Wood heating system for the house. Long burning wood boilers

20.10.2023

There are boilers that run not only on solid fuel, but your “house in the village” may end up in a place where gas is not supplied, and there are power outages. In such a situation, a wood-burning boiler for heating is a real panacea. The main thing is to prepare firewood in advance - and you will be able to heat not only the house, but also the bathhouse or greenhouse. What are the advantages of such equipment and does it have any disadvantages, by what principle is the choice made, and what are the connection diagrams? Answers to these questions will be given throughout the article.

Firewood belongs to the category of solid fuel and can be used, along with coal, to maintain the operation of any stove intended for it, with the exception of pellet stoves. We all know that wood burns quickly, which is its main disadvantage. For a fireplace, for example, this does not matter much - the same thing applies when we are talking about a heat source for the entire house, which must be heated uninterruptedly.

For this purpose, boilers have been created, the design of which is capable of maintaining combustion for as long as possible ( not 3, but 8-24 hours). In some units, for this purpose, control of fuel combustion is provided through a water circuit or an additional chamber, in others, an increase in the volume of the firebox is provided. But these are not all the features that can affect the quality and quantity of heat received.

Prices for popular models of solid fuel boilers

Solid fuel boilers

Distinctive features of the models

The combustion process in boilers of certain designs can differ fundamentally. In some, ignition starts at the top and moves down, in others it occurs in the opposite direction. There are models that work using the pyrolysis method (gas generator), when the fuel does not burn, but smolders. At the same time, it releases gas accumulating in the adjacent chamber, which, in fact, is the main coolant.

Pyrolysis models can support combustion up to 28-30 hours, and are very economical in terms of fuel consumption. However, the prohibitively high price most often forces the consumer to pay attention to conventional boilers with a water jacket - especially when there is no need for round-the-clock heating.
In general, with the correct calculation of power, with the help of one wood-burning boiler, you can easily heat a mansion with an area of 500 sq m and room height up to 2.7 m. The calculation is something like this: for 10 m2 – 1 kW.
If the model is double-circuit and will also heat water for household needs, the resulting power is added 20% . So, the number of circuits is one of the essential characteristics by which heating boilers are classified.

Note! For effective operation, the circuit must also include an element such as a boiler (provides indirect heating). This, of course, entails additional costs, but even when the boiler cools down, you will always have hot water.

The differences between the boilers also lie in the design of the firebox, which can be either vertically loaded or front-loaded. The first is often provided for in long-burning models, which can also use raw firewood. In this case, dry fuel is placed at the bottom, where it begins to burn, and wet fuel is placed at the top. While the lower firewood burns, the upper ones dry out.

The cost of a boiler is determined not only by its operating principle or power, but also by the degree of automation equipment. For example, in some variations there is a function of pumping the air necessary to maintain combustion and forcibly removing combustion products from the chambers.
The heating temperature of a wood-burning boiler, like any other, can be controlled and regulated, and they can also have a built-in storage tank. In this case, even with only one circuit, they can heat water not only for heating, but also for the hot water system.

Another thing is whether you need all these options, for which you always have to pay extra.

Prices for double-circuit wood boilers

Double-circuit wood boilers

Video - Which boiler is better?

What should be in the system

The set of characteristics: the design of the firebox, the number of chambers and circuits, the quality of the fuel, determine how long the boiler can operate without “refueling”. But most importantly, for the heating system you need to correctly arrange the equipment and choose the optimal connection diagram in which it will work most efficiently.

Table 1. Typical mistakes when piping a boiler.

Photo for clarity	A comment
	It is very important to choose the right pipes that will be connected directly to the boiler. Firstly, they should be steel, not polymer, since the coolant at the outlet has the highest temperature; Secondly, the diameter of the pipes must correspond to the calculation, and not be selected a size or two larger “just in case.”
	The second and very common mistake is trying to save money on installing a bypass line. Its main element is a thermostatic 3-way valve with a pump - or, as in the photo, a mixing group, which prevents the return of water from the heating network to the boiler. The valve has factory settings, thanks to which it does not allow cooled water to enter the system, but circulates it in a small circle through the boiler until it warms up. It opens only when the coolant reaches the set temperature. Note! This scheme allows you to avoid large differences in temperature values at the supply and return, which contributes to the formation of condensate in the boiler.
	The system must have a buffer tank, the task of which is to accumulate and distribute heat evenly. It will not allow fuel to be burned in vain - that is, it will make the network more economical.
	When heated, water tends to increase in volume, which can result in increased pressure in the pipeline. A safety element such as an expansion tank (hydraulic accumulator) is designed to compensate for this phenomenon.
	In addition to increasing volume, hot water intensively produces steam. Accordingly, excess air from the system must be discharged, for which an air vent is provided above the expansion tank.
	We have already mentioned that it is advisable to also include a boiler in the system. At the exit from the buffer tank, water flows through a 3-way valve, which, according to the thermostat command, can direct the flow either to the indirect tank, or, when the water in it is already heated to the desired degree, to the heating circuit. Thus, you will always have water at a stable temperature for your needs.
	The coordinated operation of such a multi-component system will be helped by regulating such a small but very valuable in functionality device as a controller. In accordance with the specified settings, it will automatically change the direction of the water flow, and also, to achieve a certain temperature, dose the mixture of cooled coolant from the return to the hot one.

