How to choose a double-circuit gas boiler for your home?

Autonomous gas heating will only be effective and economical when all the technical nuances and everyday needs of the inhabitants of the house are taken into account during its design and installation. A gas boiler is a key element of an autonomous heating system, so even at the project stage you should decide on the type and type of gas heating equipment. Finding out which boiler is better in each specific case, floor-mounted or wall-mounted, single-pipe or two-pipe, is a complex task and deserves a separate article. Let's try to figure out the situation, how to choose a double-circuit gas boiler for your home if you decide to choose units of this particular type.

In this case, you will have to choose according to many criteria. Each aspect has a specific meaning and plays a corresponding role in the operation of the home heating system. The level of comfort at home ultimately depends on your choice.

What determines your choice?

If you are the owner of a city apartment or the owner of a small private house, your choice in favor of double-circuit boilers is quite reasonable and obvious. The main aspect that most often determines such a decision is the desire of homeowners to receive several engineering and technical solutions at once, “two in one”, independent heating and hot water supply. Today there is a huge amount of information available to the average person on the topic of gas boiler equipment. Let's try to figure out what exactly we need, which model to give preference to, and what technical parameters of double-circuit boilers we should pay attention to.

To begin with, you should clearly outline the range of requirements for an autonomous heating system, which arise from the existing technical living conditions and your own domestic needs. Eg:

what area of your house, apartment, country house requires heating;
what are the climatic conditions of your region;
at what time of year the operation of the heating system is most relevant;
what is the duration of the heating period for your home;
what is the on/off cycle of the gas boiler;
the actual number of inhabitants of a residential building;
the level of domestic comfort in the house, including the intensity of heating, the degree of furnishing of housing with external thermal insulation and the possibility of hot water supply;

Having answered these questions, you will be able to approach the solution of the problem in more detail and independently choose a model of a double-circuit gas boiler for your apartment or private house. Often the choice determines the cost of the units, methods and conditions for installing gas boilers in specific conditions.

Gas boilers

Gas boilers are considered the most economical and energy efficient. Since the type of fuel is not expensive, the possibility of connecting to a central gas supply is possible everywhere. The principle of operation involves the transfer of heat through the heating system due to the coolant in them. During the combustion of gas in the boiler burner, heat is released, which heats the coolant, which in turn, passing through the entire heating circuit, releases heat, heating the air.

There are two types of gas boilers:

Single-circuit.
Dual-circuit.

The operating principle of a single-circuit gas boiler is to remove coolant from the boiler burner .

Double-circuit boilers are designed a little differently. One circuit of such boilers serves only to heat water, which is used for heating, and the second serves for hot water supply. In terms of economics, double-circuit boilers are more economical, since you receive both heat into the house and hot water from the tap for domestic needs.

There are both floor-mounted and wall-mounted boilers. Wall-mounted ones are the most practical, take up little space and there is no need to allocate a separate room (furnace room).

Currently, gas boilers are equipped with modern protection systems , which automatically turn off the boiler at the slightest danger.

Specifications

The first thing you need to pay attention to is whether a double-circuit boiler is suitable for your water supply system. Malfunctions of the cold water supply system can lead to serious damage to heating equipment.

Important! When choosing a gas boiler model, it is necessary to find out the ability of the structure to respond to changes in operating pressure in the cold water system. Manufacturers usually indicate in the accompanying documentation the minimum operating water pressure threshold required to turn on the boiler and its subsequent operation.

Double-circuit boilers are usually used for heating in small residential buildings, where hot water supply does not require a long pipeline. An essential point is the number of inhabitants in the house. If several hot water distribution points are used simultaneously and intensively, there is a high probability that the volume of hot water will be insufficient for domestic needs.

For example: it is better to install a gas boiler in the kitchen or bathroom, where there is no need to lay a long water supply pipe. If the hot water supply pipe is more than 7 m long, the waiting time for hot water to flow from the tap will be long.

Single-circuit or double-circuit gas boiler

Single-circuit or double-circuit: which gas boiler to choose and why?

