Comparison Midea D80-15F1(W) vs Round VMR 80

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.

— Enamel. Like plastic, enamel is chemically neutral and does not affect the taste and smell of water, while it is considered more durable. Theoretically, this material is prone to the appearance of microcracks, including due to temperature differences (which eventually lead to water contact with metal and corrosion). However, high-quality heat-resistant enamels are most often used in boilers, which have the same coefficient of thermal expansion as the material of the tank and are damaged only in case of violation of operating conditions (or with strong impacts). So the mentioned drawback is typical mainly for the most inexpensive models with appropriate quality materials.

— Stainless steel. Due to its high strength, stainless steel is considered the most reliable and durable material today. Unlike enamelled ones, such tanks are absolutely not afraid of temperature changes, and they also normally withstand hits including pretty strong ones. On the other hand, steel is noticeably more expensive than enamel. At the same time, for such containers, the possibility of corrosion is not ruled out — especially when it comes to cheap devices that use outdated welding technologies, and the material of the seams may differ from the material of the tank. To eliminate this phenomenon, cathodic protection is required, which further affects the cost.

— Glass ceramics....Material, in many respects similar to the enamel described above. On the one hand, glass ceramic does not react with water, does not affect its taste and properties, and is also considered quite reliable. On the other hand, this material is more brittle and prone to the appearance of microcracks and the loss of its properties — both as it wears out and due to strong heating. Because of this, such water heaters usually have a recommended temperature limit of 60 °C.

— Plastic. Plastic is chemically resistant, not subject to corrosion and practically does not affect the composition of water, besides it is inexpensive. The main disadvantage of plastic coating is considered to be fragility.

— Copper. Copper coating is used exclusively in instant water heaters (see "Type"); more precisely, in such devices, the entire tank is usually made of copper. This material is not suitable for a storage tank: copper is too heavy, and it has a corrosive effect on some materials (aluminium, cast iron) due to its electrochemical properties, even if these materials are used outside the heater, in other parts of the water supply system. However, in a small tank in an instant water heater, these moments are invisible, while copper perfectly tolerates compression and tension during temperature changes.

— Titanium-cobalt alloy. A special alloy, characterized by the highest strength and resistance to corrosion, but also very expensive. It is extremely rare, only in top-level heaters.

Time to heat the storage tank (see "Type"), filled with cold water, to operating temperature.

It is worth remembering that this characteristic is not 100% accurate. Manufacturers usually indicate the heating time for certain conditions: a filled tank, maximum heating intensity, and temperature rise (∆T) by a certain number of degrees. In practice, the heating time may differ, both one way and the other. For example, if the heating time for the device is 20 minutes at ∆T = 50 °C, then when the water is heated from 15 °C to 60 °C, the time will be shorter (∆T = 45 °C). Nevertheless, this indicator allows us to evaluate the overall flow rate of the boiler, and with equal ∆T and volumes, different models can be compared in terms of heating time.

Among the functions of the water heater there are thermostat, water flow regulator, Smart (auto mode), programmer, display and control via the Internet. More about each of them

— Thermostat. A device that allows you to control the temperature of the water at the outlet of the heater. In storage models (see "Type"), the thermostat sets the maximum temperature for heating water in the tank; in instant devices, this function is carried out by changing the intensity of heating.

— Automatic water flow regulator. It is used in instant water heaters. Since the water in such devices heats up in the process of its movement through the heater, the higher the speed of water movement (the greater the pressure), the lower the heating temperature, and if the pressure is too high, the power of the device may simply not be enough for effective heating. The use of an automatic water flow regulator avoids this — this system regulates the speed of water movement through the heater, limiting it if necessary.

— Smart (auto mode). A special “smart” mode in which the boiler is controlled (primarily the intensity of heating) automatically. Specific features of this mode may vary depending on the model. However, the following format of operation is most common: during...the first week of use, the device remembers at what time of the day the hot water was used, and then the heater’s operating mode adjusts to this data. Thus, the water heater provides the user with hot water at the right time and, at the same time, does not waste energy on heating during hours when heating is not needed.

— Programmer. The presence of a programmable thermostat — a device that allows not only to maintain the temperature but also to programme the operation of the device for a certain period. The simplest programmers work like a timer, turning on at the right time (vacation or holiday mode, when the device is not active for several days, and when the family returns to the house, it will turn on and heat the water). More advanced ones allow you to set the mode of operation for individual days. Either way, this feature provides added convenience and eliminates the need to constantly adjust the operation of the device manually. On the other hand, the presence of a programmer affects the cost.

— Display. Usually, a simple LCD screen with a few characters is used as a display. However, even such equipment significantly increases the convenience and information content of management. Various service data can be shown on the display — from the temperature of the water in the tank to messages about malfunctions and failures. This feature slightly increases the cost of the device, but compared to the total cost of the heater, this moment is usually insignificant.

— Control via the Internet. The specific nuances of such control may vary: for example, some models use a special application installed on a smartphone or tablet, while others can work through a regular browser from any computer. However, this function allows you to control the heater from almost anywhere in the world — provided that there is access to the Internet. In addition, with this control, the user can also monitor the status of the device and receive various notifications (on and off, about the temperature of the water in the tank, about various problems, etc.).

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.

- Mechanical. Manual control using rotary knobs and mechanical buttons. Models with mechanical controls are inexpensive, but the control capabilities themselves are quite limited and, as a rule, include only basic functions.

- Electronic. This control is carried out using an electronic unit. Electronically controlled heaters, as a rule, have a wider range of functions than their “mechanical” counterparts; they can be programmed and equipped with a display to indicate various parameters. On the other hand, with all other characteristics being equal, such heaters are much more expensive.

The warranty period declared by the manufacturer for the storage water heater tank (see “Type”).

This parameter is important for the reasons of maintenance terms. The tank is the most complex element: other parts of the water heater are relatively easy to repair and change, and if there is a problem with the tank, it is often easier to replace the entire boiler. In the most advanced models, the warranty on the tank can be 10 years or more.