Step-by-step boiler installation instructions

The selection and arrangement of equipment is not yet a guarantee of trouble-free operation of the system, because its elements still need to be installed correctly. And you should start with the arrangement of the boiler room, in which all this should be located. A short instruction in pictures will tell you what you need to pay special attention to.

Table 2. Correct step-by-step installation.

Steps, photo	Description
	The boiler is installed after repairs have been completed in the room where it will be installed. It is important that: non-combustible materials were used in the finishing; the foundation for the boiler was prepared; there must be an air flow in the room; An exit for the chimney pipe must be provided in advance in the wall or ceiling.
	When choosing a place for installation, you need to keep in mind that there must be a minimum of 700 mm between the walls and the rear and side surfaces of the boiler body. On the front side, this distance must be at least 1250 mm (if the unit is top-loading). If loading is done from the front, you must also add the width of the door to this distance.
	It is very important that the position of the boiler does not deviate from the vertical, so during installation you need to use a level. Place it on the firebox with the lid folded back.
	According to the boiler passport, check its equipment, which may vary depending on the manufacturer. Purchase all other elements necessary for installation in advance in accordance with the selected scheme.
	Naturally, you will need tools: adjustable, gas, socket and open-end wrenches, as well as screwdrivers of different sizes, a square and an angle grinder.
	FUM tape is wound onto the regulator rod and it is installed in its original place. Tighten the nut, set the desired temperature and fix it in this position with a screw.
	A little further than the combustion regulator there is a hole for installing the heating element regulator. If you don’t plan to install it, then simply screw a plug in there.
	Next, the heating element itself is mounted - or a plug instead.
	For ease of operation or routine maintenance of the system, taps are installed at the inlet and outlet of the coolant from the boiler.
	You assemble a pressure gauge, an air valve and a safety valve into one unit, which ensure the safe operation of the boiler and come with it. The group is placed in front of the shut-off valves.
	To connect the supply and discharge pipelines to the boiler, you need to make rotary pipes. It is better if the connections are welded rather than detachable.
	To ensure that the chimney pipe fits tightly and does not allow combustion products to enter the room, its landing site and all other connections are treated with sealant.
	Install a flexible tube onto the faucet installed at the very beginning, through which the hydraulic part of the boiler will be filled with water. Open all taps, raise the pressure to 1.3 atm, and check the tightness of the system. There shouldn't be any leaks anywhere.
	Now, in accordance with the instructions, you can load the firebox with wood and light it.

The installation process is presented only in general terms, since each boiler model has its own nuances, and the connection diagram may be different.

Prices for angle grinders (grinders)

Angle grinders (grinders)

Video - Heating boiler connection diagram

In order for your boiler to be as efficient as possible, it must be operated correctly. Here are the points you need to pay attention to so that the firewood burns longer:

When igniting the fuel, the damper on the boiler must be completely open;
Long burning mode is set only after heating up to +600 degrees;
The coolant at the outlet must have a temperature 65 and more degrees;
If the boiler design does not provide for the laying of raw firewood, its humidity should not exceed 20% ;

To avoid resin settling on the walls of the firebox and chimney, heat the boiler with hardwood firewood - acacia, birch, alder, aspen. And, by the way, the breed has a great influence on the amount of heat received;
Do not chop the firewood - the larger the pieces, and the closer to each other they are laid in the firebox, the longer they will burn;
To prevent logs from hanging, they should not be too long. Ideal size – combustion chamber length minus 5 cm.

Advice! You should not use flammable liquids for ignition - a dry splinter will be enough for this.

Steel or cast iron - which is better?

Solid fuel boilers are made from two types of metal alloys - steel and cast iron, and therefore there are ongoing battles on forums about which of these options is better.

Opinions, as usual, are the most contradictory, and it is simply impossible to make an unambiguous verdict here.

Let's still try to understand this issue, relying on the opinions of experts.

Table 3. Experts' opinion.

Evaluation criterion	Pros and cons
Weight and transportation	A boiler with a steel body is lighter, so it is much easier to transport and carry it by hand. Cast iron is generally very heavy, and also fragile. Such a boiler must be moved very carefully, since after an impact it may not survive to the first fire.
Maintainability	The most common problem that occurs with cast iron boilers is a burst section that needs to be replaced. And here you can expect difficulties associated with ordering it and waiting for delivery - as well as with finding a technician who can replace it so that in the future the boiler, which needs to be completely disassembled, does not leak. On a steel boiler, at most, you may need to weld a seam, and any welder can do this.
Price and durability	If we compare two models with a similar design and power, then the cast iron one will be twice or even three times more expensive. Manufacturers and sellers explain this by a longer service life, which many experts strongly disagree with. And even if so, then for the amount you need to pay for a cast-iron model you can buy at least two steel ones, which in total will amount to the same period. And it is still unknown how many times during the entire life of a cast iron unit you will need to change its sections. So here the advantage definitely goes to the steel boiler.
Efficiency	About the same. However, cast iron is more massive and retains heat longer, while steel, although it heats up faster, also cools down faster.
Difficulty of installation	A cast iron boiler is more complex in installation, and any connection error can cost it its “life.” So here too it loses to its steel brother.

