Mansion heating assembly includes various devices. Heating installation includes thermostats, pressure-increasing pumps, batteries, air vents, expansion tank, fasteners, manifolds, boiler pipes, connection system. On this resource tab we will try to determine specific heating components for the desired dacha. These design elements are undeniably important. Therefore, the matching of each installation element must be done correctly.

In general, the situation is this: they asked to calculate the heating load; I used the formula: max-hour consumption: Q=Vin*qout*(Tin - Tout)*a, and calculated average consumption heat:Q = Qfrom*(Tin.-Ts.r.ot)/(Tin-Tr.from)

Maximum hourly heating consumption:

Qot =(qot * Vn *(tv-tn)) / 1000000; Gcal/h

Qyear = (qot * Vn * R * 24 * (tv-tav))/ 1000000; Gcal/h

where Vн is the volume of the building according to external measurements, m3 (from the technical passport);

R – duration of the heating period;

R =188 (take your own number) days (Table 3.1) [SNB 2.04.02-2000 “Building climatology”];

tav. – average outside air temperature during the heating period;

tav.= - 1.00С (Table 3.1) [SNB 2.04.02-2000 “Building climatology”]

tВ, – average design temperature internal air of heated premises,ºС;

tв= +18ºС – for an administrative building (Appendix A, Table A.1) [Methodology for rationing the consumption of fuel and energy resources for housing and communal services organizations];

tн= –24ºС – design temperature of outside air for heating calculations (Appendix E, Table E.1) [SNB 4.02.01-03. Heating, ventilation and air conditioning”];

qot – average specific heating characteristics of buildings, kcal/m³*h*ºС (Appendix A, Table A.2) [Methodology for rationing the consumption of fuel and energy resources for housing and communal services organizations];

For administrative buildings:

.

We got a result more than twice the result of the first calculation! As practical experience shows, this result is much closer to the real needs for hot water for a 45-apartment residential building.

You can give for comparison the result of the calculation using the old method, which is given in most reference literature.

Option III. Calculation using the old method. Maximum hourly heat consumption for hot water supply needs for residential buildings, hotels and hospitals general type by the number of consumers (in accordance with SNiP IIG.8–62) was determined as follows:

,

Where k h - coefficient of hourly unevenness of hot water consumption, taken, for example, according to table. 1.14 reference book “Adjustment and operation of water heating networks” (see Table 1); n 1 - estimated number of consumers; b - the rate of hot water consumption per consumer, adopted according to the relevant tables of SNiPa IIG.8–62 and for apartment-type residential buildings equipped with bathrooms from 1500 to 1700 mm in length, is 110–130 l/day; 65 - hot water temperature, °C; t x - temperature cold water, °С, accept t x = 5°C.

Thus, the maximum hourly heat consumption for DHW will be equal.

Hello, dear readers! Today is a short post about calculating the amount of heat for heating using aggregated indicators. In general, the heating load is accepted according to the project, that is, the data calculated by the designer is entered into the heat supply contract.

But often such data is simply not available, especially if the building is small, such as a garage, or some kind of utility room. In this case, the heating load in Gcal/h is calculated using the so-called aggregated indicators. I wrote about this. And this figure is already included in the contract as the calculated heating load. How is this figure calculated? And it is calculated according to the formula:

Qot = α*qо*V*(tв-tн.р)*(1+Kн.р)*0.000001; Where

α is a correction factor that takes into account the climatic conditions of the area; it is applied in cases where the estimated outdoor air temperature differs from -30 °C;

qо - specific heating characteristic buildings at tн.р = -30 °С, kcal/cubic m*С;

V is the volume of the building according to external measurements, m³;

tв - design temperature inside the heated building, °C;

tн.р - calculated outside air temperature for heating design, °C;

Kn.r is the infiltration coefficient, which is determined by thermal and wind pressure, that is, the ratio of heat losses by the building with infiltration and heat transfer through external fences at the air temperature outside, which is calculated for heating design.

