Today, modern solid fuel boilers are often used to heat a private home, despite the fact that they are inferior in ease of use to their electric and gas competitors. This popularity of this equipment is primarily due to rising prices for traditional energy resources (especially electricity), as well as the lack of centralized gas supply in some regions. We should also not forget that waste from an agricultural or woodworking enterprise is often used as fuel for solid fuel boilers, which makes heating a private home absolutely free.
Types of fuel for solid fuel boilers
The list of fuel types suitable for use in a solid fuel boiler is quite wide; it includes almost everything that is not a gas or liquid and can burn. In most cases, the heat sources are:
- coal;
- peat;
- wood briquettes;
- pellets;
- waste in the form of wood shavings and sawdust;
- husks and husks of oilseeds and grain crops;
- straw.
Each type of fuel has its own requirements for the material and design of the firebox, the air supply system and some other components of the boiler. Of course, the fuel will burn even if all these parameters do not meet, but the efficiency of the boiler in this case will be significantly lower than the maximum possible. Therefore, before choosing a suitable solid fuel boiler model, you should decide exactly what type of fuel you will use in it.
The disadvantage of household solid fuel boilers is that this equipment is not capable of operating without user participation. Even in models with automatic fuel supply, it is necessary to constantly add fuel to the storage hopper, and the owner also needs to periodically remove ash.
Features of the design of solid fuel boilers
In their simplest form, household solid fuel boilers are devices consisting of a housing, a combustion chamber located inside it and a chimney. Such boilers provide so-called air heating, that is, simply put, they heat the air around them in the same way as a traditional Russian stove does. These models have the lowest cost, but it is impossible to use these types of modern boilers for a private house with several rooms. They are suitable for small buildings consisting of one or two rooms.
To heat the coolant of a water heating system, you should use a solid fuel boiler with a heat exchanger. The heat exchanger is blown with hot gases generated during fuel combustion, due to which the water circulating through it is heated. Heat exchangers are made of steel or cast iron.
Cast iron heat exchangers are considered the most preferable: they are more durable than steel ones, are not subject to corrosion and have better performance. However, they also have some disadvantages: cast iron is much less ductile than steel, so it tolerates temperature changes less well; The cast iron heat exchanger weighs significantly more than the steel one, which complicates the transportation and installation of the boiler. The main “minus” of steel heat exchangers is the fear of corrosion.
In modern models of household solid fuel boilers, this problem is solved by adding special additives to the steel composition that increase anti-corrosion resistance. Another disadvantage is that a steel heat exchanger, unlike a cast iron one, is a welded structure:
- Firstly, welds are weak point products;
- secondly, this method of manufacturing a heat exchanger significantly complicates its repair.
However, steel heat exchangers offer a very useful feature, which is the use of a cooling coil. When the temperature of the coolant rises above the permissible limits, the thermostatic valve will open, allowing cold water to flow into the container. Boilers with cast iron heat exchangers cannot use this method to lower the temperature of the coolant; the system must be refilled with cool water.
Double-circuit boilers
More “advanced” models of solid fuel boilers can be used not only for heating private houses, but also for heating water in a hot water supply system. Such boilers are called double-circuit boilers. Anyone who wants to buy such a device should take into account one circumstance: immediately at the moment of using a hot water tap, the boiler completely switches to heating the DHW circuit, and the heating is turned off.
This happens as follows: as a result of switching the valves, the coolant heated by the boiler is redirected to the heat exchanger of the DHW circuit, so it temporarily does not enter the heating system. Therefore, such a connection scheme for a solid fuel boiler is justified only if hot water is consumed occasionally and in small volumes. If you need a lot of water, the water supply system is supplemented with a storage tank (boiler), which provides the following advantages:
- allows you to increase the consumption of hot water;
- makes it possible to use hot water longer without turning off the heating;
- smoothes the operating mode of the boiler, reducing the frequency of its switching from the heating circuit to the DHW.
In inexpensive models of solid fuel boilers, fuel is loaded manually, while in more advanced versions this process is partially automated. Such boilers are equipped with a hopper from which fuel is supplied to the firebox by a screw or piston feeder. Of course, such a system is unlikely to be able to supply firewood instead of the user, but with bulk fuels - fine coal (with a size of 5 to 25 mm), pellets, etc. – will cope “excellently”. The volume of one filling of the bunker is usually enough for several days.
Pellet boilers
One of the most high-calorie and easy-to-use types of fuel are pellets, which are also called biogranules. They are mainly made from wood chips, but peat, sunflower seed husks, etc. can also be used. To obtain granules, the raw materials are crushed and then pressed under pressure reaching 300 atm. Therefore, pellets occupy a much smaller volume than a portion of chips in their pure form, having the same mass. Using pellet boilers for home heating is very convenient: one load into the bunker is enough for a whole week, and the fuel burns almost completely, so you can remove ash about once a month. This equipment differs from other types of solid fuel boilers, first of all, by the presence of a special burner called a pellet burner.
Basic setup of a pellet boiler consists of the following steps:
- precise adjustment of the turn-on and waiting times of the screw feeder when supplying fuel;
- selection of the optimal fan speed for air supply;
- adjustment of operating modes of circulation pumps in heating and hot water circuits;
- setting temperature conditions.
The maximum and minimum consumption of a pellet boiler is determined by several factors:
- boiler efficiency;
- fuel calorie content;
- thermal resistance of the building envelope;
- outside air temperature;
- the number of consumers connected to the boiler in addition to the heating system (warm floor system, hot water supply).
Pyrolysis boilers
If a domestic heating boiler in a private house is supposed to be heated with coal or wood fuel, it is better to give preference to a pyrolysis or, what is the same thing, a gas generator model. Such equipment is also called long-burning boilers. Pyrolysis is the process of formation of flammable gas during the smoldering of coal or wood fuel without access to oxygen. It takes place in a special boiler chamber and is accompanied by the release of a significant amount of heat. Wood gas, consisting mostly of ethylene and propylene, is fed through a ceramic nozzle into the second chamber, where air is pumped and where it is burned. Pyrolysis boilers solid fuels are very beneficial for the home because they have increased efficiency, and besides, cleaning them requires much less effort, because there is not much ash left after pyrolysis.
Rules for choosing a solid fuel boiler
Before choosing long-burning solid fuel boilers, you should calculate their power. On average, the specific energy consumption for heating a house with an area of 100 - 150 square meters. m is 120 – 130 W/sq. m, for a house with an area of 400 - 500 sq. m – from 80 to 85 W/sq. m.
