DIY boiler for a brick oven for a country house

Types of stoves with built-in boiler

The design can be made of metal or brick with different placement of the heater, with a boiler for heating water for washing, if we are talking about a bathhouse. The dimensions are not limited: the choice of parameters is determined taking into account the dimensions of the room, the building materials, as well as the local climate.

It is necessary to consider the design features of two types of furnaces with heating boilers:

The boiler is built into the chimney. This model has a long service life, the walls of the stove completely receive heat from the firebox, and the heat transfer rates are unchanged. Disadvantage: you cannot heat a large area.
The boiler is located directly in the firebox. You can heat a large area of the room. It is possible to use different types of heat exchanger. Disadvantages: metal parts come into direct contact with fire, resulting in destruction. Due to the low temperature of the heat exchanger, condensation is generated, which later causes a lot of soot to stick to the surface, resulting in a decrease in efficiency.

Review of various schemes of water heating furnaces

One of the simplest stove designs with a U-shaped heat exchanger installed directly in the firebox. The heater with flat surfaces is made of 4 mm thick sheet metal; it is better to use heat-resistant steel. Another option is a coil in the form of a register, welded from pipes (possibly water and gas pipes) with a nominal diameter of 50 mm and a wall thickness of at least 3.5 mm. The figure shows a diagram of a water-heated furnace of a similar design.

Drawing of a stove with a built-in heat exchanger for water heating

1 – heat exchanger in the combustion chamber; 2 – door for cleaning chimneys; 3 - supply to the heating system.

The principle of operation here is simple: a steel register with a coolant is heated directly from the flame in the firebox, and the combustion products rush upward and make 3 strokes, simultaneously giving off heat to the brick walls and oven for cooking.

A slightly different stove for a home with water heating is a dual-purpose hob with a heater built into the firebox. The stove does not have long chimney channels, since it provides for the extraction of heat from combustion products by a water heat exchanger. The dimensions of the heat source are 1030 x 650 x 780 (height), the heater power is about 9 kW. The latter is made of pipes with diameters of 57 x 3 mm and 48 x 3 mm. The design of the furnace is shown in the photo.

Oven with hob

1 – firebox; 2 – ash chamber; 3 – door for cleaning; 4 – oven; 5 – hob; 6 – clay solution; 7 – water heater; 8 – chimney channel; 9, 10 – respectively, return and supply pipelines of the heating system.

The fuel, when burned, heats the coil directly. Additionally, it is heated by flue gases, which then enter the channel between the hob and oven, go around the latter and are discharged through the chimney. The heated coolant circulates from the register into the system, and the impulse can be either natural or forced. Thus, the water heater removes heat from the firebox and combustion products, cooling them to 150-200 ºС, due to which water heating from the stove is realized.

Despite all the advantages of such a design, there is an irrational grain in its work. The fact is that the combustion products, from which the hob warms up, are strongly cooled by the heat exchanger. It turns out that during cooking it is necessary to reheat the stove in order to warm up the hob, and at this time the water heating of the house will function at full capacity, and this is irrational and uneconomical. To limit the temperature of the coolant, you will have to install a buffer tank - a heat accumulator, otherwise in the autumn-spring period the rooms will become unbearably hot.

The two-chamber wood-burning stove with water heating by K. A. Dmitriev is devoid of the significant drawback described above and is considered the most common option in central Russia. It has separate chimney channels and two separate fireboxes - one for heating the oven and cooking floor, and the second for water heating from the stove. Separate chimneys at a height of 2 m are combined into one. The overall dimensions of the stove are 1500 x 680 x 770 mm (height), the developed thermal power is 9.5 kW, which is already significant, since it is enough for a house with an area of 100-120 m2. The design can be studied in detail using the drawings.

Structural diagram and cross sections of the furnace

1 – ash chamber; 2, 5 – combustion chambers; 3 – oven; 4 – ash pan door; 6 – cooking floor; 7, 8 — connection to water heating; 9 – heat exchanger; 10 – valve.

When the first firebox is operating, flue gases wash around the metal oven and enter the flue located underneath it. The water heater is not involved in the process, so this mode is convenient in the summer and transition period. In the cold season, a second chamber is heated, which is used only to heat a private home and does not affect the operation of the hob and oven. This version of the brick stove is optimal and economical, showing good results in the efficiency of burning solid fuels (efficiency - 50-55%).

Masonry and brick

The principle of brick laying

Stove makers have enjoyed well-deserved respect since ancient times. Masters of their craft create stoves with a heating boiler, which always have good “draft” and an evenly heated surface.

There are several general rules that all specialists follow without exception:

Combustion chambers are made of fire-resistant materials. Open fire can easily damage ordinary brick and even stone.
You shouldn’t skimp on materials by laying quarter-brick walls. This reduces the reliability and stability of the entire structure.
It is necessary to carefully monitor the tightness of the seams. Any gap will subsequently allow carbon monoxide to pass through, which is dangerous for the lives of the inhabitants of the house.

Sometimes home owners resort to a little trick by setting up separate chambers for heating and cooking in the summer. This is a completely justified solution that allows you to save fuel in the warm season.

