Comparison Bosch Therm 4000 O WR 10-2 P vs Beretta Idrabagno 11

This parameter characterizes the efficiency of electricity consumption by the water heater. Classes are indicated by latin letters from A to G (A, B, C, D), where A is the most energy efficient device.

Rated power of the heat exchanger installed in the gas or indirect heater (see "Water heater type"), in other words, the amount of heat that can be transferred to the heated water through the heat exchanger.

This parameter is directly related to the performance of the water heater: high performance inevitably requires appropriate power. At the same time, the power of the heat exchanger is selected in such a way as to provide the necessary operating parameters (primarily performance and temperature). So when choosing a water heater, you should focus primarily on these parameters. Data on the power of the heat exchanger may be needed for some specific calculations — for example, assessing the compatibility of the heater with a boiler or solar collector: an external heat source must have no less thermal power than the heat exchanger, otherwise, it will be impossible to achieve the claimed performance.

It is also worth considering that the actual power of the heat exchanger depends on the temperature of the coolant flowing through it. In the characteristics of the water heater, usually, the power is given for the maximum allowable operating temperature; if the coolant is cooler, then the actual power will be lower.

The highest water temperature provided by the device. The standard temperature of hot water in the water supply is 60 °C, and this value is actually the minimum for modern water heaters: models with more modest rates (usually from 40 °C) are extremely rare. But higher values can be found much more often: for example, water heaters of 75 °C and 80 °C are very popular, and in the most powerful models in this regard, the temperature can reach 95 °C and even higher.

On the one hand, strong heating requires appropriate power (which is especially noticeable in the case of instant electric heaters). On the other hand, the higher the temperature of hot water, the less it is needed for a comfortable outlet temperature, after mixing with cold water; this reduces the consumption of heated water, which is especially important for storage boilers. In addition, many models have thermostats (see "Features").

Also, note that heating to operating values may involve different ΔT (degree of temperature change) — depending on the initial temperature of the cold water. The actual performance of the heater directly depends on ΔT; this moment is described in more detail below, in the paragraphs devoted to performance at different ΔT.

Water heater performance when heating water by approximately 25 °C above the initial temperature.

Performance is the maximum amount of hot water the unit can produce in a minute. It depends not only on the power of the heater as such, but also on how much water needs to be heated: the higher the temperature difference ΔT between cold and heated water, the more energy is required for heating and the smaller the volume of water with which the unit can handle in this mode. Therefore, the performance of water heaters must be indicated for specific options ΔT — namely 25 °C, 40 °C and/or 50 °C. And it is worth choosing according to this indicator taking into account the real needs for hot water: exactly how much and what temperature is needed for a particular situation. Methods of such calculations can be found in special sources.

Recall that water begins to be felt by a person as warm somewhere from 40 °C, as hot — somewhere from 50 °C, and the temperature of hot water in central water supply systems (according to official standards) is at least 60 °C. Thus, at Δt~25°C, for heating to at least the same 40°C, the initial water temperature must be at least 15°C (15+25=40°C). This is a rather high value — for example, in a centralized water supply system, cold water reaches 15 °C, except in summer, when the water pipes warm up noticeably; the same applies to water supplied from wells. So in the “Δt ~ 25 °C” mode, modern water heaters work quite rarely — eithe...r if the initial water temperature is high enough, or if it does not need to be heated much. Most often, the degree of heating is much higher, and the performance is lower. Nevertheless, data for a given degree of heating is still often given in the characteristics — including for advertising purposes, since with a low ΔT, the performance figures are quite impressive. In addition, this information can be useful in fact — for the situations mentioned above, when heating by 25 °C is quite enough.

Flue diameter for which the gas water heater is designed (see "Energy source").

This parameter is useful primarily for the selection and installation of a flue for a specific device. At the same time, it is worth remembering that the design of the duct differs depending on the type of combustion chamber (see above). So, for an open chamber, an ordinary pipe is used; in such cases, one diameter is indicated in the characteristics. But closed (turbocharged) combustion chambers are usually made under the so-called coaxial flue — a channel of the "pipe in pipe" type, where combustion products are brought out through the inner pipe, and the air necessary for fuel combustion is taken from the outside through the outer pipe. For such chimneys, two diameters are indicated for each of the pipes.

It is the amount of gas a device consumes.

The weight of the device, excluding the water collected (passing) into it.