Home Article How to choose a boiler for solid fuel

How to choose a boiler for solid fuel

tips for choosing a solid fuel boiler for a private home

Access to electricity and gas is not everywhere, and warm somehow need. Installation of a solid fuel boiler will be a great solution. Not only does it allow you to create a fully self-contained heating system, but it’s also very economical to operate. Solid fuel boilers are used as a primary and backup source of heat, and for obtaining thermal energy burn wood, sawdust, coal or pellets. These are quite bulky units, and the fuel has to be added regularly, but the low cost of the resulting energy allows solid fuel boilers still compete with the more modern gas and electric. Let’s figure out what solid fuel boiler is best to choose for a private house, let’s determine the capacity, type of heat exchanger and other nuances.

It would seem that what is complicated in a solid fuel boiler? Throw wood or coal in the furnace, they burn, heat water, and the house is filled with heat. In general, everything is so, but the principle of operation of the device is a little more complicated. In the design of modern solid fuel boilers you can distinguish such basic elements:

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  • furnace;
  • The system of circulation of the coolant;
  • Smoke removal system;
  • security system;
  • heat accumulation system.

Fuel is fed into the furnace and burned to produce heat. This is in the classic version. There are pyrolysis boilers, in which solid fuel (firewood) smolders, releasing gas, which then burns, providing heat. The efficiency in this case increases slightly, but the features of the classic and pyrolytic boilers will be discussed later.

The furnace is a large container with double walls, between which there is the coolant. This is in most cases water, less often non-freezing liquid or a mixture of water and antifreeze is used. The coolant receives heat from the burned fuel, circulates through pipes and radiators, heating the air in the house. When the water cools down, it goes back to the boiler and everything repeats. Often special pumps are used to improve the circulation.

When burning fuel, not only heat is generated, but also gases that must be removed. A smoke evacuation system is designed for this purpose. Chimney carries gases from the boiler to the outside, sometimes a forced ventilation system is used to increase the efficiency of this process.

The greatest danger that can happen during operation of the solid fuel boiler is overheating of the coolant. The water can already be sufficiently heated, and the boiler will continue to produce heat. If the water comes to a boil, the heating system may not hold, especially if the house has quite sensitive to high temperatures metal-plastic pipes. To stop the combustion of wood or coal is almost impossible. you can only reduce the intensity, and to prevent overheated coolant in the system, use a cooling heat exchanger. It receives cold water from the water supply, but it is always better to have a sufficient supply of it in case of water outage.

The cooling exchanger can be built into the boiler or located between the boiler and the rest of the heating system. It can only be built into the structure of a steel boiler. It works in one of two possible ways:

  • The first option. cooling the heated coolant, which passes through a cooling heat exchanger. Cold water in the cooling exchanger is fed through a thermo valve, which opens when the coolant temperature reaches 95 0 C. The process lasts until the coolant cools down to a safe temperature;
  • The second option provides for a shut-off valve.If the water temperature rises to critical values, the valve prevents it from flowing into the pipes. Cold water from the water supply is fed into the heating system, and the superheated coolant is discharged into the sewer. However, the water pressure must be sufficient, and in its composition there should not be an increased amount of salts, which will provoke the formation of scale.

To drain the heated water into the drain. is not very smart and economical, so the design of the solid fuel boiler is better to complement the tank-accumulator. This is a buffer between the boiler and the rest of the heating system, through which a number of important functions are realized:

  • accumulation of warm water for its further use, which is a fuel economy, comfort, stability in maintaining the temperature and reducing the number of trips to the furnace for tossing fuel;
  • protection against accidents. In the tank overheated water is mixed with warm water;
  • Possibility to use boilers of different types. Storage tank will be common to solid fuel and, for example, gas or electric boiler, will simply organize a unified system of heat supply at home and to insure a few sources of heat.

Heat accumulators are made of cast iron or steel, get a powerful thermal insulation. The volume of the buffer, first of all, depends on the power of the boiler: for every 1 kW you need to provide 25 liters of tank volume. The quality of this element of the heating system should be the highest, so it is better to trust the products of well-known manufacturers. In the online store https://www.duim24.In addition, the range includes tanks of different volumes and materials.

Advantages and disadvantages of solid fuel boilers

In order to make a decision in favor of choosing the type of solid fuel heating boiler, it is desirable to consider all the options that this equipment offers. For this it is best to get acquainted with the advantages and disadvantages associated with the operation of this technique.

All boilers of such type are characterized by the following positive qualities:

  • economy of use. with the same capacity of the unit, the cost of fuel for solid fuel boiler long combustion will be twice cheaper than for a gas boiler and three times cheaper than for an electric boiler;
  • simple design. allows you to install the equipment without the involvement of qualified specialists, and also serves as a guarantee of reliability;
  • The device assumes the use of different types of fuel, which allows the user to save a lot of money;
  • Independence. allows using this type of equipment in conditions remote from the boons of civilization;
  • Compared with gas or electric heating boilers, solid fuel units have a reasonable cost;
  • a large variety of designs allows you to choose the installation that meets all the personal requirements of the consumer.

