Types of chimneys for a gas boiler


Gas boilers are a very popular solution in places where there is access to a centralized gas supply. To ensure reliable and efficient heating of a house with a gas boiler, it is necessary to choose the right material for the chimney and carry out its installation in accordance with accepted standards. In this case, mistakes must not be made, since they will lead to a deterioration in draft, therefore, combustion products will not be completely removed, which will negatively affect the efficiency of the boiler. Gas consumption will increase, so heating costs will increase. In addition, improper operation of the chimney can pose a threat to human life, since combustion products, instead of being discharged outside, can enter the room. Redesigning a chimney is not only expensive, but also time-consuming, so before installing it, you need to familiarize yourself with how to do it correctly, and take into account the advice and recommendations of specialists.

Features of the chimney device for a gas boiler

One of the most popular types of fuel is gas, therefore gas boilers are a common and demanded equipment. During gas combustion, the temperature of the products discharged through the chimney does not exceed 150-180 degrees. This fact largely determines the requirements for the materials used to create the chimney.

When building a new house, the type of heating equipment is foreseen in advance, and its project is also being developed. If it is necessary to install a gas boiler in an old building, its reconstruction may be necessary.

To create a chimney for a gas boiler, different materials can be used, but all of its types, except for brick, have the following elements in their composition:

  • pipe - it can be of different lengths and diameters;
  • connecting pipes - necessary to connect the boiler and the chimney;
  • bends;
  • pass-through pipes;
  • cone for protection from natural precipitation;
  • a revision tee with a union through which the accumulated condensate is drained.

    A chimney inside a building usually has more fittings than an outside chimney

As part of the heating system of a house, the chimney is of great importance, since it serves to remove fuel combustion products. Not only the efficiency of the gas boiler operation, but also the safety of residents depends on how correctly it is executed and installed.

To correctly make a chimney, you need to familiarize yourself with the existing requirements for this element of the heating system. One or two boilers can be connected to one chimney, provided that the exhaust of combustion products is carried out into openings located at different levels at a distance of more than 50 cm from one another. Elbows can be at the same level, but cutting devices installed at a height of 50 cm or more must be used.

When installing two boilers located at different levels, the flue gas outlets must be at least 50 cm apart.

Of particular importance is the correct calculation of the chimney cross-section, while it cannot be less than the size of the boiler outlet. When several heating devices are connected to one chimney, its diameter is determined taking into account the simultaneous operation of all boilers.

Gas boilers have high efficiency, usually it reaches or even exceeds 95%, so the temperature of the combustion products will be low. But it must be borne in mind that this produces a large amount of condensate, which has a particularly negative effect on the brick chimney. To reduce the destructive effect of condensate on a brick, experts recommend casing such chimneys using a special pipe made of stainless steel, or lining with a corrugated pipe.

For a gas boiler, the optimal chimney section is a circle, its oval shape is allowed, and a rectangular configuration is rarely used, since it cannot provide high draft.

The following requirements are put forward for the chimneys of gas boilers:

  • The flue pipe must be installed vertically and there must be no ledges in it. In special cases, a slope of no more than 30 degrees is allowed;
  • the length of the vertical part of the pipe connecting the boiler and chimney must be at least 50 cm;
  • the total length of horizontally located chimney sections for a room of standard height should not exceed 3 m;
  • there should not be a slope towards the boiler, in exceptional cases it can be no more than 0.1 degrees;
  • there can be no more than three turns along the entire length of the channel;

    There should be no more than three turns in the chimney of a gas boiler

  • the condensate trap is installed below the pipe inlet to the gas boiler;
  • the distance from the connecting pipes to non-combustible surfaces must be more than 5 cm, and to combustible ones - at least 25 cm;
  • all connecting elements must have high tightness, therefore, one pipe into another must go no less than a length equal to half of its diameter;
  • the distance from the pipe to the parapet should not be less than 150 cm;
  • the height of the pipe installation depends on its distance to the ridge and should not exceed 50 cm when it is located closer than 1.5 m from the upper junction of the slopes. When the pipe is removed up to 3 m, it can be installed flush with the ridge, and in all other cases, the head height should be on an imaginary line drawn from the ridge down at an angle of 10o to the horizon;

    The installation height of the chimney head above the roof depends on its distance to the ridge

  • if the roof of the house is flat, then the chimney must be at least 1 m higher than it.

It is strictly forbidden:

  • use porous substances to create channels;
  • lay a chimney through rooms where people live;
  • install deflectors, as they interfere with the normal removal of combustion products;
  • lay the pipe through those rooms where there is no ventilation.

