An important attribute for the efficient operation of a solid fuel boiler and the creation of the required conditions for fuel combustion in it is a well-mounted chimney, otherwise the unit will not generate draft, which is necessary to remove combustion products.
The key criterion for the quality of the boiler chimney is excellent draft. It is estimated based on the speed of movement of flue gases through the chimney. The draft depends on the surface roughness, the height of the chimney, the internal section and the temperature difference between the ambient air and the combustion products. The chimney must be fireproof, resistant to high temperatures and equipped in accordance with fire safety regulations. Since the cross section for different boilers is not the same, the diameter of the chimney for a solid fuel boiler should be selected in accordance with the technical data sheet (instruction) provided by the equipment manufacturer.
Draft
So what is craving? Draft - a characteristic of the chimney, reflecting the speed of movement of flue gases in it. She appears ondue to the difference in temperatures (heat tends upwards) and pressure between the street (atmosphere) and the room in which the boiler is installed. It should also be clarified that in addition to a qualitative characteristic, thrust also has a quantitative one - this parameter is more influenced by the diameter of the chimney for a solid fuel boiler. At the same time, thrust itself is more dependent on the design (height, fresh air intake, turns, angles).
In absolutely all chimney systems, the draft is determined by several constant factors: the temperature of the wind, flue gases; difference between indoor and outdoor temperatures.
The warmer it is indoors and the colder it is outside, the better draft will be the chimneys for solid fuel boilers. This can be explained by the fact that the density of cold air is greater than that of warm air, which means that warm air has a lower pressure of the gas column. This factor ensures the occurrence of a pressure difference outside and inside the pipe. If the building is leaking, then at the foot of the building, due to the pressure difference, an air flow appears, which is directed inward. At the same time, warm air is forced out and exits through a hole at the top of the building, and cold air is inside due to holes inside the building. Natural air ventilation occurs.
It must be taken into account that the properties of smoke are not constant, since combustion in solid fuel boilers is uneven, respectively, the temperature of the flue gases varies in a fairly large range (in coal-fired boilers - 400-600 ˚С, and in wood-burning boilers 70-300WITH). The temperature of the smoke increases sharply when the boiler is ignited and decreases after the work begins to be carried out in the standard operating mode. This all also affects traction.
The length of the chimney also plays a significant role in draft. In other words, warm flue gases, when rising in straight sections, pick up a certain speed, and this ensures an increase in the flow of flue gases through the chimney. There is also a certain formula that proves the dependence of draft on the smoothness of the walls, the cross section and length of the chimney, the temperature both outdoors and indoors.
Chimney design
The next important nuance is the chimney device. The fewer narrowings, horizontal sections, turns, the better the traction will be. This is due to the fact that the gases from the boiler rise along the chimney in a spiral upwards, while at each of the bends the flue gases change their course of movement, their ordinary mixing takes place. At the same time, a chimney that has wall roughness, protrusions or bends creates resistance to the flue gas swirls formed in it.
Concluding from the above, we can say that the best option for a chimney will be round, cross-sectional, with smooth walls. If it is not possible to mount such a structure, it can be made rectangular, square or oval in shape, of the corresponding section. By the way, in the corners of the chimney, which has a rectangular shape, turbulences form, and this worsens the draft and contributes toaccumulation of soot in the chimney.
There are exceptions to the deadlift. For example, a temporary weakening of traction, reverse traction often occurs in the summer, when temperature indicators change on the street and in the house. There is also a capsizing or blowing thrust. An important role in these problems is played by the device of the chimney.
Anemometer is a special device for measuring thrust. It is digital and analog. It is usually used by inspectors of the relevant authorities. In everyday life, the method with the deviation of a sheet of paper is often used, but it does not provide accurate results, but simply indicates the presence or absence of traction as such.
Draft Quality Factors
It is possible to isolate several important facts that indicate the level of traction quality:
- humming and noise in the chimney - excessive draft: you should adjust the draft using the damper;
- smoke collects in the room after leaving the slots of the furnace - improper draft level: it is necessary to open the damper, increase the air flow to the room where the boiler is installed.
If the draft is too weak during the operation of the boiler, and the flame turns red, smoke swirls, the damper is not useful, you should focus on the following nuances:
- chimney height: check with an anemometer, best before activating the boiler;
- chimney section: check is performed by comparing the section of the chimney and the section of the exit from the solid fuel boiler;
- air flow into the room withheating equipment: it is necessary to check whether the air vents are clogged, whether the grates are clogged with dust;
soot: the question of its presence is ambiguous, it all depends on the design of the boiler and the type of fuel, but in any case, inspection holes should be checked before the start of the season.
Types of smoke channels
Chimneys must be made only from high-quality and fireproof materials.
The following types of chimneys are distinguished:
- brick;
- metal;
- ceramic;
- glass.
Brick chimneys
This material for laying the smoke channel has been used for a very long time. Brick chimneys for solid fuel boilers can be connected to boilers at a given height and allow you to go around small obstacles. However, there is one drawback: the classic scheme of a chimney made of this material suggests that it will have too much weight and dimensions, and this will require a lot of effort. It should also be taken into account that the brick cannot withstand temperatures over 500 ° C.
Complete arrangement of a brick chimney, having a length of 10 m and a width of 140 mm, with an asbestos-cement insert is from 23,300 rubles.
Metal chimneys
Such chimneys for solid fuel boilers are made of stainless and black steel. Black steel structures are unstable to aggressive environments, so it is undesirable to use them. With continuous operation of the boiler, a similar pipe forchimney, the price of which is relatively low, will very quickly become unusable and fire hazardous for your home.
The cost of pipes depends on the grade of steel used to make them. So, 1 m of a pipe made of the most inexpensive corrosion-resistant steel with a diameter of 115 mm has a price of 400 rubles. A similar pipe made of AISI 439 steel with the addition of titanium costs from 800 rubles/m.
Ceramic chimneys for solid fuel boilers
Great choice for solid fuel boiler. Ceramic chimneys have the following properties:
- not afraid of condensation;
- have high fire resistance (the maximum allowable flue gas temperature is 1200 °C);
- resistant to mechanical stress;
- weather resistant.
Glass chimneys
Such chimneys are quite rare, they are characterized by low thermal inertia, rather extravagant appearance and complete absence of corrosion. A similar chimney pipe, the price of which is quite high, is not available to everyone. It is necessary to take into account not only the high cost of the material, but also the high cost of installing this chimney.
