How to make water heating from a stove, build a heat exchanger boiler into the stove

Skirting radiators

This is a newfangled option when small radiators are installed around the perimeter of the apartment, at the level of the baseboard and disguised as worthless.

The main disadvantage will be this very plinth, it is wider and higher than ordinary plinths, and therefore there will be a small side around the perimeter of the room, which will not allow the bedside table or bed to be pushed completely against the wall. Agree, it’s very inconvenient when all the objects in the room stand 3-5 centimeters from the walls.

The advantage will be a more uniform heat distribution compared to radiator batteries. There will be no warm or cold corners in the rooms and it will be more pleasant to be in such a house.

Advantages and disadvantages of heating from a stove

Stoves with a water circuit are easy to make yourself, but you can purchase ready-made heating devices in the store. The models are characterized by the following advantages:

Furnaces with a water circuit do not need to be connected to electrical networks. They do not use gas as fuel. The devices run on coal, peat and wood, which are renewable fuels.
Stove water heating is completely autonomous, but it can be combined with other systems.
Adjustment is carried out using a manual valve.
The walls of the furnace are massive, they transfer heat, heating the air and surrounding objects. The room is heated evenly due to the use of coolant. It passes through the pipes, heating them and radiators.
Heating a private home will not require large expenses. Coal, peat and wood are available to everyone.
Stoves not only heat the room, they are used for cooking and heating water.
Devices, the front of which is covered with glass, allow you to contemplate an open flame. Fireplaces create a comfortable atmosphere in homes.
The design of the stove is massive; during the cold season it accumulates a large amount of thermal energy. The stove cools down gradually, so it heats the room for a long time after the fuel has burned out. In summer, the processes proceed in the opposite way. If the stove in a wooden house is built on a separate foundation, during the warm season it releases excess heat into the ground, working as an air conditioner.
The natural fuel on which the stove operates moderately pollutes the environment.
Water is used as a coolant. It has a volumetric heat capacity, which allows heat to be transferred over long distances. Water is affordable. It does not burn, is not toxic.

But furnaces with a water circuit also have disadvantages. They must be constantly monitored, firewood must be placed in time and the draft must be adjusted. The chimney should be cleaned and the ash removed.

A powerful brick oven is large in size, so it is placed on a solid foundation. It takes up the usable area of the room, which is why large structures are installed in spacious rooms. Such a furnace has low efficiency.

When installing a stove, you need to build a chimney. The draft must be strong, then the fuel burns intensely and the smoke is quickly removed outside. The pipe is isolated from the wooden elements of the roof and ceilings. Having installed a stove in the house, it is necessary to maintain a fuel supply and dispose of ash and slag in a timely manner. This adds more work to the owners of a private home.

The main disadvantage of water heating is that the water freezes quickly. Turning into ice, it expands, damaging devices. Combining with air, it promotes corrosion on the metal elements of the heating system. If the water is hard, scale will form inside radiators and pipes.

The principle of operation of a sauna stove with a water tank

Heating units have the following operating pattern: fuel (wood) is placed in the firebox and set on fire. During the combustion process, a sufficient amount of thermal energy is released. Warm air moves from bottom to top and heats the cobblestones in the heater. This way the stones heat up and maintain the desired temperature in the room.

The wood is ignited from below. Some models of sauna stoves need to constantly add fuel, otherwise the stones quickly cool down.

Other types of units have a longer combustion period. They can work for 7-20 hours without constantly adding firewood. This possibility is achieved due to the reverse direction of combustion - from top to bottom.

It is best to use peat briquettes, alder logs or coal as the main fuel. To warm up the room faster, use only dry firewood. There is no need to use logs made from coniferous trees; they will quickly pollute the chimney, releasing a large amount of soot.

Making a heat exchanger with your own hands

It is not always possible to buy a ready-made furnace project with a heat exchanger. Also, not everyone can weld themselves. But building a heat exchanger for a heating stove with your own hands is not such a difficult task. By using aluminum or copper you can avoid welding work. With good preparation and correct calculations, this is possible and not burdensome. In addition, it saves the family budget.

Consumables

Having chosen the location and size, it is worth considering what is easier to build a heat exchanger from. You can use both the materials listed above and cast iron radiators, car radiators, and the like. The main thing is to correctly take into account thermal conductivity. Think through exactly what tool you will need and prepare it in advance. All these little things will make installation easier.

Assembly algorithm

You need to start with the project - thinking through the little things and selecting options. It is worth starting from the size - if the stove is weak, then a disproportionately large heat exchanger will only do harm. If you use copper as a pipe for the coil, then the length should not exceed three meters.

The simplest manufacturing option is a coil. It will require a copper pipe from 2 m to 3 m long.

The heating rate depends on the length of the pipe and the number of turns. But it’s worth remembering that you need to take into account the size of the stove and firebox and not overuse the enlargement of the coil. Distortions in size reduce the service life of the furnace.

