How to calculate the power of a gas boiler

Autonomous heating of a household requires the installation of a heating source. Traditional gas boilers remain in demand, despite the abundance of equipment operating using other resources. This is due to the low price of the gas used and the comfort of use at home.

Boiler power calculation

The initial characteristic of a heat source is power. Depending on the individual operating requirements, the value of this value is selected, which is measured in kilowatts (kW). Manufacturers of heating equipment offer a large selection of models with various parameters to satisfy users of all categories and capabilities. To understand how much power a boiler should have, calculate the amount of thermal energy spent on heating the house and preparing hot water.

With one circuit

To maintain a comfortable temperature in a private home in winter, when there is no need to heat hot water, the calculation of the boiler’s thermal power is based on the characteristics of the building.

A simple calculation of detached buildings uses the square meter measurement, which is multiplied by 0.1 because...the technique assumes the need for 1 kW per 10 sq. m. After this, add 15–20% (for middle latitudes) and take the resulting value as the calculated one. For example, let’s calculate the required amount of heat for a cottage with an area of ​​130 square meters. m:

130x0.1=13 kW;

13+15%=14.95 kW.

We round up and get 15 kW needed to heat a house of 130 square meters. m. This is the power that is selected for the heat source.

The calculation performed is very approximate, since it does not take into account all the factors that affect the required amount of thermal energy. Construction Norms and Rules (SNIP) recommend for middle latitudes to use the calculated value of 41 W, required to heat 1 cubic meter of room. The same regulatory documents regulate the need to use increasing and decreasing coefficients, which depend on the parameters:

• insulation of the facility;
• number of windows, their area;
• method of connecting heating devices;
• required temperature;
• the presence of nearby buildings and structures;
• coolant temperature;
• heat losses.

REFERENCE! Local standards used by construction organizations when carrying out work in the Moscow region recommend using a value of 50 W per 1 cubic meter. m, to calculate the thermal power of separate buildings!

Now let’s calculate the required parameter using building codes. The same house, the ceiling height is 3.2 m. The window openings have an increased area, the walls are insulated with foam plastic, 10 cm thick. First, we calculate the volume: 130x3.2 = 416 cubic meters. m, then multiply by the recommended value for 1 cube: 416x41 = 17056 kW.

Now we apply correction factors regulated by SNIPs:

• insulation – 0.85;
• increase in window openings – 1.05;
• isolation of the building – 1.2.

Now let’s apply it and get: 17056x0.85x1.05x1.2=18.267 kW

We round up to 18.5 and see the difference between the approximate and refined calculation, which is recommended by regulatory documents. Considering that it will not be easy to find a boiler with a capacity of 18.5 or 19 kW, the user will have to make a choice on a 20 kW unit.

Dual-circuit

The peculiarity of using a double-circuit boiler allows you to heat the required room and provide all its residents with heated water, up to 40–45 degrees. In this regard, the calculation of the selected unit becomes more complicated. In addition to the value that makes it possible to maintain a comfortable air temperature, the power required to prepare water that is dispensed at one, two or more points simultaneously is determined.

The preparation of hot water, as well as heating, is influenced by a large number of factors:

• number of water points;
• diameter of water pipes;
• line pressure;
• cold water temperature;
• length of pipelines.

The average value of the required amount of heat to heat water to 40–45 degrees. is 6–8 kW. Owners of gas water heaters in old houses know that their power for two points was 12–16 kW. Using the average value, we calculate the necessary parameters of a double-circuit boiler for a cottage with an area of ​​130 square meters. m.

Let's assume that the cottage has two toilets, a bathroom, a shower and a kitchen. The provision of hot water will be required at three water points. A simple calculation shows: 7x3=21 kW. This is exactly the amount of thermal energy that will be required when three hot water taps are turned on simultaneously.

Now we have two values ​​for determining the boiler power. One for operating the heating circuit and the other for preparing hot water. The correctness of further calculations is based on the principle of operation of dual-circuit equipment.

The specific operation of the unit does not provide for simultaneous heating of two circuits: if the hot water supply is turned on, the automation turns off the heating of the coolant in the heating system and actively heats the water preparation heat exchanger. Therefore, in order to correctly determine the required power of a gas double-circuit boiler, in no case should you add the calculated values. The initial value is a large value, which is taken as the basis when choosing the necessary equipment. In the example considered, this is 21 kW.

ATTENTION! If the calculated parameters differ several times, then all the same, the determining value is the larger value, regardless of whether it was calculated when calculating heating or hot water preparation!

With boiler

Calculation of thermal power for a cottage in which it is planned to install an electric water heater comes down to calculations with a single-circuit boiler. This is due to the absence of the need for a gas heat source to waste energy on preparing hot water. The boiler’s energy will be directed only to maintaining a comfortable temperature in the building.

Why is it necessary to accurately calculate the power of a gas boiler?

The two calculation methods described above for a single-circuit unit show a large difference in values ​​between the rough and refined calculation. It is more correct to use the second method. This will allow you to maintain a comfortable microclimate in the building, in any frost and wind.Using the data from the first calculation will lead to underheating of the building when the outside temperature drops significantly.

Rough calculations used to determine thermal power serve as a guide when choosing a heat source. The choice of equipment based on an approximate calculation will lead to the need to operate the unit at power limits, which will lead to a reduction in the service life of the boiler. To be sure of the accuracy of the calculations made, use all the recommendations of building regulations.

Additional factors taken into account when installing the boiler

When installing a heat source, provision is made for air supply (for closed combustion chambers) and exhaust combustion products removal. Correct installation of a coaxial or simple chimney will rid the room of the accumulation of harmful gases and maintain the required microclimate. To prevent the formation of condensation, the installation of the smoke exhaust duct is carried out in compliance with all necessary rules and regulations.

IMPORTANT! According to the method of installing the heat source, two types of structures are distinguished: wall-mounted or floor-mounted. This factor may affect the interior design of the room in which the unit will be installed.

Is excess power needed?

Some craftsmen, after making a rough calculation, argue that it is necessary to use heating equipment with a power reserve of 1.5-2 times, so as not to make a mistake. The operation of a more powerful heat source will lead to increased gas consumption, especially in the economical mode of maintaining the required coolant temperature. In addition, the cost of the boiler will be an order of magnitude different from a unit with lower power ratings.Purchasing and installing a heat source that corresponds to the calculations made will allow you to use the capabilities of the heating unit more efficiently.

Having studied the power calculation method, the consumer can independently calculate the required boiler parameters for his household and help friends and relatives in resolving this issue.