Why is the boiler crying? What materials are best to work with in order to reduce condensate on the gas boiler pipe, is it possible to calculate the risk of its occurrence Dew point in the boiler chimney

Condensate seeping from the chimney can have a devastating effect on the structure of the furnace pipe. Therefore, in order to avoid such situations, even at the time of building the house, you should carefully understand the types of chimney structures, choose the most suitable model and, in addition, use a chimney steam trap.

What is condensate

Condensate is a tarry liquid that, due to regular exposure to cold temperatures, turns into condensate that settles on the inner walls of the pipe.

When flue gases pass through the channel, they gradually lose their original temperature, due to which the water vapor in them remains on the walls, turning into a liquid. When it is mixed with the products of fuel combustion, acids (for example, sulfuric, hydrochloric, nitric and others) begin to form.

Modern gas heating boilers are characterized by a low temperature of the exhaust gases and periodic shutdowns. During this, the walls of the chimney are cooled from top to bottom. When gases are cooled to a temperature of 45-60 degrees, condensate begins to form. In a smooth stainless steel pipe, the liquid flows down, and in pipes with a rough inner surface (for example, made of brick), the liquid penetrates the walls. As a result, the chimney is gradually destroyed.

In most cases, condensation forms due to:

• draft;
• a sharp temperature drop;
• poorly blocked outlet;
• low temperature of escaping vapors;
• unheated pipes;
• wet or raw fuel;
• not completely burned fuel;
• clogging of pipes;
• various violations in the design of the device;
• high difference between internal and external temperatures;
• traction problems.

Normal thrust is provided, first of all, due to dry fuel. This will ensure that the device warms up thoroughly and quickly, minimizing the risk of any deposits. In addition, you should be very careful in choosing the firewood themselves. For example, too resinous, regardless of the quality of drying, will cause resinous deposits. For this reason, for home heating, it is best to choose firewood that is well dried and does not contain a large amount of resins.

Unfortunately, it is impossible to completely eliminate condensate in the pipes of gas boilers, only to reduce its amount. To achieve this, it is necessary to choose the correct design and material of the chimney. It is advisable to carefully insulate the upper part of the chimney, which will reduce its cooling time.

Requirements for the design of the chimney

The chimney must be vertical, tight and without ledges. If, nevertheless, there is a slope of the chimney, then it should be no more than 30 degrees, while the horizontal distance should not exceed one meter. In addition, the cross section of the channel must be the same throughout its length. Thanks to the observance of all these requirements, traction will be much better, and the amount of condensate will be noticeably reduced.

Types of chimneys

When building a house, you should decide in advance which chimney design is most suitable for the selected type of furnace, because if in the future the old chimney has to be replaced with a new one, serious repair work may be required.

Brick chimney

It is characterized by excellent traction, high quality of heat accumulation, and the ability to retain heat for a long time. But at the same time, brick, when used as the main material for chimneys, is considered one of the worst, since condensate can form in such chimneys due to low temperature, prolonged heating of the pipe, certain climatic conditions (for example, periodic freezing and thawing of the pipe in winter). The process of brick destruction will occur very quickly, since this material absorbs moisture very well. The walls will get wet, the interior finish will become unusable, and the pipe head may simply crumble. Here it is recommended to use a sleeve, in which a special stainless steel channel is built into the inside of the chimney.

Asbestos-cement chimneys

In recent times, asbestos-cement chimneys have been used almost everywhere, even in the construction of fireplaces and sauna stoves. These types of chimneys are very cheap, but they have a lot of disadvantages.

The disadvantages of asbestos-cement chimneys include:

• poor tightness of joints;
• the possibility of installing pipes only on vertical sections of the chimney;
• high level of condensate absorption by the walls of the chimney;
• difficulties during installation work due to the large length and weight of the chimney structure;
• lack of resistance to high temperatures, due to which asbestos-cement pipes can burst and explode;
• the complexity of connecting the boiler, since the connection requires a tee, a condensate trap and a cleaning hatch.

As a result of exposure to condensate, they can rust in the shortest possible time. On average, the service life of steel pipes reaches 3 years, and galvanized pipes - no longer than 4.

In the manufacture of plastic, reinforced with high-strength fibers. Due to this, pipes made of such material have a high level of resistance to condensates, low thermal conductivity, and are excellent for use at temperatures not exceeding 200 degrees.