To twist the pipe into a spiral, you need a template. This is any cylindrical auxiliary part. The diameter of the template must fit into the combustion chamber size.

Having prepared the materials, let's start:

Bending the pipe, we wind it onto a prepared blank to obtain a spiral;
We observe the dimensions in which the coil must be placed;

The average design power of the heat exchanger is 1 kW per 10 meters of area.

If you are not satisfied with this type of heat exchanger, you can make another type, for example by welding steel pipes. It looks something like this:

Examples of drawings on which to carry out work:

How to install?

It is convenient to install a heat exchanger in a stove when laying a new stove. This will allow it to be completely installed, observing all the gaps and dimensions. With this installation it is easier to maintain the correct size. Having mounted the heat exchanger on the foundation of the furnace, it is easier to cover it with bricks than disassembling the finished furnace and trying to fit it into place. But this is also possible.

Functions

Most often, heat exchangers are used to create a second heating circuit. Without it, the fuel burns and heats the walls of the firebox. Interacting with air, heated bricks give off heat. But it flies away through the flue.
With the help of a heat exchanger in a brick kiln, hot air transfers excess heat to the circulating fluid. Allows you to increase efficiency by obtaining a double output coefficient per fuel unit.
Heat exchangers are used in stoves for baths, garages, and houses. In each listed option, the heat exchanger has its own function - heating water for a shower, heating the coolant for heating, and the like. Various designs increase the range of applications.

Design features

Most often, a metal tank with a capacity of up to 5 liters with built-in pipes acts as a heat exchanger. There is no direct contact with fire. The device allows you to heat cold water, which then flows into radiators or a removable tank of larger capacity located in the same or an adjacent room.

As a result, by heating the stove in one room, it will be possible to heat another. According to its design, the heat exchanger for a furnace can be external or internal.

External

This type is very similar to a tank filled with coolant. Inside the container there is a part of the pipe used to remove combustion products. In terms of its design, the external heat exchanger is more complex than the internal one, as it places increased demands on welding work.

However, its maintenance is much easier. If necessary, the tank can be dismantled to remove scale or eliminate leaks.

Interior

Mounted above the firebox directly inside the stove. It is easy to install, but if maintenance is necessary, certain difficulties may arise. Especially if the stove is made of brick.

To avoid this, at the time of design development it is worth taking care of the maintainability of the future heat exchanger.

Description of the heat exchanger

The construction market sells many electric thermal energy generators powered by different fuels. However, sometimes it is more practical to use traditional ovens. For example, in cases where the house is located in remote rural areas, where problems with the supply of electricity or gas are possible. It is also acceptable to place the stove in country houses. But in order for the stove to not only heat the house, but also provide you with hot water, the right option would be to install a heat exchanger.

The heat exchanger is a small metal tank, with a volume of 3 to 5 liters, with built-in pipes. The device heats the incoming cold water and sends it to the radiators and to a removable tank with a capacity of up to 100 liters, which is additionally connected to the heat exchanger. The operating system is designed in such a way that when the stove is heated, the adjacent room is also provided with hot water, and when the bathhouse is not in use, the water is automatically drained from the system. The tank does not come into direct contact with the fire, and it is installed in the gap between the stove firebox and the convector. The oven is lit when the system is assembled and filled with water.

There are mainly 2 types of heat exchangers: internal and external:

The internal heat exchanger is located directly inside the furnace. It is easy to install, but in a brick stove it is more difficult to get to. This is easier to do with a metal stove.
External - looks like a chimney module and is a pipe hidden inside a sealed container. This pipe removes heat from the stove. This design is easy to repair and maintain.

Any type of heat exchanger for a sauna stove must be filled with water, and in some cases with antifreeze. The liquid in them is supplied from a mounted tank. By circulating it in a natural way, the system operates. Sometimes an electric pump is used for circulation. However, experts recommend using the method of natural movement of water in the system, plus it is better if the total length of the pipes does not exceed 3 meters and the thickness is not less than 2.5 cm.

The heat exchanger area is determined based on the total area of the bathhouse. As a rule, for heating a standard room with an area of 2 sq.m. approximately 5 kW of electricity is consumed. In many ways, this indicator also depends on the strength of fuel combustion in the furnace, on the location of the boiler itself, and when the combustion process stops, the boiler’s power rapidly decreases. Calculation of the surface area of the heat exchanger for the furnace must be done with a margin in order to organize a system capable of maintaining the required temperature in the bath.

Making a homemade heat exchanger

To make a heat exchanger with your own hands. many nuances must be taken into account. Only after carefully considering all stages of work, the end result will be a device that can provide the optimal temperature in the house. The main advantage of a device made by yourself is that the price of such a product is much lower, because you will only have to spend money on purchasing materials.

To ensure the maximum level of heating at home, it is necessary to choose the right material for the heat exchanger. Each metal has its own level of thermal conductivity. For copper, this figure is 7 times higher than for steel, so 2 pipes of the same diameter can provide different levels of heating. Therefore, copper is the best option for such a device. The price of this material is quite reasonable.

