Requirements for installing a chimney for a gas boiler. Chimney for a gas boiler - design, calculation, insulation, requirements What pipe diameter is needed for a gas boiler
Careful calculations must be made before purchasing materials.
Below we describe how to calculate a chimney for a gas boiler. Formulas for calculating the cross-section and power of the heater are presented. In addition, you will be able to superficially familiarize yourself with the types of materials used for the construction of chimneys and their designs, as well as the requirements for the exhaust system.
First, let's look at the materials of chimney pipes. Brick ones have not been used for these purposes for a long time. This is due to the fact that the smoke released during combustion has a relatively low temperature, about 150 degrees. Based on this, its speed in the system will also be low. The smoke has time to cool down to the dew point temperature and condensation forms along the internal diameter of the chimney of the gas boiler. Moisture has an extremely destructive effect on brick. If it is possible to use a brick structure for the above-mentioned type of equipment, then only with a liner inside. Prefabricated structures are the most widely used. These are metal double-circuit and three-layer pipes. Therefore, you should choose one of them as a pipe for the chimney of a gas boiler.
Requirements for the installation of a chimney for a gas boiler
- there must be good traction;
- reliability and durability;
- corrosion resistance;
- resistance of the exhaust pipe for a gas boiler to chemically aggressive environments;
- ability to withstand high temperatures.
The height of the pipe depends on the cross-section and power of the equipment
In modern construction, only round or oval chimneys are used as outlets for fuel combustion products in heating systems. Almost no soot settles on their walls. It is also important that the surface of the internal diameter of the chimney pipe for a gas boiler is smooth. Structures with a square cross-section are more problematic to operate. Soot gets packed into the corners, then you have to get it out of there somehow, this causes a lot of hassle. Ideally, if you constantly use the heating system, you should inspect the exhaust pipe for the heating boiler twice a year. It is carried out by a knowledgeable person, a master. If the cross-section is round, then you can get by by calling a specialist only once a year.
Be sure to carry out preventive maintenance every year if we are talking about the house in which you live permanently. Call a professional before the start of the heating season. Otherwise, the soot, having accumulated, will reduce the diameter of the chimney for the gas boiler.
Types of combustion chamber designs
Before we move on to calculating the diameter of the chimney for a gas boiler, let's look at their types. The design of the combustion chamber matters more. The chamber in which combustion occurs may or may not be sealed. If it is not sealed, then oxygen to support the combustion process comes from the room in which the boiler is located. The heater has a special air duct in the lower part, through which air is supplied naturally. For such systems, only horizontal chimneys can be installed. These are metal double-circuit and ceramic sandwich pipes. If the design provides for the use of one chimney by two heaters, then the minimum height between chimney inserts for gas boilers should be more than half a meter. Even if the heaters are on the same floor.
Sealed combustion chambers take air from the street. For this purpose, a special chimney has been developed, which is called coaxial. The dimensions of a coaxial chimney for a gas boiler are much smaller than a conventional one. It is a metal pipe within a pipe. The smoke goes out into the street along the internal circuit, and through the external circuit it enters the boiler. To maintain circulation, a fan is installed at the top of the heater. This chimney can be installed both vertically and horizontally.
The standards for a chimney with a sealed combustion chamber provide for the installation of an individual outlet for carbon monoxide. It is impossible to connect two heaters to one coaxial system.
Calculation of chimney dimensions for a gas boiler
Calculations are carried out to determine the necessary parameters. What matters:
- cross-sectional area;
- The height of the chimney for a gas boiler is at least five meters, while the head must be at least half a meter higher than the roof ridge.
The draft depends on the correct calculation of the chimney diameter
Let's consider two possible options for calculating the chimney diameter for a gas boiler. The first option is when you have a heater and you need to calculate the cross-section of the chimney for it. Everything is very simple here. The ventilation should not be the same size as the stake pipe. Simply measure the smoke outlet hole at the top of the heater and you're done. If you cannot do this because it is not in stock, for example, when you ordered it and are waiting for delivery, the cross-section can be calculated based on the power of the gas equipment. In any case, you will know its characteristics. To calculate the cross-sectional area of the chimney, you need to multiply the heater power in kW by 5.5. The result will be calculated in square centimeters.
Before calculating the diameter of the chimney for a gas boiler, read the heater data sheet. For calculations, take not the thermal power, but the nameplate power. For example, for a unit with a nameplate power of 1.5 kW, the thermal heat can reach 38 kW. Insert a smaller value into the formula, otherwise you will be horrified by the result.
If you need to connect two gas heaters to one chimney, and this is allowed by fire safety standards, you should take into account the total power of both units.
The second option is when there is already a chimney. There is no need to calculate the diameter of the exhaust pipe of a gas boiler, since it can simply be measured. But you can find out the degree of productivity of equipment that is suitable for this system using the formula:
If the boiler chimney pipe diameter calculations are not done correctly, the hood will not work as it should. More than half of fires start due to a faulty chimney. Take this seriously.
The internal size of the chimney pipe should be either the same as the diameter of the chimney hole in the gas boiler, or slightly larger. Increasing the cross-section, of course, will affect the draft, but it will be there, and carbon monoxide will not enter the room.
Rules for installing chimneys for gas boilers
In order for the system to have good traction, the following technical requirements must be observed when installing a structure made of double-circuit pipes:
- assembly is carried out from the heater;
- the smoke channel must be smooth;
- there should be no bends along the entire length of the chimney for a gas boiler;
- to have good traction, it must be at least five meters in height;
- two bends are allowed at an angle of 45 degrees and one at a right angle. Moreover, these segments should be no more than one meter;
- the structure must be rigid, for this it is attached to the wall at a certain distance;
- the umbrella should rise above the roof ridge by at least 50 cm;
- Do not neglect the installation of additional elements, such as a moisture accumulator, a purifier and a head.
The parts of the metal sandwich pipe are fastened with rivets at the joints. Additionally, you can put on a clamp to hide the fasteners. Where the structure passes through walls and ceilings, a metal screen is installed. This is a square sheet of tin with a round hole in the middle. Special heat-resistant wool is placed into the resulting void between the warm lining of the chimney and the ceiling material. It looks like mineral wool, and foil is glued to both sides.
Installation of boiler equipment and its efficient operation is impossible without a chimney.
The correct choice of materials and compliance with standards when connecting is the key to your safety.
Gas services strictly control the commissioning process and may fine violators or forcibly disconnect the user from the gas supply.
