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Boiler for water heating for home drawing. Using a homemade boiler for water heating

Boiler for water heating for home drawing. Using a homemade boiler for water heating

Firewood is the most accessible, environmentally friendly and inexpensive type of fuel that has been used by man since the beginning of time. The main advantages of wood heating systems are energy independence, high efficiency and relative ease of operation. Despite the variety of gas and electric heating systems, wood heating boilers have not lost their relevance and are popular among the majority of Russians. Wood-burning installations have another undeniable advantage - their simplicity of design, which allows you to easily make a boiler for heating your home with your own hands. This will be discussed in this publication.

Design and operating principle

Before moving directly to the instructions for creating a homemade solid fuel boiler, you need to understand how a wood-burning boiler installation works.

In the simplest wood-burning boiler with a heat exchanger, when wood burns, thermal energy is released, which heats the walls of the heat exchanger (water jacket) and the coolant itself. Combustion products, passing through the soot collector, are discharged through the chimney. The draft is regulated by the position of the ash pan door and the chimney damper. The heat exchanger is connected to a heating system, which includes main pipes, radiators and an expansion tank. The circulation of the coolant can be carried out either naturally or forcefully by turning on a circulation pump in the heating system (CO).

The simplicity of such a boiler is “compensated” by the low efficiency of this design: most of the thermal energy literally “flies down the chimney” along with the combustion products. But the main disadvantage is the low level of automation: all operations for loading fuel into the firebox and maintaining the combustion process must be done manually. Therefore, wood-burning pyrolysis combustion boiler systems are considered the most popular. Making such a heating boiler with your own hands is not difficult for any home craftsman.

Homemade pyrolysis boiler

Fuel is loaded into the fuel chamber immediately in full. Under conditions of lack of oxygen in the gasification chamber, fuel smoldering with the release of pyrolysis gas. Smoldering occurs with the release of heat, which is spent on heating the coolant in the heat exchanger. Pyrolysis gas, together with combustion products, enters the afterburner, which in this design also serves as an ash pit. Due to the fact that the access of oxygen to the afterburning chamber is not limited, the combustion of combustible gas occurs with the release of high temperatures, as a result of which the efficiency of the device increases significantly. The entire operation of a pyrolysis boiler can be divided into four stages:

At the first stage, the wood is dried and pyrolysis gas is released from the fuel.
The second stage of operation of this installation is the combustion of a mixture of secondary air and combustible gas in the afterburner.
The third stage is the passage of hot gases through the heat exchanger.
Removal of combustion products that gave off the lion's share of thermal energy.

A homemade solid fuel boiler must be equipped with controls and automation that make its maintenance as simple and safe as possible. The operation of the installation can be controlled by changing the position of the ash pan door and the smoke exhaust damper. The automation of a homemade wood-burning boiler is usually represented by a pressure gauge, an air vent and a blast valve (safety group). Quite often, domestic “Kulibins” equip their heating installations with: a temperature sensor, thanks to which the primary air fan is turned on and off, as well as pressure sensors in the water circuit.

Let's digress a little, because we want to inform you that we have compiled a rating of solid fuel boilers by model. You can learn more from the following materials:

Preparation of materials and tools

Before answering the question of how to make a solid fuel boiler yourself, you should decide on the design of the device. The simplest option is a classic combustion boiler unit. In other words, a “potbelly stove” with a water heat exchanger. A more efficient boiler unit is considered to be a classic combustion installation, divided into two chambers: in the lower one the process of burning wood will take place; in the top - heating water for the needs of the owner.

After choosing the optimal design of a wood heating installation, you should decide on the size of the device. Ideally, the next stage of creating a heating boiler with your own hands is drawings, which can be ordered from a specialized organization.

Important! We deliberately do not publish drawings of a wood heating installation. All information is provided for informational purposes only.

Material selection

If you have mastered the art of welding and the possibility of plasma welding, then to create a wood-burning boiler you need to use sheet metal 3-5 mm thick. Boiler blanks are cut out of metal and welded according to the diagram.

The simplest housing option is a piece of thick-walled steel pipe, 4-6 mm thick; length 800 – 1000 mm; with a diameter of 300 mm. Grate bars and supports can be made from reinforcement, rolled steel or channel bars. You will also need metal to create the bottom of the boiler (50 mm thick), the lid (3-5 mm thick), the air distributor (10 mm thick), the hinge and the valve. In addition, you need to stock up on a metal pipe with a diameter of 60 mm. The height of the pipe should be 50 mm greater than the height of the housing. The chimney will require a steel pipe with a diameter of 100 mm.

To assemble a simple wood-burning boiler, you will need a tool, namely:

Welding machine.
Powerful angle grinder (“Binder”).
Drill and drill bits for metal.

The assembly process can be divided into several stages:

A circle corresponding to the diameter of the case should be cut out of 50 mm metal. After welding, it will be the bottom of a wood-burning boiler.
A circle should be cut out of metal, which has a diameter 20 mm smaller than the body. After which, in the middle of the circle it is necessary to drill a hole with a diameter of 20 mm. A piece of air distribution pipe (d 60mm) should be welded to the hole. On the opposite side of the circle, impeller-shaped plates are welded.
A circle is cut out of sheet metal 3-5 mm thick, which will serve as the top lid of the boiler. In the middle of the circle, a hole should be made in which the air distribution pipe (d 60 mm) will move freely.
The chimney is welded to the top of the body.

Important! For proper smoke removal, it is necessary that a section of the chimney pipe, 50 cm long, be strictly horizontal from the boiler.

Fuel is loaded into such a boiler through the top cover. It is necessary to load the fuel chamber space as tightly as possible so that there are no gaps left. Ignition is done through the top. As soon as the fuel ignites, you should install the air distributor and the top cover in their original places. As it burns out, the air distributor disk will lower, increasing pressure in the lower chamber. Due to this, the amount of oxygen in the fuel chamber will be reduced, and the combustion process will turn into slow smoldering. The entire design of this wood-burning boiler looks like this:

Tip: this homemade boiler installation scheme requires a chimney. If it is not possible to arrange a smoke exhaust duct, but the need for a heating device exists, then you can create a simple induction heating boiler with your own hands, if you have a welding inverter at hand.