As for determining the power of the heat exchanger, these calculations are quite difficult. This is due to the fact that too many factors influence this indicator. However, on average, one meter of coil with a diameter of 50-60 mm is capable of producing 1 kW of thermal power. This indicator can be used as a starting point when making calculations.

Design features when making it yourself can be very different.

You can weld a pipe in the form of a coil or a regular rectangle, but there is a list of rules that you should definitely pay attention to:

The diameter of the inner part of the pipe should not be less than 5 mm. Otherwise, the water may simply boil.
To prevent overheating of the metal, the wall thickness must be at least 3 mm.
There should be a gap between the walls of the firebox and the heat exchanger, the size of which is 10-15 mm. After all, metal tends to expand.

A water heat exchanger has these basic rules. Its manufacture (with proper welding skills) will not be difficult. The right approach to your home heating system will ensure comfortable living conditions.

Be sure to read these materials:

Chimney pipe in a bathhouse
Heat exchangers for hot water supply

Features of heat exchangers

Creating a heat exchanger is hardly possible without first studying the features and operating principle of this device. In general, a heat exchanger is a device for exchanging thermal energy between two media that do not have their own energy source. A stove, for example, is not a heat exchanger, while a stove bench, which passes smoky gas through itself and heats the air in the room with its help, is such.

Diagram of a pipe-in-pipe heat exchanger

Another, more primitive type of heat exchanger can be considered the process of cooling a bottle under the pressure of cold tap water. In this case, the water heats up and the liquid inside the bottle cools.

Things to remember

With natural circulation of the coolant, the heat exchanger should be placed above the furnace at a distance of 1.5 - 2.5 m. Due to the constant change in geometric parameters, the pipes cannot be fastened to the wall tightly enough. It is necessary to provide a small gap.

It is important to remember that if the stove is used not only to heat the house, but also to heat water, a maximum of 10% of the total amount of heat generated should go to the heat exchanger. When using a structure with an expansion tank for heating, the volume of the latter should be selected so that the water in it can heat up to the required temperature in two hours

The return pipes should have a smaller diameter than the coolant supply pipes. The material intended for sealing threaded connections is selected with a sufficient level of heat resistance.

If the house is not intended for permanent residence, but is used only from time to time, then it is better to refuse water heating. It is advisable to fill in special antifreeze instead of water if you plan to heat a stove with a heat exchanger in the cold season. This will prevent pipes from bursting. Remember that adding coolant when the furnace is fully heated is unacceptable.

Heat exchanger and fireplace stove

This option is suitable for those who plan to heat several rooms, but at the same time love live fire.

Heat exchanger and fireplace stove

Design

The main element of such a system is a fireplace stove, from which numerous pipes filled with coolant (often water) run in all directions.

Important! In winter, it is recommended to add a little antifreeze to the water!

The liquid can circulate either naturally or forcibly using special pumps. In other words, the furnace heats the coolant, and pumps distribute it throughout the heated area.

Furnace with heat exchanger

Installing a heat exchanger can significantly increase the efficiency of the heat generator, and instead of one room, as in previous options, you can heat two at once without any special costs.

Main types

The modern market offers a wide variety of fireplace stoves, and all of them can be equipped with a heat exchanger if necessary to heat a large area. At the same time, some pay attention to the type of fuel used, others to the power. Below are the most popular options.

The pellet device, as the name suggests, is distinguished by the fact that instead of wood it is fueled with pellets - environmentally friendly fuel, which is produced by pressing waste from the wood processing industry and supplied in the form of granules.

Pellets

The main reason for the popularity of this type of fuel is its low cost. Moreover, when burning it practically does not emit soot, so it is generally accepted that it is the future.

Cooking ovens are no less popular, and the reason for this is their multifunctionality. With their help you can not only heat the room, but also cook food. Original, practical and, probably, even romantic (meaning cooking over the fireplace).

Instructions for building a stove heating system with a water circuit

A hole is being dug.
A “cushion” is laid, consisting of broken bricks, crushed stone and medium-sized rubble. The width of this layer is approximately 20 cm. Natural materials are compacted and filled with cement mortar.
Bricks are being laid. It is laid in two rows on cement, and covered on top with a waterproofing layer of roofing felt, parchment and roofing felt.
A brick foundation is being built with clay mortar.