Basic requirements for materials:
- fire resistance;
- anti-corrosion properties;
- resistance to the effects of acid formed as a result of the interaction of condensate with combustion products;
- long period of use.
Brick chimney. It has low draft and is prone to rapid destruction due to the formation of abundant condensation on the surface, which turns into an ice crust during the cold season. Ideal only for fireplaces or as a kind of cover for a stainless steel chimney.
Stainless steel. It has a lot of advantages, which makes it one of the first in popularity among its peers. It has good traction, fire resistance and anti-corrosion, and a long service life (especially dual-circuit models). The modular assembly method allows you to create steel chimneys of different configurations and is accessible even to a non-professional. Compatible with high-power boilers. Will serve you for 15 years.
Chimneys made of galvanized steel behave much worse during use. Galvanization is susceptible to rust.
Service life – maximum 5 years.
Ceramic chimney. Externally, it is as massive as brick. The installation option is strictly vertical only. Austrian manufacturers have developed models of ceramic chimneys with an external contour not only made of ceramics, but also of metal. They are much lighter, but when installing them you need to calculate the loads on the foundation and walls. Warranty up to 30 years.
Asbestos cement pipes. Short service life (5 years), difficult to install, not environmentally friendly. Even the low price of the material cannot serve as a compelling reason to choose such a chimney. Overheating can simply rupture the pipe. Suitable for occasional use in the countryside.
Coaxial- made of aluminum in the form of two sandwich pipes with different diameters, located one inside the other. The external one is intended for supplying air, and the internal one is for removing combustion products. The structure is prefabricated. The location is most often horizontal.
Advantages of a coaxial chimney:
- Safety
- Increased efficiency of the heating system
- Environmental friendliness
Chimney elements
Regardless of the material, the design includes the following elements:
- Tee with revision— a fitting for condensate is installed at the bottom of the tee
- Adapter for connecting the gas boiler pipe and the chimney
- Fastenings- brackets and clamps
- Cone shaped tip
- Bends— installed no further than 2 meters from the beginning, otherwise the boiler draft is reduced;
- Feedthrough
- Telescopic pipes
Size Requirements
- Smoke channel should not contain ledges and be positioned strictly vertically. With a narrowed cross-section, a significant reduction in draft occurs, and when using pipes with a large diameter, it is possible to blow into the boiler chamber, with its subsequent attenuation.
- Sectional area of the chimney pipe should not be smaller than the area of the pipe through which the chimney is connected to the boiler.
How to calculate the chimney diameter
Key parameters- cross-sectional area (outlet F cm2).
The calculation is made using the formula F = (K ∙ Q) / (4.19 ∙ √ˉ N), Where:
K- coefficient calculated empirically (0.02-0.03);
Q- performance indicator of the gas appliance (indicated in the technical characteristics of the boiler);
N- chimney height.
The resulting number is adjusted by building codes and regulations.
For example, if brick is used, then the cross-section is 0.5 x 0.5 material.
For asbestos cement, the diameter is at least 10 cm.
Diameter of round chimney with a boiler power of 24 kW it should be 120 mm, 30 kW - 130 mm, 45 kW - 170 mm, 55 kW - 190 mm, 80 kW - 220 mm and 100 kW - 230 mm.
The minimum cross-section of rectangular channels depends on the thermal power of the boiler:
- Up to 3.5 kW - 14 by 14 cm.
- 3.5 to 5.2 kW - 14 by 20 cm.
- From 5.2 to 7.3 kW - 14 by 27 cm.
Design rules for boilers with natural removal of combustion products
- The chimney pipe must be located above the ridge of the roof, is at least 0.5 meters higher than it, provided that its axis is close to the ridge or parapet (less than 1 m and no more than 1.5 m).
- If the pipe is located further from the ridge (from 1.5 m to 3 m), then its height should be level with the ridge.
- When the chimney is located at a distance of more than 3 m, its height must not exceed the boundary of a line laid down from the ridge at an angle of 10° to the horizontal.
- If you have a flat roof, the height of your chimney should also have a minimum limit of 0.5 m, and in the case of a combined roof – 2 m.
A smoke removal pipe outside the building cannot be erected without insulation: the resulting condensate will destroy the chimney.
- The system for ejecting combustion products must be fixed to the wall at intervals of no more than 2.5 meters, in areas with a slope - every 1.5 meters.
- Clamp must be used on any connecting section of an insulated chimney.
- Chimney elbow must have a slope angle of at least 15 ° and no more than 90 ° (no more than three rotary bends in the system are allowed). The vertical section following the turn must be clearly secured with fastenings. It is prohibited to load inclined sections of the pipe or its bends.
- It is necessary to equip the chimney with a condensate drain, which must be available for service.
- The chimney must be insulated from flammable materials using brickwork or asbestos board. The distance from the connecting pipe to flammable surfaces must be at least 25 cm, and if a protective layer is applied - from 10 to 5 cm.
- Stable traction can be ensured, if you build a pipe above the wind pressure zone.
- Smoke exhaust systems built inside the building do not need to be additionally insulated, but it is necessary to take care of the tightness and ventilation system. Toxic smoke can easily seep even through the brickwork of the protective casing.
- Areas located outside the structure are insulated. In the absence of thermal insulation, the gases quickly cool, the draft decreases, and the boiler power drops. Condensation forms on the walls.
Requirements for installation of coaxial chimneys
When installing the smoke duct of such boilers, it is necessary to keep in mind that:
- When the length of the coaxial pipe is no more than 1 meter, it is necessary to install a tapering diaphragm on the air duct. The power of the fan in the chimney is designed for a certain pipe length and, if it is less, there will be a loss of draft with all the ensuing consequences.
- The pipe is located in a horizontal plane, but should still have a slope of 1 cm for each meter of total length and no more than two knees.
- Pipe head can protrude outward no more than the length of its tip - to protect against freezing, and not lower than 2 meters from the surface of the earth.
What do SNiPs say?
The installation of smoke ducts for gas boilers is regulated SNiP 2.04.05-91, and DBN V.2.5-20-2001
If you comply with all requirements during installation work, you can be sure that the gas service specialists will not have any questions for you. On cold winter evenings, your family will be warm and safe.
To learn how to choose and install a chimney correctly, watch the video:
Is the complete removal of combustion products. In order for this requirement to be met, it is necessary to properly design and install the gas exhaust system. In particular, carry out a correct calculation of the chimney for a heating boiler installed in a private house.