Video - Which boiler to choose - steel or cast iron

From the above, it becomes clear that a steel boiler is easier to install and repair, has less weight and cost. And all this despite the fact that, with proper piping, it provides the house with heat and hot water in the same way as a cast iron one. The question suggests itself: “If there is no difference, why pay more?”

A solid fuel boiler is one of the most suitable household heating devices for creating a comfortable temperature in country cottages, private houses and cottages. Operation of classic wood-burning boilers does not require the consumption of electrical energy, natural or liquefied gas. The heating device automatically maintains the required temperature of the coolant by changing the height of raising and lowering the stove damper, which speeds up or slows down the combustion process.
Heating It is advisable to install a wood boiler in rural or urban non-gas areas that do not have an electrical supply network. The main type of boiler fuel is firewood, wood waste and pellets, which are granules of a certain size that are made from agricultural waste, woodworking waste, peat and bottom dry sediments.
Main distinctive advantages heating wood boilers are:

long period of trouble-free operation;
low cost of the device;
no electricity consumption;
cheapness of the fuel used.

A solid fuel boiler with a water circuit is a self-powered unit that can efficiently heat small apartments and fairly large areas.

Firewood, peat, pallets, coal and eco-peas can be used as an energy source.

The device is ideal for installation in a house that does not have a connection to a central heating system or gas mains.

The main feature of such units is the presence of a water circuit. They can be single-circuit or double-circuit. The former are only capable of heating the room, while the latter are capable of additionally preparing hot water for subsequent use.

Fuel is supplied manually or automatically, depending on the model. If it is automatic, then the boiler has a reservoir for storing raw materials. Fuel can be loaded into the system within a week without assistance.

Such models have a high price, so people prefer to choose a manually laid boiler.

One fill of fuel is enough for 3-4 hours.

To create an image of a solid fuel boiler with a water circuit, it is necessary to consider the principle of its operation:

Setting the required temperature in the coolant, supplying fuel.
Heating the heat exchanger in the water circuit.
The resulting thermal energy accumulates from the walls of the water jacket and the water is heated.
Regardless of the type of water circulation in the system (natural or forced), the house is filled with heat in a short period of time.

Types of devices

Each device has its own unique technical characteristics.

But all models can be divided into several types, depending on the type of combustion process:

Traditional. A distinctive feature is that the combustion process occurs from the bottom up. Fuel is loaded manually, combustion products are discharged through the chimney. The boiler does not require electricity to operate.
Long burning. Features - the combustion process occurs from top to bottom, fuel is added from above. The unit is designed for uninterrupted operation throughout the day without “topping up.” Due to their complex design, long-burning boilers have a high cost.
Pyrolysis. Features - the presence of two fuel chambers: the first is intended for the combustion of solid fuel, the second consumes the gas that was formed in the first. Advantages: high efficiency, minimum waste, environmental friendliness. But such boilers require special attention - they are only allowed to be installed in rooms with a humidity of 17-20%.
Universal. Features: operation on all types of solid fuel. If you change the burner, you can use liquid fuel. The models are equipped with a safety system that prevents spontaneous combustion or interruption of operation.

Advantages and disadvantages

Advantages:

high build quality, reliability and safety of equipment;
long service life - some models can last more than 10 years;
economical fuel consumption, low cost of units and raw materials;
versatility;
there is no need to carry out regular technical inspection;
combustion products are suitable for recycling.

Flaws:

wood-burning models have low efficiency - no higher than 80%;
the need to load fuel into manually fed models every 5-6 hours.

How to choose and what to pay attention to?

Power. Here the buyer should pay attention to the technical characteristics of the model he likes. Manufacturers indicate the maximum power, temperature, and estimated area.
Principle of operation. The main nuance is the number of contours. Units with one circuit only supply heat to the rooms, while units with two circuits additionally provide a person with hot water for domestic needs.
Possibilities. The devices are equipped with various systems to control the combustion process and record the required temperature. Some modern models are equipped with hobs on which you can cook food.
Fuel type and cost. Here it is better for a person to build on personal preferences and financial capabilities. Fuel in the form of coal and wood raw materials is considered economical.

Popular manufacturing companies

Solid fuel boilers from Russian, German, and Italian manufacturers are in high demand.

This is Viessman, Buderus, Ferroli, EVAN, Lemax. Below are models that deserve attention.