The first continuous row is laid. In the second row, an ash chamber begins to form, for which a special door is installed. The third row repeats the previous one.
The fourth row is formed. It serves as the basis for the fuel chamber made of refractory bricks; grooves are provided on it for installing the grate.
A U-shaped boiler made of steel is installed. Two pipes are welded to it - one at the top for supply, the other at the bottom for return. It also has a rectangular hole through which heated gases will escape.
The fifth row is laid. It is necessary to provide channels behind the side and rear walls of the boiler. Two small doors are installed on them to remove soot.
A sixth row is formed, in which a hole is provided between the gaps made in the previous row. This is a suction channel to increase draft in a heating furnace. The door for the fuel chamber is also installed here.
The wall is being laid out. It should be taken into account that fire-resistant bricks are laid around the door leading into the combustion chamber and above the fuel boiler.
Cast iron stoves are being installed on which food can be cooked. A metal corner is attached to the entrance of the heating and cooking chamber.
Chambers are formed, a channel is made on the back surface, and doors are installed.
The facade of the cooking chamber in the 16th row is covered with a metal strip. And then it itself is covered by laying bricks on specially laid metal strips.
A steam exhaust valve is installed to ventilate the furnace and an upper flue is formed.
35 rows are laid, on which the construction of the chimney begins.

Some people want to use a ready-made stove or fireplace, combining it with a water circuit. In this case, you will have to disassemble them almost to the ground in order to install the register.

Mayevsky crane

Water circuit installation process

For efficient operation of equipment for a heating water system, it is necessary to install a so-called register, which is a boiler or heat exchanger. It is also often called serpentine. Such a register is placed in the stove firebox.

A water stove heating scheme for a private house consists of the following elements:

combustion chamber;
ash pan;
sealed oven door;
hatch for cleaning the oven;
special surface for heating the oven;
injector;
gate;
cutter;
convection pipes;
grate

When making a container yourself, it is important to take into account that only welding is used to connect parts. When connecting heating pipes, you need to use special connection elements in the form of fittings, couplings, etc.

Using this type of design for your home will make it possible to save money on a boiler, for which the manufacturing materials will cost much less than if you buy a ready-made one. The best option is to use a regular metal pipe for water heating, in which holes are simply made for the outlets and inlets of the pipeline.

What are heat exchangers made of?

Finned pipes

There are a great many designs of this device today. Every craftsman involved in the manufacture of a heat exchanger tried to contribute something of his own, to somehow improve it. Therefore, it is impossible to consider all options. Meanwhile, the most popular components are listed below:

collectors;
radiators from cars;
registers;
heating radiators;
metal containers;
coils.

Is it possible to install a heating register in an existing furnace?

It would be more correct, of course, to build the furnace around the manufactured register. But, if the stove is already standing, you can still build a water circuit into it. True, you will have to try hard - they are of considerable size and must somehow hold on. So the task is not an easy one. In addition, do not forget that you will have to make two more conclusions - to connect the supply and return pipelines.

The best option is to make a water jacket under the shape of the stove (this one is for a metal stove with burners)

Finding a place to locate the register is also not very easy. Its direct contact with fire is very undesirable, but it should be in an environment of hot gases. In this case, you can hope that the heat exchanger will last a long time.

Material of manufacture

Copper. Due to its ductility, copper is most optimal for the manufacture of a heat exchanger. A copper tube is easy to bend and give any shape. It has a high thermal conductivity coefficient of more than 380. But copper is also not a heat-resistant material and is expensive.
Stainless steel. Also quite flexible and responsive material. Although it has a lower thermal conductivity coefficient. But it is resistant to temperature changes. Any configuration can be welded from it. IMPORTANT: Galvanized steel cannot be used; when heated, it releases toxic zinc compounds into the air.
Metal-plastic. Easily accessible practical material. Easily found, but it has a low thermal conductivity! Almost two orders of magnitude lower than that of copper. But this material is durable and resistant to temperature changes.

Advantages and disadvantages

Designs with a built-in heat exchanger have many advantages:

The system is energy efficient and economical. Brickwork will not require serious financial investments, the costs for pipes and radiators will be in any case, and the heat exchanger is an order of magnitude cheaper than ready-made boilers. When operating a stove, the cost of heating the house will be several thousand rubles for the purchase of firewood for the winter period.
The design of a brick stove hides unsightly elements; if desired, a fireplace or decor can be added to the system.
Heating of the room does not depend on the location of the structure; radiators can be installed anywhere
A brick stove takes a long time to cool down; the water circuit will remain hot for several hours after the wood burns out.

Some publications list the advantages of the water circuit system as the possibility of installing it in a ready-made furnace, which is possible in principle, but in practice this option is associated with a large number of problems that have to be solved.

Disassembling and subsequent reassembly of the stove is the most necessary thing that will have to be done. The cost of correcting an incorrectly installed register is comparable to the cost of a new stove, so contact professionals for such work.

The disadvantage of this design is a continuation of its advantages; in order to make a stove with heat exchangers yourself, experience is required, both in laying bricks and in installing heating systems. If experience comes with age and the amount of material studied, then when building a furnace with a water circuit, its disadvantages should be taken into account:

The fireplace is a fire hazard; it is necessary to take measures to prevent fire from reaching flammable objects; The stove takes up a significant area of the house, design the rooms in advance, include a large heating system in the design of the room; The temperature near the stove will always be higher than in the rest of the room; The heating process of the oven cannot be stopped instantly. If you are using a closed loop system with a circulation pump, turning off the electricity (even briefly for a few minutes) and stopping the pump will cause the water in the heat exchanger to boil. To avoid this, provide a combined system for water movement in the circuit. If the heating system is not used regularly, the water must be drained, which leads to premature wear of the entire structure. Otherwise, the water will freeze, which will lead to the destruction of the entire complex of devices. You cannot light the stove without water in the circuit.