A winding of 50-100 turns should be made from copper wire with a cross-section of 2 mm, the core of which will be a steel pipe. Under the influence of magnetic induction, the section of pipe (core) through which the coolant will move will be heated.

In our country there are quite a few private houses heated with coal and wood. A classic stove and solid fuel boilers differ little from each other. Their efficiency is approximately the same. The design of the heating boiler is quite simple, which allows it to be made in a home workshop from available materials using non-professional tools.

Moreover, a number of improvements can be made to the design of equipment used for heating and cooking. These changes will improve its efficiency, which will lead to lower costs for these purposes. On the site you can find many descriptions with videos and photos illustrating the boiler manufacturing process in detail.

Such a guide allows you to clearly see and imagine all stages of the work. Detailed written instructions on the technology for producing heating devices with your own hands complement the descriptive part of the project well.

Design features of a solid fuel boiler

This equipment has much in common with a conventional stove, but it also has a number of differences regarding the methods of transferring heat to the room. The classic heating boiler device consists of the following elements:

bunker for burning solid fuel, equipped with grate bars to supply the required amount of air;
water container, which is the coolant in the heating system or tubular heat exchanger;
chimney to create the necessary draft and remove combustion products;
throttle system to regulate air draft and shut off channels after the fire in the stove has completely died out.

To ensure uniform temperature conditions in residential premises, the heating system is equipped with a water heat accumulator. It is a container of a calculated size, installed in the upper part of the boiler and accumulating thermal energy during active combustion. After this process stops, the liquid circulates in the system and heats the air.

An additional stainless steel tank installed above the heat accumulator is a source of hot water for domestic needs. It is not a mandatory element of the heating system and serves to create more comfortable living conditions in a country house or country house.

Before starting work, you should draw up accurate drawings of the heating boiler and its components. You can find typical devices in specialized literature, in periodicals or on the Internet. However, for a more rational use of living space, it is optimal to develop an individual design for heating equipment that runs on solid fuel. They were created to make life easier for their owners.

Materials and tools

To make our own solid fuel boiler we will need:

steel sheet with a thickness of at least 5 mm;
metal corner;
cast iron grate;
steel water pipes of different diameters;
doors for the combustion and ash bunker;
oven throttle valves;
stainless steel sheet for the manufacture of heat accumulators and containers for household needs;
sifted river or quarry sand.

You can purchase all the necessary materials from specialized companies that sell rolled metal. As a rule, their selling prices directly depend on volumes. A one-time purchase of everything you need according to the list will save money on the family budget.

Having carefully studied the drawing of the heating boiler, you come to the conclusion that welding will be required during its manufacture. Accordingly, the list of required tools will look like this:

inverter-type welding machine or any other suitable for use at home;
an angle cutting machine with sufficiently high power; in everyday life this power tool is called an angle grinder;
pliers and forceps;
electric drill with a set of drills;
measuring instruments: tape measure, squares and building level.

It goes without saying that the master must have the necessary welding skills. In addition, you will need experience working with metal-cutting tools and the necessary protective equipment for the eyes and skin of the hands and face.

Home technology for the production of heating equipment

In search of an answer to the question of how to make a heating boiler with your own hands, you quickly come to the conclusion that there is nothing particularly difficult about it. Subject to proper organization of the production process. It is more convenient to make individual parts on a workbench in an equipped workshop or other place where you can make a workbench.

Manufacturing of body parts

The basis of any is the firebox, where the temperature reaches 1000 ⁰C and its assembly will require materials with the appropriate characteristics. The procedure for manufacturing the case is as follows:

In the absence of heat-resistant steel, you can get by with conventional steel, but to ensure the durability of the unit, its walls are made double. The front, back, side and bottom walls are cut from steel sheet using an angle grinder;
Drawings of heating boilers indicate the exact dimensions of all parts, which are transferred to rolled metal using a measuring tool and a large ruler. In addition to the walls of the chamber, the required amount is cut from steel profile pipes to use them as stiffeners. Reinforcements for joints between individual parts of the furnace are made from angle steel;
It is necessary to make a rectangular hole in the front wall, corresponding in size to the doors of the combustion and ash bins.

Helpful advice: to make a through rectangular hole of the desired configuration, apply markings to the metal, and drill the sheet in the corners using an electric drill. Using an angle grinder, we make a through cut in the middle part and move it from the center to the edge. This will avoid unnecessary damage to the sheet.

Manufacturing of water tanks and heat exchangers

The efficient design of the heating boiler includes two water tanks. They are made from stainless steel sheet, the welding of which requires special equipment and certain qualifications. Here it is better to trust the professionals and order these containers from a specialized workshop.

The design of the heat exchanger is a set of water pipes. Using a welding machine, they are connected in such a way as to form a flow circuit with the largest possible external surface. This will ensure the fastest and most complete heat transfer from the burned fuel to the coolant.

Boiler assembly

The design of heating boilers is characterized by high metal consumption, and the final product will have quite an impressive weight. Based on this, it is better to carry out assembly at the installation site of the heating equipment.

A foundation of heat-resistant brick must be made under the boiler. The bottom of the ash bunker is placed on it, along the perimeter of which the inner walls of the boiler are placed vertically and connected by welding.

Inside the finished housing, grate bars are laid on pre-welded guides and heat exchangers are mounted. From the outside, stiffening ribs made of a steel rectangular profile are welded to the hopper in a vertical position. Now making heating boilers with your own hands is moving into the final stage. All we have to do is install the outer walls and the top plate.

Prepared sand is poured between the walls, which performs double duty as an additional heat accumulator and protects the walls of the combustion chamber from overheating and rapid burnout.

Advice: For backfilling, it is better to use washed sand that does not contain dust or organic inclusions. It must first be heated over a fire to burn out all the organic matter. If this is not done, an unpleasant odor may appear during the heating of the boiler.

