How to choose a solid fuel double-circuit boiler for long burning

The best solid fuel boilers for long burning

At its core, long-burning solid fuel heat generators are classic boiler plants that use the principle of upper combustion. That is, only the top layer of fuel is burned, and the air distributor, which descends as the fuel burns out, controls the flow of oxygen.

Stropuva S40U

4.9

★★★★★
editorial score

97%
buyers recommend this product

See review

A classic single-loop industrial long-burning plant with an open chamber can use wood, briquettes or coal as fuel. Up to 50 kg of briquettes are easily placed in the combustion chamber of the device, which is enough for 72 hours of continuous operation.

The efficiency of the model is at the level of classic gas installations - 85%, which is quite good. 40 kW power is enough for heating premises up to 400 m2.

Advantages:

• High power.
• Long period of work on one load.
• Energy independence.
• Operational safety.

Flaws:

• Steel heat exchanger.
• High cost - 116 thousand.

A very good, and most importantly, energy-efficient model for heating industrial premises.

Heiztechnik Q Plus Comfort 45

4.8

★★★★★
editorial score

95%
buyers recommend this product

The reliable two-section copper is intended for burning of wood, coal and waste of their production. The main difference from analogues is the presence of volatile and highly technological automation that fully controls the combustion process. Also, the model independently selects the intensity of combustion corresponding to the load, type of fuel and operating conditions.

Another feature of Heiztechnik Komfort is the use of horizontal water columns and a partition separating the sections from each other in the design. This solution significantly increases the efficiency of the equipment and reduces the risk of corrosion. The power of the unit is 45 kW, which is enough to heat residential and industrial premises, ranging from 150 to 450 m2.

Advantages:

• Ability to work in semi-automatic mode.
• Automatic control of burning intensity.
• Versatility.
• Sufficiently high efficiency (83%).

Flaws:

The price is over 137 thousand.

An excellent solution for efficient heating of residential and industrial premises up to 450 m2.

Candle S-18

4.8

★★★★★
editorial score

92%
buyers recommend this product

See review

Candle S-18 is the brightest representative of long-burning solid fuel boilers with front loading and top burning fuel, which can be used as wood, briquettes and woodworking waste (wood chips, sawdust). Depending on the type of fuel and operating conditions, the continuous burning time on one tab varies from 7 to 36 hours.

Power given models is 18 kW - this is enough to heat a room up to 180 m2.

Advantages:

• Unusually high efficiency - 93%.
• Good power.
• Complete energy independence.
• Compact body with a diameter of 57 cm.

Flaws:

High cost - about 96 thousand.

Candle S-18 is an almost “omnivorous” model that is perfect for heating a private house and will work out every kilogram of fuel to the maximum.

Suvorov K36

4.7

★★★★★
editorial score

87%
buyers recommend this product

A classic wood-burning boiler designed for space heating up to 360 m2. In this installation, the process of long-term combustion is implemented due to the precise control of the air supply to the combustion chamber. Smoldering provided a significant increase in the duration of work on one tab - from 6 to 20 hours. In addition, afterburning of pyrolysis gases is implemented in the boiler, which made it possible to achieve fuel savings of 50% and increase efficiency up to 90%.

Advantages:

• Energy independence.
• High efficiency.
• Possibility of using wood and peat briquettes.
• Stable maintenance of the set power for a long time.
• Possibility to connect a heating element to maintain the temperature.

Flaws:

• Steel heat exchanger.
• The price is not less than 111 thousand.

A trouble-free and energy-efficient boiler unit that can be used to heat residential buildings and industrial premises.

Comparison with electric and gas boilers

Many people who build a house away from the city are faced with a choice - to install an autonomous solid fuel, gas or electric boiler.

In order to compare these options with each other, you will need to consider three important parameters: connection cost, service safety and ecology.

Connection cost. Although a solid fuel boiler is not cheap, its operation has the lowest cost indicators among all compared models.

Why will they require the owner to provide a gas supply project, perform installation work on installing a boiler and a meter, and also pay for the connection.

Today, according to modest estimates, it will take 600 thousand rubles or more to supply gas to the house, perform installation work and obtain an operating permit. Installation of an electric boiler will cost much less, but also not cheap.

In most cases, such a connection will require a change in the power of the supply line to 380 V. This will also require significant financial injections for the reconstruction of the intra-house electrical networks and coordination with the RES.

At the same time, it is not a fact that the electricity supplier will agree to change the technical conditions.A solid fuel boiler does not require any approvals, and the funds spent on the purchase of boiler equipment will pay off in 2-3 years, while connecting to the gas network and installing a new power line will not be earlier than 6-9 years.

