Double-circuit gas boiler for heating a private house: is a boiler needed for condensing, parapet and with a closed combustion chamber

In private houses where main gas supply is provided and possible, the owners often decide the principle of gas equipment that will be located in the house. After all, a gas boiler is capable of not only heating the coolant circulating through the internal circuit and providing heating for the radiators, but also preparing hot water in the boiler for household needs. For this purpose, it is quite possible to consider purchasing a single-circuit gas boiler with an indirect heating boiler.

What is a double-circuit gas boiler and what is the difference from a single-circuit one?

A double-circuit boiler differs from a single-circuit boiler in the presence of an additional heat exchanger for preparing hot water (it is sometimes called a DHW heat exchanger).

In addition to the main task - heating the coolant for the heating circuit, the procedure for heating and supplying hot water to consumer appliances is performed . This feature makes the boiler more efficient and in demand.

It is noteworthy that no significant changes are made to the design; an additional flow-type heat exchanger is simply installed in the gap in the straight line between the primary heat exchanger and the three-way valve.

The simplicity and small size of the additions make it possible to use the same housings for both types of units, making production more economical. The cost of the boiler increases only by the price of the additional unit.

Specifications

When choosing a model of the system in question, the technical characteristics must correspond to the level of expected comfort and the amount of heat and hot water used. Since they will vary greatly depending on the area of the room and the activity of using the system. Because some owners visit private houses only for a short period of time, while others live in them permanently.

The number of people living and the presence of pets also greatly influences. Because, in any case, the more people live, the more hot water is used. Therefore, when choosing a model, it is necessary to take into account all the characteristics of the heated object in order to choose the best option.

Device

The main components and parts of double-circuit boilers are:

gas burner and primary heat exchanger combined with it;
gas equipment - supply unit, valve, other elements;
secondary heat exchanger;
three-way valve;
turbocharger fan;
circulation pump;
expansion tank;
control board and self-diagnosis sensors.

Boilers created using traditional “open” technology do not have a turbocharging fan, since their smoke removal occurs according to the principle of natural draft, and the air comes directly from the surrounding atmosphere.

Operating principle

The operation of a double-circuit boiler consists of two streams:

The coolant enters the primary heat exchanger and receives the maximum possible temperature. It is then passed through a secondary heat exchanger, where it transfers some of the resulting energy to prepare hot water. After this, it passes into a three-way valve, receives the desired temperature by mixing some of the return flow, and is discharged into the heating circuit for a new circulation circle;
cold water enters the boiler and is passed through a secondary heat exchanger. After that, it goes to the consumption devices. When the tap opens, water begins to pass through the plate device and heat up in flow mode. The more water is drawn, the lower the water temperature - at high flow rates it does not have time to heat up properly.

The coolant is prepared in the flame of a gas burner. For its operation, air is required, which is supplied by the turbocharger fan. Excess pressure arises, pushing the smoke out through a special coaxial chimney.

The operation of all system components is constantly monitored by self-diagnosis sensors.

They immediately signal the occurrence of failures or malfunctions, the control board places an alert on the display, and in some dangerous situations immediately turns off and locks the boiler.

NOTE!

Non-volatile models are equipped only with mechanical parts. They are much simpler and do not have fans, centrifugal pumps or control units. The functioning of the system occurs on the basis of natural processes of traction and lifting of warm layers of liquid upward.

Requirements for heating systems of country houses

The general rules adopted by SNiP look quite simple; according to the recommendations of experts, the temperature during the heating period should not fall below 12 degrees. When considering heat for a country house, special attention is paid to fire safety measures; they will be different for each type of system.

The best location for devices is considered to be under the window openings, and the wiring itself must meet the standards of operational reliability. For air coolant, I advise installing mechanical ventilation, then the result from heating devices will be as efficient as possible. Propylene glycol for the heating system is not prohibited by the rules; this liquid is excellent for various systems.

Kinds

There are different design options for double-circuit boilers. They can be conditionally united according to specific characteristics.

