Heating area
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.
Condensing
Boilers generate additional heat by condensing water vapour from combustion products. In such units, the combustion gases, before entering the flue, are passed through an additional heat exchanger, in which they are cooled, and the water vapour condenses and transfers thermal energy to the coolant. It allows you to increase the efficiency by 10 – 15% compared to boilers of the classical design — up to the fact that in many similar models, the efficiency exceeds 100% (for more details, see "Efficiency").
The condensation principle of operation is most often found in gas models (see "Power source"); however, solid and liquid fuel boilers with this feature are also produced.
Built-in water heater tank
The presence of a built-in water heater tank in the boiler — a storage tank for water used in the hot water supply system. For obvious reasons, this feature is found exclusively in dual-circuit boilers (see "Type"). It provides several advantages over a flow-through design (when the boiler heats water directly in the process of moving through the heat exchanger). Firstly, in the tank, you can constantly keep a supply of ready hot water, and use it even in case of interruptions in the water supply. Secondly, the temperature of the dispensed water is constant, while in instant heating devices fluctuations are possible when the water flow rate changes. Thirdly, the efficiency of work does not depend on the pressure in the water supply. On the other hand, this feature significantly affects the dimensions, weight and price of the boiler.
DHW tank volume
The volume of the DHW tank provided in the boiler.
In this case, we can talk about both built-in tanks (see above), and a separate device supplied in the kit. The first option is found in dual-circuit boilers, and the second is in single-circuit ones (see "Type"). Anyway, the larger the tank, the more water you can keep in reserve, but the larger and heavier the entire boiler or separate tank is. There are special methods that allow you to calculate the optimal tank capacity depending on the number and type of water points, the number of users, etc. Such methods are described in detail in special sources, but we note here that the average value is considered to be about 80 – 100 litres. It is enough for regular use by a family of 3 – 4 people.
Heat output
It is the maximum useful power of the boiler.
The ability of the device to heat a room of a particular area directly depends on this parameter; by power, you can approximately determine the heating area, if this parameter is not indicated in the specs. The most general rule says that for a dwelling with a ceiling height of 2.5 – 3 m, at least 100 W of heat power is needed to heat 1 m2 of area. There are also more detailed calculation methods that take into account specific factors: the climatic zone, heat gain from the outside, design features of the heating system, etc.; they are described in detail in special sources. Also note that in dual-circuit boilers (see "Type"), part of the heat generated is used to heat water for the hot water supply; this must be taken into account when evaluating the output power.
It is believed that boilers with a power of more than 30 kW must be installed in separate rooms (boiler rooms).
Power consumption
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.
Rated current
The current consumed by the electric boiler (see "Power source") during normal operation.
This parameter directly depends on the power. It is required primarily for organizing the connection: wiring and automation must safely deal with the current consumed by the unit.
Coolant min. T
The minimum operating temperature of the heat medium in the boiler system when operating in heating mode.
Coolant max. T
The maximum operating temperature of the heat medium in the boiler system when operating in heating mode.
