Max. water temperature
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.
Performance (Δt ~25 °C)
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.
Performance (Δt ~50 °C)
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.
Safety systems
The safety of water heaters can be carried out by such functions as
overheat protection frost protection,
dry heating protection,
surge protection,
electrical protection (RCD),
anti-legionella,
gas control and
draft sensor. More about them:
— Overheat protection. Water heater safety system that automatically turns off the power supply or gas supply (depending on the type) when the heating element reaches a critical temperature. It avoids overheating and the troubles associated with it, ranging from heater failure to fire.
— Frost protection. Function to prevent freezing of water in the circuits, tank and/or heat exchanger of the water heater. It will be useful when the device is installed in a room with a low temperature and works with long breaks. Frozen water expands, which can damage the device; to avoid this, the frost protection monitors the temperature of the water in the device and turns on the heating when this temperature drops to a critical level.
— Dry heating protection. A safety system that prevents the heater from being switched on without the presence of water in it. Since the heating element does not transfer heat to the water when turned on, it heats up very q
...uickly and, in a short time, reaches a high temperature that can lead to damage to the heater and even to a fire. The presence of protection against switching on without water allows you to avoid such unpleasant consequences.
— Voltage surge protection. System for protecting the heater from power surges. Electronically controlled models are usually equipped with such protection (see Control) since it is the control electronics that are most sensitive to problems with the power supply. Note that the capabilities of such systems are noticeably more modest than those of specialized stabilizers or protective systems: the “hardware” of a water heater can smooth out relatively weak power surges, but in case of serious failures, it will most likely simply turn off the device to avoid damage. However, this feature will be useful; except that in very unstable electrical grids, prone to frequent fluctuations, such a heater may require an external stabilizer.
— Electrical protection (RCD). Built directly into the heater, the RCD is a residual current device. Such a device is primarily intended to protect people from electric shock — for example, if the insulation is damaged and electricity leaks into the case or water. When a person comes into contact with this electricity, a so-called leakage current occurs. The RCD reacts to it and almost instantly turns off the power to the boiler, preventing electric shock.
Note that such safety devices are standardly installed directly in switchboards. However, the presence of an RCD in the water heater provides additional security. Naturally, such equipment is found mainly in electric models.
— Safety valve. A safety system that prevents a critical increase in water pressure in the heater. Usually, this protection is based on a safety valve that opens when a certain pressure level is reached and drains excess water, avoiding damage to the heater.
— Gas control. Gas heater safety system that automatically shuts off the gas supply in the event of a burner flame failure. It avoids filling the room with gas and possible unpleasant, and even tragic consequences. Resuming the gas supply after the protection is triggered must be done manually.
— Draft sensor. A sensor that monitors the presence of draft in the flue of a gas water heater. This function is especially important for models with open combustion chambers: in the absence of a draft, combustion products will fill the room where the heater is located. And this, in turn, can lead to a deterioration in people's well-being, health problems and even deaths. To avoid such consequences, this sensor, when detecting problems with the draft, turns off the gas supply and issues a warning about the problem. However, such equipment can also be found in models with closed combustion chambers. In them, the draft sensor performs mainly a diagnostic function, allowing you to determine what interferes with the normal operation of the burner.
— Anti-legionella. A function that prevents the growth of pathogenic bacteria in the tank and water heater circuits. Some types of such bacteria can live and multiply in fairly hot water — up to 60 °C. To avoid this, the anti-legionella system monitors the temperature of the water in the tank and periodically raises it to a level of about 65 °C. The specific methods of operation of such systems can be different: for example, some work strictly according to a set schedule (for example, once every two weeks), others turn on additional heating only if for some period (for example, a month) the water has not been heated to sufficiently high temperatures.