The geometry and features of the gas exhaust system affect the traction force, which, in turn, affects the efficiency of the device, the efficiency and safety of its operation. If the draft is weak, carbon monoxide will enter the room, which poses a high risk to the health of the people in it. If there is excess draft, heat will leave the room. Therefore, accurate calculation of diameter, height, selection of building materials and taking into account a number of other parameters of the gas exhaust system is a task of paramount importance.
Types of chimneys
The durability of any system installed in a private home or business is affected by the building materials from which it is constructed. The chimney for a heating stove or boiler must withstand high temperatures, exposure to moisture and acids formed during the combustion of gas or other fuel. Weight is equally important; After installation of the system, there should be no need to strengthen the load-bearing walls or foundation.
The most popular materials for chimney installation are:
- stainless steel (lightweight, corrosion-resistant, with a service life of 15-20 years);
- galvanized steel (more than a budget option, but short-lived option due to rapid wear of the zinc coating);
- aluminum (durable material, but not particularly strong; usually used only in the interior decoration of the chimney);
- ceramics (durable and reliable, but quite heavy material with a service life of more than 30 years).
Enameled pipes are also used to install gas exhaust systems, because they are installed faster than others, since they have a built-in thermal insulation system.
Knowing the properties of the above materials, it is easy to conclude: the best of them are stainless steel or ordinary thick-walled steel, coated on the outside with a layer of stainless steel.
Calculation of a chimney for a gas boiler (or solid fuel) should be carried out at the stage when the design of the device is determined. Its main types are listed below:
- Sandwich chimneys. Structurally, they are a small pipe embedded in a large one. Insulation is laid between them. A double metal layer is the key to reliability and durability.
- Coaxial chimneys. The design is similar to a “sandwich”, but there is no insulation between the pipes - street air is supplied into the space. Most often, coaxial chimneys are used in closed-type gas boilers. Available in easy-to-assemble modules.
- Brick chimneys. The heaviest structures. The draft may be low due to the roughness of the internal walls; in addition, there is a high risk of soot accumulation and difficulty in removing gases. In addition, brick absorbs moisture well, which is why it quickly collapses.
- Asbestos-cement chimneys. Made from a mixture of asbestos and cement. Such designs are popular due to their obvious cheapness, but even with slight heating they crack and release harmful substances.
Another criterion for classifying drainage systems is the installation method. On this basis:
- external;
- internal.
The first ones are placed horizontally on the street and attached to the outer walls. They are easy to install and make it easy to comply with fire safety regulations. Disadvantages - increased insulation of pipes and the mandatory installation of a condensate collector.
Internal chimneys are vented outside through the ceilings and roof. Plus - on the second and subsequent floors, the temperature will remain above zero in winter due to the passage of a pipe heated by gases through them. For technical premises - the best option. The downside is the need to arrange passage units to ensure fire safety requirements.
It is also important to know the regulatory requirements related to the installation of a chimney. Below we list the main ones.
What to look for when choosing a chimney
The maximum temperature of combustion products passing through the exhaust systems is 150-160° C. This characteristic is relevant for most chimneys.
Most steel grades can easily withstand the temperature, but not everyone can withstand the effects of sulfuric acids formed during gas combustion. Chemical compounds corrode the walls of brick, metal, and asbestos-cement chimneys. It is recommended to give preference to products from acid-resistant brands.
The second nuance you need to know about is the formation of dew point inside the chimney. As air passes through the pipes, condensation forms on their inner surface over time. Because of this, the process of removing flue gases becomes difficult or stops.
This problem is usually observed in brick chimneys, the inner walls of which are rough. There is almost no condensation on stainless steel chimneys. Just as rarely - on ceramic and asbestos-cement. However, we remember that the latter form harmful substances during combustion, so we do not consider them further.
The optimal chimney design is a “sandwich”. The presence of insulation between the pipes equalizes the external and internal temperatures. Due to this, less condensation forms.
External and internal options for the gas boiler chimney outlet.
Types of gas boilers
The type of chimney selected, as well as its performance indicators, directly depends on the heating device. All gas boilers are divided into two large groups by design:
- With open burners. Quite bulky boilers, comparable in size to a fireplace and installed on the floor. A working device consumes oxygen from the room. For stable operation you need constant high-quality air exchange. If not enough air enters the room, carbon dioxide released during combustion leaks into the house from the boiler.
- With closed burners. Such devices are installed on compact low-power boilers (up to 40 kW). Fuel combustion occurs in a sealed chamber. A coaxial type chimney is optimal for such a boiler. The chimney is mounted in a horizontal plane.
Now it’s time to study the requirements of GOSTs and SNiPs regarding heating equipment. With them, the algorithm for calculating chimneys for solid fuel boilers, as well as for gas boilers, will become a little more understandable.
General requirements for installation of structures
The regulations for gas boilers differ depending on the type of burner. The following standards and regulations apply to chimney systems installed on open-type boilers:
- the pipe has no more than 3 bends (45-90°);
- only non-flammable material is used;
- pipes must be protected with thermal insulation;
- a hole with a damper is provided through which the chimney is cleaned;
- the height and cross-sectional parameters of the chimney comply with the requirements recommended by the boiler manufacturer;
- there is another hole in the pipe to collect condensate;
- To protect the chimney from dirt, leaves, etc., a special umbrella is provided.
Requirements for chimneys on boilers with closed air exchange:
- the diameter of the outlet pipe is less than the diameter of the pipe itself;
- the minimum distance of the horizontal chimney from the ground surface is 2 m;
- the chimney pipe is located at least 2 meters from windows, doors, ventilation holes;
- the minimum vertical distance from the pipe to the window openings is 1 m;
- there should be no walls, fences or other obstacles closer than 1.5 m near the pipe;
- When installing, you should maintain a pipe inclination angle of 6-12° for natural removal of condensate.
- it is allowed to use one outlet channel for two heating devices if the distance between them is at least 750 mm;
- pipes must be completely sealed;
- the optimal type of section is round;
- perfectly smooth inner walls (finished with galvanized or stainless steel).
It's time to move directly to the calculations themselves.
Calculation of chimneys for heating boilers
When installing chimney systems, a dozen formulas are used, which take into account:
- physical processes of fuel combustion (movement of carbon dioxide, temperature outside and inside the pipe);
- geometric characteristics of the house and boiler (ceiling height, cross-sectional shape of the outlet pipe, channel area);
- constant values (for example, the acceleration of gravity when calculating the speed of gas movement or the smoothness coefficient of pipes, depending on the material).
