Heating equipment that runs on solid fuel is represented today by a whole group of devices. Every solid fuel boiler produced today by domestic and foreign manufacturing companies is a completely new, high-tech heating device. Thanks to the introduction of technical innovations and automatic control devices into the design of heating devices, it was possible to significantly increase efficiency and optimize the operation of solid fuel boilers.
Heating devices of this type use a traditional principle of operation, similar to the well-known version of stove heating. The main action is due to the process of generating thermal energy released during the combustion of coal, coke, firewood and other fuel resources in the boiler furnace, followed by heat transfer to the coolant.
Like other devices that provide energy generation and transmission, boiler equipment has its own efficiency factor. Let us consider in more detail what the efficiency of units operating on solid fuel is. We will try to find answers to questions related to these parameters.
Which solid fuel boiler is better to buy?
There are many different types of solid fuel boilers on the modern market. Each type of equipment has its own technical characteristics and efficiency. To facilitate the process of choosing a solid fuel boiler, you need to have a clear understanding of each type of this equipment.
Natural combustion solid fuel boilers
This type of boiler is characterized by its simple design and affordable cost.
Any type of solid fuel is suitable for operation:
Coal.
Peat briquettes.
Firewood.
Waste from wood processing enterprises.
Pallets.
The best energy performance is achieved when working on coal, which has a high calorific value. Combustion is carried out due to the natural supply of outside air to the firebox. Modern models are equipped with thermostats that change the position of the damper at the entrance to the combustion chamber. During operation, it is necessary to regularly add fuel, remove ash and periodically clean the chimney of soot.
Obvious advantages of such boilers:
- ease of installation;
- fuel availability;
- no dependence on external networks (electric and gas).
Sectional view of a natural combustion solid fuel boiler.
Long-burning solid fuel boilers
Such devices represent the next step in the development of boiler equipment. They have an improved firebox shape, forced air supply, and an intelligent control system. The programs built into the control unit make it possible to increase the burning time of a single load of firewood by up to 24 hours, which is very convenient for residents. The relationship between the operation of the blower and the circulation pump, adjusted for temperature indicators, allows us to achieve optimal heating conditions for the building.
The peculiarity of these boilers is that the wood in them does not burn simultaneously throughout the entire volume of the firebox. The area of intense oxidation gradually moves from one end of the combustion chamber to the other.
Advantages of such equipment:
- adjustable combustion process with increased heating duration;
- economical fuel consumption;
- simplified maintenance;
- minimal soot formation.
Sectional view of a long-burning solid fuel boiler.
Pyrolysis boilers
Normal operation of boilers of this class occurs in the mode of high-temperature generation of combustible gases. In technology, this process is called pyrolysis. Wood is usually used as fuel, which, from a chemist’s point of view, is a complex mixture of high-molecular compounds. Under the influence of high temperatures and a lack of oxygen, they split into simple gases, which burn, releasing the main amount of heat.
The firebox of such a boiler is usually divided into two compartments. In the main chamber, the firewood smolders, intensely releasing flammable gases. Entering the afterburning zone, they mix with secondary air and burn out completely. The temperature of this stage reaches 1200o C, which guarantees the absence of harmful emissions in the exhaust mixture.
The heat generated in both chambers is generated by a water heat exchanger connected to the heating circuit of the building. Thanks to the complete combustion of fuel and controlled air supply, such boilers demonstrate the highest possible energy efficiency. The disadvantages include increased demands on the quality of the loaded firewood, the relative humidity of which in most cases should not exceed 16%.
Advantages of such equipment:
- high efficiency;
- lengthening the heating period on one fuel load;
- high level of automation;
- minimum of unburnt waste.
Sectional view of a pyrolysis boiler.
Pellet boilers
Pellet boilers operate on specially prepared solid fuel. Pellets are granules made from industrial waste: sawdust, agricultural plant residues, peat. They are distinguished by their convenient shape, low humidity and high calorific value.
Boilers of this category require almost no human intervention in the process of maintaining the fire. It may be enough to pour the granules into the bunker once a week. Automation will do the rest.
Given the availability of pellets, the advantages of such equipment are undeniable:
- economical operation;
- ease of operation and minimal maintenance;
- high level of automation;
- environmental Safety.