However, with many advantages of solid fuel boilers for long combustion, they have disadvantages that do not allow their use in all (without exception) cases.

Why choose solid fuel Boiler BRICK. Advice to a Friend.

Among the disadvantages can be noted the following:

  • additional space must be allocated for fuel storage;
  • For the effective use of the unit it is important to follow a number of certain rules;
  • manual loading of fuel, the frequency of which depends on the model of the boiler;
  • budget units have additional difficulties in operation, not having automatic control;
  • Most of the units of long combustion efficiency does not exceed 70%.

Advantages and disadvantages of boilers of this type are determined by a number of factors: the area of the heated room, the presence of various communications, the degree of resistance of thermal insulation. For this reason the equipment should be chosen according to the local conditions.

The rules of choice

Choose a solid fuel boiler takes into account several important parameters: the available fuel, mode of operation, boiler capacity and heat supply scheme.

Also take into account the type of load, whether only heating load or in addition will be needed to prepare hot water. They also determine the possibility of the unit to work without electricity and take into account the existing systems of flue gas discharge and coolant flow on the heating circuit inside the house.


Even the simplest solid fuel boilers can operate on different types of solid fuels from coal to pellets. The most modern boilers provide the possibility of operating the unit on liquid and gaseous fuels by installing a special burner in the combustion chamber door. This allows the owner to use the fuel available in the area of residence.

Russian manufacturers use the practice of installation of electric heaters in solid fuel boilers, to maintain the heating mode in the absence of primary fuel.

It should be noted that the boiler on an auxiliary fuel will work with a lower efficiency, so you need to choose the boiler, taking into account the main fuel and the possibility of an uninterrupted supply of necessary energy carrier.

Heat exchanger material

All boilers are produced with two types of heat exchangers, made of cast iron and steel. The first are the most expensive and heavyweight, with a lifetime of at least twice as long as steel. 20 years.

They operate well in high temperature environments and provide good heat transfer from the flue gases to the heating medium. Cast iron heat exchangers are made of demountable sections that make them easy to replace during repairs.

It should be noted that cast iron heat exchangers have a number of disadvantages, including the high fragility of the product. Destruction can occur when there is a water hammer in the heating system during start-up or when cold water hits the red-hot cast iron.

Steel heat exchangers are almost always performed in a monoconstruction with the boiler, they are not demountable. Despite the fact that the steel metal is more plastic and is not afraid of water hammer, it is highly susceptible to corrosion, especially in the area of welds.

Such devices are not durable, work no more than 10 years, and at failure. you need to replace the heating unit completely.

Energy consumption

Boiler units that work on solid fuel are divided into 2 groups:

Energy-independent, which operate only with the presence of voltage in the network. Typically, these are systems with forced air and circulation of the heating coolant through the heating circuit using an electric circulating pump.

Of course, the first option is the most preferred and is used in all modern boilers with high efficiency and level of automation of thermal processes.

Solid fuel boiler: how to choose

Boiler room with solid fuel boiler

An important advantage of such boilers is sometimes their energy-independent, when in the construction there are no devices requiring electrical power supply, even thermostatic controls are mechanical. Most often this applies to domestic manufacturers, who know firsthand about power outages in the countryside and take this fact into account in the schemes of boilers. However, do not forget that modern heating systems, even with a solid fuel boiler as a heat source, are more stable in the presence of a circulating pump, and it does not work without power, alas. So it is still recommended to get a backup power station in case of power problems, but often the solid fuel boiler is excluded from the list of energy consuming devices.

Material of the heat exchanger of a solid fuel boiler: cast iron or steel

Cast iron boilers

Cast iron solid fuel boiler

Solid fuel boilers are associated with something bulky and heavy, because its heat exchanger is often made of cast iron. Boiler manufacturers use this material for its durability, high corrosion resistance (wear of cast iron heat exchanger in the normal mode is 0,1-0,2 mm per year, so at a wall thickness of 5 mm it will last for twenty years), resistance to high temperatures (when burning coal only cast iron heat exchanger can sustain a burning temperature of 900 degrees C), for it is not characterized by temperature deformation.

The disadvantages of boilers with cast iron heat exchangers are their heavy weight, which hinders transport, during which the equipment must not be dropped or hit. Cast iron is brittle and cracks on sharp impact. Cracks will also appear if cold water is spilled on the hot exchanger or if the boiler is fed with too cold water. The difference in temperature between the flow and return flow temperatures of over 50 degrees Celsius can be fatal for cast iron heat exchangers, even if micro cracks are not initially visually visible. Some modern products of eutectic (ductile) cast iron successfully operates at a low temperature at the boiler inlet, it is 30% more ductile than conventional grey cast iron, which enables the operation of the boiler in low-temperature operation.

