How to choose a gas wall-mounted double-circuit boiler: what to look at + what the market offers

Alexey Dedyulin
Checked by a specialist: Alexey Dedyulin
Author: Tatyana Zakharova
Last update: July 2019

You can achieve some independence from utilities if you install equipment such as a gas wall-mounted double-circuit boiler that solves the problems of heating and providing a home with an autonomously functioning hot water system.

In the article we presented, characteristics are given that should be paid attention to when choosing an aggregate. We have described in detail the device and design features of gas dual-circuit equipment. In order to facilitate the selection, they listed the leading manufacturers in the segment.

Connection scheme 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 paperwork and approvals in several instances, the installation of gas boilers justifies itself. A correctly selected model will be able to serve both the heating system and supply sanitary water.

The boiler is installed in a convenient place for maintenance. With proven in practice wiring diagrams a dual-circuit gas unit will be introduced by our recommended article. It is necessary to ensure a safe, in-line installation of the gas pipe and bring the chimney out to transport combustion products.

Connection diagram of a wall-mounted double-circuit boiler
Connection diagram of a wall-mounted double-circuit boiler. Yellow line - natural gas supply, blue - hot 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 draw-off, the main of which are a shower, bathtub, sink in the kitchen.

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

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

An alternative to installing a dual-circuit model is to install a set of 1-circuit boiler + BKN, where indirect heating boiler serves the hot water supply system. This scheme is good in that taps always have hot water of the right temperature.

Disadvantages of a kit with a boiler
The disadvantage of installing a boiler is easily understood by the owners of houses and apartments with a deficit 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 dual-circuit models, the heating system and the hot water supply 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 heat carrier.

Advantages of wall-mounted double-circuit boilers

Saving space in a cramped apartment is just one advantage of boilers with two circuits (DC). There are a number of advantages due to which it is wall-mounted recreation centers that are chosen as the main equipment for heating water and organizing domestic autonomous systems.

Here are a few reasons to purchase a 2-circuit wall model:

  • this equipment, the most equipped for heating water and its further distribution, not requiring the connection of additional devices;
  • The recreation center can be installed in the hallway, equipped with windows or a ventilation vent, or in the kitchen; it does not require a separate room;
  • due to their compact size, the boilers are mounted in niches or corners, masked in kitchen cabinets;
  • automatic equipment allows you to maintain the required water temperature, which does not depend on pressure or temperature fluctuations of the air;
  • modern models are highly efficient and economical;
  • one of the installation conditions in a residential building (apartment) is satisfied - a low, comfortable noise level for residents;
  • the cost of household models can be called moderate, the same applies to service.

For wall modifications with a closed combustion chamber, a simplified version of the chimney is equipped: instead of a vertical one passing through the roof, equip coaxial optionbrought out through a nearby wall.

In apartment buildings, the smoke channel is constructed in the form of a curved elbow from modular elements or corrugations and is connected to a public chimney.

What to look for when choosing equipment?

Depending on the requirements for the equipment, the selection criteria may differ, but in any case it is necessary to understand the technical characteristics, functionality and even such seemingly small things as the exact dimensions.

Boiler Model Requirements
A correctly selected model is one that simultaneously provides the house with the necessary amount of hot water, requires minimal intervention in the work process and fits into the interior design

First, consider the main technical nuances.

Thermal Power and Performance

The main function of a gas boiler is to increase the temperature of water for domestic hot water and heating, so the power parameters must be considered first. They can be found in the technical passport of the device. To find out if the boiler is suitable for power in your home / apartment, you need to make simple calculations.

It is generally accepted that for every 10 m² of serviced space, 1 kW is needed for normal heating. But these are the average figures applied to housing with good thermal insulation. If we take into account climatic features and the need for heating water for domestic hot water, we can still increase the result by 35-40 percent.

Power parameters
Power is a variable value, therefore, in the technical documentation most often you can find the min and max value, for example 10 kW / 24 kW

The more powerful the equipment, the more productive it is.The performance indicated in the data sheet makes it clear how many liters of water are heated in 1 minute to the desired temperature.

2 parameters are given - for a temperature of 25 ° C and 35 ° C. Some people mistakenly take these indicators for the outlet water temperature, but this is not so. This is the difference between the inlet temperature and the already heated water.

Suppose that the coolant at the inlet has a temperature of 10 ° C; therefore, at 35 ° C, water reaches 45 ° C. At 25 ° C, the water heats faster, therefore, the heating rate is higher.