They are made both in single-walled and insulated (basalt fiber) version. To combat the formation of condensate, steel itself is used, which can be significantly strengthened due to the combination with a heater.

Steel chimneys have many advantages:

• tightness;
• high level of fire safety (if all operating rules are observed);
• ease of use;
• good traction, which is ensured by the round section and smooth surface.

Elimination of condensate

Timely removal of condensate is an occupation that every owner of a stove, fireplace, etc. has to deal with. The main solution to this problem is the use of a condensate drain, supplemented by a special waste collector. In this case, all work is reduced only to removing condensate from the collector and cleaning the chimney.

Other ways to eliminate condensation include:

• Use of carefully dried high quality fuel.
• Elimination of air leakage by closing the hole or completely sealing it.
• Insulation of the pipe, which will minimize the settling of moisture on the walls.
• Achieving a temperature at which the temperature of the outgoing gases will be at least 100 degrees. This requires the installation of a special channel.

Attention ! Naturally, it is worth remembering such a procedure as timely cleaning of pipes. This ensures that the chimney is constantly clean and, at the same time, its long operation. You can clean the pipes yourself or with the help of a master who will additionally assess their condition.

You should also check the entire structure of the furnace and, if there are any defects, eliminate them. It is worth noting that special attention should be paid to various additional devices that can have a positive effect on one function, but at the same time negatively on another.

Perhaps the most favorable solution for eliminating condensate in the chimney is to equip the structure with an acid-resistant stainless steel channel, supplemented by a collector and a drain. Installation works are characterized by ease, simplicity and fast terms.

During the operation of the heating system, the appearance of moisture in the chimney harms not only the chimney itself, but also the heater. Reacting with combustion products, moisture turns into chemically aggressive substances that disrupt the operation of the heating system.

It is impossible to get rid of condensate completely, but you can minimize its amount and prevent undesirable consequences.

Any fuel for a boiler, stove or fireplace, when burned, releases water vapor, which cools down in the chimney pipe and forms a deposit in the form of drops on the walls. This happens due to the temperature difference at the outlet of the heating unit and in certain parts of the chimney.

Additionally, moisture can enter the smoke channel from the outside during rain. The chemical reaction of water with soot and resins leads to the formation of acids and alkalis.

On smooth walls, condensate flows down, where it accumulates, preventing smoke from being removed and worsening traction. Rough surfaces trap and absorb moisture, subject to corrosion and premature failure.

In addition, substances accumulated in the chimney can enter the room, causing an unpleasant odor and causing harm to health.

Note! Condensation can form not only from the inside, but also from the outside of the chimney - at very different temperatures in the pipe and on the street. The result may be the destruction of the pipe itself, if it is made of moisture-absorbing materials, as well as walls and roofs in contact with the chimney.

Factors affecting the formation of condensate

The process of formation of condensate in the chimney channel depends on several factors:

• Humidity of the fuel used by the heating system. Even seemingly dry firewood contains moisture, which turns into steam when burned. Peat, coal and other combustible materials have a certain percentage of moisture content. Natural gas, burning in a gas boiler, also releases a large amount of water vapor. There is no absolutely dry fuel, but poorly dried or damp material increases the condensation process.
• Traction level. The better the draft, the faster steam is removed and less moisture settles on the pipe walls. It simply does not have time to mix with other combustion products. If the draft is bad, a vicious circle is obtained: condensate accumulates in the chimney, contributing to clogging and further worsening the circulation of gases.
• The temperature of the air in the pipe and the gases leaving the heater. The first time after kindling, smoke moves along an unheated channel, also having a low temperature. It is at the start that the greatest condensation occurs. Therefore, systems that operate constantly, without regular shutdowns, are least susceptible to condensation.
• Temperature and humidity of the environment. In the cold season, due to the temperature difference inside the chimney and outside, as well as increased air humidity, condensate forms more actively on the outer and end parts of the pipe.
• The material from which the chimney is made. Brick and asbestos cement prevent the dripping of moisture drops and absorb the resulting acids. Metal pipes can be prone to corrosion and rust. Chimneys made of ceramic blocks or stainless steel sections prevent chemically aggressive compounds from catching on a smooth surface. The smoother, smoother the inner surface and the lower the moisture absorption capacity of the pipe material, the less condensate is formed in it.
• Integrity of the chimney structure. In case of violation of the tightness of the pipe, the appearance of damage on its inner surface, the draft deteriorates, the channel becomes clogged faster, moisture from the outside can get inside. All this leads to increased steam condensation and deterioration of the chimney.

