There are many ways to heat a private house associated with the use of gas and electricity. However, a proven option with the use of solid-fuel furnaces. To use stove heating in its classical form with the release of heat into the air from the walls of the furnace is effective only for small rooms.
For uniform and rapid distribution of heat, heating circuits are used, where air or water is used as the coolant.
The content of the article:
- Heating with air system
- The device of water heating on the basis of the furnace
- The main elements of water heating
- Types of heat exchanger and methods of placement
- Circulation of water in the heating circuit
- Expansion Tank Use Rules
- The choice between pipes and radiators
- Prevent freezing of the heating system
- Useful video on the topic
Heating with air system
The reason for the sustainable preference, which the owners of private houses give the stove heating option, is the low cost and availability of firewood, fuel briquettes or coal.
The disadvantage is that the treated space is limited, which can be eliminated by arranging a water and air system based on a brick unit.
The specificity of the device for heating low-rise buildings with an oven is presented in the photo selection:
The principle of operation of air heating on the basis of a stove or fireplace is the transfer of a warm stream heated to the working temperature in a heat exchanger or in a boiler. Air enters either directly into the room, or through air ducts. Due to the relatively small path he does not have time to lose the temperature. The result is a uniform distribution of heat throughout the house.
The camera for heating the air is arranged above the furnace, so that the hot upper surface of the furnace and the chimney transfer the maximum amount of heat to it. Air circulation occurs naturally or with the help of fans.
Natural circulation occurs as a result of the difference in the density of cold and hot air. Cold air entering the heating chamber displaces hot air into the air ducts. This method does not require the presence of electricity, however, if the air does not move fast enough through the heating chamber, it becomes very hot, which can cause problems.
Forced circulation occurs with the use of fans or pumps. However, space heating occurs more quickly and evenly. With forced ventilation, by adjusting its mode, you can easily control the volume of air supplied to various rooms, thereby determining the microclimate of individual rooms in the house.
According to the type of cold air supply, the systems are divided into two types:
- With full recycling. Heated air masses alternate with chilled within the same room. The disadvantage of the circuit is that the air quality drops with each heating / cooling cycle.
- With partial reclamation. Part of the fresh air is taken from the outside, which is mixed into the air from the room. After heating, the mixture of two air portions is supplied to the consumer. Advantage in stable air quality, lack of energy dependence.
It is clear that the first group includes channel systems with the natural movement of the air coolant. The second group includes options with the forced movement of air, for the movement of which it is not necessary to arrange a duct network.
The main advantages of air heating in comparison with water:
- high efficiency;
- no radiators in the rooms.
The device contour with forced movement allows you to do without the construction of the duct system. In addition, this variety can be combined with air conditioning, humidification and air ionization.
If the installation of a device that stimulates the movement of heated air is not planned, then the following methods are used to improve the stove performance:
The increase in efficiency spontaneously increases the speed of the air flow: the faster the air heats up, the more intense the change in the cooled and heated air mass.
The main disadvantages of air heating compared to water:
- when using a furnace, the temperature of the supplied air has a considerable range, unlike using other means of heating;
- air ducts have a large diameter, so installation must be carried out at the construction stage;
- preferably the location of the furnace in the basement, otherwise it is necessary to use fans that emit noise.
The movement of air in the room has a negative side - raises dust, but the use of filters on ductwork allows this dust to be effectively caught, thus reducing the total amount of dust in the house.
Another feature of air heating having a positive and negative side is the rate of heat transfer. On the one hand, the rooms heat up faster than when heated by a water circuit, on the other thermal inertia is absent - as soon as the stove or fireplace goes out, the room immediately begins cool down.
Unlike water heating installation of the air heating system is not difficult. All elements (pipes, bends, ventilation grilles) can be simply connected without welding. There are flexible air ducts that can take any form, depending on the geometry of the premises.
Despite this, air heating systems based on stoves or fireplaces are not yet widespread. Much more often in an individual low-rise building, a water circuit is used to heat the premises.