It is impossible to perform accurate calculations for everything on your own. It is better to turn to specialists, but some conclusions can be obtained by taking a cheaper and shorter route.
Thus, there are three methods of installing a chimney, depending on its distance from the roof ridge:
- The chimney is more than 3 m away from the ridge. In this case, its highest point can be set below the level of the ridge at an angle not exceeding 10°. An urgent requirement if you want to save on chimney elements.
- The chimney is 1.5-3 m away from the ridge. The height of the channel is equal to the height of the house, i.e. the ridge and the top point of the smoke exhaust system are located on the same level.
- Between the chimney and the ridge - less than 1.5 m. The highest point of the pipe is located at least 50 cm above the ridge.
We have decided on the length of the chimney; all that remains is to calculate the sufficient cross-section for the pipe. This is done most accurately using the formula F=(AxB)/4.19xC, where:
- F- cross-section (sq. m);
- A- tabular coefficient from 0.02 to 0.03;
- IN- boiler power (kW);
- WITH- chimney height (m).
The resulting value is compared with the table according to SNiP 2.04.05-91 and, if necessary, adjusted upward.
If we take the average characteristics from the mentioned document, we get a recommended round section with a diameter of 200 mm for a pipe 7 m high, removing gas from a 16 kW boiler, or a diameter of 150 mm for a 32 kW boiler and a 20 m long outlet.
You can calculate the chimney for a gas boiler online on the Teplodar company website. If the design of the drainage system and an approximate scheme for its implementation are known, the calculations will take less than a minute.
Our specialists are always ready to make the necessary calculations, give recommendations on the selection of chimney elements and announce their exact cost.
Please note that the health of the people living in the house depends on the correctness of the calculation. And in order to increase fire safety, it is recommended to slightly overestimate the obtained values. Remember that reducing the design diameter may result in a ban on operation. You'll have to dismantle the chimney, redo everything and pay double.
The design and installation of a smoke exhaust system can be delegated to professionals, but you will have to think about caring for it. Do not overheat gas and solid fuel boilers, do not use them at maximum power and clean them at least once a year. Then the selected chimney will last for decades.
Correct operation of gas heating equipment largely depends on the system that removes combustion products. Before installing a chimney for a gas boiler in a private house, you need to have an idea of the types of equipment, the principles of its operation and the regulatory documents according to which it is installed. Regardless of who will carry out the work, the choice of device and installation should be taken with full responsibility.
Installing a combustion product recovery system on a gas boiler contributes to the efficient functioning of the equipment and the entire heating system, safe and comfortable heating, as well as trouble-free operation of the boiler. Before buying a chimney for a gas boiler, it would be a good idea to get specialist advice about the existing options for chimneys and the feasibility of their use.
Types of smoke ducts for gas boilers:
- brick chimney - its construction is planned at the stage of building a house and a foundation is laid under it. A prerequisite is the smooth surface of the internal walls of the chimney. It should be noted that the structure must be resistant to acid, which is formed due to steam condensation. Otherwise, rapid destruction of the brick chimney pipe will occur. Used in combination with ceramic or steel liners. Brick chimneys for gas boilers are distinguished by their complex design, construction time and cost. In terms of technical indicators, they are in many ways inferior to the modern chimney systems that have emerged;
- stainless steel pipe design - this version of the chimney is highly resistant to chemical environments and mechanical damage. The system is made in the form of a sandwich structure: when a pipe with a smaller diameter is inserted into the outer pipe. Fire-resistant material - basalt wool - is placed in the free space between them. Manufacturers offer a wide selection of chimney models;
- coaxial chimney - the design is assembled according to the “pipe-in-pipe” principle: combustion air is taken in through one pipe, and combustion products are discharged through the other. Such a system has high technical characteristics that help improve the safety of all gas equipment and increase its efficiency. And due to the fact that the combustion cycle occurs outdoors, a boiler with a coaxial chimney is environmentally friendly equipment;
- chimney made of ceramic pipes - consists of ceramic blocks with thermal insulation, installed in a concrete frame. Such a smoke exhaust system is resistant to temperature fluctuations, waterproof, fireproof and has high mechanical strength. The main requirement for installation is high-quality joining of ceramic modules.
Which chimney pipe is best to use - everyone decides based on their specific situation. The main thing is to highlight the strengths and weaknesses of any option. Regardless of what type of chimney you choose, its design and installation must comply with SNiP 2.04.05-91 “Heating, ventilation and air conditioning.” After studying these standards, you can learn how to properly install a chimney on a gas boiler.
Chimney for a gas boiler in a private house: basic requirements of SNiP 2.04.05-91
Measures for installing a chimney for a gas boiler, from the design stage to the actual installation of the system, must comply with the requirements of the current regulatory framework, since improper installation and operation of gas equipment calls into question the safety of people using gas installations.
Main elements of the chimney design:
- flue - a channel leaving the boiler into the chimney pipe, connected by an adapter;
- chimney pipes;
- revision - attached to the bottom of the smoke exhaust shaft and serves to clean the channel from combustion products and remove excess moisture;
- fastening elements (brackets, clamps) - used for fastening to the wall;
- other components for the system device.
As a rule, the location of a gas boiler in a private house is planned on the ground floor in a separate room (boiler room). All elements of the heating system must be connected to each other strictly tightly. The basic rules for installing chimneys for gas boilers, regulating the technological order, are presented in regulations SNiP 2.04.05-91 and contain the following requirements:
- proper draft - ensures complete removal of exhaust gases;
- resistance to high temperatures;
- tightness of connecting points - all components along the entire length of the chimney exhaust system must fit tightly to each other;
- the pipe where it passes through the ceiling must be solid, without joints;
- condensate collector - the design of this element must ensure the collection and removal of liquid;
- if the structure has turns, inspection hatches are installed in these places to diagnose the condition of the chimney, clean it and drain condensate;
- the length of the pipe branch to the side should not exceed 1 m;
- the permissible number of turns on chimney pipes is possible - no more than 3;
- the height of the chimney pipe must exceed the height of the roof (at the highest point) to ensure good draft and prevent reverse draft;
- the distance between the chimney pipes and the surface, which is made of non-combustible materials, can be at least 5 cm, and if the surface material is flammable - at least 25 cm.
Helpful advice! Complete sealing of the chimney sections will not allow hot combustion products to escape the system.
