Despite the fact that most private households are connected to the gas pipeline, the most ancient method of heating a house by burning wood is still in great demand. The heat generators that run on this ecological fuel are constantly being improved and become more convenient and efficient every day. Engineers managed to increase the burning time of a single fuel bookmark many times over. Thanks to this development, wood boilers for heating private houses appeared.
Features and Benefits
These units, although resembling old archaic solutions, have several serious advantages. So, the design is extremely simple, and there’s practically nothing to break into it. In some regions, firewood is not only available, but also produced almost for free.
A wood-burning boiler for heating, being untied from centralized energy supply systems, is completely and completely independent. Therefore, users who have enough fuel for it are insured against a variety of troubles.
disadvantages
There are other features that are undesirable. The installation has a large thermal inertia. This means that if air access is completely limited, power does not drop instantly. This carries risks - the coolant may boil. A safety valve must be installed in the piping of the wood boiler for the house.
Gases in smoke contain harmful substances - these are oxides of various chemical elements. Their danger is that when combined with water, they form acids - sulfuric and others. The condensate that forms when the combustion products cool down will be quite caustic. Therefore, experts recommend establishing certain restrictions on the temperature of water or antifreeze in the heating system coming from the return circuit to the heat exchanger. The temperature should not fall below 55 degrees. To prevent such cases, a special unit is mounted in the system that automatically redirects part of the heated heat carrier to the cooled return circuit.
Another feature of wood-fired boilers is the need for periodic cleaning of the internals of the device from combustion products. The chimney also requires cleaning. How often do this? Experts say that it is necessary to clean the chimney and the heating wood boiler itself from the soot accumulated inside at least once a year.
And finally, one of the most serious drawbacks is that the fuel is completely enclosed by hand. You need to do this often. To maintain a comfortable temperature, it is necessary to add new firewood every 3 hours. The body of these boilers does not have a high body capacity - this is not a Russian stove, which is heated once a day. Engineers had to work hard to ensure that the unit worked longer on one tab. Such a system is called a long-burning wood-burning boiler.
Operating principle
There are several schemes of operation of these heating systems. Let's consider each separately. The differences are in how the fuel is stacked and how it is ignited.
Column fuel stacking and ignition from above
Firewood will burn the longest if set on fire. So, the fuel will burn in the direction from top to bottom. Wood-fired boilers operating on this principle are called top-burning boilers. So that the flame does not have the ability to quickly spread through the fuel, air is supplied only to the combustion zone. To do this, the design has special telescopic ducts.
Approximately in this way systems with a long firebox work. But firewood here is set on fire not from above, but from the side of the boiler. Such solutions are much less common, as they have large overall dimensions.
Wood pyrolysis
This is another principle on which wood boilers for a long-burning house work. The peculiarity of this principle is that it is not the wood itself that is used as fuel, but the gas obtained as a result of pyrolysis.
When heated to high temperatures and in conditions of limited air access, long chains of organic wood particles become short. As a result, combustible gases are formed. In our case, this is the so-called wood gas. Then, through the nozzle, it is fed into the second chamber of the boiler, where it burns out. Air is introduced into the chamber and the gas ignites. Such wood boilers are called pyrolysis.
Unit with automatic ignition system
This is another version of the popular wood-fired boilers. They take an ordinary wood-based heat generator and equip it with a nozzle with a damper and an automatically controlled fan. In the process of burning wood, the fan pumps air into the combustion chamber. When they are warm enough, the automation stops the flow of oxygen.
The open shutter closes under its own weight. As a result, the flame goes out. When the water in the system or antifreeze cools down to certain temperatures, the automatic system will restart the fan, it will again begin to supply air - the fuel will ignite.
Airflow restriction for smoldering firewood
This mode of operation of a wood boiler for heating a house has a lot of disadvantages. In this case, combustion is not fully carried out - the efficiency of the system is very low. In the process, a huge amount of soot is formed, and black smoke comes from the chimney. Since the fuel does not burn in full, condensate forms - it is caustic and poisonous. Moreover, it is quite a lot.