Sectional view of a pellet boiler.
Heat exchanger - steel or cast iron
The reliability and efficiency of the heating system largely depends on the material and design of the heat exchanger. Historically, there are two main types of heat exchangers supplied with solid fuel boilers.
Cast iron heat exchangers
Cast iron heat exchangers have a sectional structure. Their main advantages:
- ease of transportation and repair;
- resistance to chemical corrosion;
- ability to work at high temperatures;
- high thermal conductivity;
- acceptable cost.
But we should not forget about the shortcomings. Among them:
- high probability of destruction due to a sharp temperature change, which often happens when cold water is supplied to a hot apparatus;
- Such boilers take a little longer to warm up, but they retain heat for a longer time.
Steel heat exchangers
Steel heat exchangers are almost always manufactured as a single unit with the boiler. Steel is a more ductile material and is not afraid of temperature changes, but with intensive and careless use, thermal fatigue zones can form in the area of the welds, followed by the appearance of cracks. Unlike a cast iron heat exchanger, the design of which allows the replacement of a rejected section, high-quality repair of a steel block is only possible in a factory setting using welding and heat treatment.
Steel heat exchanger for solid fuel boiler.
What you need to know about power
The power of the boiler is its main characteristic. It shows how much thermal energy it is capable of generating per unit of time. This indicator directly depends on the type of fuel used, the size and design features of the equipment. It is laid down at the design stage and is confirmed by numerous tests of the finished sample. Household solid fuel boilers can reach a power of several tens of kW.
We must remember that most solid fuel boilers are adapted to operate on different types of fuel. The manufacturer usually indicates the maximum performance achieved under ideal conditions. When switching from using coal to raw wood, the loss of power can reach 25-30%.
Tips for choosing a boiler
The future owner of a solid fuel boiler should know the following before purchasing:
1. What type of fuel will be most simple and economical to purchase in your area of residence. This can be coal, peat, firewood, organic briquettes or pellets.
2. Determine the required power of the equipment used to heat the building. In general, to heat every 10 square meters of area of a well-insulated house, 1 kW of boiler energy is required. The calculation should be performed with a small margin, since the efficiency of heat transfer gradually decreases over the years of operation.
3. If you need not only to heat the building, but also to produce hot water for household needs, the boiler you purchase must be a double-circuit one.
4. The quality requirements for a boiler used in a cottage with continuous residence must be higher than for a country house visited periodically.
We gradually approached the selection of specific equipment. The proposed rating of solid fuel boilers for heating a private home should help you with this. When compiling it, the technical characteristics, reputation of manufacturers, reviews of specialists and users were taken into account.
conclusions
Despite the abundance of models of modern heating equipment, solid fuel boilers continue to be one of the most effective and affordable types of heating equipment. Compared to electric boilers, which have an efficiency of up to 90%, solid fuel units have a high economic effect. The increase in efficiency on new models has allowed this type of boiler equipment to come closer to electric and gas boilers.
Modern solid fuel devices are capable of not only operating for a long time using affordable natural fuel resources, but also have high performance characteristics.
The best solid fuel direct combustion boilers
Viadrus Hercules U22
The lineup
The model range of this series of Vidarus boilers is represented by seven solid fuel boilers with a capacity from 20 to 49 kW. The most productive of them is capable of heating a building with an area of up to 370 sq.m. All equipment is designed for a maximum pressure in the heating circuit of 4 atm. The operating temperature range in the coolant circulation system is from 60 to 90o C. The manufacturer claims the efficiency of each product at 78%.
Watch the product video
Design features
All models in the presented line are designed for floor installation. They have an open combustion chamber with air supplied due to natural draft. Large doors with a square configuration easily open wide, which is convenient when loading fuel, removing ash and inspecting the condition of internal elements.
The built-in heat exchanger made of high-quality cast iron is adapted to work in a single-circuit heating system. The boilers do not have devices powered from an external electrical network and operate in a completely autonomous mode. All settings are mechanical.
Fuel used. The design of the spacious firebox is designed to use wood as the main fuel, but coal, peat and briquettes can be used.