Service safety.

Everyone knows that gas boilers are the most dangerous, because in the event of a malfunction and separation of the flame from the burner, an explosive mixture can be created in the house.

Electric boilers pose a danger due to the possible occurrence of combustion centers in cable lines during overloads. In addition, an explosion of the steam-water mixture in the heat exchanger can occur if the circulation of the coolant is disturbed.

Any boiler needs to be serviced on time. Source

A solid fuel double-circuit boiler is also a source of a fire hazard situation, but the reality of its occurrence is much lower.

Since all structural units of the boiler unit are designed in such a way that the device was non-volatile. The built-in automatic protection, in case of violation of the permissible operating parameters of the boiler, cuts off the air supply to the furnace, after which the combustion process stops. In addition, today pallets are the safest fuel.

Ecology.

Here, in the first place are electric boilers, which have no emissions at all, followed by long-burning solid fuel double-circuit boilers and gas boilers complete the list, with the largest CO emissions.

Considering all the listed features of the types considered, it can be concluded that the most convenient and easiest to operate is an electric boiler, then comes a gas unit, and a solid fuel one is inferior to them in these requirements.

The cost of basic options for solid fuel boilers

Solid fuel boilers are produced for operation on various types of fuel. Most commonly used wood species, pressed wood chip pellets and various types of coal.

The cost of boilers is from 30 to 200 thousand rubles. Source

Recently, with the advent of biofuel from wood and agricultural waste, many users have switched to burning it in heating boilers. There are models that can run on any of these types of fuel.

The price of such modifications of heating units depends very much on the metal of the furnace space - cast iron or steel.

Wood-burning boilers today can be purchased for 55 thousand rubles. Coal units from 40 to 80 thousand rubles. Pellet double-circuit solid fuel boilers of long burning are the most expensive from 120 to 200 thousand rubles.

Open circuit with gravity circulation

This option is easy to perform even for a beginner. Here, water circulates in the system due to the difference in density of cold and hot liquids. According to the laws of physics, hot water begins to flow upwards (since its density is less), and then it cools down and returns to the starting point.

Despite the fact that this type of strapping is quite simple, it requires compliance with a number of requirements. Firstly, in order for water to circulate freely in the system, it is necessary to install heating equipment half a meter lower than the batteries are located in the house.Secondly, in order to minimize the manifestation of water resistance, pipes with a cross section of up to 5 cm are needed, while distribution pipes on batteries can have a value of 2.5 cm. Thirdly, locking devices and fittings directly affect the free circulation of water in the system, Therefore, there should be a minimum of such elements.

But for the sake of fairness, it is worth saying that an open system with natural circulation has a number of its advantages. Besides the fact that it is the easiest to arrange, the financial costs of it are not so great. True, the owner will not be able to constantly control the temperature regime of the coolant at the outlet, which is why the heating of the circuit is somewhat reduced. Also, the expansion tank occasionally remains open, which means that oxygen has contact with the coolant, which gradually increases the risk of corrosion.

Summing up, it is worth saying that experts recommend this type of heating scheme only for those private houses where people live from time to time, and not on an ongoing basis, for example, for summer cottages.

No. 8. Combustion chamber volume

The larger the volume of the combustion chamber, the more fuel can be loaded, and the less likely it is to run to the firebox and throw in a new portion. In the characteristics for the boiler, it is customary to indicate such an indicator as the ratio of the fuel load to the boiler power, measured in l / kW. Since a steel boiler with the same power as a cast iron one will have somewhat more compact parameters, for it this ratio is 1.6-2.6 l / kW. For cast iron boilers - 1.1-1.4 l / kW. The higher this indicator, the less often you have to run to the boiler.

Boilers with top fuel loading have a larger usable volume, and in this case the fuel is distributed more evenly. With front loading, especially if it is a cast iron multi-section heat exchanger, some effort will be required to evenly distribute the fuel.

Types of solid fuel boilers

Classic solid fuel boilers

Modern classic units are an effective alternative to appliances that run on other types of fuel, such as gas, which, unlike firewood, coal, coke and briquettes, cannot always be used due to the lack of a nearby main.

For the most part, they do not depend on electricity - they are loaded manually, operate in a natural circulation mode and are mechanically controlled. Some models provide automatic loading using feed hoppers - mainly for pellets, which are compressed wood pellets.