It is also worth paying attention to various improvements that can significantly facilitate the operation of the equipment. For example, heating a country house with a solid fuel boiler can be controlled by commands from a mobile phone if the boiler is equipped with a GSM module with a SIM card installed in it.
As a conclusion, we recommend watching interesting video with a review of the operation of a cast iron solid fuel boiler.
When did solid fuel heating boilers appear? To answer this question, it is necessary to plunge deeply into the history of the development of heating.
After all, man has been using solid fuel virtually since the beginning of his “reasonable” existence. And if earlier a fire, a hearth, and then a stone stove were used for this, requiring constant attention and replenishment of fuel, today their function can be performed by simple or fully automated solid fuel heating boilers.
The principle of their operation is based on obtaining heat from the combustion of solid fuel and transferring it to the coolant (water) circulating in the heating system. Such heating devices are installed where it is not possible to heat with gas or electricity (often for financial reasons).
Often, a combination of different boilers is used in a heating system project for a private home or office space. For example, the main heating unit runs on gas, and a solid fuel boiler is used as an emergency boiler in case of interruptions in gas supply. Or vice versa - a gas boiler is an alternative option.
In this article we will cover the topic of classifying solid fuel heating boilers, consider their main parameters, additional devices that expand their functionality. In general, we will reveal the basic concepts about this technique so that you can make the right choice if necessary.
Interesting to know!
The authorship of the creation of water heating informally belongs to Martin Trivald from Sweden. While working as a coal mine supervisor, he first used water heating for heating the greenhouse. Only a century later, in 1820, a similar heating method began to be used in private homes in England, and later in other countries.
What is solid fuel?
In modern boilers the following are used as solid fuel:
- firewood;
- wood chips;
- coal;
- brown coal;
- peat briquettes;
- biofuel (pellets).
The use of these substances for heating is economically justified if cheap solid fuel options are available. The most fashionable and convenient solid fuel today is biofuel pellets - these are wood waste pressed into small briquettes.
Let's understand the types of solid fuel heating boilers
Regardless of whether it is a simple boiler or one with a mechanical fuel supply and a self-cleaning system, they still require human attention and participation in the process of their “life activity,” as well as compliance with strict safety rules during their operation.
By type of material, from which they are made, there are two types of boilers:
- steel;
- cast iron.
Each type has its own strengths and weaknesses!
For example, steel boilers are less susceptible to temperature changes, but they are highly susceptible to corrosion. A cast iron boiler is considered “long-lived” compared to a steel one, but it is fragile, afraid of overheating, and warms up slowly.
During operation, it is necessary to monitor the presence of water in the “water” jacket of the boiler. Its absence (which is unlikely, but...) can cause overheating and deformation of the boiler.
According to the combustion mechanism of solid fuel, in particular firewood, boilers can be divided into two groups:
- classical combustion boilers
- long burning boilers
- pyrolysis,
- smoldering.
The first group includes most of the simple cast iron and steel solid fuel boilers, inside which an uncontrolled normal combustion process takes place.
Some kind of “automation” is still present in such boilers. They can have a sensor installed to control the temperature of the water in the boiler, connected mechanically (by a chain) to an air damper, which affects the intensity of the combustion process in the furnace.
When the water temperature exceeds the permissible limit, the damper closes, slowing down the combustion process. A further decrease in water temperature leads to a gradual opening of the damper.
More advanced models have electronic temperature sensors and a controller that analyzes their data and controls the operation of an additional forced-air fan. This brings a significant amount of comfort to working with such solid fuel heating boilers.
Advantages:
- ease of maintenance;
- relatively low cost;
- ability to work autonomously (without electricity);
Flaws:
- the need for fairly frequent fuel replenishment. Frequency: 3-8 hours.
Boilers of this type are often used in a system with a heat storage tank, which allows the water temperature to be maintained for some time after the boiler has died down.
Among the manufacturers of “classical” combustion solid fuel heating boilers, the following have proven themselves well: SAS, Aton, Wichlaczh, Sime, Galmet, Biasi.
Boilers of the second group are called pyrolysis or smoldering.
Pyrolysis boilers use the principle of gasified wood combustion. These are boilers with a long burning time on one “refueling” (about 10-12 hours) and high efficiency (up to 92%), due to the fact that wood gas is first released from the wood under the influence of high temperature, which is then burned in a second firebox.
Such boilers are high-tech devices, “stuffed” with electronics. By the way, their firebox is ceramic, capable of retaining heat for a long time, and is equipped with a fan that regulates the intensity of combustion. It also makes it easier to light the boiler and makes loading a new batch of firewood comfortable, preventing smoke from entering the room.
There are some disadvantages: the high cost of boilers, the relatively small volume of the working chamber for loading.
The Czech brands Atmos and Verner are recognized as European leaders in the production of pyrolysis boilers. You will be 100% satisfied with their products.
Operating principle of a solid fuel pyrolysis boiler
In their operating principle, “smoldering” type boilers use the phenomenon of smoldering of the upper part of the fuel. This process can “stretch”, in the case of using firewood, up to 30 hours. And the Baltic manufacturer Stropuva has in its arsenal a universal-purpose model with the designation “U”, capable of “holding out” on coal for up to 5 days. In addition, smoldering boilers are relatively inexpensive.
The disadvantages of such boilers include their “demanding” requirements for fuel:
- humidity (wood) up to 15-20%, coal highest quality;
- length up to 60 cm;
- power up to 40 kW.
Manufacturers – Baltic countries Stopuva and Candle.
The required power of a solid fuel boiler is approximately calculated based on the proportion: per 10 m2 of insulated room area with ceilings up to 3 m - 1 kW of boiler power. For exact numbers, contact a professional.
Important! Excessive boiler power can only be useful when using low-quality fuel, for example, not enough dry firewood.
Solid fuel boiler STROPUVA - video presentation
Notice! Among the huge range of solid fuel heating boilers, some manufacturers have models that allow the installation of additional gas burners or liquid fuel burners.
Let us separately dwell on another type of heating boilers, which are becoming increasingly popular - pellet boilers.
Pellets- these are cylinders pressed under high pressure from biomass.
Options:
- diameter: from 6 to 1.4 mm;
- length: from 5 to 20 mm;
- density: up to 600kg/m3;
- ash volumetric residue: up to 3%.
The advantages of pellet boilers include, first of all, the possibility of automating their operation, which is not possible either with coal or with wood.
Pellet heating boilers today are one of the safest, environmentally friendly ways to produce heat indoors.