Manufactured stainless steel containers are installed on the top plate and connected to the appropriate circuits. The work is finished, all that remains is to install the chamber doors in place and the boiler is ready for use.

A hydronic heating system is the most common way to create heat in a home. The main element of the system is a water heating boiler, which heats the coolant.

Kinds

You can make the following types of boilers with your own hands:

Electric boilers.

There are, but given the explosiveness of the gas, it is impossible to undertake the independent production of such units.

All types of boilers have two common features:

Availability of a tank for heating water. It may take the form of a cylindrical tank or be a system of interconnected tubes.
Availability of a heat source. In long-burning boilers, this is wood, pellets or any other type of solid fuel. In electrical devices for a private home, the coolant is heated due to the low electrical conductivity of the nichrome thread or water itself. Also, its heating can occur due to eddy currents that arise due to the operation of the induction coil.

The first element plays a key role, since the efficiency and efficiency of a homemade boiler depends on it. Its importance is felt most of all in long-burning solid fuel boilers, because it must absorb as much of the created heat as possible.

This ability of his depends on the area. The larger it is, the more heat it absorbs, and the more the carbon monoxide cools. In a properly made long-burning heating boiler, it cools to 120-150 °C.

Long burning boiler

This boiler has at least two modifications.

The design of the first modification of a long-burning boiler consists of the following elements:

An ash chamber with a door on which the ash pan is placed.
Combustion chamber with door.
Heat exchanger.
Connections for supply and return of coolant.
Openings for the release of carbon monoxide. Placed at the top of the combustion chamber.
Draft regulator (includes a temperature sensor in the form of a bimetallic plate or container filled with wax, as well as a chain mechanism that controls the blower).
Cases.
Thermal insulation.
Sheathing.
Nozhek.

Read also: Hot water boilers for a private home

In this long-burning boiler, the ash chamber has the same depth and width as the combustion chamber. It is located under the combustion chamber.

You can make two types of heat exchanger yourself:

Tubular.
Water jacket.

The first one is vertical pipes that are connected by horizontal pipes, or horizontal tubes, the ends of which are welded to two flat vertical sealed metal boxes. In this case, one end of each pipe is higher than the second. That is, there is a slight slope. In both options, the pipes are placed in a checkerboard pattern. Thanks to this, the smoke seems to get entangled between the heat exchanger tubes and gives off more heat.

Such a unit is placed in the firebox. It is placed at the top of the chamber. In this case, the movement of the coolant should be opposite to the movement of smoke. In a boiler with such a heat exchanger, an additional casing is always made. There should be a space of several centimeters between it and the combustion chamber. Thanks to this, the thermal insulation material, which is placed around the body, will not overheat.

As for the water jacket, this the heat exchanger consists of two containers placed one in the same. The inner one is the combustion chamber. Space is created between the containers. During operation of the boiler, it is filled with water, which absorbs heat from the hot walls of the combustion chamber.

The second modification of the boiler for heating a house has a similar structure:

Frame. It is a structure of two pipes that are inserted into each other. The space between them is filled with water.
Ash and loading doors.
Air distributor. A round plate with vertical plates welded at the bottom and a hole made in the center. This distributor supplies air to the firewood through a pipe that is welded to a hole made in it. There is a valve at the top of the tube.
Top with a hole in the center. An oxygen supply pipe passes through this hole (it is welded to the air distributor).
Chimney.

Pyrolysis boiler

This long-burning solid fuel boiler has a more complex design:

Gas generation chamber. It has a bottom made of fireclay bricks. There is a hole in the middle for the movement of gases.
Carbon monoxide combustion chamber.
Gas combustion chamber.
Chamber with tubular heat exchanger. It has a smoke hole.
Two doors. One is intended for loading fuel. The other is for removing ashes. It has dimensions that provide free access to the combustion and afterburning chambers of the gas.
Pipes that supply air inside different chambers. In this case, oxygen is supplied separately. Some channels supply air into the gasification chamber, others into the gap in the bottom of this chamber. The channels are located in the thickness of fireclay bricks. In this case, the incoming oxygen, under the influence of draft, moves along with the gases into the combustion chamber.
A mechanism with dampers that control the flow of air through various channels.
Smoke exhauster (located on the back side of the 4th chamber).
Air gate. There is a smoke exhauster above it.
Direct stroke gate. This element is located on the rear wall of the loading chamber. It is opened only when the fire is lit. At this time, the smoke exits directly into the rear chamber.
Tubular heat exchanger.

Features of manufacturing solid fuel boilers

The best material to use is heat-resistant steel with a thickness of 4-5 m. If such an alloy is too expensive, you can weld the boiler from ordinary sheet metal. Metal with a fire-resistant lining is suitable for a pyrolysis boiler. Other material will quickly degrade.
The diameter of the pipes that extend from the heat exchanger depends on coolant circulation type. If water is to move naturally, the diameter must be large. If you plan to use a pump, then you can take narrower pipes. A universal option is a pipe with a diameter of 32 mm or more.
It is worth choosing a loading door for a device with a tubular heat exchanger so that the heat exchanger can be removed through the hole.
Doors should be made double, with asbestos gasket.

Electric water heating boiler

The easiest way to make a heating element boiler at home. It has this design:

Storage tank in the form of a wide pipe with plugged ends.
A heating element located at the bottom (for a system with natural circulation) or at the top (for a system with a circulation pump).
Water supply and return pipes. The first is welded at the top of the tank, the other at the bottom.
Mineral wool (wrapped around the tank).
Overheat sensor. Located on the body or inside the boiler.
Circuit breaker.
Magnetic switch.
Control board with temperature sensor.

The boiler is made like this:

Cut the main pipe.
Weld circles cut out of sheet metal on both sides.
Drill a hole for the heating element in one of the circles.
Drill holes in the side walls for the pipes.
The pipes are welded.
Fix the heating element.
Install an overheating sensor on the housing. If a thermal relay is used, then a hole is made near the hole for the heating element. The thermostat is fixed in it.
The heating element is connected to the magnetic starter, and the starter is connected to the switch.
The temperature sensor is connected to the control board.
A cable is drawn from the board to the magnetic starter.
The entire structure is hidden in a casing made of galvanized or sheet steel.

