Boilers: specifications, types

The type of fuel or heater used by the boiler.

— Gas. Gas boilers are popular due to the low cost of fuel and a number of practical advantages. For example, heating starts and stops almost instantly, the burner power can be easily adjusted, various additional features can be provided in the design (such as connecting a room thermostat), etc. The disadvantages of this type of boilers are dependence on gas pipelines (gas in cylinders can also be used, but this is rather inconvenient and rarely used), as well as installation complexity and dependence on power supply.

— Electricity. Boilers with electric heaters are the easiest to install — thanks in part to the absence of chimneys — and can have advanced control options. On the other hand, high electricity consumption affects the cost of operation, and only the most low-power models can be connected to a regular outlet — more or less solid units require a separate connection. Electric boilers are convenient primarily where it is not possible to provide the boiler with gas or solid / liquid fuel.

— Electricity (electrode). A variety of electric boilers (see above), also known as "ionic" ("ion-exchange"). The key difference between such devices is that they do not have heating elements or other separate heating elements: heating occurs due to the fact that the electric current passes directly through th...e liquid coolant. In addition to the general advantages of all electric boilers (small size, ease of installation and control, the possibility of using advanced automation, etc.), such models also have such advantages as very high efficiency and good heating rate. It should be noted that even if the coolant leaks, there is practically no danger of electric shock. On the other hand, electrode boilers are very demanding on the quality of the coolant: it must be water with a strictly defined salt concentration, and during use, the resulting electrolysis gases must be regularly removed from the heating system and fresh solution added to it. In addition, units of this type, for technical reasons, are not compatible with RCD protection.

— Solid fuel. Solid fuel boilers most often use coal, coke or special fuel briquettes as fuel. The main advantage of such boilers is a small price. The disadvantages are due to the type of fuel used: it is most often required to be loaded manually, as well as to remove solid combustion products (ash, soot). In addition, the combustion process is difficult to regulate and cannot be stopped until the fuel is completely burned out, which leads to problems in setting the boiler to the required power and may require special automation. Therefore, such boilers are most often used where, for some reason, it is impossible to install gas or electric boilers.

— Firewood. Wood-fired boilers are a type of solid fuel boilers with all their characteristic advantages and disadvantages (see above for details). The main feature of such boilers is that they can use a pyrolysis combustion scheme, which significantly increases the efficiency (see Pyrolysis).

— Liquid fuel. Boilers which, as the name suggests, use liquid fuel. Most often we are talking about diesel fuel, but some models can also work with lower quality options — such as fuel oil or even used oil. Such boilers are in many ways similar to gas boilers — in particular, they make it easy to adjust the operating mode and instantly stop heating. At the same time, they do not require connection to highways, due to which they are completely autonomous; And yes, they tend to be more powerful. On the other hand, such units require fairly large fuel tanks, otherwise you will have to constantly refill the tank during the season, and the fuel itself is much more expensive than gas. In addition, boilers of this type have increased requirements for the quality of the hood, because. during operation, a lot of combustion products are formed. Another drawback is their high cost. Therefore, liquid fuel models are not widely used; most often they are used as an option for those rooms in which it is impossible to conduct gas.

In addition to single-fuel boilers, there are also combined boilers that can operate with more than one energy source. In modern models, almost any combination is found — for example, gas and liquid fuel, solid fuel and electricity, etc. The exception is perhaps the option "electricity plus liquid fuel", such units are practically not produced. Anyway, compatibility with several energy sources makes the boiler more versatile and less dependent on malfunctions (for example, gas pipeline failures), but it affects its cost. Also note that switching to another energy source may require additional work — for example, replacing a gas burner with a fuel injector.

According to the installation method, boilers are divided into two main types: wall and floor.

— Wall -mounted boilers, as the name suggests, are designed to be mounted on a wall. They usually have low power, which makes it possible to do without a separate room for their installation, and relatively small dimensions, which allow the boiler to “fit” into the interior of a kitchen or bathroom.

— Floor boilers usually have more power than wall-mounted ones, which accordingly affects their weight, dimensions and, in fact, the installation method. The weight is also due to the presence of a cast iron heat exchanger, which is considered more reliable and durable than copper, steel or silumin. Most boilers with a power of 50 kW or more and almost all boilers with a power of 100 kW or more are floor-standing.

— Parapet. Also, boilers of this type can be called "wall" — they are designed for installation close to the wall; at the same time, the installation itself can be both wall-mounted and floor-mounted, depending on the dimensions and weight of the unit. All parapet boilers are gas-fired (see Energy Source) and have a closed combustion chamber (see below); in this case, the chimney is brought out directly through the wall, near which the boiler is located. One of the key advantages of such devices is their small size; a parapet boiler is considered a good option for a small city apartm...ent or a private house with small rooms. Also, the advantages of such devices include the fact that they do not burn the air from the room and immediately remove the products of combustion to the outside. In addition, many of the boilers of this type have convection holes and during operation they also play the role of heating radiators.