This will lead to the destruction of the register and the reconstruction of the stove in order to use the stove in the summer without “turning on” the battery using the original design of the installation of heat exchangers. There is a risk of carbon monoxide poisoning, as with all solid fuel heating products, special attention must be paid to the correct manufacture of the chimney.

Making a heating system in your home based on a stove with a heat exchanger and batteries is an economically viable solution, but the design and construction must be approached competently, taking into account all the nuances of the work.

Operating principle of the heat exchanger

After lighting the stove, the water in the heat exchanger will heat up. As the temperature rises, the liquid slowly moves up the pipe. From the lower pipe, cold water enters the heat exchanger, heats up and moves back to the tank.

It is strictly forbidden to start the device “dry”, otherwise it will lose its sealant and begin to leak. You should also avoid using plastic pipes in the steam room, as when heated they emit toxic fumes.

A separate type of heat exchanger for a stove is applicable for a bathhouse as a chimney element. Heat consumption from fuel combustion in such devices occurs more efficiently. The main thermal energy that goes into heating the steam room is absorbed by the heat exchanger built into the stove from the furnace firebox. But a samovar-type device (that is, on a pipe) uses the heat of the chimney pipe to heat water. As a result, its efficiency is high.

To understand how the device works, imagine a hot water bottle immersed in cold water. The bottle cools, but the water, on the contrary, heats up. The heat exchanger works on the same principle.

In simple words, it is a coiled piece of pipe laid in a barrel with two outlets that heats or cools the liquid. An annealed copper pipe is suitable as a pipe. It simply bends and a threaded fitting is easily attached to it.

You can make a heat exchanger for a stove with your own hands according to the principle of a water jacket, when heat is exchanged between containers nested inside each other. But this type of device is very difficult to produce for a non-specialist in this matter.

An old heated towel rail or radiator (possibly even a car radiator), coil, register, manifold or metal tank can also be used as parts for the heat exchanger. Used gas water heaters are also suitable for this. The choice of materials for the manufacture of the device depends on the responsibilities assigned to it in the future.

The most durable material for a heat exchanger is food-grade stainless steel. It can withstand high temperatures, while its characteristics remain the same. Zinc, for example, evaporates at 200°C, and at higher temperatures it becomes hazardous to health due to its fumes. Therefore, heat exchangers with galvanized profiles should be under your supervision.

The design of heat exchangers involves their manufacture from both sheet steel and pipes. The latter, in turn, have a larger heating area. A heat exchanger made of pipes is most often used in stoves; they are placed under the hob. And in heating stoves it is advisable to install devices made of sheet steel with a thickness of 3 to 5 mm. Their length is individual and depends on the dimensions of the fuel compartment of the stove.

What are the benefits of heat exchangers:

Thanks to the use of a heat exchanger, the hot water tank can be installed further away from the stove.
The device provides rapid heating of the liquid and the entire system.
The heat exchanger can be used not only for working in a sauna stove, but also in other heating and heating equipment.
It is easy to install and dismantle the device.
Provided that the welds of the heat exchanger are strong and sealed, it can operate for a long time and reliably.
The heat exchanger produces steam, heats water and air in two or three rooms.
Easy maintenance of the device.
High efficiency.
Can be installed in any bathhouse.
Compact dimensions allow you to significantly save space.
High power of the device and its fast heating.
Deformations during heating are excluded.

Flaws

Despite many advantages, the installation of a heating element on a chimney pipe also has disadvantages. One of them, the most important, is a sharp decrease in the smoke temperature at the installation site of the heat exchanger. This can lead to deterioration of traction and the formation of condensation, increased soot deposition inside the pipe.

In addition, when connecting a heating system, for example, a garage, you need to calculate the volume of coolant to avoid boiling water and bursting pipes. Welds must be completely sealed.

Any heat exchanger design significantly increases the efficiency of the furnace. For trouble-free operation of the system, it is necessary to carry out a visual inspection of all its elements at least twice a year, and, if necessary, timely repairs, descaling, replacement of gaskets and other necessary maintenance work. In this case, water heating and heating systems will operate flawlessly for a long time.

Video: how to build a stove with a heating circuit yourself

Due to the fact that today gas lines are not installed everywhere, stove heating remains relevant and indispensable. Stocking up on fuel in advance and keeping the fire burning in the stove is all that is required of the owner of a stove-heated home. Therefore, in some houses, even with gas heating, they are in no hurry to get rid of reliable brick buildings, and also install cast iron fireplace stoves to create not only a warm, but also a cozy atmosphere in the house.