By installation method:

wall- mounted Gas boilers that are mounted in a hinged manner on strong, preferably load-bearing walls. The installation method implies the absence of massive and heavy parts. Because of this, the power of wall-mounted boilers does not exceed 35-40 kW;
floor . They are installed directly on the floor (or on a stand). There are no restrictions on weight and dimensions, so the power of floor-standing boilers can be much greater - up to 100 kW and higher. Also, floor-standing units can be connected in a cascade (usually up to 4 pieces), which allows you to create a powerful heating unit.

By heat exchanger type:

separate . The design of such boilers has two units - a primary (main) unit in which the coolant is heated, and a secondary unit (usually plate-type, for hot water supply);
bithermic . This design resembles a coaxial pipe in which coolant flows through the outer cavity, and water for hot water flows through the inner cavity. This design significantly changed the specifics of water heating. The temperature has stabilized, there are no noticeable differences in the DHW supply . However, such a heat exchanger is susceptible to the formation of lime deposits. Flushing does not give noticeable results, and replacing a bithermic heat exchanger is too complicated and expensive.

The material for the heat exchanger can be:

stainless steel . Used for units of budget units;
copper . Used in expensive boilers from the most famous manufacturers. They have high performance capabilities and are lightweight, which is important in wall structures;
ductile cast iron . Heat exchangers of this type are found in floor-standing boilers, where massive parts can be used. The qualities of cast iron make it possible to obtain a high heating effect and equalize temperature changes under harsh operating conditions.

By type of combustion chamber:

open (atmospheric) . The burner operates on air that comes directly from the room. Smoke removal occurs naturally, using a stove-type draft. To do this, the boiler must be connected to the central chimney. This method is considered outdated and unstable, since it depends on external causes - gusts of wind, drafts, and other factors;
closed (turbocharged) . The chamber does not communicate with the outside atmosphere, so air is supplied into it using a fan. In this case, excess pressure arises in the chamber, displacing smoke and other combustion gases out. In such designs, a coaxial type chimney is used, the outer pipe of which serves to supply air, and the inner pipe exhausts smoke.

By heat transfer method:

convection _ Conventional heating of a coil with coolant in a burner flame;
condensation _ A two-stage heating of the coolant is carried out, preliminary (with heat obtained from condensation of wet smoke) and main (in the usual way). It is necessary to take into account that full operation of such boilers is possible only in low-temperature heating systems - with heated floors, or in regions with high winter temperatures . The critical temperature difference between inside and outside the room at which the process stops is 20°. In Russia this is impossible even in the southern regions.

IMPORTANT!

When choosing a condensing boiler, you should know exactly the principle of its operation and be confident in the possibility of using it in the existing conditions. Otherwise, the money will be wasted.

Schemes of water heating systems

I consider the issue of the cost of one- and two-pipe types of construction not so fundamental; in the opinion of most people, the first heating system will cost less, but only when it comes to small buildings. The second heating circuit will not be able to function as efficiently as possible without thermostatic valves, and slightly more radiators will need to be installed than in the first option.

Single-pipe wiring: pros and cons

An important positive side will be the length of the circuit and the pipeline, because thanks to this indicator they do not affect each other in any way. The connection is quite simple, and the ability to install the system in multi-storey buildings makes it practical. The main pipe looks quite aesthetically pleasing; it is located parallel to the baseboard.

Among the disadvantages, I can note the mandatory installation of additional equipment due to the serial connection of radiators, otherwise the last point will not be able to properly generate heat. This process will affect cash costs, and the heat exchange area will increase.

Advantages of a two-pipe connection:

Versatility and simplicity.
Maximum concealed pipe placement.
Hydraulic balance.
Possibility to connect many radiators to one coolant.

Do you need a boiler?

A double-circuit boiler is capable of independently preparing hot water and does not require additional devices . This is a common view, and it is generally correct.

However, many users are not satisfied with the DHW supply mode in their homes. This usually happens due to a large number of water taps, numerous families, etc. For these cases, there is a way to connect an external drive as a buffer capacity.

Hot water fills the container and is replenished as needed.

The boiler's DHW supply can be adjusted so that the flow rate is minimal . This will ensure high temperatures and stabilize the supply of hot water to consumers.