Depending on the set of functions, boilers are divided into single-circuit and double-circuit.

- Single -circuit boilers are equipped with one heat exchanger, in which the heat from fuel combustion is transferred to the heat carrier of the heating system. The only function of such boilers is space heating. It is technically possible to use single-circuit boilers to provide hot water, but this requires an additional boiler (the so-called indirect heating boiler).

- In double-circuit boilers, the primary heat exchanger is supplemented by a secondary one, due to this, such a boiler, in addition to heating the room, also provides hot water supply. In this case, both running water and water accumulated in a special container (see Built-in boiler) can be used.

The maximum area of the room that the boiler can effectively heat. However, it is worth considering that different buildings have different thermal insulation properties and modern buildings are much “warmer” than 30-year-old and even more so 50-year-old houses. Accordingly, this paragraph is more of a reference nature and does not allow a full assessment of the actual heated area. There is a formula by which you can derive the maximum heating area, knowing the useful power of the boiler and the climatic conditions in which it will be used; see Net Power for more details. In our case, the heating area is calculated according to the formula "boiler power multiplied by 8", which is approximately equivalent to use in houses that are more than a dozen years old.

Boilers that generate additional heat by condensing water vapor from combustion products. In such units, the combustion products, before entering the chimney, are passed through an additional heat exchanger, in which they are cooled, and the water vapor condenses and transfers thermal energy to the coolant. This allows you to increase the efficiency by 10 – 15% compared to boilers of the classical design — up to the fact that in many similar models the efficiency exceeds 100% (for more details, see "Efficiency").

The condensation principle of operation is most often found in gas models (see "Power source"); however, solid and liquid fuel boilers with this feature are also produced.

Boilers using the pyrolysis principle of operation during operation; they are also sometimes called gas generators. Such models are only solid fuel (including wood-burning — see "Source of Energy"). Without going into unnecessary details, the scheme of their operation can be described as follows: during the operation of the boiler, not only the fuel itself burns out, but also the combustible gas released from it at high temperatures. This allows you to significantly increase the efficiency and provides additional features for power adjustment. In addition, in such boilers almost no soot is formed, and the amount of ash is minimal. Among the disadvantages of pyrolysis models, one can note the high cost, the need to connect to a power supply, as well as specific requirements for certain types of fuel: for example, wood for such a unit must be very dry (less than 15%), otherwise all the advantages of the pyrolysis scheme will be nullified .

Long-burning boilers include a specific type of solid fuel models (see "Source of Energy"). Such boilers have a rather large height with a small width, as well as a special air circulation system. Due to all this, not the entire mass of fuel is involved in the combustion process, but only a relatively thin layer (usually about 10 – 15 cm). This means that a lot of fuel can be loaded into the boiler, but it will burn out gradually, without generating excessive power and allowing it to work for a long time on one “charge” (hence the name).

The presence of a built-in boiler in the boiler — a storage tank for water used in the hot water supply system. For obvious reasons, this feature is found exclusively in double-circuit boilers (see "Type"). It provides a number of advantages over a flow-through design (when the boiler heats water directly in the process of moving through the heat exchanger). Firstly, in the boiler, you can constantly keep a supply of hot water at the ready, and use it even in case of interruptions in the water supply. Secondly, the temperature of the dispensed water is constant, while in flow devices fluctuations are possible when the water flow rate changes. Thirdly, the efficiency of work does not depend on the pressure in the water supply (flow heaters may “not see” the flow of water at low pressure and not turn on). On the other hand, this feature significantly affects the dimensions, weight and price of the boiler.

The volume of the boiler provided in the boiler.

In this case, we can talk about both a built-in boiler (see above), and a separate device supplied in the kit. The first option is found in double-circuit boilers, the second — in single-circuit ones (see "Type"). Anyway, the larger the tank, the more water you can keep in reserve, but the larger and heavier the entire boiler or individual boiler is. There are special methods that allow you to calculate the optimal tank capacity depending on the number and type of water points, the number of users, etc. Such methods are described in detail in special sources, but we note here that the average value is considered to be about 80 – 100 liters, this is enough for regular use by a family of 3 – 4 people.

The volume of the buffer tank supplied with the boiler.