Rating of TOP 10 best models

Place	Name	Price
TOP 10 best solid fuel boilers with a water circuit
1		16,000 ₽
2		19,000 ₽
3		34,000 ₽
4		34,000 ₽
5		54,000 ₽
6		38,000 ₽
7		52,000 ₽
8		12,000 ₽
9		18,000 ₽
10		16,000 ₽

The best solid fuel boilers with a water circuit

Lemax Forward-12.5 13 kW

A distinctive feature of the model is the presence of a steel heat exchanger with a long service life. A single-circuit boiler is designed for heating residential buildings, cottages, and administrative buildings.

It does not require power from the electrical network.

The type of water heating system does not prevent the device from functioning normally.

Characteristics:

power - 13 kW;
Efficiency - 75%;
fuel - coal, firewood, coke;
Max. heat exchanger temperature - 95 degrees, water pressure - 2 bar;
presence of a thermometer;
type of fuel loading - vertical;
chimney diameter - 14 cm;
dimensions - 37x90x58 cm;
weight - 70 kg;
warranty - 3 years.

Advantages:

high level of safety and environmental friendliness;
impact-resistant heat exchanger, additionally protected by heat-insulating materials;
the body is made of 4 mm thick steel, which guarantees its strength and reliability;
easy connection of the unit to the chimney;
affordable price - from 14,900 rubles.

Flaws:

there is no system for cleaning the boiler;
poor ash pan adjustment.

Lemax Forward-20

Single-circuit boiler with vertical fuel loading. Thanks to its high power, it quickly warms up rooms in room and maintains the set temperature for a long time.

Attractive appearance allows you to install the device in any place and adapt it to the overall interior.

It is also possible to connect to a water heating system with natural circulation.

Characteristics:

power - 20 kW;
does not require electricity to operate;
combustion chamber type - open, control - mechanical, installation - floor;
Efficiency - 75%;
heat exchanger material - steel, max. temperature - 95 degrees;
fuel - coal, firewood, coke;
Max. water pressure - 2 bar;
equipped with a thermometer;
chimney diameter - 15 cm;
dimensions - 41x90x58 cm;
weight - 78 kg;
warranty - 3 years.

Advantages:

steel thickness is 4 mm, which affects the durability of the structure;
convenient download method;
efficient and fast heating of large rooms, the area of which exceeds 200 square meters. m;
environmental friendliness of fuel;
ease of installation and operation;
affordable price - from 18,900 rubles.

Flaws:

not detected.

ZOTA Topol M 20 20 kW

Non-volatile single-circuit boiler with front fuel loading. It is equipped with combustion doors that open horizontally and vertically, close with a lock.

The heat exchanger is combined with a removable damper, which makes the flue two-way.

Therefore, there is a significant increase in the heating area with prolonged heat transfer.

Characteristics:

power - 20 kW;
combustion chamber type - open, control - mechanical, installation - floor;
Efficiency - 75%;
type of heating elements - optional, their max. temperature - 95 degrees;
fuel - firewood, coal;
Max. water pressure - 3 bar;
presence of a thermometer;
chimney diameter - 15 cm;
dimensions - 44x84.5x97.5 cm;
weight - 140 kg;
warranty - 1 year.

Advantages:

good value for money - the buyer receives a powerful unit for more than 30 thousand rubles;
easy to use, easy to download;
the ability to install a gas burner in place of the screw door;
quick cleaning of the chamber and chimney due to its simple design.

Flaws:

the need to call a technician if you decide to add other functions to the unit;
fast fuel consumption: anthracite - 1.3 kg/h, coal - 2.5 kg/h, firewood - 3.3 kg/h.

Carbon 20 20 kW

Single circuit top loading model. Capable of heating rooms up to 200 square meters. m. Does not require connection to electrical network.

Has a spacious fuel tank, autonomous loading system.

If you use the device correctly, you will be pleased with its functionality and durability.

Characteristics:

power - 7-20 kW;
combustion chamber type - open, control - mechanical, installation - floor;
Efficiency - 80%;
heat exchanger material - steel, type - optional, temperature - 65-95 degrees;
fuel - coal, consumption - 5.6 kg/h;
Max. water pressure - 3 bar;
presence of a thermometer and pressure gauge;
chimney diameter - 15 cm;
dimensions - 46.5x97x105 cm;
weight - 176 kg.

Advantages:

long and stable combustion;
easy cleaning of the boiler;
a single load of coal is 24 kg, and it lasts for 4-6 hours;
each structural part is made of durable steel, which determines its service life;
environmental friendliness and safety.

Flaws:

requires a certain type of fuel - fine coal;
the internal part of the structure is affected by corrosion over time due to the formation of sulfuric acid condensate;
high cost - from 40,000 rubles.

Protherm Beaver 20 DLO 19 kW

A single-circuit boiler is characterized by high performance, the ability to heat a larger area, the presence of a two-pass cast iron heat exchanger, low electricity requirements.

The presence of 4 sections allows you to change the performance and complete the device to the optimal option.