Principle of operation

Units with a water circuit are equipped with a heat exchanger built into the firebox or chimney duct. There are models that can operate in steam circulation mode.

A wood heating stove can be made of boiler steel or cast iron, designed to operate under high steam pressure. These devices are used both as additional equipment and as the main heat source.

A heat exchanger is installed inside the furnace unit. Heated gases move through the channels of the heating reservoir, transferring heat to the liquid. A furnace with a boiler in its design can have several tanks at the same time, which can significantly increase its efficiency. Water is heated in one tank, and with increased heating, the process of vaporization occurs in the second.

To heat a large building with traditional furnace heating, several furnaces will be required, and the consumption of coal or fuel will be quite high. Therefore, a more economical and alternative option would be a stove for water heating a house using wood, equipped with a special hot water boiler built into the firebox. Even in severe frosts, heating the stove twice a day is enough for such a heating system.

Such devices are capable of heating the building even during breaks between fireboxes. During the cooling process, the pipelines give up their heat for another 5-6 hours, thereby providing heating without consuming fuel. Water heating from a wood-burning stove has an efficiency of 80-85%.

Laying the boiler and installing a horizontal heat exchanger in it

A do-it-yourself heat exchanger using any of the options is installed in a brick boiler. The latter is laid according to the same principle as a brick oven.

The dimensions of a solid fuel boiler must be proportional to the volume of the premises that must be heated by it. The values available in the article are given based on a house with an area of 90-100 square meters. m. with 6 cast iron radiators and a distribution of 2 pipes (25-50 mm).

The choice and design of the boiler piping should be based on many factors:

How many circuits are there in the system?
How complex is the system?
Is there any other equipment available?

The entire boiler must stand on a solid reinforced concrete foundation.
The size of the foundation is selected based on the dimensions of the furnace. When laying a solid fuel boiler, the heat exchanger must be positioned so that the outlet pipe is the highest point. The height difference must be at least 10 mm. This is necessary to ensure that a plug of air does not form in the boiler while filling with water. This slope will also improve fluid circulation. Brickwork is done with your own hands, following the rules for bandaging the seams. The pipes should be approximately 2-3 cm lower than the brick wall itself. To prevent a decrease in efficiency, it is necessary to have a removable cast-iron plate on top of the boiler for easier cleaning. The smoke is discharged into a separate or main pipe. The pipe can be brick or metal.

Preparation and selection of installation site

To begin, lay out all the materials in front of you. But we do this at the place where the stove is installed. We choose the latter like this. For maximum efficiency, the heat generator is mounted in the corner of the room so that the heat spreads across 2 walls and is not lost in 4 directions.

In this case, it is necessary to leave a small gap from the walls, equal to approximately 150 mm. If the stove is used in a country house, it is advisable to provide a chimney during its construction and run the upper section of the pipe through the roof.

There is no need to lay a foundation for our unit, because with the given parameters the weight will be small. If the stove is planned to be massive, then it is better to prepare a concrete base.

Radiator assembly

Assembling radiators is a simple process, because it completely repeats the process of disassembling them. The sections are connected by nipples that have left and right threads on both sides. This way, the sections at the top and bottom will be pulled tightly against each other when the nipple is turned. When the gap becomes 2 cm wide, you should wind the asbestos-impregnated cord and only then tighten the nipples completely.

When the entire structure is assembled, you should wait for the drying oil to dry, and then check the joints for leaks. that is, supply water under high pressure to the radiator. This will ensure the subsequent use of the radiator and there will be no leaks.

The return and coolant supply pipes must be connected diagonally to the radiators. Holes that remain open must be closed with plugs. It is better to take inch pipes. On one side of the radiator there will be a right-hand thread, so there will be no difficulties with connection. On the opposite side, use a coupling with a squeegee and a nipple.

What dimensions should the chimney have?

Chimney placement options.

The draft in the chimney channel will occur due to differences in the height of the inlet and outlet, as well as due to temperature differences. To ensure continuous operation of any heating device, you will need to make a strong draft

Before starting masonry, it is important to decide what type of heating device will be used, what dimensions it has and how many channels it is planned to make

The number of channels can be determined taking into account the power of the heating device, fuel and the special requirements of the device manufacturer.

If the diameter of the chimney channel significantly exceeds the calculated value, the draft in such a channel will greatly decrease. As a result, there will be frequent interruptions in the functioning of a gas boiler or other heating device. If the channel diameter is smaller, this may impede the removal of combustion products. It is for this reason that in most cases the operation of boilers stops.

To make brick channels, you will need to use ceramic brick grade M50-75. You can also use concrete blocks that have channels with a square cross-section.

If you plan to use ceramic bricks to make a chimney, then you should know that its minimum cross-section is 14x14 cm. If you plan to purchase material with a round cross-section, then the permissible diameter is 15 cm or more.

In a brick chimney whose height is less than 5 m, the dimensions of the channels must be increased to 14x20 cm or 18 cm in diameter. Such structures should be made in the walls between rooms that are planned to be heated. In this way, it will be possible to create a certain protection of supporting structures from cooling, which in most cases leads to a weakening of traction.