The buffer tank is a kind of heat accumulator: it is a large (with a volume of several tens of liters) tank with good thermal insulation, connected to the heating system. From the top of the tank, heated water enters the heating system, and the cooled coolant returns to the bottom of the tank. The buffer tank significantly increases the total amount of coolant in the system and plays the role of a kind of heat accumulator: when the boiler is completely turned off, the heating system cools down several times slower than without such a tank. This will be especially useful in the event of a fuel/power outage. In addition, when properly installed, such a tank avoids overheating of the system in the event of a failure of the circulation pump.

As for the capacity of the buffer tank, it is selected by the manufacturer depending on the total capacity of the boiler and the area on which it is supposed to be used. There are formulas that allow you to calculate the optimal capacity for a given situation; such calculations are described in more detail in special sources.

Only solid fuel boilers can be equipped with a bunker (see "Energy source"). It is a design of a container for fuel and an automatic feeder. This design eliminates the need to manually load the boiler (although this may be possible in some models) and greatly facilitates boiler management. So, from the control panel, you can set a number of different parameters, ranging from the required temperature to the full daily cycle of operation — and the automatic bunker will provide the required amount of fuel itself, without constant control by the operator. For normal operation of the bunker fuel in pellets (granules) is necessary.

The volume of the bunker installed in the boiler.

About the bunker itself, see above. And the amount of fuel that can be loaded into the boiler at a time depends on its volume. Note that the capacity of the bunker is selected by the manufacturer depending on the power and high consumption of the boiler — so that the fuel does not have to be loaded too often and at the same time the bunker is not too bulky.

This function allows you to use the boiler also as a stove. It is found exclusively in solid fuel models (see "Power source"). The role of the hob in such boilers is played by the upper part of the body: it has a lid that opens directly into the furnace. To use the boiler as a stove, you need to open the lid and place a pot, frying pan or other dish over the hole — in this way, the bottom of the dish will be heated directly from the heat of the firebox. Usually such a "burner" can be adjusted in size; it, usually, is only one, but more often it is not required.

The presence of a heat pump in the boiler delivery set.

A heat pump is a kind of "air conditioner in reverse": it takes heat from the environment and transfers it to the room (more precisely, to the heating system). The advantage of such devices lies in the high ratio of useful power to consumed: the amount of heat produced by the heat pump is many times higher than the amount of energy spent on its operation. On the other hand, the efficiency of such units is greatly reduced as the outside temperature drops. Therefore, heat pumps are mainly used as auxiliary equipment for the heating system. However, such an addition can significantly reduce the cost of space heating.

Net output of the heat pump supplied with the boiler.

The purpose and features of heat pumps as a whole are described in detail. higher. And the useful power in this case is the heating power — the amount of heat provided by the unit. The general meaning of this parameter is the same as for the useful output of the boiler (see below). However, when choosing, it should be taken into account that the maximum useful power of the heat pump is usually given in the characteristics, while the actual power is highly dependent on outdoor conditions and decreases as the air temperature drops. So it’s worth choosing according to this parameter with a certain margin — at least 10-15 percent.

The presence of a solar collector in the boiler delivery set.

Such equipment, in accordance with the name, provides heating of the coolant due to sunlight. It can be a good addition to the heating system, especially since solar energy is practically free and its production does not require any costs (except, in fact, the purchase of a collector). At the same time, the efficiency of a solar collector naturally depends on the weather and greatly decreases in winter (and not every model allows year-round use). Therefore, in boilers, solar collectors are provided exclusively as ancillary equipment, which makes it possible to reduce the cost of obtaining heat.

Thermal power of the solar collector, which is equipped with the boiler.

About the solar collectors themselves, see above. And the thermal power of such a device is added to the useful power of the boiler itself (see the relevant paragraph) and affects the overall efficiency of the heating system. However, note that the characteristics of the solar collector give the maximum power achieved under perfect operating conditions: a clear sky, a relatively high air temperature and a strictly perpendicular direction of the sun's rays relative to the plane of the absorber. In fact, such conditions are achieved extremely rarely, so that the actual power most often turns out to be noticeably lower.

Remote control unit that allows you to control the boiler from another room. It can be connected both wired and wirelessly, often equipped with an electronic display to indicate operating modes, set temperature, emergency situations, etc. Many of these blocks are quite advanced devices with the ability to programme the operation of the boiler, for example, for a week; some models can be equipped with temperature sensors that automatically adjust the intensity of the boiler depending on the temperature in the room.

The useful power of the boiler is the heating power that it provides at maximum mode.

The ability of the device to heat a room of a particular area directly depends on this parameter; by power, you can approximately determine the heating area, if this parameter is not indicated in the characteristics. The most general rule says that for a dwelling with a ceiling height of 2.5 – 3 m, at least 100 W of heat power is needed to heat 1 m2 of area. There are also more detailed calculation methods that take into account specific factors: the climatic zone, heat gain from the outside, design features of the heating system, etc.; they are described in detail in special sources. Also note that in double-circuit boilers (see "Type"), part of the heat generated is used to heat water for hot water supply; this must be taken into account when evaluating the net power.

