Comparison BAXI Eco-4s 24 F 24 kW vs BAXI Main 5 24 F 24 kW

The maximum area of the building 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 even more so 50-year-old houses. Accordingly, this paragraph is more of a reference nature and does not allow a full assessment of 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; see Heat output for more details. In our case, the heating area is calculated according to the formula "boiler power multiplied by 8", which is approximately equivalent to use in houses that are more than a dozen years 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 maximum electrical power consumed by the boiler during operation. For non-electric models (see Energy source), this power is usually low, as it is required mainly for control circuits and it can be ignored. Regarding electric boilers, it is worth noting that the power consumption in them is most often somewhat higher than the useful one since part of the energy is inevitably dissipated and not used for heating. Accordingly, the ratio of useful and consumed power can be used to evaluate the efficiency of such a boiler.

The minimum operating temperature of the heat medium in the boiler system when operating in heating mode.

The maximum operating temperature of the heat medium in the boiler system when operating in heating mode.

The maximum temperature of domestic hot water supplied by a dual-circuit boiler. For comparison, we note that water begins to be perceived as warm, starting from 40 °C, and in centralized hot water supply systems, the temperature of hot water is usually about 60 °C (and should not exceed 75 °C). Accordingly, even in the most modest models, this figure is about 45 °C, in the vast majority of modern boilers, it is not lower than 50 °C, and in some models, it can even exceed 90 °C.

Also when heated to a given temperature, the temperature difference ("ΔT") may be different — depending on the initial temperature of the cold water. And the performance of the boiler in the DHW mode directly depends on ΔT; see below for performance details.

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 OpenTherm 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 efficiency of the boiler.

For electric models (see "Energy source"), this parameter is calculated as the ratio of net power to consumed; in such models, indicators of 98 – 99% are not uncommon. For other boilers, the efficiency is the ratio of the amount of heat directly transferred to the water to the total heat amount released during combustion. In such devices, the efficiency is lower than in electric ones; for them, a parameter of more than 90% is considered good. An exception is gas condensing boilers (see the relevant paragraph), where the efficiency can even be higher than 100%. There is no violation of the laws of physics here. It is a kind of advertising trick: when calculating the efficiency, an inaccurate method is used that does not take into account the energy spent on the formation of water vapour. Nevertheless, formally everything is correct: the boiler gives out more thermal energy to the water than is released during the combustion of fuel since condensation energy is added to the combustion energy.

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.