“A boiler is really a stove in a barrel of water”... and the efficiency of such a unit will be at best 10%, or even 3-5%. After all, a solid fuel boiler is not a stove at all, and a solid fuel stove is not a hot water boiler. The fact is that the combustion process of solid fuel, unlike gas or flammable liquids, is certainly extended in space and time. Gas or oil can be completely burned immediately in a small gap from the nozzle to the burner diffuser, but wood and coal cannot. Therefore, the requirements for the design of a solid fuel heating boiler are different than for a heating furnace; it is impossible to simply put a heating circuit water heater into it in continuous circulation. Why this is so, and how a continuous heating boiler should be designed, is what this article is intended to explain.

Your own heating boiler in a private house or apartment becomes a necessity. Gas and liquid fuels are steadily becoming more expensive, and in return, inexpensive alternative fuels are appearing on sale, for example. from crop waste - straw, husks, husks. This is only from the point of view of the owners of the house, not to mention the fact that the transition to individual heating will allow you to get rid of energy losses in the main lines of thermal power plants and power line wires, and they are by no means small, up to 30%

You cannot make a gas boiler yourself, if only because no one will give permission to operate it. It is prohibited to use individual liquid fuel boilers for heating residential premises due to their high fire and explosion hazard when used in a decentralized manner. But you can make a solid fuel boiler with your own hands and register it officially, just like a heating stove. This is perhaps the only thing they fundamentally have in common.

Features of solid fuel

Solid fuel does not burn very quickly, and not all components carrying thermal energy burn in its visible flame. For complete combustion of flue gases, a high but well-defined temperature is required, otherwise conditions will arise for endothermic reactions to occur (for example, nitrogen oxidation), the products of which will carry away the energy of the fuel into the chimney.

Why doesn't the boiler bake?

The oven is a cyclic device. So much fuel is loaded into its firebox at once so that its energy lasts until the next fire. The excess combustion energy of the fuel load is partially used to maintain the optimal temperature for afterburning in the gas path of the furnace (its convective system), and is partially absorbed by the furnace body. As the load burns out, the ratio of these parts of fuel energy changes, and a powerful flow of heat circulates inside the furnace, several times more powerful than the current needs for heating.

The body of the stove is thus a heat accumulator: the main heating of the room occurs due to its cooling after heating. Therefore, it is impossible to take away the heat circulating in the furnace; this will somehow disrupt its internal thermal balance, and the efficiency will drop sharply. It is possible, and even then not in every place of the convection system, to take up to 5% to replenish the hot water storage tank. Also, the stove does not require operational adjustment of its thermal power; it is enough to load fuel based on the required average hourly time between firings.

A water boiler, no matter what fuel it uses, is a continuous operation device. The coolant circulates in the system all the time, otherwise it will not heat, and the boiler must at any given moment provide exactly as much heat as was lost outside due to heat loss. That is, fuel must either be periodically loaded into the boiler, or the thermal power must be quickly adjusted within a fairly wide range.

The second point is flue gases. They must approach the heat exchanger, firstly, as hot as possible in order to ensure high efficiency. Secondly, they must be completely burned out, otherwise the fuel energy will be deposited on the register as soot, which will also need to be cleaned.

Finally, if the stove heats around itself, then the boiler as a heat source and its consumers are separated. The boiler requires a separate room (boiler room or furnace): Due to the high concentration of heat in the boiler, its fire danger is much higher than that of the furnace.

Note: An individual boiler room in a residential building must have a volume of at least 8 cubic meters. m, ceiling at least 2.2 m high, opening window at least 0.7 sq. m, a constant (without valves) flow of fresh air, a smoke channel separate from other communications and a fire separation from the other rooms.

From this it follows, firstly, boiler furnace requirements:

It should ensure rapid and complete combustion of fuel without a complex convection system. This can only be achieved in a firebox made of materials with the lowest possible thermal conductivity, because For rapid combustion of gases, a high concentration of heat is required.
The firebox itself and the parts of the structure associated with it in heat should have the lowest possible heat capacity: all the heat that went into heating them will remain in the boiler room.

These requirements are initially contradictory: materials that conduct heat poorly, as a rule, accumulate it well. Therefore, a regular stove firebox will not work for a boiler; some kind of special one is needed.

Heat exchange register

The heat exchanger is the most important component of a heating boiler; it mainly determines its efficiency. Based on the design of the heat exchanger, the entire boiler is called. In household heating boilers, heat exchangers are used - water jackets and tubular, horizontal or vertical.

A boiler with a water jacket is the same “stove in a barrel”; a heat exchange register in the form of a tank surrounds the firebox. A jacketed boiler can be quite economical under one condition: if the combustion in the firebox is flameless. A flaming solid fuel furnace certainly requires afterburning of the exhaust gases, and in contact with the jacket their temperature immediately drops below the value required for this. The result is an efficiency of up to 15% and increased deposition of soot and even acid condensate.

Horizontal registers, generally speaking, are always inclined: their hot end (supply) must be raised above the cold end (return), otherwise the coolant will flow backwards, and failure of forced circulation will immediately lead to a serious accident. In vertical registers, the pipes are located vertically or slightly inclined to the side. In both cases, the pipes are arranged in rows in a checkerboard pattern, so that gases are better “entangled” in them.

Regarding the directions of movement of hot gases and coolant, pipe registers are divided into:

Flow-through - gases generally flow perpendicular to the coolant flow. Most often, this scheme is used in horizontal industrial boilers of high power due to their lower height, which reduces the cost of installation. In households, the situation is the opposite: in order for the register to properly capture the heat, it has to be made extended upward above the ceiling.
Countercurrent - gases and coolant move along the same line towards each other. This scheme provides the most efficient heat transfer and the highest efficiency.
Flow - gases and coolant move parallel in one direction. Rarely used in special-purpose boilers, because At the same time, efficiency is poor, and equipment wear is high.