But despite the shortcomings, wood-fired boilers operating on the basis of this principle (and these are the famous Bulerian stoves) are widely used in the field. They are autonomous and do not require electricity.
Functional Features and Specifications
Modern wood-fired boilers can not only provide heating, but can also heat water. There are two types of heat generators. There are two-and single-circuit solutions.
The double-circuit wood boiler for heating a private house has an additional one heat exchanger. It is designed specifically for heating water. When the second circuit becomes active, the automation will not supply the hot coolant to the heating pipes, but to heat the second circuit. Such a unit is a flow heater. But at the same time, heat does not enter the heating system.
A single-circuit boiler is a system with the function of connecting indirect heating boilers. This boiler is a storage tank with a coil inside. The latter circulates the coolant before entering the heating system. This option is more convenient for domestic use.
Popular models
Many people think that European brands are leading among manufacturers of wood-fired boilers for heating a private house. This is actually not the case. More popular are Russian models. They are much cheaper and no less high quality in comparison with European counterparts.
You can highlight the products of the domestic manufacturer "Prometheus". The power of this equipment is from 10 to 50 kW. You can choose a model for heating a small cottage or a large house. The body material is made of steel. The boiler can work not only on wood, but also on coal.
Also popular is the Russian KMCh product. This is a multi-fuel equipment. It works great on gas, diesel, wood and coal. It is acquired by people who are not yet sure what kind of heating to carry out.
There are many European brands. So, Czech cars Buderus Logano occupy worthy first places in the market of heating equipment. The boiler is considered universal. It can work not only on wood, but also on gas. This is a good option for those who have problems with gas supply. If it was suddenly turned off, the house and its inhabitants will not freeze.
Lithuanian Stropuva products are used in houses with high ceilings. But do not think that the boiler is something formless. This is an elegant design that will fit into any interior. Wood burning time is 80 hours. This is true, although it seems unbelievable. It must be borne in mind that the boiler is quite large.
How to choose a unit?
To correctly choose a wood boiler for a private house, you should know the power. It is equal to the heat loss that is characteristic of heated rooms in the coldest periods of the year. This leak can be identified using thermal engineering calculations. They take into account the material from which the house is built, the temperature difference inside and outside, the area of the window openings, the orientation of the building in relation to the cardinal points.
These calculations can be ordered from qualified engineers. But you can calculate everything yourself - how this is done is indicated in the corresponding SNiPs.
Very often the recommended power is one kW for every 10 square meters. This is an approximate figure, and it is relevant only for regions in the middle zone of the Russian Federation.
Efficiency will be maximum only when the boiler is in operation. Therefore, to save money, it is recommended to buy two units - one for medium temperature, and the second - low-power. The latter will help the large boiler in the cold winter, and will also work between seasons. In addition, each unit will operate in nominal conditions.
The most important part of any boiler is the heat exchanger. The most reliable are cast iron products. They are not subject to corrosion, and the service life is 20-25 years. Steel heat exchangers have a lower price, but less strength - this is due to welds. Service life will be no more than 15 years.
Expediency of installation
The use of wood-fired boilers in the heating system will be advisable when it is completely impossible to connect gas or use any other coolant. Firewood is a non-renewable source of energy. But if you have access to free raw materials in large quantities, anyway, the preparation of firewood requires an investment of time, effort and money. This is not always as cost-effective as it may seem.
However, if the boiler is installed in the country, then this is quite an effective option. People are not often at dachas and come for a short time, which means that a lot of fuel is not needed. If you need to heat a large room, then it is best to purchase multi-fuel solutions or a long-burning boiler. Such units will cost a little more. But they are very versatile. In the absence of one type of fuel, you can always use another. If a conventional wood-fired boiler is used, this feature will not be available.