment buildings that have a common riser for smoke removal.

Simplicity of design and aesthetic appearance do coaxial chimney indispensable for proper operation gas wall-mounted double-circuit or single-circuit boiler. Let us take a detailed look at its features, operating principles, requirements for installation and installation of this structure.

Coaxial chimney for a gas boiler: what is it and where is it used

Coaxial chimney is used for heating with forced draft. The boiler itself must be turbocharged, i.e. have a built-in fan to exhaust combustion products. The very concept of “coaxial” means coaxial, i.e. chimney "pipe in pipe". Through the outer pipe there is an influx of air into the boiler, inner pipe— exhaust gases released into the atmosphere.

The diameter of these chimneys is usually 60/100. Its inner tube is 60 mm, and its outer tube is 100 mm. For condensing boilers, chimney diameter: 80/125 mm. The material used is steel coated with heat-resistant enamel. white. We look at the standard equipment according to the photo diagram.

There is also such a thing as an insulated coaxial chimney. This is the same coaxial chimney, only its outer pipe is made not of metal, but of plastic. Or the second option: when the inner pipe is slightly longer than the outer one. This was done specifically to prevent condensation from forming on the outer pipe. This type of chimney costs a little more, but not much.

A coaxial chimney can be composed of several elements:

— coaxial pipes (extensions) of different lengths from 0.25 m to 2 meters;

— coaxial elbow (angle) at 90 or 45 degrees;

— coaxial tee;

- the tip of a pipe, sometimes an umbrella;

- clamps and gaskets.

Manufacturers of coaxial chimneys for gas boilers

When purchasing a wall-mounted gas boiler, you will be offered to immediately buy a coaxial pipe for it. In a normal, standard situation, a coaxial kit is sold for horizontal system smoke exhaust, which includes: a 90 degree elbow, a 750 mm extension with an outdoor tip, a crimp clamp, gaskets and decorative inserts.

If your case is slightly different, then all other parts and elements can be purchased separately. These elements are universal for almost any manufacturer of wall-mounted gas boilers.

The exception is the first element, this is either the first elbow or the first pipe from the boiler. The fact is that each boiler manufacturer has its own seating characteristics. This applies to branded (native) coaxial chimneys.

But there are times when pipes for a certain brand of boiler are not available or they are very expensive. For example, a branded coaxial kit for a German boiler costs about 70 euros. In such cases, you can consider purchasing its analogue.

Analogues of coaxial chimney manufacturers

These kits have universal seats, and the holes for attaching the starting elbow (outlet) coincide with most manufacturers of gas boilers presented on the Russian market.

Coaxial chimney "Royal Thermo"

Coaxial chimneys from " Royal Thermo» suitable for , Vaillant or Navien. When purchasing Royal pipes, look carefully at the packaging; on the end of it, each brand of boiler has its own article number: “Bx” - Baxi, “V” - Vaillant, “N” - Navien.

Another manufacturer on the market of coaxial pipes and elements for them is the company “ Grosseto».
Their chimneys are universal and suitable for boilers of the Ariston, Vaillant, Wolf, Baxi, Ferroli brands, as well as Korean and Korea Star.

The main advantage of universal analogues of coaxial chimneys is their low price. It differs from branded kits by two or even three times.

Installation and requirements for installation of a coaxial (coaxial) chimney

The coaxial chimney can be installed in three options:

— horizontally with access to the street;

— horizontally with outlet to the shaft (apartment heating);

- vertically with outlet to an existing chimney.

The most common way to output a coaxial chimney is horizontally with output to the street.

Coaxial chimney into the wall

From the diagram above we see:

1 - coaxial pipe with a tip;

2 — coaxial elbow;

4 - coaxial pipe (extension);

For correct installation coaxial chimney there are a number of requirements

1. The total length of the chimney should be no more than 4 meters.

2. Only two turns are allowed, no more than two knees.

3. The minimum distance from the pipe to the section of the ceiling and walls made of non-combustible material should be 0.5 meters.

4. The horizontal section of the pipe should be made with a slight downward slope towards the street.

These must be done so that the resulting condensate does not flow into the boiler, but goes outside.

Separate chimney systems for gas boilers

Another popular method of removing combustion products from turbocharged gas wall-mounted boilers is a separate smoke removal system. What is it?

