One device, but so much benefit! Double-circuit gas boilers for heating a private house: which is better

A double-circuit gas boiler is a heating device that combines both a heating device and a water heater.

If a single-circuit boiler has only one heat exchanger for heating the heating system coolant (HSC), then Double-circuit boilers have two heat exchangers installed.

For the heating medium CO and for the hot water supply system (DHW), as well as a special valve that controls the distribution of boiler power between heating and DHW.

Since in many houses where it is necessary to install, there is no central heating and hot water, a double-circuit gas boiler can be the best option in terms of price, functionality and ease of use.

Choosing a double-circuit gas boiler for heating a private house

To choose the best option for your home it is necessary to understand the operating principle of a double-circuit gas boiler And understand the basic parameters, on which the efficiency and ease of use of the device will depend. Let's consider these characteristics.

How the device works

Common to all dual-circuit systems: the boiler has two heat exchangers, main (heating) And additional (for hot water supply).

The water flow sensor is triggered when the tap is opened, the electromagnetic valve closes the circulation of the coolant in the heating system and directs it to the secondary heat exchanger, where it begins to heat water for hot water supply.

As soon as the tap is closed, the valve switches again, and the boiler continues to operate to heat the building.

Power

When calculating, we use the standard formula: 1 kW of heating power per 10 m² area of ​​heated premises.

Considering that the boiler is double-circuit and the power will be spent not only on heating the building, but also on the DHW system, we will determine the power for DHW. Standard household tap with supply ½ inch has a productivity of the order of 400 l of water per hour or about 6.6 l/minIf there is more than one water intake point in the house (for example, a bathroom and a kitchen), we sum them up.

In the technical characteristics of the boiler we look for maximum flow heating performance.

It should be equal to or greater than the total value you received, in which case the boiler capacity will be sufficient for comfortable use of hot water supply at all points in the house.

In addition, the power for DHW is affected by the difference between the required hot water temperature and the temperature of the incoming cold water. In the boiler data sheet, it is designated as the flow rate at a given ∆t. For example, if you need hot water with t₂=50 °C, and the water coming from the well has t₁=5 °C, then the parameter ∆t = t₂ - t₁ = 45 °C.

Without going into details, we calculate the total boiler power as the power required for heating, plus 30% on top for hot water supply.

Accommodation Features

There are two versions available: for wall and floor mounting. The power of wall-mounted boilers is usually limited 30 kW, but they are very compact and do not require placement in a separate room. Moreover, since this type of heating devices has been produced relatively recently, they use the most modern technologies. However, floor-standing boilers are highly reliable, powerful, and have a long service life.

Photo 1. Double-circuit floor-standing gas boiler. Heating and hot water supply circuits are connected to it.

For the sake of compactness, in wall-mounted units a very small heat exchanger for hot water supply is installed. When using hot water, the entire power of the boiler is instantly redirected to it. If the water quality is poor, the thin tubes of the heat exchanger quickly become clogged and the boiler fails. Therefore, if you choose wall-mounted equipment, pay special attention to the quality of the incoming water.

Type of combustion chamber and its operating principle

There are also two options here: open and closed. In an open chamber, oxygen for gas combustion comes from the room where the boiler is installed, and combustion products are discharged into the chimney. Such a device operates on natural draft, therefore two conditions must be met: ensure good ventilation of the room with the boiler, and also construct a vertical chimney.

Boilers with a closed combustion chamber are used in pairs with a coaxial chimney, through which both air is supplied from the street and combustion products of gas are removed. The draft is maintained forcibly by a fan, so the chimney can be of any configuration. The disadvantage of this type is its higher price.

Energy dependence

Most gas boilers operate only when there is electricity. It is needed for the operation of automation, electric ignition, and circulation pumps.

Usually such boilers are supplied with uninterruptible power supplies (UPS). However, there are energy-independent units. They use dual burner piezo ignition system.

In the event of a power failure, the system switches to a mode with natural circulation of the coolant.

Degree of automation

The devices also differ in the level of automation installed. The simplest are mechanical systems, where ignition is carried out manually by pressing a button with a piezoelectric element, and the thermostat is made on a bimetallic plate. They do not require electricity, but the list of functions is small.

If the boiler is equipped with electronic automation, then everything is limited by the manufacturer's imagination. Advanced electronics not only ensure safe and autonomous operation of the boiler in a given mode, but also allows you to control it remotely, set programs by days of the week, etc.

Ignition type

Distinguish piezo ignition and electric. In the first case, a piezoelectric element is installed in the boiler, generating a spark when the piezoelectric crystal is compressed by pressing a button.

This spark ignites a small pilot light, which then lights the larger main gas burner.

In systems with electric ignition, the spark is created by high-voltage converters on command from the electronics without any effort on the part of the user.

Review of popular models, which one is better to choose

There are many models of gas boilers on the market, the most popular of them are presented below.

Baxi MAIN Four 240 F

A good and very budget option, however, unreliable. With proper handling and understanding of the operating principles, provided you have “straight hands”, it will last a relatively long time, but it is not suitable for “set it and forget it” users.

Photo 2. Gas double-circuit boiler Baxi MAIN Four 240 F. The model is made in a wall-mounted version.

• Combustion chamber: closed.
• Design: wall-mounted.
• Power: 24 kW.
• Minimum power: 9.3 kW.
• Efficiency: 93%.
• DHW temperature: 35—55 °C.
• DHW performance: 9.8 l/min @ Δt=35 °C.
• Weight: 31 kg.
• Price: from 13000 rub.

