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Calculation of boiler power for home heating. Calculation of the power of a gas boiler for a private house - for one and two-circuit schemes Power of a gas heating boiler

Technical consultants of the Termomir company, who have been working with gas boiler equipment for more than a year, often hear the question - How to choose a gas boiler according to the area of \u200b\u200bthe house. Let's deal with this topic in more detail.

A heating gas boiler is a device that, by means of the combustion of fuel (natural or liquefied gas), heats the coolant.

The device (design) of a gas boiler: burner, heat exchanger, thermally insulated housing, hydraulic unit, as well as safety and control devices. Such gas-fired boilers require a chimney to be connected to remove combustion products. The chimney can be either a conventional vertical or coaxial ("pipe in pipe") for boilers with a closed combustion chamber. Many modern boilers are equipped with built-in pumps for forced circulation of water.

The principle of operation of a gas boiler- the coolant, passing through the heat exchanger, heats up and then circulates through the heating system, giving the received thermal energy through radiators, underfloor heating, heated towel rails, as well as providing water heating in the boiler indirect heating(if it is connected to a gas boiler).

Heat exchanger - a metal container in which the coolant (water or antifreeze) is heated - can be made of steel, cast iron, copper, etc. The reliability and durability of a gas boiler depends on the quality of the heat exchanger in the first place. Cast iron heat exchangers are corrosion resistant and have long term services, but are sensitive to sudden temperature changes and are distinguished by significant weight. Steel containers can suffer from rust, so their internal surfaces are protected with various anti-corrosion coatings that prolong the “life” of the device. Steel heat exchangers are the most common in the manufacture of boilers. Corrosion is not terrible for copper heat exchangers, and due to the high heat transfer coefficient, low weight and dimensions, such heat exchangers are often used in wall boilers, but of the minuses, it should be noted that they are more expensive than steel ones.
In addition to the heat exchanger, an important part of gas boilers is a burner, which can be various kinds: atmospheric or fan, single-stage or two-stage, with smooth modulation, double.

To control the gas boiler, automation is used with various settings and functions (for example, weather-compensated control system), as well as devices for programming operation and remote control of the boiler.

The main technical characteristics of gas heating boilers are: power, number of heating circuits, type of fuel, type of combustion chamber, burner type, installation method, pump and expansion tank, boiler control automation.

To determine required power gas heating boiler for private country house or an apartment, a simple formula is used - 1 kW of boiler power for heating 10 m 2 of a well-insulated room with a ceiling height of up to 3 m. If heating of a glazed basement is required winter garden, rooms with non-standard ceilings, etc. the gas boiler output must be increased. It is also necessary to increase the power (about 20-50%) when providing a gas boiler and hot water supply (especially if water heating in the pool is necessary).

The peculiarity of calculating the power of gas boilers: the nominal gas pressure at which the boiler operates at 100% of the power declared by the manufacturer, for most boilers is from 13 to 20 mbar, and the actual pressure in gas networks in Russia can be 10 mbar, and sometimes even lower . Accordingly, a gas boiler often works only at 2/3 of its capacity, and this must be taken into account when calculating. In more detail with a table for calculating the power of a heating boiler, you can

Most gas boilers can transfer from work natural gas for liquefied gas(ballooned propane). Many models switch to liquefied gas at the factory (check these characteristics of the model when purchasing), or nozzles (jets) are additionally supplied to the gas boiler to switch to bottled gas.

Pros and cons of gas boilers:

Boiler piping- These are devices for the full operation of the heating and water supply system. It includes: pumps, expansion tanks, filters (if necessary), collectors, return and safety valves, air valves, valves, etc. You will also need to purchase radiators, connecting pipes and valves, thermostats, a boiler, etc. The issue of choosing a boiler is quite serious, so it is better to entrust the selection of equipment and its complete set to professionals.

What is the best boiler? The Russian market of gas boiler equipment has its own leaders in quality and reliability. The best manufacturing companies and brands of gas boilers are presented in the range:

"Premium" or "Lux"- the most reliable and durable, easy to manage, the kit is assembled as a "constructor", more expensive than the others. These manufacturers include German companies

Fulfilling repair work, which are associated with the replacement of heating equipment, or when designing a heating system for a new house, you must be able to calculate the heat output for the planned heating system. It is this calculation that will make it possible to make a decision that can provide optimal, efficient and economical heating of all housing. How to calculate the power of a gas boiler, and how much information is needed for this, is indicated in this review.