Characteristics:

power - 19 kW;
combustion chamber type - open, control - mechanical, installation - floor;
Efficiency - 90.2%;
fuel - coal, firewood;
heat exchanger temperature - 30-85 degrees;
Max. water pressure - 4 bar;
chimney diameter - 15 cm;
dimensions - 44x93.5x64 cm;
weight - 230 kg;
warranty - 2 years.

Advantages:

simple durable design made of cast iron;
the presence of a spacious combustion chamber;
after prolonged use, the unit retains its appearance and performance;
fast heating of rooms, maintaining the set temperature for a long time.

Flaws:

the massiveness of the boiler, making it difficult to move and install;
high cost - from 60,000 rubles.

Kentatsu ELEGANT-04 27 kW

The floor-standing single-circuit boiler is suitable for installation in rooms with any circulating heating system. Does not require connection to the electrical network, can act as an independent heat source or as an addition to another type of boiler.

All structural elements are made of cast iron, with the exception of control levers.

The model is worthy of attention and has good value for money.

Characteristics:

power - 27 kW;
combustion chamber type - open, control - mechanical, installation - floor;
fuel - coal, firewood;
coolant temperature - 90 degrees;
Max. water pressure - 4 bar;
presence of a thermometer;
chimney diameter - 18 cm;
dimensions - 45x94.7x70.9 cm;
weight - 198 kg;
warranty - 2 years.

Advantages:

easy operation and cleaning of the chamber and chimney;
ease of temperature adjustment;
fast heating, efficient heat transfer;
supplied assembled;
affordable price - from 38,000 rubles.

Flaws:

not detected.

Buderus Logano S111-2-16 16 kW

Single-circuit boiler with top-loading fuel that does not require electricity to operate. The structure is made of impact-resistant steel, effectively maintaining heat in all rooms.

The power of the unit is sufficient for heating private and country houses, apartments, offices, and service premises.

Characteristics:

power - 16 kW;
combustion chamber type - open, control - mechanical, installation - floor;
Efficiency - 76%;
fuel - coal (recommended by the manufacturer), coal and wood briquettes, firewood, coke;
fuel consumption - 6.4 kg/h;
coolant temperature - 65-95 degrees;
water pressure - 3 bar;
equipped with a thermometer and pressure gauge;
chimney diameter - 14.5 cm;
dimensions - 60x87.5x73 cm;
weight - 160 kg;
cost - from 54,000 rubles.

Advantages:

duration of the combustion process;
easy access to the fuel supply chamber;
durable design that is not subject to any damage;
easy installation, delivered assembled.

Flaws:

not detected.

EVAN WARMOS TK-12 12 kW

Single-circuit steel boiler designed for heating small spaces. Distinctive feature consists in the cylindrical shape of the body, which ensures the greatest strength of the unit.

The firebox is equipped with a wide door, making it easy to load fuel and then clean it.

Characteristics:

power - 5-12 kW;
combustion chamber type - open (capacity 50 l), controls - mechanical, installation - floor;
heated area - 80 sq. m;
Efficiency - 70%;
fuel - coal, firewood, peat, max. firewood length - 55 cm;
coolant temperature - 95 degrees;
water pressure - 2.5 bar;
equipped with a thermometer;
chimney diameter - 11.4 cm;
dimensions - 44x62x93 cm;
weight - 59 kg;
warranty - 1 year.

Advantages:

high level of strength and durability;
rapid heating of the room, with long-term maintenance of the set temperature;
good value for money - the buyer purchases high-performance equipment at a very reasonable price (from 15,600 rubles);
ease of cleaning and maintenance.

Flaws:

not detected.

Teplodar Cooper Praktik 20

The single-circuit steel model is designed for heating rooms with an area of up to 200 square meters. m. Heat exchanger made of steel is designed for a long service life and maximum heat transfer.

The main difference is the simple design with an attractive design.

Characteristics:

power - 20 kW;
combustion chamber type - open, control - mechanical, installation - floor;
type of heating element - preinstalled, power - 6 kW, temperature - 50-95 degrees;
water pressure - 1 bar;
equipped with a thermometer;
chimney diameter - 15 cm;
dimensions - 49x69x69 cm;
weight - 82 kg;
warranty - 3 years.

Advantages:

low price - from 18,000 rubles;
spacious firebox;
fast heating;
the ability to install a draft regulator;
it is permissible to insulate the side walls;
high build quality, durability and strength.

Flaws:

not detected.

Teplodar Kupper Praktik 14 14 kW

The single-circuit boiler has become famous for its durability and low electrical requirements. The model is different from previous power indicator and maximum heating area - up to 140 sq. m.

The attractive appearance allows you to install the structure anywhere in the room.

Characteristics:

power - 14 kW;
chamber type - open, control - mechanical, installation - floor;
type of heating element - preinstalled,
material - steel,
power - 6 kW,
temperature - 50-95 degrees;
fuel - coal, firewood, peat briquettes;
water pressure - 1 bar;
presence of a thermometer;
chimney diameter - 11.5 cm;
dimensions - 42x65.5x63 cm;
weight - 68 kg.

