How to calculate the boiler output by area

Calculating the capacity for a two-circuit boiler

The above calculations were made for a device that provides only heating. When you need to make a calculation of the capacity of the gas boiler for the house, which will simultaneously heat water for household needs, its capacity needs to be increased. This also applies to units running on other fuels.

When determining the capacity of the heating boiler with the possibility of heating water, you need to build a margin of 20-25%, applying a coefficient of 1.2-1.25.

For example, you need to make an adjustment for DHW. Previously calculated result of 27 kW multiply by 1.2 and receive 32.4 kW. The difference turns out quite a lot.

You must remember how to correctly calculate the boiler power. The reserve for heating water is applied after taking into account the region where the house is located, because the temperature of the fluid also depends on the location of the object.

How the boiler output depends on the area. how to calculate correctly

In most cases, use the approximate calculation of thermal capacity of the boiler unit on the heating area, for example, for a private home:

Such calculations may be suitable for a not very large building with an insulated attic floor, low ceilings, good thermal insulation, double glazed windows, but no more than that.

According to the old calculations it is better not to do. Source

Unfortunately, these conditions correspond only to a small number of buildings. In order to carry out the most thorough calculation of the boiler output indicator, it is necessary to consider a complete package of interrelated values, including:

  • atmospheric conditions in the area;
  • The size of the residential building;
  • thermal conductivity coefficient of the wall;
  • the actual thermal insulation of the building;
  • The system of regulating the power of the gas boiler;
  • amount of heat required for DHW.

Calculation of a single-circuit heating boiler

Calculation of the capacity of a single-circuit boiler wall or floor modification of the boiler, using the ratio: 10 kW per 100 m2, you need to increase by 15-20%.

For example, it is necessary to heat a building with an area of 80 m2.

Calculation of the capacity of the gas heating boiler:

In the case where the trade network does not exist the required type of device, buy a modification with a larger size of the kW. Such a method is suitable for single-circuit heating sources, without the load on the hot water supply, and can be the basis for calculating the gas consumption for the season. Sometimes, instead of the living space, the calculation is carried out taking into account the volume of the apartment building and the degree of insulation.

For individual premises built on a typical project, with a ceiling height of 3 m, the formula for calculating quite simple.

In this option, the built-up area (B) and the boiler unit specific capacity factor (UHC), depending on the climatic location of the object are taken into account.

Consequently, the formula for calculation is as follows: Mo=PUMK/10

For example, the required capacity of the heating source for a building of 80 m2, located in the northern region:

If the owner will install a two-circuit boiler unit, for heating and DHW, professionals advise to add to the obtained result another 20% of power to heat water.

How to calculate the capacity of the boiler

The calculation of the heat output of a two-circuit boiler unit is performed on the basis of this proportion:

10 m2 = 1,000 W 20% (heat loss) 20% (DHW heating).

If the building has an area of 200 m2, the required size will be: 20.0 kW 40.0% = 28.0 kW

This is an estimate and is best clarified by the HTW consumption per person. Such data is given in SNIP:

In the technical documentation to the water heater specifies what heat output of the boiler is needed to ensure quality heating of water.

For a heat exchanger for 200 liters will be sufficient heater load of approximately 30.0 kW. Then calculate the output sufficient for heating, at the end of the calculation add up.

Calculation of the capacity of the indirect heating boiler

In order to balance the required capacity of a single-circuit unit operating on gas fuel with a boiler of indirect heating, you need to establish how much heat exchanger will be needed to provide hot water for the occupants of the house. Using the data on the norms of hot water consumption can easily be established that the flow rate per day for a family of 4 people is 500 liters.

Performance of the indirect water heater directly depends on the area of the internal heat exchanger, the larger the size of the coil, the more heat energy it transfers to water per hour. You can detail such information by studying the characteristics on the passport of the equipment.

There are optimal ratios of these values for the average power range of indirect heating boilers and the time to obtain the desired temperature:

When choosing a water heater, it is recommended that it heats water in about half an hour. Based on these requirements, the 3rd variant of BKN is preferable.

Calculation of the power of the gas boiler depending on the area of the house

Using the coefficient of the specific heat capacity provides the fastest way to determine the parameters of the equipment. Multiplying the standard heat loss of 1 m² by the total area to be heated gives the desired value. Depending on the building technology and climate zones, the average space heat consumption is assumed to be 100 W/m² or 1 kW per 10 m². If the building parameters deviate from the standard, domestic hot water requirements, the capacity of the gas appliances must be recalculated.

The value of the average heat loss per square meter of surface varies depending on the climate, the regional coefficient is:

  • 0.7. 0.9 for southern regions;
  • 1.0 to 1.15 in the Russian midlands;
  • 1,2-1,5 for Moscow region.;
  • 1.5. 2.0 for areas beyond the Arctic Circle.

For a single-circuit boiler

A simplified calculation of the output of a 1-circuit boiler, in the floor-standing or wall-mounted version, is based on the coefficient 1 m² = 100 W of energy. This value is increased by 20% to create a reserve of. If necessary, a correction factor for the climatic zone can be applied. So, for a house area of 100 m² will need a boiler 12 kW = 10 kW 2 kW. The calculations do not include the DHW system, underfloor heating and other heat consumers.