It is believed that boilers with a power of more than 30 kW must be installed in separate rooms (boiler rooms).

The minimum thermal power at which the heating boiler can operate in constant mode. Operation at minimum power allows you to reduce the number of on and off cycles that adversely affect the durability of heating boilers.

The type of electrical supply required for normal operation of the boiler. Power supply may be required not only for electric models, but also for other types of boilers (see "Power supply") — in particular, for the operation of control automation. Connection options can be:

— 230 V. Work from a conventional household network with a voltage of 230 V. At the same time, models with a power consumption of up to 3.5 kW can be connected to a regular outlet, but for more “gluttonous” devices, you need to connect directly to the shield. Many of the electric boilers with this connection also allow operation from 400 V (see below).

— 400 V. Operation from a three-phase network with a voltage of 400 V. This power supply is suitable for boilers with any power consumption, however, it is not as common as 230 V: in particular, it may be difficult to use it in a residential area. Therefore, this option is provided mainly in high-power devices for which 230 V power supply is not suitable in principle.

— Autonomous work. Work in completely autonomous mode, without connection of electricity. This format of operation is found in all boilers that do not use electrical heating (see "Energy Source"), with the exception of purely liquid fuel ones — in them electricity is necessary for the operation of the fuel supply systems.

The maximum electrical power consumed by the boiler during operation. For non-electric models (see Power Source), this power is usually low, as it is required mainly for control circuits, and it can be ignored. Regarding electric boilers, it is worth noting that the power consumption in them is most often somewhat higher than the useful one, since part of the energy is inevitably dissipated and not used for heating. Accordingly, the ratio of useful and consumed power can be used to evaluate the efficiency of such a boiler.

The current in amps consumed by the electric boiler (see "Power Source") during normal operation.

This parameter directly depends on the power. It is required primarily for organizing the connection: wiring and automation must normally transfer the current consumed by the unit.

The minimum temperature of the heat carrier provided by the boiler when it is turned on in heating mode.

The maximum operating temperature of the heat carrier in the boiler system when operating in heating mode.

The maximum allowable pressure in the heating circuit of the boiler, at which it remains operational and there is no risk of physical damage to the structure. For a heating system, the maximum pressure is usually about 3 bar, for a hot water system up to 10 bar. When the maximum pressure is exceeded, protection (safety valve) is activated and part of the water is discharged from the system until a normal pressure level is reached.

The maximum allowable pressure in the hot water circuit (DHW) of the boiler, at which it is able to operate indefinitely for a long time without failures and damage. See "Maximum pressure in the heating circuit.

The minimum temperature of hot water supplied by a double-circuit boiler in hot water supply (DHW) mode. For comparison, we note that water begins to be perceived as warm, starting from 40 °C, and in centralized hot water supply systems, the temperature of hot water is usually about 60 °C (and should not exceed 75 °C). At the same time, in some boilers, the minimum heating temperature can be only 10 °C, or even 5 °C. A similar mode of operation is used to protect pipes from freezing during the cold season: the circulation of water with a positive temperature prevents the formation of ice inside and damage to the circuits.

It is also worth bearing in mind that when heated to a given temperature, the temperature difference ("Δt") may be different — depending on the initial temperature of the cold water. And the performance of the boiler in the DHW mode directly depends on Δt; see below for performance details.

The maximum temperature of hot water supplied by a double-circuit boiler in hot water mode. For comparison, we note that water begins to be perceived as warm, starting from 40 °C, and in centralized hot water supply systems, the temperature of hot water is usually about 60 °C (and should not exceed 75 °C). Accordingly, even in the most modest models, this figure is about 45 °C, in the vast majority of modern boilers it is not lower than 50 °C, and in some models it can even exceed 90 °C.

It is also worth bearing in mind that when heated to a given temperature, the temperature difference ("Δt") may be different — depending on the initial temperature of the cold water. And the performance of the boiler in the DHW mode directly depends on Δt; see below for performance details.

The performance of a double-circuit boiler in the hot water supply mode when the water is heated by 25 °C above the initial temperature.

Productivity is the maximum amount of hot water that 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 — “delta te”) between cold and heated water, the more energy is required for heating and the smaller the volume of water with which the boiler can handle in this mode. Therefore, the performance of double-circuit boilers is necessarily indicated for certain options Δt — namely 25 °C, 30 °C and/or 50 °C. And it’s worth choosing according to this indicator, taking into account the initial water temperature and taking into account what kind of hot water demand there is at the installation site of the boiler (how many points of water intake, what are the temperature requirements, etc.); detailed recommendations on this subject can be found in special sources.