TMK - What is this indicator and how to work with it

However, this value in itself does not give any idea of what area of the premises can be heated using this boiler. It is also not clear how external factors will affect heat consumption, and how much heat will be spent to cover objective heat losses in each specific case.

Taking into account all the circumstances under which the heating system will operate will make it possible to determine which thermal power must be transferred to external devices in order to provide the necessary heat to the owners in the house.

It is necessary to start the calculation with the simplest.

Calculation of the required heat output by area

Preliminary data on the required power of a gas boiler can be obtained by making a simple calculation of the power of a gas boiler by area using the formula:

Boiler power \u003d Heated area (sq.m.) x Boiler specific power / 10

The specific power of a gas boiler (UMK) is a value calculated for each region of Russia, which is:

The obtained MK is relevant for single-circuit boilers that provide only heating.

Thus, if it is necessary to heat a residential building of 100 sq.m. in the Moscow region, then the calculation of the gas boiler for the area of \u200b\u200bthe house will look like this:

100×1.5/10 = 15 kW

But do not rush to look gas boilers fifteen watts. It is necessary to determine the sources of heat loss and the total heat loss of the building or apartment. building codes it is determined that heat losses occur through all the enclosures of the premises (walls, windows, doors, ceilings, floors).

General formula for determining heat loss for building envelopes

Heat loss coefficient = heat transfer coefficient of the enclosure multiplied by the total area of the enclosure and the difference between the room's internal temperature and outdoor temperature environment.

All heat loss and heat transfer coefficients are measured in W / (m.kv * C).
The area of enclosing structures is calculated according to the project.
The lowest possible ambient temperatures for a particular region are published in information guides.
The internal temperature is determined by the order of the customer of the construction or repair work.
Determination of heat loss through walls and ceiling - the table shows the thermal conductivity of the main materials

To calculate the heat loss through the walls and ceiling, it is necessary to determine the coefficient of thermal conductivity building materials, of which these enclosing structures consist, and the thickness of each layer of a certain building material.

To calculate it, you will need the following indicators:

a(vn) is a coefficient that determines the intensity of heat transfer from the internal air in the room to the walls and ceiling. Usually a constant value is taken - 8.7;
a (нр) is a coefficient that determines the intensity of heat transfer from the walls and ceiling to the outside air. Usually a constant value is taken - 23 (for heated rooms).
k - thermal conductivity of building materials from which the walls and ceiling are made;
d - the thickness of each layer of building materials.

The formula for calculating the thermal conductivity coefficient:

The calculation is made separately for the walls and separately for the ceiling.

K (st) - the heat transfer coefficient of glass or double-glazed window determined by the manufacturer;
F(st) - area of glass or double-glazed window;
K(p) - the heat transfer coefficient of the frame determined by the manufacturer;
F(p) - frame area;
P is the perimeter of the glass.

Calculation: K (windows) \u003d K (st) * F (st) + K (p) * F (p) + P / F (windows)

The coefficient of thermal conductivity for doors is also calculated. Only instead of the values for the materials from which the windows are made, the values for the materials from which the doors are made are substituted.

An unheated floor gives a heat loss of approximately 10%, and the calculation is made using the same formula that calculates the heat loss of walls and ceilings. The same formula for calculating the thermal conductivity of the floor.

However, there is a subtlety in the calculation of thermal conductivity for each zone of the floor. There are four zones in total and they are located in the direction of movement from the outer walls to the center of the room.

Average heat loss values for building envelopes

On average, heat loss is determined by:

through windows and doors - up to 50% of heat;
through walls and ceiling - 15%;
through the floor - 10%.

Using the entire amount of information listed, you can independently draw conclusions about the state of thermal insulation of the house and, if necessary, take measures to insulate certain building envelopes.

Having received information about how much heat generated by the gas boiler will go to heat loss, it is necessary to correct the indicator that gave the calculation of the power of the gas heating boiler from the area. To do this, the preliminary power of the boiler is multiplied by the heat loss coefficient - 0.75.

Those who do not have the ability to independently make complex calculations can use the power calculator. However, before calculating the power of a gas boiler with a calculator, it is necessary to make measurements building structures at home (according to current technical plan or directly on the object, using a laser line).