The question of how hot water supply will be organized in the house must be decided as early as possible - even at the stage of choosing a gas boiler. The optimal solution takes into account all the features of the house.

Connection diagram for a double-circuit boiler. Connection diagram for a single-circuit boiler and an indirect heating boiler.

A single-circuit gas boiler is intended only for heating rooms, unless of course it is used with an indirect heating boiler. A double-circuit boiler easily copes with both heating and preparing hot water.

Double-circuit gas boiler. A heat exchanger, which is additionally responsible for heating water from the cold water supply system, a three-way valve that controls the movement of the coolant. It has two positions, in one it will direct the coolant to the central heating system (your radiators), and in the second it will direct it to the heat exchanger to heat the water in the domestic hot water system, but this will only happen if someone decides open the hot water tap. All double-circuit gas boilers have a priority for hot water: while the hot water tap is open, the central heating system will be disconnected from the boiler, in other words, if someone takes a shower for 2-3 hours, the room may get colder.

Single-circuit gas boiler. Strangely enough, it costs more than a dual-circuit one, although it has less functionality. There are a huge number of different types of single-circuit gas boilers in Belarus, but they are less popular than double-circuit ones, as they require additional investments. One of the main additions to a single-circuit gas boiler will be an indirect heating boiler. It is a tank inside which a coil is installed; the coolant circulates and heats the water in the tank. You will also have to purchase a three-way valve (unless, of course, it is not included in the kit, for example, Ariston gas single-circuit boilers are often not equipped with this option), it controls the flow of coolant from the boiler.

A huge problem with double-circuit boilers arises when someone is trying to wash dishes in the kitchen, and someone is taking a shower. So, double-circuit gas boilers are not initially designed for the simultaneous use of two hot water taps. If you have finally decided to buy a double-circuit gas boiler and are ready to fight this disease, then you should know that to prepare a hot bath, the minimum power of the gas boiler must be at least 18 kW; to take a shower, you will need a gas boiler of at least 16 kW kW power. But so that your shower does not turn into a contrast shower the moment you open the second hot water tap, take a closer look at choosing a boiler with a power of 28 kW. But not everything is so simple, by purchasing a powerful boiler you will certainly get rid of the problem of a contrast shower, but you will immediately acquire a second, more significant problem. If the area of the heated room being used is small, about 60-130 m2, your boiler will soon fail due to frequent switching on and off.

Single-circuit boilers. Everything is simple here, if you don’t have enough hot water, just change the boiler to a more capacious one. For example, if 4 people live, the boiler costs 80 liters and you realize that you don’t have enough of it, change it to 140 or 200 liters, but remember, if your choice is the latter, then it is better to take this model in a floor-standing version, if 200 liters turned out to be not enough for you, then in this case, purchase a water heater with two coils and the problem will be solved. (you can find out more by reading the article...)

A double-circuit gas boiler has everything. As a rule, double-circuit boilers are already equipped with everything: circulation pump, safety valve, three-way valve, membrane expansion tank. All you have to do is hang the boiler, supply gas and install a coaxial chimney. On the Belarusian market, the Eolo Star 24 3e model from Immergas is additionally equipped with hot water and heating filters.

In single-circuit boilers, everything will have to be purchased separately. If you find an expansion tank there, then not all models have a three-way valve. Moreover, placing all the equipment will take up quite a bit of space; you are unlikely to be able to install it in the kitchen like a double-circuit boiler.

As mentioned above, the double-circuit boiler has no equal in compactness. Since an indirect heating boiler is unnecessary and due to the already installed fittings in the housing, it is easier to find a place for it.

A double-circuit boiler will be more economical. It will only turn on when you need hot water. A single-circuit gas heating boiler turns on whenever the water temperature in the water heater drops below the set minimum. And even if you don’t use water, a single-circuit boiler always spends fuel to heat it.