There are times when, for one reason or another, it is impossible to remove a coaxial chimney. For this purpose, a system was developed consisting of two separate pipes: one for the release of gases, the other for sucking air into the boiler. Let's look at the installation diagram.

Separate chimney for boiler

As a rule, the diameter of such pipes is 80 mm. Material: steel. In some cases, the air suction pipe is replaced with a flexible aluminum corrugation, which stretches up to 3 meters.

In order to install a separate chimney on a gas boiler, you need to buy a special adapter - a channel separator. It is installed on top of a mounted boiler and converts the “pipe-in-pipe” outlet into a separate one, onto which the pipes are then mounted.

Some manufacturers, for example, the same Navien, took care of consumers in advance and produce wall-mounted gas boilers since already installed system for separate pipes. This is a purely Korean version of boilers, designated under the article “K”. A boiler with such a system will be called “Navien Deluxe-24 K”, where 24 is its power in kW.

Installation of a boiler with a separate chimney system

Pipes can be laid out in 3 options:

- both pipes into one wall;

- both pipes in different walls;

- one pipe into the wall, the second into the existing chimney.

Which smoke removal method is right for your home should be decided by the design organization. According to technical specifications, they create an individual project for each home.

It specifies the design of the gas boiler (floor-standing, wall-mounted), its maximum power, as well as which pipes should be installed: separate or whether it is necessary to buy a coaxial chimney for a gas boiler.

The only thing they do not have the right to decide for you is the brand of the boiler. No one can force you to buy a model from a specific manufacturer. Here the choice is only yours. Let's watch the video.

Coaxial chimney - new technical solution, which replaced standard chimneys. The peculiarity and great advantage of this device is that the oxygen for combustion in the boiler furnace is taken from the street, and not from the house.

Coaxial chimney designs

Chimneys are used for different types boilers:

• B - chimneys for boilers with an open combustion chamber;
• C - chimneys for boilers with closed camera combustion.

In high-rise buildings you can find a variant of a collective chimney, to which individual boilers are connected. This chimney goes to the roof

Coaxial chimneys are mounted in two positions:

• vertical;

• horizontal.

Only the installation method differs, but the principle of operation of the chimney is the same. Like everyone else engineering systems, it has both advantages and disadvantages. Let's look at them.

Advantages

Structurally, the chimney consists of two pipes, one acts as an outer shell, the other as an inner shell. Combustion products - exhaust gases - are discharged through a pipe of smaller diameter. Air enters the combustion chamber of the boiler through the outer pipe to maintain combustion. This system provides a compact and aesthetic appearance and takes up little space. The system ensures heating of the incoming outside air with exhaust gases, which increases the efficiency of the boiler.

Another important advantage of this system is its fire safety. When withdrawing flue gases they are cooled by air that enters the combustion chamber of the heating unit, reducing the risk of fire to zero. Additional insulation of the chimney with highly flammable materials is not required.

A similar chimney system can be installed on Various types boilers:

• on gas;
• on liquid fuel;
• on solid fuel.

Disadvantages of a coaxial chimney

Freezing. This is probably the main and most serious drawback when installing a horizontal chimney.

The first models of coaxial chimneys that appeared on the Russian market were not designed for such low temperatures operation - -15 - -30°С. They are designed for countries with milder climates. As a consequence, there is the possibility of freezing of the chimney and failure of the heating unit.

Although not all experts are so categorical. In their opinion, main reason freezing of a coaxial chimney is due to incorrect thermal engineering calculations. In this case, the boiler efficiency depends on the supply air temperature. In pursuit of increasing efficiency, designers reduced the diameter of the exhaust pipe. In this case, the temperature of the flue gases drops below the dew point, which leads to an increase in condensation formed inside the exhaust pipe and freezing. To reduce the effect of this factor, it is necessary to increase the temperature of the flue gases by increasing the diameter of the pipe. A properly selected coaxial chimney should not freeze.

When installing a vertical coaxial chimney, we are faced with the problem of collecting condensate. Since the problem is known to all manufacturers, models of coaxial chimneys designed for vertical installation, equipped with a condensate collector.