Further, heat exchangers are made of fire tube and water tube. In fire tubes, smoke tubes carrying flue gases pass through a tank of water. Fire tube registers operate stably, and vertical ones provide good efficiency even in a flow diagram, because internal water circulation is established in the tank.

However, if we calculate the optimal temperature gradient for heat transfer from gas to water based on the ratio of their density and heat capacity, then it turns out to be approximately 250 degrees. And in order to push this heat flow through the wall of a steel pipe of 4 mm (you can’t do less, it will burn out very quickly) without noticeable losses on the thermal conductivity of the metal, you need about another 200 degrees. As a result, the inner surface of the smoke pipe should be heated to 500-600 degrees; 50-150 degrees – operational margin for fuel water cut, etc.

Because of this, the service life of the smoke tubes is limited, especially in large boilers. In addition, the efficiency of a fire tube boiler is low; it is determined by the ratio of the temperatures of hot gases entering the register and those exiting the chimney. It is impossible to allow gases to cool below 450-500 degrees in a fire tube boiler, and the temperature in a conventional firebox does not exceed 1100-1200 degrees. According to the Carnot formula, it turns out that the efficiency cannot be higher than 63%, and the efficiency of the firebox is no more than 80%, so the total is 50%, which is very bad.

In small domestic boilers, these features have a weaker effect, because when the size of the boiler decreases, the ratio of the register surface to the volume of flue gases in it increases, this is the so-called. square-cube law. In modern pyrolysis boilers, the temperature in the combustion chamber reaches 1600 degrees, the efficiency of their furnace is 100%, and the registers of branded boilers, guaranteed for 5 years or more, are made only of thin-walled heat-resistant special steel. In them, gases can be allowed to cool to 180-250 degrees, and the overall efficiency reaches 85-86%

Note: Cast iron is generally unsuitable for smoke pipes; it cracks.

In water-tube registers, the coolant flows through pipes placed in a fire chamber into which hot gases enter. Now temperature gradients and the square-cube law operate in the opposite way: at 1000 degrees in the chamber, the outer surface of the pipes will be heated to only 400 degrees, and the inner surface to the temperature of the coolant. As a result, pipes made of ordinary steel last a long time and the boiler efficiency is about 80%

But horizontal flow-through water tube boilers are prone to the so-called. "flooding". The water in the lower pipes turns out to be much hotter than in the upper ones. It is pushed into the supply first, the pressure drops, and the colder upper pipes “spit out” the water. “Buhtenie” not only provides as much noise, heat and comfort as a neighbor who is a drunkard and a brawler, but is also fraught with a break in the system due to water hammer.

Vertical water-tube boilers do not fire, but if a water-tube boiler is being designed for a house, the register should be located at the bottom of the chimney, in the section where hot gases flow from top to bottom. In an in-line water-tube boiler with the same direction of movement of gases and coolant, the efficiency drops sharply and soot is intensively deposited on the pipes near the supply, and it is generally unacceptable to make a return above the supply.

About the heat exchanger capacity

The ratio of the heat exchanger capacities and the entire cooling system is not taken arbitrarily. The rate of heat transfer from gases to water is not infinite; the water in the register must have time to absorb heat before it leaves the system. On the other hand, the heated outer surface of the register gives off heat to the air, and it is wasted in the boiler room.

A register that is too small is prone to boiling and requires precise, quick adjustment of the firebox power, which is unattainable in solid fuel boilers. A large-volume register takes a long time to warm up and, if the external thermal insulation of the boiler is poor or absent, it loses a lot of heat, and the air in the boiler room can warm up above the permissible level for fire safety and boiler specifications.

The size of the heat exchanger capacity of solid fuel boilers ranges from 5-25% of the system capacity. This must be taken into account when choosing a boiler. For example, for heating, according to the calculation, there were only 30 sections of radiators (batteries) of 15 liters each. With water in the pipes and an expansion tank, the total capacity of the system will be about 470 liters. The boiler register capacity should be between 23.5-117.5 liters.

Note: There is a rule - the greater the calorific value of solid fuel, the greater the relative capacity of the boiler register should be. Therefore, if the boiler is coal-fired, the register capacity should be taken closer to the upper value, and for a wood-burning boiler - to the lower value. For slow-burning boilers, this rule is not valid; the capacity of their registers is calculated based on the highest efficiency of the boiler.

What is the heat exchanger made of?

Cast iron as a material for a boiler register does not meet modern requirements:

The low thermal conductivity of cast iron leads to low boiler efficiency, because It is impossible to cool the exhaust gases below 450-500 degrees; as much heat as needed will not pass through the cast iron into the water.
The high heat capacity of cast iron is also its disadvantage: the boiler must quickly release heat into the system before it evaporates somewhere else.
Cast iron heat exchangers do not fit into modern weight and size requirements.

For example, let's take the M-140 section from an old Soviet cast-iron battery. Its surface area is 0.254 square meters. m. For heating 80 sq. m of living space, a heat exchange surface in the boiler of approximately 3 square meters is required. m, i.e. 12 sections. Have you seen a battery with 12 sections? Imagine what the cauldron must be like in which it will fit. And the load on the floor from it will definitely exceed the limit according to SNiP, and a separate foundation will have to be made for the boiler. In general, 1-2 cast iron sections will go to the heat exchanger that feeds the hot water storage tank, but for a heating boiler the question of a cast iron register can be considered closed.

The registers of modern factory boilers are made of heat-resistant and heat-resistant special steel, but their production requires production conditions. What remains is ordinary structural steel, but it corrodes very quickly at 400 degrees and above, so fire tube boilers made of steel must be selected for purchase or developed very carefully.