But a single-circuit boiler is more convenient to use. Thanks to the pump, hot water will immediately and evenly flow from the tap. It won't get colder if someone decides to use the hot tap in another room.

But remember, the load on a double-circuit boiler will be much greater than on a single-circuit one, which means that the likelihood of a heat exchanger failure in a single-circuit gas boiler will be lower than in a double-circuit one.

if you use one tap, then feel free to take any double-circuit boiler of at least 18 kW.

if in your home there is a possibility that 2 hot water taps will be open at the same time, then you need a double-circuit boiler with a capacity of at least 24-28 kW.,

if you know that you will have 3 hot water taps in operation, then in this case you will have to purchase a modern and comfortable heating system with a single-circuit boiler and an indirect heating boiler.

What is a double-circuit gas boiler?

The first thing that captivates you about double-circuit boilers is their compactness. Indeed, in terms of their dimensions, such models simply fit perfectly into the layout of a city apartment, and are convenient and practical for installation in a small private house. Having studied in detail the technological capabilities of each model and their functionality, you can choose a gas boiler that best suits your needs and technical requirements.

Most often, double-circuit boilers are mini-boiler rooms equipped with all the functions necessary for domestic use. The wall-mounted version is more practical and convenient. Modern models are able to effectively solve the problem of heating residential premises and provide residents with hot water for household needs. The presence of automation ensures a high degree of reliability of the units.

Gas boiler circuits

The first circuit of a gas boiler always means a heating circuit. The boiler has one input and one output for heated water.

In double-circuit boilers, in addition to the first heating circuit, there is another circuit for heating drinking water in flow-through mode. And accordingly, two more pipes are added - one for cold water inlet, the second for hot water outlet.

The boiler independently switches heating from heating to the drinking (second) circuit when a flow appears in the second circuit. When heating hot water, the heating circuit does not work (does not heat up).

Features of the internal structure and technical parameters of the units

Wall-mounted double-circuit boilers are today the most common type of heating equipment that can be found in a city apartment. Compared to single-circuit boiler models, such units are much cheaper. The optimization of all equipment installed inside the structure itself has an impact.

For comparison: the lightness of the entire unit is achieved through the use of heat exchangers made of stainless steel and bimetallic material in the design. Instead of a storage tank for hot water, the design uses a flow-through heating method. To create the required pressure in the system, usually one, or less often two, circulation pumps are installed. All other structural elements - sensors, automation, main and safety valves, gas burner are small in size, closely interact with each other and are arranged in a small volume.

The diagram below shows the structure of a two-pipe household gas boiler and the principle of its operation.

A floor-standing boiler is much more powerful and heavier. Cast iron or steel heat exchangers, a storage tank for hot water (indirectly heated boiler) - all this and much more have significant dimensions and weight, which places increased demands on the strength of the floor of the room. To install a floor-standing double-circuit gas boiler, you will need a special place or even a separate room, which must have a good exhaust hood and be equipped with a chimney. Such units are usually installed in large country houses, in private residential buildings of two or more floors.

As for choosing a specific model of a wall-mounted gas boiler, here too you should take your time. For efficient operation of gas heating equipment, draft is required, due to which the fuel burns in the furnace. Some models are designed for natural draft, while others, on the contrary, are equipped with fans for forced ventilation. Comparing both options, there is a lower cost for units with natural draft and an open combustion chamber. On the other hand, in this case you will need to organize a chimney, which must strictly comply with all technical norms and standards.

Note: a bulky chimney pipe is not suitable for a city apartment. Which of your neighbors will like smoke in their apartment from your chimney?

* Models with a closed firebox and forced ventilation are more expensive, however, they are more practical and reliable in operation. For a double-circuit boiler with a closed combustion chamber, a coaxial chimney is installed, which is a compact pipe acting at the inlet and outlet. Such structures are small in size, do not require much space, and can be installed in a city apartment.

What to pay attention to: if hot water is used intensively in the house, it is better to equip the heating system with a gas boiler with an additional storage tank for hot water. The reserve is 50-60 liters. will be appropriate in any situation. The built-in boiler will ensure constant water pressure in the system and maintain the required hot water temperature.

