How to choose the right wall-mounted double-circuit gas boiler for a private 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.

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.

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Rating of the best wall-mounted double-circuit gas boilers

The rating is based on expert statements and owner reviews.

Buderus Logamax U072-24 K

The double-circuit boiler is easy to install, compact, reliable and easy to maintain. In addition, voltage surges in the electrical network do not cause malfunctions in the operation of the electronic control unit.

Specifications:

Bosch Gaz 6000 WBN-18C RN

The compact overall dimensions of the installation make it possible to use a gas boiler not only in a private house, but also in an apartment. When operating at maximum load, gas consumption does not exceed 2.2 m3/h. The electronic control unit ensures uninterrupted operation of the system in the voltage range from 170 to 260 V.

Specifications:

Hotpoint-Ariston Atleas X24

This boiler model is equipped with an unprecedented safety system that is triggered when the pressure in the gas line decreases, the water temperature rises sharply, the burner goes out and the coolant freezes in the heating system. In addition, the double-circuit wall-mounted boiler has a stylish design and is equipped with an informative liquid crystal display.

Specifications:

Baxi Eco Four 24 F

In addition to the heating function and provision of hot water, the unit can be used in conjunction with various underfloor heating systems. The protection system includes 7 autonomous modules that ensure reliable, uninterrupted operation of the device.

Specifications:

Vaillantatmo TEC pro VUW INT 200/5-3H

A gas boiler from Vaillantatmo TEC can operate in summer mode, designed exclusively for domestic hot water, which can significantly reduce gas costs. The automatic control system ensures complete safety and stability of the unit. Automation will promptly and adequately respond to circulation problems, burner failure and overheating of the coolant.

Specifications:

Before buying heating equipment, it is advisable to read reviews from owners who have assessed in practice the advantages and disadvantages of a particular model.

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.

Differences

To select the optimal heating device, you must be guided by the basic and additional characteristics of the equipment. There are two types of boilers: single-circuit and double-circuit. Which one is best for fully heating a living space?

Double-circuit and single-circuit thermal appliances differ in the following characteristics:

• in single-circuit models, only the coolant is heated;
• double-circuit units are capable of heating water separately for water supply and separately for heating;
• Single-circuit boilers are usually installed in private houses, double-circuit boilers are installed in small rooms.

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.

Design and characteristics of such units

Externally, such a boiler looks like a neat cabinet, so it will fit perfectly into the interior. All the necessary elements are placed inside; the device just needs to be connected to the heating and hot water systems. Among other advantages of wall-mounted gas boilers, the following are usually mentioned:

• the ability to use one unit to perform two tasks at once: heating rooms and heating water;
• significant reduction in utility bills (cold water is much cheaper than hot water);
• high degree of equipment safety;
• relatively low price (compared to other autonomous heating options);
• the ability to use automation systems, which minimizes maintenance and setup of the unit.

In size and performance, wall-mounted gas boilers differ markedly from each other. It is necessary to take into account a number of characteristics in order to choose a model that will provide your home with heat and hot water without incurring unnecessary costs.

Wall-mounted gas heating boilers usually have an attractive modern design and compact size; they are easy to fit even in a small kitchen

Double-circuit wall-mounted gas models usually cost significantly less than single-circuit ones complete with a boiler. The wall-mounted version of such equipment is the most common and practical. Floor-standing models are usually high-power devices, or boilers with a cast-iron heat exchanger, which are too heavy to be placed on the wall.

A double-circuit gas boiler is a compact device, essentially a version of a mini-boiler room. To heat water, such a unit is equipped with a flow-through water heater, an expansion tank, one or two circulation pumps, a safety valve, temperature and safety system sensors, a pressure gauge, etc. There is no need to allocate a separate room for such a device. It is usually placed on the wall in the kitchen.

The power of wall-mounted gas boilers is relatively small, usually about 30 kW. They are used to service premises with an area of ​​no more than 200-300 square meters. m. It is recommended to install such a boiler as close as possible to the water collection points, which should also be located nearby, i.e. the shower room should be located next to the kitchen. Typically there is only enough hot water to service one water intake point. If someone is taking a shower, washing dishes with hot water will be problematic. If the distance between water intake points in the house is too large, heating will be extremely ineffective.

The figure shows a diagram of the design of a wall-mounted double-circuit gas boiler with forced ventilation and two heat exchangers, which will help you understand the principle of operation of the device

Some models use natural draft, others use forced ventilation. In the second case, you should install not a traditional, but a special coaxial chimney. This is a compact chimney pipe, the installation of which is much simpler than the construction of a conventional chimney for a natural draft boiler.

Note! If you need to use several water intake points, it is recommended to pay attention to models that allow you to create a supply of hot water of at least 60 liters. They are equipped with a built-in boiler and a special mixer, which allows you to keep the water temperature constant at any level of water flow or pressure in the system.

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.

What is a gas double-circuit boiler: general concept

A gas double-circuit boiler can only be installed in rooms with good ventilation.

Double-circuit boilers are designed to heat a house and provide hot water using the energy of burned gas.

