To solve this problem correctly and determine how many sections of heating radiators (bimetallic, steel, cast iron, etc.) are needed, it is necessary to make a reliable calculation based on the area of the room with using the online calculator below.
Enter the radiator connection diagram in the online calculator
When constructing any building, calculating the capacity of heating radiators and sizing the heat exchanger is an important consideration. Homeowners face the same problem when replacing radiators.
In this article, we'll explore all the different types of convectors and calculate radiator performance based on area using a formula, no calculator required.
Specifics of heating calculations
A common design for heating buildings is a radiator with standard 50 cm spacing between sections. The heat output of a single section is affected by the material it is made of:
- cast iron - 120 W;
- steel - 90;
- aluminum - 180;
- bimetallic material - 190.
But these values are average, and in real life they are affected by operating conditions, the size of the room and the degree of heating of the water at the supply and outlet; as it decreases, heat transfer decreases.
Therefore, to calculate the heat output of a heating radiator under specific conditions, it is necessary to know the temperature difference in the main line - this is the value of the difference in temperature between the air in the room and the heating device.
The temperature in the device is the arithmetic mean of the supply and return temperatures. The temperature difference can be calculated using an online calculator or using the formula
DT = (T supply + T return) / 2 - T room, where:
DT — temperature difference
The device's data sheet specifies the calculated temperature difference, located next to the power rating. For example: 2000 W, 90/70 (supply and return). This means that when cooling water from 90 to 70 degrees, the convector's thermal output is 2000 W.
When installing such a device on a low- or medium-temperature system, the heat output will be lower than stated and should be recalculated. This can be done using an online calculator or the following formula:
Pf=Pn x (DTf / DTn) to the power of 1/3, where:
- Pf and Pn — actual and standard thermal power in W;
- DTf and Dtn are the actual and standard temperature differences.
In a heated room, the standard pressure indicator corresponds to 20 degrees.
The average heat consumption per square meter is 60–150 kilowatts, depending on climate conditions and the floor on which the heated room is located. If you don't enter this value in the "Estimated heat energy per square meter" field, the calculator will assume an average of 100 watts.
Types of heat exchangers
A heating radiator is a device consisting of sections combined into a single unit through which a heated coolant—usually water—flows. A section is a radiator element, typically a cast, two-tube structure capable of radiating heat, which is transferred to the surrounding air, creating a comfortable atmosphere in the apartment.
Heating units are designed as either panel or sectional units. There are also registers—a large-diameter tubular element—or a shaped coil (like a heated towel rail in a bathroom) that are installed into the system.
Heating appliances come in steel, cast iron, aluminum, and copper. The cast iron items we're accustomed to seeing in our homes require painting to maintain their appearance.
Please note! There are electric convectors—they consist of a housing with a heating element inside, equipped with a thermostat with a degree scale and LEDs.
Cast iron
Cast iron products are the most common; they have a simple shape and design. They can be wall-mounted or stand-alone.
Manufactured using casting, these are massive structures that retain heat for a long time and offer the most cost-effective operation.
Pros:
- transmit heat well;
- corrosion resistant;
- durable, last for at least 30 years;
- not picky about water quality.
Cons:
- heavy, difficult to install;
- bad design.
Steel
Steel heat exchangers are either panel or tubular.
Panel models are made of 1.5 mm thick metal, so they have a small thermal capacity. This quality allows for quick temperature adjustment. They are efficient, with efficiency reaching 75%. Their advantages include low cost and ease of use. A disadvantage is poor corrosion resistance.
Tubular varieties have all the advantages of the panel type, but unlike them, they have a higher pressure level of 9 - 16 bar, while the first ones have 7 - 9. And the heating power (120 - 1600 W) and water heating (120) are the same for both models.
The range of steel radiators is wide in size (length), allowing you to choose one for any area.
Aluminum
Aluminum heat exchangers are recommended for private buildings with independent heating systems. This model is not intended for use in centralized heating systems, as it is susceptible to damage from poor-quality heat transfer fluid. They are marketed in Russia by Rifara.
Aluminum batteries are available in cast and extruded forms:
- cast - have several compartments, they are durable, with thicker walls and wide channels for water;
- Extrusion - according to the production technology, the device is pressed out of an aluminum alloy mechanically, resulting in a single product, while the number of compartments cannot be increased.
All aluminum radiators offer high thermal output, are lightweight, and easy to install. They also have a visually appealing appearance. In terms of pressure and temperature ratings, they are comparable to steel products.
The weak points of such devices are the joints between the compartments and the pipe connections, which can lead to leaks after their lifespan. Furthermore, they are not impact-resistant. Their service life is only 3-5 years.
Bimetallic
The bimetallic heat exchanger has a tubular steel core and an aluminum housing. It is durable and reliable, capable of withstanding high pressure. Despite its low inertia, it offers increased heat transfer with low water consumption. It has a visually appealing appearance and is easy to maintain.
The main disadvantage is the high price.
Copper
Copper has long been used to make heat exchangers, but such models have only recently gained widespread use. Heating systems require a refined form of copper, and new technologies have made its production inexpensive.
While offering the same technical specifications as other models, they weigh less and produce higher heat output. This feature significantly reduces electricity costs.
Copper has increased mechanical strength, so the pipes can be used in combination with water heated to 150 degrees, at a pressure of 16 atmospheres.
Which radiator should I choose?
Before purchasing heating components, you need to know what the entire system consists of. A standard heating system includes:
- boiler - this can be an electric boiler, or one that runs on gas or solid fuel;
- battery;
- pipes;
- electric pump, if provided for in the project;
- expansion tank.
The calculation of batteries for heating any area and their selection are influenced by:
- Working pressure - its maximum;
- Power;
- Device design.
Additionally, you'll need to calculate the number of radiator sections per square meter, taking into account the number of rooms to be heated. This can be done using a formula or a calculator.
Methods for calculating radiator sections based on room area without a calculator
Thermal calculations based on room volume are considered the most complex in the construction industry. To calculate the number of radiator sections—whether bimetallic, aluminum, or cast iron—you can use an online calculator or use the formula:
- By area of the room;
- By heat loss.
The first method for calculating the number of sections of a heating device, without using a calculator, using a formula, looks like this:
k = P1/P2, where:
- P1 — required power level in W;
- P2 is the heat output of one compartment in W.
To calculate the total power rating for heating an entire apartment, you need to multiply the standard per cubic meter by the building's area. However, there are no such standards in regulatory documents, so approximate values are used for calculations. For a brick house, the standard is 0.037 kW per cubic meter; for a panel house, the standard is 0.041 kW/m3; for wooden houses, a lower value is used.
In addition, depending on the method of connecting the device, the following adjustments are applied:
- For one-sided:
- heating and return from below - 1.28;
- serve from above and return from below - 1.03.
- For double sided:
- heating and return from below on both sides - 1.13;
- feed and return from below on one side - 1.28.
- For diagonal:
- heating and return from below - 1.00;
- serve from above and return from below - 1.25.
The second method of calculation without the help of a calculator is using a formula taking into account heat loss.
k = Q / P2, where:
- Q — heat loss in W;
- P2 is the heat output of one compartment in W.
The power of one section is shown in the table:
| View | Heat transfer of the compartment depending on the axial gap |
| Steel | 85 - 120 |
| Cast iron | 100 - 160 |
| Aluminum | 140 - 185 |
| Biometric | 150 - 210 |
You can calculate the number of battery compartments for heating a private house in the following way.
N = S/t*100*w*h*r, where:
- N — number of compartments;
- S — building size;
- t is the thermal energy needed to heat the room;
- w is an index that takes into account the area and model of windows: standard type - 1.1, or plastic with double glazing - 1;
- h — ceiling height: up to 2.7 m — 1, from 2.7 to 3.5 m — 1.5;
- r is a correction value, it depends on the number of external walls: corner room – 1, other type – 1.
Depending on the area, the calculation of the heating radiator's performance per square meter is determined according to the formula:
t = S*100 W, where
- 100 W is the heat required to heat 1 m2 of a room.
The efficiency of a heating system is influenced by many factors. It is essential to accurately calculate the heating power and heat output of the heating system used to heat a given area of the room.
If you are not sure that you can perform calculations correctly using the formula, it is better to use a calculator or seek help from professionals.