Boiler power selection - video

Calculation of the power of a gas boiler depending on the equipment

There is no such parameter in the heating system that would not affect the determination of the required heat output of a gas boiler:

specifications the boiler itself and heating equipment;
the use of the boiler not only for heating, but also for heating water;
boiler draft type;
type of use of heat of combustion of fuel.

All of the above should be taken into account in the process of finding the answer to the question of how to choose the right gas heating boiler.

Technical characteristics of the boiler and its heat output:

the larger the boiler heat exchanger, the more heat output will be spent on heating the coolant;
depending on what the heat exchanger is made of - cast iron, steel or copper, it is necessary to determine the operating mode of the boiler, since the listed materials have different inertia;
a double-circuit boiler (designed not only for heating, but also for heating water) will take up to 25% of the heat output specifically for hot water supply (hot water supply);
if the working type of boiler draft is forced, then the thermal power of such a boiler is higher than that of a boiler with natural draft;
a condensing gas boiler produces more heat than a convection one, its efficiency is about 110%, respectively, there will be much less loss of rated heat output;
boiler automation must regulate the temperature of the heat carrier and, accordingly, the supplied heat output.

Calculation of the power of a wall and floor gas boiler

For small residential premises or residential buildings, you can choose a wall-mounted gas boiler. These boilers are classified as low-power, but they are much more economical. In addition, the wall-mounted boiler is sold with all accessories: a pump, expansion tank, measuring instruments etc. A complete set of heating equipment provides the least loss of heat produced and the highest efficiency.

Equipment for floor boilers is determined by the designers and purchased separately. With any miscalculations in the project, the entire heating system will malfunction.

How to choose a gas boiler for a cottage

150*1.5/10=22.5kW;

Accounting for the heat loss coefficient can be taken in half of the calculated value, since the maximum indicators were taken for its calculation;

22.5 kW * 0.3 = 6.75 kW;

22.5 kW + 6.75 k. W = 29.25 k. W - the calculated thermal power of the gas boiler.

An important role in calculating the required power of a gas boiler is played by the technical characteristics of pipes and radiators. The slower the coolant cools, the more efficiency all heating system.

Advantages and disadvantages of gas boilers

The boiler is the main part of the heating system. It generates the amount of heat necessary for comfortable conditions and provides hot water. If there is a gas pipeline near the house, the best option will install a gas boiler. It has its pros and cons. Benefits gas equipment are efficiency, high power, ease of operation, medium-sized boilers can be installed even in the kitchen, compact size and environmental friendliness (the boiler emits the least amount of harmful substances into the atmosphere).

The disadvantages of such a boiler are the requirement for a special permit for its installation, the risk of gas leaks, the presence of certain requirements for the room in which the boiler will be located, and the presence automatic shutdown gas leak or insufficient ventilation. In any case, if you decide to install gas heating equipment, you will have a question about how to calculate the power of a gas boiler.

Calculation of a gas boiler: the first method

A correctly calculated boiler power is a guarantee of reliable and effective work heating system. The basis of the calculation is to provide the house with an optimal temperature. Most often, the main source of heat in a house or cottage is the boiler. In order to calculate the necessary parameters and record the data obtained, you will need the following materials and tools:

roulette;
paper, pen;
calculator.

The efficiency of the heating system depends entirely on the power of the boiler. Excessive power leads to excessive fuel consumption, and insufficient power leads to the inability to maintain the desired temperature in the house, especially in winter time of the year. The power of the gas boiler is determined based on the following parameters: the specific power of the unit per 10 m2, taking into account the climatic conditions of a certain region (Wsp), the area of heated premises (S). Specific power, depending on climate zone can take various meanings: 1.2-1.5 kW - for central Russia, 0.7-0.9 - for the southern regions and 1.5-2.0 kW - for the northern regions.
The boiler power is calculated using the formula Wcat = (S * Wsp) / 10. For convenience of calculation, unit is most often taken as specific power. The power is accordingly calculated as 10 kW per 100 m2. Another important parameter is the volume of coolant circulating in the system (Vsyst). When calculating, use the proportion 1 kW: 15 l (unit power: liquid volume. The formula will look like this: Vsyst \u003d Wcat 15

As an example, the calculation of the power of a gas boiler and the required volume of coolant for heating a house of 100 m2 located in the northern region will be given. The maximum specific power for the northern regions is 2 kW, then:

Wcat \u003d 100 2 / 10 \u003d 20 kW;
Vsyst \u003d 20 15 \u003d 300 l.