So, in one formula you can calculate the heat load for heating any building. Of course, this calculation is largely approximate, but it is recommended in the technical literature on heat supply. Heat supply organizations also include this figure for the heating load Qot, in Gcal/h, in heat supply contracts. So the calculation is necessary. This calculation is well presented in the book - V.I. Manyuk, Ya.I. Kaplinsky, E.B. Khizh and others. “Handbook for the setup and operation of water heating networks.” This book is one of my reference books, a very good book.

Also, this calculation of the heat load for heating a building can be done using the “Methodology for determining the amounts of thermal energy and coolant in public water supply systems” of RAO Roskommunenergo of the State Construction Committee of Russia. True, there is an inaccuracy in the calculation in this method (in formula 2 in Appendix No. 1 it is indicated 10 to the minus third power, but it should be 10 to the minus sixth power, this must be taken into account in the calculations), you can read more about this in the comments to this article.

I fully automated this calculation, added reference tables, including a table of climatic parameters for all regions of the former USSR (from SNiP 01/23/99 “Construction Climatology”). You can purchase a calculation in the form of a program for 100 rubles by writing to me by email [email protected].

I will be glad to receive comments on the article.

The first and most important stage in the difficult process of organizing heating of any property (be it Vacation home or industrial facility) is the competent execution of design and calculations. In particular, it is necessary to calculate the thermal load on the heating system, as well as the volume of heat and fuel consumption.

Carrying out preliminary calculations is necessary not only in order to obtain the entire range of documentation for organizing the heating of a property, but also to understand the volumes of fuel and heat, and the selection of one or another type of heat generator.

Thermal loads of the heating system: characteristics, definitions

The definition should be understood as the amount of heat that is collectively given off by heating devices installed in a house or other facility. It should be noted that before installing all the equipment, this calculation is made to eliminate any troubles, unnecessary financial costs and work.

Calculating the heat load on heating will help organize the uninterrupted and efficient operation of the heating system of the property. Thanks to this calculation, you can quickly complete absolutely all heat supply tasks and ensure their compliance with the standards and requirements of SNiP.

The cost of an error in calculation can be quite significant. The thing is that, depending on the received calculation data, the city’s housing and communal services department will highlight maximum consumption parameters, set limits and other characteristics, from which they are based when calculating the cost of services.

General thermal load on modern system heating system consists of several main load parameters:

• On common system central heating;
• Per system underfloor heating(if it is available in the house) – warm floor;
• Ventilation system (natural and forced);
• Hot water supply system;
• For all kinds of technological needs: swimming pools, baths and other similar structures.

Main characteristics of the object that are important to take into account when calculating the heat load

The most correct and competent calculation of the heat load for heating will be determined only if absolutely everything is taken into account, even the most small parts and parameters.

This list is quite large and can include:

• Type and purpose of real estate. Residential or non-residential building, apartment or administrative building - all this is very important for obtaining reliable thermal calculation data.

Also, the load rate determined by heat supply companies and, accordingly, heating costs depend on the type of building;

• Architectural part. The dimensions of all kinds of external fences (walls, floors, roofs), and the sizes of openings (balconies, loggias, doors and windows) are taken into account. The number of floors of the building, the presence of basements, attics and their features are important;
• Temperature requirements for each room in the building. This parameter should be understood as temperature modes for each room of a residential building or area of ​​an administrative building;
• Design and features of external fencing, including the type of materials, thickness, presence of insulating layers;

• The nature of the purpose of the premises. As a rule, it is inherent in industrial buildings, where it is necessary to create certain thermal conditions and regimes for a workshop or site;
• Availability and parameters of special premises. The presence of the same baths, swimming pools and other similar structures;
• Degree Maintenance – availability of hot water supply, such as central heating, ventilation and air conditioning systems;
• Total number of points, from which hot water is drawn. It is this characteristic that you should pay attention to Special attention, because the greater the number of points, the greater the thermal load on the entire heating system as a whole;
• Number of people living in the house or on site. The requirements for humidity and temperature depend on this - factors that are included in the formula for calculating the thermal load;

• Other data. For an industrial facility, such factors include, for example, the number of shifts, the number of workers per shift, as well as working days per year.