The range of pellet boilers is already huge. Unites them all high level automation of the combustion process and principles of work organization:
- possibility of automatic fuel supply from a bunker or warehouse;
- maintaining a stable temperature;
- centralized control of the entire heating system (circulation pumps, self-cleaning systems, etc.)
Domestic boilers have a power in the range of 10-100 kW, industrial boilers - up to 1500 kW. Efficiency factor - up to 95%!!!
In addition, such boilers do not require constant human presence. The boiler can be equipped with an automatic ash removal system; fuel is supplied not from the bunker, but from the adjacent room - the fuel warehouse, with a volume that allows the boiler to operate for more than a month. Such boilers support remote control via a mobile phone.
To summarize, today there is plenty to choose from in the field of solid fuel heating systems. It all depends on the characteristics of the territory where you live and... on the size of your wallet.
“A boiler is really a stove in a barrel of water”... and the efficiency of such a unit will be at best 10%, or even 3-5%. After all, a solid fuel boiler is not a stove at all, and a solid fuel stove is not a hot water boiler. The fact is that the combustion process of solid fuel, unlike gas or flammable liquids, is certainly extended in space and time. Gas or oil can be completely burned immediately in a small gap from the nozzle to the burner diffuser, but wood and coal cannot. Therefore, the requirements for the design of a solid fuel heating boiler are different than for heating stove, you can’t just stick a heating circuit water heater into it with continuous circulation. Why this is so, and how a continuous heating boiler should be designed, is what this article is intended to explain.
Your own heating boiler in a private house or apartment becomes a necessity. Gas and liquid fuels are steadily becoming more expensive, and in return, inexpensive alternative fuels are appearing on sale, for example. from crop waste - straw, husks, husks. This is only from the point of view of the owners of the house, not to mention the fact that the transition to individual heating will allow you to get rid of energy losses in the main lines of thermal power plants and power line wires, and they are by no means small, up to 30%
You cannot make a gas boiler yourself, if only because no one will give permission to operate it. It is prohibited to use individual liquid fuel boilers for heating residential premises due to their high fire and explosion hazard when used in a decentralized manner. But you can make a solid fuel boiler with your own hands and register it officially, just like a heating stove. This is perhaps the only thing they fundamentally have in common.
Features of solid fuel
Solid fuel does not burn very quickly, and in its visible flame not all components that carry thermal energy. For complete combustion of flue gases, a high but well-defined temperature is required, otherwise conditions will arise for endothermic reactions to occur (for example, nitrogen oxidation), the products of which will carry away the energy of the fuel into the chimney.
Why doesn't the boiler bake?
The oven is a cyclic device. So much fuel is loaded into its firebox at once so that its energy lasts until the next fire. The excess combustion energy of the fuel load is partially used to maintain the optimal temperature for afterburning in the gas path of the furnace (its convective system), and is partially absorbed by the furnace body. As the load burns out, the ratio of these parts of fuel energy changes, and a powerful flow of heat circulates inside the furnace, several times more powerful than the current needs for heating.
The body of the stove is thus a heat accumulator: the main heating of the room occurs due to its cooling after heating. Therefore, it is impossible to take away the heat circulating in the furnace; this will somehow disrupt its internal thermal balance, and the efficiency will drop sharply. It is possible, and even then not in every place of the convection system, to take up to 5% to replenish the hot water storage tank. Also, the stove does not require operational adjustment of its thermal power; it is enough to load fuel based on the required average hourly time between firings.
A water boiler, no matter what fuel it uses, is a continuous operation device. The coolant circulates in the system all the time, otherwise it will not heat, and the boiler must at any given moment provide exactly as much heat as was lost outside due to heat loss. That is, fuel must either be periodically loaded into the boiler, or the thermal power must be quickly adjusted within a fairly wide range.
The second point is flue gases. They must approach the heat exchanger, firstly, as hot as possible in order to ensure high efficiency. Secondly, they must be completely burned out, otherwise the fuel energy will be deposited on the register as soot, which will also need to be cleaned.
Finally, if the stove heats around itself, then the boiler as a heat source and its consumers are separated. The boiler requires a separate room (boiler room or furnace): Due to the high concentration of heat in the boiler, its fire danger is much higher than that of the furnace.
Note: An individual boiler room in a residential building must have a volume of at least 8 cubic meters. m, ceiling at least 2.2 m high, opening window at least 0.7 sq. m, a constant (without valves) flow of fresh air, a smoke channel separate from other communications and a fire separation from the other rooms.
From this it follows, firstly, boiler furnace requirements:
- It should ensure fast and complete combustion of fuel without a complex convection system. This can only be achieved in a firebox made of materials with the lowest possible thermal conductivity, because For rapid combustion of gases, a high concentration of heat is required.
- The firebox itself and the parts of the structure associated with it in heat should have the lowest possible heat capacity: all the heat that went into heating them will remain in the boiler room.
These requirements are initially contradictory: materials that conduct heat poorly, as a rule, accumulate it well. Therefore, a regular stove firebox will not work for a boiler; some kind of special one is needed.
Heat exchange register
The heat exchanger is the most important component of a heating boiler; it mainly determines its efficiency. The design of the heat exchanger is what the entire boiler is called. In household heating boilers, heat exchangers are used - water jackets and tubular, horizontal or vertical.
A boiler with a water jacket is the same “stove in a barrel”; a heat exchange register in the form of a tank surrounds the firebox. A jacketed boiler can be quite economical under one condition: if the combustion in the firebox is flameless. A flaming solid fuel furnace certainly requires afterburning of the exhaust gases, and in contact with the jacket their temperature immediately drops below the value required for this. The result is an efficiency of up to 15% and increased deposition of soot, and even acid condensate.
Horizontal registers, generally speaking, are always inclined: their hot end (supply) must be raised above the cold (return), otherwise the coolant will flow backwards and failure forced circulation will immediately lead to a serious accident. In vertical registers, the pipes are located vertically or slightly inclined to the side. In both cases, the pipes are arranged in rows in a checkerboard pattern, so that gases are better “entangled” in them.
Regarding the directions of movement of hot gases and coolant, pipe registers are divided into:
- Flow-through - gases generally flow perpendicular to the coolant flow. Most often, this scheme is used in horizontal industrial boilers of high power due to their lower height, which reduces the cost of installation. In households, the situation is the opposite: in order for the register to properly capture the heat, it has to be made extended upward above the ceiling.