Modern man is very thermophilic. If you, our dear reader, have your own house, then you have to solve the problem of heating it yourself. But modern heating equipment is different from the fireplaces of the past; along with an increase in efficiency, the complexity of the design increases and the maintenance of the units becomes more complicated.

During the operation of modern boilers, stoves and fireplaces, condensation is necessarily formed in the chimney.

Whatever type of fuel you use, you are burning hydrocarbons. Coal, coke, firewood, fuel oil, gas, pellets - everything consists of hydrogen and carbon with small impurities of sulfur and some other chemical elements. Any fuel also contains a small amount of water - it is impossible to completely remove it. During combustion, they are oxidized by atmospheric oxygen and the output is water, carbon dioxide, and other oxides.

Sulfur oxides react with water at high temperatures and form very aggressive acids (sulphuric, sulphurous, etc.), which also enter the condensate. A few other acids are also formed: hydrochloric, nitric.

What is dangerous condensate

There are two immediate dangers in the formation of condensate:

• when condensate freezes in the form of ice on the pipe mouth or deflector, the pipe section overlaps until it is completely closed - as a result, the draft decreases, the draft may tip over (back draft), combustion products (carbon dioxide and carbon monoxide gases) will enter the living room and cause severe poisoning of people; hot gases can cause a fire.
• with a very large amount, the liquid can extinguish the fire, for example, in a fireplace - with a direct-flow tube).

Consequences of condensation in pipes

The aggressive acidic environment, gathering on the walls of the chimney, leads to its rapid destruction - acids corrode steel, corrosion occurs - the metal quickly rusts and “burns out”. are also destroyed by acid condensate.

In addition, the condensate flowing into the boiler furnace destroys the heating unit (and with a very large amount, it can also extinguish the fire in the furnace).

A large amount of moisture settling on the walls can also lead to unpleasant consequences:

• moisture settling in the upper part of a brick chimney leads to its wetting and constant freezing and heating - this leads to the rapid destruction of such a pipe;
• condensate flowing into the boiler furnace destroys the heating unit;
• when the steel pipe “burns out”, moisture enters the insulation, freezes and thaws - the pipe also collapses very quickly.

The photo below shows the consequences of repeated freezing of a brick pipe.

Causes of condensation in the chimney pipe

The waste gases contain water and other liquids in the form of steam. When gases are cooled, the steam becomes supersaturated, water collects in droplets and tends to go down - this is the main reason for the appearance of condensate. In a stream of hot gases, this process occurs at the colder walls of the chimney - and it is there that drops of liquid settle, forming condensate.

When considering the reasons for the appearance of condensate, it should be borne in mind that there is no smoke without water vapor, the presence of liquid collecting on the walls of the chimney cannot be avoided.

Reasons for the increase in the amount of condensing liquid in the chimneys:

• , especially from single-layer galvanized pipes;
• too long pipe - in the upper part there is a significant cooling of the smoke;
• low exhaust gas temperature. This is especially true for modern units with a heat exchanger for connecting the heating system. It is desirable that the temperature of the gases leaving the furnace head be at least 100 °C;
• a large difference between the temperature of the ambient air and the outgoing smoke;
• raw fuel (especially firewood);
• narrowing of the lumen of the hog due to soot deposits and, as a result, a decrease in traction;
• low combustion temperature with incomplete combustion of the fuel due to insufficient supply of fresh air, which leads to a low smoke temperature and low thrust;
• design flaws of the chimney - the presence of horizontal and inclined sections (in excess of the allowable standards of 2000 mm of horizontal projection); inconsistency of the cross-sectional area of ​​the channel with the design area (and it is bad to both reduce and increase the cross-section);
• the ingress of precipitation in the absence of a deflector or cap increases the amount of liquid in the chimney channel;
• Rough walls slow down exhaust gases more and collect more condensate than smooth ones.

Ways to get rid of condensation

It is impossible to completely eliminate the condensate. If you think that “previously, stoves were heated for centuries and there was no condensate,” then you should keep in mind that now the fuel is burned almost completely, the efficiency of heating units is greater than that of more primitive models of wood-burning stoves and fireplaces of past centuries, the flue gas temperature is lower - hence the greater amount of aggressive liquid in the chimneys.