Table: arrangement of smoke ducts through the outer wall of the house without creating a vertical duct

Installation location of the bendThe smallest distances, m
to the natural draft boilerto the boiler with a fan
Equipment powerEquipment power
up to 7.5 kW7.5-30 kWup to 12 kW12-30 kW
Under the ventilation hole2,52,52,52,5
Near the ventilation hole0,61,50,30,6
Under window0,25
Next to the window0,250,50,250,5
Above a window or vent0,250,250,250,25
Above ground level0,52,22,22,2
Under parts of the building that protrude more than 0.4 m2,03,01,53,0
Under parts of the building protruding less than 0.4 m0,31,50,30,3
Under another bend2,52,52,52,5
Next to another bend1,51,51,51,5

Video: features of the chimney device

Materials used for the chimney of a gas boiler

You can choose different materials for creating a chimney, but they must:

  • have high resistance to the negative effects of harmful and aggressive substances;
  • do not pass combustion products through the walls and joints;
  • have a dense and smooth surface.

For the correct choice of material for the chimney, you need to familiarize yourself with the pros and cons of each option.

Brick chimney

Until recently, brick was most often used to create a chimney for a gas boiler, but now other materials are usually used. This is due to the fact that the brick has a lot of weight, so a strong foundation must be erected to create it. You will not be able to make such a chimney on your own; you will have to invite a master.

Among the main disadvantages of a brick chimney, the following should be noted:

  • its walls are not smooth, so soot accumulates on them faster, which makes traction worse;
  • since the brick absorbs moisture well, it quickly collapses under the negative effects of condensation;
  • usually the cross-section of such a chimney has a rectangular shape, since it is difficult to make a circular cross-section, and for a gas boiler it is better that the chimney is cylindrical.

To eliminate the disadvantages of a brick chimney, it is enough to insert a pipe of the required diameter inside. It can be metal or asbestos, as well as corrugated pipe.

For the reconstruction of an old brick chimney, a stainless steel pipe is placed inside

When creating a combined chimney, you must adhere to the following rules:

  1. If the liner consists of several pipes, then all joints must be well sealed. There are no problems with sandwich pipes or single-walled metal products, and in order to achieve good tightness when connecting asbestos pipes, you will have to try. The use of ordinary cement mortar does not give the desired result, in this case it is better to use special water-repellent compounds or heat-resistant sealant, as well as hermetic clamps.
  2. To minimize the possibility of condensation formation, single-wall steel pipes installed inside a brick chimney must be additionally insulated. They do this with materials that are not afraid of moisture. Most often, basalt wool is used or a sandwich pipe is installed.
  3. The liner must have a condensate collector in its lower part, to which free access is provided.

If you carry out such a reconstruction of a brick chimney, then it will reliably, efficiently and safely serve for many years.

Chimney from metal pipes

Due to the fact that the temperature of combustion products in modern gas boilers is low, condensate is constantly and in large quantities formed in them. If there is good draft in the chimney, then the bulk of the condensate goes out with the smoke to the street, and if it is well insulated, the rest evaporates. If everything is done correctly, then although condensation is constantly formed, there will be a minimum amount of it in the condensate trap.

In order for pipes made of stainless steel to serve for a long time, they must withstand prolonged exposure to aggressive substances. Food grade stainless steel does this best, but is expensive.

Sandwich pipes are the best option for creating a chimney

To reduce the likelihood of condensation formation, the chimney pipe must not be allowed to cool, therefore it must be insulated. If a sandwich pipe is used for laying an external chimney, then to extend its service life it is better to perform additional insulation. To do this, you will need to lay only one layer of insulation, while when using a single-wall structure, at least 2-3 layers will be required. Although the cost of a single-wall pipe is lower than that of a sandwich structure, due to the need to use several layers of insulation, in the end result, their cost is practically equal. When creating a chimney for a gas boiler, it is best to use a sandwich pipe.

When using single-wall pipes, the part that is outside the residential part of the building must be well insulated

Installation of pipes when creating a chimney outside the building is carried out "by condensate", which means that the upper pipe is inserted into the lower one. If the chimney is laid inside the building, then it is done "through the smoke" - the upper pipe is put on the lower one, which prevents gases from entering the room.

Depending on whether the chimney is inside or outside the house, the assembly is carried out "by condensate" or "by smoke"

The reliability of a sandwich pipe will be higher than that of a single-walled pipe due to the presence of two layers of metal. If you decide to insulate a sandwich pipe, then you can take one with an outer pipe made of galvanized metal. It is cheaper than made of stainless steel, has no contact with condensate and is not visible under the insulation, so this solution will save money.