Double-circuit gas boilers

Double-circuit gas boilers are most widespread in small private houses with an area of up to 150 square meters and a population of 2-4 people.

Double-circuit wall-mounted flow-type boilers will provide you with ten to fifteen liters per hour, heating it by about 30 degrees. In the maximum case, this is enough for comfortable use of two water points at the same time.

It is advisable that water consumers (washbasins, sinks, showers, etc.) be as close to the boiler as possible, otherwise you will have to wait until the cooled water runs out of the pipes and hot water flows.

The main problem with double-circuit boilers arises during their operation. Hard water can quickly clog the secondary heat exchanger, which leads to a complete stop of the boiler (not in all cases).

Double-circuit floor-standing boilers with a cast iron or steel heat exchanger are a rather rare type of boiler - their main disadvantage is a complex design and less reliability. Floor-standing gas boilers are used because of their reliability, long service life (since there is practically nothing to break) and a wide range of capacities. We also recommend considering the option with a single-circuit floor-standing gas boiler and a free-standing (or hanging) indirect heating boiler.

Advantages of double-circuit boilers

Low cost of the secondary circuit. With a small difference in price of a single- and double-circuit boiler, an inexpensive source of hot water supply appears
Compact boiler installation (all equipment is located in one building)

Disadvantages of double-circuit boilers

Rapid failure of the secondary circuit with hard water
Simultaneous use of hot water is limited to two consumers
When heating hot water, the heating circuit remains switched off
Hot water circulation is not possible (prevents the water in the pipes from cooling)
In summer you have to wait a long time for warm water (more than 30 seconds)
When using water, temperature changes are felt

Automation

For gas heating devices, one of the most important design elements is automation. Today, not a single model of gas boiler is produced without automatic devices for monitoring the operation of heating equipment, which can be mechanical or electronic. The choice of equipment in this case is up to the consumer.

Models from foreign manufacturers are almost all equipped with electronic automation devices. This approach makes modern heating equipment high-tech devices capable of operating in various modes and independently monitoring the current state of all elements of a single mechanism. A significant obstacle for many consumers is the cost of such boilers. In some cases, gas boilers equipped with electronics become hostage to the power supply system. No electricity, no heating. Frequent breakdowns and failures of gas boilers with electronics entail additional costs for repairs and maintenance of equipment.

For reference: gas boilers equipped with electronic automation more often fail due to breakdown of the electronic components of the system (every second boiler breaks down due to faults with the electronics). Frequent power outages and power surges negatively affect the operation of gas heating units with electronic automation devices.

The optimal option for our conditions would be to purchase a boiler with an independent power supply or with mechanical control devices. Such models are a budget option. They are practical and unpretentious in their work.

Selection criteria: what to look for when purchasing

When choosing a device, it is advisable to analyze the technical characteristics of the product. The most important are:

boiler power - depends on the area of the heated room;
fuel type - natural gas, propane, mixed type;
coolants used - water or antiphysis;
Efficiency of the device;
maximum coolant temperature in the heating circuit;
gas operating pressure range;
weight and linear dimensions of equipment;
fuel consumption.

When choosing a boiler, the efficiency of the device and fuel consumption are taken into account.

Selection of required characteristics

A balanced assessment of equipment characteristics allows you to select a device that is optimally suited to the needs of the consumer. So, for heating an apartment or house with an area of up to 100 square meters. m, a device with a power of 15-20 kW is suitable. Installing a higher capacity will not be economically feasible.

Floor structures are recommended for heating large rooms. Wall-mounted models are often installed in apartments and country houses. A unit with optimal technical parameters can effectively heat a room without increasing fuel and electricity costs.

Boiler power. What should you pay attention to?

The key points that influence your choice may be the power of the boiler. You should not immediately settle on high-power gas two-pipe boilers. The technical progress that we have achieved allows us to produce models designed for different household needs. The main thing is to objectively approach the requirements that you place on an autonomous heating system. Choosing a double-circuit gas boiler will be successful if you have a ready-made project at hand and you listen to the advice of experts.