In addition, steel conducts heat well. On the one hand, this is not bad; you can expect to obtain good efficiency using simple means. On the other hand, the return flow should not be allowed to cool below 65 degrees, otherwise acidic condensate will fall onto the register in the boiler from the flue gases, which can eat through the pipes within an hour. You can exclude the possibility of its deposition in 2 ways:

For boiler power up to 12 kW, a bypass valve between the boiler flow and return is sufficient.
With greater power and/or heated area of more than 160 sq. We also need an elevator unit, and the boiler must operate in the mode of superheating water under pressure.

The bypass valve is controlled either electrically from a temperature sensor, or energy-independently: from a bimetallic plate with traction, from wax melting in a special container, etc. As soon as the temperature in the return drops below 70-75 degrees, it admits hot water from the supply into it.

The elevator unit, or simply the elevator (see figure), acts in the opposite way: the water in the boiler is heated to 110-120 degrees under pressure of up to 6 ati, which eliminates boiling. To do this, the combustion temperature of the fuel is increased, which increases efficiency and eliminates condensation. And before entering the system, hot water is diluted with return water.

In both cases, forced water circulation is necessary. However, it is quite possible to create a steel boiler using thermosiphon circulation that does not require power supply for the circulation pump. Some designs will be discussed below.

Circulation and boiler

Thermosiphon (gravity) circulation of water does not allow heating a room with an area of more than 50-60 square meters. m. The point is not only that it is difficult for water to squeeze through a developed system of pipes and radiators: if you open the drain valve when the expansion tank is full, water will rush out in a strong stream. The fact is that the energy for pushing water through the pipes is taken from the fuel, and the efficiency of converting heat into movement in a thermosiphon system is negligible. Therefore, the efficiency of the boiler as a whole decreases.

But the circulation pump requires electricity (50-200 W), which may be lost. A UPS (uninterruptible power supply) for 12-24 hours of autonomous operation is very expensive, so a properly designed boiler is designed for forced circulation, and if the power supply is lost, it must, without outside intervention, go into thermosiphon mode, when the heating is barely warm, but still warms.

How to install the boiler?

The requirement for a boiler’s minimum intrinsic heat capacity directly follows from its low weight compared to a stove and its weight load per unit floor area. As a rule, it does not exceed the minimum allowable according to SNiP for flooring of 250 kg/sq. m. Therefore, installing a boiler is permissible without a foundation and even dismantling the flooring, incl. and on the upper floors.

Place the boiler on a flat, stable surface. If the floor plays, it will still have to be dismantled at the boiler installation site down to the concrete screed with a distance of at least 150 mm to the sides. The base for the boiler is covered with asbestos or basalt cardboard 4-6 mm thick, and a sheet of roofing iron 1.5-2 mm thick is placed on it. Next, if the flooring has been dismantled, the bottom of the boiler is lined with cement-sand mortar to the floor level.

Around the boiler protruding above the floor, thermal insulation is made, the same as underneath: asbestos or basalt cardboard, and iron on it. The removal of insulation to the sides from the boiler is from 150 mm, and in front of the firebox door is at least 300 mm. If the boiler allows additional fuel loading before the previous portion burns out, then the removal in front of the firebox is required from 600 mm. Under the boiler, which is placed directly on the floor, only thermal insulation covered with a steel sheet is placed. Removal - as in the previous case.

A separate boiler room is required for a solid fuel boiler. The requirements for it are given above. In addition, almost all solid fuel boilers do not allow power adjustment within a wide range, so they require a full-fledged piping - a set of additional equipment that ensures efficient and trouble-free operation. We’ll talk about it later, but in general, piping the boiler is a separate big topic. Here we mention only the immutable rules:

Installation of the piping is carried out in counterflow to the water, from the return to the supply.
Upon completion of installation, its correctness and quality of connections are checked visually according to the diagram.
The installation of the heating system in the house begins only after piping the boiler.
Before loading fuel and, if required, supplying power, the entire system is filled with cold water and all joints are monitored for leaks during the day. In this case, water is water, and not some other coolant.
If there are no leaks, or after they have been eliminated, the boiler is started on water, continuously monitoring the temperature and pressure in the system.
Once the nominal temperature is reached, the pressure is controlled for 15 minutes; it should not change by more than 0.2 bar, this process is called pressure testing.
After pressure testing, the boiler is extinguished and the system is allowed to cool completely.
Drain the water and fill in the standard coolant.
Check the joints for leaks once again 24 hours. If everything is in order, the boiler is started. No - they fix the leaks, and again daily monitoring before starting.

Choosing a boiler

Now we know enough to choose a boiler based on the intended type of fuel and its purpose. Let's get started.

Wood burning

The calorific value of firewood is low, the best ones have less than 5000 kcal/kg. Firewood burns quite quickly, releasing a large volume of volatile components that require afterburning. Therefore, it is better not to count on high efficiency using wood, but they can be found almost everywhere.

Wood burning for the house

A home wood-burning boiler can only burn for a long time, otherwise it will damage it in all respects. Industrial structures, e.g. the well-known KVR, cost from 50,000 rubles, which is still cheaper than building a furnace, do not require power supply and allow power adjustment for heating in the off-season. As a rule, they operate on coal and any solid fuel, except sawdust, but with coal, fuel consumption will be much higher: heat transfer from one load is 60-72 hours, and for specialized coal ones – up to 20 days.

However, a long-burning wood-burning boiler can be useful in places where there is no regular supply of coal and qualified heating service. It costs one and a half times less than coal, its jacket design is very reliable and allows you to build a thermosiphon heating system with an area of up to 100 square meters. m.. In combination with the smoldering of the fuel in a thin layer and a fairly large volume of the jacket, boiling of water is excluded, so the piping is sufficiently the same as for titanium. Connecting a long-burning wood-burning boiler is also no more difficult than titanium, and can be done independently by an unqualified owner.

About brick boilers

Diagram of the boiler “Blago”

Brick is the friend of the stove and the enemy of the boiler due to the fact that it gives the structure greater thermal inertia and weight. Perhaps the only brick boiler in which the brick is in its place is Belyaev’s pyrolysis “Blago”, diagram in Fig. And then, its role here is completely different: the lining of the combustion chamber is made of fireclay bricks. Horizontal water tube heat exchanger; The problem of coiling is solved by the fact that the register pipes are single, flat, elongated in height.