Ceramic chimney

The main advantages of a ceramic chimney are its high reliability and durability - the service life is 30 years or more. Ceramics are highly resistant to the action of the acid contained in the condensate that settles on the pipe walls. Such a chimney can be used with a boiler operating on any type of fuel, it provides good draft, heats up quickly and accumulates heat.

But it also has several drawbacks:

  • large weight - if the chimney is high, then its installation will require the creation of a powerful foundation;
  • complex device - it takes more time to install it than to install a sandwich pipe;
  • low mobility - there is no way to disassemble and transfer to another place;
  • high price.

    Ceramic chimney resists aggressive substances well, but is heavy

Chimney from asbestos pipes

In the past, asbestos pipes were often used to create the chimney of a gas boiler. This is due to the fact that the temperature of the combustion products is low, so this design can withstand it. The main advantage of asbestos pipes is their low cost. Among the shortcomings, it is worth noting the rough surface and the difficulty of sealing the joints. Do not use an asbestos pipe if the temperature of the combustion products is more than 250-300 degrees, as this can lead to damage to the pipe. It is imperative to study the boiler documentation to determine whether the selected material is suitable for creating a chimney.

When creating a chimney from asbestos-cement pipes, you must adhere to the following rules:

  • the chimney should be as straight as possible so that the joints are smooth;
  • it is necessary to seal the seams well, one of the best options is to use a cement mortar with the addition of hydrophobic additives, after which the joint is coated with a sealant that can withstand high temperatures;
  • in order to reduce the amount of condensate, the pipe must be well insulated and made high, then, due to the good draft, the condensate will fly out into the street.

Considering the fact that when using asbestos pipes you need to suffer with sealing joints, it is much easier to use stainless steel pipes to create a chimney, the installation of which is faster, and the price does not differ much.

Such stains occur due to poor sealing of asbestos-cement or metal chimney pipes.

Coaxial chimney

In this case, one pipe is placed inside the other, and they are connected to each other by thin bridges. You purchase a ready-made chimney, so its installation is quick and easy.

This solution allows you to remove combustion products from gas boilers in the absence of the possibility to install another type of chimney. Most often these are apartment buildings or structures in which there are no chimneys. Such a chimney can only be used with a boiler with a closed combustion chamber.

The main advantage of a coaxial chimney is that it simultaneously performs two functions: removing flue gases and supplying air to the combustion chamber.

The coaxial chimney is used with gas boilers with a closed combustion chamber

Installation of this type of chimney provides the following advantages:

  • air from the room is not used for gas combustion;
  • due to the fact that the incoming air is heated by the discharged fuel combustion products, the boiler efficiency increases and the gas consumption decreases;
  • such a solution allows the chimney to be led out not through the ceiling, as is usually done, but through the outer wall of the house.

For a boiler with an open burner, a flat vertical chimney is required, which can be built in two ways.

  1. A horizontal pipe is mounted from the boiler through the wall, which is taken out, after which it is connected to a vertical chimney.
  2. The pipe is led out through the ceiling and roof.In order to take the pipe away from the wall at the same time, you can install two elbows of 45o, straight knees are not recommended.

For a gas boiler with an atmospheric burner, you can make an internal or external chimney

When creating chimneys, both options are used, but making the outside is easier. In the case of an internal arrangement, it is difficult to create a passage through the floor and the roofing pie. To ensure fire safety in these places, special pass-through elements are used.

Video: types of chimneys

Calculation of the diameter

To calculate the diameter of the chimney, it must be borne in mind that this value is in direct proportion to the power of the heating device. The condition must be taken into account: the cross-section of the inner diameter must be constant along the entire length of the pipe.

When performing calculations, experts recommend that for each kilowatt of gas boiler power, there should be at least 5.5 cm2 chimney area. This is the optimum value, which ensures good draft, efficiency and safety of the gas boiler.

When installing a chimney from a sandwich pipe, only its inner diameter is taken into account

If we talk about such a parameter as the height of the chimney, then for a gas boiler it should be at least 5 m. The specific requirements for the location of the pipe head have already been discussed by us in the section "Features of the chimney arrangement for a gas boiler".

The calculation of the chimney diameter can be done in two ways.

  1. If you already have a gas boiler, then everything will be simple here. The diameter of the chimney must be equal to or slightly larger than the chimney of the boiler, therefore this hole must be measured and a pipe of the corresponding diameter must be ordered.
  2. If there is no boiler yet, but you know its performance, then the chimney diameter is calculated taking into account this parameter. It is necessary to multiply the boiler power in kilowatts by 5.5 and obtain the minimum allowable cross-sectional area in square centimeters.