It is necessary to try to group the chimney channels so that in the device that will be installed above the roof, their number is maximum. In this way, it will be possible to reduce the cost of manufacturing work and significantly improve the performance of the chimney device.

Features of water circuit pipe routing

The pipe system is connected to a heat exchanger installed in the furnace through sockets that are inserted through one of the walls. The water circuit in such a system is often arranged in the form of a two-pipe system. The wiring can be either lower or upper.

Naturally, the heating circuit must be fully equipped. The expansion tank is installed at the highest point of the line, safety and air valves are installed, and a safety unit with a pressure gauge is also included in the system; valves are connected at the inlet and outlet of the radiators.

The water circuit can be connected to a circulation pump; it significantly increases efficiency and allows for a more flexible approach to solving the issue of pipe routing. But there is a problem with this approach. If the pump stops working due to a power outage, the water will not circulate and will begin to boil in the coil.

In the cold winter, when the boiler is working at full capacity, one minute can be enough for the consequences to be disastrous. The stove, unlike a gas boiler, cannot be turned off quickly. For these reasons, it is recommended to use a combined wiring method.

Exiting pipes for heating

In the supply pipe, after it leaves the furnace, an acceleration manifold is installed, raising the pipe vertically by 1-1.5 m, and then lowering it to the level of the radiators. Sections of the highway are located at a slope of 3-5°. In case of emergency mode, coolant circulation will be natural.

It is better to install the circulation pump in the return circuit as close as possible to the expansion tank using a bypass, and the pump axis should be located strictly horizontally.

Laying a brick oven with a water boiler

Diagram of a solid fuel boiler.

Laying a brick oven with a water boiler is carried out in the following sequence:

The foundation is poured under the furnace location.
While the foundation is drying, mix a solution of clay and sand in a ratio of 1:2. Depending on the fat content of the clay, this proportion can be changed. Before preparing the mixture, the clay is soaked in water for 10-12 hours (large lumps of clay must be kneaded with your hands). Before starting masonry, sand and clay are thoroughly mixed.
Waterproofing is laid on the dried foundation - usually roofing material the size of the future furnace.
A layer of mortar is applied over the waterproofing, the first layer of brick is leveled and laid. It should be noted that it is better to use beautiful brick for the outer layer; it will look more aesthetically pleasing. The inner layers can be formed from defective or broken bricks.
Each layer of brick is carefully covered with mortar.
At the required height, a compartment for ash and the firebox itself are made.
A sheet of metal is placed in the ash compartment to make it convenient to remove ash residues in the future. The blower door is installed here.
Behind the firebox, in front of the chimney, a water boiler is installed. Brick ledges with metal corners are built for it. A level must be used to prevent air pockets from forming. A door for loading fuel is fixed in the firebox itself.
A metal plate is placed on top of the boiler, a chimney and a cleaning system are formed. It would be useful to make a separate door for cleaning the boiler from carbon deposits.
A metal sheet is fixed to the floor in front of the firebox in order to comply with fire safety regulations.

Boiler design diagram.

When you first light up a finished stove, you must ensure that the system is in good working order and that there are no leaks. The room must be ventilated, as often during the first heating there are unpleasant odors of burning industrial lubricants and heating clay. It is carried out for at least an hour with the maximum possible amount of fuel.

A brick stove with a homemade boiler is one of the best ways to heat small country houses, which will allow you to enjoy the warmth on cold winter evenings and save your budget.

Cast iron radiators as a boiler

You can build old radiators into a brick stove, and they will serve as a boiler. Cast iron built-in water heating elements have their own characteristics, for example, cast iron does not react very well to open fire. Nevertheless, this method is used quite widely. You can use the M-140 radiator, which can easily be found at demolition sites of five-story buildings. If you weld a dozen sections, you will get a heater with an area of 3 sq.m and 18 liters of capacity. A flat boiler with the same characteristics would require a lot of space. Such boilers can heat large areas.

Before the radiators are welded together, they must be disassembled, cleaned of dirt and thoroughly rinsed with a hot 6% hydrochloric acid solution. Then rinse again with water. Then change the cardboard spacers located between the sections, as they will simply burn out. Instead, use asbestos cord impregnated with graphite powder and natural drying oil.

The radiator elements should be assembled in a certain sequence. Screw nipples with their right and left threads into the sections to be connected, then wind an impregnated asbestos cord around them and tighten both nipples with a wrench, making sure that there is no misalignment of the sections. After connecting two sections, you can attach a third, then compress the radiator to check the quality of the assembly. Now you can install the risers.

You can position the cold water inlet and hot water outlet diagonally. The other two holes can be plugged to allow water to circulate through the entire volume. The radiator must be mounted in the smoke duct located behind the firebox. This will help avoid contact of cast iron with open fire: the boiler will be heated by hot gases.

You can increase the natural circulation of water in such furnaces by running a return line pipe through its foundation and the space under the floor, which will increase the temperature difference between the return and hot lines. The battery in the furnace is installed with a slight slope to allow air to escape and enter the system. For cleaning, you can build an additional door into the smoke channel itself.

