Why is water flowing from the chimney. Chimney Condensation and Dew Point
Stoves and fireplaces give any home a kind of comfort, but, like any heating systems they require regular care. Over time, condensation forms on the chimney pipe, which flows down and has a devastating effect on it. In the common people, this phenomenon is called "the oven is crying." You can avoid unpleasant consequences if you install a high-quality condensate collector at the stage of building a house. In its absence, there are several effective ways minimizing the formation of condensation.
Causes of condensation in the chimney
Condensate is a tarry liquid mass that settles on the inner walls of the chimney as a result of the contact of air flows of different temperatures. Hot smoke, rising through the pipe, gradually loses its temperature and, having cooled, releases water vapor, which condenses, turning into a liquid. In this case, it mixes with the products of combustion, resulting in the formation of acid.
Almost all modern gas installations have a sufficiently low temperature of the combustion products at the exit, which is the reason for the cold walls of the chimney. The formation of condensate begins already at a temperature of the outgoing gases of 45-60°C. And if in steel pipe, which has a smooth surface, the liquid flows down without lingering, then its gradual accumulation occurs on the brickwork, leading to the destruction of the pipe.
The amount of condensate can be different for a number of reasons, knowing them, you can minimize the formation of liquid on the walls of the chimney:
In addition to the above reasons, the appearance of liquid in the pipe can be triggered by a violation of its tightness. Cold air entering through the cracks from the outside will cool the gas flow and contribute to the condensation of water vapor.
To ensure normal traction, it is necessary to use exclusively dry fuel, which will quickly warm up the device and after its combustion there will be no deposits inside the pipe. Raw firewood does not provide the required amount of heat and, when burned, emits a lot of wet vapors that settle in the form of condensate. Using high-quality fuel will extend the life of the chimney and the stove itself. For normal drying, firewood should lie in a dry place for at least one and a half years.
Equipment running on natural gas is more susceptible to the harmful effects of condensate and therefore more likely to fail. When installing gas equipment, it is advisable to take care of the condensate collector in advance, otherwise you will have to constantly clean the chimney. Often in the operating instructions, the manufacturer indicates how best to protect the system from condensate.
Consequences of condensation inside the chimney
The water vapor of the exhaust gases, turning into water, settles on the cooled inner surface of the chimney. Drops of liquid, mixing with other products of combustion, flow down the pipe, gradually making it unusable.
This destructive effect is due to the aggressiveness of the mixture of condensate and soot deposits. The acid formed on the inner walls corrodes the metal and other materials from which the pipe is made over time. It should be noted that the problem of the appearance of acid condensate is inherent only furnace heating. In case of use gas equipment a liquid is formed only from water vapor.
Especially quickly, the acid solution destroys the brickwork of the upper section of the pipe, which in the cold season is often subjected to freezing and thawing. Crumbling bricks and dark streaks of an unpleasant odor are the consequences of irresponsible installation brick chimney in our climate.
Acid condensate eats through chimneys made of ordinary steel. Moreover, the attempts of some owners to protect them from the outside with anti-corrosion agents do not bring results, since the destruction occurs from the inside. Stainless steel pipes will last much longer.
The accumulation of liquid in the pipe also leads to a deterioration in draft, which will result in an unpleasant smell in the room.
Chimney Material
The amount of condensate formed and the normal functioning of the heating system for a long time to a large extent depends on the material of the chimney pipe. It is better to choose the best option even at the construction stage, otherwise the failed chimney will have to be completely changed, which will subsequently be problematic.
brick chimney
A brick pipe tends to accumulate heat and not cool down for a long time, preventing cold air from descending, which ensures normal draft in the chimney. But this advantage is at the same time a disadvantage of brickwork, since it takes quite a long time to heat up the pipe and at a low temperature of the channel, condensate is intensively formed. Brick pipes are most prone to failure due to sudden temperature changes in winter and exposure to an acid mixture. To prolong the life of the chimney, the inner cavity is lined with stainless steel pipes.
Stainless steel pipe
Such chimneys are of two types:
- single-walled;
- double-walled.
Double-walled pipes have additional insulation made of basalt fiber, which is laid between the inner and outer walls. Steel warms up quickly, providing normal traction and, thanks to the insulating layer, cools down for a long time, which reduces the possibility of condensation to a minimum. The smooth inner surface does not allow deposits from water and soot to accumulate. The only disadvantage of stainless steel chimneys is the possibility of icing on the outer surface when low temperatures and the need for additional insulation of single-wall pipes.