Installation features

Installation features include the following:

the entire piping of the water heater itself must be connected not only to the heating system, but also to both water supply lines, that is, to both cold and hot water;
It should be noted that the cold water input is connected to the system from below, and the hot water is discharged from the top of the tank, while the recirculation point is located approximately in the middle of the boiler tank;
the heated coolant must move along the circuit from top to bottom;
It is worth noting that the coolant liquid moves to the upper nozzle, and then returns back into the bosom of the heating line from the lower nozzle of the container. It is this feature that helps increase efficiency, since heat is initially transferred to the warmest layers of the coolant;
it is important to know in what ways you can connect the boiler so that it works correctly, making the most of its resources;
It is for a single-circuit gas boiler with an indirect heating boiler that a sensor is provided that regulates the temperature, and it is installed directly in the tank;
When connecting a boiler to a single-circuit boiler, it is necessary to use a circuit with two circulation pumps. It is important to note that this type can replace the previously discussed three-way sensor circuit;
it is important to know that the connection features also include the separation of flows through which the coolant moves;
due to the way the heating system assembly algorithm is configured, either the water heating system or the circuit where the coolant circulates can take precedence in receiving heat;
The thermostat also regulates the alternating activation of both pumps installed in the tank.

Which company should you choose?

Since a gas boiler is an expensive device that is purchased for a long time, it is better to give preference to appliances from well-known brands.

Companies that specialize in the production of heating equipment provide a guarantee for their devices, and use high-quality materials and modern technologies for their manufacture. In 2021, as an analysis of user reviews showed, boilers from Protherm, Vaillant, Lemax, Baxi and Bosch were recognized as the best. It is these devices that are included in this rating.

How to calculate power?

Calculating boiler power is too complex a task. An unprepared person cannot cope with it . However, there is a simple calculation option that gives an approximate, but quite acceptable result.

Heating 10 m2 of area requires 1 kW of thermal energy. Based on this ratio, you can quickly determine the required boiler power. For example, for a house of 200 sq.m. you need 20 kW of thermal energy.

A unit of either 18 or 24 kW is suitable.

NOTE!

You should not make a large power reserve, since the boiler begins to operate at minimum mode. Frequent starting and stopping of the burner contributes to the rapid failure of components, and scale accumulates in the heat exchanger. The result will be the need for expensive repairs or the purchase of a new boiler.

Reviews

Users who have already purchased the necessary equipment suggest that when choosing a single-circuit gas boiler with an indirect heating boiler, the consumer should pay attention to the following details:

from which manufacturer is this design purchased, because if the plant producing the units is not yet widely represented, then in the event of the need for warranty repairs or other breakdowns, it will be extremely difficult to find a service station or the necessary parts;
and wall-mounted gas installations are also very popular, because there is no need to build a separate room for them, as would happen if you purchased a floor-standing gas boiler;
wall-mounted single-circuit gas boilers are quite easy to install in small rooms, and even in offices where there is no heating, because the body width is only 40-45 cm;
According to reviews, it is necessary to purchase models that come complete with all the fasteners, as well as mounting elements that help you easily install the structure even yourself, without resorting to expensive outside help;
It is worth paying attention to models where the water heating tank starts from 6-7 liters, and it is equipped with a circulation pump;
convenient models with functions clearly displayed on the control panel, that is, you can freely adjust the temperature, control the thermostat, light the burner if necessary, and monitor the readings;
the system must also provide data on its performance;
It is advisable to purchase units that have a self-diagnosis function.

That is, before choosing a particular model, you should study in detail the reviews of consumers who are already using a specific design that has the functions necessary for the owner of the house.

Rating of TOP 5 double-circuit boilers

Let's consider several popular models of double-circuit boilers:

Buderus Logamax U072-12K

When talking about Buderus boilers, it is necessary to keep in mind that today it is a “daughter” of the world-famous Bosh concern. This determines the general attitude of manufacturers towards their products, the level of requirements and quality.

The brand was built for the production of budget gas boilers, since it is unacceptable for Bosh to reduce the price of its products from a reputational point of view.

The Buderus Logamax U072-12K boiler has a power of 12 kW, which allows it to be used for heating rooms up to 120 sq.m.

The unit is equipped with a copper primary and stainless steel secondary heat exchangers. There is multi-stage protection against freezing, overheating and other undesirable situations.