The procedure for installing a chimney for a gas boiler in a private house
Depending on the stage at which it is planned to install a chimney for a gas boiler, the exhaust system can be internal or external (remote). In cottages under construction, where the use of gas boilers is envisaged, internal chimneys are used, the placement of which is taken into account in the design. In old houses, when switching to heating using a gas boiler, the chimney is vented outside.
You can compare the strengths and weaknesses of external and external chimneys by reading the table:
| Chimney type | |
| Remote | Interior |
| Full thermal insulation of the chimney is required | Thermal insulation is only necessary in the area that faces the outside |
| Safe operation is guaranteed if the standards are followed | The possibility of combustion products entering the room cannot be ruled out; there is a high fire hazard |
| The chimney device is made of the same type of elements and is characterized by ease of execution | It is characterized by complex installation, since there is a need for a large number of components and components of the chimney |
| Availability of any kind of repair work and maintenance | Difficulty in maintaining and repairing the chimney |
The installation of a chimney for an internal type gas boiler involves the construction of a foundation and a protective channel made of brick. Then safe operation will be ensured. Such systems are more efficient and the formation of condensate in them is minimal. In some cases, chimneys can be attached to the wall of the house behind which the boiler is installed.
The installation of an external chimney requires high-quality fastening and mandatory maximum insulation, since condensate in such structures is formed in larger quantities.
The main stages of installing a chimney for an internal gas boiler:
- marking places for making holes in the ceiling and roof of the house;
- arrangement of an opening for the chimney;
- connection of the boiler pipe with the gas duct;
- installation of revision, tee;
- extension of the chimney pipe;
- strengthening joints with clamps;
- fastening the structure with brackets;
- thermal insulation of the outer part.
Helpful advice! The location of the smoke exhaust system must be strictly vertical, without narrowing or widening the channel.
Chimneys for gas boilers made of stainless steel
Chimneys made of steel can have a single-walled or double-walled design. Single-layer exhaust pipes can be installed in heated rooms and used for lining brick chimneys. In three-layer systems, there is a heat-insulating layer between the two pipes, which makes it possible to use them for both internal and external installation.
Due to the fact that gas fuel contains sulfur impurities, when exhaust products are removed, its vapors have an aggressive effect, corroding the walls of the smoke exhaust channels. Therefore, in the production of stainless steel chimneys for gas boilers, heat-resistant and acid-resistant material AISI 316L is used. Its use greatly increases the service life of smoke exhaust systems.
One of the weak points of a stainless chimney pipe for a gas boiler is its not entirely aesthetic appearance. The benefits include:
- resistance to corrosion and aggressive chemical composition;
- light weight, no need for a foundation;
- non-flammability of the material - stainless steel does not melt even at a temperature of 500 ºС;
- modular design - factory production of a large number of tees, adapters and elbows allows you to integrate a chimney into any home;
- factory production of all elements of the steel chimney allows it to be assembled and removed at any convenient angle;
- absolutely smooth round inner surface - provides a minimum of obstacles to the exit of combustion products;
- possibility of installation in an already built house;
- Quite affordable price of a chimney for a gas boiler.
When installing an external chimney made of steel, there is a high probability of dew point formation: if the temperature outside is low, the exhaust vapors form condensation and a water plug is created. It clogs the channel, preventing products from escaping, and thereby blocks the combustion process. This can be avoided by placing the pipe in a brick-lined chimney duct. This technique will also solve the aesthetic side of the structure.
Another option to avoid the formation of a water plug is to use a sandwich structure of two pipes, one of which is protected by a layer of basalt wool. Such a remote chimney system no longer requires additional insulation. The diameter of the chimney for a gas boiler is selected so that it coincides with the cross-section of the equipment outlet.
Helpful advice! Stainless steel chimneys are easy to maintain, but it is necessary to have the system inspected by a specialist once every 3 years.
Rules for installing a chimney for a geyser
The key to safe operation of a gas water heater is a proper exhaust system. For the column, chimneys are used, which discharge combustion products into the smoke exhaust channel or directly into the atmosphere. The following types of pipes are used to remove exhaust gases:
- - easy to install, the flexibility of the material allows
stretch it up to 2-3 m in length, and also lengthen it by connecting several sections of corrugation; - aluminum pipe - easy to install, resistant to condensation, requires additional thermal insulation;
- coaxial chimneys - the price of such systems can be reduced due to the possibility of leading the pipe through the wall. This reduces material consumption and installation costs. The main advantage of such a chimney is that air from the room is not involved in the operation of all equipment.
Basic requirements for the installation of chimney pipes for geysers:
- operation of the devices is prohibited without a chimney securely fixed in it;
- the draft inside the chimney system must be constant;
- the pipe material must be non-flammable, resistant to corrosion, condensation and high temperatures;
- the outer section of the chimney must be vertical;
- the structure must be sealed to prevent carbon monoxide from entering the room;
- the exhaust pipe should be installed in an open place for quick troubleshooting if necessary;
- the chimney must be located at least 0.5 m above the roof level;
- It is strictly forbidden to use ventilation systems, the space between floors, or attics to remove combustion products.
How to check the draft in the chimney of a gas boiler
Draft is one of the main indicators of the proper functioning of the chimney. Its effectiveness depends on the following parameters:
- cross-section of the chimney pipe - heated gases are removed faster with a smaller cross-section, but if it is too small, there is a risk of combustion products entering the room. If the cross-section of the chimney is unreasonably large, a reverse draft effect may be created;
- accumulation of a large amount of soot on the walls of the barrel - due to this, the working cross-section is reduced, which leads to a decrease in the rate of carbon monoxide removal;
- a large number of turns in the system - any of the turns of the pipe inhibits the movement of exhaust gases;
- insufficient tightness of the chimney - the presence of small cracks and gaps allows cold air to penetrate into the system, which prevents the rapid removal of smoke;
- weather - high humidity and low atmospheric pressure can cause a decrease in traction.
You can check the state of traction using several methods. If diagnostics are carried out by professionals, they use an anemometer - a device for measuring the speed of gas movement. In everyday life they use the so-called folk methods:
- visual inspection - if there is smoke in the room, it means there is backdraft;
- using a thin sheet of paper - it is brought to the viewing window: the stronger the paper is attracted, the better the traction;
- candle flame - a lit candle is brought to the channel and the flame is blown out. The direction of smoke from an extinguished candle towards the chimney indicates good draft.