We also 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, in order for the boiler to operate in the Δt=25 °C mode and produce at least warm water at 40 °C, the initial temperature of cold water must be at least 15 °C (15+25=40 °C). This is a rather high value — fo...r 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 this performance is a very conditional value; in fact, the boiler does not work so often with a temperature difference of 25 °C. Nevertheless, the data for Δt=25°C is still often given in the specifications — including for advertising purposes, since it is in this mode that the performance figures are the highest. In addition, this information may be useful if the boiler is used as a pre-heater, and heating to operating temperature is provided by another device, such as an electric boiler or instantaneous water heater.

The performance of a double-circuit boiler in hot water mode when water is heated by approximately 30 °C above the initial temperature.

Productivity is the maximum amount of hot water that 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 — “delta te”) between cold and heated water, the more energy is required for heating and the smaller the volume of water with which the boiler can handle in this mode. Therefore, the performance of double-circuit boilers is necessarily indicated for certain options Δt — namely 25 °C, 30 °C and/or 50 °C. And it’s worth choosing according to this indicator, taking into account the initial water temperature and taking into account what kind of hot water demand there is at the installation site of the boiler (how many points of water intake, what are the temperature requirements, etc.); detailed recommendations on this subject can be found in special sources.

We also 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, in order for the boiler to operate in the mode Δt ~ 30 °C and give out at least warm water at 40 °C, the initial temperature of cold water should be about 10 °C (10 + 30=40 °C). A similar temperature can be...found in wells in the warm season, and cold water in the centralized water supply system often warms up to 10 °C in the warm season. However, boilers, including double-circuit boilers, are switched on mainly in cold weather, when the initial water temperature is noticeably lower. Accordingly, if the boiler is used as the main water heater, heating to the claimed temperatures (see "Min. t hot water", "Maximum t hot water") often requires a greater Δt than 30 °C, and the performance is less than indicated in this paragraph. But when operating in the preheating mode (when the water is heated to the desired temperature by an additional device like a boiler), this indicator very reliably describes the capabilities of the unit.

The performance of a double-circuit boiler in hot water mode when water is heated by approximately 50 °C above the initial temperature.

Productivity is the maximum amount of hot water that 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 — “delta te”) between cold and heated water, the more energy is required for heating and the smaller the volume of water with which the boiler can handle in this mode. Therefore, the performance of double-circuit boilers is necessarily indicated for certain options Δt — namely 25 °C, 30 °C and/or 50 °C. And it’s worth choosing according to this indicator, taking into account the initial water temperature and taking into account what kind of hot water demand there is at the installation site of the boiler (how many points of water intake, what are the temperature requirements, etc.); detailed recommendations on this subject can be found in special sources.

We also 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, when working with Δt of about 50 °C, the boiler is able to heat even water with an initial temperature of about zero to the “hot” state. So it is precisely by this performance value that one can most accurat...ely assess the capabilities of the unit if it is used as the main source of hot water.

The boiler has a Wi-Fi module. This function is most often used to remotely control the unit from a smartphone, tablet or other device. The specific features of such control may be different: for some models, you need to install a special application, for others, control is available through a page in any browser; the gadget can be connected directly or via the Internet, etc. The details of using Wi-Fi in each case should be clarified separately. Here we note that through such a communication channel, you can not only control the unit, but also receive notifications from it — about the operating mode and parameters, about the current state, about failures and malfunctions, etc. At the same time, this function is relatively rare — in In most cases, traditional control is sufficient.

The outdoor temperature sensor allows you to monitor the outdoor weather conditions and automatically adjust the operation of the boiler to them — increase the heating power when the outside temperature drops and decrease it when it rises.

Boiler operating mode, designed for the warm season. In this mode, it works only to provide hot water (if such a function is provided), the heating is turned off. If the boiler is equipped with an outside temperature sensor, this sensor is also switched off in summer mode so that the heating does not turn on at night when the outside temperature drops.

The boiler has a special mode for underfloor heating systems.

Underfloor heating differs from conventional heating systems primarily by a lower coolant temperature — otherwise the floor could be too hot for comfortable use (plus, high temperatures are also undesirable for flooring and furniture installed on it). In addition, boilers with this function are distinguished by increased pump power — in order to ensure efficient circulation of the coolant through branched heating circuits that have a rather high resistance.

Support for the hot start function by the boiler.

This function is found only in double circuit models (see "Type"): it accelerates the heating of water for the domestic hot water system and ensures a constant leaving water temperature. To do this, the boiler automation monitors and controls the temperature of the water in the secondary heat exchanger of the boiler in a special way. The presence of a "hot start" affects the cost of the unit, but this is offset by ease of use.

