What diameter of polypropylene pipes is needed for heating. Pipe diameters for heating a private house

With two-pipe wiring, the most important thing is not to make a mistake in choosing the pipe diameter. Otherwise, heating will not be uniform, or even absent altogether on some heating devices. This material based solely on my own work experience. If you stick to it, everything will work.

First let's define the basic terms:

supply pipe - a pipe of any diameter through which heated coolant flows to the radiators, warm floor, convectors, etc., (See also: Two-pipe heating system for a private house)
return pipe - a pipe of any diameter through which the coolant returns to the boiler; in a regular two-pipe system, the diameters of the supply and return pipes are equal at the same points.
shoulder - a pipe outlet through a tee in an additional direction; shoulders can also be at an existing shoulder. There are always two of them, according to the number of branches at the tee. For most domestic boilers, the diameter of the supply and return pipes is equal to 1 inch (d25) or an inch and a quarter (d32). There are boilers whose outlet diameter is three quarters (d20). With such boilers it is better to build a single-pipe circuit. Let's look at the range of diameters. It looks like this: d32, d25, d20, d16. The main rule for forming the pipe diameter: after each tee, the diameter decreases by one position when passing from the boiler to the last radiator. For example: you have a d32 pipe coming from your boiler. You have d16 for the first radiator. Next comes d25. D16 goes to the second radiator. Next comes d20. D16 goes to the third radiator. And the last one goes to d16. We see that there are 4 radiators “hanging” on the pipe. (See also: Modern water heating)What to do if there are more radiators? Very simple. We separate the pipe into two arms. D32 comes out of the boiler. Through the tee we open two pipes, but already d25. From each d25 we allocate d16 to the radiators, followed by d20. From each d20 we assign d16 to two more radiators, then d16 goes to two more radiators. As you can see, we already have six radiators. I can also say with complete certainty that if you make a tap d16 from d16 onto two radiators and throw further d16 onto two more radiators, then such a system will work. Therefore, we already fit eight radiators.
The considered system will operate without balancing. If there are any deviations from this principle, then you will need to balance the radiators, that is, use valves to limit the flow to the hottest ones so that the heat reaches the less heated ones. The more radiators you have, the less efficient the system is. Eight is the best option.

Selection of pipe diameters in a two-pipe heating system

When laying out a two-pipe heating system, it is very important to choose correct diameter pipes Otherwise, heating will not be uniform, or even absent altogether on some heating devices.

How to choose the diameter of heating pipes

In the article we will consider systems with forced circulation. In them, the movement of the coolant is ensured by a constantly running circulation pump. When choosing the diameter of heating pipes, it is assumed that their main task is to ensure the delivery of the required amount of heat to heating devices - radiators or registers. For the calculation you will need the following data:

General heat loss of a house or apartment.
Power heating devices(radiators) in every room.
Pipeline length.
Method of wiring the system (one-pipe, two-pipe, with forced or natural circulation).

That is, before you start calculating the diameters of the pipes, you first calculate the total heat loss, determine the power of the boiler and calculate the power of the radiators for each room. You will also need to decide on the wiring method. Using these data, you draw up a diagram and then just start calculating.

To determine the diameter of the heating pipes, you will need a diagram with the thermal load values assigned to each element.

What else do you need to pay attention to? What is marked for polypropylene and copper pipes outside diameter, and the internal one is calculated (subtract the wall thickness). For steel and metal-plastic ones, the internal size is indicated when marking. So don't forget this little thing.

How to choose the diameter of a heating pipe

Let me explain. It is important for us to deliver the right amount of heat to the radiators and at the same time achieve uniform heating of the radiators. In systems with forced circulation, we do this using pipes, coolant and a pump. In principle, all we need is to “drive” a certain amount of coolant over a certain period of time. There are two options: install pipes of a smaller diameter and supply coolant at a higher speed, or make a system of a larger cross-section, but with less traffic. Usually the first option is chosen. And that's why:

the cost of products with a smaller diameter is lower;
they are easier to work with;
when laid open, they do not attract so much attention, and when laid in the floor or walls, smaller grooves are required;
when not large diameter There is less coolant in the system, which reduces its inertia and leads to fuel savings.

Calculation of the diameter of copper heating pipes depending on the power of the radiators

Since there is a certain set of diameters and a certain amount of heat that needs to be delivered through them, it is unreasonable to calculate the same thing every time. Therefore, special tables have been developed, according to which, depending on the required amount of heat, the speed of movement of the coolant and the temperature indicators of the system, the possible size is determined. That is, to determine the cross-section of pipes in the heating system, find the required table and select the appropriate cross-section from it.

The diameter of the heating pipes was calculated using the following formula (you can calculate it if you wish). Then the calculated values were recorded in a table.

Formula for calculating the diameter of a heating pipe

D - required pipeline diameter, mm

∆t° - temperature delta (difference between supply and return), °C

Q - load on a given section of the system, kW - the amount of heat determined by us required to heat the room

V - coolant speed, m/s - selected from a certain range.

In systems individual heating the coolant movement speed can be from 0.2 m/s to 1.5 m/s. Based on operating experience, it is known that the optimal speed is in the range of 0.3 m/s - 0.7 m/s. If the coolant moves more slowly, air jams occur; if it moves faster, the noise level increases greatly. The optimal speed range is selected in the table. Tables are designed for different types pipes: metal, polypropylene, metal-plastic, copper. The values are calculated for standard operating modes: high and medium temperatures. To make the selection process more clear, let’s look at specific examples.