Rules for installing a coaxial chimney for a gas boiler

When installing a coaxial chimney yourself, you must read the manufacturer's instructions. Be sure to follow the rules for installing a coaxial chimney.

• During installation, use only materials and components that have been tested by the state gas inspection; It is prohibited to make any changes to the configuration and design of the chimney.
• During installation, it is prohibited to use materials not from the chimney manufacturer; Purchase necessary additional components only from service centers.
• All parts of the chimney are firmly connected and tested for flue gas leaks.
• Use of sealants and adhesive compositions forbidden.
• It is forbidden to join pipes within the thickness of the wall; it is necessary to provide a joint location outside the wall.
• A horizontal coaxial chimney is installed (unless otherwise specified by the boiler manufacturer): for condensing boilers 2-3° towards the boiler, for classic 2-3° outwards, ensuring condensate drainage and preventing precipitation from entering the boiler.
• The length of the coaxial chimney depends on the boiler model, the complexity of the chimney route and ranges from 1 to 7 m. ( maximum length with a straight-line installation for a boiler with an installed turbine with a power of more than 30 kW.).
• It is prohibited to install a coaxial chimney outlet below ground level into a window pit in a semi-basement.
• Remember, the installer is responsible for breakdowns and accidents during the operation of the chimney.

Coaxial chimney installation diagram

The exit of a coaxial chimney through the enclosing structures must comply with a number of rules and requirements. Since type C boilers have a closed combustion chamber, they can be installed in all types of premises. Regardless of the presence of windows in the ventilation system and the volume of the room itself, several standards must be adhered to. The photo shows the requirements for installing a coaxial chimney in different versions:

• a - the minimum distance from the axis of the chimney to any opening element of the facade of the house;
• b - the minimum distance from the axis of the chimney to any air intake;
• c - minimum distance to sidewalks (to reduce the distance, install a grille with a deflector, in this case the distance will be 0.15 m);
• d - minimum distance from the ground;
• e - the minimum distance from the axis of the chimney to the wall at an angle of 90° with opening elements or air intake openings; (0.15 m with a deflector);
• f - the minimum distance from the axis of the chimney to the wall at an angle of 90° without opening elements;
• g - minimum distance to green spaces;
• h is the minimum distance to the drainage system or vertical pipeline.

Choosing a coaxial chimney

When choosing a coaxial chimney, first of all you need to pay attention to the recommendations of the boiler manufacturer. There have been cases when service center did not accept the equipment for warranty through the installation of a coaxial chimney, which was not recommended for this boiler.

A coaxial chimney must ensure not only the removal of flue gases, but also completely ensure the intake of oxygen from the street, so the reliability of its operation is very important. It is worth choosing from proven foreign brands: Baxi, Vaillant, Navien, Ferroli, Ariston, Viessmann.

Coaxial chimney Baxi

Chimneys are made from of stainless steel and high strength polymer materials. The standard kit includes a 1 meter long chimney pipe, a 90° elbow, a wind protection nozzle, and decorative rings. If it is necessary to use an extension cord, it must be purchased separately. It should be noted that for a chimney up to 1 m long it is necessary to install a narrowing diaphragm on the boiler air duct. The procedure is carried out to compensate for draft, since the boiler fan is designed for a maximum chimney length (5m), and in the absence of a diaphragm, it will flow into the combustion chamber a large number of air, which will lead to a decrease in boiler efficiency. To protect against freezing, the coaxial pipe should protrude from the wall to the length of the tip, no more. If the length of the pipe is longer than necessary, the excess is cut off from the inside.

Photos of the main Baxi coaxial chimneys:

Coaxial chimney Vaillant

Vaillant company completes boilers own production coaxial chimneys. Compliance with the size of the pipes is the key to successful operation of the boiler. Also, Vilent coaxial chimneys can be purchased for boilers from other manufacturers.

Coaxial chimney Navien

Navien smoke removal systems from the Korean company are well established in the heating equipment market. Chimneys are produced for wall-mounted and floor-standing boilers with a power of up to 75 kW. The cost of Navien coaxial chimneys is slightly lower than their European competitors, while the quality of workmanship is not inferior to them.

• 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 the outer pipe, it is warmed by the exhaust pipe, 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 fuels. 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.