The presence in the boiler of its own circulation pump.

Such a pump ensures the movement of the coolant along the heating circuit, due to which the heat is evenly and efficiently distributed over the radiators. Similar devices are also available as separate devices; however, buying a boiler with a circulation pump eliminates the need to purchase additional equipment and simplifies the heating system. The disadvantages of such models include the difficulty in troubleshooting: if a separate pump fails, it is enough to replace only it, and the module built into the boiler may require complex and expensive repairs, and at this time the heating system becomes unavailable.

Also note that it is theoretically possible to build a heating system without a pump, based on natural circulation; however, such systems have a number of disadvantages, so that in fact it is still preferable to use forced circulation.

The control bus with which the boiler is compatible.

The control bus is a communication channel through which control and controlled devices can exchange data. Support for such a channel greatly simplifies the connection of thermostats and other control automation — it is enough that such devices are compatible with the same bus as the boiler. In addition, many types of tyres allow you to create very extensive monitoring and control systems and easily integrate various devices into them, including heating boilers.

In modern heating technology, the most popular tyres are OpenTherm, eBus, Bus BridgeNet and EMS. Here are their key features:

— Opentherm. A fairly simple standard with modest functionality: it allows only a direct connection between the control and the controlled device, and is not designed to create extensive systems. On the other hand, this bus has quite advanced capabilities for controlling heaters: in particular, it allows you to control the temperature not just by turning the boiler on / off, but by changing the power of the gas burner. This mode of operation contributes to saving fuel / energy, as well as reduces wear and increases the life of the heater; and in many cases, a system of two devices (boiler and thermostat) is quite enough for effective heating control. At the same time, the OpenThe...rm standard is simple and inexpensive to implement, which makes it extremely popular in modern boilers. For a number of reasons, it is mainly used in gas models.

— eBUS. A control bus that has some pretty impressive practical features. Allows you to combine up to 25 control and 228 controlled devices in one system, with a data transmission distance between individual components up to 1 km. At the same time, eBUS is an open standard, its implementation (at least within the framework of the main functions) is freely available to everyone. And although nowadays eBUS support can be found mainly in Protherm and Vaillant equipment, however, in general, in boilers this is the second most popular type of control bus, after OpenTherm. This lag is mainly due to slightly higher cost, while advanced eBUS capabilities are not really needed as often.

— Bus Bridge Net. Hotpoint-Ariston proprietary development, used exclusively in boilers of this brand. One of the advantages is a high degree of automation: the user only needs to set the temperature parameters (and for different zones, you can choose your own options) and, if desired, a weekly programme, the rest of the necessary calculations and adjustments will be carried out by the system. However, such features are available only in special control devices such as temperature controllers; in boilers, Bus BridgeNet support usually means only compatibility with such automation.

— EMS. A control bus used primarily in Bosch and Buderus equipment. In general, it is characterized by wide functionality, a high degree of automation and the ability to create extensive control systems. However, note that nowadays you can find both the original EMS and the modified EMS Plus, and these standards are not initially compatible with each other (although support for both of them may well be provided in separate devices). So the specific version of the EMS bus should be specified separately; here we note that in Bosch technology there is mainly an original version, and in Buderus devices — EMS Plus (although exceptions are possible there and there).

The presence of a programmer in the design of the boiler.

A programmer is called a programmable thermostat — a device that allows not only to maintain the temperature, but also to programme the operation of the boiler for a certain period of time. The simplest programmers cover a day, more advanced ones allow you to set the operating mode for individual days of work. Anyway, this function provides additional convenience and eliminates the need to constantly adjust the operation of the boiler manually. On the other hand, the presence of a programmer affects the cost.

The efficiency of the boiler is the main indicator characterizing the efficiency of its operation.

For electric models (see "Energy source"), this indicator is calculated as the ratio of useful power to consumed; in such models, indicators of 98 – 99% are not uncommon. For combustible fuel boilers, the efficiency is the ratio of the amount of heat directly transferred to the coolant to the total amount of heat released during combustion. In such devices, the efficiency is lower than in electric ones; for them, an indicator of more than 90% is considered good. An exception are condensing boilers (see the relevant paragraph), where the efficiency can even be higher than 100%. There is no violation of the laws of physics here, this is a kind of advertising trick: when calculating the efficiency, an inaccurate method is used that does not take into account the energy spent on the formation of water vapor. Nevertheless, formally everything is correct: the boiler gives out more thermal energy to the coolant than is released during the combustion of fuel, since condensation energy is added to the combustion energy.

The type of combustion chamber provided in the boiler.