The units use several methods of temperature control:

1. With the help of a damper that opens slightly to let the right amount of air through;

2. With the help of cold water added at the feed;

3. With the help of hot liquid dispensed on the return.

Advantages:

• non-volatility of many models;
• good efficiency - the average efficiency is about 80%;
• universality - in most cases;
• relatively high level of security;
• cheap fuel - depending on the region;
• ease of operation.

Flaws:

• installation is possible only in a specially designated room;
• the need for a site for firewood, coal, briquettes;
• the need for regular maintenance, namely loading and cleaning;
• low comfort of use.

Such boilers are installed mainly in the countryside: in private houses, cottages, hotels, shops, warehouses.

Pyrolysis solid fuel boilers

The pyrolysis boiler, also called a gas generator, is an improved classic model.

It has 2 chambers interconnected by ceramic nozzles:

1. One is intended for firewood, which at a temperature of +200 ° C heat up, smolder and decompose into coal and a volatile substance with CO in the composition;

2. The other is used to receive the pyrolysis gas generated by the heat treatment of wood.

The latter burns at a temperature of ≈ +1150 ° C - pre-ignition occurs after air is supplied. As a result, 2 different fuels are extracted and used from ordinary firewood - gas and charcoal, the total heat transfer of which is much higher than that of the primary fuel.

During the operation of the pyrolysis unit, the moisture content of firewood is necessarily taken into account - it should be no more than 20%.

Advantages:

• high efficiency - is ≈ 90%;
• increased interval between downloads;
• almost complete burnout and low ash content;
• efficiency of operation;
• compatibility with an indirect heating boiler;
• the possibility of automatic control, which simplifies operation.

Flaws:

• the need for a special room, a platform for firewood and regular maintenance;
• dependence on power supply and humidity of logs;
• lack of combustion stability with incomplete filling;
• high price.

Pyrolysis boilers are characterized by high power, in addition, they are expensive, therefore they are usually installed in suburban residential and commercial buildings with a considerable square footage.

Solid fuel boilers of long burning

Among the competitors, the most expressive and efficient long-burning boiler called Stropuva is an innovative cylindrical unit with patented technology.

Firewood, briquettes or coal placed in the firebox are burned according to the principle of a candle, not a fire - from top to bottom, and not from bottom to top. An essential role for the effectiveness of this method is played by an automatic valve - a draft regulator, which expands or contracts depending on the heating value.

In these units, there are practically no temperature jumps, as a result, excess heat is not discharged into the storage tanks due to its absence.

One bookmark of firewood weighing 50 kg is enough for uninterrupted heating of a room of 130 m2 for 30 hours. In addition, the fuel actually burns down to the residue - after burning coal, cleaning is carried out weekly, in the case of logs - once every 14 days.

Advantages:

• non-volatility of many models;
• optimal efficiency - about 85%;
• long burning interval;
• no effect of loading on efficiency;
• economy of use;
• convenience in operation.

Flaws:

• the need for maintenance, premises and areas for storing fuel;
• uncomfortable doors, regardless of model;
• high price.

Objects for the use of such devices are private households, as well as small-sized commercial and outbuildings. For large buildings and structures, the units are mounted in a cascade.

Life hacks from heating engineers

Installing an autonomous power generator and connecting it as an emergency power source contributes not only to uninterrupted heat supply, but also to the safety of equipment.

If the electric generator and the boiler operate on the same type of fuel, for example, diesel fuel, and the boiler automation is reduced to a minimum, refueling the boiler and generator solves the problem of starting the equipment in the absence of electricity.

The presence of electricity generators or charged batteries is a prerequisite for autonomous existence. Electricity ensures the start of all systems, heating, water pumps, other equipment, including heating of sewer pipes. Therefore, the "crazy" ideas of sustainable houses with windmills and solar panels on the roofs are not so crazy on closer inspection.

Types of gas boilers

With open combustion chamber

Boilers with an open combustion chamber use air to maintain the fire, which comes directly from the room with the equipment located there. Removal is carried out using natural draft through the chimney.

Since a device of this type burns a lot of oxygen, it is installed in a non-residential specially adapted room with a 3-fold air exchange.

These devices are absolutely not suitable for apartments in multi-storey buildings, since ventilation wells cannot be used as chimneys.

Advantages:

• simplicity of design and, as a result, low cost of repair;
• no noise during operation;
• a wide range of;
• relatively low cost.

Flaws:

• the need for a separate room and chimney;
• unsuitable for apartments.

With closed combustion chamber

For units with a closed firebox, there is no need for a specially equipped room, since their chamber is sealed and does not come into direct contact with the internal air space.