  • Supply pressure natural gas should not be more than 0.03 kgf/cm 2 (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 right place the location of the heating system and the beginning of the chimney inlet, 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.

  • Outer pipe When outputting, it should have a slight slope. 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. Leave between the ceiling and the chimney air gap and attach mineral non-combustible insulation. The chimney outlet is completely sealed. The joint is securely covered with a special apron.

  One of the most effective means to heat the house is a heating system connected to a gas boiler. Boilers using gas as fuel warm up quickly enough and maintain good temperature regime and inexpensive to operate. In addition, a good gas boiler often also provides water heating, which is very convenient and profitable.

  An important component heating system The pipe that allows the boiler to operate is a pipe that discharges combustion products into the atmosphere. The removal of combustion products can be carried out by coaxial pipes for gas boilers, which will be discussed in this article.

  Problems with conventional chimneys

  As mentioned above, one of the main problems that arise when using gas heating equipment is the removal of combustion products from the system. This is a serious drawback, and most other heat sources do not have this quality - but here you have to take care of removing carbon dioxide and carbon monoxide.

  To remove these substances, chimneys are used, which may have different designs and be created from different materials– metal, ceramics, brick and many others. The installation and characteristics of a chimney directly depend on its purpose, design features and other parameters.

  
  

  All chimneys that fit this description, in addition to their advantages, also have a lot of disadvantages. Firstly, it is worth noting the problem associated with the exhaust and supply of air through one pipe - sometimes this leads to deterioration in the operation of the system. However, this problem seems insignificant compared to the next one.

  Secondly, any chimney becomes clogged over time, as a result of which the draft in the boiler becomes much worse. If you leave a clogged chimney for a gas water heater in an apartment without attention, then at some point it will become completely clogged and the heating system will stop working. In addition to stopping the heating, a clogged chimney also threatens that gas combustion products will enter the living space - and this should not be allowed under any circumstances.

  Installing a coaxial pipe for a gas boiler as a solution

  The problems described above are quite unpleasant, but technology does not stand still, and construction industry was no exception - coaxial pipes began to be used as chimneys. A coaxial pipe is a structure that includes two pipes, one of which is located outside, and the second, respectively, inside.

  The inner tube has a smaller diameter - the standard value is usually about 60 mm. However, sometimes a larger diameter of the coaxial pipe for a gas boiler is selected. It will not be possible to use a pipe with a diameter of less than 60 mm as a chimney - such a cross-section is not enough to effectively remove combustion products. In addition, the small diameter of the chimney often causes complete clogging with various deposits, even taking into account the low susceptibility of the coaxial pipe to this factor.

  
  

  The outer pipe has a larger diameter - the average value for a 60 mm inner pipe is 100 mm. Simple calculations allow us to say that the dimensions of the pipes are in a ratio of 1:1.5. A pipe with a diameter of 100 mm ensures a continuous supply of air to the boiler. In addition, the outer shell is necessary to drain condensate that is released on the inner pipe.

  Regardless of the selected sizes of coaxial pipes (and their configuration may differ significantly from standard values), installation of the coaxial pipe of a double-circuit gas boiler is carried out using clamps and special fasteners. During installation, it is necessary to ensure that there is no direct contact between the two pipes - in fact, the coaxial nature of the structure implies the presence of a biaxial mechanism.

  Advantages and disadvantages of such a solution

  Coaxial pipes in combination with gas heating equipment ensure high-quality operation of the entire system. This is largely due to the positive qualities inherent in the type of chimney in question.

  The main advantages of coaxial pipes are as follows:

  • Significant increase in the efficiency of the heating system;
  • Safe and permanent removal of combustion products;
  • Good protection of the structure from clogging;
  • Condensate is removed from the system through a safe circuit, and air enters the system through a separate pipe;
  • Low probability of problems occurring;
  • Simplicity of design with high efficiency.

  
  

  All these advantages together seriously increase the efficiency of the system as a whole. For example, a constant supply of fresh air through an external pipe provides the system with the oxygen necessary for combustion. Condensation is also retained on the outer pipe and gradually dries, so the inside of the system is protected.

