Currently, more and more owners of private houses, cottages are trying to achieve independence from sources of central energy supply. If with electricity this issue is not relevant and problematic due to technical complexity, then with the heating of residential buildings the situation is much simpler. Autonomous gas heating is popular among residents of the private sector, however, in those conditions where there is no centralized gas supply, solid fuel boilers come to the fore.

Heating devices of this type are experiencing a rebirth today. Stoves and fireplaces familiar to all of us, used in the old days for heating residential buildings, are now giving way to high-tech boiler equipment.

The scheme of a heating boiler, the device of a solid fuel boiler in its current form allow us to understand not only the principle of operation of heating devices of this type, but also to appreciate the enormous possibilities of such equipment. The principle of operation of solid fuel boilers is in many ways a key aspect that the consumer pays attention to today. In order to use the autonomous heating system with maximum benefit, you should understand two points:

  • what elements and parts does a solid fuel boiler consist of;
  • what is the basic scheme of operation of a solid fuel boiler.

See also: the principle of operation of a gas boiler.

Operation of solid fuel boilers. New opportunities

Unlike gas and electric heating, using a home heating system with a solid fuel boiler requires great physical effort and appropriate technical training from homeowners. Having significant technical and domestic limitations, solid fuel boilers have one indisputable advantage in comparison with gas heaters, not to mention electricity. A solid fuel heating boiler is 80-90% energy-independent device. A sufficient supply of fossil fuels, firewood or pellets will allow you to not only heat your own house calmly all winter, but also provide yourself with hot water.

The heating system connected to a solid fuel boiler does not depend much on power outages. She is not afraid of drops in working pressure in the gas line. The cost of fuel and the availability of free access to it will ensure the normal and uninterrupted operation of all heating equipment in the house. Management of solid fuel boilers allows you to operate the units in any operating mode, thereby ensuring the safety and comfort of the inhabitants of a residential building.

Domestic manufacturers, foreign companies specializing in the production of boiler equipment today offer the consumer a qualitatively new product. Solid fuel boilers that are used for domestic and industrial purposes have a higher efficiency. Today this parameter reaches 90%.

For reference: old solid fuel boilers in the traditional design had an efficiency of 70-80%. The low energy efficiency of old-generation heating equipment led to significant fuel overruns and significant losses of thermal energy.


Design innovations and «know-how» in the field of practical application of various energy resources have made it possible to significantly expand the operational capabilities of heating equipment. Huge power is one of the main advantages of solid fuel boilers. The profitability of modern models of solid fuel boilers has increased by an order of magnitude. The safety of operation of this type of boiler equipment has significantly increased.

A double-circuit solid fuel boiler is able to provide heating for large and spacious rooms. In addition, almost all models of boilers are designed to provide domestic hot water facilities.

Design features of solid fuel boilers

A traditional solid fuel boiler is, in our understanding, a heating unit capable of operating on any solid fuel. The principle of operation of the boiler is elementary. The fuel entering the combustion chamber during the combustion process releases a large amount of thermal energy, which heats the coolant. According to a similar principle, stove heating was organized in the old days, only hot air was used instead of a liquid heat carrier.

A significant disadvantage of the traditional model of a solid fuel boiler is that part of the heat generated by the combustion of fuel simply escapes into the atmosphere through the chimney. Consider a schematic diagram of a solid fuel boiler. The boiler device is a structure assembled from various modules into a single steel case. The main structural elements of this type of heating equipment are:

  • combustion chamber (furnace equipped with a door);
  • heat exchanger (steel or cast iron);
  • cleaning hatch;
  • grate (lattice);
  • thermostats;
  • safety valve.

The traditional solid fuel boiler of the new generation shown in the figure is equipped with all the devices, mechanisms and elements necessary for normal operation.

The combustion chamber — the processes occurring in it

One of the first elements that you have to get acquainted with first of all is the boiler furnace. It is the ships that lay coal, peat, briquettes or firewood, and it is here that the main process takes place — fuel combustion. The whole process can be divided into three stages, fuel drying, oxidation and production of a combustible gaseous substance, which already performs the main heating function in the combustion process.

In the combustion chamber, the loaded fuel is evenly distributed on the grate, which is specially installed at an angle.

The fuel located on the grate is dried by hot gases, after which the process of fuel combustion with forced air supply already begins. At the end, the gaseous combustible mixture obtained at the initial stage of combustion is afterburned in the furnace at a temperature of 950-10000 C. An uninterrupted air supply must be ensured at each stage.
Solid fuel residues, ash and soot accumulate in the ash chamber, from where it is removed manually.

For reference: it should be noted that the efficiency of the boiler depends on how densely the combustion chamber is loaded with fuel and how the hood works. When the combustion chamber is fully loaded and the air supply is normal, the fuel should burn completely, releasing the maximum number of kilocalories during the combustion process. The ratio of useful supply to boiler power is a key point during the operation of a solid fuel boiler.

The processes occurring in the combustion chamber also determine the type of boiler equipment. Combustion can be carried out in the usual way, thanks to pyrolysis, or for a long time, from top to bottom. In each case, a certain thermal effect is achieved, which determines the scope of the solid fuel boiler, how the heating of the house is organized.

Heat exchanger — its function

The next most important structural element of a solid fuel boiler is a heat exchanger. The device is a cast-iron or steel structure in which thermal energy is transferred from combustion products to the coolant. In the traditional version, the heat exchanger is made in the form of a barrel, through which seamless boiler pipes pass. The heated gases, passing through the pipes, heat the boiler water circulating inside the heat exchanger circuit.