There are two main ways to prepare hot water. First, the water is heated while moving through the heater and supplied to the water tap. Such a heater is called a flow-through heater.

The second method is to heat a large volume of water in a thermally insulated container, then gradually consume it. Such a heater is called a storage heater. The energy source is usually gas, electricity or heated coolant from the heating system.

Flow-through – high peak power

The instantaneous heater must be relatively powerful in order to provide the required flow of hot water to the tap. For a shower head, a power of at least 10 kW is required, for filling a bath - from 15 kW, for two hot water taps - from 20 kW.

Heating water with an electric instantaneous heater is not cheap. In addition, you need a three-phase connection (over 6 kW) and a special permit for higher power.

It is optimal to provide several taps by installing a compact electric flow-through heater on each of them. At the same time, protection is installed against their simultaneous operation, so as not to overload the network.

A cheaper option is heating water using gas. A gas water heater or a second circuit of the heating boiler is used. The power of such devices can be enough for two taps, and hot water is cheaper.

Disadvantages of flow-through

With a flow-through circuit, the heater should be located as close to the tap as possible in order to drain less water until it gets hot. The recommended distance is no more than 5 meters. But in any case there will be excessive consumption of water and energy. A similar drawback is typical for a storage heater.

Another disadvantage of a flow-through DHW (hot water supply) circuit is the inability to pick up some hot water. Each device has its own minimum power. Therefore, when water flow is low, it simply does not turn on. This also results in waste of water and energy.

Pressure surges in the system cause discomfort because they change the outlet water temperature.

In retail outlets, in order to sell an unsuitable flow-through electric heater, they simply indicate that it produces so many liters of water at a temperature, for example, +50 degrees, which at first glance is acceptable. But it is not indicated at what temperature the water is heated. The key characteristic of such a device is the temperature difference. After all, cold water is usually +6 - +10 degrees, and not +15 or +20.

Storage water heating system

The main advantage of an electric storage tank with a power of 1.5-2.0 kW is that it can be installed anywhere, in any house or apartment where there is a 220 V power supply. Its volume is usually 25 - 150 liters (running volume 50 - 100 liters) . The water in it is heated gradually to a predetermined temperature, and when withdrawn, a large flow rate is possible; the temperature decreases gradually.

How to make a homemade heat exchanger

Multi-pipe register

The shape of a heat exchanger for heating made by yourself can be different. The most common option is a register made of several steel or copper pipes, but plate-type examples are also used.

The temperature in the combustion zone is very high, especially when burning coal. Therefore, increased demands are placed on the metal from which the heat exchanger elements will be made, the rationality of its design and the quality of the welds.

Materials for production

An example of using cast iron radiators as a heat exchanger in a brick oven

The task of water heat exchangers for heating is to ensure optimal heat transfer, and in this process the degree of thermal conductivity of the metal is important. For example, a steel pipe conducts heat 7 times less than a copper pipe. Therefore, with the same pipe diameter, to transfer the same amount of heat, you will need 25 meters of steel pipe instead of 3.5 meters of copper.

Copper heat exchangers are the most economical to operate, but also expensive. Heat exchangers made of steel pipes with a diameter of at least 32 mm are considered more affordable for self-production.

If you plan to heat the stove with coal, it is better to install a heat exchanger made of cast iron. This metal is stronger, and the walls of the device will not burn out for a long time.

Heat exchanger power calculation

It is quite difficult to calculate in advance the power of the heat exchanger for a heating system. To do this, you need to take into account too many factors: pipe diameter, coil length, thermal conductivity of the metal, fuel combustion temperature, coolant circulation rate, etc. The real ability of the heat exchanger to cope with its functions will become clear only after the heating system starts operating.

When calculating, you can estimate that 1 meter of pipe with a diameter of 50 mm, serving as a heat exchanger, will provide 1 kW of thermal power.

You can take as an example any well-known boiler model and, in accordance with its parameters, make your own homemade heat exchanger.

Design Features

A heat exchanger for water heating of a house, welded from smooth-walled pipes, is called a register. It looks like a kind of “grid” and is the most popular form of homemade heat exchanger. In addition to this design, simpler devices are also made in the form of a rectangular or cylindrical tank. The main thing is that the surface area for heat exchange is as large as possible.

When making a heat exchanger with your own hands, several conditions must be observed:

the width of the internal voids in the heat exchanger must be at least 5 mm, otherwise the water in it may boil;
the thickness of the pipe walls must be at least 3 mm so that the metal does not burn through;
a gap of 10–15 mm between the heat exchanger and the walls of the firebox should compensate for the expansion of the metal when heated.

Installation features

The heat exchanger is installed inside the furnace during its laying

The easiest way is to install the heat exchanger simultaneously with the construction of the furnace. If you install it in an old stove, you will have to dismantle part of its brickwork.

A tubular heat exchanger is installed on the prepared furnace foundation directly into the furnace cavity.
When further laying rows of bricks, space is left for the inlet and outlet pipes of the device.
After completing the laying of the stove, connect the heat exchanger to the heating system, fill the system with water and test fire the stove.