When calculating the diameter of the chimney, it is necessary to take into account the passport, and not the thermal power of the boiler. For example, with a rated power of 1.5 kW, the thermal power can reach 38 kW, but a lower value is taken for the calculation.

Let's consider a specific example: let's say the boiler power is 24 kW.

  1. The minimum cross-sectional area of ​​the chimney should be 24 5.5 = 132 cm2.
  2. Since the chimney has a round shape, knowing its area, you can determine the diameter. For this we use the formula S = πr2, from which it follows that r = √S / π, that is, √132 / 3.14 = 6.48 cm. Thus, the minimum allowable chimney diameter is 6.48 2 = 12.96 cm or 130 mm.
  3. When finally choosing the diameter of the chimney, the value obtained must be corrected with the existing tables.

Table: dependence of the diameter of the chimney on the power of the gas boiler

Chimney diameter, mm100125140150175200250300350
Gas boiler power, kW3,6–9,89,4–15,37,1–19,213,5–22,118,7–30,424,1–39,337,7–61,354,3–88,373,9–120,2

Installation technology and features

For a gas boiler, you can make a chimney inside or outside the building. In each case, the owner independently decides how to mount the smoke channel, but to make it easier to decide, you can be guided by the data from the table.

Table: comparison of internal and external methods of chimney installation

Internal installation of the chimneyExternal installation of the chimney
The chimney, passing through all the rooms, heats them additionally, so only that part of it that is outside the living quarters needs to be insulated.It is necessary to carry out thermal insulation of the chimney along its entire length.
Since a large section of the pipe runs inside the building, there is a high probability of carbon monoxide entering it, and the fire hazard also increases.High level of safety, since even if carbon monoxide leaks, it will remain outside.
Since additional elements are used, the installation of the system becomes more complicated and its cost increases.Fewer chimney elements, so installation is easier and faster.
If it is necessary to carry out repair work, additional difficulties arise.Since the chimney is located outside the building, there is always free access to it, so repairs are simple and quick.

Comparing the data obtained, everyone will be able to decide for themselves in which way it is better to mount the chimney in his case.

The process of creating an internal chimney consists of the following steps.

  1. Marking is applied, the places of passages in the ceiling and roofing pie are marked.
  2. Make passages for the chimney pipe in the ceiling and roofing pie. If the floor is concrete, then a perforator is used for this, and in the wooden floor, the passages are made with a saw.

    It is necessary to make a passage for the pipe in the ceiling of the house, as well as in the roofing pie

  3. A branch is connected to the boiler, to which the tee is attached. A vertical pipe is put on top of the tee, and a condensate trap is installed at the bottom.

    The pipe and condensate trap are connected to the boiler using a tee

  4. Put on and, if necessary, build up a vertical pipe.

    Usually the length of one vertical pipe is not enough to create a chimney, so it is increased

  5. To pass through the ceiling, a special metal box is installed, the size of which must correspond to the diameter of the pipe. If a pipe with a diameter of 200 mm is used, then for it you will need a box measuring 400x400 mm, above and below which sheets of 500x500 mm are installed. The diameter of the holes for the pipe in the sheets must be 10 mm larger than the diameter of the chimney so that the pipe passes freely through it. To hide this gap, after installing the pipe, an entrenchment (special clamp) is put on it. The distance from the pipe to combustible materials must be at least 200–250 mm.

    The box for the passage through the ceiling can be purchased ready-made or made yourself from stainless steel

  6. If necessary, the pipe is fixed to the elements of the roof overlap, they do this every 400 cm.The pipe is fixed to the wall with brackets every 200 cm.

    If the height of the attic is large, then the pipe is additionally attached to the elements of the rafter system

  7. A roofing passage is installed and a pipe is passed through it.

    To design the passage of the chimney through the roofing pie, a special passage element is used

  8. At the last stage, the tip is mounted in the form of a cone.

    To protect the chimney from atmospheric precipitation, a cone-shaped tip is used

  9. In those places where the chimney comes into contact with flammable materials, it is necessary to install high-quality thermal insulation. Basalt wool is usually used for this. The insulation is fixed with fire-resistant mastic. After that, the passage through the ceiling is closed with galvanized sheets that come with the box, and if the box was made independently, then the sheets must be of such a size as to completely cover it. At the last stage, the tightness of all joints is checked. To do this, the boiler is started, and the joints are coated with soapy water. If problems are identified, they must be eliminated immediately.

    Basalt wool is used for thermal insulation of the chimney passage through the ceiling.

The procedure for installing the chimney outside the building will be slightly different.