Ceramic pipes
Ceramics is a durable material that is resistant to the damaging effects of condensate. It warms up quickly, retains heat for a long time and is not afraid of soot fires. The cost of ceramic pipes is low, but due to the large weight, installation difficulties arise.
Furanflex chimneys
Furanflex is a modern composite material consisting of a polymer resin reinforced with fiberglass. Furanflex pipes are resistant to corrosion and aggressive environments and can be easily cleaned mechanically. Are issued with a diameter from 60 to 1000 mm. At the same time, the length of the chimney channel does not matter - polymer sleeves are available in any length. The finished furanflex channel will be absolutely sealed, providing normal traction and no leaks.
The installation of such a chimney does not require the dismantling of walls or structures. The installation process is clean and can be done when the finishing work is completed. The material is able to withstand temperatures up to 250°C for a long time. Manufacturers guarantee uninterrupted operation of furanflex pipes for 30 years.
How to avoid condensation
As noted above, it will not be possible to completely eliminate the formation of condensate, but it is possible to reduce its amount to a minimum. There are several proven ways to do this:
- increase the temperature of the exhaust gases at the outlet of the pipe, using dry, high-quality fuel for this;
- use chimneys made of heat-intensive materials that provide rapid heating and long-term cooling;
- additionally insulate the upper section of the pipe - this will reduce the temperature difference inside and outside the chimney;
- the chimney must be made of a material resistant to acid mixture;
- the chimney channel must be equipped with a container for collecting liquid and provide for the possibility for its revision and regular cleaning.
Not only the fuel used and suitable pipe material will help reduce the amount of condensate, but also a chimney system installed in accordance with all the rules:
- vertical deviation of the pipe should not be more than 30%;
- all existing joints must be securely sealed;
- the maximum length of the horizontal sections of the channel should not exceed 1 m;
- install pipes of the same diameter in all sections of the system.
To prevent the accumulation of condensate in the chimney, it is necessary to install a condensate collector and a drain. And do not forget about regular cleaning of the equipment and the internal cavity of the chimney.
Often, when the stove is fired, a black oily liquid with a characteristic unpleasant odor flows out of the pipes. This means that condensation forms in the oven. Condensation is formed when water vapor settles on cold walls. Water vapor is always present in flue gases. Their source is the moisture contained in the firewood. The damper the firewood, the more steam is produced. In addition, water is formed during the combustion of hydrocarbon fuels by combining two parts of oxygen with 1 part of hydrogen. When the temperature drops in the chimney, flue or bell-shaped part of the furnace on the walls, water vapor condenses on the walls. Condensate, mixed with combustion products, forms a black liquid, which is absorbed into the brick and after a while appears on the surface of the furnace in the form of dark spots. This leads to the rapid destruction of the brickwork.
Condensation is also the cause of the "burnout" of metal pipes. True, the pipes do not burn through, but are destroyed due to corrosion. The fact is that sulfur is present in the fuel. When it burns, sulfur dioxide is formed, which, when mixed with water, forms sulfuric acid. The destruction of the pipes does not occur in the lower, hottest part, but at the very top, where the temperature is lower. Condensation almost always forms in metal pipes. Therefore, for their manufacture it is necessary to use special stable grades of steel. The most common steel grade used for the manufacture of chimneys and chimneys is 304 stainless steel. It is heat resistant and resistant to weak acids. But it should not be used for boilers that use coal and gas as fuel. In this case, 316 stainless steel is used. It is an acid-resistant steel. And the most resistant to both heat and corrosion is 321 stainless steel.
What is the reason for the formation of condensate? Water evaporates and, accordingly, condenses at a temperature of 100 degrees Celsius. Therefore, the temperature at the outlet of the pipe must be at least 100 degrees. Better than 120. At the level of the upper gate, the temperature should not fall below 200 degrees Celsius.
To determine the temperature, a splinter is inserted into the shell of the upper gate. After 30-40 minutes, we take out the torch and clean off the soot. If the color of the torch has not changed, then the temperature of the gases is less than 150 degrees Celsius. At temperatures up to 200 degrees, the torch becomes yellow. If the torch is brown, then the temperature is up to 250 degrees. With more high temperature the beam is charred.