The device of water heating on the basis of the furnace
The principles of operation of any water heating system are based on the distribution of heat from a local source throughout the entire room, using the movement of water along the heating circuit.
The main elements of water heating
For a heating circuit with a water circuit, the main elements are:
- a stove or fireplace with a heat exchanger in which water is heated;
- heating circuit, where the heat is transferred to the room;
- expansion tank to prevent damage to the system as a result of increased pressure;
- circulation pump to ensure the movement of water around the circuit.
There are general rules for the operation of water heating, such as wiring diagrams, which are well known and must be followed. However, when using a furnace as a heat source, there are specific requirements associated with the feature of the temperature regime.
The furnaces do not heat up quickly and cool slowly, an uneven heat generation occurs and only Correct installation of all system components will allow to avoid problems with high-quality heating. premises of the house.
Types of heat exchanger and methods of placement
For the manufacture of the heat exchanger for the furnaces, sheet steel “black” steel or heat-resistant stainless steel is used. The use of cast iron as a material for production is difficult, but you can use finished cast iron products, such as cast iron radiators.
It is possible to use copper, which has better thermal conductivity than steel, but the price of such a device will be high. The heat exchanger is recommended to be made of steel with a thickness of 3 mm. At high furnace temperatures, arising from the use of coal or, especially, coke, it is necessary to use steel 5 mm thick.
Heat exchangers can be divided into three types:
- registers, coils and radiators, consisting of a set of pipes;
- shirts (boilers), welded from sheet steel;
- combined version in the form of vertical walls connected by pipes (so-called “books”).
Shirts made of sheet steel are easier to make and easier to clean from the products of combustion of fuel, but tubular structures have a large heating area. In the manufacture of shirts must take into account the excess water pressure that occurs when using a membrane tank expander or lifting water to a great height.
The heat exchanger for water heating on the basis of the furnace can be made of scrap materials:
In this case, it is required to use steel with a thickness of at least 5 mm and additionally reinforce the walls with stiffening ribs in order to avoid their deformation.
The shapes of tubular structures can be different, however, it is necessary to observe the condition that the internal size of the pipes is at least 3 cm in diameter. Otherwise, if the circulation speed is slow or the temperature is too high, boiling water is likely. Registers are made, as a rule, from shaped, and not from round pipes, in order to facilitate welding work.
You can make a heat exchanger of the required size by yourself. In this case, special attention should be paid to the quality of welding. If a heat exchanger leaks, all the water will flow into the oven. In addition, to solve the problem, you will have to do a lot of work: disassemble the furnace, remove it, brew it and put the heat exchanger back, and then reassemble the furnace.
There are two options for the location of the heat exchanger. In the first case, it is placed directly in the firebox, significantly narrowing its space. In the second case, the registers are installed in the cap of non-current furnaces, however, the furnace itself in this case has a more complex structure.
When installing a tubular type of heat exchanger, it is necessary to leave a gap between it and the wall of the stove. This is necessary for better heating of the coolant, as well as the possibility of cleaning the register. It is periodically necessary to clean both the shirts and the registers, since in case of heavy clogging with ash, the heat exchange efficiency decreases.
In the presence of the hob cleaning occurs after its removal. If the furnace has only a heating function, then cleaning takes place through the combustion door.
Circulation of water in the heating circuit
The basic principles of the organization of the natural circulation of water in the system are to simulate a “collector acceleration "at the exit from the heat exchanger and in creating a constant slope of the pipes of the heating circuit of a value of 3-5 degrees The general meaning of the “runaway collector” is that the heated water from the furnace rises vertically upwards and then is distributed along the heating circuit.
Circulation occurs due to the difference in the specific gravity of cold and hot water. Cold water is heavier than hot water, and flowing to the heat exchanger, displaces hot water up the pipe. The entry point of the "return" must be lower than the output of water from the radiators of heating, otherwise the circulation of water will be very slow or it will not be at all.