  1. An element passing through the outer wall of the building is connected to the outlet of the boiler.

    A special passage element is used to lead the chimney through the outer wall.

  2. A hole is made in the wall. To make this process as fast and easy as possible, you can use a hammer drill.

    To bring the chimney to the street, a hole is made in the wall

  3. After installing the pipe, the hole between it and the wall is qualitatively sealed with basalt wool.

    After installation in the pipe hole, it is sealed with high quality

  4. A tee is attached to the outlet connected to the boiler. A vertical pipe is put on top of the tee, and a condensate trap is installed at the bottom.

    A tee and a revision are attached to the element protruding from the wall

  5. The vertical pipe is extended to the required height, while every 2 m, it is fixed to the wall using brackets. To protect against atmospheric precipitation, a tapered tip is put on the pipe head.
  6. All joints are fixed with clamps.

    To strengthen the joints, clamps are additionally used

  7. If a sandwich pipe was used, then another layer of thermal insulation can be laid for additional insulation. A minimum of 2-3 layers of insulation is placed on a single-wall pipe.
  8. Check the functionality of the boiler and chimney.

In order to avoid mistakes when independently installing a chimney for a gas boiler, the following facts must be taken into account.

  1. Coaxial pipes for traditional boilers are made from an alloy of aluminum and steel, they can withstand temperatures up to 110 degrees and above. For condensing boilers, the emission temperature is in the range of 40-90 degrees, it is often below the dew point. This leads to the formation of a large amount of condensation, which quickly destroys metal products. Chimneys made of special polymers are used for condensing boilers. The use of chimneys for other types of gas boilers is prohibited.
  2. Sewer pipes cannot be used to create a chimney for a condensing boiler, although many people try to do so. Plastic cannot withstand temperatures of 70-80 degrees for a long time, and this often happens during the operation of the boiler, therefore the pipes are deformed, and the tightness of the chimney is broken.
  3. To drain the condensate, it is necessary to make the correct slope of the chimney, in addition, the presence of a slope does not allow atmospheric precipitation to get into the gas boiler. Negative slopes should be avoided, as this leads to the accumulation of condensation and the malfunction of the fan.
  4. It is important to observe the correct assembly of the chimney: into the socket where the seal is located, the next pipe is inserted with the smooth side.
  5. During operation of the condensing boiler, up to 50 liters of condensate can form per day, which must be discharged into the sewage system. Condensation cannot be discharged outside, as many do by analogy with an air conditioner. In winter, the system freezes, so the boiler is blocked.

    Condensate must not be drained outside from the condensing boiler, as it will freeze in winter and the boiler will stop working.

  6. In the event that the sewerage level is higher than the boiler and spontaneous condensate drainage is impossible, a special pump with a reservoir must be installed, which will automatically pump out the condensate as it accumulates.

    To collect and drain condensate, if its spontaneous drainage is impossible, a special condensate trap is used

All work on the installation of the chimney, both inside and outside the building, must be performed carefully in order to obtain a sealed structure. The correct installation of the chimney will determine not only the quality of the heater, but also the safety of all residents of the house.

Video: installation of a sandwich chimney

Any heating device, and especially one that runs on gas, is a source of increased danger. All work related to the installation of a gas boiler, as well as the creation of a chimney, must be performed correctly and in accordance with existing standards. Before starting the installation of the chimney, all calculations must be performed correctly. If you are not confident in your abilities, then it is better to entrust the work on installing a chimney for a gas boiler to specialists.


How to make a chimney for a solid fuel boiler

Imperceptibly during the holidays, winter approached its middle. The traditional dacha planting chores will begin very soon. But while it is cold outside and February frosts are still expected ahead. Comfort and coziness in a home is associated with warmth. And whether it is enough in a country house directly depends on the heating equipment and its correct installation.


Chimney

One of the important elements of a solid fuel boiler is a chimney. Compliance with all the rules for its installation is a guarantee of not only stable efficient operation of the equipment, but also the fire safety of the building. Therefore, in continuation of the topic of installing solid fuel equipment, which dealt with the device of the boiler room, we will consider how to correctly make a chimney for a solid fuel boiler.


The installation of a chimney can be considered using the example of a double-circuit design.

Installation of chimneys for a gas boiler is carried out in the direction of the structure from the bottom up, that is, from the heating objects of the room towards the chimney. With this installation, the inner tube is pushed onto the previous one, and the outer tube is inserted onto the previous one.

All pipes are fastened to each other with clamps, and along the entire laying line, every 1.5–2 meters, brackets are installed to fix the pipe to a wall or other structural element. The clamp is a special fastening element, with the help of which not only the parts are connected to each other, but also the tightness of the joints is ensured.