As for a private house, you need to take into account the number of people living, the number of bathrooms, rooms, etc.

Calculation of heat loads: what is included in the process

The calculation of the heating load itself is done with your own hands at the design stage country cottage or another piece of real estate - this is due to the simplicity and lack of extra cash costs. This takes into account the requirements various standards and standards, TKP, SNB and GOST.

The following factors are required to be determined during the calculation of thermal power:

• Heat loss from external enclosures. Includes the desired temperature conditions in each room;
• Power required to heat water in the room;
• The amount of heat required to heat the air ventilation (in the case where forced forced ventilation is required);
• Heat needed to heat water in a swimming pool or sauna;

• Possible developments for the further existence of the heating system. This implies the possibility of distributing heating to the attic, basement, as well as all kinds of buildings and extensions;

Advice. Thermal loads are calculated with a “margin” in order to eliminate the possibility of unnecessary financial costs. Especially relevant for country house, where additional connection of heating elements without preliminary design and preparation will be prohibitively expensive.

Features of calculating thermal load

As stated earlier, design parameters indoor air conditions are selected from the relevant literature. At the same time, the selection of heat transfer coefficients is made from the same sources (the passport data of the heating units is also taken into account).

Traditional calculation of thermal loads for heating requires consistent determination of the maximum heat flow from heating devices (all actually located in the building heating batteries), maximum hourly heat energy consumption, as well as total heat power consumption for a certain period, for example, a heating season.

The above instructions for calculating thermal loads taking into account the heat exchange surface area can be applied to various real estate objects. It should be noted that this method allows you to competently and most correctly develop a justification for the use of effective heating, as well as energy inspection of houses and buildings.

An ideal method of calculation for emergency heating of an industrial facility, when it is assumed that temperatures will decrease during non-working hours (holidays and weekends are also taken into account).

Methods for determining thermal loads

Currently, thermal loads are calculated in several main ways:

1. Calculation of heat loss using aggregated indicators;
2. Defining parameters via various elements enclosing structures, additional losses due to air heating;
3. Calculation of the heat transfer of all heating and ventilation equipment installed in the building.

Enlarged method for calculating heating loads

Another method for calculating the load on the heating system is the so-called enlarged method. As a rule, a similar scheme is used in cases where there is no information about projects or such data does not correspond to actual characteristics.

For a larger calculation of the heating heat load, a fairly simple and uncomplicated formula is used:

Qmax from.=α*V*q0*(tв-tн.р.)*10 -6

The formula uses the following coefficients: α is correction factor, taking into account the climatic conditions in the region where the building is built (applied when the design temperature is different from -30C); q0 specific heating characteristic, selected depending on the temperature of the coldest week of the year (the so-called “five-day week”); V – external volume of the building.

Types of thermal loads to be taken into account in the calculation

When performing calculations (as well as when selecting equipment), it is taken into account a large number of a wide variety of thermal loads:

1. Seasonal loads. As a rule, they have the following features:

• Throughout the year, heat loads change depending on the air temperature outside the room;
• Annual heat costs, which are determined by the meteorological characteristics of the region where the object for which the heat loads are calculated is located;

• Changes in the load on the heating system depending on the time of day. Due to the heat resistance of the building’s external enclosures, such values ​​are accepted as insignificant;
• Thermal energy consumption of the ventilation system by hour of the day.

1. Year-round heat loads. It should be noted that for heating and hot water supply systems, most domestic facilities have heat consumption throughout the year, which changes quite little. For example, in summer, thermal energy consumption is reduced by almost 30-35% compared to winter;
2. Dry heat– convection heat exchange and thermal radiation from other similar devices. Determined by dry bulb temperature.

This factor depends on a lot of parameters, including all kinds of windows and doors, equipment, ventilation systems and even air exchange through cracks in the walls and ceilings. The number of people who can be in the room must also be taken into account;

1. Latent heat– evaporation and condensation. Relies on wet bulb temperature. The volume of latent heat of humidity and its sources in the room is determined.

In any room, humidity is influenced by:

• People and their number who are simultaneously in the room;
• Technological and other equipment;
• Air flows that pass through cracks and crevices in building structures.

