Comparison BAXI Duo-Tec Compact 28 28 kW vs BAXI LUNA Duo-tec 28 28 kW

A very conditional parameter that slightly characterizes the purpose based on the size of the room. And depending on the height of the ceilings, layout, building design and equipment, actual values may differ significantly. However, this item represents the maximum recommended area of the room that the boiler can effectively heat. However, it is worth considering that different buildings have different thermal insulation properties and modern buildings are much “warmer” than 30-year-old and especially 50-year-old houses. Accordingly, this item is more of a reference nature and does not allow us to fully assess the actual heated area. There is a formula by which you can derive the maximum heating area, knowing the useful power of the boiler and the climatic conditions in which it will be used; For more information on this, see "Useful Power". In our case, the heating area is calculated using the formula “boiler power multiplied by 8”, which is approximately equivalent to use in houses that are several decades old.

The minimum heat output at which the heating boiler can operate in constant mode. Operation at minimum power allows you to reduce the number of on-and-off cycles that adversely affect the durability of heating boilers.

The outdoor temperature sensor allows you to monitor the outdoor weather conditions and automatically adjust the operation of the boiler to them — increase the heating power when the outside temperature drops and decrease it when it rises.

The control bus with which the boiler is compatible.

The control bus is a communication channel through which control and controlled devices can exchange data. Support for such a channel greatly simplifies the connection of thermostats and other control automation. It is enough that such devices are compatible with the same bus as the boiler. In addition, many types of tyres allow you to create very extensive monitoring and control systems and easily integrate various devices into them, including heating boilers.

In modern heating technology, the most popular tyres are OpenTherm, eBus, Bus BridgeNet and EMS. Here are their key features:

— OpenTherm. A fairly simple standard with modest functionality: it allows only a direct connection between the control and the controlled device and is not designed to create extensive systems. On the other hand, this bus has quite advanced capabilities for controlling heaters: in particular, it allows you to control the temperature not just by turning the boiler on/off, but by changing the power of the gas burner. This mode of operation contributes to saving fuel/energy, as well as reduces wear and increases the life of the heater; and in many cases, a system of two devices (boiler and thermostat) is quite enough for effective heating control. At the same time, the OpenThe...rm standard is simple and inexpensive to implement, which makes it extremely popular in modern boilers. For several reasons, it is mainly used in gas models.

— eBUS. A control bus that has some pretty impressive features. Allows you to combine up to 25 control and 228 controlled devices in one system, with a data transmission distance between individual components up to 1 km. At the same time, eBUS is an open standard, its implementation (at least within the framework of the main functions) is freely available to everyone. And although nowadays eBUS support can be found mainly in Protherm and Vaillant equipment. However, in boilers, this is the second most popular type of control bus, after OpenTherm. It is mainly due to slightly higher cost, while advanced eBUS capabilities are not needed as often.

— Bus BridgeNet. Hotpoint-Ariston proprietary development, used exclusively in boilers of this brand. One of the advantages is a high degree of automation: the user only needs to set the temperature parameters (and for different zones, you can choose custom options) and, if desired, a weekly programme, the rest of the necessary calculations and adjustments will be carried out by the system. However, such features are available only in special control devices such as temperature controllers; in boilers, Bus BridgeNet support usually means only compatibility with such automation.

— EMS. A control bus used primarily in Bosch and Buderus equipment. In general, it is characterized by wide functionality, a high degree of automation and the ability to create extensive control systems. However, note that nowadays you can find both the original EMS and the modified EMS Plus, and these standards are not initially compatible with each other (although support for both of them may well be provided in some devices). So the specific version of the EMS bus should be specified separately. We note that in Bosch devices there is mainly an original version, and in Buderus devices — EMS Plus (although exceptions are possible there and there).

The diameter of the pipe through which combustion products are discharged from the combustion chamber.

In boilers with a closed combustion chamber often used the coaxial flue, consisting of two pipes nested one inside the other. At the same time, products of combustion are discharged from the combustion chamber through the inner pipe, and the air is supplied through the gap between the inner and outer ones. For such flues, the diameter is usually shown in the form of two numbers — the diameter of the inner and outer pipes, respectively. The most popular values are 60/100, 80/80 and 80/125. Non-coaxial flues can be 100, 110, 125, 130, 140, 150, 160, 180 and 200 mm.

It is the optimum gas pressure supplied to the inlet of the boiler system. Most often indicated for natural gas and is about 15-20 mbar. This parameter must match the specs of the gas supply system. However, the pressure in the latter may be higher, which may require the installation of a special gas regulator.

The capacity of the expansion tank supplied with the boiler.

The expansion tank is designed to drain excess water from the heating system when the total volume of liquid increases as a result of heating. It consists of two parts connected by a flexible membrane: in one, hermetically closed, there is air under pressure; in the other, excess water enters, compressing the membrane. In this way, a catastrophic increase in pressure in the heating circuit is avoided. The optimal volume of the expansion tank depends on several system parameters, primarily the volume and composition of the coolant; detailed recommendations for calculations can be found in special sources.

The diameter of the pipe for connecting the gas supply pipe in the boiler with the corresponding type of power supply (see "Energy source").

Diameters are indicated in inches. In some cases, it is allowed to connect a pipe of a different diameter through an adapter, but the best option is still a match in size. The most common options are 1/2" and 3/4".

— Gas pressure drop. This protection system ensures that the boiler is switched off in the event of a critical drop in gas pressure, insufficient for the normal functioning of the burner. In the event of such a fall, the valve that supplies gas to the burner is closed and blocked. After the restoration of gas pressure, it also remains closed; it is necessary to open it and resume the gas supply manually.

— Water overheating. A temperature sensor automatically turns off the boiler when the temperature of the water in the system is critically exceeded.

— Flame loss. Flame loss protection is based on a sensor that monitors the combustion of gas and automatically stops its supply. It prevents the room from filling with gas and the possible tragic consequences of this.

— Draft control. In boilers with an open combustion chamber, to maintain normal conditions in the room where such a boiler is installed, constant removal of products of combustion into the atmosphere is necessary. The lack of a normal draft in the chimney can lead to the accumulation of combustion products in the room. The draft protection system prevents this by automatically turning off the boiler when it detects the release of combustion products outside the chimney.

— Power outage. Most modern boilers h...ave an electronic control system; in addition, many structural elements (pumps, valves, fans, etc.) are also powered by electricity. Thus, a power outage during the operation of the boiler will inevitably lead to an abnormal mode of operation, which is fraught with breakdowns and even accidents. To prevent such cases, a power outage protection system is installed, which completely stops the operation of the boiler in the event of a power outage. When the power supply is restored, the boiler needs to be restarted manually.

— Water circulation failure. This protection system controls the normal movement of the water through the heating circuit. Water circulation failure can lead to overheating of some elements of the boiler and damage to it. To avoid this, if the circulation is disturbed, the system turns off the pump and shuts off the gas supply to the burner.

— Frost protection. A system that controls the temperature in the heating circuit. Freezing of the liquid in the circuit disrupts the normal operation of the heating, which may require heating of the pipes and lead to system damage. To avoid this, when the water temperature drops below 5 °C, the burner is ignited, the circulation pump is activated, and the circuit warms up to a temperature of about 35 °C — thus preventing the formation of ice in the pipes.