— Open(chimney). Combustion chambers of this type consume air from the room in which the boiler is located, and the combustion products are naturally removed through the chimney. Boilers of this design are simple and inexpensive, but they have specific installation requirements: the room must be well ventilated, and the height of the chimney must be at least 4 m to ensure sufficient draft.

— Closed(turbocharged). Closed combustion chambers are isolated from the room in which the boiler is installed: combustion air is taken from the street, and combustion products are sent there. For this, a coaxial chimney is usually used — in the form of two pipes nested one inside the other: combustion products are removed through the inner one, and the outer one is responsible for the air supply. Turbocharged combustion chambers are more complicated and more expensive than open ones, and the maximum length of the chimney is limited. On the other hand, such a boiler does not burn the air in the room, and it can be installed anywhere, regardless of the ventilation efficiency.

— Is absent. Boilers powered by electricity do not have combustion chambers (see "Source of Energy").

The diameter of the pipe through which combustion products are discharged from the combustion chamber.

In boilers with a closed combustion chamber, the so-called coaxial chimney, consisting of two pipes nested one inside the other. At the same time, combustion products are discharged from the combustion chamber through the inner pipe, and air is supplied through the gap between the inner and outer ones. For such chimneys, the diameter is usually indicated in the form of two numbers — the diameter of the inner and outer pipes, respectively. The most popular values are 60/100, 80/80 and 80/125. Classically, the chimney (not coaxial) can be 100, 110, 125, 130, 140, 150, 160, 180 and 200 mm.

Optimum gas pressure supplied to the inlet of the boiler system. Most often indicated for natural gas and is about 15-20 mbar. This parameter must match the parameters of the gas supply system. However, the pressure in the latter may be higher, which may require the installation of a special gas regulator — this issue is resolved when installing the boiler, which can only be carried out by a qualified gas master.

Maximum gas flow in the boiler with the corresponding energy source (see above). Achieved when the gas heater is operating at full capacity; with reduced power and consumption, respectively, will be lower.

Note that boilers of the same power may differ in gas consumption due to the difference in efficiency; while the more fuel-efficient models tend to cost more, but the price difference pays off in gas savings.

The capacity of the expansion tank supplied with the boiler.

The expansion tank is designed to drain excess water from the heating system when the total volume of liquid increases as a result of heating. It consists of two parts connected by a flexible membrane: in one, hermetically closed, there is air under pressure, in the other, "excess" water enters, compressing the membrane. In this way, a catastrophic increase in pressure in the heating circuit is avoided. The optimal volume of the expansion tank depends on a number of system parameters, primarily the volume and composition of the coolant; detailed recommendations for calculations can be found in special sources.

Gas pressure in the hermetically sealed part of the expansion tank (for details on the design, see Expansion tank capacity). The required pressure in the expansion vessel must be approximately 0.3 bar higher than the initial pressure in the system. The initial pressure, in turn, directly depends on the total height of the heating system, or rather on the difference between the height of the highest and lowest points of the heating system. It can be derived using the approximate formula P=h/10, where P is the initial pressure in bar, h is the height difference between the highest and lowest point of the system in metres. Thus, if the height difference is 2 m, the initial pressure in the system is 0.2 bar, and the pressure in the expansion tank must be at least 0.5 bar.

The amount of heat carrier passing through the boiler heat exchanger per unit of time. The optimal performance is such that three full volumes of the entire heating system pass through the heat exchanger per hour.

The material of the primary heat exchanger, in which thermal energy from hot combustion products is transferred to the coolant. The efficiency of the boiler, the heating rate and the service life of the unit directly depend on the material of manufacture of the heat exchanger.

— Copper. Copper is a material with the best heat dissipation characteristics and high resistance to corrosion. It heats up quickly, which allows you to save energy during the operation of the heating boiler, has a low roughness coefficient, and has a long service life. The only drawback of this metal is its high cost. Copper heat exchangers are installed on board heavy mid-range and premium grade equipment.

— Aluminium. Aluminium as a heat exchanger material is characterized by excellent thermal conductivity, long service life, moreover, it is cheaper than copper. To reduce the cost of production in copper heat exchangers, they try to reduce the wall thickness. You don't need to do this with aluminium.

— Cast iron. Boilers with a cast-iron heat exchanger heat up for a long time and cool down slowly, retaining heat for a long time after heating stops. Cast iron is also notable for its high heat capacity and low susceptibility to corrosion. The service life of a cast iron unit can be 30 or 50 years. The reverse side of the coin is the huge w...eight and size indicators of heating equipment, which is why boilers with a cast-iron heat exchanger are produced mainly in a floor layout. In addition, cast iron does not tolerate sudden temperature changes — they can cause cracks.