Zota Topol-M
The lineup
The line of six Zota Topol-M solid fuel boilers begins with a compact 14 kW model, designed to heat a home for an average family, and ends with an 80 kW unit capable of heating a large cottage or industrial workshop. The boilers are designed for operation in systems with pressures up to 3 bar. The efficiency of thermal energy use is 75%.
Watch the product video
Design features
Their distinctive feature is their slightly raised design, which makes it more convenient to open the ash pan door and empty it. The combustion chamber is open type with a chimney connection from the rear wall. There is a built-in temperature sensor. All adjustments are made manually.
A heat exchanger for a single-circuit heating system is mounted inside, connected to 1.5 or 2” pipelines. The boilers operate in autonomous mode. Products of this brand are easy to install and reliable in operation.
Fuel used. The fuel used is wood or coal, for which a special grate is provided.
Bosch Solid 2000 B-2 SFU
The lineup
Solid fuel boilers Bosch Solid 2000 B-2 SFU are presented in a number of models with power from 13.5 to 32 kW. They are capable of heating buildings with a usable area of up to 240 sq.m. Circuit operating parameters: pressure up to 2 bar, heating temperature from 65 to 95o C. Efficiency according to the passport is 76%.
Watch the product video
Design features
The units have a built-in single-section heat exchanger made of cast iron. It is connected to a single-circuit heating system through standard 1 ½” fittings. The boilers are equipped with an open combustion chamber with a chimney with a diameter of 145 mm. For normal operation, a connection to a 220 volt electrical network is required.
There is a temperature regulator and protection against water overheating. The ash pan has a small volume, so it requires regular cleaning. Manufacturer's warranty 2 years. The design is simple, safe and highly reliable.
Fuel used. The boiler is designed to use hard coal. Using this type of fuel it demonstrates high efficiency. When working with wood or briquettes, efficiency decreases noticeably.
Protherm Bober
The lineup
The Protherm Bober series of solid fuel boilers is represented by five models with power from 18 to 45 kW. This range completely covers any private home. The unit is designed to operate as part of a single-circuit heating circuit with a maximum pressure of 3 bar and a coolant temperature of up to 90 ° C. For the correct operation of the control system and activation of the circulation pump, a connection to a household electrical network is required.
Watch the product video
Design features
Boilers of this series are equipped with reliable cast iron heat exchangers. The original design of the combustion chamber increases the efficiency of heat transfer. Exhaust gases are discharged through a chimney with a diameter of 150 mm. For connection to the heating circuit there are 2" pipes. Such boilers are designed for long-term operation.
Fuel used. The declared power is designed to burn wood with a humidity of up to 20%. The manufacturer has provided for the possibility of using coal. In this case, work efficiency increases by several percent.
24-hour loss of thermal energy
To maintain the required temperature in the house, the solid fuel boiler must operate 24 hours a day. Now imagine how much useful heat flies out into the chimney in the form of soot and unburned gases during this time? The efficiency of such work cannot be 90%.
Another type of boiler worth mentioning here is the pyrolysis boiler. In addition to the above disadvantages, two more are added in his case:
- A fan running 24/7 consumes electricity.
- Thanks to the same fan, excess oxygen enters the boiler - the temperature of the gases decreases, they do not have time to burn and fly away into the chimney.
The accelerated movement of gases through the pipe causes a decrease in another parameter - heat transfer efficiency. Due to the special design of the boiler, the flame in it does not have time to burn out and rises into the heat exchanger, where it dies out, leaving soot along the way and throwing unburned gases into the chimney.
The best long-burning solid fuel boilers
Zota Carbon
The lineup
This domestic series of long-burning solid fuel boilers is represented by models with power from 15 to 60 kW. The equipment is intended for heating residential and industrial buildings. The boiler is single-circuit and has the following coolant parameters: maximum pressure 3 bar; temperature from 65 to 95o C. With optimal settings, efficiency reaches 80%. The boiler is easy to load and has movable grates for ash removal.
Watch the product video
Design features
The boilers are completely energy independent. Control is carried out mechanically. There is protection against overheating of the coolant. A built-in heat exchanger made of high-quality steel is installed. The duration of the combustion process is regulated by changing the flow rate of air entering the combustion chamber.