Boiler installation

When implementing plans to create a combined heating system, it is important to pay attention to some features. Water-heated brick stoves have many options, each of which differs in material, type of main element and other nuances. Ignoring technical and construction requirements will certainly lead to the rejection of the entire work

Ignoring technical and construction requirements will certainly lead to the rejection of the entire work.

The boiler must fit completely into the firebox. However, in practice there are incidental situations when part of the heat exchanger is located outside the stove. This is unacceptable, because the main task of the unit is to heat the coolant. The boiler is made in the shape of a “P” from pipes or sheet iron. All its elements are hollow and are designed to remove heat.

The preferred option is from pipes. It has a larger convection area and allows the flame to reach the cooking surface to cook food. In addition, attention is required:

Dimensions. It would seem that a massive product is needed that can heat a lot of water and provide heat to a decent-sized structure. But that's not true. The boiler itself is made of very modest dimensions - 75 * 50 * 30 cm (length, width, height). The convection surface of such a device is enough to heat a house up to 200 square meters. Installing a pump for forced circulation of coolant increases productivity by up to 50%. Boiler. Its shape is designed in such a way that the heated surface area is as large as possible

It is very important to install it in the center of the combustion center. This is the only way to achieve high efficiency of water heating. Peculiarities

A small gap must be left between the walls of the furnace and the surface of the boiler. The optimal distance is considered to be 5 millimeters. It is quite sufficient to level the free movement of the metal during thermal expansion.

The heat supply and outlet lines are carried out in strict accordance with the laws of physics. It is known from school that hot flows tend to go upward, while cold flows are always directed downward. Therefore, the pipe supplying hot water to the house is always adjacent to the boiler at the top point, and the channel with the “return” is at the lowest point. This arrangement eliminates the accumulation of hot steam, which poses a serious threat to the integrity of the system.

Stove water heating device

The furnace for the heating system in question should ideally be calculated and built at the same time as the house. If a residential building has already been erected, then it will be difficult to install a brick stove structure in it. And often this turns out to be completely impossible due to the need to build a solid foundation and rebuild the rafter system.

A furnace for water heating in a private house can be made not only of brick, but also of steel in the form of a potbelly stove with heat exchange pipes around the firebox for heating the coolant

Stove-based water heating consists of:

the stove itself (metal or brick);
a heat exchanger inside or around the stove firebox, as well as in the form of a coil around the chimney;
a circuit with coolant distributed throughout the house and an expansion tank in the attic.

Also, in some cases, this heating system is supplemented with a circulation pump and a hydraulic accumulator. However, this extended option is used extremely rarely, since it requires an uninterrupted power supply and leads to an increase in the cost of the entire circuit.

And the main advantage of water stove heating is the low cost of the device. It is not worth supplementing it with expensive and breakage-prone elements.

Water circulation diagram in the circuit

The water heating system in houses is built with natural (gravitational) or forced circulation of the coolant. If it is made on the basis of a wood stove, then it is best to give preference to the first option.

The wiring diagram with natural water circulation is cheaper than the forced analogue, and also, unlike it, does not require power supply

It is recommended to install water stove heating only in one-story houses with an area of up to 150 m2. In this case, it can be made gravitational without additional pumps.

If you need to heat a cottage of a couple or more floors, then it is better to do this using a more powerful boiler. The furnace for such buildings will have to be built simply huge, which is expensive to implement. Yes, and you will have to put considerable amounts of fuel into it each time. But doing this is highly not recommended due to the increased risk of fires.

A classic stove heating system with natural water circulation consists of:

heat exchanger as part of the stove;
metal pipeline circuit;
radiators (usually replaced with thick pipes in rooms);
expansion tank.

If you decide to do water heating in a country house yourself, then it is better to design it according to this scheme. Installation and calculation of this option is easier than with forced water movement.

A system with a circulation pump is more suitable for boilers; based on a stove, it loses its increased heat transfer efficiency

If the boiler is automated and constantly heats water as needed, then the wood-burning stove is heated once or twice a day. It is at these moments that the coolant in the furnace firebox heats up to release heat into the rooms. Afterwards, driving it with a pump through the pipes of the circuit is pointless. Nothing will heat the water in a cold firebox anyway.

When choosing a wood or coal stove, owners of private houses usually expect to receive an autonomous heating system. If you install pumping equipment in it that requires power from the electrical network for operation, then it will be difficult to talk about autonomy.

Oven - brick or metal

A brick oven takes longer to heat up, but it also takes longer to transfer heat to the space around it. The steel counterpart, on the contrary, heats up quickly and cools down just as quickly after the fuel burns out. This problem is partially solved due to the presence of large volumes of coolant in the water circuit.

However, the more water that has to be stored in the system, the more expensive it becomes in terms of materials.

A metal potbelly stove with a water coil for the heating circuit in private homes can be placed directly on a wooden floor without installing a special foundation

A steel furnace for water heating with a power of 5–15 kW - without fuel and water it is a structure weighing 100–300 kg. Such a potbelly stove can be safely placed on reinforced logs. Stove foundations need to be poured when the stove weighs more than 700–800 kg. Now, if it is brick, then you definitely can’t do without concrete work.