For a two-circuit boiler

When designing a heating system, do not get carried away with excessive accuracy of calculations. On the question of how to calculate the capacity of a gas boiler with 2 circuits, there will be no difficulties if you apply the standard method. To know the exact temperature of the rooms, using a simplified method, is problematic. It only allows you to determine how much power reserve should be to provide heat to all consumers.


The heating energy is calculated with the ratio of 1 m² = 100 W. Add 20% to this value and an additional 20% to increase the water temperature. For a 100 square meter house, the required output of the split-circuit heater is 10 kW 2 kW = 14 kW.

For the boiler

First, the maximum flow of hot water, which is calculated by summing the performance of each point of water intake:

From the manual to the boiler determines the boiler capacity and volume of the hot water tank. For these figures you need a 200 liter storage tank and 30 kW heater. This value is added to the heating output and deducted by 20% P0 = (P(boiler)P(boiler)-20%. This results in a total P0 value for the system as a whole.

What factors should be considered when calculating the boiler output?

Possible points of heat loss in a private house

  • All these construction elements or technical equipment keep the heat in the rooms differently, but each of them gives a certain percentage of heat losses, depending on the material of their construction.
  • An important role in the calculations also plays the difference between the air temperature in the rooms of the dwelling and outside the building, the lower on the outside of the building, the faster the house cools down.
  • Also take into account the average winter temperature in the region where the building is located.
  • If the boiler is not only designed for heating, but also for water heating, this factor must also be taken into account in the calculations.

In the calculations, all loads on the boiler are taken into account

Armed with such figures, you can make a calculation and determine the output of the boiler in different ways.

Approximate selection of the boiler

For example, for heating a dwelling with a total area of 350 m2, located in the Moscow region, the calculation will be as follows: W = S Wud/10 = 350 1.35/10 = 47.25 kW. In the example, the resulting figure should be rounded, it turns out that the device should be chosen with a capacity of about 50 kW.

Another example. Determination of the power for a house with an area of 230 m2, located in the north of Russia: W = S W ud/10 = 230 1.7/10 = 39.1 kW. In this case you have to select the motor on the basis of 39.1 kW, which in rounding will be 40, but it is necessary to take a power reserve, so it is possible to apply 43.

The calculation is simple and does not require any professional knowledge. You just need to consider the initial parameters of the room, take the correct value of specific power W o ue relative to the climate zone.

Nuances in determining the capacity of the boiler for apartments

The value of 10 m2 / 1 kW of heat is also used for the calculation of the boiler output in apartments. Other parameters are needed for adjustment here. The first thing to take into account is whether there are unheated rooms above or below.

The algorithm for further action, how to calculate the boiler for the house:

  • If there is a cold room downstairs or upstairs need to apply a coefficient of 0.7.
  • If there is no other unheated apartment, the result is left uncorrected.
  • The presence of a heated basement or attic provides for the use of a coefficient of 0.9.

During the calculations, walls that face the street are also taken into account.

Corner rooms need more heat:

These areas which must be taken into account are the areas through which the greatest amount of heat is lost. Sometimes the number of windows is taken into account. If we are talking about modern double-glazed windows, there is no correction. The presence of old wood products requires the use of a coefficient of 1.2. The way in which the apartment is located also has a certain value. Exactly the same increase in power requires the use of a two-circuit boiler for DHW.

Calculation of the capacity of the solid fuel boiler

Solid fuel boilers are used much less frequently than electric or gas boilers. They are characterized by affordability, possibility of independent operation, economical operation, the need for space for fuel storage.

A distinctive feature that should be considered when determining the capacity of solid fuel boilers, is the cyclicality of the resulting temperature. The daily temperature in the heated room varies within 5ºC. If there is no possibility to refuse such a system, there are two ways how to maintain a stable temperature in the room: the use of a thermobalance and the use of water heat accumulators.

Thermal balloon serves to regulate the air supply, which allows you to increase the burning time and reduce the number of burns. Water thermal accumulators of 2 to 10 square meters are installed in the heating system, reduce energy costs and save fuel. All these measures help to reduce the required capacity of a solid fuel boiler for heating a private house. The effect of these measures should be considered when determining the capacity of heating equipment.

Calculation of boiler output by area of the house

Autonomous heating system involves special equipment, the power of the boiler is not less important than the fuel on which it will operate. There are devices on liquid, solid fuel, gas and with a direct connection to the power grid.

Regardless of the type of device to achieve maximum comfort in the rooms in winter, it is necessary to make correct calculations. If you miss it, you will not get a good temperature, some nuances will also lead to an increase in equipment costs, I want to give effective advice on this and help avoid fatal errors after starting the system.

Calculating the capacity of heating boilers for private homes

The comfort of people staying indoors, especially in winter, largely depends on the temperature of the air around them. Therefore, among the utilities to be installed in residential areas, the heating system takes first place. In urban conditions, heating of apartments is often centrally controlled, but in private houses, owners have to equip independent heating system, the main element of which is a hot water boiler. It is from the technical and economic characteristics of the latter depends on the efficiency of the entire system.

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