A chimney with a diameter of 180 mm and pipelines of a 2” circulation circuit are connected to the device from the rear wall.
Fuel used. It is recommended to use coal of fraction 10-50 mm as fuel.
Candle
The lineup
The line of Lithuanian heating equipment Candle includes five long-burning boilers with a power from 18 to 50 kW. They are intended for floor installation in residential or industrial premises. The units are designed to operate autonomously as part of a separate heating system. There is no additional circuit for heating hot water. The device is designed for a pressure of 1.8 bar and a coolant temperature of 90o C.
Watch the product video
Design features
The design of the open-type firebox and automatic air supply adjustment provide for a long combustion mode. The water “jacket” is built into the boiler body. There is automatic protection against overheating. Flue gas outlet pipe 160 mm. The diameter of the circulation circuit fittings is 2”.
Fuel used. Firewood or peat briquettes can be used as fuel.
Stropuva S
The lineup
The line of single-circuit long-burning boilers made in Lithuania includes models with a power of 8, 15, 20, 30 and 40 kW. The buyer can easily choose a suitable unit for heating a private home or small business. The most productive of them is capable of maintaining optimal temperature in a building with an area of up to 300 sq.m. No electrical connection required.
During operation, the combustion zone smoothly shifts in the firebox from top to bottom. Efficiency reaches 91.6%. Maintenance consists of periodically replacing fuel, removing ash and periodically cleaning the gas path, including the chimney.
Watch the product video
Design features
The elongated upward shape of the housing saves usable space during installation. The volumetric firebox allows you to load up to 80 kg of fuel. Precise adjustment of the incoming air extends the burning time of one bookmark to 31 hours. The coolant is heated to 70°C and circulates at a pressure of up to 2 bar. On the rear side there are fittings for connecting a chimney with a diameter of 200 mm and heating water 1 ¼”.
Fuel used. The boiler is designed to use dry wood as the main source of energy.
How to increase the efficiency of heating equipment running on solid fuels
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Today, many consumers, having at their disposal a solid fuel boiler, are trying to find the most convenient and practical way to increase the efficiency of heating equipment. The technological parameters of heating devices set by the manufacturer lose their nominal values over time, so various methods and means are being sought to increase the efficiency of boiler equipment.
Let's consider one of the most effective options, installing an additional heat exchanger. The task of the new equipment is to remove thermal energy from volatile combustion products.
In the video you can see how to make your own economizer (heat exchanger)
To do this, we first need to know what the temperature of the smoke at the outlet is. You can change it using a multimeter, which is placed directly in the middle of the chimney. Data on how much additional heat can be obtained from evaporating combustion products is necessary to calculate the area of the additional heat exchanger. We do the following:
- we send a certain amount of firewood into the firebox;
- We measure how long it takes for a certain amount of firewood to burn.
For example: firewood, in the amount of 14.2 kg. burn for 3.5 hours. The smoke temperature at the boiler outlet is 460 0 C.
In 1 hour we burned: 14.2/3.5 = 4.05 kg. firewood
To calculate the amount of smoke, we use the generally accepted value of 1 kg. firewood = 5.7 kg. flue gases. Next, we multiply the amount of wood burned in one hour by the amount of smoke produced by burning 1 kg. firewood As a result: 4.05 x 5.7 = 23.08 kg. volatile combustion products. This figure will become the starting point for subsequent calculations of the amount of thermal energy that can be additionally used to heat the second heat exchanger.
Knowing the value of the heat capacity of volatile hot gases as 1.1 kJ/kg, we make a further calculation of the heat flow power if we want to reduce the smoke temperature from 460 0C to 160 degrees.
Q = 23.08 x 1.1 (460-160) = 8124 kJ thermal energy.
As a result, we obtain the exact value of the additional power provided by volatile combustion products: q = 8124/3600 = 2.25 kW, a large figure that can have a significant impact on increasing the efficiency of heating equipment. Knowing how much energy is wasted, the desire to equip the boiler with an additional heat exchanger is completely justified. Due to the influx of additional thermal energy for heating the coolant, not only the efficiency of the entire heating system increases, but also the efficiency of the heating unit itself increases.