The table clearly shows how you can determine the optimal boiler power in each specific case

It should be noted that many owners of apartments and private houses mistakenly approach the issue of determining the optimal power of a heating unit. There is a misconception that all mounted models of double-circuit gas boilers have a power of 24 kW. A detailed acquaintance with the offer on the market will clarify the situation for you. Typically, the power of such models varies between 17-35 kW. A key aspect of determining power is the number of hot water intake points in the house. It is necessary to select a double-circuit gas boiler taking into account the rule - the more hot water taps, the more boiler power is required.

For example: a private house with an area of 200 m2 can be fully heated by a double-circuit boiler with a capacity of 24 kW. However! If the house has two bathrooms, then this power will not be enough for normal hot water supply. Therefore, when buying a boiler, you need to take into account the number of hot water intake points.

Of the total boiler power, a third is spent on heating, that is, 5-10 kW. The remaining kilowatts are used to heat water in the hot water supply system of a residential building. In other words, 30-40% of the boiler power is enough to heat the house, the rest of the power is necessary for the normal operation of the hot water system.

Having settled on the optimal power parameters of the gas boiler, add another 10-20% to this figure, taking into account the heat losses that are inevitable when operating an autonomous heating system. In many ways, the amount of heat loss depends on the thermal efficiency of a residential building. Timely work done to insulate living spaces in a house or comprehensive insulation of apartments will allow the heating equipment to operate at optimal levels.

The principle of operation of double-circuit gas boilers

Gas currently remains one of the most accessible and inexpensive sources of energy for home heating. By installing gas equipment, you not only use fuel efficiently, but you can also regulate the required temperature.

Schematically, a wall-mounted double-circuit gas boiler is connected as follows.

The heating apparatus itself is placed on the wall in the place where there is a connection to the gas main, as well as the chimney pipe (which is located in the hole in the wall).

The boiler circuit responsible for hot water supply is not closed. A pipe is connected to the unit, which supplies cold water, and the already heated water is discharged through the pipe to the point of consumption: to the kitchen sink, to the bathroom.

As for the heating circuit, it forms a closed system through which water circulates. The speed of this circulation is determined by the pumping unit.

Thus, the boiler design includes several types of pipes, including: for connection to the gas main, heating supply to the system, “return” of the heating circuit, inlet and outlet of the cold water supply and, accordingly, heated water.

The circuits in the device do not intersect, which means they work independently of each other. When turning on a hot water tap, priority is given to the hot water supply circuit. Subsequently, the system is rebuilt to the standard operating mode of the heating circuit.

The video describes the structure of the boiler, connection diagram and operating principle:

What kind of heat exchanger should be in a double-circuit boiler?

If you set out to ensure maximum comfort in your apartment, you should not go to extremes and try to buy everything at once. It is important to remember: “better is the main enemy of good.” Modern wall-mounted models of double-circuit boilers are available with two types of heat exchangers:

separate products;
bithermal devices;

Separate product units are boilers that have two heat exchangers. The main or main one is used to heat the coolant in the heating system, while the secondary heat exchanger is designed to heat water in the hot water supply system. In the first type, the main work is done by heating the heat exchanger, which is responsible for the operation of the heating system. The secondary heat exchanger is already by indirect heating due to the heated water coolant in the DHW system.

When choosing such a model for yourself, be guided by its fairly high cost. The reason for the high price is the larger number of individual elements and additional functions.

Note: A significant advantage of boilers with separate heat exchangers is the absence of scale formation in the heat exchanger, which provides indirect heating. In addition, this scheme completely eliminates boiling of water in the system.

The second option is that boilers with bithermal heat exchangers have dual elements. During operation of the boiler, simultaneous heating of the coolant for heating and water for the hot water system is carried out. Accordingly, in such systems scale forms faster and the permeability of the coolant and hot water in the pipeline deteriorates.