It is possible to achieve such operation of the equipment and the design of the pipe that almost all the condensate will be carried into the atmosphere by very hot smoke - but it will also take away a considerable share of the heat and your money.

But not all is lost - measures can be taken to reduce the amount of condensed liquid

Chimney channel insulation

Alpha and omega chimney devices. Any chimney must be insulated to the very tip. Old brick pipes are also recommended to be additionally insulated above the roof and in the attic.

An uninsulated chimney has no right to exist at all.

Fuel pre-drying

Firewood needs to dry! First - under a canopy or in a spacious ventilated barn, the optimal drying time is one and a half to two years. Finely chopped firewood dries faster. Before use - let them lie down for a week or more in a warm, dry room. Constantly burning wet wood will introduce a lot of moisture into the smoke, waste wood, incomplete combustion, and release a lot of soot (and the need for more frequent cleaning of the flue).

Coal, peat - do not wet. Bring it into the room in advance, let it warm up and dry out the moisture that has settled on it. Pellets, briquettes - keep away from getting wet, store in a dry, warm room.

The right choice of fuel

Firewood, pellets, briquettes (especially firewood) initially have a higher moisture content than firewood or fuel oil. But it is more reasonable to choose the type of fuel for the heating unit, based on the parameters of the cost of fuel, availability in your area, and the need to automate the heating system.

Chimney cleaning

The smoother the inner surface of the smoke channel, the better the draft and the more moisture will “fly away into the pipe”. Therefore, the chimney should be cleaned of soot regularly, without waiting for the draft to deteriorate - at least twice a year. Cleaning methods - mechanical or chemical - are of fundamental importance.

Different types of fuel produce different amounts of soot. For example, for a gas boiler, the amount of soot formed is minimal, for a coal stove it is maximum.

- quite an affordable event to do it yourself. On our video you will see all the details of cleaning the chimney.

Using a steam trap

What to do if condensate flows along the walls of the chimney? Install a condensate collector. This is an absolutely necessary measure in modern heating systems. A steam trap is a stainless steel container for collecting condensate, mounted in the lower part of the vertical channel, below the outlet channel or branch pipe of the heating unit, with access for emptying it. Sometimes they arrange a constant removal of condensate from the tank to the sewer. In modern metal "sandwich systems" and ceramic pipes, there are ready-made sections for mounting such containers in the assortment.

Old chimneys should also be upgraded by building a steam trap into the lower part.

Condensation Prevention

The main preventive measures to reduce the amount of condensate:

• even at the design stage - compliance with all standards for the construction of the chimney system;
• installation of a chimney without deviations from the project;
• modernization of existing pipes (you can protect the channel by inserting stainless steel liners; insulation);
• traction enhancement by all available means - installation of deflectors, smoke exhausters, rotary turbines; reliable air supply to the heating unit;
• regular cleaning of the pipe;
• use of dry fuel.

Requirements for the design of the chimney

Requirements for the design of chimneys are determined by SNiP 41-01-2003.

Primary requirements:

• channel height should not be less than 5 m;
• the height of the pipe above the roof is at least 1 m for a flat roof;
• the height of the pipe with a pitched roof is determined depending on the ridge (at a distance from the ridge to the head (horizontally) of 1.5 m - at least 0.5 mm; at a distance of 1.5 m to 3 m - flush with the ridge; at a distance more than 3 m - the angle between the horizontal and the line passing through the top of the pipe and the ridge should not exceed 10 °);
• the length of the horizontal hog should not exceed 1 m;
• the sum of projections on the horizontal of horizontal and inclined sections should not exceed 2 m, while the length of the vertical section increases by the same length.

Conclusion

We hope, our dear reader, that this article will help you understand the operation of modern chimneys, choose the optimal design of the smoke exhaust system for your home, and protect equipment from aggressive condensate. Subscribe to our newsletter - and you will not miss new useful information about construction and repairs and will be able to discuss it with friends on social networks.