Advantages:

affordable price - from 15,000 rubles;
excellent for heating private and country houses;
simple use, easy installation;
quick cleaning of the chamber and chimney;
maintaining cleanliness in the room.

Flaws:

not detected.

Conclusion and conclusions

Solid fuel boilers with a water circuit are a good buy for people whose house is not connected to central heating. The units will also be an excellent solution for heating country houses.

If you choose wisely, you can get an effective and high-performance device with a long service life.

Useful video

From the video you will get an overview of a solid fuel boiler with a water circuit:

In contact with

Long-burning wood-burning boilers are in demand among summer residents and owners of cottages intended for year-round use. Before installation, you should understand the features, pros and cons of this type of heating in a private home.

Long-term combustion boilers using wood do not require frequent maintenance, and the cost of each 1 kW/h. thermal energy is several times lower than when using liquid fuel or gas units.

A solid fuel wood boiler is well suited for homeowners who have the opportunity to purchase good quality firewood

In general, the operating mechanism is based on long-term smoldering of fuel due to limited air supply - as a result, the filling lasts approximately 80% longer than when operating a solid fuel boiler of the so-called classic type.

Pros and cons of wood-burning boilers for long-burning fuel

Advantages:

no need for frequent refueling - depending on the chosen model, you need to add firewood into the combustion chamber from once every 3-4 hours and up to 12 hours;
possibility of using different types of fuel and their combination;
In most cases, the boiler operates autonomously and does not require connection to other communications;
relative cheapness of fuel.

Solid fuel boiler in a private house

Flaws:

the cost is higher than classic boilers;
due to the low calorific value of firewood, the efficiency is from 70 to 89%;
There is no mechanism for regulating the temperature regime.

Another important disadvantage is the inability to operate heating equipment without human intervention

Advice. Wood-burning boilers with small combustion chambers are mainly purchased for summer cottages and private cottages. Heating efficiency can be increased by increasing the combustion chamber, but at the same time the dimensions of the boiler itself will also increase.

Varieties by mechanism of action

Heating unit with extended firebox
The simplest and most common type of wood heating. The main difference from standard solid fuel units is their elongated shape with an elongated firebox. Directly into the combustion chamber after ignition, air is supplied in a dosed manner, due to which the operating time on each load of firewood is significantly increased (up to 6–8 hours).

Solid fuel boiler with extended firebox

Top burning model
Unlike standard wood-fired boilers, which are ignited from below, in the chambers of top-combustion boilers, fuel is burned under the influence of a burner moving from above and slowly descending down.
Pyrolysis boiler
The gas generator or pyrolysis unit has a more complex operating principle and design compared to the two previous models, due to which it can operate continuously for up to 12 hours on each fuel fill. In the combustion chamber, the wood does not burn in it, but smolders very slowly, in turn releasing gas. It is discharged into the lower chamber compartment, where it is burned under the forced supply of oxygen, releasing additional heat.

Top combustion solid fuel boiler

The most popular units for private properties

Different models of wood boilers differ from each other:

dimensions of combustion chambers;
type of construction;
material of manufacture.

The heat exchanger is often made of steel or cast iron. At the same time, cast iron will last longer than steel, it takes a long time to cool down, but can collapse under sudden temperature changes. Steel is heat-resistant, but can be subject to corrosion and will last on average about 10–15 years.

For country heating, simple single-circuit models are most often installed; for houses with year-round living, it is rational to install a double-circuit boiler. In the latter case, one circuit will provide heating, while the second will provide hot water supply.

Diagram: device of a pyrolysis boiler

Each individual unit has its own special technical characteristics, averaged data:

power about 100 kW;
coolant temperature at the outlet is 80 degrees, at the return - at least 50 degrees;
working pressure on average 1 atm;
boiler weight up to 400 kg;
Duration of operation on one load of fuel is 10-12 hours.

Operation of the pyrolysis boiler

Attention! When buying a heating boiler that runs on wood, you need to take into account that most units were originally designed to burn brown or hard coal. Their technical data sheets indicate the power and burning time of one bookmark based on operation on coal. Therefore, it is necessary to separately calculate the power and combustion time of the fuel if the heat generator runs on wood.

How to properly organize heating

In private cottages intended for year-round use, long-burning boilers equipped with heat exchangers are embedded in the heating system. The coolant carries the thermal energy obtained from burning wood to the radiators.

Attention! If a circulation pump is used in an autonomous system, it is necessary to make sure that the boiler heat exchanger can withstand the operating pressure of the entire system.

In small dachas with 1-2 rooms, there is no need for an autonomous heating system; it is more rational to use a convector stove of the Buleryan type. For models operating on the convection principle, the walls of the fireboxes consist of open metal tubes that are welded to each other in a vertical position.

House heating system using a solid fuel boiler

During the combustion of wood, heated air rises through the tubes due to the action of convection, and cold air comes in its place.

Fuel selection

You can place a long-burning wood-burning boiler both in the house and in an equipped boiler room or in a small separate extension to a private cottage. In this case, it will be necessary to allocate a separate place for fuel: wood, coal, peat, etc.