The laid sections of the structure in a horizontal direction up to 1 meter should not come into contact with elements that pass near communications. The working channels of the chimney are located along the walls of the buildings.

Be sure to install a bracket on the wall every 2 meters of the chimney, and the tee is attached using a support bracket. If it is necessary to fix the channel to a wooden wall, then the pipe is lined with a non-combustible material, for example, asbestos.

When mounted on a concrete or brick wall, special aprons are used. Then we bring the end of the horizontal pipe through the wall and there we mount the tee required for the vertical pipe. It is necessary to install the brackets on the wall every 2.5 m.

The next step is to attach, raise the vertical pipe and lead it out through the roof. The pipe is usually assembled on the ground and the fastening for the brackets is prepared. The fully assembled volumetric tube is difficult to fit on the elbow.

For simplicity, a hinge is used, which is made when welding pieces of sheet metal or cutting a pin. Typically, the vertical pipe is pushed into the tee pipe and secured with a pipe clamp. Attaching the hinge to the knee is similar.

After lifting the pipe in a vertical position, the pipe joints should be bolted where possible. Then you should unscrew the nuts of the bolts to which the hinge was fastened. Then we cut or knock out the bolts themselves.

With the hinge selected, attach the remaining bolts to the joint. After that, we tighten the remaining brackets. We first adjust the tension manually, then we fix the cable and adjust it with screws.

Necessary distances to be observed when placing the chimney outside

The installation is completed by checking the chimney draft. To do this, bring a burning piece of paper to the fireplace or stove. Draft is present in case of deflection of the flame towards the chimney.

The figure below shows the distances that must be observed in various options for the location of the chimney outside:

  • when installed on a flat roof, the distance should not be less than 500 mm
  • if the pipe is removed from the ridge of the roof at a distance that is less than 1.5 meters, the height of the pipe must be at least 500 mm in relation to the ridge
  • if the chimney outlet installation is located at a distance of more than 3 meters from the roof ridge, then the height should not be more than the assumed straight line.

The setting depends on the type of channel directions required for the combustion of the fuel. In the interior of the room, there are several types of chimney directions:

Chimney support bracket

  • direction with rotation in 90 or 45 degrees
  • vertical direction
  • horizontal direction
  • direction with a slope (at an angle).

It is necessary to install support brackets for fixing the tees every 2 meters of the flue duct, it is necessary to provide additional fastening to the wall. Under no circumstances should horizontal sections be created above 1 meter when installing the chimney.

When installing chimneys, consider:

  • distance from metal and reinforced concrete beams to the inner surface of the chimney walls, which should not exceed 130 mm
  • the distance to many flammable structures is not less than 380 mm
  • cuts for non-combustible metals are made for passage of smoke channels through ceilings to the roof or through the wall
  • the distance from combustible structures to an uninsulated metal chimney must be at least 1 meter.

The gas boiler flue connection is carried out on the basis of building codes and the manufacturer's instructions. The chimney must be cleaned up to four times a year (see How to clean the chimney).

To optimally calculate the height of the chimney, it is necessary to take into account the type of roof and the height of the building:

  • the elevation of the chimney must be at least 1 meter when installed on a flat roof and at least 0.5 meters above a non-flat roof
  • the location of the chimney on the roof must be made at a distance of 1.5 meters from the ridge
  • the height of an ideal chimney is at least 5 meters.


Purpose of a coaxial chimney for a gas boiler

The main advantage of installing such a pipe is that the air in the room does not dry out, therefore, there is no need for frequent ventilation or the purchase of expensive climate systems. The air stream from the street, passing through the system, gradually heats up, improving the combustion process. Thanks to this, the gas burns out completely, and this increases the efficiency of the equipment.

You should know this! You can choose a pipe for any heating equipment. Manufacturers produce designs of different diameters and materials. In addition, the installation of a coaxial chimney of a gas boiler is easy to do with your own hands, and this is a significant budget saving.

Flow circulation principle


Differences between gas boilers by type of heating

The standard single-circuit gas boiler is intended for heating only. Its design allows water to be heated in a loop heating system. To heat water in such cases, gas water heaters or boilers are used. But this is unprofitable if a double-circuit gas boiler can be used. There is much more effect from such a device. In addition to the fact that you do not need to buy and connect additional equipment, it allows you to almost simultaneously heat water for use in the bathroom, shower, etc.

Gas boilers differ in the type of heating

Remember! Single-circuit gas boilers are used only for heating, double-circuit ones - for heating and heating water in unlimited quantities.