  The condensate aspect is very important - most of the internal damage to the system is caused by it. As a result of the release of condensate and the accompanying oxidation processes, solid deposits appear on the surface of the pipe, which subsequently must be cleaned. The use of a coaxial pipe with its special characteristics makes cleaning the structure much easier.

  
  

  However, coaxial pipes also have several disadvantages, including:

  • High cost of materials;
  • Standardization of pipes does not allow the creation of individual configurations;
  • Installing a coaxial chimney is very difficult to do on your own;
  • During installation, it is necessary to comply with a number of safety requirements, which is not always possible to do.

  Requirements for installation of coaxial pipes

  To realize all the positive qualities of a coaxial chimney, the following requirements must be met:

  1. The slope of the pipe from the axis should be about 3 degrees. This requirement will allow the system to independently remove condensate from the pipe. Otherwise, moisture removal will occur too slowly, resulting in the system becoming clogged and unable to perform its functions.
  2. The pipe outlet should be located at a height of 1.5 meters from the ground and at a distance of 0.6 m from the nearest window.
  3. When installing individual structural elements, it is necessary to use fittings, avoiding various handicraft methods of connecting pipes. In addition, it is undesirable to bend the pipe more than three times - an excessive number of turns reduces the strength of the structure.
  4. The length of the coaxial pipe for a gas boiler can only be increased with the help of special sealants or mastics purchased from pipe manufacturers. Inappropriate materials may cause damage to the integrity of the chimney.

  Installation of a coaxial pipe of a gas boiler, carried out in compliance with these requirements, will allow you to assemble a reliable and high-quality structure.

  Installation of coaxial pipe

  Installation of a coaxial pipe of a gas boiler belongs to the category complex processes– the design is not simple, and the requirements for it are quite serious. In addition, you need to think in advance about how to install the pipe according to the simplest possible scheme, so as not to complicate the already problematic installation.

  The process of installing pipes for different boilers is practically the same. For example, you can take a standard chimney, which includes pipes with a diameter of 100 and 60 mm (external and internal pipes, respectively).

  
  

  The installation algorithm for coaxial pipes is as follows:

  1. First you need to prepare all the equipment and design the future structure.
  2. In all ceilings and obstacles through which the pipe will pass, it is necessary to drill holes, the size of which should be 10 mm larger than the diameter of the outer pipe. A 10mm tolerance is required to install the fasteners.
  3. The base is connected to the boiler outlet. Most boilers have the outlet on the top, so there shouldn't be any problems.
  4. Next, the lower part of the pipe is installed. Its fixation is carried out using clamps and fittings.
  5. After installing the first section, you can begin installing the remaining elements of the coaxial chimney.
  6. The pipe connections must be treated with sealant or similar material.
  7. Final stage– checking the system for operability, for which you need to conduct a test run.

  The pipes must be connected tightly and efficiently - its operation depends on how well the sections of the chimney are joined. The outer and inner pipes must be located on the same vertical axis and strictly parallel to each other - any contacts are unacceptable. As practice shows, a small displacement occurs during operation, but it is insignificant and does not affect the performance of the system.

  It is best to keep the number of fittings and elbows to a minimum. According to the requirements, 3 fittings or 2 elbows can be installed on a three-meter piece of pipe, but this is the maximum permissible quantity - the smaller it will be various connections, the more reliable the design will be.

  Conclusion

  Installing a coaxial pipe for a gas boiler is quite complicated, but in the future it pays off in the efficiency of the heating equipment. When designing and installing, it is necessary to take into account all the nuances and approach the work with all care in order to create the most reliable and high-quality design.

  Content

  Boiler units for heating a private house, operating on gas fuel, need to install a chimney. Performance and efficiency autonomous system heat supply largely depends on the intensity of air supply to the burner and the removal of flue gases to the outside. Coaxial chimney for a gas boiler – best option for heating units with a closed combustion chamber. It is fundamentally different in design and functionality from the classic chimney. It is important to know the installation rules and follow the installation technology of this chimney in order to eliminate problems during the operation of the boiler during the heating season.

  Coaxial chimney

  Operating principles

  The coaxial pipe design consists of two pipes different diameters- one of them is inserted into the other and secured with jumpers so that the walls do not touch. The axes of both pipes must coincide.