In order to make the calculation more accurate, you can use a special calculator that also takes into account the desired constant temperature in the house, the lowest average annual temperature, room parameters, wall thickness and material, type of ceilings and number of windows.

Before purchasing a boiler, it is necessary to carefully study its technical characteristics and technical passport.

So you will be sure of its thermal power, because in some cases, instead of the power given to the system, the technical characteristics of the burner may be indicated, which are of no interest to consumers.

The second way to calculate the power of equipment

When choosing a boiler, it is necessary to take into account information about the heat losses of the room, which will need to be compensated. They need to be calculated. This is usually done by the architect who designs the house. Using this data, you can select the boiler of the required power. It is possible to calculate heat losses using special programs with advanced features, with the help of which even those who have never encountered design can make calculations.

If there is no house project and heat loss calculations, they can be determined independently using a simplified calculation method. Questionnaires are accurate enough for small private houses. They contain questions regarding the material and thickness of the walls, the number and size of windows and the type of double-glazed windows. For each question, there are several possible answers. Each answer has its own number.
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The boiler is calculated using these numbers, the result is a value that reflects the heat loss of the house. It is quite suitable for determining the power of the unit. It will take only a few minutes to fill out the questionnaire and make calculations. The simplest method for calculating heat losses is to calculate them using a conditional coefficient having the following values:

from 130 to 200 W / m2 - houses without thermal insulation;
from 90 to 110 W / m2 - houses with thermal insulation, built 20-30 years ago;
from 50 to 70 W / m2 - modern thermally insulated houses with new windows, built in the 21st century.

To determine heat loss, the coefficient is multiplied by the area of the house, however, these calculations are approximate, they do not take into account the number and size of windows, the location and shape of the house, which affect heat loss. This calculation is not the main one when choosing a boiler.
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The calculated heat loss reflects the maximum heat demand of the house, necessary to maintain a normal temperature. The greatest need for heat occurs at temperatures below -22°C. Such frosts usually occur several days a year, and sometimes do not occur at all for several years. And the boiler must work throughout the heating season, when the average temperature is zero. In this case, heating the house will require half the estimated capacity of the equipment. It is not worth buying a boiler of greater power, this leads not only to unnecessary expenses, but also lowers its efficiency. The lack of heat in extreme cold can be compensated by other appliances, such as a fireplace or an electric heater.

Compared to electrical heating appliances, own heating system is more advantageous in terms of cost savings, and in maximum convenience when heating rooms.

The efficiency and profitability of the heating system in the house depends on the correct calculations, adherence to precise rules and instructions.

Calculation of heating by the area of the house is a laborious and complex process. Don't skimp on materials. Quality equipment and its installation affects the financial budget, but then serves the house well and comfortably.

When equipping the house with a heating system, construction works and installation of heating must go strictly according to the project and taking into account all safety regulations for use.

The following points should be taken into account:

house building material,
footage of window openings;
climatic features of the area where the house is located;
location window frames by compass;
what is the device of the "warm floor" system.

Subject to all the above rules and calculations for heating, some knowledge in the field of engineering is required. But there is also a simplified system - the calculation of heating by area, which can be done independently, again, adhering to the rules and complying with all norms.

Choosing a boiler requires an individual approach

If there is gas in the house, then the most the best option- this is gas boiler. In the absence of a centralized gas pipeline, we choose an electric boiler, a heat generator using solid or liquid fuel. Taking into account regional peculiarities, access to the supply of materials, it is possible to install a combined boiler. Combined generator heat will always keep comfortable temperature, in any emergency and force majeure situations. Here you need to start from a simple type of operation, the heat transfer coefficient.

After determining the type of boiler, it is necessary to calculate the heating according to the area of \u200b\u200bthe room. The formula is simple, but it takes into account the temperature of the cold period, the heat loss coefficient for large windows and their location, the thickness of the walls and the height of the ceilings.

Each boiler has a certain power. With the wrong choice, the room will be either cold or excessively hot. Thus, if the specific power of the boiler per 10 cubic meters. taking into account the area of the heated room of 100 sq.m., you can choose the most optimal heat generator.