Regulators of thermal loads as a way out of difficult situations

As you can see in many photos and videos of modern and other boiler equipment, special heat load regulators are included with them. Equipment in this category is designed to provide support for a certain level of loads and eliminate all kinds of surges and dips.

It should be noted that RTN allows you to significantly save on heating costs, because in many cases (and especially for industrial enterprises) certain limits are set that cannot be exceeded. Otherwise, if surges and excesses of thermal loads are recorded, fines and similar sanctions are possible.

Advice. Loads on heating, ventilation and air conditioning systems – important point in home design. If it is impossible to carry out the design work yourself, then it is best to entrust it to specialists. At the same time, all the formulas are simple and uncomplicated, and therefore it is not so difficult to calculate all the parameters yourself.

Ventilation and hot water loads are one of the factors in thermal systems

Thermal loads for heating, as a rule, are calculated in conjunction with ventilation. This is a seasonal load, it is designed to replace exhaust air with clean air, as well as heat it to a set temperature.

Hourly heat consumption for ventilation systems is calculated using a certain formula:

Qv.=qv.V(tn.-tv.), Where

In addition to ventilation itself, the thermal loads on the hot water supply system are also calculated. The reasons for carrying out such calculations are similar to ventilation, and the formula is somewhat similar:

Qgws.=0.042rv(tg.-tx.)Pgav, Where

r, in, tg.,tx. – calculated temperature of hot and cold water, water density, as well as a coefficient that takes into account the values maximum load hot water supply to the average value established by GOST;

Comprehensive calculation of thermal loads

In addition to the theoretical calculation issues themselves, some practical work is also carried out. For example, comprehensive thermal inspections include mandatory thermography of all structures - walls, ceilings, doors and windows. It should be noted that such work makes it possible to identify and record factors that have a significant impact on the heat loss of a building.

Thermal imaging diagnostics will show what the real temperature difference will be when a certain strictly defined amount of heat passes through 1 m2 of enclosing structures. Also, this will help to find out the heat consumption at a certain temperature difference.

Practical measurements are an indispensable component of various calculation works. Taken together, such processes will help obtain the most reliable data on thermal loads and heat losses that will be observed in a certain structure over a certain period of time. Practical calculation will help to achieve what theory will not show, namely the “bottlenecks” of each structure.

Conclusion

Calculation of thermal loads, likewise, is an important factor, the calculations of which must be carried out before starting to organize a heating system. If all the work is done correctly and you approach the process wisely, you can guarantee trouble-free heating operation, as well as save money on overheating and other unnecessary costs.

How to optimize heating costs? This problem can only be solved an integrated approach, taking into account all parameters of the system, building and climatic features region. In this case, the most important component is the thermal load on heating: the calculation of hourly and annual indicators is included in the system for calculating the efficiency of the system.

Why do you need to know this parameter?

What is the calculation of the thermal load for heating? It determines the optimal amount of thermal energy for each room and the building as a whole. The variables are power heating equipment– boiler, radiators and pipelines. Also taken into account heat losses Houses.

Ideally, the thermal output of the heating system should compensate for all heat losses and at the same time maintain a comfortable temperature level. Therefore, before calculating the annual heating load, you need to determine the main factors influencing it:

• Characteristics of the structural elements of the house. Exterior walls, windows, doors, ventilation system affect the level of heat losses;
• Dimensions of the house. It is logical to assume that the larger the room, the more intense the heating system should work. An important factor in this case is not only the total volume of each room, but also the area of ​​the external walls and window structures;
• Climate in the region. With relatively small drops in outside temperature, a small amount of energy is needed to compensate for heat losses. Those. the maximum hourly heating load directly depends on the degree of temperature decrease in a certain period of time and the average annual value for heating season.

Taking these factors into account, the optimal thermal operating conditions of the heating system are compiled. Summarizing all of the above, we can say that determining the thermal load for heating is necessary to reduce energy consumption and maintain the optimal heating level in the premises of the house.

For calculation optimal load For heating based on aggregated indicators, you need to know the exact volume of the building. It is important to remember that this technique was developed for large structures, so the calculation error will be large.