  The double pipe allows for simultaneous air flow from the street into the firebox (through the outer ring-shaped passage) and exhaust of flue gases (through the central channel). As a result, a boiler with a closed combustion chamber operates without taking in air and without burning oxygen in the room. This allows you to install units with a closed combustion chamber not only in a specially equipped boiler room, but also in other rooms of the house within the framework of SNiP requirements.

  During operation of a gas boiler, hot flue gases move outward through the inner pipe, while giving off their heat to the air moving in the opposite direction along the gap between the inner and outer pipes. Due to the fact that the combustion chamber is heated and not cold air, the efficiency of the boiler increases, since it does not need to consume thermal energy to heat the incoming air.

  
  Principle of operation

  Due to the fact that air from the street moves along the outer contour of the coaxial chimney, the outer pipe of the device does not overheat, and this ensures fire safety and simplifies the installation of pipe passages through the wall, ceiling, and roof. It is also worth noting the compactness of the coaxial chimney and attractive appearance, easier installation compared to the traditional option. This is especially important if the boiler is planned to be installed in an already constructed building in which the presence of a chimney pipe was not provided for.

  Vertical and horizontal version

  Depending on the installation location, two types of coaxial chimneys for floor-standing and wall-mounted gas boilers can be distinguished:

  • Horizontal. The most common option due to ease of installation. To bring the pipe outside, a hole of the required size is punched in the wall - this makes it possible to use the boiler in an apartment building or install the unit in any suitable room of a private house. The advantages of a horizontal chimney also include the short length of the coaxial chimney and the absence of the need to install a condensate drain - the moisture will flow to the street through a pipe installed at an angle.
  • Vertical. Like traditional trumpet to remove flue gases, it is mounted with an exit through the roof. This option is more expensive due to the large length of the double pipe and the arrangement of penetrations through the floors and roof. The condensate drain device also increases the cost of the design and complicates the operation.
  
  Vertical version

  The choice of installation principle for a coaxial chimney is based on the characteristics of the boiler, the specific location of the boiler unit, and climatic conditions. If the pipe is mounted vertically, it passes through heated rooms and the incoming air has time to warm up, thereby reducing the volume of condensate and increasing the efficiency of the boiler. The vertical chimney is suitable for any type of boiler and provides good draft. The disadvantages of the horizontal design include poor draft - this option is only suitable for boiler units with an exhaust fan.

  Choosing a slope

  A horizontal chimney in cold climates often freezes in winter - the cold air in the outer pipe manages to cool the flue gases, as a result, condensation forms and freezes on the inner walls, gradually blocking the outlet. This effect is observed if the slope of the chimney pipe is made outward for reasons that condensate will drain to the ground.

  Note! An outward slope is not recommended, since condensate is toxic and its entry into the ground is harmful to the environment. Accumulated condensate must be disposed of in a specially designated place.

  
  Condensate freezing when the pipe slopes outward

  Practice shows that the outward slope of the pipe can be chosen in regions with a mild climate. If winters are severe, it is recommended to slope the pipe inward and install a condensate receiver so that moisture does not enter the combustion chamber, reducing the efficiency of the boiler.

  Insulating the outer part of a coaxial chimney is not an effective measure in combating freezing of a pipe mounted with an outward slope. More practical option will be the use of a special kit that is resistant to icing. This coaxial chimney is equipped with an extension nozzle for the central pipe through which flue gases are discharged. There is a protective spiral inside the nozzle. The air intake holes of the outer pipe are located in its lower part at the edge.

  Installation rules

  Before you start installation work you should study the requirements for installing a coaxial chimney. Rules and regulations largely depend on the chosen option for installing the pipe - horizontally or vertically.

  
  Installation conditions

  Installation standards for a horizontal chimney:

  • The kit is selected in accordance with the diameter of the gas boiler outlet pipe - you cannot use a chimney pipe of a smaller cross-section. The size of the pipe is indicated in the documentation for the boiler unit.
  • The maximum length of a horizontal coaxial pipe is 3 meters. Manufacturers of boilers with fans increased power may allow the use of longer pipes. In this case, each turn of the chimney reduces the permissible length by 0.5 meters.
  • The slope of the condensate removal pipe must be at least 3° per linear meter.
  • The recommended distance from the boiler outlet to the hole in external wall is half a meter to a meter. In this case, the temperature of the flue gases will be sufficient to prevent internal icing of the pipe in frosty weather.
  • The distance from the window, door to the outlet of the coaxial chimney is at least 0.5 m. It is not recommended to route the pipe under the window, but if there are no other options, then the minimum gap between the chimney outlet and the bottom of the window is 1 m.
  • The outlet of the pipe must be located at a height of at least 2 m from the ground surface.
  • The gap between the pipe and the edges of the hole in the wall is 5 cm for wooden wall, 1 cm for brick or block construction. The gap is filled with non-flammable heat insulator (basalt wool).
  • If the pipe is located outside under a balcony or canopy, then you need to correctly calculate its length. The protruding part of the chimney must extend beyond the circle segment bounded by the wall and the lower part of the balcony or canopy with a radius equal to the width protruding beyond the plane of the wall of the structure. The closer the pipe is to the structure, the longer its outer part should be.
  
  Horizontal design of coaxial pipe

  The installation standards for a vertical coaxial chimney provide:

  • Assembling elbows by inserting subsequent elements into the previous ones to ensure free drainage of condensate. To prevent moisture from leaking out, the joints are sealed by tightening them with clamps.
  • A tee is installed at the bottom of the structure, which collects condensate and allows you to check and clean the chimney.

  Important! It is prohibited to install a deflector on the head of a vertical coaxial chimney, as this can lead to icing and blockage of the pipe. To protect the outlet from precipitation and wind, install a cone-shaped tip.

  Main stages of work

  It is permissible to install a coaxial chimney on our own, if you have skills in working with power tools. When equipping a double-circuit or single-circuit gas boiler with a double chimney, you will need:

  • Do it in the wall (or in the ceilings and roofing pie, If we're talking about about a vertical chimney) holes, the diameter of which must meet the requirements of SNiP.
  • Connect the adapter to the boiler outlet pipe.
  • Attach the assembled coaxial pipe to the adapter, if necessary using a corner element to connect the chimney to the wall (all joints are fixed using crimp clamps).
  • Lead the pipe through the hole made (if we are talking about a horizontal chimney, it is necessary to maintain a slope for condensate drainage).
  • Fill the gap between the pipe and the wood building structures non-flammable heat insulator ( basalt wool, fire resistant polyurethane foam), if the wall is brick, a heat insulator is not required.
  • Install the decorative trim.

  Installation nuances

  To correctly connect a two-channel chimney, you should study the boiler manufacturer’s instructions, where all technological subtleties taking into account parameters heating unit. The coaxial chimney exhaust is designed for use in conjunction with a boiler whose power does not exceed 40 kW - when operating more powerful units, the draft is insufficient, which reduces efficiency, generates a lot of condensate, and increases the risk of icing and blockage of the chimney.

  
  Installation features

  Adapter for boiler unit pipe. It is incorrect to use a homemade replacement instead of a standard adapter, for example, a piece of stainless steel pipe of suitable diameter. This leads to the penetration of flue gases into the room and prevents the chimney from working normally.

  Installation features. A two-channel chimney is mounted “on condensate” - the upper element must be inserted into the lower one. This should be taken into account when installing a pipe inclined outward to drain condensate to the ground. If necessary, use standard elbows to rotate 90 and 45 degrees. The joints should be sealed with special clamps; it is prohibited to use silicone sealant– it destroys the standard sealing elements.

  Pipe extension. To extend the chimney, it is allowed to use only standard elements. Cannot be attached to an existing pipe homemade designs made of stainless steel or other material.

  Anti-icing. The appearance of icicles on the outer part of a two-channel chimney indicates incorrect calculations or installation errors. As additional measures to protect the pipe from icing, install a special unit - an anti-icer.

  
  The length of the outer part should be no more than 0.5 m

  Wind protection. It is important to prevent wind from blowing into the chimney and creating reverse draft, otherwise carbon monoxide will penetrate into the room, causing poisoning. To avoid such a danger, you must:

  • correctly position the part of the pipe protruding outwards, observing the distances from window and doorways, protruding structures, neighboring buildings and other objects;
  • install special wind protection and diaphragm ( mandatory measure for regions with strong winds).