Another solution for low-temperature operation of solid fuel boilers can be the use of a buffer tank in the scheme of the boiler room.

On the other hand cast iron heat exchangers consist of sections and are therefore repairable. Sections are replaced, fastened with screws with heat-resistant gasket and sealant. Thanks to the sectional nature, the cast iron boiler can “grow” along with the house. For example, when you add a large workshop or conservatory to the house, you can not buy an additional boiler, but only add internal sections, thereby increasing the power of the boiler to the necessary.

Calculation of the capacity of the domestic boiler is based on the formula “1 kW per 10 m² heated area”, ie for a house of 200 square meters will need a boiler capacity of 20 kW.

Steel boilers

Steel solid fuel boiler

Boilers with steel heat exchangers are similarly sized, but their designs are more diverse and they are usually cheaper, which makes them a frequent source of heat in solid fuel boilers.

The lightness of steel heat exchanger and its welded construction are both advantages and disadvantages in solid fuel boilers. It is easier to transport and unload. It is easier, but the temperature extremes of such a boiler tolerates worse, overheating can deform the heat exchanger, welds. Leak, and sometimes the wall of the heat exchanger can burn through.

Most often such situations occur in case of emergency power failure and in systems with forced circulation. In this case, the boiler continues to heat, and the circulation pump does not rotate, does not remove heat from the boiler and overheating occurs. Uninterruptible power supplies help, but in 50% of cases do not work, it is best if there is an automatic switch to a diesel power plant. The most effective way to protect the solid fuel boiler from overheating in case of power grid breakdown is a short circuit with gravity circulation, that is a section of large diameter pipes, where the boiler heated coolant will be during the breakdown.

How to choose a solid fuel boiler

Equipment for heating must be reliable, economical, able to maintain an optimal microclimate. The equipment that meets these requirements are offered by domestic and foreign companies. Which solid fuel boiler is better for a private house, and which can only cope with the heating of a small cottage. depends on a number of parameters that are taken into account when selecting the model.

Thermal capacity

You can buy a small inexpensive boiler, but it is necessary to take into account the power of the equipment. Producers necessarily indicate this characteristic in the technical documentation. The maximum area of the heated space depends on the thermal capacity. These parameters are in direct dependence: for 1 kW should not be more than 10 sq.m.м. rooms with 2.7 m high ceilings. For heating a small house of 60-70 square meters.м. A boiler with a thermal capacity of 6-7 kW is enough.

Pre-calculation is relevant for small buildings. accurate parameters should take into account the caloric content of fuel used, the number of radiators installed, the presence of a boiler and its volume. Detailed calculation of the thermal capacity is recommended to order from the heating engineer. This helps to get rid of problems during severe frosts or when using low-calorie fuel.


The ratio of the consumed fuel to the amount of usable heat is called efficiency. There is no equipment with 100% indicators, heat losses occur from unburned emitted gases, as evidenced by the appearance of soot. Part of the heat energy escapes through the pipe, the other. is spent on heating the walls and heat exchange with the air of the room where the equipment is installed. Reduces the efficiency of raw fuel, improper air supply.

The maximum efficiency of pyrolytic-type models, to make it higher allows not only the high combustion temperature of gases, but also the complete burning of fuel. Manufacturers increase efficiency by installing a combined thermal insulation, part of which becomes a water jacket. the energy is spent not on heating air, but on increasing the temperature of water. The higher the efficiency. the more cost-effective heating system.

Type of fuel

It is recommended to buy a boiler that operates on an available type of fuel. Automated pellet models attract functionality, but in the absence of access to pellets can be left in a cold house. Universal models work on coal and wood. Coal burns longer, which allows you to spend less time on service. Wood is a more affordable fuel.

When choosing a model that works on wood, you should consider the recommended size of logs, the ability to effectively burn raw fuel. Pyrolysis boilers function on dry wood. If there is no possibility of storing fuel in a room with normal humidity, then such equipment must be abandoned.

The material of the heat exchanger

Manufacturers produce models with steel and cast iron heat exchangers. Heat exchangers made of refractory steel have low inertia, are easy to maintain, lightweight and resistant to mechanical damage. Steel can be used to make a design of any complexity and to improve performance parameters. Disadvantages. short life, risk of burning and low resistance to corrosion.

Cast iron sectional heat exchangers are resistant to corrosion, acids, high temperatures. Good heat transfer allows the use of small sections. Cast iron is a fragile material, not resistant to sudden changes in temperature. Heat exchangers have a large weight and low efficiency.

