Choosing a double-circuit wall-mounted gas boiler: advice from consultants + review of brands and prices

Device and principle of operation

A modern double-circuit gas heat generator is a rather complex structure, which includes many individual elements, the coordinated operation of which is ensured by an electronic control unit.

Gas boiler design

Regardless of the performance characteristics, a two-circuit installation consists of the following main modules:

• gas burner, which can be installed in both open and closed combustion chambers. Thanks to this element, the coolant is heated in the heating circuit and the DHW circuit.The automatic control system (ACS) regulates the intensity of fuel combustion, which makes it possible to maintain the coolant temperature within the specified limits.
• combustion chambers, open or closed type. When using a closed chamber, a fan is located above it, which provides air supply to the combustion zone and removal of combustion products.
• circulation pump, with the help of which forced circulation of the coolant is carried out through the heating circuit and DHW pipelines.
• Three way valve, designed to switch the unit to the DHW circuit.
• Main heat exchanger. This element is located in the combustion chamber above the gas burner. When the coolant passes through the inner section of the heat exchanger, there is an intense transfer of thermal energy from the walls of the heat exchanger to the coolant. In modern gas boilers, this module can be made of stainless or galvanized steel; some premium models use copper heat exchangers.
• secondary heat exchanger, providing heating of running water.
• Automatic system control that regulates the intensity of combustion, the temperature of the coolant. It is the electronic control unit that provides timely ignition of the burner, turning on and off the elements of the unit, and ensures the autonomous operation of the boiler.

Branch pipes for supplying cold water, gas, hot water outlet and heating system coolant are located on the bottom panel of the device case.

The principle of operation of a double-circuit gas heat generator

A distinctive feature of double-circuit boilers is that mixing the coolant with the running water of the DHW circuit is impossible under any circumstances.The heating system is filled with a coolant through a special neck, and running water is heated by circulating a part of the coolant in the secondary heat exchanger.

Since the simultaneous operation of the unit in two modes is impossible, we will consider the operation of the system in heating mode and in hot water mode.

Heating mode

If the boiler is connected to the heating circuit, the essence of its work is as follows: the circulation pump ensures the movement of the coolant through the pipelines of the heating system. When you turn on the gas burner, the coolant is gradually heated due to intensive heat exchange with the walls of the heat exchanger. Upon reaching the set temperature parameters, the electronic control unit shuts off the gas supply. When the temperature in the heating line drops, the burner ignites again.

If there is a temperature sensor in the house, the automated control system will correct the system operation taking into account the data received from it. All the heat generated by the burner, in this case, is spent on the heating circuit, and the position of the three-way valve prevents the coolant from entering the secondary heat exchanger. Depending on the type of combustion chamber, exhaust gases can be removed both through a natural chimney and forcibly.

DHW mode

To switch to mode hot water supply it is enough to open the mixer valve, while the three-way valve blocks the circulation of the coolant through the heating main, and the automatic control system ignites the gas burner.

The three-way valve ensures that the heated coolant enters the hot water heat exchanger, where the heat energy is transferred from the walls of the heat exchanger to running water.When the tap is closed, the three-way valve returns to its original position, and the unit switches to the heating mode discussed above.

However, it should be remembered that in the case of prolonged operation in the DHW mode, the efficiency of the heating system may decrease.

Connection diagram for boilers with two circuits

The main gas, to which urban residential buildings, enterprises and public institutions are connected, is the cheapest fuel. Even taking into account the paperwork and approvals in several instances, the installation of gas boilers justifies itself. A properly selected model will be able to serve both the heating system and supply sanitary water.

The boiler is installed in a place convenient for maintenance. With proven circuits connection of double-circuit gas the unit will be introduced by the article recommended by us. It is necessary to provide a safe connection of the gas pipe that meets the installation standards and lead the chimney to the outside for transporting combustion products.

Connection diagram of a wall-mounted double-circuit boiler. Yellow line - natural gas supply, blue - cold water, red - hot water, purple and pink - heating circuit

Cold water is supplied to the boiler, after heating (when a certain temperature is reached), it is transported to the points of water intake, the main of which are a shower cabin, a bathtub, a sink in the kitchen.

The in-house heating network is a closed circuit with a circulating coolant that serves the “warm floor” system, radiators, convectors and a heated towel rail in the bathroom.

When choosing a boiler, it is necessary to take into account its performance, since household-class double-circuit equipment is not designed to service a large number of connected water distribution and heating devices

An alternative to installing a two-circuit model is to install a 1-circuit boiler + BKN kit, where an indirect heating boiler serves the hot water supply system. This scheme is good because hot water of the required temperature is always present in the taps.

