A well-arranged heating system will provide housing with the necessary temperature and will be comfortable in all rooms in any weather. But in order to transfer heat to the airspace of residential premises, you need to know the required number of batteries, right?
To find out this will help the calculation of heating radiators, based on calculations of the thermal power required from the installed heating devices.
Have you ever done such calculations and are afraid to make a mistake? We will help to deal with formulas - the article considers a detailed calculation algorithm, analyzes the values of individual coefficients used in the calculation process.
To make it easier for you to understand the intricacies of the calculation, we have selected thematic photo materials and useful videos that explain the principle of calculating the power of heating devices.
Simplified calculation of heat loss compensation
Any calculations are based on certain principles. The calculation of the required thermal power of the batteries is based on the understanding that well-functioning heating devices must completely compensate for the heat loss that occurs during their operation due to the characteristics of the heated rooms.
For living rooms located in a well-insulated house, located, in turn, in a temperate climate zone, in some cases a simplified calculation of compensation for heat leaks is suitable.
For such premises, calculations are based on a standard power of 41 W, which is required for heating 1 cubic meter. living space.
In order for the thermal energy emitted by heating devices to be directed specifically to space heating, it is necessary to insulate walls, attics, windows and floors
The formula for determining the thermal power of radiators necessary to maintain optimal living conditions in a room is as follows:
Q = 41 x V,
Where V - the volume of the heated room in cubic meters.
The obtained four-digit result can be expressed in kilowatts, reducing it at the rate of 1 kW = 1000 watts.
Detailed formula for calculating thermal power
In detailed calculations of the number and size of heating batteries, it is customary to start from a relative power of 100 W, which is necessary for normal heating of 1 m² of a certain standard room.
The formula for determining the heat output required from heating appliances is as follows:
Q = (100 x S) x R x K x U x T x H x W x G x X x Y x Z
Factor S in calculations, it is nothing but the area of a heated room, expressed in square meters.
The remaining letters are various correction factors, without which the calculation will be limited.
The main thing in thermal calculations is to remember the saying “heat does not break bones” and not be afraid to make a big mistake
But even additional design parameters can not always reflect the specifics of a room. If in doubt in the calculations, it is recommended to give preference to indicators with large values.
It is easier then to lower the temperature of the radiators using thermostatic devices than to freeze when there is a lack of thermal power.
Next, each of the coefficients involved in the calculation of the thermal power of the batteries is analyzed in detail.
At the end of the article, information is given on the characteristics of collapsible radiators from different materials, and the procedure for calculating the required number of sections and the batteries themselves is examined based on the basic calculation.
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A simplified method for calculating the power of radiators required for normal room heating, assumes that for every 10 m3 you need to deliver 1 kW of heat
In order for the owners of the premises to have a reserve in case of unexpected heat losses, the calculated power value is multiplied by 1.15, i.e. increase by 15%
Compact radiators used in low-temperature heating circuits are effective no less than traditional appliances. Their power is calculated according to a similar scheme.
If the room is bounded by two external walls and it has one window, the calculated value of the thermal power must be increased by 20%
The power of the heating system appliance installed in the room with access to the terrace or the winter garden needs to be increased by 25%
For a room with one external wall and one window, the heater power should be multiplied by a correction factor of 1.15
If the heating battery is masked by a box or screen, then its power is increased by 15 - 20% depending on the heat-conducting characteristics of the material of which the structure is made
When calculating the performance of radiators for the attic with widescreen panoramic windows, the result is increased by 25 - 35%
Average heat output of radiators
Stock of thermal power of devices
Low-temperature compact radiators in the interior
Radiators in a room with two external walls
Indoor heating devices with terrace
Installing the battery in a corner room
Calculations for a box-closed radiator
Attic heating device
Orientation of rooms to the cardinal points
And on the coldest days, the energy of the sun still affects the thermal balance inside the home.
The coefficient “R” of the formula for calculating heat power depends on the direction of the rooms in one direction or another.
- Room with a window to the south - R = 1,0. During daylight hours, it will receive maximum additional external heat compared to other rooms. This orientation is taken as the base, and the additional parameter in this case is minimal.
- The window faces west - R = 1,0 orR = 1.05 (for areas with a short winter day). This room will also have time to get its portion of sunlight. The sun, though, will glance there in the late afternoon, but still the location of such a room is more advantageous than the eastern and northern ones.
- The room is oriented to the east - R = 1,1. The rising winter luminary is unlikely to have time to properly heat such a room from the outside. Battery power will require extra watts. Accordingly, we add to the calculation a tangible correction of 10%.
- Outside the window is only the north - R = 1,1 or R = 1.15 (a resident of the northern latitudes will not be mistaken, who will take an additional 15%). In winter, such a room does not see direct sunlight at all. Therefore, it is recommended that the calculations of the thermal return required from radiators be also adjusted by 10% upwards.
