Magnesium anode
Magnesium anode is used in storage heaters (see type). It is an additional means of protecting the tank and heating elements from corrosion. Due to its special electrochemical properties, magnesium significantly slows down the oxidation of other metal parts that come into contact with water. Note that the magnesium anode has a limited service life. It needs to be changed every 5-7 years.
Heating elements
The number of heating elements provided in the design of the water heater. In this case, it is the total number of elements that are taken into account, regardless of whether they belong to the same type or different ones: for example, 2 heat exchangers and 1 heating element are considered as 3 elements.
All gas models (see "Energy source") have only one heating element — this is quite enough for efficient operation. In
combined devices (see ibid.), on the contrary, there are several heating elements by definition (at least two — a heat exchanger and an electric one). In electric and indirect water heaters, the options may be different.
The meaning of several heaters of the same type is primarily to increase the heating efficiency. For example, in an instant (see "Type") electrical water heater, in this way, it is possible to increase the working length — the distance that water passes inside the device from inlet to outlet; by increasing the working length, the water is heated longer. In storage electric models, several heaters provide more uniform heating of the water, and in indirect ones, they allow more heat to be taken away. In addition, in indirect devices, heat exchangers can differ in the source of heating: for example, one can work from a heating boiler, the second from a solar collector.
Also, note that duplication of heating elements can also be used as protection against failures: if one of them
...fails, the heating efficiency decreases, but the device remains operational. However, this possibility is not available in all models with several heaters, its presence should be clarified separately.Heating element type
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Open coil. The open coil is made from a high-resistance electrical wire enclosed in a thin insulating sheath. The main advantages of such an element are the heating rate, high efficiency and precise temperature control; in addition, scale is almost not formed on the spiral. And of the shortcomings — a low service life.
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Wet heating element. Wet heater is a metal tube with a heating thread laid in the centre; the space between the tube and the thread is filled with an insulating material with good thermal conductivity. Heating elements heat up more slowly than open coils, have lower efficiency and are prone to the formation of scale on them; on the other hand, their service life is much longer, and in instant heaters, heating elements are not so sensitive to air pockets.
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Dry heating element. A kind of heating element with an improved design: the heater tube is enclosed in an additional shell (most often made of metal with an enamel coating on the outside) and does not come into contact with water, hence the name. Thanks to this, the likelihood of scale formation is reduced, which is especially important when working with hard water. Also, the replacement of such elements is significantly easier than conventional ones. Among their shortcomings can be called a rather high cost.
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Infrared heating element. Tu
...bular electric heater of a special design: in the form of a transparent glass tube, in which the incandescent spiral is enclosed. The principle of operation of such an element is somewhat different from a conventional heating element: a significant part of the heating is provided by infrared radiation, which heats not so much the water as the walls of the tank — and heat is already transferred from them to the water. Thus, the water is heated not only at the point of contact with the heating element but also at the point of contact with the walls — which means that the heating is faster and more uniform. Also, note that the IR heater itself is usually "dry"; see above for the advantages of this design. The main disadvantages of such heaters are high cost and relatively short service life.
— Heat exchanger. It is used in gas and indirect heaters (see Water heater type). It is a metal structure heated by burning gas (in gas heaters) or passing inside a heated coolant (in indirect heaters). Usually has a ribbed shape. It is done to ensure the maximum area of contact with the heated water with relatively small dimensions — the larger this area, the more heat is transferred to the water per unit of time and the more efficient the heater is.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.Weight
The weight of the device, excluding the water collected (passing) into it.