The disadvantage of installing a boiler is easily understood by owners of houses and apartments with a shortage of free space. Another drawback concerns the cost of a kit with a single-circuit boiler - it comes out more expensive than a double-circuit boiler

In double-circuit models, the heating system and hot water inside the device do not intersect, which gives its bonuses. For example, not a universal filler - water, but a special solution is used as a coolant.

Boiler power

One of the key points in choosing a heating boiler is determining the required power. If we approach this with full responsibility, it is necessary to consider the heat loss of each room, if we are talking about an apartment or a building as a whole, if the boiler is selected for heating a private house. The calculations take into account the materials of the walls, their thickness, the area of ​​windows and doors, the degree of their insulation, the presence / absence of an unheated room at the bottom / top, the type of roof and roofing material

Geographic location and a whole bunch of other factors are taken into account

Such a calculation can be ordered from a specialized organization (at least in GorGaz or a design bureau), if desired, you can master it yourself, or you can take the path of least resistance - calculate based on average norms.

Where does the heat leave the house?

Based on the results of all calculations, the norm was derived: 1 kW of heating power is required for heating 10 square meters of area. This standard is suitable for rooms with ceilings of 2.5 m, with walls with an average degree of thermal insulation. If your room falls into this category, divide the total area that needs to be heated by 10. You get the required boiler output. Then you can make adjustments - increase or decrease the resulting figure, depending on the actual conditions. It is necessary to increase the power of the heating boiler in the following cases:

• The walls are made of a material with high thermal conductivity and are not insulated. Brick, concrete fall into this category for sure, the rest - according to the circumstances. If you are choosing a boiler for an apartment, you need to add power if the apartment is corner. For "internal" heat loss through them is not so terrible.
• Windows have a large area and do not provide tightness (old wooden frames).
• If the ceilings in the room are higher than 2.7 m.
• If in a private house the attic is not heated and poorly insulated.
• If the apartment is on the first or last floor.

The design power is reduced if the walls, roof, floor are well insulated, energy-saving double-glazed windows are installed on the windows. The resulting figure will be the required power of the boiler. When looking for a suitable model, make sure that the maximum power of the unit is not less than your figure.

What you need to know when choosing a heater

You can’t just go to the store and buy a gas heating boiler. To select a suitable model, it is necessary to prepare a list of requirements for the unit - to determine the thermal power, the necessary functions, the method of installation and other initial data.

What items are on the list:

1. Calculate the amount of heat required to heat a cottage or apartment.
2. Outline the scope of tasks for a gas boiler - it should only heat the building or, in addition, serve as a water heater for household needs.
3. Allocate a place for the installation of a heat generator. The rules allow installing gas-using heating equipment in the kitchen (power - up to 60 kW), an attached boiler room or in another separate room located near the outer wall of the dwelling.
4. Decide whether the boiler is to be installed on the floor or on the wall. For apartments, only the hinged version is suitable.
5. Consider how your heating system works. Under the gravitational scheme with natural circulation of the coolant (the so-called gravity flow), an appropriate non-volatile heater operating without electricity is selected.
6. Set the machine automation level according to your wishes. Examples of useful functions: maintaining the indoor temperature according to a schedule or signals from an external weather sensor, remote control via the Internet, and so on.
7. Estimate the prices of various boilers and find out how much you are willing to spend on a gas boiler.

Before choosing a new or changing an outdated gas boiler for heating a private house, we highly recommend that you consult with the subscriber department of Gorgaz (or another management company). Why is it needed:

• in addition to the general rules, regional offices have internal instructions that restrict the use of gas equipment, these points should be clarified;
• a new or replacement boiler must be included in the project documentation, otherwise you risk getting a fine for installation without approval;
• experts will help you to properly place the heat generator in the house.

In the project of the boiler house, the location of all heat generators is indicated with dimensional references to building structures

Another example: you want to remove a horizontal (coaxial) chimney from a room in an apartment building, but the office does not agree on this decision, since the protruding pipe spoils the appearance of the facade. To understand all the subtleties, you will have to understand the existing varieties of gas heaters, but first ...