If winds of a certain direction prevail in the area of residence, it is advisable for rooms with windward sides to increase R up to 20% depending on the strength of the blow (x1.1 ÷ 1.2), and for rooms with walls parallel to cold flows, raise the value of R by 10% (x1.1).
Premises oriented to the north and east, as well as rooms on the windward side, will require more powerful heating.
Taking into account the influence of external walls
In addition to the wall with a window or windows built into it, other walls of the room may also have contact with the outside cold.
The external walls of the room determine the coefficient "K" of the calculated formula for the thermal power of radiators:
- The presence of one street wall in a room is a typical case. Everything is simple with the coefficient - K = 1,0.
- Two external walls will request 20% more heat to heat the room - K = 1,2.
- Each subsequent outer wall adds 10% of the required heat transfer to the calculations. For three street walls - K = 1.3.
- The presence of four external walls in the room also adds 10% - K = 1.4.
Depending on the characteristics of the room for which the calculation is carried out, it is necessary to take the corresponding coefficient.
The dependence of radiators on thermal insulation
To reduce the budget for heating the internal space allows competently and reliably isolated from the winter cold housing, and significantly.
The degree of insulation of street walls obeys the coefficient "U", which reduces or increases the estimated thermal power of heating devices:
- U = 1,0 - for standard external walls.
- U = 0.85 - if the insulation of street walls was carried out according to a special calculation.
- U = 1.27 - if the external walls are not sufficiently cold-resistant.
Walls made of climate-friendly materials and thickness are considered standard. As well as reduced thickness, but with a plastered outer surface or with a surface outer insulation.
If the area permits, then you can warm the walls from the inside. And to protect the walls from the cold outside there is always a way.
A well-insulated corner room according to special calculations will give a significant percentage of the cost savings for heating the entire living area of the apartment
Climate is an important factor in arithmetic
Different climatic zones have different indicators of minimally low street temperatures.
When calculating the heat transfer power of radiators, a coefficient “T” is provided for taking into account temperature differences.
Consider the values of this coefficient for various climatic conditions:
- T = 1.0 to -20 ° C.
- T = 0.9 for winters with frost up to -15 ° С
- T = 0.7 - up to -10 ° С.
- T = 1,1 for frosts up to -25 ° С,
- T = 1.3 - up to -35 ° C,
- T = 1.5 - below -35 ° C.
As you can see from the list above, winter weather is considered normal to -20 ° C. For areas with such the least cold take a value of 1.
For warmer regions, this calculated coefficient will lower the overall result of the calculations. But for areas of harsh climate, the amount of heat required from heating appliances will increase.
Features calculation of high rooms
It is clear that out of two rooms with the same area, more heat will be required for the one with a higher ceiling. Factor “H” helps to take into account the correction for the volume of heated space in the calculations of thermal power.
At the beginning of the article, a certain normative premise was mentioned. Such is considered a room with a ceiling at a level of 2.7 meters and below. For her, take the value of the coefficient equal to 1.
Consider the dependence of the coefficient N on the height of the ceilings:
- H = 1.0 - for ceilings of 2.7 meters high.
- H = 1.05 - for rooms up to 3 meters high.
- H = 1,1 - for a room with a ceiling up to 3.5 meters.
- H = 1.15 - up to 4 meters.
- H = 1.2 - The need for heat for a higher room.
As you can see, for rooms with high ceilings, 5% should be added to the calculation for every half meter of height, starting from 3.5 m.
According to the law of nature, warm, heated air rushes up. To mix its entire volume, the heating devices will have to work hard.
With the same room area, a larger room may require an additional number of radiators connected to the heating system
The estimated role of the ceiling and floor
Not only well-insulated external walls lead to a decrease in the thermal power of batteries. A ceiling in contact with a warm room also helps to minimize losses when heating a room.
The coefficient "W" in the calculation formula is just in order to provide for this:
- W = 1.0 - if located at the top, for example, an unheated uninsulated attic.
- W = 0.9 - for an unheated, but insulated attic or other insulated room from above.
- W = 0.8 - if the floor above the room is heated.
The W indicator can be adjusted upwards for the premises of the first floor, if they are located on the ground, above an unheated basement or basement. Then the numbers will be as follows: the floor is insulated + 20% (x1,2); the floor is not insulated + 40% (x1.4).
Frame quality is the key to heat
Windows - once a weak spot in the insulation of living space.Modern frames with double-glazed windows have significantly improved the protection of rooms from street cold.
The degree of quality of windows in the formula for calculating thermal power describes the coefficient "G".
The calculation is based on a standard frame with a single-chamber double-glazed window, in which the coefficient is 1.