Belyaev’s boiler is truly omnivorous, and there are 2 separate bunkers for loading different types of fuel without stopping the boiler. “Blago” can work on anthracite for several days, on sawdust – up to a day.

Unfortunately, Belyaev’s boiler is quite expensive, due to the fireclay lining it is poorly transportable and, like all pyrolysis boilers, requires complex and expensive piping. Its power is regulated within small limits by bypassing flue gases, so it will show good efficiency on average for the season only in places with prolonged severe frosts.

About boilers in the furnace

The boiler in the furnace, about which they talk and write so much now, is a water-tube heat exchanger immured in the furnace masonry, see fig. below. The idea is this: after firing, the stove should release heat more directly than into the surrounding air. Let's say right away: reports of an efficiency of 80-90% are not only doubtful, but simply fantastic. The best brick oven itself has an efficiency of no higher than 75%, and its outer surface area will be no less than 10-12 square meters. m. The surface area of the register is unlikely to be more than 5 square meters. m. In total, less than half of the heat accumulated by the furnace will go into the water, and the overall efficiency will be below 40%

Next point - a stove with a register immediately loses its properties. Under no circumstances should you heat it out of season with an empty register. The TCR (temperature coefficient of expansion) of metal is much greater than that of brick, and the heat exchanger, swollen from overheating, will tear the stove before our eyes. Thermal seams will not help the matter; the register is not a sheet or a beam, but a three-dimensional structure, and it is bursting in all directions at once.

There are other nuances here, but the general conclusion is clear: a stove is a stove, and a boiler is a boiler. And the fruit of their forced unnatural union will not be viable.

Boiler piping

Boilers that prevent boiling of water (long-burning jacket boilers, titanium boilers) cannot be made with a power of more than 15-20 kW and cannot be extended in height. Therefore, they always provide heating for their area in thermosiphon mode, although a circulation pump, of course, would not hurt. In addition to the expansion tank, their piping includes only an air drain valve at the highest point of the supply pipeline and a drain valve at the lowest point of the return line.

The wiring of solid fuel boilers of other types should provide a set of functions, which can be better understood in Fig. on right:

safety group: air drain valve, general pressure gauge and breakthrough valve for releasing steam during boiling;
emergency cooling storage tank;
its float valve is the same as in the toilet;
thermal valve for starting emergency cooling with its sensor;
MAG block - drain valve, emergency drain valve and pressure gauge, assembled in one housing and connected to a membrane expansion tank;
forced circulation unit with a check valve, a circulation pump and an electrically temperature-controlled three-way bypass valve;
intercooler - emergency cooling radiator.

Pos. 2-4 and 7 make up the power reset group. As already mentioned, solid fuel boilers are regulated in terms of power within small limits, and with sudden warming, the entire system may overheat unacceptably, even to the point of bursting. Then thermal valve 4 lets tap water into the intercooler, and it cools the supply to normal.

Note: The owner's money for fuel and water flows quietly and peacefully down the drain. Therefore, solid fuel boilers are not suitable for places with mild winters and long off-season periods.

The forced circulation group in normal mode bypasses part of the supply to the return line so that its temperature does not fall below 65 degrees, see above. When the power supply is turned off, the thermal valve closes. The heating radiators receive as much water as they can handle in thermosiphon mode, just so that the rooms can be lived in. But the intercooler thermal valve opens completely (it is kept closed under voltage), and excess heat again carries the owner’s money down the drain.

Note: If the water goes out along with the electricity, the boiler needs to be extinguished immediately. When water flows out of tank 2, the system will boil.

Boilers with built-in overheating protection are 10-12% more expensive than conventional ones, but this is more than compensated by simplifying the piping and increasing the reliability of the boiler: here excess superheated water is poured into an open large-capacity expansion tank, see figure, from where it cools and flows into return. The system, except for circulation pump 7, is energy-independent and switches to thermosiphon mode smoothly, but with sudden warming, the fuel is still wasted, and the expansion tank must be installed in the attic.

As for pyrolysis boilers, we provide a typical wiring diagram for your information only. All the same, its professional installation will cost only a fraction of the cost of the components. For reference: the heat accumulator alone for a 20 kW boiler costs about $5,000.

Note: Membrane expansion tanks, unlike open ones, are installed on the return line at its lowest point.

Chimneys for boilers

Chimneys of solid fuel boilers are calculated in general in the same way as stoves. General principle: a chimney that is too narrow will not provide the required draft. This is especially dangerous for the boiler, because it is heated continuously and fumes can occur at night. A chimney that is too wide leads to “whistle”: cold air descends through it into the firebox, cooling the stove or register.

The boiler chimney must meet the following requirements: the distance from the ridge of the roof and between different chimneys is at least 1.5 mm, the lift above the ridge is also at least 1.5 m. Safe access to the chimney must be provided on the roof at any time of the year. There must be a cleanout door at every chimney break outside the boiler room, and every pipe passage through the ceilings must be thermally insulated. The upper end of the pipe must be equipped with an aerodynamic cap; for a boiler chimney, it is required, unlike for a stove. Also, a condensate collector is required for the boiler chimney.

In general, calculating a chimney for a boiler is somewhat simpler than for a stove, because The boiler chimney is not so tortuous; the heat exchanger is considered simply a lattice barrier. Therefore, it is possible to build generalized graphs for different design cases, for example. for a chimney with a horizontal section (burrow) of 2 m and a condensate collector 1.5 m deep, see fig.

Using such graphs, after an accurate calculation using local data, you can estimate whether there was a gross error. If the calculated point is somewhere around its generalized curve, the calculation is correct. In extreme cases, you will have to extend or cut the pipe by 0.3-0.5 m.

Note: if, say, for a pipe 12 m high there is no curve for a power less than 9 kW, this does not mean that a 9 kW boiler cannot be operated with a shorter pipe. It’s just that for lower pipes a generalized calculation is no longer possible, and it is necessary to calculate exactly according to local data.