- Countercurrent - gases and coolant move along the same line towards each other. This scheme provides the most efficient heat transfer and the highest efficiency.
- Flow - gases and coolant move parallel in one direction. Rarely used in special-purpose boilers, because At the same time, efficiency is poor, and equipment wear is high.
Further, heat exchangers are made of fire tube and water tube. In fire tubes, smoke tubes carrying flue gases pass through a tank of water. Fire tube registers operate stably, and vertical ones provide good efficiency even in a flow diagram, because internal water circulation is established in the tank.
However, if we calculate the optimal temperature gradient for heat transfer from gas to water based on the ratio of their density and heat capacity, then it turns out to be approximately 250 degrees. And to push this heat flow through the wall steel pipe 4 mm (you can’t do less, it will burn out very quickly) without noticeable losses on the thermal conductivity of the metal, you need about 200 degrees more. As a result, the inner surface of the smoke pipe should be heated to 500-600 degrees; 50-150 degrees – operational margin for fuel water cut, etc.
Because of this, the service life of the smoke tubes is limited, especially in large boilers. In addition, the efficiency of a fire tube boiler is low; it is determined by the ratio of the temperatures of hot gases entering the register and those exiting the chimney. It is impossible to allow gases to cool below 450-500 degrees in a fire tube boiler, and the temperature in a conventional firebox does not exceed 1100-1200 degrees. According to the Carnot formula, it turns out that the efficiency cannot be higher than 63%, and the efficiency of the firebox is no more than 80%, so the total is 50%, which is very bad.
In small domestic boilers these features have a weaker effect, because when the size of the boiler decreases, the ratio of the register surface to the volume of flue gases in it increases, this is the so-called. square-cube law. In modern pyrolysis boilers, the temperature in the combustion chamber reaches 1600 degrees, the efficiency of their furnace is 100%, and the registers of branded boilers, guaranteed for 5 years or more, are made only of thin-walled heat-resistant special steel. In them, gases can be allowed to cool to 180-250 degrees, and the overall efficiency reaches 85-86%
Note: Cast iron is generally unsuitable for smoke pipes; it cracks.
In water-tube registers, the coolant flows through pipes placed in a fire chamber into which hot gases enter. Now temperature gradients and the square-cube law operate in the opposite way: at 1000 degrees in the chamber, the outer surface of the pipes will be heated to only 400 degrees, and the inner surface will be heated to the temperature of the coolant. As a result, pipes made of ordinary steel last a long time and the boiler efficiency is about 80%
But horizontal flow-through water tube boilers are prone to the so-called. "flooding". The water in the lower pipes turns out to be much hotter than in the upper ones. It is pushed into the supply first, the pressure drops, and the colder upper pipes “spit out” the water. “Buhtenie” not only provides as much noise, heat and comfort as a neighbor who is a drunkard and a brawler, but is also fraught with a break in the system due to water hammer.
Vertical water-tube boilers do not fire, but if a water-tube boiler is being designed for a house, the register should be located at the bottom of the chimney, in the section where hot gases flow from top to bottom. In an in-line water-tube boiler with the same direction of movement of gases and coolant, the efficiency drops sharply and soot is intensively deposited on the pipes near the supply, and it is generally unacceptable to make a return above the supply.
About the heat exchanger capacity
The ratio of the heat exchanger capacities and the entire cooling system is not taken arbitrarily. The rate of heat transfer from gases to water is not infinite; the water in the register must have time to absorb heat before it leaves the system. On the other hand, the heated outer surface of the register gives off heat to the air, and it is wasted in the boiler room.
A register that is too small is prone to boiling and requires precise, quick adjustment of the firebox power, which is unattainable in solid fuel boilers. A large-volume register takes a long time to warm up and in poor conditions external thermal insulation boiler or its absence loses a lot of heat, and the air in the boiler room can warm up above the permissible fire safety and boiler specifications.
The size of the heat exchanger capacity of solid fuel boilers ranges from 5-25% of the system capacity. This must be taken into account when choosing a boiler. For example, for heating, according to the calculation, there were only 30 sections of radiators (batteries) of 15 liters each. With water in the pipes and an expansion tank, the total capacity of the system will be about 470 liters. The boiler register capacity should be between 23.5-117.5 liters.
Note: There is a rule - the greater the calorific value of solid fuel, the greater the relative capacity of the boiler register should be. Therefore, if the boiler is coal-fired, the register capacity should be taken closer to the upper value, and for a wood-burning boiler - to the lower value. For slow-burning boilers, this rule is not valid; the capacity of their registers is calculated based on the highest efficiency of the boiler.
What is the heat exchanger made of?
Cast iron as a material for a boiler register does not meet modern requirements:
- The low thermal conductivity of cast iron leads to low boiler efficiency, because It is impossible to cool the exhaust gases below 450-500 degrees; as much heat as needed will not pass through the cast iron into the water.
- The high heat capacity of cast iron is also its disadvantage: the boiler must quickly release heat into the system before it evaporates somewhere else.
- Cast iron heat exchangers do not fit into modern weight and size requirements.
For example, let's take the M-140 section from the old Soviet cast iron battery. Its surface area is 0.254 square meters. m. For heating 80 sq. m of living space, a heat exchange surface in the boiler of approximately 3 square meters is required. m, i.e. 12 sections. Have you seen a battery with 12 sections? Imagine what the cauldron must be like in which it will fit. And the load on the floor from it will definitely exceed the limit according to SNiP, and a separate foundation will have to be made for the boiler. In general, 1-2 cast iron sections will go to the heat exchanger that feeds the hot water storage tank, but for a heating boiler the question of a cast iron register can be considered closed.
The registers of modern factory boilers are made of heat-resistant and heat-resistant special steel, but their production requires production conditions. What remains is ordinary structural steel, but it corrodes very quickly at 400 degrees and above, so fire tube boilers made of steel must be selected for purchase or developed very carefully.
In addition, steel conducts heat well. On the one hand, this is not bad; you can expect to obtain good efficiency using simple means. On the other hand, the return flow should not be allowed to cool below 65 degrees, otherwise acidic condensate will fall onto the register in the boiler from the flue gases, which can eat through the pipes within an hour. You can exclude the possibility of its deposition in 2 ways:
- For boiler power up to 12 kW, a bypass valve between the boiler flow and return is sufficient.
- With greater power and/or heated area of more than 160 sq. We also need an elevator unit, and the boiler must operate in the mode of superheating water under pressure.