— Steel. Steel heat exchangers in heating boilers are most widely used. Steel has a combination of high ductility and strength when exposed to high temperatures, is inexpensive, and can be easily processed at production stages. However, steel heat exchangers are susceptible to corrosion. As a result, they are not as durable.

— From stainless steel. Stainless steel heat exchangers are "rare birds" in heating boilers, which is explained by the high cost of using this material. But they combine the advantages of both cast iron and steel. Stainless steel exhibits high corrosion resistance, resistance to thermal shocks, low inertia, and has a long service life.

The diameter of the pipe for connecting the pipe through which cold water is supplied to the boiler for heating and use in the hot water supply system.

Diameters are traditionally indicated in inches. In some cases, it is allowed to connect a pipe of a different diameter through an adapter, but the best option is still a match in size. There are connection options 1/2", 3/4", 1" and 1 1/2".

The diameter of the pipe for connecting the pipe through which hot water leaves the boiler for the DHW system.

Diameters are traditionally indicated in inches. In some cases, it is allowed to connect a pipe of a different diameter through an adapter, but the best option is still a match in size.

The diameter of the branch pipe for connecting the gas supply pipe in the boiler with the corresponding type of power supply (see "Energy source").

Diameters are traditionally indicated in inches. In some cases, it is allowed to connect a pipe of a different diameter through an adapter, but the best option is still a match in size. The most common options are 1/2" and 3/4".

The diameter of the pipe for connecting the pipe through which the heated coolant enters the heating system from the boiler.

Diameters are traditionally indicated in inches. In some cases, it is allowed to connect a pipe of a different diameter through an adapter, but the best option is still a match in size. Among which models stand out for 3/4", 1", 1 1/4" and 1 1/2".

The diameter of the pipe for connecting the pipe through which the cooled coolant returns from the heating system to the boiler.

Diameters are traditionally indicated in inches. In some cases, it is allowed to connect a pipe of a different diameter through an adapter, but the best option is still a match in size.

— Gas pressure drop. This protection system ensures that the boiler is switched off in the event of a critical drop in gas pressure, insufficient for the normal functioning of the burner. In the event of such a fall, the valve that supplies gas to the burner is closed and blocked. After the restoration of gas pressure, it also remains closed, it is necessary to open it and resume the gas supply manually.

— Overheating of water. Temperature sensor that automatically turns off the boiler when the temperature of the coolant in the system is critically exceeded.

— Extinction of the flame. Flame extinction protection is based on a sensor that monitors the combustion of gas and automatically stops its supply in the event of a burner extinction. This prevents the room from filling with gas and the possible tragic consequences of this.

— Lack of traction. In boilers with an open combustion chamber, in order to maintain normal conditions in the room where such a boiler is installed, a constant removal of combustion products into the atmosphere is necessary. The lack of normal draft in the chimney can lead to the accumulation of combustion products in the room. The draft protection system prevents this by automatically turning off the boiler when it detects the release of combustion products outside the chimney.
...> — Power outage. Most modern boilers have an electronic control system; in addition, many structural elements (pumps, valves, fans, etc.) are also powered by electricity. Thus, a power outage during the operation of the boiler will inevitably lead to an abnormal mode of operation, which is fraught with breakdowns and even accidents. To prevent such cases, a power outage protection system is installed, which completely stops the operation of the boiler in the event of a power outage. When the power supply is restored, the boiler usually needs to be restarted manually.

— Violation of water circulation. This protection system controls the normal movement of the coolant along the heating circuit. Violation of circulation can lead to overheating of individual elements of the boiler and damage to it. To avoid this, if the circulation is disturbed, the system turns off the pump and shuts off the gas supply to the burner.

— Freezing of liquid in the circuit. A system that controls the temperature in the heating circuit. Freezing of the liquid in the circuit disrupts the normal operation of the heating, which may, at best, require heating of the pipes, and at worst, lead to system damage (ruptures). To avoid this, when the coolant temperature drops below 5 °C, the burner is ignited, the circulation pump is activated and the circuit warms up to a temperature of about 35 °C — thus preventing the formation of ice in the pipes.

Such a panel usually covers the front of the unit. Its role is mainly decorative: glass does not affect the functionality, but it gives the boiler an aesthetic appearance. It is also worth noting that glass is easier to clean from dirt than painted metal. However, note that the presence of a glass panel significantly affects the cost. So it makes sense to specifically look for a boiler with this feature if it is planned to be installed in plain sight and a stylish appearance for the unit is no less important than performance.

The size of the furnace is characterized by two parameters:

1. directly by the dimensions, due to which it is possible to determine the appropriate size firewood for use with the boiler;

2. volume, which characterizes the amount of fuel used in the furnace.