The decrease in the temperature of gases in chimneys occurs for the following reasons:
The presence of cracks and cracks in the masonry;
Air suction through cleaning doors;
Too much or too little air is supplied through the furnace blower. With a correctly adjusted air supply, the flame is straw-yellow;
Excessive length of smoke circuits or overestimated volume of the bell part. In this case, a partial or complete alteration of the furnace is necessary;
In the cold season, condensate can form when a pipe passes through an unheated second floor. Or when the pipe rises very high above the roof. In this case, it is necessary to insulate the pipe by plastering it or other finishing methods. The wall thickness of the pipe passing through the room must be at least 12 cm (half-brick laying). Pipes standing outside the walls of buildings are laid with a wall thickness of at least 1.5 bricks.
To avoid cooling of the pipe wall, do not increase the pipe cross-section beyond what is necessary. For furnaces with power up to 3000 kcal. h you need a pipe with an internal size of 13x13 cm (in the floor - bricks). For more powerful stoves, the chimney size is 13x27 cm (in brick).
Condensation can form when water enters the pipe. To protect against precipitation, it is necessary to protect the pipe with a cap.
In conclusion, I want to say that it is always easier to avoid such unpleasant things as the formation of condensate than to deal with it later. And for this you need to properly lay the stove. And it’s better to invite an experienced craftsman for this than to do the laying of the furnace yourself.
Condensation in a chimney is formed when water vapor passes through a cold chimney. There are 2 options to consider here.
1 option. When the heating unit is not working. Warm air from the room enters through leaks in the damper, brickwork or gaps due to improper installation of pipes. I already described this option in the article.
Here are some more recent photos
I often pass by this house and noticed the chimneys. Judging by the cross section, these are fireplace chimneys. On the right chimney, frost is visible on the cap, which is not on the left. I have never seen how the left fireplace is heated this winter, but the right one is heated about once a week. When heated, the cap heats up, and the condensate flows from the cap onto the otter, on which icicles growing upwards are visible. Condensation, which is absorbed into the brick, will destroy it when it freezes. I saw one such pipe that fell and broke through the slate. It was in a house with central heating. The stove was heated only in the off-season, when it was already cool in the house, and the heating was not yet connected.
Option 2. Condensation forms during combustion. Water vapor in flue gases also settles on the cold walls of the chimney. Where does the water vapor in flue gases come from?
1. From wet, poorly dried firewood
2. Combustion is an oxidation reaction, and the hydrogen contained in the wood is oxidized to water.
What can be done to reduce the formation of condensate?
1. Stoke the stove with well-dried firewood. To do this, they need to be split and kept under a canopy for 1.5-2 years.
2. Eliminate air leakage through the valve and other leaks.
At my stove, I sealed the gap between the frame and the valve with a sealant on the advice of Alexander Kutuzov.
If the suction goes through the leaks of the brickwork, then you need to cover the seams with mortar or plaster
3. Insulate the chimney. Water will not condense on a warm chimney. I observed this with two neighbors who live across the street from each other. They have stacked similar fireplaces and the height of the chimneys is approximately the same. One of them has a chimney running through a warm residential attic, and it has no problems with condensate.
4. Ensure that the temperature of the flue gases in the chimney is at least 100 degrees. Cold smoke comes out of the chimney when a small amount of wood is burned in a massive stove. The brick takes a lot of heat from the flue gases, and they exit the chimney cold. For example in 5 or 7 channel ovens. To increase the temperature of the exhaust gases, a straight channel of small cross section is made from the furnace to the last channel. Such a channel is called burnout, bypass or "ram".
A lot of heat can be taken from the flue gases and the boiler built into the furnace. I saw such a boiler built into a 5-channel furnace. The water in the heating system warmed up very well, and the furnace array almost did not heat up.
The temperature of the gases escaping into the pipe is also low in furnaces operating in glow mode. This happens when the blower door is tightly closed. For normal combustion, there is not enough oxygen and the temperature in the furnace is low. In addition to condensate, a lot of soot is formed in the chimneys of furnaces with this mode of operation. I will talk about soot in another article.
Well, now a question from a regular reader of my blog Anatoly:
Hello, Alexander!
I propose to discuss this topic in your blog, maybe someone will report fresh solutions. The question is how to assemble a sandwich chimney? It seems to be correct for condensate so that condensate does not flow into the gap between the inner and outer pipes. That's exactly what I did. The umbrella is also made in the rain - the inner tube is inserted into the tube located below, the outer part is put on the outer shell of the sandwich located below. On the one hand, this is correct. Rain will not flow between the sandwich pipes and condensate, and the rain that has flown into the pipe will drain onto the valve. But! Condensation began to flow from under the outer shell of the umbrella. When moving in the chimney, smoke enters under the section of the pipe located above, rises to the top and, reaching the top, forms condensate that flows from under the outer shell of the umbrella. This is bad. How to fix? In the photo, the arrows show the places where the condensate escapes, the photo was taken immediately after installation, so the place where the condensate appeared is not visible and had to be marked with arrows.