The bypass valve is controlled either electrically from a temperature sensor, or energy-independently: from a bimetallic plate with traction, from wax melting in a special container, etc. As soon as the temperature in the return drops below 70-75 degrees, it admits hot water from the supply into it.
The elevator unit, or simply the elevator (see figure), acts in the opposite way: the water in the boiler is heated to 110-120 degrees under pressure of up to 6 ati, which eliminates boiling. To do this, the combustion temperature of the fuel is increased, which increases efficiency and eliminates condensation. And before entering the system, hot water is diluted with return water.
In both cases, forced water circulation is necessary. However, it is quite possible to create a steel boiler using thermosiphon circulation that does not require power supply for the circulation pump. Some designs will be discussed below.
Circulation and boiler
Thermosiphon (gravity) circulation of water does not allow heating a room with an area of more than 50-60 square meters. m. The point is not only that it is difficult for water to squeeze through a developed system of pipes and radiators: if you open the drain valve when the expansion tank is full, water will rush out in a strong stream. The fact is that the energy for pushing water through the pipes is taken from the fuel, and the efficiency of converting heat into movement in a thermosiphon system is negligible. Therefore, the efficiency of the boiler as a whole decreases.
But the circulation pump requires electricity (50-200 W), which may be lost. A UPS (uninterruptible power supply) for 12-24 hours of autonomous operation is very expensive, so a properly designed boiler is designed for forced circulation, and if the power supply is lost, it must, without outside intervention, go into thermosiphon mode, when the heating is barely warm, but still warms.
How to install the boiler?
The requirement for a boiler’s minimum intrinsic heat capacity directly follows from its low weight compared to a stove and its weight load per unit floor area. As a rule, it does not exceed the minimum allowable according to SNiP for flooring of 250 kg/sq. m. Therefore, installing a boiler is permissible without a foundation and even dismantling the flooring, incl. and on the upper floors.
Place the boiler on a flat, stable surface. If the floor plays, it will still have to be dismantled at the boiler installation site down to the concrete screed with a distance of at least 150 mm to the sides. The base for the boiler is covered with asbestos or basalt cardboard 4-6 mm thick, and a sheet of roofing iron 1.5-2 mm thick is placed on it. Next, if the flooring has been dismantled, the bottom of the boiler is lined with cement-sand mortar to the floor level.
Around the boiler protruding above the floor, thermal insulation is made, the same as underneath: asbestos or basalt cardboard, and iron on it. The removal of insulation to the sides from the boiler is from 150 mm, and in front of the firebox door is at least 300 mm. If the boiler allows additional fuel loading before the previous portion burns out, then the removal in front of the firebox is required from 600 mm. Under the boiler, which is placed directly on the floor, place only thermal insulation, covered steel sheet. Removal - as in the previous case.
A separate boiler room is required for a solid fuel boiler. The requirements for it are given above. In addition, almost all solid fuel boilers do not allow power adjustment within a wide range, so they require a full-fledged piping - a set of additional equipment that ensures efficient and trouble-free operation. We’ll talk about it later, but in general, boiler piping is a separate big topic. Here we mention only the immutable rules:
- The installation of the piping is carried out in counterflow to the water, from the return to the supply.
- Upon completion of installation, its correctness and quality of connections are checked visually according to the diagram.
- The installation of the heating system in the house begins only after piping the boiler.
- Before loading fuel and, if required, supplying power, the entire system is filled with cold water and all joints are monitored for leaks during the day. In this case, water is water, and not some other coolant.
- If there are no leaks, or after they have been eliminated, the boiler is started on water, continuously monitoring the temperature and pressure in the system.
- Once the nominal temperature is reached, the pressure is controlled for 15 minutes; it should not change by more than 0.2 bar, this process is called pressure testing.
- After pressure testing, the boiler is extinguished and the system is allowed to cool completely.
- Drain the water and fill in the standard coolant.
- Check the joints for leaks once again 24 hours. If everything is in order, the boiler is started. No - they fix the leaks, and again daily monitoring before starting.
Choosing a boiler
Now we know enough to choose a boiler based on the intended type of fuel and its purpose. Let's get started.
Wood burning
The calorific value of firewood is low, the best ones have less than 5000 kcal/kg. Firewood burns quite quickly, releasing a large volume of volatile components that require afterburning. Therefore, it is better not to count on high efficiency using wood, but they can be found almost everywhere.
Wood burning for the house
A home wood-burning boiler can only burn for a long time, otherwise it will damage it in all respects. Industrial structures, e.g. the well-known KVR, cost from 50,000 rubles, which is still cheaper than building a furnace, do not require power supply and allow power adjustment for heating in the off-season. As a rule, they operate on coal and any solid fuel, except sawdust, but with coal, fuel consumption will be much higher: heat transfer from one load is 60-72 hours, and for specialized coal ones – up to 20 days.
However, a long-burning wood-burning boiler can be useful in places where there is no regular supply of coal and qualified heating service. It costs one and a half times less than coal, its jacket design is very reliable and allows you to build a thermosiphon heating system with an area of up to 100 square meters. m.. In combination with the smoldering of the fuel in a thin layer and a fairly large volume of the jacket, boiling of water is excluded, so the piping is sufficiently the same as for titanium. Connecting a long-burning wood-burning boiler is also no more difficult than titanium, and can be done independently by an unqualified owner.
About brick boilers
Diagram of the boiler “Blago”
Brick is the friend of the stove and the enemy of the boiler due to the fact that it gives the structure greater thermal inertia and weight. Perhaps the only brick boiler in which the brick is in its place is Belyaev’s pyrolysis “Blago”, diagram in Fig. And then, its role here is completely different: the lining of the combustion chamber is made of fireclay bricks. Horizontal water tube heat exchanger; The problem of coiling is solved by the fact that the register pipes are single, flat, elongated in height.
Belyaev’s boiler is truly omnivorous, and there are 2 separate bunkers for loading different types of fuel without stopping the boiler. “Blago” can work on anthracite for several days, on sawdust – up to a day.
Unfortunately, Belyaev’s boiler is quite expensive, due to the fireclay lining it is poorly transportable and, like all pyrolysis boilers, requires complex and expensive piping. Its power is regulated within small limits by bypassing flue gases, so it will show good efficiency on average for the season only in places with prolonged severe frosts.