The best pyrolysis solid fuel boilers
Buderus Logano S171
The lineup
Floor-standing pyrolysis boilers made in Germany, Buderus Logano S171, are available in four modifications with a power of 20, 30, 40 and 50 kW. They operate automatically and do not require constant human supervision. Their performance is sufficient to heat low-rise buildings of various sizes. Equipment efficiency reaches 87%. For normal operation, a connection to a 220 volt electrical network is required. Electricity consumption does not exceed 80 W. The unit is reliable and easy to use. Manufacturer's warranty 2 years.
Watch the product video
Design features
The boiler has a spacious open-type combustion chamber with a two-stage air supply circuit. Exhaust gases are discharged through a chimney with a diameter of 180 mm. Wide doors facilitate the process of loading fuel and inspecting internal devices. The design pressure in the heating circuit is 3 bar. The coolant temperature is 55-85o C. Overheating protection is provided.
Fuel used. The main source of energy is dry firewood up to 50 cm long. The burning time of one bookmark is 3 hours.
Ecosystem ProBurn Lambda
The lineup
Bulgarian single-circuit pyrolysis boilers are available in two versions with a capacity of 25 and 30 kW. Their performance is sufficient to heat a medium-sized private house. To operate the automatic control system, a connection to a standard electrical network is required.
The unit is designed to heat circulating water up to 90o C. The maximum pressure in the circuit is 3 atmospheres. There is protection against overheating of the coolant. The boiler is easy to maintain and highly efficient. A 12 month warranty is provided.
Watch the product video
Design features
There is a pipe with a diameter of 150 mm for connecting the chimney and 1 ½” fittings for the circulation circuit. In the area where the flue gases exit the furnace, a probe is installed that measures the oxygen concentration. It gives control signals to the damper that regulates the air supply.
Fuel used. Regular wood is used as fuel.
Atmos DC 18S, 22S, 25S, 32S, 50S, 70S
The lineup
The line of elegant pyrolysis boilers of this brand includes a number of models with a power from 20 to 70 kW. They are intended for floor installation in residential, industrial and warehouse premises. The equipment is highly efficient and reliable. For correct operation of the automatic control system, the unit requires power from a 220 volt network. Maximum power consumption is 50 W.
The intelligent control system for air flow entering the combustion chamber ensures the efficiency of each model at 91%.
Watch the product video
Design features
The devices are distinguished by spacious fireboxes of a special configuration, wide doors and a convenient control panel. The heat exchanger is designed for a maximum pressure of 2.5 bar. Maximum heating of the coolant is 90o C. When overheating, a protective lock is triggered. The exhaust gas outlet pipe is adapted for connecting chimneys of various diameters.
Fuel used. To load the firebox, use firewood with a relative humidity of no more than 20%.
Kiturami KRH-35A
The lineup
This floor-standing boiler of the Korean brand is designed for heating residential and industrial premises with an area of up to 280 sq.m. It has two heat exchange circuits that work for heating and heating hot water for household needs. They are designed for operating pressures of 2 and 3.5 bar respectively. For correct operation of the equipment, a connection to an electrical network is required.
This model has a remote control unit with the ability to select several operating modes. Automation protects equipment from overheating and freezing of the coolant. Unit efficiency is 91%.
Watch the product video
Fuel used. The main difference of the presented brand is its versatility. The boiler can operate not only on solid fuel, but also on diesel fuel. When loading coal, its power reaches 35 kW. With the liquid fuel version it decreases to 24.4 kW.
Why you shouldn't trust advertising
When viewing advertisements related to the power of solid fuel boilers, you can often see offers promising 90% efficiency and higher. However, if you request any official protocol or act confirming this indicator, they will not be able to provide it to you, and here’s why.
To draw up such a document, it is necessary to carry out tests using appropriately standardized fuel. In relation to coal or firewood, it is impossible to obtain such fuel - because they are the most unstable in the world by their characteristics and composition. How can you get a constant indicator using non-constant components?
The best pellet boilers with hopper
Buderus Logano S181
German single-circuit solid fuel boilers Buderus Logano series S181 are presented in three models with a power of 15, 20 and 27 kW. They are used to heat low-rise residential and industrial buildings with an area of up to 216 sq.m. The equipment is designed to work with fine fractions of coal or pellets.