Video: example of construction of a shaft-type solid fuel boiler

conclusions

The depletion of energy resources and rising fuel prices have radically changed the approach to the design of household heating boilers. Now they, like industrial ones, are required to have high efficiency, low thermal inertia and the ability to quickly regulate power over a wide range.

In our time, heating boilers, according to the basic principles laid down in them, have finally diverged from stoves and were divided into groups for different climatic conditions. In particular, the considered Solid fuel boilers are suitable for areas with harsh climates and prolonged severe frosts. For places with a different climate, other types of heating devices will be preferable.

When designing a heating system for a private home, many owners, in order to reduce the cost of purchasing equipment, prefer homemade heating boilers to factory ones. Indeed, factory units are quite expensive, but they can be made if you have competent drawings and skills in handling tools for mechanical processing of materials, as well as a welding machine.

The operation scheme of water heating boilers is, as a rule, universal - the thermal energy that is released during fuel combustion is transferred to a heat exchanger, from where it goes to heating devices for heating the house. The design of the units can be very different, such as the fuel used and materials for manufacturing.

Long-burning pyrolysis boilers

The operation scheme of a long-burning pyrolysis device is based on the process of pyrolysis (dry distillation). During the smoldering process of firewood, wood gas is released, which burns at a very high temperature. In this case, a large amount of heat is released - it is used to heat the water heat exchanger, from where it is supplied through the main line to the heating devices to heat the house.

Solid fuel pyrolysis boilers are quite expensive, so many owners prefer to make a homemade heating boiler for their home.

The design of such a unit is quite simple. Solid fuel pyrolysis boilers consist of the following elements:

Firewood loading chamber.
Grate.
Combustion chamber for volatile gases.
A smoke exhauster is a means of providing forced draft.
Water type heat exchanger.

Firewood is placed in the loading chamber, set on fire and the damper is closed. In a sealed space, smoldering wood produces nitrogen, carbon and hydrogen. They enter a special compartment where they burn, releasing a large amount of heat. It is used to heat the water circuit, from where, together with the heated coolant, it is used to heat the house.

The fuel combustion time of such a water heating device is about 12 hours - this is quite convenient, since there is no need to visit it often to load a new portion of firewood. For this reason, solid fuel pyrolysis boilers are very highly valued among private sector home owners.

The drawing in the diagram clearly demonstrates all the design features of pyrolysis hot water boilers.

In order to make such a device yourself, you will need a grinder, a welding machine and the following consumables:

Sheet of metal 4 mm thick.
Metal pipe with a diameter of 300 mm and a wall thickness of 3 mm.
Metal pipes with a diameter of 60 mm.
Metal pipes with a diameter of 100 mm.

The step-by-step manufacturing algorithm is as follows:

We cut a section 1 m long from a pipe with a diameter of 300 mm.
Next, you need to attach a bottom made of sheet metal - to do this, you need to cut out a section of the required size and weld it with the pipe. The stands can be welded from channel bars.
Next we make a means for air intake. We cut out a circle with a diameter of 28 cm from sheet metal. In the middle we drill a hole measuring 20 mm.
We place the fan on one side - the blades should be 5 cm in width.
Next, we install a tube with a diameter of 60 mm and a length of more than 1 m. We attach a hatch on the top side so that it is possible to adjust the air flow.
A hole for fuel is required at the bottom of the boiler. Next, you need to weld and attach the hatch for a hermetically sealed closure.
We place the chimney on top. It is placed vertically at a distance of 40 cm, after which it is passed through a heat exchanger.

Solid fuel pyrolysis devices of the hot water type very effectively provide heating for a private home. Making them yourself helps save a very significant amount of money.

How to make a steam boiler with your own hands

The operation scheme of steam heating systems is based on the use of thermal energy of hot steam. When fuel burns, a certain amount of heat is generated, which enters the water heating section of the system. There, the water turns into steam, which flows under high pressure from the hot water section into the heating main.

Such devices can be single-circuit or double-circuit. A single-circuit device is used only for heating. Double-circuit also ensures the presence of hot water supply.

The steam heating system consists of the following elements:

Water heating steam device.
Stoyakov.
Highways.
Heating radiators.

The drawing in the figure clearly demonstrates all the nuances of the design of a steam boiler.

You can weld such a unit with your own hands if you have some skills in handling a welding machine and tools for mechanical processing of materials. The most important part of the system is the drum. We connect the water circuit pipes and instruments for control and measurement to it.

Water is pumped into the upper part of the unit using a pump. Pipes are directed downwards, through which water enters the collectors and the lifting pipeline. It passes through the fuel combustion zone and water is heated there. Essentially, the principle of communicating vessels is involved here.

First you need to think through the system well and study all its elements. Then you need to purchase all the necessary consumables and tools:

Stainless steel pipes with a diameter of 10-12 cm.
Stainless steel sheet 1 mm thick.
Pipes with a diameter of 10 mm and 30 mm.
Safety valve.
Asbestos.
Tools for machining.
Welding machine.
Instruments for control and measurement.

We make the body from a pipe 11 cm long with a wall thickness of 2.5 mm.
We make 12 smoke pipes 10 cm long.
We make a flame tube 11 cm.
We make partitions from stainless steel sheets. We make holes in them for the smoke tubes - we attach them to the base by welding.
We weld the safety valve and manifold to the body.
Thermal insulation is carried out using asbestos.
We equip the unit with monitoring and adjustment devices.

Conclusion

As practice shows, the manufacture of boilers for heating systems in private houses is quite common. If all thermal engineering calculations are carried out correctly, and if there is a well-drawn drawing and wiring diagram for the main line, such devices cope with their task quite effectively and allow you to save a significant amount of money, since such factory-made devices are quite expensive.

Making heating devices on your own is a scrupulous, complex and time-consuming task. In order to cope with it, you need to be able to use a welding machine and have skills in using tools for mechanical processing of materials. If you don’t have such skills, this will be a good opportunity to learn - and you will be able to provide your home with warmth and comfort with your own hands.