From the formula used by engineers, Wcat = (SxWsp)/10, kW. – it follows that the boiler with a capacity of 10 kW heats a room of 100 sq.m.

The required number of sections of the heating radiator.

To make it more clear, let's solve the problem using the example of specific numbers. If we assume that room area 14 sq.m. and ceiling height 3 meters, the volume is determined by multiplication.

14 x 3 = 42 cubic meters.

In central Russia, Ukraine, Belarus, thermal power per cubic meter corresponds to 41 W. We determine: 41x 42 \u003d 1722 watts. Found out that for a room of 14 sq.m. need a 1700W heatsink. Each individual section (rib) has a power of 150 watts. By dividing the results obtained, we obtain the number of sections required for the acquisition. The calculation of heating by area is not the same everywhere. For premises over 100 sq.m. required circulation pump installation, which serves as a "forcer" of the movement of the coolant through the pipes. Its installation takes place in the opposite direction from the heating devices to the heat generator. Circulation pump increases the life of the heating system, reducing the contact of hot coolants with appliances.

When installing a heating system warm floor» the coefficient of heating of the house increases many times. Connect system floor heating possible to existing types of heating. A pipe is removed from the heating radiators and floor heating wiring is supplied. This is the most convenient and profitable option, taking into account the savings in time and money.

The basis of any heating system is the boiler. Whether it will be warm in the house depends on how correctly its parameters are selected. And in order for the parameters to be correct, it is necessary to calculate the power of the boiler. These are not the most complex calculations - at the level of the third grade, you will only need a calculator and some data on your possessions. Handle everything yourself, with your own hands.

General points

In order for the house to be warm, the heating system must make up for all the existing heat losses in full. Heat escapes through walls, windows, floor, roof. That is, when calculating the power of the boiler, it is necessary to take into account the degree of insulation of all these parts of an apartment or house. With a serious approach, specialists are ordered to calculate the heat loss of the building, and according to the results, the boiler and all other parameters of the heating system are already selected. This task is not to say that it is very difficult, but it is required to take into account what the walls, floor, ceiling are made of, their thickness and degree of insulation. They also take into account what windows and doors cost, whether there is a system supply ventilation and what is its performance. In general, a long process.

There is a second way to determine heat loss. You can actually determine the amount of heat that a house / room loses with the help of a thermal imager. This is a small device that displays the actual picture of heat loss on the screen. At the same time, you can see where the outflow of heat is greater and take measures to eliminate leaks.

Determination of actual heat losses - an easier way

Now about whether it is worth taking a boiler with a power reserve. In general, the constant operation of the equipment on the verge of capabilities negatively affects its service life. Therefore, it is desirable to have a margin of performance. Small, about 15-20% of the calculated value. It is quite enough to ensure that the equipment does not work at the limit of its capabilities.

Too much stock is unprofitable economically: the more powerful the equipment, the more expensive it is. And the price difference is significant. So, if you are not considering the possibility of increasing the heated area, you should not take a boiler with a large power reserve.

Calculation of boiler power by area

This is the easiest way to choose a heating boiler by power. When analyzing many ready-made calculations, an average figure was derived: for heating 10 square meters area requires 1 kW of heat. This pattern is valid for rooms with a ceiling height of 2.5-2.7 m and medium insulation. If your house or apartment fits these parameters, knowing the area of \u200b\u200byour house, you can easily determine the approximate performance of the boiler.

To make it clearer, we present an example of calculating the power of a heating boiler by area. Available cottage 12 * 14 m. Find its area. To do this, we multiply its length and width: 12 m * 14 m = 168 sq.m. According to the method, we divide the area by 10 and get the required number of kilowatts: 168/10 = 16.8 kW. For ease of use, the figure can be rounded off: the required power of the heating boiler is 17 kW.

Accounting for ceiling heights

But in private homes, ceilings can be higher. If the difference is only 10-15 cm, it can be ignored, but if the ceiling height is more than 2.9 m, you will have to recalculate. To do this, it finds a correction factor (by dividing the actual height by the standard 2.6 m) and multiplies the figure found by it.

Ceiling Height Adjustment Example. The building has a ceiling height of 3.2 meters. It is required to recalculate the power of the heating boiler for these conditions (the parameters of the house are the same as in the first example):

As you can see, the difference is quite significant. If it is not taken into account, there is no guarantee that the house will be warm even at average winter temperatures, and there is no need to talk about severe frosts.