Instead of a classic chimney, a horizontal coaxial chimney is used, which is a pipe in a pipe - one end of this product is attached to the appliance from above, the other goes out through the wall. Such a chimney works simply: air is supplied through the outer cavity of the two-pipe product, and exhaust gas is removed through the inner hole using an electric fan.

This device can be installed both in apartments and houses, and in any room convenient for operation.

Advantages:

• no need for a special room;
• operational safety;
• relatively high environmental friendliness;
• simple installation;
• ease of use.

Flaws:

• dependence on electricity;
• high noise level;
• High price.

single circuit

A single-circuit boiler is a classic heating device with a local purpose: preparation of a coolant for a heating system.

Its main feature is that in the design, among the many elements, only 2 tubes are provided: one for the entry of cold liquid, the other for the exit of the already heated one. The composition also includes 1 heat exchanger, which is natural, a burner and a pump that pumps the coolant - in the case of natural circulation, the latter may be absent.

When installing hot water, an indirect heating boiler is connected to the CO system - given the possibility of such a prospect, manufacturers produce boilers that are compatible with this drive.

Advantages:

• relatively low fuel consumption;
• simplicity in design, maintenance and repair;
• the possibility of creating hot water using an indirect heating boiler;
• acceptable price.

Flaws:

• used only for heating;
• for a set with a separate boiler, a special room is desirable.

Dual circuit

Double-circuit units are more complicated - one ring is intended for heating, the other for hot water supply. The design can have 2 separate heat exchangers (1 for each system) or 1 joint bithermic. The latter consists of a metal case, an outer tube for CO and an inner tube for hot water.

In the standard mode, water, heating up, is supplied to the radiators - when the mixer is turned on, for example, washing, the flow sensor is triggered, as a result of which the circulation pump turns off, the heating system stops working, and the hot water circuit starts to function. After closing the tap, the previous mode resumes.

Advantages:

• providing hot water to several systems at once;
• small dimensions;
• simple installation;
• affordable cost;
• the possibility of local shutdown of heating for the season "spring-autumn";
• a large selection, including design;
• ease of use.

Flaws:

• DHW flow diagram;
• accumulation of salt deposits in hard water.

Types of boilers and the principle of their operation

All solid fuel boilers are divided into several types, which differ from each other in many indicators. But according to the main characteristics, they are divided into four types:

• Classic;
• Pyrolysis heating boilers;
• Long burning boilers;
• Automatic;

Classical boilers - the principle of operation of a classic solid fuel boiler lies in the fact that heat is given by fiery combustion of fuel.It has two doors, through one of which fuel is loaded, through the other - the boiler is cleaned of ash and other combustion products. They can run on two types of fuel - wood and coal.

They differ in the material of manufacture of the heat exchanger; they can be made of cast iron or steel. Cast iron is a priority in terms of durability, its service life is more than 20 years. Among the shortcomings, one can note the fact that he is afraid of mechanical shocks and is very sensitive to temperature changes, which can lead to destruction. The steel heat exchanger is more resistant to temperature extremes and damage, but its service life is much lower - just over 6 years.

Pyrolysis (gas generating) boilers - this type of boiler works on the principle of pyrolysis, that is, decomposition and gasification of solid fuel. This process takes place with a closed chimney and a closed combustion chamber. After the release of the wood gas formed during the pyrolysis process, it is sent to the burner nozzle, where it mixes with secondary air, which is pumped by a fan. After that, the gas mixture enters the combustion chamber, where it ignites. Combustion occurs at a temperature that sometimes reaches 1200°, and the process will continue until the solid fuel is completely burned.

Long-burning boilers - in this type of boiler, a long burning process is ensured by special techniques. Currently, there are two long-burning systems (the Canadian system Buleryan, and the Baltic Stropuva), but the second one has not found wide application due to the high cost, complexity of operation and many other technical parameters.

Long-burning boilers can be attributed to pyrolysis boilers, but the principle of operation will be slightly different. The first system (Burelyan) is a furnace consisting of two chambers, where smoldering and gas formation occurs in the lower chamber. After the gas enters the second chamber, it mixes with air and then completely burns it (fuel afterburning). The design of such a solid fuel boiler is a cylinder, with pipes welded into it for half a circle. The arrangement of pipes from the bottom up provides good air circulation, thereby increasing heat transfer. They are installed mainly in non-residential premises, perfect for heating a garage or cottage. The price for such a boiler is adequate, it is possible to choose a size that suits a particular area.