The surrounding air always contains moisture. Think foggy windows in damp weather or wet walls in the bathroom. When air or flue gases cool down to a critical temperature (down to the "dew point") in contact with the colder walls of the boiler or chimney, condensate drops form. Many boiler owners immediately begin to panic as soon as they see water in the boiler and believe that the boiler has leaked. Mixing with soot particles, this water becomes black, thick, "like oil." This substance covers the heat transfer surfaces of the boiler and significantly reduces heat transfer, resulting in power loss. In addition, this liquid has a very aggressive property - it begins to corrode the boiler walls and welds due to the formation of sulfurous acid. If nothing is done, the heat exchanger and chimney will be damaged.

Condensation can form in the boiler itself (on the walls of the furnace and in the heat exchanger), as well as in the chimney. At the same time, owners of pellet boilers and long-burning solid fuel boilers often face this, since the flue gases there have a lower outlet temperature. But all problems can be solved even when designing a boiler room and using high-quality fuel.

The amount of condensate depends on the ambient air temperature, air humidity and the moisture content of the fuel used.

Chimney problems

Often, when using a solid fuel boiler, they do not pay much attention to the chimney. But the operation of the entire heating system depends on it almost 100%. There is no sufficient draft - the power of the boiler is lost, the boiler starts to smoke. A chimney of a smaller diameter is used - it also leads to a significant decrease in power, since there will not be enough oxygen to burn the required amount of fuel per unit time. A cold pipe, no insulation - condensate forms, which begins to flow down the pipe walls into the boiler.

If the pipe is insulated, but a thick-walled steel pipe is used, then condensation will form until the entire pipe warms up. If it is a pellet boiler, then it will be quite difficult to warm up such a pipe, since the exhaust gases have a low temperature. In addition, the pellet boiler in the mode of maintaining the temperature in the room may be off for a long time, and when it is turned on again, condensate will form. Therefore, for any pellet boilers, we recommend using only insulated sandwich pipes (they usually have a wall thickness of up to 1 mm). In extreme cases, you can connect the boiler to a brick chimney. Long-burning boilers can also be in combustion maintenance modes with a low flue gas temperature, so it is also desirable to use sandwich pipes and brick chimneys for them. If the boiler will be mainly operated in maximum power modes, then it is allowed to use thick-walled insulated pipes.

In order to reduce the cost of purchasing a chimney, it is enough to insulate a part of the chimney located in unheated premises and on the street. In addition, in this case, part of the heat from the uninsulated pipe will be transferred into the room, further reducing heating costs.

A cold brick pipe can also be destroyed by such acid. Over time, traces of such an impact are noticeable on the pipe, and through the seams in the brickwork, smoke begins to enter the premises of a private house. High-quality solid bricks should be used and masonry joints should be filled with high quality. It is recommended that the pipe wall thickness be at least 25cm. To connect the brick pipe to the boiler, you can use a steel bend of a suitable size.

The easiest and most costly way to solve problems with a chimney is to use a ready-made insulated stainless steel pipe - a sandwich pipe. Such a pipe consists of two concentric pipes, between which there is a heater. The thickness of the insulation layer and the material of the inner pipe is selected based on the characteristics of the heating boiler. Boiler characteristics include flue gas temperature and fuel used. For solid fuel boilers, pipes made of high-quality stainless steels that are resistant to aggressive environments are used, for example, AISI 304, 310 or 316 steel. Sandwich pipes are quite light, and their installation is not complicated. Pipes are inserted one into another using crimping clamps. There are various connecting elements of such smoke systems - tees, transitions from the boiler nozzle to the main pipe, bends, passages through walls, passages through ceilings and roofs.

An asbestos-cement chimney can be used. However, such pipes are "afraid" of flue gases that are too hot. Therefore, it is recommended to make a section of about 2 meters at the outlet of the boiler from a steel pipe, and then use asbestos-cement.

Proper operation of the boiler and heating system

Do not turn on the circulation pump of the heating system at a negative temperature in the heating system. It is advisable to turn on the pump after the boiler has warmed up to a temperature of at least 50-60 degrees.
Otherwise, there is also a problem of condensate formation in the boiler furnace and heat exchanger.
As the boiler operates and the heating system warms up, the condensate will, of course, evaporate, but this takes time and additional energy to evaporate moisture.

The question arises - how to control the inclusion of the pump?