Compared to a metal stove, a brick stove weighs more, costs more and is more difficult to install. However, it has higher efficiency and less risk of freezing the circuit with pipe rupture due to the formation of ice inside. If you decide to do everything completely for yourself and permanent residence, then it is recommended to choose the brick option.

Pipes - stainless steel or metal-plastic

If the heating system is built on the basis of a hot water boiler, then it can be piped not only with steel pipes, but also with metal-plastic and polypropylene pipes. However, if the water is heated by a wood-burning stove, then the circuit with the coolant from it should be created only from stainless steel.

With a large load of firewood, the water in the furnace coil can quickly heat up to 100 degrees and boil; only steel can withstand such temperatures for a long time

Metal-plastic is designed to work with coolant heated to 90–95 °C. For a short time it can withstand heating up to 110–120 °C. At the same time, the automation of boilers and boilers initially does not allow the water to warm up to such degrees. For heated floors it heats up to 30–45 °C, and for radiators up to 60–65 °C.

However, in the case of a wood-burning stove, temperatures under a hundred are not only possible, but far from uncommon. It is not recommended to take risks and play Russian roulette by piping this stove with metal-plastic pipes. It is best to give preference to more reliable stainless steel.

In addition, the pipes coming out of the furnace from the coil for connecting the circuit pipes will definitely heat up to very high temperatures. They are separated from an open fire by less than half a meter. It is dangerous to connect any plastic pipes to them due to the risk of them melting.

Heat dissipation - radiators or register

Heat is supplied from the stove to the heating circuit in portions of several hours, while wood or coal is burning in the firebox. If there is not enough water in the heating system, the house will quickly dry out. Therefore, in villages, such heating is usually made from thick steel pipes, and not on the basis of radiators more familiar to city dwellers. The heating register for wood burning stoves is simply perfect.

The classic scheme of water stove heating with natural circulation involves direct contact of water with the atmosphere through an expansion tank, but air in the coolant is contraindicated for conventional batteries

A stainless steel pipe with a diameter of 80–120 mm laid throughout the house is a heating register, consisting of a supply from the stove and a return to it. In the room farthest from the firebox, these lines are connected together, and in the remaining rooms they are laid in the form of two pipelines along the outer walls.

The register does not look as aesthetically pleasing as the radiator. But the first option is much cheaper and easier to make yourself than the second. To implement it, you just need to have experience in handling a welding machine.

The heat transfer area for such a circuit is calculated by multiplying the PI number by the diameter and length of the pipe. Plus, in the calculations it is necessary to take into account the thermal pressure in the supply and return, as well as the vertical distance between the pipelines.

However, often such calculations are not made, but a pipe with a diameter of 80–100 mm is taken and laid around the perimeter of the entire residential building with a loop in the back room. In this case, heat transfer is adjusted “by eye” and experimentally as a result of adding a particular volume of fuel to the firebox.

It’s not for nothing that register circuits coupled with water furnaces are so common. You don’t even need to calculate them, just take a suitable pipe and weld it together.

Selecting a heat exchanger for the furnace

The heat exchanger in the stove can be made of copper, steel or cast iron. It is better to immediately exclude the copper option due to the high price. Soldering such a device yourself is extremely problematic.

Cast iron batteries should be installed inside the firebox with caution - due to temperature shock, individual sections may become detached from adjacent elements

Cast iron is superior to steel in terms of technical parameters. However, making a heat exchanger for a wood-burning stove out of it yourself seems problematic. You can only take an old battery for this. But here we must take into account that the seal between its sections will burn out in the firebox. And this is a direct path to loss of tightness and water escaping into the combustion chamber.

If it is decided to make the heat exchanger from a cast iron battery, then it is best to take the MS-110-300 or MS-90-300 models for this. They are small and will easily fit in the firebox. Their heating surface area for each rib will be about 0.14–0.16 m2.

Based on these numbers, you can estimate how many sections will be required for a particular circuit. For every 10 square meters of house area, 1 kW is needed, which will be approximately equal to 0.1 m2 of heating area of a cast iron heat exchanger.

The fins of a cast iron radiator are usually connected using heat-resistant rubber gaskets. In a stove firebox, such a rubber seal will burn out; it needs to be replaced with an asbestos cord

Another point about using a cast iron battery as a heat exchanger is the difficulty of cleaning it from soot from inside the firebox. From time to time the combustion chamber needs to be cleaned, and the raised ribs of the cast iron will greatly interfere with this.

The most optimal option for a heat exchanger is steel in the form of:

a coil of several tubes;
sheet steel shirts.

They are made from low-carbon steel St10...St20 with a thickness of 4–5 mm. If you take tubes, then with a diameter of 30–50 mm.

The easiest way to make a steel heat exchanger is from sheet steel - however, only the surface facing the inside of the firebox towards the fire will participate in heat exchange

The tubular version is more efficient in terms of heat transfer, but it is also more labor-intensive to manufacture.