Heating in a private house is carried out using stoves of various types, each of which requires the construction of a chimney. The main problems of flue ducts are clogging of pipes and the formation of condensate. If the chimney is clogged, cleaning is required, but it is more difficult to deal with the formation of condensate. Condensation in the chimney pipe can lead to premature destruction of the chimney.
Causes of condensation
Condensation in the chimney can form for the following reasons:
- chimney blockage. With insufficient draft due to clogging of the chimney channel, the rate of passage of heated gas decreases, which leads to interaction with air and the formation of moisture;
- a large difference between the temperature of the exhaust gases and the temperature environment. In late autumn and winter, cold air is in the chimney, which, when interacting with hot gases, precipitates as a wet precipitate;
- use of wet fuel. When burning the stove, it is important to use dry wood or other fuel that has a minimum moisture content. The accumulation of moisture in the wood when exposed to high temperatures leads to the evaporation of the liquid and its settling on the chimneys;
- atmospheric precipitation entering the chimney pipe.
Troubleshooting
Depending on the cause of the condensate, a method is selected to eliminate it, which include:
- chimney cleaning;
- chimney insulation;
- rain protection.
How to clean a chimney
If the condensate chimney accumulates due to blockage, then an immediate flue duct is required. To clean the chimney, you can use:
- special chemicals that, when burned, decompose soot deposits. For example, the log "Chimney sweep";
- mechanical cleaning.
To clean pipes manually you will need:
The cleaning device smoothly lowers into the smoke channel from the roof of the house.
- folk remedies that were used in the villages. You can clean the smoke channel:
- ordinary salt, sprinkling it during the heating of the furnace;
- potato peelings, which are also loaded into the oven during the furnace.
With any cleaning method, elementary safety rules must be observed.
Chimney insulation
If condensate accumulates on the boiler pipe due to the use of heating equipment in the cold season, that is, the cause of moisture is the temperature difference, it is recommended to insulate the chimney.
As heaters you can use:
- mineral wool;
- any fibrous insulation;
- expanded polystyrene boards;
- plaster.
Mineral wool and fiber insulations are suitable for metal and asbestos-cement chimneys. The brick chimney is insulated by plastering the surface.
To insulate the chimney with fibrous materials or mineral wool, you need:
- cut the material into pieces required for wrapping the pipe;
- attach the material with metal wire or clamps over the entire surface of the chimney;
- close the insulation with a metal box or foil.
How to insulate brick pipe foam polystyrene plates can be seen in the video.
Plastering a brick chimney for the purpose of its insulation is carried out in several stages:
- a plaster mesh is attached to the wall of the chimney for better adhesion of materials. Fastening is required to be carried out with special bolts with an enlarged head;
- the first layer of plaster is applied, consisting of a mixture of cement, lime, water and fine slag. The thickness of the first layer should not exceed 4 cm;
- after some time required to dry the solution, the remaining layers are applied, which should be from 3 to 5;
- to give the chimney an aesthetic appearance after the plaster has dried, it can be painted.
To insulate the pipe, the total layer of plaster must be at least 7 cm.
How to protect the smoke channel from precipitation
To protect the chimney from atmospheric precipitation, special ones are used that are installed on the top of the chimney.
Some heads are equipped with built-in deflectors. Such devices not only protect the pipe from precipitation, but also contribute to increased draft in the chimney.
Condensation Prevention
To reduce the formation of condensate in chimneys, you can:
- install inside a brick chimney metal pipe. This technique is called guillization. An additional pipe facilitates the cleaning of a brick chimney, contributes to the insulation and sealing of the channel, as well as the removal of condensate;
- install a condensate collector in the chimney. The device is installed at the intersection of the vertical and horizontal sections of the chimney and helps to collect moisture from the pipe. Maintenance of the condensate collector consists in the timely removal of water.
Chimney prevention also consists of:
- in the use of fuel of proper quality;
- in timely cleaning of the chimney;
- in conducting a chimney as needed.
It is impossible to completely get rid of the condensate that accumulates on the chimney, but the set of measures presented in the article will help to significantly reduce the formation of excess moisture and extend the service life chimney.