About boilers in the furnace
The boiler in the furnace, about which they talk and write so much now, is a water-tube heat exchanger immured in the furnace masonry, see fig. below. The idea is this: after firing, the stove should release heat more directly than into the surrounding air. Let's say right away: reports of an efficiency of 80-90% are not only doubtful, but simply fantastic. The best brick oven itself has an efficiency of no higher than 75%, and its outer surface area will be no less than 10-12 square meters. m. The surface area of the register is unlikely to be more than 5 square meters. m. In total, less than half of the heat accumulated by the furnace will go into the water, and the overall efficiency will be below 40%
Next point - a stove with a register immediately loses its properties. Under no circumstances should you heat it out of season with an empty register. TKR ( temperature coefficient expansion) of metal is much greater than that of a brick, and the heat exchanger, swollen from overheating, will tear the stove before our eyes. Thermal seams will not help the matter; the register is not a sheet or a beam, but a three-dimensional structure, and it is bursting in all directions at once.
There are other nuances here, but the general conclusion is clear: a stove is a stove, and a boiler is a boiler. And the fruit of their forced unnatural union will not be viable.
Boiler piping
Boilers that prevent boiling of water (long-burning jacket boilers, titanium boilers) cannot be made with a power of more than 15-20 kW and cannot be extended in height. Therefore, they always provide heating for their area in thermosiphon mode, although a circulation pump, of course, would not hurt. In addition to the expansion tank, their piping includes only an air drain valve at the highest point of the supply pipeline and a drain valve at the lowest point of the return line.
The wiring of solid fuel boilers of other types should provide a set of functions, which can be better understood in Fig. on right:
- safety group: air drain valve, general pressure gauge and breakthrough valve for releasing steam during boiling;
- emergency cooling storage tank;
- its float valve is the same as in the toilet;
- thermal valve for starting emergency cooling with its sensor;
- MAG block – drain valve, emergency drain valve and a pressure gauge, assembled in one housing and connected to a membrane expansion tank;
- forced circulation unit with a check valve, a circulation pump and an electrically temperature-controlled three-way bypass valve;
- intercooler - emergency cooling radiator.
Pos. 2-4 and 7 make up the power reset group. As already mentioned, solid fuel boilers are regulated in terms of power within small limits, and with sudden warming, the entire system may overheat unacceptably, even to the point of bursting. Then thermal valve 4 lets tap water into the intercooler, and it cools the supply to normal.
Note: The owner's money for fuel and water flows quietly and peacefully down the drain. Therefore, solid fuel boilers are not suitable for places with mild winters and long off-season periods.
The forced circulation group in normal mode bypasses part of the supply to the return line so that its temperature does not fall below 65 degrees, see above. When the power supply is turned off, the thermal valve closes. The heating radiators receive as much water as they can handle in thermosiphon mode, just so that the rooms can be lived in. But the intercooler thermal valve opens completely (it is kept closed under voltage), and excess heat again carries the owner’s money down the drain.
Note: If the water goes out along with the electricity, the boiler needs to be extinguished immediately. When water flows out of tank 2, the system will boil.
Boilers with built-in overheating protection are 10-12% more expensive than conventional ones, but this is more than compensated by simplifying the piping and increasing the reliability of the boiler: here excess superheated water is poured into an open large-capacity expansion tank, see figure, from where it cools and flows into return. The system, except for circulation pump 7, is energy-independent and switches to thermosiphon mode smoothly, but with sudden warming, the fuel is still wasted, and the expansion tank must be installed in the attic.
As for pyrolysis boilers, we provide a typical wiring diagram for your information only. All the same, its professional installation will cost only a fraction of the cost of the components. For reference: the heat accumulator alone for a 20 kW boiler costs about $5,000.
Note: Membrane expansion tanks, unlike open ones, are installed on the return line at its lowest point.
Chimneys for boilers
Chimneys of solid fuel boilers are calculated in general in the same way as stoves. General principle: a chimney that is too narrow will not provide the required draft. This is especially dangerous for the boiler, because it is heated continuously and fumes can occur at night. A chimney that is too wide leads to “whistle”: cold air descends through it into the firebox, cooling the stove or register.
The boiler chimney must meet the following requirements: the distance from the ridge of the roof and between different chimneys is at least 1.5 mm, the lift above the ridge is also at least 1.5 m. Safe access to the chimney must be provided on the roof at any time of the year. There must be a cleanout door at every chimney break outside the boiler room, and every pipe passage through the ceilings must be thermally insulated. The upper end of the pipe must be equipped with an aerodynamic cap; for a boiler chimney, it is required, unlike for a stove. Also, a condensate collector is required for the boiler chimney.
In general, calculating a chimney for a boiler is somewhat simpler than for a stove, because The boiler chimney is not so tortuous; the heat exchanger is considered simply a lattice barrier. Therefore, it is possible to build generalized graphs for different design cases, for example. for a chimney with a horizontal section (burrow) of 2 m and a condensate collector 1.5 m deep, see fig.
Using such graphs, after an accurate calculation using local data, you can estimate whether there was a gross error. If the calculated point is somewhere around its generalized curve, the calculation is correct. In extreme cases, you will have to extend or cut the pipe by 0.3-0.5 m.
Note: if, say, for a pipe 12 m high there is no curve for a power less than 9 kW, this does not mean that a 9 kW boiler cannot be operated with a shorter pipe. It’s just that for lower pipes a generalized calculation is no longer possible, and it is necessary to calculate exactly according to local data.
Video: example of construction of a shaft-type solid fuel boiler
conclusions
The depletion of energy resources and rising fuel prices have radically changed the approach to the design of household heating boilers. Now they, like industrial ones, are required to have high efficiency, low thermal inertia and the ability to quickly regulate power over a wide range.
In our time, heating boilers, according to the basic principles laid down in them, have finally diverged from stoves and were divided into groups for different climatic conditions. In particular, the considered Solid fuel boilers are suitable for areas with harsh climates and prolonged severe frosts. For places with a different climate, other types of heating devices will be preferable.
1.
2.
3.
4.
5.
6.
For a long time, in every house located in the Russian expanses, the heating stove was the most important place. Thanks to the stove, the house was warm in winter. In addition, food was prepared on them, and some structures with a bed even made it possible to sleep. In many rural huts, the stoves are still preserved. Over time, they have undergone significant changes and now owners use solid fuel, electricity or gas boilers to provide heating.
Gas heating is deservedly considered the most optimal solution to the heat supply problem, but, unfortunately, the mains are not laid in all populated areas. Electric heating of a home is an expensive option, and an unstable power supply can lead to equipment shutdown or breakdown. Therefore, property owners, especially in rural areas, prefer to install solid fuel heat generators.