Number of heating circuits

Models with one water circuit are designed only for heating. Two-circuit boiler will provide heat and hot water. These models are more expensive, so if necessary, it is better to use equipment with the possibility of connecting a boiler. It is not always comfortable to heat in summer, in this situation the electric solid fuel boiler with a heating element will help, it will maintain the desired temperature in the hot water system.

Teplodar Carbo 26

Universal shaft boiler designed to work with coal (guarantees combustion for up to 16 hours), but as an alternative it is possible to use wood and any kind of fuel briquettes. It is possible to install a flare pellet or gas burner.

  • Fuel: Coal (preferred), wood, briquettes (toja, wood, coal) electricity.
  • Heating area: 190-260 m2 ;
  • Volume of the furnace: 50 l;
  • Number of circuits: 1;
  • Chimney: 115 mm in diameter;
  • Working pressure 2 atm;
  • Weight: 180 kg;
  • Production: Russia.

Shaft design guarantees maximum heat extraction, high efficiency, no freezing of fuel.

The system of protection against pyrolysis gas ignition.

The built in block of heating elements helps to keep the boiler from cooling down after the burning out of the main fuel.

The furnace is easy to clean thanks to its special design and conveniently located hatch.

❌ Difficult installation, separate airing room in the house is required.

Zota Carbon 15

Reliable steel heating boiler of Russian brand with a loading hatch from the top. This model is famous for its high safety and efficiency. It is equipped with temperature and pressure control systems, air supply regulating mechanisms and draught regulator.

  • Fuel: coal fraction, coal briquettes;
  • Heating area: 100 m 2 ;
  • Furnace volume: 22 liters;
  • Power output: 15 kW;
  • Number of circuits: 1;
  • Chimney: diameter 115 mm;
  • Working pressure: up to 3 atm;
  • Weight: 184 kg;
  • Production: Russia.

Ability to regulate the air flow into the furnace;

Only suitable for coal of certain sizes.

❌ Special skills are required to put the parts back in place after cleaning.

Buderus Logano S 131

Steel energy-independent boiler for residential premises. German manufacturer has provided for this model to be installed both individually and in already installed heating system. Suitable for residential house, warehouse or production hall.

  • Fuel: coal, wood.
  • Heating area: up to 200 m 2 ;
  • Furnace volume: 45 liters;
  • Power: 15 kW;
  • Number of heating circuits: 1;
  • Chimney: Ø 115 mm;
  • Working pressure: 2 bar;
  • Weight: 115 kg;
  • Production: Germany.

Easy to load fuel and clean thanks to the front door;

High efficiency. the manufacturer claims up to 65%.

❌ Resin may be deposited on the walls of the hopper from logs;

❌ Preferably installed in a room with a separate entrance.

  • coal, Montenegrin coal, Balahta coal and Borodino brown coal, when buying coal you should pay attention to its fraction and grade, they must meet the technical conditions of the boiler operation;
  • Firewood, birch, pine, other types of wood, you can buy immediately chopped, the secret of choice is simple. the less moisture content of wood, the better, especially when it comes to pyrolysis, gas generator boilers, wet firewood such boiler will kill in three seasons maximum, so the place for storage should be protected from moisture and precipitation, the humidity of wood for gas generator boiler no more than 20%, wet wood can be used in classic, traditional boilers, but not advisable.

The third common option. pellets, on which pellet boilers function. These are pellets, which are produced from wood waste, waste from various areas of agriculture. Choose the right pellets. a whole science, it is important and the color, shape and structure. Pellets are probably one of the best types of solid fuel, if it were not for one problem. price and availability on the market. Pellet boilers and pellets are more expensive than wood and coal, but cheaper than gas and electricity. It should be understood that such solid fuel heating systems for the future. There are more and more new producers on the market, the supply is growing, and therefore there are no problems with where to buy and the cost of fuel is falling. Pellet boilers can be automatic and semi-automatic, differ in type of burner (flare, volumetric combustion, fireplace). Advantages. easy maintenance, very high performance (efficiency). Disadvantages. the high cost of heating equipment and fuel. Boilers on solid fuel can operate on the wastes of various spheres of agriculture, woodworking industry. For example, SEG Bio boilers of the Polish company “Metal Fach” can be loaded with corn. The main advantage of such boilers is the low cost of fuel. Also note the fuel briquettes from toa, oil shale, there are other options.

  • Solid fuel heating boilers for private houses (up to 100 kW);
  • Industrial solid fuel boilers for continuous combustion (capacity over 100 kW).

Solid fuel boilers: How to choose the right one?

In regions where the cost of electricity is high, and natural gas is either unavailable or very expensive, an excellent solution for the installation of heating systems are solid fuel boilers. And it is important to choose the best, ideal variant. The qualified and experienced heating engineers of Kras-Kotel will help you with this. When choosing a heater yourself, you should pay attention to a number of key points.



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