Principle of operation

The installation can operate in 2 modes - hot water preparation and room heating. For this purpose, the device has 2 separate circuits.

Heating of the coolant entering the heating circuit is carried out in the primary heat exchanger. The 3-way valve is designed to switch operating modes.

DHW preparation takes place in a plate heat exchanger. The operation of the device is regulated automatically.

The mechanism of operation of the dual-circuit device is as follows:

1. When the sensor detects a decrease in temperature in the room below the set value, the automation turns on the circulation pump. The coolant begins to move through the heating circuit.
2. The burner in the working chamber lights up.
3. The coolant is heated in the primary heat exchanger and enters the heating circuit. The indoor air temperature rises.
4. The cooled coolant is heated and returned to the circuit. This continues until the sensor records the air temperature level set by the user.
5. After this, circulation in the heating circuit stops and fuel combustion stops.
6. The equipment is put into operation to produce hot water when the hot water tap is opened. The 3-way valve switches and closes the coolant circulation inside the device. Running water is heated in a secondary heat exchanger and supplied to consumers.
7. After closing the tap, the burner goes out and the pump stops working.

Scheme of operation of a double-circuit boiler.

Advantages

Double-circuit heating devices operating on gaseous fuel have the following advantages:

• compact dimensions allowing installation of devices in country houses and private apartments;
• versatility - the ability to provide consumers with heat and hot water at the same time;
• automation and sensors eliminate manual control of the unit;
• high product safety;
• good selection of models of varying prices.

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.

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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.

Wall-mounted double-circuit gas boilers: reviews from owners

To heat the country house, we bought a BoschGaz 6000 W WBN 6000 - 12 C. The area of ​​the house is approximately 75 m2, so the power is quite enough for a comfortable stay. There were no failures for 3 years, I cleaned the heat exchanger a couple of times and that’s it. Very happy with the purchase. Nikolay, Novosibirsk.

When choosing a wall-mounted heating boiler, I immediately thought about the availability of components in case of unforeseen circumstances, so the choice fell on Ariston CARES X 24 FF NG. Fortunately, over the course of 2 years I never had to use the services of a service center; the system works great. The boiler copes well with heating 200 m2 and there are no interruptions in hot water.

In terms of quality and price ratio, in my opinion, domestic manufacturers are in no way inferior to their foreign counterparts, and repairs are several times cheaper. It is for this reason that I installed Lemax PRIME-V32. All the necessary information is displayed on the display, and control is completely simpler than ever. Over three years of operation, I washed the heat exchanger twice and there were no more problems.

Considering the cost of centralized heating in the apartment and the temperature of the radiators, my husband and I decided to give up this pleasure and installed Navien DELUXE 13K in the apartment. Now our only regret is that we didn’t do this earlier. The boiler perfectly heats 80 m2 of our apartment and there are no tricks with hot water.

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.

Heat exchanger characteristics

In modern double-circuit boilers, two types of boilers are mainly used - bithermic and flow-through. The first one is more used when domestic hot water consumption is low. Flow-through heaters have a developed heating surface, which ensures high water heating speed and large volumes.

Models with bithermic heat exchanger

Heating of the coolant in a gas boiler equipped with a bithermic heat exchanger occurs due to the circulation of the coolant through copper channels, the sections of which are made with a complex configuration inside the housing.

The heating coolant circulates through the external channels, and heated water for hot water is inside the tubes. The heat exchanger receives heat from the operating gas burner device.

Operating principle of a bithermic heat exchanger:

1. In heating mode, at a low coolant temperature in the circuit, an electromechanical gas flow valve supplies gas to the nozzle, which is ignited by a piezo igniter.
2. The fuel burns, and the released heat is transferred through the walls of the heat exchanger to the coolant.
3. When the set water temperature is reached, the gas supply to the double-circuit gas boiler stops and turns on automatically when it decreases.
4. When the user opens the hot water tap on the mixer, tap water will begin to flow into the DHW heating circuit of the bithermal heater. The coolant enters the small hot water circulation circuit and quickly heats the cold water.
5. After the DHW tap is closed, the valve redirects the coolant to the heating circuit.

Models with flow-through heater

The principle of operation of boilers operating on gas fuel, in the design of which a separate flow-through heat exchanger for domestic hot water is installed, is that the coolant for heating and hot water is heated in separate housings.

In a flow-through DHW heat exchanger, tap water is heated by a heating fluid, which is switched by a three-way valve.

At this moment, the water in the heating circuit of the in-house heating system continues to circulate through a separate heat exchanger, naturally, without receiving heat. In order for the system to operate reliably, an electric circulation pump and two separate expansion tanks for each circuit are integrated into it.

This scheme is more efficient in terms of specific fuel indicators, can provide a larger load for domestic hot water, and is not so sensitive to the quality of the source water. In addition, the heating surfaces of the heat exchangers are designed in such a way as to ensure maximum heat removal from the combustion chamber.

For example, in a hot water supply circuit, the flows of coolant and cold water are directed according to the countercurrent principle, which allows for maximum temperature reduction in the heating circuit and reduces the processes of scale formation on the internal heating surfaces of the heat exchanger.

We create the necessary level of comfort

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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.