The most popular type of fuel is often waste from the wood processing industry. But this type of fuel is low-calorie, so it requires high consumption.

Wood is the most popular type of fuel for a home boiler room

The choice and degree of moisture content of the raw material will directly determine its calorific value. The fuel with the highest productivity is dry firewood, the quality of which should ideally be the same high from purchase to purchase. The maximum fuel length is 40 cm.

Important installation features

The weight of wood-burning boilers reaches several hundred kilograms, so before installation you need to make sure that the floors can withstand the load. For durable floors, a cast iron product is suitable; in other cases, it is worth considering the option of purchasing a boiler made of steel, which will weigh several times less.

At the place where the unit is planned to be installed, a concrete pad is usually installed (its thickness varies from 100 to 150 mm).

For the smooth operation of the boiler, its correct installation is very important.

Non-volatile boilers use so-called mechanical thermostats. If the model has a fan designed for forced air supply, as well as an electronic control system, then a power supply will be required.

It is important to take into account that during power outages, operation will be very difficult.

Conclusion

Long-burning boilers deserve special attention when choosing heating equipment for private houses and cottages. The most effective are pyrolysis units, which have the highest efficiency of 97% and a long service life without refueling.

Placing a solid fuel boiler

Before purchasing, you should also decide on the material of manufacture, the required volume of the firebox, prepare the boiler room or equip a place for the boiler in the house. Separately, you should take care of choosing high-quality fuel - dry firewood must be prepared in advance, and a separate place is allocated for its storage.

How a pyrolysis solid fuel boiler works: video

Long burning boiler: photo

With a limited choice of energy resources, there may be no alternative to heating with wood at all. It is important to purchase a suitable wood-burning boiler and understand the features of its operation. We will tell you about these heating units, from choosing the right type to installation issues.

Main types of wood boilers

The arsenal of heating equipment is constantly replenished with new, more advanced products, but nothing radically new has been invented among solid fuel boilers. In an attempt to increase efficiency, designers improved the design one way or another, which is why several varieties appeared with a number of characteristic features:

1. Complex Z-shaped firebox or its division into 2 combustion chambers. Such boilers are designed for long-term combustion and the most complete combustion of the released pyrolysis gases.

An example of the design of a long-burning solid fuel boiler: 1 - boiler automation; 2 - loading door; 3 — primary air supply; 4 — secondary air supply; 5 - ash pan; 6 - combustion of pyrolysis gases; 7 - pyrolysis of solid fuel; 8 - heat exchanger; 9 — fan-exhaust fan

2. The presence of water-filled grates and/or jackets. It is believed that in this way the coolant absorbs up to 90% of the combustion heat, but in practice, good wood-burning boilers with an efficiency above 80% are already very rare.

3. Form of organization of blowing. By reducing the incoming oxygen, the combustion duration can be greatly extended, maintaining the water temperature within specified limits. Usually implemented through a manual or controlled damper; if the draft is not strong enough, a boost fan can be used. The damper is usually controlled by digital automation, which controls the temperature of the water in the supply pipe.

4. Type and design of heat exchanger. On the one hand, there is a race to maximize surface area for more efficient heat removal, and on the other, for durability and reliability. In the first case, we have cellular boiler-type heat exchangers, highly efficient, but problematic to clean and repair/replace. On the other hand, simple tubular coils made of cold-drawn seamless pipe are hard to argue with the classics.

5. Availability of insulation. The need for a mineral-filled casing is determined by the installation location. If it makes no sense to waste heat outside, then for a garage or workshop, a non-insulated boiler can be a good heating method.

There are also differences in the type of fuel, horizontal and vertical location of the shaft, as well as the firebox material. Chambers and coils made of cold-rolled low-carbon steel are simple and unpretentious, but are susceptible to scale formation. Coils and water-filled jackets made of cast iron are the most durable and are not subject to scale formation, but require special piping due to their high sensitivity to thermal shock.

Equipment power

Ultimately, what is important for a boiler is not so much the details of its internal structure, but the main performance indicators, which were achieved using a number of engineering innovations. The most important and determining parameter of the boiler is its rated instantaneous power. The heat capacity of different types of fuel is different, as is the case with different types of firewood; the manufacturer cannot accurately predict it and calculate the rated power in a particular operating mode.

Power is determined by two indicators. By the volume of the firebox one can judge the mass of the filling. On average, it is believed that for every kilowatt of power of a wood-burning boiler there is 2.5-3 liters of combustion chamber volume. Having received the instantaneous value of the power released during combustion, it is possible to predict what part of it can be absorbed by the heat exchanger at different operating temperature conditions. Typically, absorption is deliberately made higher than the calculated heat release under combustion conditions close to optimal, but this approach is fraught with troubles.