The boiler according to the Stropuva system has two cylinders, one of which is located inside the second, according to the principle of a nesting doll. All the space between them is filled with water, which gradually heats up. The internal cylinder of the system plays the role of a firebox, where air is supplied with the help of a distributor. After loading the fuel, it begins to burn from top to bottom, thereby heating the coolant. The price declared by the manufacturer, a long burning time, from 2 to 4 days, depending on the fuel, the required cooling of the boiler and further cleaning before a new ignition, double the task and bring inconvenience. Therefore, this type of boiler did not bring wide distribution.

Automatic boilers - in this type of boiler, the process of loading fuel and removing ash is fully automated. The boiler is equipped with a screw or conveyor hopper for fuel supply and automatic ash removal.The option of a coal-fired automatic boiler implies the movement of the fuel combustion layer, which is necessary for complete combustion. For this, the automatic boiler is equipped with movable grates, or chopping and moving mechanisms. The parameters of heating of the coolant and combustion of fuel are provided by forced pressurization.

The advantages and features of automatic boilers can include;

• Do not require time-consuming maintenance and close attention to the combustion process;
• Are supplied with the included temperature regulator;
• Many are equipped with a sensor that monitors the temperature in the boiler itself;
• The efficiency of an automatic boiler is up to 85% of the total;
• Long-term operation, limited only by the capacity of the bunker for automatic fuel supply.

It is worth considering that fuel consumption, in particular coal, is much less than in traditional solid fuel boilers.

How to choose the power of a gas boiler

Most consultants who sell heating equipment independently calculate the required performance using the formula 1 kW = 10 m². Additional calculations are carried out according to the amount of coolant in the heating system.

Calculation of a single-circuit heating boiler

• For 60 m² - a unit of 6 kW + 20% = 7.5 kilowatts can satisfy the need for heat
  . If there is no model with a suitable performance size, preference is given to heating equipment with a large power value.
• In a similar way, calculations are made for 100 m² - the required power of boiler equipment, 12 kW.
• For heating 150 m², you need a gas boiler with a power of 15 kW + 20% (3 kilowatts) = 18 kW
  . Accordingly, for 200 m², a 22 kW boiler is required.

How to calculate the power of a double-circuit boiler

10 m² = 1 kW + 20% (power reserve) + 20% (for water heating)

The power of a double-circuit gas boiler for heating and hot water heating for 250 m² will be 25 kW + 40% (10 kilowatts) = 35 kW
. Calculations are suitable for two-circuit equipment. To calculate the performance of a single-circuit unit connected to an indirect heating boiler, a different formula is used.

Calculation of the power of an indirect heating boiler and a single-circuit boiler

• Determine what volume of the boiler will be sufficient to meet the needs of the residents of the house.
• In the technical documentation for the storage tank, the required performance of the boiler equipment is indicated in order to maintain the heating of hot water, without taking into account the necessary heat for heating. A 200 liter boiler will require an average of about 30 kW.
• The performance of the boiler equipment required for heating the house is calculated.

The resulting numbers are added up. The amount equal to 20% is subtracted from the result. This must be done for the reason that the heating will not simultaneously work for heating and DHW. The calculation of the thermal power of a single-circuit heating boiler, taking into account an external water heater for hot water supply, is done taking into account this feature.

What power reserve should a gas boiler have

• For single-circuit models, the margin is about 20%.
• For two-circuit units, 20% + 20%.
• Boilers with connection to an indirect heating boiler - in the storage tank configuration, the required additional performance margin is indicated.

Calculation of gas demand based on boiler power

In practice, this means that 1 m³ of gas is equal to 10 kW of thermal energy, assuming 100% heat transfer.Accordingly, with an efficiency of 92%, fuel costs will be 1.12 m³, and at 108% no more than 0.92 m³.

The method for calculating the volume of consumed gas takes into account the performance of the unit. So, a 10 kW heating device, within an hour, will burn 1.12 m³ of fuel, a 40 kW unit, 4.48 m³. This dependence of gas consumption on the power of boiler equipment is taken into account in complex heat engineering calculations.

The ratio is also built into the online heating costs. Manufacturers often indicate the average gas consumption for each model produced.

In order to fully calculate the approximate material costs of heating, it will be necessary to calculate the electricity consumption in volatile heating boilers. At the moment, boiler equipment operating on main gas is the most economical way of heating.

For heated buildings of a large area, calculations are carried out only after an audit of the heat loss of the building. In other cases, when calculating, they use special formulas or online services.

Gas boiler - universal heat exchanger, providing circulation of hot water for household purposes and space heating.

The device looks like like a small refrigerator.

When installing a heating boiler, it is necessary to correctly calculate its power.