Classification of solid fuel boilers
Depending on the material of manufacture, a solid fuel heating boiler can be:- cast iron;
- steel.
The operation of all models of devices operating on solid fuel depends on the presence of water in the heating structure. If the amount of coolant in the system reaches a critical level, overheating and deformation of individual elements is possible. Steel units are more resistant to temperature fluctuations, and cast iron products are more resistant to corrosive processes.
The following information will be useful for consumers: the required volume of fuel for loading is calculated based on certain standards. For one kilowatt, steel boilers require 1.6 - 2.6 liters, and for cast iron appliances 1.1 -1.4 liters.
Thus, cast iron and steel heat generators differ not only in weight and material of manufacture, but also in other characteristics, including structural differences. So the cooling coil in steel solid fuel boilers is located inside them. When the coolant heats up to a critical temperature, you can open the thermostatic tap slightly, after which cold water will begin to flow and thereby lower the temperature.
In cast iron boilers, such as in the photo, similar elements are located on the supply. You can lower the temperature in them only by partially draining the hot water and adding cold coolant. When producing a cast iron product, its sections are assembled into a single device using steel pins. As for the steel unit, its parts are connected by welding. The strength of the seams depends on its quality.
Loading firewood, coal, pellets into solid fuel heating boilers is done manually by opening/closing the loading hatch door. Since its internal part comes into contact with fire and gets very hot, a person can get a serious burn if they come into contact with it. To prevent this from happening, cast iron units have a door with a special protective layer. U steel appliances The door along the contour is equipped with a water-cooling circuit.
To clean a cast iron boiler from ash and ash, you will need a poker. Steel heat generators are equipped with rotating grate bars, mechanically controlled - as a result, to clean the stove you do not need to open the door to the firebox.
The design of solid fuel boilers varies. These devices are:- single-circuit;
- double-circuit.
classical (traditional) and gas generator (pyrolysis). The latest devices consist of two chambers located one above the other, which are separated by nozzles.
Solid fuel is placed in the upper part, but it does not burn immediately. Thanks to the pyrolysis process, the wood is initially dried and at the same time the air is slightly heated. As a result, efficient heat exchange is ensured. Pyrolysis boilers are equipped with a ventilation device, which not only facilitates quick combustion, but also minimizes harmful emissions into the atmosphere.
If such a bunker is filled completely, the next loading will only be required after a few days. The warranty period for these devices is about 10 years. But if the operating conditions are observed, the boiler can last a much longer period.
Safety of the heating system
The main point when a solid fuel heating boiler is installed is to prevent overheating of the heating supply structure. Since the heat generator cools down very slowly, it is necessary to avoid situations where the temperature reaches the maximum limit. This is especially true for metal-plastic and plastic elements. When the temperature exceeds 100 degrees, they can melt and the heating equipment may become unusable.
You also need to be extremely careful when draining hot water (to prevent overheating) into the sewer system if it is equipped with plastic pipes that can become deformed.
The need to install a chimney
Effective operation of a solid fuel boiler is impossible without the correct choice of installation location for the chimney, which must withstand high temperatures without problems and not be subject to corrosion. It cannot be less than 4 meters in height, and 18 centimeters in diameter.Installation of the boiler and smoke exhaust system should only be carried out by professionals. But the customer of installation services does not bother to study the relevant information in order to assess the quality of the work. After installation is completed, the boiler ash pan must be regularly cleaned of accumulated ash and slag, which reduce the efficiency of the equipment.
Video about a solid fuel heating boiler:
It is extremely difficult to imagine a comfortable home without a heating system, because the presence of heat in the room depends on its presence and functionality. Such a system necessarily includes a heating boiler, the main task of which is to heat the coolant to a given temperature. There are many types of equipment, the main difference of which is the type of fuel used, which determines the principle of operation of the device. According to statistics, the most common heating boilers are solid fuels, which are considered one of the first heating devices.
How does such a unit work?
Solid fuel devices use various types of solid fuel for their operation. These are firewood, coal, oil shale, peat, etc. The boiler operating cycle can be divided into three phases. Let's look at each of them in more detail.
Stage #1 - ignition of the boiler
The cycle begins with ignition, which is characterized by a sharp increase in temperature on average from 40°C to 600°C in 5-10 minutes. The temperature values of the combustion heat exchanger begin to increase, which depend on the system parameters and can range from 40°C to 70°C. At a minimum, a thermal shock is possible on the heating system as a whole and on the heat exchanger itself. The latter, especially those made of cast iron, will not be able to withstand such conditions for long and will burst. If the circulation rate of the coolant is low and heating occurs quickly, boiling of the liquid may occur, which will lead to thermal and hydraulic shock to the heating system. The most vulnerable to it are plastic pipes. At this stage, the pipes begin to warm up, but the air in the room is still cold.
Coal, firewood, pellets, peat, etc. can be used as fuel for solid fuel boilers.
Stage #2 - warming up the coolant
The temperature in the furnace continues to rise and reaches values of 1300°C for coal boilers and about 1000C for wood boilers. The coolant continues to warm up. At this stage, control is important, otherwise it can heat up to the maximum boiler temperature, which remains 95°C, and this is already dangerous.
Regulation is carried out using a valve that controls the air supply. Optimal temperature must be maintained until complete combustion of the fuel. During this phase, the pipes in the room become hot and the air warms up.
Stage #3 - fuel burnout
At the end of the boiler operating cycle, the fuel is completely burned out and smoldering coals are formed. The temperature drops to 600°C-400°C, which are considered the most comfortable for the system. The coolant slowly cools down, and the air in the room also begins to cool down little by little. After smoldering coals have formed, the cooling process of air and coolant immediately accelerates.
Having examined all phases of operation of a solid fuel boiler, you can clearly see its main feature - temperature cycling. It is due to the need to add a new portion of fuel from time to time in order to minimize fluctuations in coolant temperature. To a greater extent, this problem is solved in automatic boilers, where there is an automated fuel supply and burner fan pressure. The rest need constant human monitoring and timely replenishment of fuel.
How does a solid fuel boiler work?
You need to understand that a solid fuel boiler is a modular structure assembled in a steel casing, which includes the following components:
- Combustion chamber equipped with a door. This is where the fuel combustion process takes place.
- Grate. Fuel is placed on it and evenly distributed. After it burns out, the resulting ash is poured through special holes into the ash pan.
- Cleaning hatch. Designed for cleaning the boiler.
- Heat exchanger. It is a structure that transfers energy from a heated coolant to a cold one. Most often this is a barrel through which smoke pipes are laid. Gases passing through them heat up the coolant circulating in the heat exchanger.