Criterias of choice

heated area (we are looking for models for rooms up to 100 m², up to 200 m², up to 300 m² and over 350 m²);
the number of circuits and the required volume of hot water supply (single-circuit with a built-in tank for a small apartment and 1-2 people, single-circuit with an indirect heating tank for a family of 3-4 people, double-circuit with one draw-off point, with two, etc.);
volatile, but economical, automated and ultra-modern or non-volatile, but very simple and unpretentious with mechanical control and a minimum of sensors (in areas with frequent and long power outages, the owners risk being left without heating in winter by choosing a volatile boiler);
if there is a separate boiler room, it can be taken with an open chamber, or it can be closed for a coaxial chimney, in a separate room it is easier to organize a bundle of a wall-mounted single-circuit boiler + a heating tank for hot water supply;
if there are problems with pressure in the gas main, a voltage drop in the mains, then look for boilers whose "brains" can withstand it, not all expensive imported models will be able to ensure trouble-free operation in our extreme conditions;
pay attention to additional functions not only for the boiler, for example, it is very convenient to have a chimney with frost protection, otherwise you will have to manually get rid of terrible icicles on the coaxial pipe or on the roof near the chimney, which will stop the boiler from working;
remember that the boiler will be only a part of the heating system, not only it is important, but also the optimally coordinated and correct operation of all components;
think over the maximum protection against gas leakage, do not save on safety, relying only on the brand or the reliability of modern electronics.

The choice between atmospheric and turbocharged boiler

When choosing a floor heating device, many are interested in the question, which unit is better to choose - atmospheric or turbocharged.

It depends on the conditions of use. Atmospheric gas boiler torch suitable in case of:

• the need for heating a large area;
• in conditions of work on several types of fuel;
• with frequent power problems.

A turbocharged unit is chosen when:

• the inability to allocate a separate furnace;
• small heating area;
• heating device for an apartment building.

Another positive aspect of atmospheric units is their lower cost compared to turbocharged ones. If you choose a model with a minimum configuration, then it will be inexpensive.

Note! Atmospheric boilers are forbidden to be installed in an apartment of a multi-storey building

The principle of operation of double-circuit gas boilers

Gas at the moment remains one of the most accessible and inexpensive sources of energy for home heating. By installing gas equipment, you not only consume fuel rationally, but you can also regulate the required temperature regime.

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

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

In the device, the contours do not intersect, which means that they work independently of each other. When a hot water tap is turned on, priority is given to the hot water circuit. In the future, the system is rebuilt to the standard operating mode of the heating circuit.

The video shows the structure of the boiler, connection diagram and principle of operation:

TOP-10 rating

Consider the most popular models double-circuit gas boilers, recognized by experts and ordinary users as the most successful in terms of design and operation:

Buderus Logamax U072-24K

Gas double-circuit boiler designed for wall mounting. Equipped with a closed-type combustion chamber and a separate heat exchanger - primary copper, secondary - stainless.

Heating area - 200-240 m2. It has several levels of protection.

Models with the index "K" perform heating of hot water in flow mode. It is possible to connect a room temperature controller.

Federica Bugatti 24 Turbo

Representative of Italian heat engineering, wall-mounted double-circuit gas boiler. Designed to work in a cottage or public space up to 240 m2.

Separate heat exchanger - copper primary and steel secondary. The manufacturer gives a 5-year warranty period, which indicates confidence in the quality and operational capabilities of the boiler.

Bosch Gaz 6000 W WBN 6000-24 C

The German company Bosch is known all over the world, so it does not need additional introductions. The Gaz 6000 W series is represented by wall-mounted models designed for operation in private homes.

The 24 kW model is the most common, it is optimal for most residential and public buildings.

There is a multi-stage protection, the copper primary heat exchanger is designed for 15 years of service.

Leberg Flamme 24 ASD

Leberg boilers are usually referred to as budget models, although there is no noticeable difference in cost with the products of other companies.

The Flamme 24 ASD model has a power of 20 kW, which is optimal for houses of 200 m2. A feature of this boiler is its high efficiency - 96.1%, which is noticeably superior to alternative options.

Works on natural gas, but can be reconfigured to liquefied gas (replacement of burner nozzles is required).

Lemax PRIME-V32

Wall-mounted double-circuit boiler, the power of which allows you to heat 300 m2 of area. It is suitable for two-story cottages, shops, public or office spaces.

Produced in Taganrog, the basic technological principles of assembly were developed by German engineers. The boiler is equipped with a copper heat exchanger providing high heat transfer.

It is calculated on operation in difficult technical conditions.

Navien DELUXE 24K

Korean boiler, the brainchild of the famous company Navien. It belongs to the budget group of equipment, although it demonstrates high performance.

It is equipped with all necessary functions, has a self-diagnosis system and frost protection. The power of the boiler is designed to work in houses up to 240 m2 with a ceiling height of up to 2.7 m.

Mounting method - wall, there is a separate heat exchanger made of stainless steel.