If at 25 ° C the productivity is 13 l / min, then at 35 ° C it will be about 9 l / min. Of course, the indicated values ​​will be more accurate if the water pressure and gas pressure comply with the standards that the manufacturer took into account when testing.

Which heat exchanger is better?

The heat exchanger is designed to transfer heat from hot gases (combustion products) to a coolant distributed over two systems. The choice is faced by two types of elements: a pair of separate (primary + secondary) and bithermic.

In devices with separate heat exchangers, the primary one looks like a pipe with plates and is located above the gas burners, and the second one looks like several wide plates assembled together and having 4 pipes for connecting instead of 2. The first is responsible for the heating system, the second is for heating the water for hot water.

Scheme of work of separate heat exchangers
Scheme of operation of separate heat exchangers in the mode of heating water for the domestic hot water system. Above the gas burner (1) and igniter (2), a primary heat exchanger (3) is located. The secondary heat exchanger (4) is located below and connected to a three-way valve (7)

If you use a hot water tap, the flow sensor (6) will work, and water under the action of the circulation pump (5) will flow to the primary heat exchanger, but already along the DHW circuit.

The second variety - the bithermic heat exchanger - is different in that it serves both circuits: both hot water and heating.

It has a special pipe design, in which water for the DHW circuit moves along the internal channel, and the coolant for heating - on the external. Advantages of the bithermic heat exchanger: space saving inside the case, simplified boiler design, lower price.

However, when choosing, they are more likely to buy devices with separate heat exchangers for the following reasons:

  • elements are less likely to fail due to the formation of scale and sediment;
  • primary heat exchanger easier to clean and rinse;
  • the boiler can be repaired in parts;
  • there is no risk of burns due to too hot water (the secondary heats only up to 60 ° C).

If there is a choice between expensive models, we suggest that you consider the offers of the condensation type, which are economical and significantly more powerful.

Condensing boiler design
The scheme of the condensing boiler. The energy generated due to the deposition of water vapor on the walls of the pipes serves to heat the coolant. The resulting condensate is discharged into the sewer

The cost of condensing devices starts from 100 thousand rubles. An example is the eco range of the German manufacturer Vaillant.

What are the combustion chambers?

The design of the chimney and ventilation depends on the design of the combustion chamber, so it must also be taken into account. The choice is between two types: open and closed, which differ fundamentally.

An open combustion chamber is located above the burner, under the hood, and is connected to a vertically directed chimney. Combustion air is taken directly from the room (kitchen, hallway, boiler room).

Scheme of closed and open combustion chambers
For units with open chambers, more stringent requirements are imposed: a separate vertical chimney is required, the organization of sufficient air flow and forced ventilation

In a closed combustion chamber, air passes through a channel of a coaxial chimney, through it the gases from the burner are led out. Natural draft does not matter, since a centrifugal fan is used to remove combustion products.

Closed-chamber devices are preferred, although they are more expensive. For them, there is no need to equip a separate chimney, in addition, they have a higher efficiency. Models with an open camera can come in handy for replacing old devices if the installation site is already equipped with good ventilation and a vertical chimney.

Other important selection options

In addition to the listed design features, which affect both the productivity and the cost of the equipment, there are a number of functions that simplify the management and maintenance of the gas double-circuit boiler.

When buying, it is also important to clarify the dimensions of the device itself and the diameter of the required chimney in order to install the boiler in the home, focusing on fire safety standards.

How to correctly choose a dual-circuit boiler, given the technical characteristics, is described in article, the content of which is devoted to this difficult issue.

Overview of gas boiler manufacturers

In countries where autonomous gas heating actively used, the market is filled with products of various companies. The competition is so high that enterprises that do not withstand it due to the poor quality of the goods quickly leave the race.

Consider best manufacturers offerswhich are popular and are of excellent quality.

Boilers of the Italian company BAXI

BAXI was founded a little less than a century ago - in 1924. Today it is part of the BDR Thermea holding and specializes in the production of wall mounted gas equipment. The well-known line of boilers ECO, MAIN, NUVOLA, LUNA have established themselves as reliable and impeccably functioning equipment.

Gas boiler BAXI
BAXI brand devices are adapted to the conditions of the country to which they are exported. All models feature a classic design and convenient control system.

Owners of housing with a deficit of free space for the installation of a gas boiler will be interested in models of the ECO Four series. These are ultra-compact devices with a height of only 73 cm and a width of 40 cm. Power is limited to 24 kW, but it is enough to heat a 200 m² house.