Important! The intensity of the passage of gases through the smoke pipes is regulated by the position of the smoke exhauster. The intensity of water circulation in the heat exchanger depends on the operation of the pumping station. Heat exchangers necessarily have a thick layer of thermal insulation that protects the main body of the boiler from overheating.


The flow of water into the heat exchanger occurs through the intake manifold, while the exit of the heated coolant, on the contrary, is carried out through the exhaust manifold. On each of the collectors there are coolant temperature sensors. Home heating in a house with a solid fuel boiler, the connection diagram of which is not much different from the traditional and generally accepted procedure, may have some design differences in each situation.

Steel heat exchangers, unlike cast iron products, are more susceptible to corrosion, at the same time they successfully cope with temperature extremes. The cost of such devices is much less in comparison with cast iron heat exchangers. The latter have a high heat capacity and are less susceptible to corrosion.

Design varieties of systems

If we do not consider the traditionally used stove heating, there are not so many types of solid fuel boilers that exist today. The main difference between the existing models of boilers is the way the fuel is supplied. Cheap units are designed for manual fuel supply. In expensive models, for the operation of a solid fuel boiler, automatic fuel supply to the combustion chamber is used.

The method of fuel supply mainly determines the principle of operation of the boiler. Coal, briquettes or firewood are loaded into the firebox and set on fire. The water heated to the required temperature in the coolant diverges through the pipes, heating the living quarters.

On a note: however, there is one but! The fuel burns out quickly and it is necessary to load the boiler with fuel raw materials again. The time required for complete combustion of the fuel is limited to 2-8 hours, depending on the model of the boiler and its power. In addition, it is necessary to simultaneously remove ash from the combustion chamber, the remnants of unburned fuel. For the normal operation of the boiler, it is constantly required to throw more and more portions of fuel into the furnace.

Automatic fuel supply solved the problem with the operation of solid fuel boilers by half. A fundamental technical solution was required. For heating with a solid fuel boiler, the best way out of this situation was the possibility of using heat generators, which are also called long-burning solid fuel boilers.

In practice, this type of heating equipment is usually divided into two types:

The method of loading in the equipment of these types remained fundamentally the same, only it became longer in time and more laborious. As compensation for the efforts spent, during operation, the boiler creates the maximum possible thermal effect. Despite the difficulty and complexity of loading, in these models there is an almost complete combustion of fuel, which significantly reduces the number of loads and fuel consumption.

For pyrolysis boilers, the work process is as follows. In the absence of oxygen, the combustion process in the chamber slows down. The fuel burns out completely, and the coke oven gas obtained as a result of smoldering is a secondary fuel. The oxygen-enriched gaseous substance in the combustion process releases additional calories of thermal energy. There is a high efficiency, profitability and efficiency of the equipment during operation.

Recently, heating of residential buildings with solid fuel boilers of upper combustion has become widespread. Fundamentally, the scheme of work looks a little different in comparison with traditional models. Here, the flame spreads from above, and not from below, as we are usually used to seeing. The combustion of fuel occurs gradually, from top to bottom. At a time when the top layer of fuel is subject to intense combustion, the lower layers remain untouched. As each layer of fuel burns, air, along with combustible gases, descends. This process can take a very long time, in some models the burning time of one bookmark can be 8-12 hours.

On a note: some models of solid fuel boilers of upper combustion in the supporting mode of operation can provide heat from one load for a day or more.

Other important structural elements — their role in the operation of the entire heating system


The scheme of any solid fuel boiler is inconceivable without a draft regulator. This device provides a mechanical effect on the damper in the chimney in the process of turning on or off the unit. You can show the operation of the draft regulator using a simple drawing.

Thanks to the operation of this device, the air supply to the combustion chamber and the heating temperature of the coolant are automatically adjusted.


For reference: The regulator is set at the first start-up of the boiler, setting the position in accordance with the set parameters. In a semi-closed position at a temperature of 650C, in the open position of the damper, the regulator corresponds to a maximum temperature value of 900 FROM.

Many units, especially large ones, are installed together with a buffer tank, which is mandatory when tying solid fuel equipment with gas boilers into a single system. Such a device is an expansion tank, where the coolant enters. The buffer tank in this case performs two functions, a hydraulic separator and a heat accumulator. As a result of the boiler cooling after shutdown, water from the heat accumulator diverges through the heating radiators, maintaining the required temperature. Rapid cooling of a solid fuel boiler is almost impossible, due to the fact that the buffer capacity plays the role of a heat accumulator.

Together with the buffer tank, the boilers are equipped with a thermostatic valve. The device is used to protect the system from overheating. The cooling circuit, equipped with a thermostatic valve, will ensure the supply of cold water inside at the first signals of overheating of the coolant.

For ignition in solid fuel boilers of modern models, various gas burners are used. Such devices usually run on liquefied gas, which is stored in a special tank. Ignition of fuel in the combustion chamber due to the use of a gas burner occurs in a matter of seconds. In operation and maintenance, such burners are simple and reliable.


Having familiarized yourself with the device and scheme of a solid fuel boiler, having learned the principle of operation of some types of solid fuel boiler equipment, you can safely proceed to create your own autonomous heating system in your own house. Choosing a boiler is not particularly difficult. The main burden and difficulties that will have to be faced in the future are the installation of equipment, connection and preparation for launch.

A competent and qualified approach at each stage will allow you to achieve the desired result.


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