A modern residential building is a whole complex complex, the task of which is to provide the domestic needs of its residents and residents. The comfort of the inhabitants and the level of livability depend on the level of technical equipment of a residential building. One of the leading roles in this regard is played by the heating system, which should not only provide heating of the interior during the cold season, but also guarantee the operation of the hot water supply system. For a country house, in the absence of a central gas supply, issues with heating and hot water supply can be solved by a double-circuit solid fuel boiler.

Let’s take a closer look at what this technique is.

The feasibility of installing a solid fuel boiler in a residential building

This type of heating equipment is very convenient for those residential buildings where there is no centralized gas supply system. The option with electric heating is recognized today as not effective due to the high cost of electricity, therefore it is often used only as an aid. Solid fuel units, on the contrary, are able to operate on fuel, which is sometimes at our fingertips. It can be firewood, woodworking waste, coal. Solid fuel, available in sufficient quantities, will not only provide a working boiler with a constant load, but will also bring significant savings to the home budget.

Single-circuit and double-circuit solid fuel boilers presented for sale today are devices with high technological characteristics. This technique has now been brought to perfection by manufacturing companies. A number of design innovations have made it possible to significantly increase the efficiency of boilers, and the conditions for servicing solid fuel heating devices have changed for the better. The double-circuit solid fuel boiler is quite capable of heating a residential building during the heating season, at the same time providing residents with hot water for domestic needs.

Thanks to technological progress, modern technologies do not stand still. Demand creates supply. Just yesterday, unpopular wood-fired or coal-fired heating boilers are becoming popular again. The intensity of suburban housing construction has become one of the reasons that solid fuel heaters are back in price. The people massively install heating units for the home heating system, using organic and fossil raw materials as fuel.


A double-circuit solid fuel boiler of long burning is the best solution for heating a private house. A powerful unit that provides all living spaces with a sufficient amount of thermal energy, is at the same time a very economical and easy-to-maintain heater. Moreover, such heating devices require minimal human intervention.

The combustion of the fuel placed in the boiler takes a long time, freeing the residents of the house from the need to constantly throw up fuel material. It is the long burning process that makes this technique as attractive as possible to the consumer. Not everyone wants to be a stoker and stand near the firebox on cold winter nights, throwing firewood or coal in the boiler. The very principle of operation, which is the basis of the operation of the devices, gave them the name — long-burning boilers, solid fuel.

The principle of operation of heating equipment of this type

In various materials, much has already been said about what the principle of operation of heating solid fuel technology for long-term combustion is based on. The achieved effect is due to a fundamentally different way of fuel combustion in the combustion chamber. Due to the multi-stage combustion process, complete burnout of the fuel mass loaded into the boiler is ensured. At the same time, wood gas is released in large quantities, which performs the main work of heating the coolant.

For reference: units operate on the basis of pyrolysis, the process of generating volatile combustible compounds obtained from wood as a result of exothermic reactions. In the process of fuel smoldering, wood (pyrolysis) gas is formed, which, when interacting with hot air, ignites. This technique is also called gas generators.

The principle of operation of boiler equipment is relatively clear, let’s figure out how a double-circuit autonomous solid fuel boiler works at home. Let’s consider its main functions. The presence of two circuits in the system provides heating in the house and hot water supply. In the primary circuit, boiler water circulates, which diverges throughout the pipeline, supplying heat to the heating radiators. The second circuit is designed to remove the waste coolant back to the boiler for subsequent heating. Sensors installed on both circuits — determinants, sensitively react to the slightest change in the set temperature of the coolant, giving signals to the control panel. Accordingly, the automation actuates a mechanical device that regulates the air flow in the combustion chamber of the heating device.

Design features of the two-circuit model

Having a double load, heating and hot water supply, solid fuel units of this type are equipped with additional devices. There are two types of such devices:

  • storage boiler (heat accumulator);
  • additional coil.

The difference in both devices lies in the principle of heating water. In the first case, we are talking about a storage tank that accumulates hot water and from there the hot water diverges to the connection points. In the second case, a cast-iron hot water coil is installed inside the boiler. Heating of water occurs in the mode of constant circulation of hot water. Both options are equally successful and efficient, providing a stable supply of hot water to the residents of the house. Together with the boiler, the heater will not take up much space, however, the presence of two circuits requires certain rules to be observed during the operation of these devices.

The connection diagram for a double-circuit solid fuel boiler looks something like this. By their design, all heating devices of this type are almost the same, with the exception of some differences.

The only condition: when connected to a heat storage system, it is necessary to have strict control over the use of hot water. Installing more than two hot water connection points in the house can adversely affect the performance of the DHW system. The flow-through method of heating hot water is more dynamic in terms of operation, however, at the same time, the boiler power should be much higher.


Long-burning double-circuit boilers have a standard design, which is almost the same for many models, with the exception of some differences.

The figure shows a typical design of a solid fuel unit operating for a heating system and hot water supply.

Solid fuel boilers with two circuits consist of:

  • main, heat-insulated body;
  • combustion chamber (furnace);
  • podzol chamber (ashpit);
  • the main heat exchanger of the heating system;
  • additional heat exchanger (coil) for hot water supply;
  • automation and control devices;
  • damper and chimney.

In some cases, an additional circulation pump is installed, which provides forced circulation of the coolant in the main heating circuit. For better operation of a long-burning heater, fans are used that force air into the combustion chamber and contribute to a better outflow of combustion products through the chimney.

Some nuances in the operation of double-circuit solid fuel boilers


An obvious plus that solid fuel boilers of this type have is long-term operation with a single fuel load.

For example: 30-50 kg. firewood laid in the firebox can burn up to 12 hours. During this time, the unit is able to provide the maximum possible heat to heat the living quarters in the house and provide normal domestic hot water needs. Reducing the consumption of hot water will increase the duration of fuel burning up to 24 hours. The boiler will operate in nominal mode, maintaining a certain temperature in the house.

It should be remembered! A solid fuel unit extinguished for a long period during the winter can cause the entire heating system to freeze. To avoid such troubles, antifreeze can be used for the main heating circuit.

It is also important that long-burning double-circuit boilers do not allow high accuracy to regulate the temperature of the coolant in the heating system. The reason for the difficulty lies in the inertia of the operating heating equipment. The built-in boiler will solve this problem by creating optimal conditions for controlling the heating unit.

In conclusion, a few words should be said about where and how it is better to install this heating equipment in the house. Long-burning solid fuel boilers are produced only in a floor version. Due to the bulkiness of the design itself and the need to install a storage tank, the best option would be to equip a special boiler room.


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