Comparison Atmos C 18S 20 kW vs Atmos DC 18S 20 kW

The type of fuel or heater used by the boiler.

— Gas. Gas boilers are popular due to their low fuel cost and several other 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 boiler 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 the power supply.

— Electricity. Boilers with electric heaters are the easiest to install, because of 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 powerful 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 because the electric current passes directly through the 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 water leaks, there is practically no danger of electric shock. On the other hand, electrode boilers are very demanding on the quality of the water: 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. The main advantage of such boilers is the 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 used where it is impossible to install gas or electric boilers.

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

— Liquid fuel. Boilers, as the name suggests, use liquid fuel. Most often it is 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 are completely autonomous. And 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 chimney, because, during operation, products of combustion 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.

The maximum area of the building 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 Heat output 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.

The maximum 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, and for a domestic hot water circuit up to 10 bar. When the maximum pressure is exceeded, a safety valve is activated, and part of the water is discharged from the system until a normal pressure level is reached.

The efficiency of the boiler.

For electric models (see "Energy source"), this parameter is calculated as the ratio of net power to consumed; in such models, indicators of 98 – 99% are not uncommon. For other boilers, the efficiency is the ratio of the amount of heat directly transferred to the water to the total heat amount released during combustion. In such devices, the efficiency is lower than in electric ones; for them, a parameter of more than 90% is considered good. An exception is gas 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. It 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 vapour. Nevertheless, formally everything is correct: the boiler gives out more thermal energy to the water 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(atmospheric). Combustion chambers of this type consume air from the room in which the boiler is installed, and the combustion products are naturally removed through the flue. Boilers of this design are simple and inexpensive but 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 removed there. For this, a coaxial flue 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 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 often used the coaxial flue, consisting of two pipes nested one inside the other. At the same time, products of combustion are discharged from the combustion chamber through the inner pipe, and the air is supplied through the gap between the inner and outer ones. For such flues, the diameter is usually shown 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. Non-coaxial flues can be 100, 110, 125, 130, 140, 150, 160, 180 and 200 mm.

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

— Copper. Copper is a material with the best heat dissipation specs and high corrosion resistance. 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 in heavy mid-range and premium grade equipment.

— Aluminium. Aluminium as a heat exchanger material is characterized by excellent thermal conductivity and 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 weight and size of hea...ting equipment, which is why boilers with cast-iron heat exchangers are produced mainly in floor-standing boilers. In addition, cast iron does not tolerate sudden temperature changes — they can cause cracks.

— Steel. Steel heat exchangers in heating boilers are the 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.

— Stainless steel. Stainless steel heat exchangers are rare 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 long service life.

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

Diameters are 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 water returns from the heating system to the boiler.

Diameters are 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.