MORA-TOP Meteor PK24KT

Czech double-circuit gas boiler, designed for hanging installation. Designed for heating 220 m2. It has several degrees of protection, blocking in the absence of liquid movement.

It is possible in addition to connect an external water heater, which greatly expands the possibilities of supplying hot water.

Adapted to unstable power supply voltage (permissible fluctuation range is 155-250 V).

Lemax PRIME-V20

Another representative of domestic heat engineering.Wall-mounted double-circuit gas boiler, designed to service 200 m2.

The modulating burner makes it possible to distribute fuel more economically by changing the gas combustion mode depending on the intensity of the coolant circulation. It has a separate stainless steel heat exchanger, can be connected to a room thermostat.

There is a possibility of remote control.

Kentatsu Nobby Smart 24–2CS

Japanese wall mounted gas boiler providing heating of 240 m2 and hot water supply. Model 2CS is equipped with a separate heat exchanger (primary copper, secondary stainless).

The main type of fuel is natural gas, but when changing jets, it can be converted to the use of liquefied gas. Most of the performance characteristics correspond to European boilers of similar power and functionality.

It is possible to use several design options for the chimney.

Oasis RT-20

Wall-mounted double-circuit gas Russian-made boiler. Designed to work in rooms of about 200 m2. Equipped with an efficient copper heat exchanger and a stainless secondary assembly.

The combustion chamber is of a turbocharged type, there is a built-in expansion tank and a condensate trap.

With an optimal set of functions and high build quality, the model has a relatively low price, which ensures its demand and popularity.

Gas consumption

When choosing, it is necessary to take into account what gas consumption is in a double-circuit boiler. To do this, you need to know that the consumption depends on:

• Equipment capacity;
• device efficiency;
• How many rooms will be heated and how much hot water will be needed.

You can calculate the gas consumption by the following example:

For example, a 15 kW unit.In winter, it works around the clock, which means you need to multiply by 720 hours (month). 720*15= 10800 kWh. An approximate calculation is as follows: 0.1 m3 of gas per 1 kW / hour. This means that the gas consumption per month is 10800 * 0.1 = 1080 m3. But keep in mind that the boiler does not always work at full capacity and around the clock. So the resulting cost can be divided in half.

Top Producers

1. Protherm. The products of this company please with excellent quality, high efficiency and good service life.
2. Vaillant. The equipment is characterized by high technical characteristics, low prices and long service life.
3. Immergas. This manufacturer is far from the most famous, but still boasts a wide range of reliable models with high performance and economy.
4. Bosch. The products of this company regularly appear in various ratings, due to reliability, optimal service life and excellent quality.
5. Buderus. The German brand produces good and easy-to-manage boilers.

What parameters should I pay attention to when buying

When choosing a suitable model of a gas double-circuit boiler, you should pay attention to the main technical parameters of the units:

Combustion chamber type

The most popular are boilers with a closed combustion chamber. The entire process of fuel combustion and smoke removal takes place in a system isolated from the atmosphere of the room, which increases safety for people.

In addition, a controlled smoke extraction process is much more efficient than unstable natural draft.

Power

The power level of the boiler is the main indicator that demonstrates the ability of the unit to provide thermal energy to rooms of different sizes.

Usually, the desired model is selected at the rate of 1 kW of power per 10 m2 of area.

It should be noted that a large margin should not be made, since the boiler operation mode should be close to the nominal one.

Heat exchanger material

For the manufacture of heat exchangers use:

• Stainless steel. This is the most affordable option, which is used in boilers of the medium and budget price range. The heat transfer and service life of such units are quite high, there is the possibility of repair or restoration.
• Copper. Heat exchangers of this type are installed in the most expensive and productive series of gas boilers. The indicators of copper heat exchangers are considered the highest.
• Cast iron. As a rule, it is used in powerful outdoor units. The heating mode is stabilized due to the large thermal inertia of the material.

Boiler type

There are two types:

• Convection. The usual design of the gas unit.
• Condensing. In addition to the traditional method, these models are equipped with a coolant preheating function, which reduces fuel consumption and the load on the heat exchanger.

When choosing the type of boiler, it must be taken into account that the operation of condensing devices is possible only if the difference between the external and internal temperatures is not more than 21 °, which in Russia is impossible to ensure due to climatic conditions.

Energy independence

There are volatile and independent installations. The former have the maximum set of functions, but in the event of a sudden power outage become useless.

The latter do not use electricity, which expands the geography of their use. At the same time, non-volatile models have minimal capabilities and a complex ignition method.