Consider other options for applying the coefficient:
- G = 1.0 - frame with single-chamber double-glazed window.
- G = 0.85 - if the frame is equipped with a two- or three-chamber double-glazed window.
- G = 1.27 - if the window has an old wooden frame.
So, if the house has old frames, then the heat loss will be significant. Therefore, more powerful batteries will be required. Ideally, it is advisable to replace such frames, because these are additional heating costs.
Window size matters
Following the logic, it can be argued that the larger the number of windows in the room and the wider their overview, the more sensitive heat leakage through them. The coefficient "X" from the formula for calculating the thermal power required by the batteries, just reflects this.
In a room with huge windows and radiators should be out of the number of sections corresponding to the size and quality of the frames
The norm is the result of dividing the area of window openings by the area of the room equal from 0.2 to 0.3.
Here are the main values of the coefficient X for various situations:
- X = 1.0 - with a ratio of 0.2 to 0.3.
- X = 0.9 - for the area ratio from 0.1 to 0.2.
- X = 0.8 - with a ratio of up to 0.1.
- X = 1.1 - if the area ratio is from 0.3 to 0.4.
- X = 1.2 - when it is from 0.4 to 0.5.
If the footage of window openings (for example, in rooms with panoramic windows) goes beyond the proposed ratios, it is reasonable to add another 10% to the X value with an increase in the area ratio by 0.1.
The door located in the room, which is regularly used in winter to access the open balcony or loggia, makes its own amendments to the heat balance. For such a room, it will be correct to increase X by another 30% (x1.3).
Loss of thermal energy is easily compensated by a compact installation under the balcony entrance of a channel water or electric convector.
The effect of battery closure
Of course, the radiator that is less fenced by various artificial and natural obstacles will give better heat. In this case, the formula for calculating its thermal power is expanded due to the coefficient "Y", taking into account the operating conditions of the battery.
The most common location for radiators is under the windowsill. With this position, the coefficient value is 1.
Consider typical situations for placing radiators:
- Y = 1.0 - immediately under the windowsill.
- Y = 0.9 - if the battery is suddenly completely open from all sides.
- Y = 1.07 - when the radiator is blocked by a horizontal ledge of the wall
- Y = 1.12 - if the battery located under the window sill is covered by the front casing.
- Y = 1.2 - when the heater is blocked on all sides.
The shifted long blackout curtains also cause a cooling in the room.
The modern design of the heating batteries allows you to operate them without any decorative covers - thereby ensuring maximum heat transfer
Radiator Connectivity
The efficiency of its operation directly depends on the method of connecting the radiator to the indoor heating wiring. Often, homeowners sacrifice this indicator for the sake of the beauty of the room. The formula for calculating the required heat capacity takes into account all this through the coefficient "Z".
We give the values of this indicator for various situations:
- Z = 1.0 - the inclusion of a radiator in the overall circuit of the heating system by the reception "diagonally", which is the most justified.
- Z = 1.03 - the other, the most common due to the small length of the eyeliner, the connection option "from the side."
- Z = 1.13 - The third method is “from below on two sides.” Thanks to plastic pipes, it was he who quickly took root in the new construction, despite much less efficiency.
- Z = 1.28 - Another, very low-efficient method "from the bottom on the one hand." It deserves consideration only because some designs of radiators are supplied with ready-made units with connection to a single point of the pipe and supply and return.
To increase the efficiency of heating devices will help the air vents installed in them, which will save the system from “airing” in a timely manner.
Before you hide the heating pipes on the floor, using ineffective battery connections, it is worth remembering about the walls and ceiling
The principle of operation of any water heater is based on the physical properties of a hot liquid rising up, and after cooling down.
Therefore, it is strongly discouraged to use the connections of heating systems to radiators, in which the supply pipe is at the bottom and the return pipes at the top.
A practical example of calculating thermal power
Initial data:
- Corner room without a balcony on the second floor of a two-story cinder block plastered house in a calm area of Western Siberia.
- Room length 5.30 m X width 4.30 m = area 22.79 sq.m.
- Window width 1.30 m X height 1.70 m = area 2.21 sq.m.
- Room height = 2.95 m.
Calculation Sequence:
Room area in sq.m .: | S = 22.79 |
Window Orientation South: | R = 1,0 |
The number of external walls is two: | K = 1,2 |
Insulation of external walls - standard: | U = 1,0 |
Minimum temperature - up to -35 ° C: | T = 1.3 |
Room height - up to 3 m: | H = 1.05 |
The room above is an uninsulated attic: | W = 1.0 |
Frames - single-chamber double-glazed window: | G = 1.0 |
The ratio of the area of the window and the room is up to 0.1: | X = 0.8 |
Radiator position - under the windowsill: | Y = 1.0 |
Radiator connection - diagonally: | Z = 1.0 |
Total (do not forget to multiply by 100): | Q = 2 986 watts |
The following is a description of the calculation of the number of radiator sections and the required number of batteries. It is based on the obtained results of thermal capacities, taking into account the dimensions of the proposed installation sites for heating devices.