The installation of circulation pumps increases the speed of water movement along the heating circuit and, thus, a faster and even distribution of heat throughout the house. At the same time it is possible to use several pumps for different heating circuits.
In the event of power surges, it is necessary to apply a voltage regulator, since the failure of the pump can have serious consequences for the entire system. Pumps can be divided into two types relative to the position of the engine: with a "dry" rotor and "wet" a rotor, and on two types on tension: they can work from a network of 220 Volts and from power supplies in 12 Volt.
The engine in pumps with a "dry" rotor is isolated from the immersed impeller with o-rings. Compared to pumps with a submerged engine, "dry" pumps have a higher efficiency.
However, among the shortcomings can be called a high noise level, the need for regular maintenance and reduced lifespan. Therefore, in a private house, as a rule, use a circulation pump with a "wet" rotor.
The choice of the type of pump power depends on the possibility of natural circulation of water in the system. If it is impossible without the participation of the pump, then the choice should be made in favor of the option with the support of 12 Volts and an uninterruptible power supply.
Otherwise, in the event of a power outage, water may boil and the system will fail. If natural circulation is possible, then it is better to purchase a more common and cheaper option with 220 volt mains power.
When installing a pump with a power of 220 volts, it is necessary to organize the possibility of functioning of the heating system during a power outage. To do this, install a stop valve on the pipe, and bypassing it, install a bypass pipe with a pump (the so-called "bypass").
On the bypass pipe in front of the pump install a crane filter, and then - a stop valve. By adjusting the position of the shut-off valves on the main and by-pass pipes, it is possible to turn on the mode of forced and natural circulation.
As a rule, the pump is installed on the "return pipe" near the furnace so that the temperature of the liquid that will pass through the pump is the lowest. This will significantly prolong the life of the pump. In addition, it is necessary to place the maximum possible number of controls of the heating system in one place so that in the event of an emergency eliminate.
Expansion Tank Use Rules
The fluid expands when heated, and if this happens in a closed system, the pressure inside it will increase greatly, and the pressure increase is fraught with water breakthrough. The use of a safety valve is impractical, since after cooling the water and reducing its volume, air will be launched into the system.
Therefore, in the heating circuits with the forced movement of water use special expansion tanks, which are open or closed types. Their volume is calculated on the basis of not only the maximum thermal expansion of the liquid (5-7%), but also taking into account the possibility of boiling the system.
An open type tank equips a water circuit of a gravitational-type heating furnace, i.e. with natural transportation of the heat carrier. It is a metal container of arbitrary shape, located at the very top of the heating circuit. It directly communicates with the atmosphere, because of which the coolant is partially evaporated.
The pipeline is connected to the bottom or bottom quarter of the tank, and a branch pipe is welded to the top of it to drain water in case of overflow and air outlet from the system. Practice shows that the volume of an open type tank should be at least 15% of the volume of water in the heating system.
The tank of the closed or membrane type represents the closed vessel with a membrane inside. Water, heating, increases pressure, stretches the membrane and enters the tank. In the event of excess pressure, the automation is triggered, and the excess coolant is discharged into the sewer.
After the first discharge, there is usually no reason to re-produce it, since the volume of coolant becomes equal to the volume of the system.
A closed membrane tank is installed in front of the pump. Such a tank, unlike an open type tank, cannot get rid of the air itself, therefore at the top of the contour heating, you must install a Mayevsky crane (mechanical air vent) or its automatic analogue The only element of the membrane tank that can eventually fail is the membrane, so it’s better to buy a tank with the possibility of changing the membrane.
When purchasing a closed type tank, which is sometimes called a hydraulic accumulator, the main thing is not to confuse it with a hydraulic accumulator for water supply. For a membrane tank that is used in heating, the working temperature is up to 120 degrees, and the pressure is up to 3 bar. For water use tanks with temperatures up to 70 degrees and pressures up to 10 bar.