The video material offers useful tips for making a heat exchanger yourself:

So far we have only talked about heat exchangers in a water heating system

Let's pay attention to other areas of their application.

Metal sauna stove with water tank

They can be made from different materials. Cast iron stoves for wood-fired saunas equipped with a water tank are not recommended for use, since the metal cannot withstand sudden temperature changes and is destroyed.

A do-it-yourself sauna stove made of metal does not require a massive foundation. To protect the floor surface, you need to lay a metal sheet. It will prevent possible fire due to fallen coal. An asbestos cement sheet is added on top of it.

A detailed design of an iron furnace with a water heat exchanger is being developed. All structural elements must be taken into account: heater, valve, firebox, ash door. Additional fittings may be required, which are made of steel for a good connection using a welding machine.

A cast iron (metal) sauna stove is usually equipped with an iron pipe. In this case, the valve is located at the top of the furnace, since it is convenient rather than reaching up to the pipe.

What to make it from? You can use any iron sheets or devices (cylinders, car rims, barrels), but it is better to use special 20K steel (boilers are made from it). Steel 20X13 can also be used to create heat exchangers or fireboxes for sauna stoves. The second option is more expensive. The thickness of the sheets is taken to be more than 5 mm.

Options from manufacturers can be equipped with a built-in tank or have remote tanks. The main material is high-quality cast iron, which lasts a long time and does not fade. Heating water in a bathhouse using a metal heater is almost no different: the brick version takes longer to heat up, but retains heat for a long time, the steel version warms up quickly and cools down quickly.

The features of the device must be reflected in the completed project. Welding work is carried out in accordance with the drawings and recommendations.

Design features

By easily changing the size of the combustion chamber, the power of the furnace can be adjusted.

The remaining important compartments are no different from the brick version. At the very bottom there is a firebox, which has a blower hole. Above is a heater for placing cobblestones. Then a valve is installed that allows you to regulate the heating power of the water tank.

The heater is made to the maximum size that fits on a homemade device. To increase maximum heat transfer, a special casing is added to the design. This is a unique alternative to the smoke circulation of stone stoves.

The advantage of a metal heater is the ability to attach a water tank to a sauna pipe. It is easy to build if you have welding skills.

In most cases, a do-it-yourself sauna tank is made of various types, depending on the selected equipment configuration (mounted, internal, etc.). The material is high-quality metal sheets or stainless steel.

Stove with a water circuit for heating a house: advantages

As already mentioned, a conventional stove is not able to provide uniform heating of all rooms in the house. In modern stoves and fireplaces, this problem is partially solved by installing a convection chamber to which an air duct system is connected. As a result, the flow of warm air from the stove is not left to its own devices, but moves in the limited space of the pipes and is regulated by valves, dampers, grilles and other additional devices.

However, air ducts are bulky, eat up useful space, and as their length and number of turns increases, heat loss increases. They need monitoring and maintenance: periodic cleaning of dust, soot and soot. The air itself has a low specific heat capacity; in order to transfer heat to a room remote from the furnace, forced injection of heated air masses by a fan is required. Therefore, water, as a coolant, is in many respects preferable to air.

Combined cottage heating system using a fireplace stove with a water circuit and solar collectors

Fact! The specific heat capacity of water is almost 4 times higher than the specific heat capacity of air. It is enough to compare 4.187 kJ/(kg×K) and 1.055 kJ/(kg×K).

Hot water is easy to transport through small-diameter pipelines, while transferring thermal energy over considerable distances. In addition, water is a harmless, non-flammable, non-toxic, chemically neutral and always available substance.

Advantages and disadvantages of stove heating

Traditional heating through a stove has both its advantages and disadvantages. Traditional stoves can be found even in the most modern homes. Stove heating systems can be used in private houses or cottages, in country houses or in the country. Among the advantages of such a heating system are the following:

Simple and quick installation. A traditional stove can be built from inexpensive and readily available materials.
Easy to operate and maintain.
This heating system has a high efficiency rate. If the heating system is designed as correctly as possible, then this figure can reach 60%. The value of this efficiency is almost similar to the efficiency of a device that runs on liquid fuel.
Modern stove heating can be combined with an appliance such as a fireplace. Thus, we will get not just a heating structure, but also a decorative element.
By using stove heating you can create a cozy and comfortable atmosphere in your home.
Thanks to furnace components such as dampers, you can regulate the temperature in your home.

The stove is an important element in the interior of the house.
The wood heating system also has its disadvantages. It would be wrong to hide such shortcomings, since they need to be taken into account when organizing stove heating:

A significant part of the usable area is lost. A more efficient stove will be larger, which means there will be less free space in the room.
It takes some time for the oven to heat up to the required temperature. The moment the stove is ignited does not mean that it is already starting to distribute heat into the room.
The stove quickly pollutes the room in which it is located. This means that it will need to be cleaned periodically.
Stove heating is not able to heat the house evenly. The temperature near the furnace will always be higher than in other parts of the building.
If such a system is operated incorrectly, there is a risk of carbon monoxide poisoning.
The risk of fire is higher.

