What to do if there is condensation in a gas boiler: methods for preventing the formation of “dew” in the chimney

Along with the increase in the efficiency of modern heating equipment, the complexity of the units increases and the requirements for its maintenance increase. Agree, it is extremely unpleasant if, a year or two after installing the device, you find condensation in the gas boiler: we will tell you what to do in this case below.

If urgent measures are not taken, the equipment itself and the chimney will begin to collapse. At the same time, inside a house equipped with a heating system, the walls will become damp, red stains will form, black mold will appear, and the finishing will become unusable.

A properly selected and correctly installed chimney will solve all problems. A condensate drain will also help cope with the situation, which will significantly extend the service life of the chimney exhaust system. From the article we have proposed, you will learn what condensation is, how to get rid of it and what a chimney should be like.

What is condensate?

Condensation is a liquid that settles on the walls of the chimney as a result of temperature changes. In modern gas equipment, the exhaust gases have a low temperature.

Reasons for condensation:

• improperly insulated chimney;
• sudden temperature change;
• unheated pipes;
• clogging of the smoke channel;
• low exhaust gas temperature (ideally, the temperature should not be lower than 100 °C);
• a very long chimney pipe, resulting in excessive cooling of the smoke;
• rough chimney walls (collect more water than smooth ones);
• violations in the design;
• problems with traction.

During operation of a gas boiler, in addition to water, carbon dioxide and other chemical compounds (oxides) are also released.

Since modern boilers are switched off periodically, the chimney walls are cooled from top to bottom. Condensation forms when the gas temperature drops to 40-60°C

Under the influence of high temperature, oxides react with water and aggressive acids are formed (nitric, hydrochloric, sulfuric, etc.). They settle on the surface of the equipment along with condensing vapors. An aggressive acidic environment leads to rapid destruction of the chimney pipe.

Why the resulting moisture is dangerous:

• if condensate freezes in the deflector or at the mouth of the pipe, the cross-section of the chimney is blocked, as a result, the draft decreases, which can lead to the formation of reverse draft and combustion products will enter the house, causing poisoning of its inhabitants;
• Large amounts of water can extinguish the flame, allowing carbon monoxide to enter the room.

In addition, if moisture gets into the boiler firebox, its walls will collapse. As a result of destruction, toxic combustion products will partially enter the house.

Condensation leads to the destruction of the chimney. If the problem is not corrected, a complete restoration of the pipe will be required in the future.

Exhaust gases contain water in the form of steam. When the temperature of the gases drops, the steam becomes supersaturated and droplets form.When the gases are hot, condensation occurs at the cooler walls of the chimney, where drops of liquid settle.

Why does moisture appear in gas boilers?

In addition to the condensate in chimney of a gas boiler Moisture can also form in water pipes. The main reason lies in the temperature difference.

The appearance of “dew” on pipelines is also affected by:

• improper ventilation operation (insufficiently powerful exhaust hood);
• high level of humidity in the room;
• incorrect operation of heating equipment.

The design of a gas boiler does not allow you to completely get rid of condensate. However, you have the power to reduce the rate of moisture formation and its amount.

Fighting condensation in an atmospheric boiler

If the house has an atmospheric wall or floor standing gas boiler, then the combustion products heat up to 170-200°C. The gases formed during combustion also contain water. However, it does not condense, but turns into steam and is discharged through the smoke channel along with other smoke and volatile soot particles.

When starting up floor-standing gas equipment after a long period of inactivity, a small amount of condensation is allowed to appear, which will evaporate after the boiler warms up. During the cold season, the boiler operates non-stop, so the appearance of liquid is unlikely

If condensation forms in the chimney pipe, then the problem is poor-quality thermal insulation of the chimney. Moreover, the formation of condensate drops on the smoke duct can occur either due to insufficient insulation or due to excessive insulation.

In pipes made of stainless steel, the problem of condensation formation can be solved by installing a condensate neutralizer and adding an element for removing condensation moisture that settles on the surface of the pipe.

When assembling conventional metal chimneys and sandwich chimneys, it is imperative to follow the order of assembly and connection of elements, which provides for spontaneous drainage of condensate outside the smoke channel.

Warning of "dew" in a turbine boiler

Models with a closed burner are equipped coaxial chimney. It has a slope of 3° in the outward direction, i.e. from the boiler, it ensures spontaneous drainage of condensate to the street.

The internal channel of the coaxial system is constantly cooled by the air flow coming from outside, due to which the temperature difference during normal operation is minimal.

The standard length of a coaxial smoke exhaust system is 1.2 meters. If extension is necessary, (necessarily indoors) the distance should not exceed 6 meters. There must be at least 0.6 m between the outlet of the outer part of the coaxial chimney and the nearest obstacle (wall, large tree, etc.).

If the boiler is equipped with a coaxial chimney, problems with condensation formation arise during frosty periods. They are solved by insulating the part of the smoke duct located outside the house, increasing ventilation or starting the boiler at full power.

When using a boiler with a coaxial chimney in the northern regions, it is advisable to insulate the outer part of the exhaust pipe. This way you can prevent the formation of condensation on chimney of a gas boiler. After all, the difference between the temperatures of the incoming air flow and the outgoing flue gases will be reduced.

You can temporarily provide the boiler with air flow from the room. Most turbocharged models of floor and wall-mounted gas boilers designed for the possibility of installing separate supply and exhaust systems. You just need to find the plug for the hole to which the exhaust pipe should be connected and open it slightly.

With the exhaust duct plug slightly open, you can wait out the frost. Then it should be covered tightly. In these cases, it also helps to increase the boiler power during frosty periods. In automated systems, a temporary reduction in the interval between the boiler activation and shutdown temperatures set by the owners works well.

Features of condensing boilers

The ideal solution would be a condensing boiler that is correctly balanced with the heating system, correctly configured and operating in the appropriate mode. In this case, the appearance of condensation is absolutely not harmful, because its energy is rationally used by the system itself.

The amount of gas saved directly depends on the amount of condensate formed. The condensation heat generated during operation of the equipment is collected and redirected to the heating circuit. The efficiency of such a boiler is 98%.

Is it possible to drain condensate into the sewer?

During operation of a gas boiler, oxides are formed that react with water vapor. As a result, carbonic and sulfuric acids are formed, the average pH of which is 4. For comparison, the pH of beer is 4.5.

The acidic solution is so weak that there are no restrictions on discharge into public sewers.This rule applies if condensation has formed on the pipe of a gas boiler operating in an apartment.

The only condition is that the condensate must be diluted with wastewater 1 to 25. If the boiler power is more than 200 kW, it is necessary to install a condensate neutralizer. This requirement is indicated by the manufacturer in the equipment passport.

It is impossible to collect condensate into an autonomous sewer system that discharges wastewater into a septic tank with anaerobic bacteria or into a deep treatment station using anaerobes and aerobes. It will destroy the biological environment involved in the cleaning process.

Requirements for the chimney of gas boilers

Today, in the construction of chimneys for gas boilers, various materials are used, most of which are impractical. The quality of execution also leaves much to be desired.

Chimney made of asbestos cement. In the past, such chimneys had no alternative. Their main advantage is low cost.

Flaws:

• installation is carried out exclusively on vertical sections of pipes;
• heavy weight and length, which complicates installation;
• joints are not sealed;
• the resulting moisture is absorbed into the walls;
• the temperature of the exhaust gases is not higher than 300 ºС.

It is important to connect the boiler to the chimney correctly. A tee is used for this purpose.

If a tee is used in the chimney, then installation is carried out “through the smoke”. In its absence, “by condensation”

A condensate drain and a cleaning hatch are required.

Brick chimneys. This material is not recommended for installing systems with gas boilers. According to the requirements specified in the collection SNiP 41-01-2003, smoke exhaust channels for gas processing equipment must be smooth and classified as class P in terms of gas tightness.

If a brick smoke duct is quite suitable in terms of gas tightness characteristics, then there can be no talk at all about the smoothness of the walls inside the pipe. Even if the seams of a brick pipe are perfectly sanded with mortar flush with the brickwork, during operation the relief will still appear due to the difference in the density of the material and the binder.

The ideal solution would be to install a metal sleeve inside the brick channel or assemble it from ceramic modules. A brick pipe with a metal or ceramic insert inside can last more than 30 years without problems.

Furanflex lining is suitable for the same purpose. This polymer hose is made of composite (plastic reinforced with high-strength fibers). It is resistant to acid condensate and has low thermal conductivity. Permissible temperature of use is up to 200 ºС.

Ceramic smoke channels. This material is strong and durable. Ceramic chimney resistant to aggressive acids, easy to maintain and fireproof.

Ceramics can heat up quickly and take a long time to cool down. Installation of such a chimney requires the participation of specialists. The downside is the high cost.

Galvanized and steel. When exposed to moisture, steel rusts. The maximum shelf life of such pipes is up to three years. Galvanized chimneys, protected from rust by a layer of zinc, last for five years or more.

If moisture does not penetrate into the boiler, it accumulates in the lower part of the chimney (in the house), which leads to an unpleasant odor. At the same time, this is a vulnerable place where acid accumulates, which over time will “eat away” this area

Stainless steel pipes. An ideal choice for arranging the smoke duct of a gas boiler. Its installation will cost several tens of times less than the construction of a brick chimney. The walls are smooth, soot and resins will not settle on them, the gas density is quite high.