The fact is that all wood-burning boilers suffer from a common disease - the formation of tar due to the high humidity of the burned wood. Condensation only occurs when the temperature difference is high enough. Thus, the formation of build-up on the economizer or secondary heat exchanger can stop when the coolant is heated to 40-45 ºС. The point here is that if you load the boiler halfway, its power will not be enough to properly heat the walls and heat exchangers, which is why the equipment will simply “leak.”

Chimney device

The main impact of condensation of water vapor from firewood falls on the chimney system. The length of the pipe is large, the temperature difference (especially outside) is very high. There are two approaches to solving this problem.

The first is to install inspection outlets to drain condensed moisture. Such outlets should be located at the lowest point of each rotating segment, starting from the last vertical section and ending with the boiler connection point. The disadvantage is that the water drainage tubes periodically need to be cleaned and cannot be of significant length with a small diameter.

Such problems do not arise with brick chimneys or asbestos-cement pipes in the lining. The difficulties of constructing such chimneys are obvious, but they can also be circumvented by using more expensive materials. We are talking about insulated sandwich pipes made of stainless steel with a mineral filler. For a chimney installation today this is the best option. To summarize: condensation does not form only in insulated chimneys.

System inertia

Another disadvantage of a solid fuel boiler is hidden in the cyclical nature of its operation and the inability to independently replenish fuel reserves. Because of this, either a high heat capacity of the house structure itself is required, or solid insulation, close to a passive house, or a way to store a reserve of heat for the period of cooling of the system.

Since the volume of the heat exchanger itself in the boiler is small, the displacement of the system can be increased mainly by increasing the diameter of the pipes. Another alternative of this kind is the installation of a heat accumulator. With the right approach, it is possible to realize heat accumulation only after heating the main system, which will help speed up the heating of the house and solve the problem with condensation.

Underfloor heating systems have their own high inertia, which increases with the thickness of the accumulating screed. With a thermal cut-off under the floor, this can be a truly long-term heat source. With a sufficiently thick layer, even the use of water at a higher temperature will not cause discomfort and thermal zebra, but along with the inertia of the system, the time it takes to reach the operating mode increases. On the other hand, connecting a heated floor to a wood-burning boiler requires a rather complex piping that prevents overheating of both the boiler and the pipes in the floor.

Automation and piping of wood-burning boilers

As already mentioned, the boiler power can be adjusted only by changing the amount of oxygen supplied. This system works most efficiently and accurately in pyrolysis-type mine boilers using wood or briquettes.

The main automation complex includes an electronic control unit, a fan, an electrically driven draft regulator and a thermocouple tightly wound to the supply pipe. All these components are sold both individually and in sets for a specific boiler model. On average, all automation costs about 4-5 thousand rubles. We should separately mention the importance of having protection against falling dampers and sealing grooves on the loading and inspection hatches, chimney, and draft stabilization system.

For solid fuel boilers, a number of other types of protective devices are provided, installed in the hydraulic piping. Among the absolutely mandatory ones are a circulation pump and protection of the firebox from overheating - a safety group for relieving excess pressure. Please note that the outlet of the relief valve must be turned towards the wall or equipped with a hose so that when activated it does not injure anyone present. Safety requirements may require the installation of a chimney bleeder valve to stabilize draft and combustion; it is mounted immediately at the outlet of the boiler or immediately before the final vertical section.

Connection diagram for a solid fuel boiler with a heat accumulator: 1 - chimney; 2 — thermostat; 3 - security group; 4 — air separator; 5 - circulation pump; 6 - heat accumulator; 7 - three-way mixer; 8 — weather-dependent automatic; 9 — heating radiator; 10 - circulation pump; 11 - check valve; 12 — expansion tank; 13 — protection against dry running; 14 — make-up valve; 15 — overhead temperature sensor; 16 - solid fuel boiler

For cast iron boilers, it is practiced to install a two-way valve that mixes water from the hot outlet to prevent cold water from entering the heated firebox. When installing a heat accumulator, a three-way electric valve is added, which starts the supply of heat to the tank only after the main composition has warmed up. Control is carried out based on the return temperature, the additional circuit is turned on 7-10 ºС before the cut-off temperature is reached. In this aspect, control units with a PID controller are most preferable.

Installation, connection

The boiler is installed on a concrete pedestal, the height of which is determined by the equilibrium of the hydraulic system. Ideally, the coolant in the boiler should be under the highest pressure compared to other sections of the pipeline. The position of the boiler is also determined by the direction and point of connection of the chimney. Its connection can be either vertical (from above) or horizontal (from behind or from the side).

It is recommended to use only steel or copper pipes in the boiler piping; for plastic there is too great a risk of overheating. The section of the supply pipeline 3-5 meters from the boiler is also traditionally made of metal. The connections can be welded, or if the necessary equipment is not available, they can be threaded using tow and anaerobic sealant.

The boiler must be configured taking into account the low heating rate and high inertia. The operating temperature of the coolant is usually maintained within 50-65 ºС. In this case, the reverse hysteresis temperature should be slightly higher than the maximum at which the boost completely stops. This is necessary so that ignition begins long before the water in the system cools down more than it should.