What to look for when choosing a double-circuit wall-mounted gas boiler?

The main criterion for choosing a high-quality heating installation is determining the required boiler power.

Wall-mounted device models can, on average, heat a building with a total area of 250 m2. To determine the required power, take the data in the calculation of 1 kW per 10 m2 . It is necessary to take into account that the design requires additional power to operate the secondary circuit (providing hot water supply). That is why, add another 25 - 30% to the calculated value obtained. This way you will get the required installation power.

To ensure reliable and uninterrupted operation of the equipment, it is recommended to purchase a voltage stabilizer, which will increase the service life of the automation in the boiler design.

We create the necessary level of comfort

The choice of boiler equipment must fully comply with the requirements for an autonomous heating system. What can influence the efficiency of a double-circuit boiler? Changes in outdoor temperature depending on the climate conditions of the region in which you live.

An extensive range of double-circuit boilers allows you to independently determine for yourself which method of controlling gas heating equipment is most suitable for you. Today, models of units are produced with the following types of power control systems:

single stage;
two-stage;
three-stage.

The most common and popular are models that use a two-stage boiler power control system. It is these boilers that are easy to adapt to seasonal and daily changes in air temperature. The ability to adjust operation in two modes ensures optimal heating of the coolant in the system, depending on whether it is warm or cold outside. Adjusting the heating intensity significantly extends the service life of the burner and heat exchanger.

Boilers with a single-stage adjustment system are less convenient to operate. Such models are much cheaper, and this, naturally, determines the limitations of their technological capabilities.

Gas boilers equipped with three-stage power control devices are an order of magnitude more advanced than other options. Such units are completely universal and autonomous in operation, however, the high cost limits the popularity of the use of these high-tech devices.

Single-circuit gas boiler

Diagram of a single-circuit gas boiler.

A single-circuit boiler is a heat production device designed to heat the coolant of a heating system. They are also called single-stage. They can be either wall-mounted or floor-mounted, the choice is wide. Wall-mounted single-circuit boilers have low power, so they are ideal for heating apartments, thereby saving space. Floor-standing single-circuit boilers have cast iron heat exchangers in their design, which makes their weight quite significant, which is why they cannot be mounted on the wall, while wall-mounted ones are light and ergonomic.

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Floor-standing systems have high power and, thanks to this, when combined with a boiler, they can provide not only heating, but also water heating to provide hot water supply. Wall-mounted gas boilers do not have this capability. Among the disadvantages, it can be noted that a system with a boiler will be more bulky and will not have a sophisticated design, while wall-mounted boilers that are not burdened with a boiler are small and usually quite original in design.

The choice of a boiler for a single-circuit system should be based on meeting all the needs of the residents. To improve collaboration with the boiler, the water heater temperature sensors are connected to the boiler operating mode control system, and, thanks to this interaction, the system will maintain the desired water temperature in the range of 35-65 ° C, working synchronously with the boiler. If the temperature in the boiler begins to drop or the hot water runs out, the boiler will simply direct water from the heating system to the boiler coil for additional heat transfer. A single-circuit floor-standing boiler can perform the function of providing water for hot water supply all year round; to do this, simply set the “summer” function in its settings, and the water supply for heating is shut off.

Diagram of a floor-standing gas boiler.

Thanks to the constant supply of hot water from the boiler, you can save time and not wait for it to heat up - water at the desired temperature will immediately come out of the tap. In addition, the sufficient power of this system makes it possible to connect additional devices, such as, for example, a coil for drying towels in the bathroom. But at the same time, you need to choose the right boiler power so that the boiler does not heat up for too long and does not lose heat when heated. For convenience and to minimize heat loss, they have now begun to produce single-circuit boilers with a boiler already built into the system. Power is usually selected depending on the size of the building, the number of glazed windows and doorways.