Electronic piezo-ignition devices are installed to ignite the boiler. Also, the combustion process is controlled by automation, which excludes the possibility of supplying gas to the combustion chamber in the absence of traction in it or in an extinguished state. Residues of combustion products are discharged due to natural exhaust or turbo compulsion.

Modern gas boilers are completely environmentally friendly


Pros and cons of condensing gas boilers

Let's talk about the best option for a heat generator for the heating system of a house - a condensing gas boiler.

To organize the heating system of a country house in the modern world, many different equipment are used. It can run on gas, electricity or wood. For those who are especially concerned about environmental safety, a condensing boiler is the best choice. Thanks to its high efficiency of 98%, it will also help to significantly save on fuel. Heating equipment manufacturers provide a wide selection of these units. You shouldn't worry about their high quality either, because the devices are manufactured using innovative technologies, reliable and durable materials.

  • Condensing gas boiler - working principle
  • Condensing heater device
  • Types of condensing boilers
  • Advantages and disadvantages of condensing boilers

The condensing gas boiler originated from the simplest gas-fired convection unit, with the most elementary operating principle. Natural or liquefied gas acts as a fuel for it. At the moment of its combustion, water and carbon dioxide are formed, releasing energy in large quantities. The heat carrier is heated by the released heat and circulates through the heating system of the dwelling. With this principle of operation, the efficiency is about 90%, the remaining 10 simply fly out into the street through the chimney. The condensing gas appliance developed by the engineers solved this problem.

In the unit, after burning fuel and transferring most of the heat to the heat exchanger, the condenser cools the gaseous combustion products to 50-60 ° C, thereby helping the development of water accumulation. Due to this, the efficiency increases, and, therefore, the volume of heat transferred to the coolant increases. Additional energy is also obtained due to the condensation of water vapor, which in conventional devices is lost when the vapor-gas mixture evaporates. The device takes the heat generated during this procedure and transfers it to the coolant. Thus, the efficiency of the device approaches 100%, because he can get almost everything possible from the combustion process. Moreover, such a high efficiency is achieved while reducing the consumed energy resources.

The design of a condensing boiler, although not essential, differs from a simple gas appliance. Its most important elements are as follows:

  • Primary heat exchanger.
  • Combustion chamber equipped with a fuel supply system, a burner and an air pumping fan.
  • Condensing heat exchanger.
  • Chamber for additional cooling of the steam-gas mixture up to 56-57 ° C.
  • Condensate collector.
  • Chimney that removes cold flue gases.
  • Pump for circulation of water through the system.

    In the primary heat exchanger, which is connected to the combustion chamber, the emitted gases are cooled to a temperature above the dew point. After that, the flue mixture goes to the condensing heat exchanger, where it is further cooled to less than 56 ° C. Steam accumulates on the walls of the heat exchanger, giving off the last heat. Condensate is collected in a tank, from which it is discharged through a pipe into the sewer. The heat carrier water moves in the opposite direction to the steam-gas mixture. When cold, it first heats up in a condensing heat exchanger, and then goes to the primary heat exchanger, where it heats up to the temperature desired by the consumer.

    The boilers themselves are made of stainless steel and silumin, the heat exchanger is cast, because the condensate is a mixture of diluted inorganic acids. Such materials allow to extend the life of the device, and the absence of seams - to prevent corrosion. To avoid the destruction of the chimney by a small amount of condensate falling on it, it is made of plastic or acid-resistant stainless steel.

    The burner helps to regulate the supply of heat at different times throughout the day. It can be simulated (allows you to gradually change the power during operation) or non-simulated (with a set value), while the burner switching frequency adjusts the device to the required parameters. In the best condensing gas boilers, simulated burners are often installed.

    This heating equipment is divided into:

    • double-circuit condensing boilers - in addition to heating, they also provide hot water supply, while the processes run synchronously and quickly
    • single-circuit - used only for space heating
    • floor-standing - they have high power, they are used to heat large areas of offices, industrial enterprises, apartment buildings
    • wall-mounted - used for residential premises of a small area.

    Before buying equipment, you should decide on its purpose, the area of ​​the premises that it should heat. If there is no need for hot water, then for a small cottage it will be advisable to take a wall-mounted single-circuit condensing boiler.

    The growing popularity is due to a number of advantages of condensing boilers:

    • saves fuel in comparison with a convection appliance by about 35%
    • on average 70% reduces harmful emissions comparable to traditional models
    • exhaust gases are cold, which makes it possible to install plastic flues, which are much more affordable than steel ones
    • the comfort level of the residents of the house is increased due to the low noise level
    • automatic operation thanks to smart electronics
    • long service life due to high-strength, corrosion-resistant materials
    • there is no need to allocate a separate room for the equipment, thanks to its small size and lightness, it can be easily installed in the bathroom or in the kitchen.