To assemble a chimney, you can purchase a set of single-layer modules or buy elements of a sandwich system. You can assemble such a structure with your own hands without much effort. The main thing is to follow the direction when forming connecting nodes.

Insulation and finishing of the chimney improve the aesthetics of the building, which gives the house a more well-kept appearance

Advantages of stainless steel chimneys:

• due to the round cross-section and smooth surface they provide good traction;
• sealed;
• they quickly overcome the condensation threshold;
• easy to maintain;
• fireproof;
• durable.

The quality of steel, welding seam, and joints between elements is also important.

When sealing seams, you need to pay great attention to the sealant. Some brands “petrify” and crack during use

The fact that chimney repair is much more expensive than proper installation at the stage of installing gas equipment is often not taken into account.

Chimney installation rules

The entire system must be insulated, waterproof and protected from aggressive materials.

Basic principles applied during installation:

• The chimney should be assembled using the “condensate”;
• each joint is treated with a sealing compound;
• It is better to retreat from the vertical by a maximum of 30%;
• the length of inclined sections constructed at an angle of no more than 30º to the horizon - up to one meter;
• Components of the same cross-section are used along the entire length of the channel.

It is recommended to install ready-made chimney kits, which are available in specialized stores.

Placing an acid-resistant liner and a condensate collector makes it possible to delay the dismantling of the old chimney and allows you to save a significant amount. However, be prepared for decreased cravings

Recommended parameters of the chimney system for gas boilers:

• for the manufacture of the chimney it is necessary to use corrosion-resistant steel type AISI 321;
• minimum thermal insulation - 50 mm;
• The system must include: a tee with a condensate collector, as well as a protective cone over the upper section of the chimney.

When choosing a chimney, you should pay attention to these characteristics.

Preventing condensation

You won’t be able to forget about moisture in the chimney forever. The formation of condensate is inevitable, although with constant operation of gas equipment, the “drops” deposited during startup will evaporate on their own and will no longer fall out while the unit is operating at full power.

To reduce the amount of moisture generated, reduce the circulation in the system when starting the boiler. Let the boiler heat the coolant in the heat exchanger to at least 60⁰C. Afterwards you can increase the pump speed. Do not allow the temperature to drop below 30⁰WITH

How to reduce the amount of condensation:

• insulate the chimney duct;
• clean the system in a timely manner;
• use a condensate drain.

If condensate accumulates in a gas heating boiler, you should install a container to collect excess liquid. A condensate trap is a container made of stainless steel in which the moisture that appears is collected.

It is also recommended to modernize old chimney pipes by installing a condensate drain tank at the bottom

The device is mounted under the outlet channel or pipe of the gas equipment. They also install permanent drainage into the sewer system.

It is better to prevent the problem of moisture formation in the chimney than to waste time and money on solving it.

The optimal solution for eliminating condensate would be to equip the pipe with an acid-resistant stainless steel channel, a drain and an additional collector

Measures to prevent the appearance of moisture:

• adhere to all standards during the construction phase of the building;
• when installing the chimney, strictly follow the design;
• regularly maintain the smoke duct using specialized chimney cleaning products;
• modernization of existing pipes (insulation, insertion of stainless steel liners);
• monitor the draft power and clean the chimney on time.

The chimney is insulated using mineral wool or fiber insulation. To insulate a brick chimney, plaster is used, which is laid in seven layers.

Determining the probability of condensation formation

Calculations can be carried out if condensation is formed as a result of a large release of steam and overheating of the chimney walls, and the power of the operating equipment is known. The average rate of heat release is 1 kW per 10 sq. m.

The formula is relevant for rooms with ceilings below 3 m:

MK = S*UMK/10

MK - boiler power (kW);

S is the area of ​​the building where the equipment is installed;

WMC is an indicator depending on the climate zone.

Indicator for different climatic zones:

• south - 0.9;
• north - 2;
• middle latitudes - 1.2.

When operating a double-circuit boiler, the resulting MK indicator should be multiplied by an additional coefficient (0.25).

Conclusions and useful video on the topic

The following video will provide information on how to protect the boiler from condensation:

Features and advantages of installing a condensate trap are presented in the video:

The formation of condensation in the chimney is inevitable. Since this cannot be avoided, we have told you how to reduce moisture quality and protect equipment from aggressive liquids.

It is recommended to reinforce the chimney with stainless steel plates, install a condensate collector and monitor the presence of draft. Do not forget about cleaning the chimney, as well as preventing the condition of its walls.

If you have successful experience in “fighting” condensation, share your secrets in the comments. Readers who have questions can ask our experts online.