To calculate the heat exchanger, use the formula:

Qy=K*(Tcp-Tk)

Where:

K is the heat transfer coefficient of the material (15–20 is taken for low-carbon steels, and 50 for gray cast iron);
Tcp – average temperature of the heating medium in the furnace (Tmax+Tmin)/2;
Tk – average coolant temperature (Tsupply + Treturn)/2.

If wood is burned in the stove, then Tcp=(700+300)/2=500 °C and Tk=(80+60)/2=70 °C. As a result, Qy=15*(500-70)=6450 kcal/hour. That is, per square meter of the heat exchanger surface facing the fire will be approximately 7.5 kW/hour.

For coal, the calculations are as follows: Tcp=(1000+600)/2=800 °C and Tk=70 °C. Qy=15*(800-70)=10,950 kcal/hour=12,734 W/hour. A square meter of heat exchanger surface will give about 12.7 kW/hour.

Next, we divide the power required to heat a particular house by the calculated figure, depending on the plans for using a particular type of fuel.

For example, for a cottage of 150 m2 you need about 15 kW. If it is heated with wood, then a heat exchanger with a heat exchange area of 15/7.5 = 2 m2 will be required. This is the surface that faces the flame and heats up.

If a tubular coil is selected, then its length is calculated by the formula:

S=2*3.14*D*L

Where:

S – design area;

D – tube diameter;

L – required length.

The parameters of a steel sheet jacket are even easier to calculate; it usually consists of two rectangles on the sides of the combustion chamber.

Flat-plate heat exchanger

A popular option, which is used both for stoves in the bathhouse and for the home. They are the simplest to manufacture, the surface is easy to clean from soot accumulations, installation is possible both vertically and horizontally, and the efficiency is relatively high.

A flat boiler can have a high volume, so you can take hot water for washing directly from the heating system. An expansion tank with an increased linear size is installed, into which water constantly flows after the level drops below critical. This option is quite convenient and helps solve several problems at once, but there is also a condition - the room temperature in winter should not drop to minus.

Key disadvantage: a sharp decrease in heat transfer from the furnace walls. This type of heat exchanger is made in the shape of the letter “P” and is installed around the perimeter of the firebox, bypassing the door. As a result, it turns out that the temperature of the external walls is quite low, as a result, warming up the room takes much longer. This is critical only if the stove is installed in a bathhouse; for residential buildings, where the stove is constantly heated, increasing the warm-up time by several hours does not play any role.

Thus, when choosing a flat boiler, think about how you can increase the heating rate. One option is to enlarge the heater and place it directly above the firebox. Second option: using a metal chimney for heating, increasing its length.

Installing a coil on a pipe

This is an excellent and fairly simple way to increase the efficiency of the stove. Flue gases heat the pipe to extremely high temperatures. The outer coil, like the inner one, helps reduce the temperature and somewhat cool the outer surfaces of the chimney. An external water heat exchanger is especially often installed on metal chimneys. This is an excellent auxiliary device for heating small spaces.

This heat exchanger has two pipes. The top one is connected to a pipe going to the storage tank, the bottom one is connected to the heating circuit. It is easy to make such a structure, as well as attach it to a pipe.

Simple rules for an efficient heat exchanger

The operating principle of stove heating.

If the house has a ready-made brick stove, then organizing water heating with your own hands is a fairly simple task. To do this, it is enough to place a homemade boiler in the firebox in the form of a coil or any other shape. The main thing to consider is:

The height difference between the fluid outlet from the heat exchanger and its inlet;
It is necessary to ensure the maximum possible surface area;
The heat exchanger should not interfere with the loading and combustion of fuel.

If you are building a stove with your own hands, then the boiler for a brick stove can be made as efficient as possible. To do this, several important conditions must be met:

Combustion products must leave the chimney as cold as possible;
Greater heat transfer of furnace gases inside the furnace increases its efficiency;
It is best to place the heat exchanger in the chimney rather than in the firebox.

These rules may seem somewhat strange, because logically, the heat exchanger should be heated best by the open flame of the firebox. However, it is necessary to take into account other processes occurring in the furnace. From a physics point of view, flames are burning fuel particles. And if we take heat away from these particles, then they will not burn completely, which will reduce the usefulness of the stove.

Diagram of connecting the boiler to the heating system.

In addition, for better heating, the coolant must move towards the heat flow. Only in this way is the temperature difference between different parts of the coolant maintained, increasing the heating efficiency and ensuring better circulation within the system.

Another advantage of this arrangement of the heating tank is that less condensation forms on it, which contributes to the absence of corrosion.

Application of pyrolysis furnaces

Long-burning stoves using wood, pellets or sawdust are often used to heat utility rooms and workshops, garages, and greenhouses. They can also be used to heat a house, but it is necessary to ensure that the stove is sealed, as carbon monoxide may be released.

If you use a pyrolysis stove to heat a garden or residential building, it is better to equip it with a water circuit connected to the heating radiators, and install the heating unit itself in the boiler room.