Main characteristics of the boiler:

coolant temperature (min-max) - 40-82°;
temperature in the DHW circuit - 40-65°;
maximum pressure in the heating system - 3 Bar;
pressure in the DHW circuit - 8 Bar;
gas consumption - 2.1 m3/hour;
dimensions - 400x700x299 mm;
weight - 29 kg.

The design of the boiler allows it to withstand pressure fluctuations in the gas or water supply system.

It is possible to switch to liquefied gas, which requires a replacement set of gas burner nozzles.

Bosch Gaz 6000 W WBN 6000- 12 C

Double-circuit gas boiler from a world-famous industrial giant. 12 kW of power allows you to heat 120 m2 of area, while simultaneously providing it with hot water .

The unit is equipped with a copper heat exchanger and a stainless secondary component. The volume of the expansion tank is 8 liters, which is quite enough for a 12 kW device.

Basic parameters of the boiler:

coolant temperature (min-max) - 40-82°;
temperature in the DHW circuit - 35-60°;
maximum pressure in the heating system - 3 Bar;
pressure in the DHW circuit - 10 Bar;
gas consumption - 2.1 m3/hour;
dimensions - 400x700x299 mm;
weight - 28 kg.

Provided that a different set of nozzles is installed, it is possible to reconfigure the boiler to operate on liquefied gas. The permissible butane pressure is 25 mbar, so a reduction reducer is required to connect the cylinder.

Lemax PRIME-V32

The Russian company Lemax is based in Taganrog. The PRIME-V32 boiler is a high-quality double-circuit wall-mounted unit. The design demonstrates high performance.

A separate heat exchanger (primary copper, secondary stainless) ensures efficient heat transfer. The power of the unit is 32 kW, allowing you to heat an area of up to 320 sq.m.

Main characteristics:

coolant temperature (min-max) - 35-85°
temperature in the DHW circuit - 40-65°;
maximum pressure in the heating system - 3 Bar;
pressure in the DHW circuit - 8 Bar;
gas consumption - 2.0 m3/hour;
dimensions - 430x770x340 mm;
weight - 32 kg.

Lemax boilers differ from other domestic heating products in their approach - most boilers are non-volatile and operate on the principle of a gas stove.

The products of engineers from Taganrog demonstrate a European approach and high performance.

Lemax Premium-30B

This is another example of domestic heating units. Premium-30B is a floor-standing double-circuit boiler with a capacity of 30 kW.

It is suitable for rooms up to 300 sq.m. A massive and heavy unit with an atmospheric burner requires a separate room with its own entrance and window opening.

Main characteristics:

coolant temperature (min-max) - 40-90°
temperature in the DHW circuit - 40-70°;
maximum pressure in the heating system - 3 Bar;
pressure in the DHW circuit - 6 Bar;
gas consumption - 3.5 m3/hour;
dimensions - 556x961x470 mm;
weight - 88 kg.

Floor-standing boilers are less often produced in a double-circuit version than wall-mounted ones. They are easier to connect to an external water heater, so single-circuit designs are more often offered .

Switching to liquefied gas is possible, but you will need to install a new set of nozzles and reconfigure the boiler parameters.

Navien SMART TOK 24K

The Korean company Navien focuses on the mass buyer, producing affordable boilers in the budget price range. At the same time, the quality of the units is high enough to successfully compete with European models.

The SMART TOK 24K boiler is designed to heat 240 sq. m., which confirms the power of 24 kW. It is equipped with steel heat exchangers and a closed burner.

Options:

coolant temperature (min-max) - 40-80°
temperature in the DHW circuit - 30-60°;
maximum pressure in the heating system - 3 Bar;
pressure in the DHW circuit - 8 Bar;
gas consumption - 2.79 m3/hour;
dimensions - 440x695x290 mm;
weight - 28 kg.

Many people criticize Korean technology for its high noise level and low strength of some parts.

However, the high demand and demand for boilers from the Korean company show a positive attitude from the majority of buyers.

How to make remote control of the heating of a country house with your own hands

The best option would be a GSM socket; I consider this modern device to be the easiest to install to control the heating system yourself. The unit has a built-in temperature sensor, and a maximum load of 4 kW is enough for small country houses.

All radiators must be connected in series, then the device is inserted into a regular socket, the smart heating temperature sensor is able to independently turn off the created system after heating the room to a given temperature, and the owner can do this from any gadget.