  Organization of space. In the gap between the boiler and the wall through which the coaxial chimney is routed, you cannot install any structures or store materials or things.

  Examination . Before putting a gas boiler unit into operation, it is necessary to check the presence and intensity of draft.

  Ventilation requirement

  A two-channel chimney allows air to be supplied to the combustion chamber through a pipe, so that the heating unit does not burn oxygen in the room. However, the room where the boiler is installed needs good supply and exhaust ventilation.

  The hood prevents accumulation carbon monoxide indoors, if the installation of the coaxial chimney is performed incorrectly, reverse thrust or the chimney is clogged with frozen condensate. Constantly updating the air in the room will reduce the risk of poisoning in the event of a chimney failure.

  Besides, ventilation system helps maintain indoors optimal level humidity, which prevents corrosion of metal elements of equipment.

  Advantages of a two-channel chimney

  The main advantage of using a coaxial type chimney is the reduction in the boiler’s consumption of oxygen from the room, since air enters the firebox through the external passage channel of the chimney. As a result, in terms of the effect on the atmosphere in the room, a gas boiler unit with a closed combustion chamber is similar to a single-burner gas stove. This allows you to reduce the requirements for the installation site of the heating unit and do without the mandatory installation of an efficient supply ventilation. According to the regulations, a gas boiler equipped with a closed combustion chamber and a coaxial chimney can be installed in an unventilated room.

  
  Boiler with two-channel chimney can be installed in an unventilated area

  The advantages of this smoke exhaust system also include:

  • quick and simple installation due to the use of ready-made elements equipped with seals and clamps for fixation;
  • reduced fire hazard because outer surface the coaxial pipe heats up slightly (overheating is prevented by the flow of air from the street through the outer ring-shaped channel);
  • versatility of use - the coaxial chimney can be installed on boiler units of various types;
  • the possibility of installation in an already built house with minimal intervention in the layout, in which a chimney was not initially provided;
  • suitability for use in apartment buildings;
  • high traction rates, provided that the installation is carried out according to all the rules.

  Thanks to the list of advantages, this smoke removal system has gained wide popularity all over the world.

  Disadvantages of coaxial chimneys

  The two-channel flue gas exhaust system also has a number of disadvantages, which include:

  • The need for coordination with sanitary and epidemiological supervision, since condensate must be disposed of in specially designated areas, which must be reported to the supervisory authorities. First of all, this concerns the installation of common coaxial chimneys in apartment buildings. Representatives of the gas service simply warn owners of private houses about the danger of toxic condensate and the inadmissibility of draining it into the sewer or getting on the ground.
  • Sensitivity to correct installation. Even small errors in installation can lead to a decrease in draft, the formation of an increased amount of condensate, and pipe icing.

  Common installation mistakes

  If a coaxial chimney pipe is installed by a non-professional, there is a risk of disrupting the technology, and improper installation leads to problems in the operation of the boiler and chimney. It is recommended to entrust the entire range of work to licensed specialists.

  
  Installation errors

  The most common mistakes include:

  • Incorrect calculations of the permissible pipe length. The longer the channel through which the flue gases move, the more they cool and at the exit they can no longer heat the incoming air. At the same time, the amount of condensate increases and on frosty days it freezes on the walls of the head and forms icicles. This results in a decrease in draft, deterioration in the operation of the boiler and can lead to carbon monoxide entering the room if the outlet channel of the pipe is completely clogged.
  • Insufficient slope of a long horizontal pipe. If the slope towards the condensate collector on a long pipe is insufficient, there is a higher risk of it freezing at the tip.
  • Lack of condensate collector on long horizontal or vertical pipe. If the chimney passing through the wall is short, the flue gases do not have time to cool enough for moisture to condense, and if the pipe is long, it is important to install a tee with a moisture collector, otherwise it will enter the combustion chamber of the boiler, reducing the efficiency of the unit.
  • Failure to comply with fire safety standards when installing a chimney through wooden structures. The head of the pipe should be located no closer than 60 cm from the wooden wall.
  • There is no de-icer or wind protection diaphragm on the horizontal chimney.

  A coaxial chimney for wall-mounted gas boilers will ensure optimal operation of the heating unit and will last long term only on condition correct installation, using only standard system elements and special protective equipment.