This article talks about how to simply make a smokehouse for cold smoking, which at home will help you prepare real delicacies from the most ordinary products. You can find out how to make a smoke generator for cold smoking by looking here. Here you will find the most understandable drawings for creating an effective potbelly stove with your own hands: https://gidpopechkam.ru/pechki/burzhujki-chertezhi.html

Laying a furnace with a boiler

If you decide to delve deeper into the topic, you may decide to install a Kuznetsov bell furnace, the operating principle of which is the free flow of gases, which does not require additional external energy. The drawings are available on the Internet. Here we will talk about a simpler design. So, first you need to pour a foundation, the depth of which is 50-70 cm. Sand should be poured onto the base in a layer of 10-15 cm, crushed stone, gravel or construction waste should be laid on top, and a space of 25-30 cm should be kept for pouring cement. It is best to prepare the solution for the foundation without using sand, replacing it with screenings, the ratio will be approximately 1:6. Roofing felt should be laid under and on top of the screed for waterproofing.

Then you should make a solution of clay + sand in a ratio of 1: 2.5, however, the proportions may vary depending on the level of fat content of the material

It is important not to leave lumps, and therefore the clay should be soaked in the evening. If the mixture slides off the trowel, leaving small streaks on it, then the concentration is appropriate

Before starting masonry, it is necessary to lay out roofing felt over the area of the poured foundation and cover it with mortar. The first row is laid out with a pallet completely made of bricks, where the furnace will then be laid. Then the first row of the furnace contour is laid out, then the next, etc. During laying you will need order.

Now the firebox, ash compartment and ash pit are made. The doors are secured using galvanized wire or a strip of galvanized sheet. It is necessary to trim the brick above the doors using a grinder, but it is best to make one of them with a wedge, so that the masonry will not crack. Make protrusions for the boiler on the brick in advance, which can also be cut with a grinder. Do not forget that the instructions require level installation, and therefore you should use a level. Then the firebox and the rear part of the structure are installed, where the chimney with cleaning is located. The pipe should protrude at least 50 cm above the roof.

You can make your own stoves for heating your home without being a pro in this matter. They are versatile and have a high heat transfer coefficient. The big advantage is their autonomy, since they do not depend on external energy sources. Such boilers can have any size depending on the area of the heated room.

Integrating a stove into an existing heating system

If you already have a heating system that has previously been used with a different type of heating, you can connect a furnace to it. For example, it can become a replacement for a gas boiler.

Modern heating equipment usually does not contain a heating tank. But, it has a heat exchanger that performs a similar function.

The cost depends on a lot of factors - material, size, efficiency, maximum permissible heated area, etc. Moreover, there are models that allow not only to heat the house, but also to provide a full-fledged hot water supply system.

Factory stoves usually allow the use of both classic wood and coal, and pellets, which is a compressed wood material used as fuel.

Water boiler made of cast iron radiators

M-140 radiators are suitable for this type of boiler. They are quite easy to find, since large quantities of them are sent to scrap when radiators are replaced with more modern ones or old buildings are demolished. Each section of such a radiator has a capacity of 1.5 liters, and their area is 0.254 square. That is, if you combine 12 sections, the volume of the heat exchanger will be 18 liters, and the area will be 3 square meters. Such a boiler has a capacity of up to 100 square meters. So it’s quite enough for a residential building.

In order to use the radiator, you need to modify it a little. Initially, you should remove the cardboard gaskets located between the sections with your own hands. The best replacement for them would be an asbestos cord, which must be impregnated with drying oil with the addition of graphite. Thus, the gaskets will be protected from burning through at high temperatures.

In addition, before starting assembly, the sections should be washed from the inside using a 6% solution of hydrochloric acid, and then washed with water. This will clean the pipes from dirt and rust that has accumulated there during operation.

Heat exchanger construction

Installation diagram of the heat exchanger and storage tank.

You can easily build an effective boiler with your own hands. If it is made in the form of a tank, then high-quality steel is required, which can withstand thermal loads and corrosion due to the coolant. In addition, the manufacturing material must have high thermal conductivity to increase the efficiency of the system.

The thickness of the tank walls should be within 4-5 mm, which ensures its strength while simultaneously heating quickly. There are no standard sizes for such a heat exchanger; it all depends on the configuration of the existing or planned furnace. The main thing is that the height of the tank is at least 500 mm for better circulation.

If the heat exchanger is a coil or another circuit of pipes, then there are also some nuances. Pipes for the manufacture of such structures must be thick-walled and have no seams. If it is difficult to find a seamless pipe, then it is necessary to weld the existing seams to prevent possible coolant leakage.

The inlet pipe is best located at the top of the structure, and the return pipe is located in any convenient place. The pipes are not butt welded, but with chamfers to avoid unwelded areas that will leak in the future. The minimum distance between the knees of the structure is 5-6 cm, so that the heating of each knee is maximum. Before placing such a boiler directly into the oven, it is necessary to fill it with water and check for leaks, which are promptly eliminated.

When placing the boiler directly into the furnace, you should adhere to the level, but minor deviations are allowed.

Brick chimney construction

Brick chimney laying diagram.