Accounting for the region of residence

Another thing to consider is the location. After all, it is clear that much less heat is required in the south than in middle lane, and for those who live in the north of the "Moscow Region" power will clearly be insufficient. To account for the region of residence, there are also coefficients. They are given with a certain range, since within the same zone the climate still changes a lot. If the house is located closer to the southern border, a smaller coefficient is applied, closer to the north - a larger one. It is also worth considering the presence / absence of strong winds and choose a coefficient taking them into account.

An example of adjustment by zones. Let the house for which we are calculating the power of the boiler be located in the north of the Moscow region. Then the found figure of 21 kW is multiplied by 1.5. Total we get: 21 kW * 1.5 = 31.5 kW.

As you can see, when compared with the original figure obtained when calculating the area (17 kW), obtained as a result of using only two coefficients, it differs significantly. Almost twice. So these parameters must be taken into account.

Power of a double-circuit boiler

Above we talked about calculating the power of the boiler, which works only for heating. If you plan to also heat the water, you need to increase the productivity even more. In calculating the power of the boiler with the possibility of heating water for domestic needs, 20-25% of the reserve is included (multiply by 1.2-1.25).

In order not to have to buy a very powerful boiler, you need a house as much as possible

Example: we adjust for the possibility of hot water supply. The found figure of 31.5 kW is multiplied by 1.2 and we get 37.8 kW. The difference is solid. Please note that the reserve for water heating is taken after the location is taken into account in the calculations - the water temperature also depends on the location.

Features of calculating the performance of the boiler for apartments

The calculation of the boiler power for heating apartments is calculated according to the same norm: 1 kW of heat per 10 square meters. But the correction is going on in other ways. The first thing that needs to be taken into account is the presence or absence of an unheated room above and below.

if another heated apartment is located below / above, a coefficient of 0.7 is applied;
if there is an unheated room below / above, we do not make any changes;
heated basement / attic - coefficient 0.9.

It is also worth considering the number of walls facing the street when calculating. Required in corner apartments large quantity heat:

with one outer wall — 1,1;
two walls face the street - 1.2;
three outer - 1.3.

These are the main areas through which heat escapes. It is imperative to take them into account. You can also take into account the quality of the windows. If these are double-glazed windows, adjustments can not be made. If the old ones are wooden windows, the figure found must be multiplied by 1.2.

You can also take into account such factors as the location of the apartment. In the same way, you need to increase the power if you want to buy a double-circuit boiler (for heating hot water).

Volume calculation

In the case of determining the power of a heating boiler for an apartment, you can use a different method, which is based on the norms of SNiP. They prescribe the norms for heating buildings:

for heating one cubic meter in panel house 41 watts of heat required;
to compensate for heat loss in brick - 34 watts.

To use this method, you need to know the total volume of the premises. In principle, this approach is more correct, since it immediately takes into account the height of the ceilings. A little difficulty may arise here: usually we know the area of \u200b\u200byour apartment. The volume will have to be calculated. To do this, multiply the total heated area by the height of the ceilings. We get the desired volume.

An example of calculating the power of a boiler for heating an apartment. Let the apartment be on the third floor of a five-story building brick house. Her total area 87 sq. m, ceiling height 2.8 m.

Finding volume. 87 * 2.7 = 234.9 cu. m.
Rounding up - 235 cu. m.
We consider the required power: 235 cubic meters. m * 34 W = 7990 W or 7.99 kW.
We round up, we get 8 kW.
Since there are heated apartments above and below, we apply a coefficient of 0.7. 8 kW * 0.7 = 5.6 kW.
Rounding up: 6 kW.
The boiler will also heat domestic water. We will give a margin of 25% for this. 6 kW * 1.25 = 7.5 kW.
The windows in the apartment have not been changed, they are old, wooden. Therefore, we use a multiplying factor of 1.2: 7.5 kW * 1.2 = 9 kW.
Two walls in the apartment are external, so once again we multiply the figure found by 1.2: 9 kW * 1.2 = 10.8 kW.
Rounding up: 11 kW.

In general, here is the method for you. In principle, it can also be used to calculate the power of a boiler for a brick house. For other types of building materials, the norms are not prescribed, and panel a private house- a rarity.