Among the presented models are single-circuit and double-circuit, with different types of combustion chambers. A required element is an LCD display that displays important parameters.

German quality thermal technology Bosch

Bosch, which arose the year before last, is known in many industrial fields, including the manufacture of gas heating boilers for domestic use. Double-circuit wall devices, which are available in many parts of the world, are highly technological, compact and easy to control.

Double-circuit boiler BOSCH GAZ 6000
A popular model among users is a compact dual-circuit boiler with a BOSCH GAZ 6000 wall-mounted boiler.The boilers are adapted for use in Russia and are produced in two places - in the city of Engels (RF) and in Turkey

Let's consider in more detail how good the 6000 series boilers are:

The German manufacturer pays great attention to the compactness of its devices and is working on the release of economical models. Novelties of the condensation type are encouraging, allowing to increase the efficiency due to the use of condensate.

Korean gas equipment Navien

We can say that the Korean company Navien is slowly but surely conquering the whole world. Having begun production of gas heating devices in 1978, it has been supplying equipment to more than 30 countries.

The Asian manufacturer is known for developing environmentally friendly technologies and caring for the environment. Part of the profits from sales goes to our own environmental fund and to warm the housing for the poor.

Korean boiler Navien
Gas wall models of the PRIME, DELUXE, ATMO series are popular. All devices are equipped with frost protection and devices that control operation at low gas or water pressure in the pipelines

A bonus for lovers of comfort is a convenient D / U remote control with an LCD display, with which you can adjust the temperature of the water in the hot water supply, set the fuel economy mode.

In addition to the listed manufacturers, it is worth paying attention to wall modifications of the Italian brands Hermann, Beretta, Weller, Feroli, as well as Chaffoteaux (France), Airfel and Demarad (Turkey), Protherm (Czech Republic), Aton (Ukraine), Gazlux and NEVA Lux (Russia )

The rules for installing and connecting wall-mounted gas boilers are given in next article, the contents of which we advise you to read.

Conclusions and useful video on the topic

You can learn about the design features, as well as the nuances of the installation and use of gas dual-circuit equipment with wall mounts, from the videos presented.

Video # 1. User feedback on the NAVIEN 24:

Video # 2. About the technical specifications of Protherm Lynx 24:

Video # 3. Comparative characteristics of 1- and 2-circuit boilers:

When choosing a gas wall-mounted boiler, you need to focus not on the appearance, which is identical for many models, but on the technical capabilities of the models. It is important to take into account both the area of ​​the home and the pressure in the gas main and the HVS network.

Even new models need care, so it’s worthwhile to clarify the presence of a workshop capable of servicing.

Tell us about how you bought a wall-mounted gas unit for installation in your house / apartment. Share what your choice was argued for. Please write comments in the block below, ask questions, post a photo on the topic of the article.

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Visitors Comments
  1. Dmitry

    I installed a Westen double-circuit boiler in my apartment located on the ground floor 8-9 years ago. Compact in size, hidden in a closet, the chimney opens into a common wentshacht. Enough for heating in a three-ruble note and underfloor heating in the kitchen located above the basement. Over the years of operation, a block burned out that regulates the shutdown of the boiler if there is no water. It happens that the water pressure drops. In general, a good thing, in our city there is no centralized hot water supply, and it is always warm and hot water, I recommend to put it to everyone who has the opportunity.

  2. Kristina

    In our house there is also a double-circuit boiler. We stopped at the wall Ferolli, with a closed combustion chamber. Installed and forgot, no problems. Use is convenient. The water temperature can be easily adjusted. They immediately concluded a contract with the company for 3 years. Once a year they will come and clean it. The main thing is that ventilation be with normal traction.

  3. Novel

    In 2012, they purchased the Baxi Mainfour 24 with an open combustion chamber. It has been working for the 7th year and there was only one problem with it. A sensor that controls the heating of hot water has broken. There was one temperature on the display, but in real life it was almost boiling water. I replaced the sensor in 2015. Everything is good at the moment. Gas consumes little. We have a wooden house, 50 sq.m., and so in the winter months it takes only 270-280 cubic meters of gas. Very economical and warm in the house, 25-26 degrees.

  4. Bogdan

    It is amazing how large the selection of gas boilers is. And the main thing about everyone, at least someone will write something bad. I thought about Ferroli, but they write that now the Chinese are collecting them and the quality has accordingly fallen. I will probably take Westen Quasar.