Laying should begin with the mounting tube. It should be laid out in compliance with the brick dressing. After this, a cutting (fluff) is formed. It needs to be laid out from 5 bricks. The channel will have dimensions of 270x140 mm. The external dimensions of the cutting are 450x590 mm. This can be achieved by inserting brick halves. To maintain the dimensions of the channel, you will need to insert brick plates inside. In this case, the channel will not change.

The next row will have dimensions of 650x510 mm. Brick plates 6 cm thick are mounted inside. At this stage, the cutting will begin to take its shape. In the next row, the external dimensions will be 710x570 mm. Inside you will need to install material 9-10 cm thick.

After this, the fluff ends. In the next row, be sure to observe the dressing. If you need to make a cut of greater height, you can install another row; the dressing should be done under the bottom row.

To allow the riser to exit outside, you will need to prepare a hole in the roof. Next, the riser should be routed through the roof. The rest of the work is done on the roof.

At the next stage, the riser is laid out. You need to carefully monitor the dressing of the brickwork. The riser must be placed several rows above the roof. After this, the otter lays out. The internal plates are selected so that the channel does not expand.

After this you will need to form the neck and head. The actions will be the same as in the case of erecting a cutting.

Benefits from combining the two systems

A traditional stove-heater consists of a combustion chamber, grates, ash pan and channels for smoke removal. All the attributes of a familiar Russian stove are known to every village resident. Modern boiler furnaces are practically no different visually.

But they have different characteristics:

An ordinary rural stove can produce a little more than 6500 kcal of heat in one hour of full operation. This energy is enough to create a comfortable microclimate in a small house. For example, this heating method is suitable for a summer house.
If you install a water boiler, its productivity will be 2.5 times greater. Naturally, the area of the heated room will also increase proportionally. The amount of fuel burned is the same. And savings are achieved through improved heat extraction. That is, less warm gases are released into the atmosphere.
Next, a very important nuance becomes clear. If you combine convection (oven) and water (boiler) heating systems, the efficiency increases multiple. The point is that when both systems are running, their performance is additive. In other words, a tandem of two heating methods produces about 21,000 kcal per hour of operation. This is quite enough to heat about 300 square meters of living space.
The positive aspect of this method of heat supply is the availability of energy resources. In most cases, firewood or a combination of wood and coal is used. The cost of these types of fuel is low, and acquiring them is not particularly difficult.
The oven does not need to be lit all the time. Fuel is added 2 times a day. A comfortable microclimate is created in the house, regardless of the temperature outside the window.
If the efficiency of a traditional stove did not even reach 50%, then the combined option reaches 85%. And for wood heating this is almost an ideal indicator.
The price of materials is low. The cost is usually determined by installation work.

How the system works

The simplest water circuit is with natural circulation of water flow. Its basis is a simple physical phenomenon: the expansion of liquids when they are heated. The unit that creates pressure is an expansion tank (a container for collecting water), installed in the attic or attic.

The water circuit is a closed system. The boiler heats the water in it and, expanding, it is directed through a pipe into a storage tank. The movement is carried out under pressure created by the cooled water constantly entering the boiler and passing through the entire system. Boiling water from the expansion tank is directed by gravity down through the pipes leading to the batteries. Having given off the heat, it returns to the tank and heats up again.

Installing a pump will help to significantly increase the pressure in the system and speed up the circulation of the coolant. At average outdoor temperatures, it can be turned off and the circuit will function on the natural movement of water. This will save you on your energy bills. Water enters the pump with the check valve closed. By turning it off (leaving it open), the entire volume of coolant is directed to bypass the pump.

Such a stove can be loaded not only with wood or coal. When using alternative fuels, it is possible to complicate the structure of the system by adding:

granule storage tank;
a mechanism that feeds pallets into the firebox (pneumatic or auger).

You can make the operation of the furnace easier by installing an automatic system for regulating its operation and forced ventilation.

Rules you need to know when building a chimney

Diagram of a brick chimney.

The structure for solid fuel boilers is made together with the walls of a private house. These elements are constructed according to a single principle, and it does not matter whether the channels will be used as ventilation or smoke. You will definitely need to build a foundation for the chimney. The base structure can be made of brick or concrete.

In all cases, a foundation project is prepared. During the design process, it must be taken into account that its height must be at least 30 cm, and its width must be such that the base structure extends beyond the border of the chimney device by 15 cm or more. If the chimney is made as an element of the external wall, then you need to know that the lower part of the chimney base must be placed at the lower level of the wall base.

During the construction of chimney structures, special attention should be paid to the quality of tightness. To make a durable brick chimney, you will need to follow the rules

The material should be laid so that the seams overlap the elements of the next row. In most cases, the same mixture is used as for the construction of load-bearing walls of the structure.

In the process of making a chimney for a solid fuel boiler, it must be taken into account that its internal base must be smooth.

Therefore, when performing construction work, you need to use a template. The walls between the elements must be at least half a brick thick. For ventilation elements, the thickness of the partition should be 2 times less.

At the end you will need to make a header. The extreme parts of the element must protrude beyond the structure by 10 cm or more. The outlets of the ventilation ducts must be created under the head; in most cases, 2 walls are used, which are placed opposite each other. This placement method will prevent air from being blown in.