Lighting up the stove is a lengthy process

Kinds

Types of heat exchangers are divided by design, location and material of manufacture. For each specific case, you can select a combination of these types.

By combining the design and material, and placing it correctly, you can significantly increase the efficiency of a brick kiln. It’s worth considering how to make a heat exchanger for a furnace without extra costs. By analyzing the types of existing structures, you can select the most optimal heat exchanger for a particular layout.

Coil. It is created from a pipe, coiled in the form of a spiral, several meters long. Such a water heat exchanger for a furnace is installed in a container with a liquid coolant. The ends of the pipe are expanded into the walls, allowing the coolant to circulate inside, simultaneously heating the water in the tank. With the correctly calculated length of the coil, the material it is made of, and the number of rings, you can speed up the heating of the water. Also, the part of the coil that remains in the air increases the rate of heating of the room.
Heat exchanger with container. The tank and heat exchanger pipe for the furnace are installed directly next to the combustion chamber. It is necessary to strictly observe the degree of inclination of the supplied pipes in order to achieve natural circulation. In some cases, it is necessary to install an electric pump for these purposes. This solution has its advantages - the water is heated directly by passing through a pipe that goes around the firebox. This solution increases the heating rate. Typically used for heating circuits.
Pipe board. It consists of two completely sealed containers and a large number of small pipes. The main pipe-containers are located in different parts, near the combustion space and are connected by pipes. Heat exchange occurs at the joints. This design is used for heating large spaces, up to high-rise buildings. The operation of such a heat exchanger is complicated because precautions must be taken. The chemical composition of the water is important here; due to the formation of scale, wall breakthroughs are possible.
Water jacket. This heat exchanger is the most difficult to create with your own hands. Its design consists of two sealed tanks located one inside the other. Efficient and easy to use - a heat exchanger for a stove made from a pipe. It allows heat exchange to occur quickly, but is difficult to manufacture and requires professional skills.

Choosing the design of the device

When choosing a suitable heat exchanger for a furnace, you should strive to ensure that the total surface area of the finished product is as large as possible. This will ensure the most efficient heating of the room.

The most widespread are registers (coils). Such heat exchangers are made from smooth-walled pipes with a diameter of 40 - 50 mm. Outwardly, they resemble a characteristic L-shaped grille. For their manufacture, you can use not only round, but also profile pipes with a similar cross-sectional area.

The return and hot water outlet can be located either on one side of the register or on different sides.

The output option is determined by the design features of the furnace itself and the piping layout of the heating system.

The next most popular are rectangular or cylindrical tanks, inside of which there is a pipe or coil. The length of such a heat exchanger depends on the parameters of the furnace firebox. The heat exchanger installed on the chimney usually has a cylindrical shape. There is a pipe running inside it, the diameter of which is equal to the diameter of the chimney. The pipes are welded from below. Can be used both for heating a room and for heating water.

This design requires special attention. Due to the rapid cooling of combustion products, the draft in the chimney itself is significantly reduced. This helps slow down fuel combustion.

Installing the product on a heating and cooking stove requires special attention. Care must be taken to ensure that hot gases pass over the top shelf and enter the chimney at the front of the firebox.

In this case, the cooking plate can be located directly above the heat exchanger. It is also possible to manufacture a register without a top shelf. The so-called shelf consists of lower and side parts connected to each other by pipes.

Heat exchanger for stove made of cast iron radiator

You can also make a heat exchanger for a furnace or boiler with your own hands from sections of cast iron radiators, even used ones. If sections of an old radiator are used for this, then before assembling they must be washed from the inside with a weak solution of hydrochloric acid (6-7%) and then with clean warm water to clean their inner surface of all deposits. In addition, it is necessary, using a special key, to disassemble the radiator into sections (even a new one) and replace the rubber or cardboard gaskets between them with asbestos threads impregnated with graphite lubricant. After this, having calculated the required number of sections for the heat exchanger (each area is about 0.25 m2), they are connected into one structure.

Such a register may consist of one or two rows of sections. The connection of heating system pipes to such a structure is carried out using threaded connections and corresponding adapters, angles and bends, just as when installing cast iron radiators, but to seal threaded connections that will be exposed to high temperatures, it is also necessary to use asbestos threads, and I’m not packing as usual.

After manufacturing such a heat exchanger, even before installing it in the furnace, it is necessary to check its tightness, and for this it is necessary to pour water into it and make sure that there are no leaks. Such a heat exchanger will have rather large dimensions, so it is better to install it not in the firebox, but in the chimney or stove hood. Moreover, cast iron does not tolerate sudden temperature changes and when exposed to flame on one side and cold water on the other, it can crack.

Video on the topic: