Double-circuit heating boilers: how to choose

Double-circuit boilers are increasingly being chosen as a more economical alternative to simple single-circuit systems. Heating the coolant and maintaining the required temperature in the hot water system helps conserve fuel, reduce maintenance costs, and even monitor the operation of the entire equipment. But to ensure long-lasting and trouble-free operation of such a boiler, it's important to choose the right type and find a high-quality design.

Device types

Gas boilers have become a popular choice for dual-circuit boilers. They are fuel-efficient, reliable, and highly efficient. They can be installed in any type of home, are compact, and affordably priced. These systems can operate on:

• liquid fuel;
• solid materials;
• electricity.

Liquid fuel is more efficient than solid fuel. It's easier to store and transport, and the heating equipment itself wears out less. Liquid fuel units generate heat through a large, built-in coil. This is the central element of these units. An internal boiler is another characteristic of this type of dual-circuit boiler. It doesn't take up space, which is important.

Solid fuel dual-circuit boilers are simpler in design. They rarely have secondary heat sources; hot water for domestic hot water is heated using primary heat. This makes them significantly cheaper and easier to repair. However, solid fuel is less environmentally friendly, and the boiler will require regular maintenance and cleaning. Achieving a consistent heating temperature is also difficult. Heavy solid fuels burn gradually, so temperature fluctuations are inevitable. More modern dual-circuit boilers with integrated pellet systems do not have this drawback. In these boilers, the energy source is automatically loaded by a built-in mechanism, simplifying operation for the owner.

An important characteristic of a dual-circuit boiler is the heat exchanger type. It determines heating stability and overall service life. There are three types:

• primary;
• bithermal;
• secondary.

Their combination determines efficiency. The primary heat exchanger is very similar to a conventional radiator, such as those found in apartments or cars. The design is the same: a central pipe and elements that transfer heat to the radiator. Heating occurs directly by the flame, which reduces the system's service life. However, each burnt-out element can be replaced individually, reducing repair and maintenance costs.

Bithermal systems are more complex. A second pipe, designed for hot water supply, is installed inside the first pipe, which serves as the primary radiator. This heat distribution ensures uniform heating and temperature stability. The pipe is more rigid and less susceptible to deformation during operation. By distributing heat across two systems simultaneously, fuel savings are achieved; however, replacement costs for this component will be higher during repairs.

The secondary elements are heated solely by the coolant circulating in the system. They are not exposed to open flame, so wear occurs slowly. Hundreds of thin plates are installed inside the main body, which evenly distribute energy and can accumulate it, gradually releasing it. Since there is no need to restrict the flow of hot water, owners can use several faucets simultaneously without losing pressure or reducing the overall temperature.

How to choose the right one

In addition to the design differences already described, dual-circuit systems differ in power, additional options, and installation type. All of this must be taken into account when selecting a boiler, as any existing deficiencies cannot be compensated for later. Determining the power is crucial, as it is the primary parameter. The required value can be calculated using a standard formula. Calculate the total area of ​​the heated rooms and then divide by 10. This will yield the required kW. Keep in mind that this calculation is valid for rooms with ceilings at least three meters high. To ensure the equipment can handle extreme loads and operate under adverse conditions, add another 30 percent to this figure. This will ensure a longer service life and ideal operation of the boiler without reaching its limits.

Since a dual-circuit boiler must supply domestic hot water, it's important to evaluate the heating rate parameter. It's expressed in liters and degrees per minute. This indicates how many liters of water will be heated in standard mode by the specified number of degrees per minute. For example, if the input temperature is +2 degrees, a boiler with a heating rate of 11/35 will output 11 liters of water at a temperature of 37 degrees. A standard calculation assumes this is enough for two consumers in a residential building.

A boiler can be wall-mounted or floor-standing. The former is more popular because it doesn't require a separate room and is compact yet efficient. Most dual-circuit boilers are offered in this configuration. Floor-mounted units offer greater heating power and a larger capacity for a single load of any fuel. This makes them a good choice for a large home or a small utility room.

A key additional option is the autonomous safety system. It ensures that the equipment will shut down if there is a lack of coolant or liquid, or if there are sudden pressure or temperature surges. Shutdown occurs if draft weakens or the burner goes out. A similar feature is self-diagnostics. In addition to switching valves and relays, the system can turn on pumps and briefly increase power to prevent jamming after periods of inactivity or operation at minimum power levels.

Self-regulating flame power depending on climate changes or a schedule is also a useful feature. This minimizes manual adjustments while simultaneously saving fuel. However, for many buyers, price is a key consideration. Top-of-the-line models with an expanded feature list cost between 60,000 and 80,000 rubles. These are the most powerful versions, often floor-standing, requiring an additional electrical connection. Budget-friendly gas models can be purchased starting at 30,000 rubles. The simplest solid-fuel models, which do not have a secondary radiator, are available starting at 15,000 rubles. However, they require manual adjustments and regular maintenance, and are also low-power.

When choosing a dual-circuit boiler, it's important to evaluate all parameters. Heating power, temperature control, and safety are all important. Choosing an expensive model with bithermic heaters can provide the greatest comfort, but models with primary elements will also last a long time with proper maintenance. Dual-circuit boilers are a good solution for saving space and money. They are suitable for owners of small apartments and residents of country houses.