    The disadvantages of condensing boilers can be distinguished much less, but nevertheless, this almost ideal unit has them:

    • the high price of the device itself and the heat exchanger (therefore, you will have to regularly check the condition of the entire system)
    • condensate is difficult to dispose of
    • in high-temperature systems, the use of such equipment is impractical
    • the unit is highly sensitive to the quality of the intake air.

    The device is an innovation of the heating system, characterized by quality, environmental friendliness and high efficiency. Despite the high cost, it is safe to say that it is still worth buying a condensing boiler, because such an investment will certainly pay off, allowing you to save on heat carriers with maximum heat transfer.

    If you have any questions on this topic, ask the specialists and readers of our project here.


    When and how often to clean the chimney?

    If you have a fireplace (fireplace stove) with a closed firebox, the chimney should be cleaned at least once a year, before the start of the heating season. A long-burning stove with a constant firebox contaminates the pipe much faster: the layers of soot, which are terrible for their combustion, grow in just a couple of months. But gas and liquid fuel equipment gives its owners much less trouble: even with intensive operation, you will have to do chimney prophylaxis every 2 to 3 years. It is best to use a weighted metal brush for cleaning. In winter, when it is difficult to climb onto the roof, you can periodically add special preparations to the firebox, partially destroying creosote deposits.

    Comparative characteristics of "exhaust" of heating units with a thermal power of 10-12 kW Mass fraction of suspended solids in smoke,% Condensation *, l / day
    Flue gas unit type, С Temperature
    Fireplace with closed hearth Up to 400-600 40-50 0.5-1
    Fireplace stove with flue Up to 250-450 40-50 0.5-1.5
    Long burning oven 150-600 Up to 70 To 10
    Oil-fired boiler 150-300 15-25 0.4-0.7
    A gas boiler 140-250 10-20 0.2-0.4
    Low temperature boiler (gas, liquid fuel) Up to 120 5-7 Up to 15
    * When using a sandwich-type steel chimney with a length of 6 m, insulated with a 30 mm thick layer of mineral wool.

    Author: Well-known construction journalist V. Grigoriev. Drawing: M. Chernov. Photo: StroyExpertiza Plus


    Installation features:

    • The flue duct should not have more than two folds.
    • With horizontal flue pipes, the outward section must be sloped downwards by 3 ° to allow condensation to drain off. If the horizontal section enters a common flue gas outlet, the slope must be in the opposite direction (down towards the boiler).

    Frozen condensate at the outlet of the coaxial chimney.

    • The installation of a gas boiler with a closed combustion chamber does not require any windows or sashes in the room.
    • The installation must be carried out in such a way that the relative position of the boiler and the chimney cannot change during the subsequent routine maintenance.
    • The adapter, areas for inspection and cleaning, and the place for draining condensate should be accessible for periodic inspection.
    • It is not allowed to discharge the chimney below ground level.
    • The distance from the pipe to the wall of the adjacent building must exceed 8 meters. When installing the deflector, the distance can be reduced to 2 meters (for a blank wall) or 5 meters (for a wall with openings).
    • If the outlet is less than 1.8 meters above the ground, a deflector grille must be installed to keep out hot smoke.
    • In order not to impede the flow of smoke, when installing the chimney, the previous section is inserted into each subsequent (direction from the boiler).
    • If in the place where the horizontal chimney is installed, winds directed against the smoke exhaust prevail, a tin barrier is installed at the exit from the chimney. The distance from the outlet to the shutter must be at least 40 cm.

    Options for the location of a coaxial chimney in a private house and the minimum distance between the axis of the pipe and the nearest objects, m.

    Each chimney system must be supplied with detailed assembly and installation instructions. Before starting the installation, you need to compare the requirements set forth in the instructions with the requirements of the currently valid regulatory documents, and be guided by the more stringent ones.

    Variants of arrangement of coaxial chimneys with vertical outlet.

    The coaxial chimney and closed combustion chamber of a gas boiler eliminate the influence of the combustion process on the atmosphere inside the room, thereby increasing the comfort of people living in the house. Thanks to their positive qualities, chimneys "pipe in pipe" every year acquire more and more adherents among those who plan to equip a house with an efficient and economical gas heating system.

    Interior solution: decorative grilles for heating radiators

    Optimum thermal insulation for heating pipes

    Self-insulation of heating pipes on the street


  • Watch the video: New! The correct way to flue your Stanley stove


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