- Thermostat for the boiler, allowing you to regulate the rate of fuel combustion.
In addition to the above mandatory elements of the device, they can also be equipped with equipment that significantly facilitates their operation. For example, such as draft regulator, gas burners, thermostatic valve. Read on for more details about each of them.
A schematic diagram of the structure of a solid fuel boiler is shown in the figure.
Traction regulator indispensable for adjusting the temperature inside the supply pipeline and controlling air access into the combustion chamber. When heated, the device expands and can affect the damper, opening or, conversely, closing it when the equipment cools. Boilers equipped with such a regulator can operate in automatic mode. The device is installed on the front wall of the equipment. When starting the boiler, it is regulated so that the temperature does not fall below 65°C and does not rise above 90°C.
Gas-burner runs on natural or liquefied gas and provides many advantages:
- Ignition takes only a few seconds.
- Safe to use.
- Simple design, which ensures the reliability of the equipment.
- Possibility of combination with different types of boilers.
- Operation in enclosed spaces.
Thermostatic valve designed for emergency heat removal from the boiler in case of overheating. To cool the apparatus, the hot coolant is drained from the system, rather than cold water being pumped in its place. The cooling circuit for steel equipment is installed inside the device, and for cast iron equipment - on the supply.
Using a gas burner allows you to get almost instant ignition and safety in using the device. This burner can be installed in any type of boiler
Types of devices based on the principle of fuel combustion
There are several types of heating boilers that run on solid fuel. Let's look at them in more detail.
Option #1 - classical combustion boilers
The equipment has a large firebox in which fuel combustion occurs naturally. The design, as a rule, contains a coolant temperature sensor-controller with the function of mechanical adjustment of the air damper. Such boilers are characterized by extreme simplicity of design, which makes their cost relatively low and operation very easy. In addition, they are very unpretentious to the type and quality of fuel and can be heated with coal, wood, briquettes, etc. However, classic devices also have disadvantages:
- Short burning time. As practice shows, one fill of fuel can be enough for a maximum of eight hours of operation.
- Difficulty in automating heating modes.
- Lower efficiency than other types of solid fuel boilers, which leads to high fuel consumption.
- A suboptimal combustion process leads to increased ash content.
Of all the listed disadvantages, the problem of frequent fuel loading can be leveled out. It is partially solved by installing a heat storage tank, which accumulates heat and thereby smoothes out temperature changes in the coolant. The tank is a metal container with good thermal insulation. Its volume is calculated depending on the capacity of the heating system and the power of the equipment. However, its presence means additional costs and the risk of system breakdown.
Traditional classical combustion boilers are very undemanding in terms of fuel. However, due to design features their efficiency is lower than that of other devices, so they are characterized by high ash content and high fuel consumption
Option #2 - long-burning devices
These boilers do not have the disadvantages described above. There are two types of such devices - pyrolysis and “smoldering” type devices. Long burning differs from the classic one by the presence of two combustion chambers. The fuel begins to burn in conditions of oxygen deficiency. When exposed to high temperatures, it begins to emit wood gas, which is a mixture of carbon monoxide, propane, methane and hydrogen. This process is called pyrolysis. At the end of this process, the fuel enters the second chamber, where it is burned with excess oxygen. As a result, the system efficiency increases to 90%.
The fuel burns with virtually no residue, and the ash has to be removed every few days. One download lasts an average of 12 hours. Average fuel consumption is low. The advantages of pyrolysis devices also include:
- Possibility of maintaining a given coolant temperature.
- Work for in various forms solid fuel: coal, briquettes, firewood.
- Wide possibilities for automating combustion control systems.
The disadvantages of the system include the higher cost of equipment, energy dependence and demands on the level of fuel moisture.
Pyrolysis boilers are distinguished by the presence of two combustion chambers. In the first, pyrolysis occurs, that is, the release of wood gas, and in the second, the actual combustion of the material occurs.
Devices of the “smoldering” type are distinguished by the presence of a water jacket built around the entire perimeter. The combustion process proceeds like a candle - from top to bottom. The process of slow smoldering of the upper part of the fuel and the large volume of the combustion chamber, and in some cases it reaches 100 liters, allows the combustion process to be extended over a long time.
The design of smoldering boilers is such that fuel ignited from above can burn without adding a new portion for quite a long time, sometimes up to several days
There are models that can “last” on one coal bed for five days. To this undoubted advantage of the device we can add a slightly lower cost than pyrolysis boilers. However, these devices are very demanding on fuel. It must be either top quality coal or wood with a moisture content of no more than 20%. It is also necessary to pay attention to the resin content in the fuel; if it is high, frequent cleaning of the system is inevitable and the automation will fail faster.
From our next article you will learn what types of braces there are, what are their pros and cons: .
Which brands should you prefer?
The most famous manufacturers of solid fuel boilers of the classical combustion type are:
- SAS. The company has more than 30 years of experience in the production of heating equipment. Produces more than nine models of boilers for various purposes.
- Aton. The manufacturer produces three series TTK devices V, TTK and TRADYCJA. The first two modifications are completely energy independent, the latter is equipped automatic control and supercharging.
- Galmet. A large number of variations of varying power, designed to work on coal, firewood, briquettes, as well as combined models.
- SIME. The company offers two types of devices. The Solida brand range includes six boilers with power varying from 16 to 40 kW. The Solida Evolution model range is represented by five devices with a power range of 23-67 kW.
The average cost of such devices depends on the power and starts from 20 thousand rubles.
The most well-known manufacturers of pyrolysis boilers include:
- ATMOS. Models are produced for working on coal, wood or coal, pellets, combined, with the ability to install a gas burner.
- VERNER. The company produces VERNER V brand equipment, classic pyrolysis devices designed to work on biomass. In terms of power, there are two modifications: VERNER V45 and VERNER V25.
The cost of devices starts from 40 thousand rubles.
The most popular manufacturers of “smoldering” type devices:
- Stopuva. Models with power from 10 to 40 kW are available, burning wood or coal and firewood.
- Candle. Variations of different power are produced, using firewood, wood chips, peat, and briquettes as fuel.
The price of equipment starts from 40 thousand rubles.
Solid fuel boilers are reliable and practical devices. They make it possible to use almost any type of fuel, which is very convenient. The main disadvantage of classical combustion devices is the temperature differences of the coolant. However, long-burning modifications do not have it. This equipment can be fully automated, which makes it possible to use the device with maximum convenience.