Selecting a calculation method

Before calculating the heating load using aggregated indicators or with higher accuracy, it is necessary to find out the recommended temperature conditions for a residential building.

When calculating heating characteristics, you must be guided by SanPiN 2.1.2.2645-10. Based on the data in the table, in each room of the house it is necessary to ensure optimal temperature regime heating operation.

The methods used to calculate the hourly heating load may have varying degrees of accuracy. In some cases, it is recommended to use fairly complex calculations, as a result of which the error will be minimal. If optimizing energy costs is not a priority when designing heating, less accurate schemes can be used.

When calculating the hourly heating load, you need to take into account the daily change in outside temperature. To improve the calculation accuracy you need to know specifications building.

Easy ways to calculate heat load

Any calculation of the heat load is needed to optimize the parameters of the heating system or improve thermal insulation characteristics Houses. After its implementation, certain methods of regulating the heating heat load are selected. Let's consider non-labor-intensive methods for calculating this parameter of the heating system.

Dependence of heating power on area

For home with standard sizes rooms, ceiling heights and good thermal insulation, you can apply a known ratio of room area to the required thermal power. In this case, 1 kW of heat will need to be generated per 10 m². A correction factor must be applied to the result obtained, depending on the climate zone.

Let's assume that the house is located in the Moscow region. Its total area is 150 m². In this case, the hourly heating load will be equal to:

15*1=15 kW/hour

The main disadvantage of this method is the large error. The calculation does not take into account changes in weather factors, as well as the features of the building - the heat transfer resistance of walls and windows. Therefore, in practice it is not recommended to use it.

Integrated calculation of the thermal load of a building

A larger calculation of the heating load is characterized by more accurate results. Initially, it was used for preliminary calculation of this parameter when it was impossible to determine the exact characteristics of the building. General formula to determine the thermal load for heating is presented below:

Where q°– specific thermal performance buildings. The values ​​must be taken from the corresponding table, A– the correction factor mentioned above, Vn– external volume of the building, m³, Tvn And Tnro– temperature values ​​inside the house and outside.

Suppose we need to calculate the maximum hourly load for heating in a house with a volume along the external walls of 480 m³ (area 160 m², two-storey house). In this case, the thermal characteristic will be equal to 0.49 W/m³*C. Correction factor a = 1 (for the Moscow region). Optimal temperature inside the living space (TV) should be +22°C. The outside temperature will be -15°C. Let's use the formula to calculate the hourly heating load:

Q=0.49*1*480(22+15)= 9.408 kW

Compared to the previous calculation, the resulting value is smaller. However, it takes into account important factors - temperature indoors, outdoors, and the total volume of the building. Similar calculations can be made for each room. The method for calculating the heating load using aggregate indicators makes it possible to determine the optimal power for each radiator in a separate room. For a more accurate calculation, you need to know the average temperature values ​​for a specific region.

This calculation method can be used to calculate the hourly heat load for heating. But the results obtained will not provide an optimally accurate value of the building’s heat losses.

Accurate heat load calculations

But still, this calculation of the optimal heat load for heating does not provide the required calculation accuracy. It does not take into account the most important parameter - the characteristics of the building. The main one is the heat transfer resistance of the material used to manufacture individual elements of the house - walls, windows, ceilings and floors. They determine the degree of conservation of thermal energy received from the coolant of the heating system.

What is heat transfer resistance ( R)? This is the reciprocal of thermal conductivity ( λ ) – the ability of the material structure to convey thermal energy. Those. The higher the thermal conductivity value, the higher the heat losses. This value cannot be used to calculate the annual heating load, since it does not take into account the thickness of the material ( d). Therefore, experts use the heat transfer resistance parameter, which is calculated using the following formula:

Calculation of walls and windows

There are standardized values ​​for the heat transfer resistance of walls, which directly depend on the region where the house is located.