The choice between pipes and radiators
A plastic pipe system with radiators (batteries) or a metal pipe system can be used as a water circuit for stove heating. The main advantage of radiators is that they look prettier compared to massive air ducts.
Plastic wiring can be easily hidden in the floor, as it does not give off heat. Although by the rules the wiring of water heating should be open. However, polymer pipelines have limitations: they can not be laid where there is a possibility of melting and direct action of UV.
The advantage of metal pipes lies in the lower price of the entire heating circuit, ease of installation and less frequently arising problems during the operation of the system.
A slight advantage of a radiator system is also the ease of temperature adjustment. Even the most accurate calculations of the temperature of the room can be adjusted. For example, a young child up to 6 months is recommended a temperature of 19-21 degrees Celsius, while a comfortable temperature in the rest of the house is considered 25 degrees.
To ensure such a temperature for a long period of time in the room, it is sufficient to fully or partially close the heat supply tap to one of the radiators. In the case of a metal pipe, the issue can also be solved, but in a more complicated way: to reduce the heat transfer of the pipe segment using polyurethane foam or foil shells.
Another option of the heating circuit can be a water heated floor. This is a very comfortable feeling of heat supplying for a person, however, installing a heated floor is much more laborious than the options considered earlier.
In addition, when using a heated floor, it is not possible to provide a slope for the natural circulation of water, which in combination with a small diameter pipe of a warm floor leads to the mandatory condition for the use of circulating the pump.
Prevent freezing of the heating system
Using water as a coolant has one drawback - if the heating system freezes, the pipeline and appliances will be damaged. It is especially difficult to recover in this case the heat exchanger integrated into the furnace.
This problem is relevant for homes that in the winter can not be heated for a long time. One way to prevent damage to the system is to use antifreeze designed for heating systems instead of water.
For residential premises, propylene glycol-based fluids are used as antifreeze as a non-toxic substance, unlike ethylene glycol.
However, the idea of using antifreeze has its disadvantages:
- antifreeze based on propylene glycol is expensive (from 80 p / liter);
- the specific heat capacity of antifreeze is less than that of water (approximately 15%), therefore, a large furnace capacity and a large surface area of space heating devices are needed;
- antifreeze has a higher dynamic viscosity than water, therefore a more powerful circulation pump is needed, and natural circulation is impossible;
- when heated, the antifreeze expands up to 40%, therefore it is necessary to use a large expansion tank of a closed type;
- propylene glycol is very fluid, therefore it penetrates through the compounds in the heating system through which water does not penetrate;
- propylene glycol is incompatible with galvanized pipes, because upon contact the antifreeze additive loses its properties;
- when boiling antifreeze (which is likely when using furnaces) an irreversible chemical reaction occurs, as a result of which the entire system will have to be drained and refilled antifreeze.
For antifreeze, the heating system must be calculated in advance - it is quite problematic to use it in projects implemented for water.
Moreover, the project with the use of antifreeze will be much more expensive than a water heating system. Therefore, the use of antifreeze has not yet become widespread in private homes for stove heating, and other methods are used to prevent freezing.
Drainage of water from the circuit and shirt or furnace register is the most common solution to the problem with a long absence of the owners of the house. In addition to the additional work, the disadvantages of this method include the access of air to the metal elements of the system from the inside and, as a result, the spread of corrosion.
Also, as a solution to the problem for a short period of time, integration into the heating circuit of an electric boiler of small capacity is used. His work at a minimum level of energy consumption is able to temporarily maintain a positive water temperature.
Useful video on the topic
Working heating system based on the stove and the water circuit in a private house with an area of 80 square meters:
Heat is supplied to the heating system from stoves and fireplaces in portions, which complicates the task of calculating the parameters of the heating circuit elements. It is quite problematic to carry out work on the contour reworking, therefore, with a lack of experience in this area, it is better to turn to specialists who have the skills to solve such problems.