Regardless of the outcome, it is recommended that in corner rooms not only window sills be equipped with radiators. Batteries should be installed at the “blind” external walls or near the corners that are most frozen through under the influence of street cold.
Specific heat output of battery sections
Even before performing the general calculation of the required heat transfer of heating devices, it is necessary to decide which collapsible batteries of which material will be installed in the premises.
The choice should be based on the characteristics of the heating system (internal pressure, coolant temperature). At the same time, do not forget about the very varied cost of purchased products.
About how to correctly calculate the right amount of different batteries for heating, and we will go further.
With a coolant at 70 ° C, standard 500 mm sections of radiators made of dissimilar materials have unequal specific heat output “q”.
- Cast Iron - q = 160 Watts (specific power of one pig-iron section). Radiators from this metal are suitable for any heating system.
- Steel - q = 85 Watts. Steel tubular radiators can operate in the most severe operating conditions. Their sections are beautiful in their metallic luster, but have the least heat dissipation.
- Aluminum - q = 200 Watts. Lightweight, aesthetic aluminum radiators should only be installed in autonomous heating systems in which the pressure is less than 7 atmospheres. But in terms of heat transfer to their sections there are no equal.
- Bimetal - q = 180 watts. The interior of the bimetallic radiators is made of steel, and the heat sink surface is made of aluminum. These batteries will withstand all kinds of pressure and temperature conditions. The specific heat output of the bimetal sections is also up to par.
The given q values are rather arbitrary and are used for preliminary calculation.More accurate numbers are contained in the passports of the purchased heating appliances.
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Advantages of the sectional assembly principle
Basic rules for assembling heating appliances
Outdated Cast Iron Battery Sections
Powder coated colored sections
Calculation of the number of sections of radiators
Collapsible radiators from any material are good in that in order to achieve their rated heat output, individual sections can be added or removed.
To determine the required number of “N” battery sections from the selected material, the following formulas are used:
N = Q / q,
Where:
- Q = previously calculated required heat output of devices for heating a room,
- q = thermal power specific section of the proposed battery installation.
Having calculated the total required number of sections of radiators in the room, you need to understand how many batteries you need to install. This calculation is based on a comparison of the dimensions of the proposed installation locations of the radiators and the dimensions of the batteries, taking into account the connection.
the battery elements are connected with nipples with a multidirectional external thread using a radiator key, while gaskets are installed in the joints
For preliminary calculations, you can arm with data on the width of the sections of different radiators:
- cast iron = 93 mm
- aluminum = 80 mm
- bimetallic = 82 mm.
In the manufacture of collapsible radiators from steel pipes, manufacturers do not adhere to certain standards. If you want to supply such batteries, you should approach the issue individually.
You can also use our free online calculator to calculate the number of sections:
Improving heat transfer efficiency
When the radiator heats the room’s internal air, the external wall is also intensely heated in the area behind the battery. This leads to additional unjustified heat loss.
It is proposed to improve the heat transfer efficiency of the radiator to block the heater from the outer wall with a heat-reflecting screen.
The market offers many modern insulating materials with a heat-reflecting foil surface. The foil protects the warm air warmed by the battery from contact with a cold wall and directs it into the room.
For proper operation, the boundaries of the installed reflector must exceed the dimensions of the radiator and protrude on each side by 2-3 cm. The gap between the heater and the thermal protection surface should be left at 3-5 cm.
For the manufacture of a heat-reflecting screen, isospan, penofol, aluf can be advised. From the acquired roll, a rectangle of the required size is cut out and fixed on the wall at the radiator installation site.
It is best to fix the screen reflecting the heat of the heater on the wall with silicone glue or with liquid nails
It is recommended to separate the insulation sheet from the external wall with a small air gap, for example, using a thin plastic grill.
If the reflector is joined from several parts of the insulating material, the joints on the side of the foil must be glued with metallized adhesive tape.
Small films will present the practical embodiment of some engineering tips in everyday life. In the next video, you can see a practical example of calculating heating radiators:
The following video tells how to mount the reflector under the battery:
The acquired skills in calculating the thermal power of different types of heating radiators will help the home foreman in the competent design of the heating system. And housewives will be able to verify the correctness of the battery installation process by third-party specialists.
Did you do your own calculating the power of heating batteries for your home? Or faced with problems arising from the installation of low-power heating devices? Tell your readers about your experience - please leave comments below.