Features and main functions of chimneys for solid fuel boilers

It seems to many of us that everything can be done quickly, especially without going into technical details and nuances. You can build a house, install a stove, a fireplace or an autonomous solid fuel boiler in it, live the communications of the heating and air conditioning system. At first glance, everything, but you should never forget about the chimney. For a private residential building, a chimney is the same mandatory attribute as a ridge on the roof. Let’s try to figure out how to properly equip chimneys for solid fuel boilers, which type of chimney is better, brick or metal.

The main function of the chimney

As is known from the school course of physics and chemistry, oxygen is necessary for combustion. The more oxygen, the more intense the combustion. Any source of open fire can be easily extinguished if air access to it is stopped. Here it would be appropriate to point out that due to the influx of air, thrust also arises. If you balance these two parameters, any fuel will burn evenly and for a long time.

If an ordinary fire gives off heat and the smoke from it quietly spreads in space, then in the house the situation looks completely different. As a result of combustion, volatile compounds (flue gases) are formed, which are drawn out through the chimney. A good chimney is half the battle. The efficiency and productivity of heating boiler equipment depends on how the chimney is installed, what is the diameter and cross section of the chimney for a solid fuel boiler.

Together with the smoke, the smallest volatile particles of soot, ash and soot escape to the outside through the hood. In a round chimney, the accumulation of soot and soot on the walls is minimal, in contrast to rectangular chimneys.

On a note: if the chimney is not made correctly, all the soot, soot and ash will remain in the chimney, clogging it and reducing the clearance.

Important! The chimney must be made of heat-resistant and refractory materials. The chimney is mounted in strict accordance with the existing fire safety rules and the operation of boiler equipment.

*

What is traction

The main condition that you need to focus on when evaluating the operation of the chimney in the house is the state of draft. If the draft is good, then combustion products are easily and quickly removed through the pipe, the fuel burns out better, giving off maximum thermal energy. Thrust occurs as a result of the temperature difference, inside and outside. Heat, as you know, moves upwards, respectively, flue gases tend to find a way out. The draft depends on the section of the chimney, the configuration of the chimney and the structure itself. Here it is important to take into account the number of bends, turns in the chimney, as well as the presence of ventilation. In straight sections, volatile combustion products pick up speed, increasing the intensity and power of the flow. The fewer bends and turns in the pipe, the better. The smoke rises in a spiral and any change in the direction of movement leads to a decrease in the speed of passage.

On a note: when calculating the chimney, one should take into account the physical properties of flue gases that are released during the operation of solid fuel boilers. The temperature of the smoke is also different. For coal-fired units, the flue gas temperature is 400-600 ⁰C. Smoke in wood-fired boilers has a temperature of only 80-300⁰C. Accordingly, the thrust in each individual case is different.

The quality of traction can be assessed during the operation of a solid fuel unit by the following factors:

• there is noise and buzzing in the chimney, therefore, the draft is excessive;
• if the flame is red, the draft is weak and insufficient;
• flue gases begin to flow from the boiler furnace into the room, which means there is a reverse draft.

If, with appropriate manipulations with the gate, it was not possible to eliminate the above factors, you need to pay attention to the design of the chimney. The main aspect is the correspondence of the cross section of the boiler outlet with the cross section of the chimney. Next, it is checked whether the height of the chimney is sufficient. The operation of the draft is affected by the volume of fresh air entering the boiler, so you need to check the ventilation in the house.

For reference: the height of the chimney for a solid fuel boiler is checked with an anemometer even before starting the boiler equipment.

Chimney structure. What materials are used for these purposes

To date, there are three types of chimneys used for household solid fuel boilers. These are the following structures:

• metal hood;
• brick chimney;
• ceramic channel.

The first option — a metal pipe is the easiest and cheapest way. It should be remembered that only heat-resistant steel is used for this purpose, capable of withstanding high temperatures (up to 800⁰FROM).

*
A brick chimney for solid fuel boilers is the most traditional. In the classical view, the chimney is always made of refractory bricks. However, this option has its technological difficulties and nuances. For the equipment of a capital brick hood, a significant reconstruction of a residential building will be required. Brick chimneys for solid fuel boilers are usually equipped with smoke exhausters. With the help of such a device, a zone of rarefied air is created in the smoke channel, where hot combustion products rush.

The last, third option involves the installation of a ceramic pipe that can withstand temperatures up to 1000⁰C. As a rule, pyrolysis boilers are equipped with a ceramic exhaust duct, the operating temperature of which reaches similar values.

For reference: ceramic and brick structures have significant physical weight, so it is often necessary to strengthen the foundation of a building or create a hotel site for a chimney.

The design of the chimney may differ depending on the design features of the residential building, the power of the heating device. Installation and installation of the hood is carried out in the manner prescribed by the rules and regulations of fire safety. You can choose the optimal cross section and determine the height of the chimney using the technical documentation provided by the manufacturers of boiler equipment. When installing a chimney in your home, you should remember:

• the length of horizontally located sections should not exceed 1 m;
• the length of the smoke channel should not be more than 5 meters
• the height of the pipe should be no more than 1 meter from the roof cut.

Important! The design of the smoke channel must be adapted for the removal of condensate, convenient when cleaning the hood from soot and soot.

Chimney installation

Pipe installation begins with the assembly of individual elements into a single channel. All joints are treated with a heat-resistant sealant to avoid leakage of flue gases from the main flue channel. The whole system can be equipped both inside the building and outside.

If you have a duct with a different diameter than the boiler outlet, purchase an adapter. The next rule to consider is that single-walled, insulated chimneys are installed according to the “pipe to pipe” principle. All existing tees are mounted on the basis of the “smoke” principle, and vertical channels are “condensed”.

The installation process can be divided into the following steps:

• all elements of a single system are assembled from the bottom up;
• clamps are used to fasten individual elements;
• all connection points must be in accessible places;
• fastening on the wall must be done in such a way that there would be no deflection of the main channel;
• proximity to other power supply communications is prohibited;
• the joints should not be in the thickness of the layer of the roofing cake;
• if there are combustible materials in the roof, a spark catcher is installed on the chimney.

To upgrade the existing hood in the house, after installing newer heating equipment, special devices are used — fans. Smoke exhausters for solid fuel boilers is an excellent option to significantly increase traction. With insufficient natural draft, with the help of a smoke exhauster, the desired effect is achieved.

conclusions

Which chimney is better, steel or brick, is up to you to decide on the spot. Here it is important to take into account not only the economic factor, but also to focus more on the quality of work. According to experts, for capital residential buildings, brick exhaust ducts are the best solution. For summer cottages and country houses, you can get by with a steel chimney, which is accordingly easier to install and maintain.