Watch the product video
Design features
Structurally, the products consist of two blocks installed in direct contact:
- the boiler itself with a combustion chamber, heat exchanger and control unit;
- a spacious bunker for storing fuel reserves with the ability to dose it into the combustion chamber.
To activate the mechanisms and operate the automation system, a power supply of 220 volts is required. The boiler is capable of heating the circulating coolant up to 80o C.
The heat exchanger is designed for a pressure of 3 bar. In case of overheating, automatic protection is triggered. Human participation in regulating the combustion process is almost not required. The efficiency of models in this range is 88%.
ACV TKAN
The lineup
The line of solid fuel boilers of the Belgian ACV brand is represented by household and industrial units with a power from 60 to 300 kW. They have one heating circuit for coolant circulating through the building’s heating system. The installed electrical equipment requires connection to an alternating current network of 220 volts.
Watch the product video
Design features
The unit consists of a housing with elements located inside it: a combustion chamber, an ash pan and heat exchange equipment. A spacious hopper with a supply of pellets is attached to the side. The heat exchanger is made of copper. This material conducts heat excellently, is not afraid of corrosion and is almost resistant to the adhesion of layers of scale and dirt. The equipment can withstand a pressure of 3 bar and heats the circulating water to 80o C.
Such boilers are designed for long-term operation without human control. Their efficiency reaches 90%.
Zota 15S Pellet
The lineup
Pellet boilers of this Russian brand are represented by a long range of heating devices with a power from 15 to 130 kW. They have one heating circuit and are used exclusively for heating rooms. Maximum parameters of the circulating coolant:
- pressure 3 bar;
- temperature 95o C.
In case of overheating, a lock is triggered. The device is distinguished by the presence of a large bunker designed to store a supply of pellets and feed them into the firebox. It allows you to leave the boiler for a long time without direct human control.
For the automation and transport line to function, the unit must be connected to a household electrical network. On the rear wall there are fittings for connecting a chimney with a diameter of 150 mm and heating pipelines of 2".
Watch the product video
Design features
If there are no pellets, you can switch to using regular firewood. To do this, you will have to install the additional grate included in the delivery set and disconnect the secondary air supply tubes. Boilers of this brand are not only simple and unpretentious, but also achieve an efficiency of 90%.
How to make efficiency high
There are many methods for increasing the efficiency of solid fuel equipment. Each of them helps to increase this parameter from 3 to 7%.
The most effective ways:
- Using quality fuel. If possible, it is necessary to use only dry and high-quality raw materials for heating the room.
- Regular removal of ash. If it is not possible to purchase expensive, high-quality fuel, it is necessary to clean the chimney more often.
- Ventilation of the room. Since the combustion process occurs in the middle part of the unit, it is necessary to ensure a stable flow of fresh air into the room where the equipment will be located.
- Reducing heat loss. If a residential building gives off heat faster than it heats up, purchasing higher quality fuel or even new boiler equipment will not give the desired result. Therefore, it is necessary to insulate the living space, install new windows made of wood or plastic, and reliable doors.
- Installation of auxiliary devices. To heat the house evenly, you need to use a circulation pump. This method is very effective and helps increase efficiency. If the old unit does not cope with the task of heating the house, then you can purchase an inexpensive boiler and install it in a cascade. Additional equipment can be used when the old one alone cannot cope with the heating task. You can find out Vilo pumps for heating at the link.
Liquid fuel devices for home heating
Liquid fuel heating devices usually use diesel fuel, oil or gasoline. Such a system works completely autonomously, and its characteristics are quite good: the room is heated quickly, and the heat lasts for quite a long time. But liquid fuel heaters have their weaknesses. Firstly, the installation of such a boiler requires a separate room, which will be maximally protected from a possible fire, therefore it is advisable to place liquid fuel heating boilers in brick extensions equipped with an exhaust hood. Secondly, the need for constant refueling suggests that it needs to be stored somewhere - and storing diesel fuel or gasoline is quite dangerous, since these substances can cause serious harm if stored incorrectly.
When choosing a boiler that runs on liquid fuel, you need to think about it in advance and consider alternative heating options, since many of them have a better level of fire safety than liquid fuel devices.