Important! The draft in gas boilers should be checked with the equipment turned off.
Depending on the reason why weak craving is observed, measures are taken to improve it. The channel is cleared of soot using a special device consisting of a brush, a sinker and a rope. The device is lowered into the canal and, with progressive movements, it is cleaned along its entire length. To achieve complete sealing of a brick chimney, it is necessary to eliminate all cracks formed as a result of the destruction of the masonry.
Coaxial chimney for a gas boiler: installation rules, advantages, installation
The main advantage of installing a coaxial chimney for a gas boiler is that such a chimney not only removes exhaust gases outside, but also provides the combustion chamber with air from the street. Thanks to this, the room does not require additional ventilation, and the air in the house remains capable of maintaining the health and performance of the people there. Equipment with such removal of combustion products is called a gas boiler without a chimney.
Design of a coaxial chimney
The design of a coaxial chimney is based on two pipes of different diameters, one of which is located inside the other. The inner pipe is designed to remove waste substances outside. Through the outer pipe, or rather, through the space between the inner and outer pipes, air is taken in from the outside, which is used for gas combustion. Thus, the chimney copes with several functions at once:
- increasing the degree of safety of the chimney - the incoming air from the street heats up, and the exiting combustion products cool down;
- increasing boiler performance - the efficiency of the equipment increases due to the fact that the air enters the combustion chamber already heated;
- maximum gas combustion - due to the fact that the boiler efficiency increases, complete combustion of fuel is achieved;
- environmental friendliness of the heating system - the entire operating cycle of gas equipment takes place outside, which ensures comfortable and safe heating.
To make a chimney, round pipes are used: the outer pipe with a diameter of 100 mm is made of steel 1-2 mm thick, the inner one is made of aluminum alloy. The diameter of the latter is 60 mm. Pipes with this ratio of diameters are used in coaxial chimneys for wall-mounted gas boilers and floor-standing devices with a closed combustion chamber. To avoid pipes coming into contact with each other, jumpers are installed along their entire length.
According to the installation method, coaxial type chimneys can be horizontal or vertical. The horizontal option is more popular due to its simple installation. In cases where it is technically impossible to install the system horizontally or the distance from the boiler to the outer wall exceeds 4 m, they resort to installing a vertical coaxial chimney. It is worth noting that its installation is more complicated.
Advantages of coaxial chimney systems
Coaxial chimneys are used for various gas equipment in which the combustion chamber has a closed structure. These are floor- and wall-mounted gas boilers, gas flow-through heaters (columns), convectors and other devices.
It is worth noting the main advantages of using coaxial chimneys over other types of gas exhaust systems:
- natural heat exchange - heating of the incoming air and cooling of the exhaust gases occurs due to the design of the pipe, which, in turn, prevents the wall from getting too hot;
- increasing the productivity of the gas equipment itself;
- compactness - the chimney is carefully installed and does not take up much space, which allows it to be used not only in private cottages, but also in high-rise apartments;
- operational safety - there is no lack of oxygen in the air of the room where the boiler is installed, since contact of the air from the room with the substances being eliminated is completely eliminated;
- ease of installation - allows you to reduce the cost of installing a coaxial chimney.
Helpful advice! If you purchased a wall-mounted gas boiler for autonomous heating of an apartment, using a coaxial chimney for it is the safest, since combustion products are not removed into the ventilation duct, but directly into the atmosphere.
Requirements for installing a coaxial chimney
As with any gas equipment, the installation of coaxial chimneys is subject to specific requirements SNiP 2.04.05–91, section 3 “Heating”; 2.04.08–87, as well as regulations regulated by the “Safety Rules in the Gas Industry”. They can be different depending on the installation method of the coaxial chimney: horizontal or vertical.
For any type of installation, there is a general requirement for the maximum length of a coaxial chimney for a gas boiler: it cannot exceed 4 m. When it is necessary to install a chimney system over a considerable distance, special coaxial models with dimensional standards are used.
When passing a vertical coaxial chimney for a gas boiler through the ceiling and roof, an adapter is used, the design of which is provided by the manufacturer specifically for this system. This also applies to coaxial chimney extensions when it is necessary to install a system of the required length. Tightness in places where pipes pass through the ceiling is ensured by a special head - a terminal. It also prevents precipitation from entering the system.
The horizontal method of installing a coaxial chimney is used, as a rule, for wall-mounted gas equipment. To avoid condensation, it is necessary to maintain a downward slope of the chimney from the boiler of 3 to 5%. There are standards for the location of smoke ducts for a chimney in the outer wall. So, if the hole is supposed to be in the wall next to the window, the distance to the window should not be less than 0.5 m, if above the window - not less than 0.25 m.
Many manufacturers of gas equipment also include a pipe for removing combustion products. If you bought a coaxial chimney for a gas boiler along with the equipment, you need to check that the kit includes a horizontal part of the pipe (usually about 1 m long), an outlet, a terminal (head), a set of sealing gaskets, and a membrane. If, when installing a pipe through a wall, it is necessary to bypass any protrusions or fittings, use elbows and bends.
Helpful advice! It is necessary to provide protection for all outputs and inputs on the coaxial chimney from foreign objects.
Coaxial chimney for a gas boiler in a private house: how to make it yourself
Before installing a coaxial chimney with your own hands, you must read the instructions for the design and operation of the purchased gas equipment. Due to the specific design of the coaxial pipe, the installation of a chimney for a wall-mounted gas boiler must be done with extreme caution. Avoid dents or other damage to the pipes that could lead to depressurization of the system.
To perform installation work, you will need the following system elements:
- pipe with flange;
- crimp clamps;
- coaxial elbow;
- adapter for connecting to the boiler;
- extension cord with sealing cuffs (if required);
- decorative overlays.
According to the requirements for chimney installation, a hole of the required diameter is made in the outer wall. If there is a window opening in the wall, it is necessary to place the hole at a distance no closer than 0.5 m from the window. When connecting a chimney to a gas boiler, first connect the adapter, and then all the links assembled into a single structure.
The pipe is led out through a hole in the wall, maintaining a slope from the boiler. If you need to connect the chimney to the wall, the structure is fixed with clamps. The gaps between the wall hole and the inserted pipe are filled with foam or sealed with mineral wool. After this, these places are covered with decorative rings.