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The main advantages of single-circuit systems:

easy to customize to suit any user needs;
different mounting options available: floor, wall;
selection of different variations of heating and water supply systems (combination with a boiler);
the possibility of creating a cascade boiler system;
simplicity of design of both wall-mounted and floor-standing boilers;
high reliability;
availability.

Which manufacturer should you choose?

Autonomous heating is not a one-day project. Your comfort not only today, but also in subsequent years, depends on the choice of boiler model and other elements of the system, so you should not save on equipment in this case. The only way out of this situation is to carefully study the existing offers on the market and take into account the reputation of the manufacturers.

Well-known companies and firms in the world that produce heating equipment try to maintain their brand and value their reputation. Boiler models from leading manufacturers are reliable, practical and easy to use. The slight difference in cost is compensated by the absence of problems with the equipment during operation.

However, you should not blindly believe in the reliability of models from foreign manufacturers. There are often cases when imported equipment turns out to be completely unadapted to our realities. The efficiency of a gas boiler can be affected by the quality of the coolant. It is also important to have a repair and maintenance base in your region. Buying a unit for which it is difficult to get components and spare parts, and which will also have to be repaired in a makeshift way, is the most ridiculous mistake. Take your choice responsibly in all aspects! The ideal choice is to purchase equipment adapted by the manufacturer to Russian conditions.

How to choose - selection criteria

To heat individual housing, modern industry produces many models of double-circuit gas boilers. Which device is better to choose depends on the parameters and purpose of the structure. A successful purchase depends on suitable characteristics.

Power

This is the main parameter that influences obtaining the required comfort in a building. It is measured in kW and calculated taking into account the design features of the building.

For a full calculation, it is necessary to take into account: floor height, total area, the presence of windows, external walls and internal partitions, the material from which the load-bearing structures are made, insulation of partitions, walls, ceilings and interfloor ceilings. In everyday life, a simpler formula is used.

How to calculate sufficient power

A rough calculation is made by multiplying the area by a factor of 0.1, respectively, for a house with an area of 450 m2, equipment with a power of 45 kW will be required.

This is a simplified method of calculation and it is valid for central Russia. For the southern regions, a coefficient of 0.8 should be applied, and for the northern territories - 1.5. In addition, it is recommended to add an insurance reserve to the calculated power in case of abnormal temperature changes; for this you need to increase the value by 10%.

Formula for calculating boiler power.

Boiler features

What is the difference between a single-circuit gas boiler and a double-circuit gas boiler? Single-circuit is responsible only for heating: one or more pipelines provide radiators and/or heated floors with coolant.

The DHW problem has to be solved separately. There are two solutions, more on them below.

Diagram of a single-circuit gas boiler.

What does a double-circuit gas boiler mean: it is possible, using the same unit, to heat water both for heating and for household needs (what are floor-standing double-circuit gas boilers for heating a private house). This happens thanks to a double heat exchanger or two separate heat exchangers in the boiler design.

Heat exchangers of dual-circuit models are of flow and boiler type. Flow-through ones are usually low-power, they are suitable for houses or apartments with a small number of users.

Boiler models are equipped with a water tank with a capacity of up to 180 liters. The water in such boilers is heated in both storage and flow modes. In running water the water is colder, because... does not have time to heat up.

Diagram of a double-circuit gas boiler.

The second design difference between dual-circuit units is the structure of the heat exchanger. A combined heat exchanger consists of two containers of different sizes, one built into the other. The water in the internal tank, intended for domestic hot water needs, is heated by the coolant in the external (heating) heat exchanger. For separate heat exchangers, these two containers are located next to each other.

The main difference between a single-circuit boiler and a double-circuit boiler is that the use of hot water from the boiler does not affect the heating process. In dual-circuit models, DHW is a priority: when hot water is required for a shower or kitchen, the boiler switches to servicing them, but the coolant is not supplied to the heating circuits.

The switching of circuits is performed by a three-way valve that responds to the opening/closing of a hot tap: in the open position of the tap, the valve switches the boiler to supply hot water; in the closed position, it switches to the heating circuit. Both circuits cannot operate at the same time.