In contrast to the enlarged calculation of the heating load, you first need to calculate the heat transfer resistance for the external walls, windows, ground floor floor and attic. Let's take the following characteristics of the house as a basis:

• Wall area – 280 m². It includes windows - 40 m²;
• The wall material is solid brick ( λ=0.56). Thickness of external walls – 0.36 m. Based on this, we calculate the TV transmission resistance - R=0.36/0.56= 0.64 m²*C/W;
• For improvement thermal insulation properties external insulation was installed - thick polystyrene foam 100 mm. For him λ=0.036. Respectively R=0.1/0.036= 2.72 m²*C/W;
• General value R for external walls it is equal 0,64+2,72= 3,36 which is a very good indicator of the thermal insulation of a house;
• Window heat transfer resistance – 0.75 m²*S/W(double glass with argon filling).

In fact, heat losses through the walls will be:

(1/3.36)*240+(1/0.75)*40= 124 W at a temperature difference of 1°C

We will take the same temperature indicators as for the aggregate calculation of the heating load +22°C indoors and -15°C outdoors. Further calculations must be made using the following formula:

124*(22+15)= 4.96 kW/hour

Ventilation calculation

Then it is necessary to calculate the losses through ventilation. The total air volume in the building is 480 m³. Moreover, its density is approximately 1.24 kg/m³. Those. its mass is 595 kg. On average, air is renewed five times per day (24 hours). In this case, to calculate the maximum hourly heating load, you need to calculate the heat losses for ventilation:

(480*40*5)/24= 4000 kJ or 1.11 kW/hour

By summing up all the obtained indicators, you can find the total heat loss of the house:

4.96+1.11=6.07 kW/hour

This way the exact maximum heating load is determined. The resulting value directly depends on the outside temperature. Therefore, to calculate the annual load on heating system changing weather conditions must be taken into account. If the average temperature during the heating season is -7°C, then the total heating load will be equal to:

(124*(22+7)+((480*(22+7)*5)/24))/3600)*24*150(heating season days)=15843 kW

By changing the temperature values, you can make an accurate calculation of the heat load for any heating system.

To the results obtained, you need to add the value of heat losses through the roof and floor. This can be done by a correction factor of 1.2 - 6.07 * 1.2 = 7.3 kW/h.

The resulting value indicates the actual energy costs during system operation. There are several ways to regulate the heating load. The most effective of them is reducing the temperature in rooms where there is no constant presence of residents. This can be done using thermostats and installed sensors temperature. But at the same time, a two-pipe heating system must be installed in the building.

To calculate the exact value of heat losses, you can use the specialized Valtec program. The video shows an example of working with it.

To find out how much power the thermal power equipment of a private home should have, you need to determine total load on the heating system, for which thermal calculations are performed. In this article we will not talk about the enlarged method of calculating the area or volume of a building, but will present a more accurate method used by designers, only in a simplified form for better perception. So, the heating system of a house is subject to 3 types of loads:

• compensation for losses of thermal energy passing through building construction(walls, floors, roof);
• heating the air required for ventilation of premises;
• heating water for DHW needs(when a boiler is involved and not a separate heater).

Determination of heat loss through external fences

To begin with, let’s present the formula from SNiP, which is used to calculate the thermal energy lost through building structures separating the interior of the house from the street:

Q = 1/R x (tв – tн) x S, where:

• Q – heat consumption passing through the structure, W;
• R – resistance to heat transfer through the fencing material, m2ºС / W;
• S – area of ​​this structure, m2;
• tв – temperature that should be inside the house, ºС;
• tн – average street temperature for the 5 coldest days, ºС.

For reference. According to the methodology, heat loss calculations are performed separately for each room. In order to simplify the problem, it is proposed to take the building as a whole, assuming an acceptable average temperature of 20-21 ºС.

The area for each type of external fencing is calculated separately, for which windows, doors, walls and floors with roofing are measured. This is done because they are made from different materials of various thicknesses. So the calculation will have to be done separately for all types of structures, and the results will then be summed up. You probably know the coldest street temperature in your area of ​​residence from practice. But the parameter R will have to be calculated separately using the formula:

R = δ / λ, where:

• λ – thermal conductivity coefficient of the fencing material, W/(mºС);
• δ – material thickness in meters.