Do-it-yourself brick chimney installation
The brick chimney design is an exclusively vertical channel with a square or rectangular cross-section. To lay a brick chimney, solid ceramic bricks are used, which are laid on mortar. The outer section of the channel is laid out with ordinary brick, corresponding in style to house construction, which can be seen in numerous photos of brick chimneys. If the house is lined with stone or plastered, you can decorate the chimney in the same way.
Brick chimneys for gas boilers: installation requirements
Before laying a brick chimney for a boiler, it is necessary to build a foundation, the height of which must be at least 0.3 m. The dimensions of the base around the perimeter must protrude beyond the contour of the channel itself by at least 0.15 m. If the chimney is located in part of the external wall, its foundation should be level with its base. Laying a brick chimney with your own hands (video instructions confirm this) begins at the stage of building the walls of the house.
Requirements for brick chimneys:
- the smoke channel must be vertical, without ledges, narrowed or widened areas;
- the thickness of the brick pipe for the chimney is taken taking into account the exclusion of freezing;
- the minimum permissible cross-section of smoke exhaust ducts is 14 x 14 cm, which corresponds to the size of half a brick, taking into account the seam;
- the size of a brick chimney, the height of which is less than 5 m, should be increased to a channel cross-section of 14 x 20 cm;
- the chimney is constructed in the walls between heated rooms, which will prevent it from cooling and reducing draft;
- tightness - the brick chimney is laid with ligation so that the vertical seam of the previous row overlaps with the brick of the next one;
- the inner surface of the channel must be smooth;
Helpful advice! To achieve a flat and smooth inner surface of the channel, use special templates when building a brick chimney with your own hands.
- the distance between adjacent smoke exhaust ducts should not be less than 5 average outer diameters of the pipe;
- if ventilation ducts are located near the chimney, their height should be equal to the height of the chimneys.
To reduce construction costs, you should place as many channels as possible in a common chimney. In this case, adjacent chimney and ventilation ducts will heat each other, which will generally improve the functioning of the chimney.
Preparation of mortar for laying a brick chimney
The composition of the mortar for laying a brick chimney is selected taking into account which section of the pipe is being laid: external or internal. To construct the external channel, the same mortar is used as for laying load-bearing walls of house construction. It is prepared from cement, sand, water and can harden in air and water. The mixture is prepared in such a volume that it can be used within an hour, as it sets quickly.
To ensure that the mixture does not deteriorate under the influence of an aggressive environment, it is recommended to add special additives to it that increase its plasticity, strength and acid resistance. Thanks to these additives, you can improve the quality of the masonry itself, increase the speed of construction and the durability of the work performed.
The preparation of a solution for a brick chimney running inside a house is based on the use of fireclay and fireclay in its composition in a 1: 1 ratio. Such mixtures cope well with high temperatures, they are durable and do not emit harmful substances. To give the clay mixture strength, you can add table salt to its composition (about 120-150 g per bucket).
Helpful advice! The strength of the chimney mortar can be enhanced by adding Portland cement in a proportion of 1 kg per bucket.
When laying a brick chimney with your own hands, you can purchase ready-made mixtures that are heat-resistant and acid-resistant. Preparing the solution yourself can reduce the cost of building a chimney.
It is quite possible to build a brick chimney with your own hands - the video below will help you familiarize yourself in detail with the stages of constructing the structure, taking into account all the basic requirements.
The feasibility of using a brick chimney for a gas boiler
Taking into account the advantages and disadvantages of brick chimneys, it is possible to draw conclusions regarding their use in combination with gas boilers. Their advantages include:
- the likelihood of using an existing chimney duct, which reduces chimney costs;
- possibility of operation in conjunction with gas equipment with an open combustion chamber;
- reasonable cost of materials for construction and finishing of the structure.
The durability of brick channels is observed only when they are used for fireplaces or stoves. If they are used for gas boilers, due to the low temperature of the combustion products, condensation will form on the channel walls, and harsh operating conditions in an aggressive environment will lead to the gradual destruction of the brickwork and deterioration in performance.
In addition, the requirements for such chimneys are more stringent:
- impeccable masonry - if the skills are not enough, it will be necessary to invite a qualified mason to work, which will cost a lot of money. Prices for work: rough brick masonry from 6,000 rubles per 1 m³, facing masonry - 2,500 rubles. for 1 m²;
- inability to perform a complex channel configuration (if you need to bypass, for example, a beam in a ceiling);
- the use of the old channel should be carried out using sleeves;
- the need for thermal insulation.
The disadvantages of such a system include a decrease in traction while the brick is warming up. Thus, the correct chimney for a gas boiler will be a brick channel together with a steel or ceramic liner. The photo of brick chimneys shows that liners are installed during the process of laying the channel. In this case, it is necessary to leave a gap between the liner pipe and the brick surface. This is necessary so that the pipe can move inside the channel.
Chimneys for gas boilers: prices for different types of pipes
When planning your budget when purchasing chimney pipes, you should take into account the length and diameter of the channel, the presence and number of turns, as well as the material from which the pipes are made. There are no fundamental differences in the design and cost of chimneys for floor-standing gas boilers and wall-mounted appliances. A stainless steel chimney will cost more than a brick chimney, but a steel pipe is easier to install, which makes its installation costs quite affordable.
You can buy a chimney for a gas boiler at specialized sales points and in online stores that sell these products. A large assortment of fittings, shaped parts, tees, adapters, plugs and other necessary structural parts is also offered for sale. Given the convenient sorting of products by category and model, you can quickly find and order the product you need.
The cost of 1 m of a single-circuit stainless steel pipe with diameters of 100, 110, 115, 120 mm is 650 rubles, the same pipe with a diameter of 140-150 mm will cost 750 rubles. The price of an elbow with a rotation angle of 90° made of stainless steel for a pipe with a diameter of 110-120 mm is 550 rubles. with a metal thickness of 0.6 mm. You can purchase 1 m of stainless steel sandwich pipe with a diameter of 140-230 mm for 1,900 rubles.
Helpful advice! You can save on purchasing high-quality and durable chimney pipes if you place an order during the discount period.
The price of a coaxial chimney for a gas boiler with a diameter of 60-100 mm and a length of 1 m, sold in a horizontal set, is 3,500 rubles. The purchase of a coaxial chimney from Baxi, a global manufacturer of modern heating systems, will cost 4,200 rubles. A complete chimney kit for a wall-mounted gas boiler includes a 75 cm long pipe with a diameter of 60-100 mm, a 90° bend and a tip. All products are guaranteed.
Proper installation of any household appliance is the key to its safe and long-term operation. Especially when it comes to gas equipment. Installation of a combustion product removal system for gas boilers requires preliminary engineering calculations and qualified implementation.
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D To remove combustion products inside the furnaces of heating devices, chimneys for a gas boiler in a private house of different designs from different materials are used. The standards SP 7.13130 specify the requirements for cross-sections, heights, location of chimneys, safe diagrams of passage units through structures made of flammable materials.
Chimney from a gas boiler on the facade of the house
Requirements for chimneys and installation rules
Combustion products have high temperatures, so chimneys must fully comply with the standards of SP 7.13130. The use of factory products that have not passed the Russian Federation certification is not allowed.
The main provisions of the set of fire safety rules are:
- internal cross-section of the chimney - 14 x 14 cm - 14 x 27 cm depending on the thermal power of the boiler (3.5 - 7 kW, respectively) for concrete, brick, ceramic structures, the area of round or asbestos-cement pipes must correspond to these dimensions;
- height – 5 m minimum from the firebox to the deflector;
- chimney thickness - 6 cm for heat-resistant concrete, 12 cm for ceramic brick, not standardized for asbestos cement, sandwich.
The height of the deflector (an umbrella structure that protects the pipe from rain and wind) relative to the ridge depends on the distance of the chimney from it:
- 0.5 m higher at a distance within 1.5 m;
- level with the ridge at a distance of 1.5 - 3 m;
- at the level of an imaginary line at an angle of 10 degrees relative to the horizontal, drawn from the ridge to the pipe, at a distance of more than 3 m from it.
When moving the chimney outside, elbows are allowed within 1 m from the axis of the main pipe to the side at an angle of less than 30 degrees relative to the vertical. The cuts should exceed the thickness of the floors with decorative ceiling cladding by 7 cm with an even distribution of this size from below/top.
The distances from the outer surfaces of structures to wooden elements of load-bearing structures (sheathing, rafters, beams, crossbars) must be greater than the specified dimensions, depending on the chimney material:
Attention! It is prohibited to combine chimneys with ventilation ducts without a special design. But you can run combustion products from two boilers into one pipe if necessary.
Chimney structures
When choosing a chimney or channel, you should focus on the best combination of construction budget, resource, and maintainability. Depending on the materials used, chimneys for a gas boiler in a private house are attached with clamps to the enclosing structures or rest on separate foundations.
Attention! Gas boilers have gases with low temperatures at the exit from the combustion chamber. Therefore, the “condensate” technology is used.
The chimney assembly technology looks like this:
- installing a damper on the boiler outlet pipe to adjust the cross-section of the chimney channel;
- installation of pipes until they are blocked by condensate;
- making a cutting from a steel box attached to the floor from below;
- cutting through the chimney, building up to the roof;
- fastening to the canopy sheathing - a plate with a conical pipe located at the desired angle to it, depending on the slope of the slopes;
- fixing the sandwich chimney pipe to the roof with a okapnik (a conical clamp of a complex profile), which decorates and seals the joint.
After that, it remains to install one of the elements at the mouth of the pipe:
- volper - deflector for increasing traction with a flat cover;
- weather vane - deflector to improve draft of the original design;
- fungus – conical nozzle for protection from precipitation.
These elements are made of stainless steel and fully correspond to the style of sandwich chimneys.
Stone and brickwork
Chimneys for a private house can be built into brickwork (only into a load-bearing internal wall) or made from blocks. Domestic manufacturers produce several types of chimney modules:
- concrete - used only in conjunction with ceramic pipes running inside them, the outer surface is square, the inner is round;
- ceramics - pressed into special molds, then fired in kilns, have the design of an internal pipe, an external square thin-walled box, connected by stiffening ribs.
The Ukrainian company Schiedel produces chimney blocks made of volcanic pumice. The modules are called Isokern and are a budget option for individual developers. The material is much lighter than concrete and ceramics, the only drawback is the rough inner surface and the lack of Russian certificates. Regional fire safety services accept structures made from this material in 50% of cases.
Brick chimneys are built into walls during the construction of enclosing structures. To lay the blocks, it is necessary to concrete a separate foundation. But, the pipes can be placed in any convenient place, there are no problems with the passage units, rafter systems, or floors.
Asbestos cement pipe
Aggressive advertising by manufacturers of sandwich chimneys cites the main disadvantage of asbestos - the lack of environmental safety. In fact, only safe raw materials and technologies are used in domestic production. According to reviews from craftsmen who install all types of modern chimneys, an asbestos-cement pipe has the following advantages:
- is self-supporting - no need to attach to walls;
- does not condense moisture - there are no leaks into the combustion chamber;
- resistant to combustion products - the resource is higher than that of concrete and brick;
- cheaper than ceramics - the cost is much lower.
Installation of an asbestos cement pipe is extremely simple:
- the first pipe is installed on the foundation, secured with racks or a frame;
- the chimney is increased to the required height, the pipes are connected with couplings;
- The top is covered with a deflector, and a hatch is made at the bottom to install the cleaning door.
The connection from the boiler is made with a steel elbow, which can be replaced if necessary.
Installation of coaxial structure
Unlike other chimney modifications, a coaxial pipe can only be used for closed combustion chambers. (supercharging) is a mandatory operating condition of the system. The design of a coaxial chimney is similar to a sandwich, but instead of insulation, there are jumpers between pipes of different diameters. The inner pipe is used to remove combustion products; the street air necessary for burning natural gas is sucked into the interpipe space.
Unlike conventional chimneys, the pipe does not need to be pulled vertically across all floors. Instead, a 90-degree outlet is put on the outlet pipe, a coaxial chimney is attached to it horizontally, and goes out through the nearest wall while maintaining fire safety distances:
- maximum length of horizontal part 3 m;
- minimum 0.2 m to the ceiling, floor, ground;
- more than 30 cm from the axis of the chimney to the wall surface;
- at least 60 cm from the mouth of the pipe to the opposite wall.
The coaxial structure can be installed vertically above the roof, horizontally through the wall, or connected to a smoke duct built into the brickwork of the wall.
conclusions
Thus, for closed combustion chambers, a coaxial chimney is preferable, saving the construction budget and the aesthetics of the roof, in which there will be no holes. The most reliable for open fireboxes are asbestos-cement pipes or sandwiches. The most discreet wiring is ensured by built-in smoke channels in brickwork, structures made of concrete, ceramic blocks or Isokern modules made of volcanic pumice.