Neva Lux 7224

Russian boiler from the company BaltGaz. Not bad devices, adapted to Russian conditions, but in case of breakdown it is very difficult to find spare parts, not the best warranty service.

• Combustion chamber: closed.
• Design: wall-mounted.
• Power: 24 kW.
• Minimum power: 8.9 kW.
• Efficiency: 92.5%.
• DHW temperature: 30—60 °C.
• Heating temperature: 30—85 °C.
• DHW performance: 14 l/min @ Δt=25 °C.
• Weight: 34 kg.
• Price: from 34000 rub.

Neva Lux 8624

Russian boiler from the company BaltGaz.

• Combustion chamber: open.
• Design: wall-mounted.
• Power: 24 kW.
• Minimum power: 8.9 kW.
• Efficiency: 92%.
• DHW temperature: 30—60 °C.
• Heating temperature: 30—85 °C.
• DHW performance: 14 l/min @ Δt=25 °C.
• Weight: 34 kg.
• Price: from 36400 rub.

Baxi Eco Four 24

Eco series boilers from Baxi receive mostly positive reviews. It heats up the heating batteries well, and the temperature of hot water from the tap is also stable.

• Combustion chamber: open.
• Design: wall-mounted.
• Power: 24 kW.
• Minimum power: 9.3 kW.
• Efficiency: 91.2%.
• DHW temperature: 35—60 °C.
• DHW performance: 9.4 l/min @ Δt=35 °C.
• Weight: 29 kg.
• Price: from 34000 rub.

Baxi MAIN-5 24 F

Relatively reliable operation, occasional problems are solved by rebooting with a complete power outage.

Photo 3. Gas boiler with two circuits Baxi MAIN-5 24 F. The device has an electronic panel that allows you to control it.

• Combustion chamber: closed.
• Design: wall-mounted.
• Power: 24 kW.
• Minimum power: 9.3 kW.
• Efficiency: 93%.
• DHW temperature: 35—55 °C.
• DHW performance: 9.8 l/min @ Δt=35 °C.
• Weight: 27 kg.
• Price: from 28900 rub.

Bosch Gaz 6000 W WBN 6000-24 C

A Russian-made boiler, specially adapted by Bosch for our conditions: works at any voltage (165-230 V) and gas pressure drops (10.5—16 bar). Works on both liquefied and natural gas.

• Combustion chamber: closed.
• Design: wall-mounted.
• Power: 24 kW.
• Minimum power: 7.2 kW.
• Efficiency: 90%.
• DHW temperature: 35—60 °C.
• Heating temperature: 40—82 °C.
• DHW performance: 6.8 l/min @ Δt=50 °C.
• Weight: 32 kg.
• Price: from 29000 rub.

Oasis BM-16

A good unit from a Chinese manufacturer. According to reviews, it works well for heating and satisfactorily for hot water supply. It will do with not very high consumption.

• Combustion chamber: closed.
• Design: wall-mounted.
• Power: 16 kW.
• Efficiency: 90%.
• DHW temperature: 36—60 °C.
• Heating temperature: 30—80 °C.
• DHW performance: 8 l/min @ Δt=25 °C.
• Weight: 34 kg.
• Price: from 27000 rub.

Navien DELUXE 24K

Durable, very comfortable and ergonomic control. The unit is of Korean manufacture and is well suited for use in Russia and has a moderate price.

• Combustion chamber: closed.
• Design: wall-mounted.
• Power: 24 kW.
• Minimum power: 9 kW.
• Efficiency: 90.5%.
• DHW temperature: 30—60 °C.
• Heating temperature: 40—80 °C.
• DHW performance: 13.8 l/min @ Δt=25 °C.
• Weight: 28 kg.
• Price: from 27500 rub.

Leberg Flamme 24 ASD

Boiler with very high efficiency And good performance for hot water for reasonable prices.

• Combustion chamber: closed.
• Design: wall-mounted.
• Power: 20 kW.
• Minimum power: 7.2 kW.
• Efficiency: 96.1%.
• DHW temperature: 35—65 °C.
• Heating temperature: 30—85 °C.
• DHW performance: 8.3 l/min @ Δt=30 °C.
• Weight: 38 kg.
• Price: from 32700 rub.

Vaillant turboTEC pro VUW 242 5-3

According to user reviews the most reliable and durable option among the models in the review.

Photo 4. Double-circuit gas boiler from the manufacturer Vaillant, model turboTEC pro VUW 242/5-3. Wall-mounted device.

• Combustion chamber: closed.
• Design: wall-mounted.
• Power: 24 kW.
• Minimum power: 8 kW.
• Efficiency: 91%.
• DHW temperature: 35—65 °C.
• Heating temperature: 30—85 °C.
• DHW performance: 11.5 l/min @ Δt=30 °C.
• Weight: 40 kg.
• Price: from 47000 rub.

Useful video

Watch the video to learn how to choose the right gas boiler.

The best choice for your home

Unfortunately, the choice of a gas double-circuit boiler cannot be reduced only to efficiency. All the units we have reviewed have Efficiency >90% in a wide range of powers, so you should pay attention to other parameters.

Boilers of Russian production NEVA Lux do not show the best results in terms of reliability. The same can be said about the budget line of the Italian manufacturer Baxi.

The principle at work here is: “expensive and for a long time, or cheap, but with constant repairs or replacement.”

If we talk about the most economical option price/efficiency/DHW consumption, then the recommended model Leberg Flamme 24 ASD. It has the highest efficiency - 96.1% — of the units considered, with a relatively low price 33,000 RUB