Note. The value of λ is for reference, it is not difficult to find in any reference literature, and for plastic windows Manufacturers will tell you this coefficient. Below is a table with the thermal conductivity coefficients of some building materials, and for calculations it is necessary to take the operational values ​​of λ.

As an example, let's calculate how much heat 10 m2 will lose brick wall 250 mm thick (2 bricks) with a temperature difference between outside and inside the house of 45 ºС:

R = 0.25 m / 0.44 W/(m ºС) = 0.57 m2 ºС / W.

Q = 1/0.57 m2 ºС / W x 45 ºС x 10 m2 = 789 W or 0.79 kW.

If the wall consists of different materials (structural material plus insulation), then they must also be calculated separately using the above formulas, and the results must be summed up. Windows and roofing are calculated in the same way, but with floors the situation is different. The first step is to draw a plan of the building and divide it into zones 2 m wide, as shown in the figure:

Now you should calculate the area of ​​each zone and substitute it into the main formula one by one. Instead of parameter R, you need to take the standard values ​​for zones I, II, III and IV, indicated in the table below. At the end of the calculations, we add up the results and get total losses heat through the floors.

Consumption for heating ventilation air

Uninformed people often do not take into account that the supply air in the house also needs to be heated and this heat load also falls on the heating system. Cold air still enters the house from the outside, whether we like it or not, and it takes energy to heat it. Moreover, a private home must have a full-fledged supply and exhaust ventilation, usually with a natural impulse. Air exchange is created due to the presence of draft in ventilation ducts and the boiler chimney.

The method for determining the heat load from ventilation proposed in the regulatory documentation is quite complex. Quite accurate results can be obtained if you calculate this load using the well-known formula through the heat capacity of the substance:

Qvent = cmΔt, here:

• Qvent – ​​amount of heat required to heat the supply air, W;
• Δt – temperature difference outside and inside the house, ºС;
• m – mass of the air mixture coming from outside, kg;
• c – heat capacity of air, assumed to be 0.28 W / (kg ºС).

The difficulty in calculating this type of heat load lies in correctly determining the mass of the heated air. Find out how much of it gets inside the house, when natural ventilation difficult. Therefore, it is worth turning to the standards, because buildings are built according to designs that include the required air exchanges. And the standards say that in most rooms the air environment should change once an hour. Then we take the volumes of all rooms and add to them the air flow rates for each bathroom - 25 m3/h and kitchen gas stove– 100 m3/h.

To calculate the heat load for heating from ventilation, the resulting volume of air must be converted into mass, having found out its density at different temperatures from the table:

Let's assume that the total amount of supply air is 350 m3/h, the temperature outside is minus 20 ºС, inside – plus 20 ºС. Then its mass will be 350 m3 x 1.394 kg/m3 = 488 kg, and the thermal load on the heating system will be Qvent = 0.28 W / (kg ºС) x 488 kg x 40 ºС = 5465.6 W or 5.5 kW.

Thermal load from heating water for domestic hot water supply

To determine this load, you can use the same simple formula, only now you need to calculate the thermal energy spent on heating the water. Its heat capacity is known and is 4.187 kJ/kg °C or 1.16 W/kg °C. Considering that a family of 4 people needs only 100 liters of water for 1 day, heated to 55 °C, we substitute these numbers into the formula and get:

QDHW = 1.16 W/kg °C x 100 kg x (55 – 10) °C = 5220 W or 5.2 kW of heat per day.

Note. By default, it is assumed that 1 liter of water is equal to 1 kg, and the temperature is cold tap water equal to 10 °C.

A unit of equipment power is always referred to 1 hour, and the resulting 5.2 kW is referred to a day. But you cannot divide this figure by 24, because hot water we want to receive it as quickly as possible, and for this the boiler must have a reserve of power. That is, this load must be added to the rest as is.

Conclusion

This calculation of home heating loads will give much more accurate results than traditional way in terms of area, although you will have to work hard. Final result it is necessary to multiply by the safety factor - 1.2, or even 1.4 and select according to the calculated value boiler equipment. Another method of enlarged calculation of thermal loads according to standards is shown in the video: