Comparison Bosch Therm 4000 O WR 10-2 P vs Hotpoint-Ariston FAST CF 11

The type of power required to operate the water heater.

— 230 V (1 phase). Powered by a single-phase household main at 230 V. At the same time, relatively low-power models (up to 3.5 kW) can be plugged into a regular outlet, with higher power a special connection format will be required. However, such devices are relatively easy to supply. On the other hand, in heaters of more than 10 kW, this option is practically not found.
Also note that it is this type of power that is used by all gas and indirect models, in which electricity is required only for the operation of control circuits. The power consumption of such circuits is small, and an ordinary outlet is enough for them, as they say, “with a head”.

— 400 V (3 phases). Powered by a three-phase main at 400 V. This power format can be called "industrial", connection to 400 V is available in specialized boiler rooms, workshops and other similar places, but in an ordinary residential area it may be difficult — you will likely have to pull the wire to the street power line or switchboard. On the other hand, such power is suitable for heaters of any power. And if you have the opportunity to connect the heater to both 230 V and 400 V, it is better to choose the second option — it will provide a more reliable account of the energy consumed.

— Non- Energy independent. Water heaters that operate without power at all and do not require an electrical connection. Only gas a...nd indirect models can be energy-independent (see “Energy source”). However, not every gas or indirect heater belongs to this category.

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.

Water heater performance when heating water by approximately 50 °C above the initial temperature.

Productivity 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, Δt~50 °C can be described as a very significant degree of heating: it allows even water with a temperature of about zero to be heated to the “hot” state, and the level of 60 °C can be reached at an initial temperature of only 10 °C (this temperature, for example, it is quite possible to meet in cold tap water even in the off-season, not to mention the summer). However, in modern water heaters, operati...ng temperatures above 60 °C are often found; to achieve them, you usually have to work with ΔT greater than 50 °C — respectively, and the actual performance is less than indicated in this paragraph. Nevertheless, it is this parameter that is closest to the real capabilities of the water heater when it comes to the full conversion of cold water into hot.

The method of ignition of gas in gas water heaters.

— Batteries. Ignition from an electric spark created by a special electrical circuit powered by batteries. Battery ignition allows you to ignite without unnecessary wires, it can be used in models that do not require a mains connection at all. However, the user has to monitor the condition of the batteries and periodically change them, but this does not have to be done so often, and the replacement itself is not difficult.

— Mains. Ignition from an electric spark created by electricity from a socket. Batteries do not need to be changed in such systems but water heaters require a connection to the mains. Mains ignition is found mainly among gas heaters with advanced electronic control, in which power from the outlet is required for control circuits — it makes sense to power the ignition from the same outlet.

— Piezo ignition. Ignition due to a piezoelectric element — a special device that generates electricity when a button is pressed (transforms the mechanical energy of pressing into electrical energy). Piezo ignition does not require battery power, and the life of the piezo element is usually comparable to the life of the heater itself.

— Turbine. It is used in instant water heaters (see "Type"). With this type of ignition, electricity to crea...te a spark is generated by a microturbine driven by the movement of water through the heater. At the same time, in many cases, no additional actions are required from the user — ignition occurs automatically when the tap is opened and water begins to move through the device.

Note that most gas boilers also allow traditional ignition, from a match or other open flame. This option is provided as a spare, in case of failure of the main ignition system.

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.