The first option - free of charge - we stand next to the boiler and control the temperature with a thermometer at the boiler outlet. After the boiler has warmed up, it is necessary to turn on the pump at the minimum speed and observe the temperature change. If the temperature rises quickly enough, then it is necessary to increase the speed of the circulation pump. The optimal mode from the point of view of efficiency and durability of the boiler is the flow of coolant into the boiler with a temperature of 50-60 degrees.

The second option is to use an automation unit that controls the operation of the heating system pump. The control unit monitors the temperature at the outlet of the boiler and turns on the pump only when the temperature at the outlet of the boiler is above the set threshold value. In long-burning START boilers, as well as in pellet boilers, circulation pumps are connected to the automation unit, in which these pump switching algorithms are organized.

The third option is to organize a small circulation circuit through the boiler using a three-way valve and an additional circulation pump. This ensures the most correct mode of operation of the heating boiler. The boiler operates in the same mode and the possibility of condensate formation is almost completely excluded (only during the start-up period).

Choice of quality fuel

You can also extend the life of your boiler and make it easier for yourself to clean it if you use high-quality fuel - fuel with low humidity. Naturally, the most ideal fuel with a moisture content of less than 10% is pellets and other briquetted fuels. Briquetted fuel will also allow you to get a longer burning of one fuel tab. Pellets can only be used in a specialized pellet boiler. Thus, a pellet boiler and pellet fuel are an ideal pair that makes life as easy as possible for the owner of such an automatic solid fuel boiler.

Condensation is a physical phenomenon that manifests itself when there is a temperature difference between the environment and the walls of the smoke channel. As a result, moisture is produced, which adversely affects the condition of the chimney and gas boiler, forming puddles when working with it and reducing efficiency.

Moisture on the walls of the chimney

Causes

Condensation is strongly formed due to:

• season and climatic factors;
• fuel quality;
• inappropriate material for the exhaust pipe of combustion products;
• improperly designed chimney.

In winter, the moisture on the inner pipe of the chimney freezes, because its walls are cold, it turns into ice plugs, and over the top - into icicles. Over time, the operation of the gas boiler, the pipe gradually heats up, the ice thaws, moisture flows to the nozzle, disrupts the operation of the burner and negatively affects the general condition of the chimney.

The chemical composition of the fuel enhances the formation of condensate. When it is burned, water vapor is released, which remains on the walls of the chimney channel, combines with moisture and salts of flue gases. Thus, aggressive acids are formed that corrode the surface of the pipes.

The very principle of operation and design of the boiler contributes to the formation of condensate. The chimney duct system for gas heating appliances is cold. The temperature of the exhaust gases is insignificant (up to 120 ° C) and does not have time to warm up the chimney, so moisture always forms on its pipe.

Due to the settings mode, the device works periodically and turns off when the system has reached the marked temperature indicators, which also excludes the optimal heating of the outlet channel.

Rust is a sign of condensation

The appearance of moisture in double-circuit boilers

In addition to the chimney, condensate also appears on the water pipe of a 2-circuit gas boiler. It occurs due to the temperature difference between the water in the supply channel and the environment. As a result, the pipe becomes rusty and damages the equipment.

There are several reasons for this:

• violation of the ventilation, check it by leaving the door in the room open at night, if the next morning the upper part of the pipe is dry, the reason is poor exhaust;
• unfavorable microclimate in the room, which is normalized by ventilation, air conditioning or installation of a moisture absorber;
• incorrectly set device operation mode.

Due to the peculiarities of the operation of a 2-circuit boiler, it is impossible to completely get rid of condensate, however, a number of tricks will help, thanks to which the formation of moisture will decrease. These include:

• thermal insulation of pipes of the circuit;
• chimney insulation.

The following act as a heat insulator for the contour pipe: foamed polyethylene, polyurethane foam, mineral wool boards, liquid ceramic compounds and others. They are purchased in the store and selected based on the characteristics and brand of equipment.

Features of pipe insulation:

• before installing a heat insulator, the pipe is sanded, treated with acetone and phosphoric acid, epoxy putty or primer is applied;
• the diameter of the thermal insulator is 2-3 mm larger than the diameter of the pipe;
• before installation, the material is cut into segments, the number of which depends on the length of the pipes;
• when arranging a section on a pipe, the technical section is at the bottom and is wrapped with a strong thread from above;
• the space between the pipe and the insulation is filled with mounting foam.

Pipe insulation

Influence of pipe material on the occurrence of excess moisture

In a gas boiler, unlike an electric or solid fuel one, condensate is constantly formed, therefore the material and thermal insulation of pipes for arranging a chimney are very important and are reflected in the safe and trouble-free operation of the device.

The optimal types of pipes for a gas boiler are:

• made of stainless steel, resistant to aggressive acids, smooth, assembled according to the "sandwich" principle - a pipe of a smaller diameter is in a pipe of a larger one;
• sandwich pipes, consist of internal and external contours, between which a thick layer of insulation (stone wool) is placed;
• ceramic, the most expensive, are distinguished by strength and durability, fireproof, heat up quickly and cool down slowly, resistant to chemical compounds, easy to maintain, insulated with mineral plates and expanded clay shell;
• coaxial, do not form condensate, built according to the “pipe in pipe” principle, where combustion products are discharged through one of them, and fresh air from outside the room enters through the other to ensure the process of maintaining the flame in the boiler, with high efficiency, safe.

The shape of pipes is allowed only oval or round. The square chimney contributes to increased soot accumulation. It is better not to use a brick or asbestos-cement channel for the removal of combustion products - they are destroyed by acidic compounds, are not sufficiently sealed and thermally insulated, and absorb moisture.

Brick chimney under the influence of condensate

Is it possible to calculate the probability of condensation occurring

Condensate is formed when the thermal power of the gas boiler is unreasonably exceeded and causes the walls of the chimney to burn out. So that the power of the equipment does not affect the formation of excess moisture, the optimal value is calculated.

For standard rooms, the normal indicator is 1 kW per 10 m2 of the room. In rooms whose ceiling height does not reach 3 meters, the following indicators serve as the basis for calculating the power formula (MK, kW):

• UMK - the specific power of the boiler, associated with the climatic zone of residence and calculated for every 10 m2 of the room;
• S is the area of ​​the room in which the boiler is installed (m2).

The formula itself looks like SXUMK/10= MK. The TMC indicator is standard and equal to:

• 7-0.9 in southern zones;
• 1-1.2 for middle latitudes;
• 2-1.5 for the Moscow region;
• 5-2.0 for northern regions.

Burnt chimney walls

If the boiler is 2-circuit, then in order to prevent condensate from forming, multiply the result by 25%. With ceilings above 3 meters and a non-standard layout of the room, the boiler power (MK) is calculated by the formula:

Qt*Kzap, whereQt- coefficient of predicted heat losses, Kzap - safety factor (1.15 for single-circuit and 1.2 for 2-circuit boilers).

• V– room volume (m3);
• Pt- the difference between the internal and external temperatures (°C) ;
• K- coefficient of dispersion, depending on the presence of thermal insulation of the room (from 3.0-4.0 in the absence of insulation to 0.6-0.9 for well-insulated rooms (with insulation of the floor, roof, walls and windows).

The final formula looks like V*Pt*k/860 = Qt.

Dew point

The process by which water vapor in a chimney begins to precipitate and form condensate is called "dew point". It depends on the indicators of absolute, maximum possible humidity, depending on the air temperature on that day, the actual air humidity at the moment and the difference between these indicators. You can find out at what temperature the dew point appears in the table below.

Dew point definition table

It can be seen from it that if the air temperature is 5 degrees Celsius, and the air humidity does not exceed 70%, then the dew point appears at a temperature of -5 ° C and moisture will begin to appear on the walls of the chimney.

Installation rules

To prevent condensation from accumulating, the chimney system must be:

• waterproof;
• tight;
• protected from corrosion;
• insulated.

These conditions can only be ensured by the correct installation of the chimney, the choice of its materials, insulation and sealing during the assembly process. A description of the nuances of these processes can be found in the video below, with a brief overview of the types of chimneys and the requirements for their installation.

Basic provisions:

• the lower pipe is located with a bell to the outlet;
• all joints are treated with sealant;
• vertical deviations within 30% are allowed;
• horizontal distance does not exceed 1 meter;
• the cross section of the pipes throughout the channel is the same.

T-shaped condensate trap

Forbidden:

• the use of a brick chimney;
• the use of fungi and umbrellas at the head of the outlet.

To prevent condensate from collecting, it is necessary to have a condensate collector and a drain, ensuring good traction. It is important not to forget about the planned cleaning of the gas boiler and the prevention of the condition of the internal walls of the chimney.

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