Calculation for a two-pipe system

There is a two-story house with a two-pipe heating system, two wings on each floor. Polypropylene products will be used, operating mode 80/60 with a temperature delta of 20 °C. The heat loss of the house is 38 kW of thermal energy. The first floor has 20 kW, the second 18 kW. The diagram is shown below.

Two-pipe heating circuit two-story house. Right wing (click to enlarge)

Two-pipe heating scheme for a two-story house. Left wing (click to enlarge)

On the right is a table from which we will determine the diameter. The pinkish area is the zone of optimal coolant speed.

Diameter calculation table polypropylene pipes heating. Operating mode 80/60 with a temperature delta of 20°C (click to enlarge)

We determine which pipe needs to be used in the area from the boiler to the first branch. The entire coolant passes through this section, therefore the entire heat volume of 38 kW passes through. In the table we find the corresponding line, using it we get to the tinted pink zones and go up. We see that two diameters are suitable: 40 mm, 50 mm. For obvious reasons, we choose the smaller one - 40 mm.
Let's look at the diagram again. Where the flow is divided, 20 kW goes to the 1st floor, 18 kW goes to the 2nd floor. In the table we find the corresponding lines and determine the cross-section of the pipes. It turns out that we are dividing both branches with a diameter of 32 mm.
Each of the circuits is divided into two branches with equal load. On the first floor there is 10 kW each to the right and left (20 kW/2=10 kW), on the second floor 9 kW each (18 kW/2)=9 kW). Using the table, we find the corresponding values for these areas: 25 mm. This size is continued to be used until the heat load drops to 5 kW (as seen in the table). Next comes a section of 20 mm. On the first floor we go 20 mm after the second radiator (look at the load), on the second - after the third. At this point there is one amendment made by accumulated experience - it is better to switch to 20 mm at a load of 3 kW.

All. The diameters of polypropylene pipes for a two-pipe system are calculated. For the return, the cross-section is not calculated, and the wiring is made with the same pipes as the supply. We hope the methodology is clear. It will not be difficult to carry out a similar calculation if all the initial data is available. If you decide to use other pipes, you will need other tables calculated for the material you need. You can practice on this system, but for an average temperature mode of 75/60 and a delta of 15 °C (the table is located below).

Table for calculating the diameter of polypropylene heating pipes. Operating mode 75/60 and delta 15 °C (click to enlarge)

Determination of pipe diameter for a single-pipe system with forced circulation

The principle remains the same, the methodology changes. Let's use another table to determine the diameter of pipes with a different principle for entering data. In it, the optimal zone of coolant movement speeds is colored blue, the power values are not in the side column, but are entered in the field. That's why the process itself is a little different.

Table for calculating the diameter of heating pipes

Using this table we calculate interior pipe diameter for a simple one-pipe heating circuit for one floor and six radiators connected in series. Let's start the calculation:

15 kW is supplied to the system input from the boiler. We find values close to 15 kW in the optimal speed zone (blue). There are two of them: in a line measuring 25 mm and 20 mm. For obvious reasons, we choose 20 mm.
On the first radiator, the thermal load is reduced to 12 kW. We find this value in the table. It turns out that it goes further from it of the same size - 20 mm.
On the third radiator the load is already 10.5 kW. We determine the cross section - still the same 20 mm.
Judging by the table, the fourth radiator is already 15 mm: 10.5 kW-2 kW = 8.5 kW.
On the fifth there is another 15mm, and after that you can already put 12mm.

Scheme of a one-pipe system with six radiators

Please note again that the table above defines internal diameters. Using them you can then find the markings of pipes made of the desired material.

It seems that there should be no problems with how to calculate the diameter of the heating pipe. Everything is quite clear. But this is true for polypropylene and metal-plastic products - their thermal conductivity is low and losses through the walls are insignificant, therefore they are not taken into account when calculating. Another thing is metals - steel, stainless steel and aluminum. If the length of the pipeline is significant, then the losses through their surface will be significant.

Features of calculating the cross-section of metal pipes

For large heating systems with metal pipes, heat loss through the walls must be taken into account. The losses are not so great, but over a long distance they can lead to the fact that the temperature on the last radiators will be very low due to wrong choice diameter

Let's calculate the losses for a 40 mm steel pipe with a wall thickness of 1.4 mm. Losses are calculated using the formula:

q - heat loss per meter of pipe,

k is the linear heat transfer coefficient (for this pipe it is 0.272 W*m/s);

tw - water temperature in the pipe - 80°C;

tп - room temperature - 22°C.

Substituting the values we get:

It turns out that almost 50 W of heat is lost per meter. If the length is significant, this can become critical. It is clear that the larger the cross-section, the greater the losses will be. If you need to take these losses into account, then when calculating losses, add losses in the pipeline to reduce the thermal load on the radiator, and then, using the total value, find the required diameter.

Determining the diameter of heating system pipes is not an easy task

But for individual heating systems these values are usually not critical. Moreover, when calculating heat loss and equipment power, the calculated values are most often rounded upward. This gives a certain margin, which allows you not to make such complex calculations.

An important question: where to get tables? Almost all manufacturers' websites have such tables. You can read it directly from the site, or you can download it for yourself. But what to do if you still haven’t found the necessary tables for the calculation. You can use the diameter selection system described below, or you can do it differently.

Despite the fact that when marking different pipes different values are indicated (internal or external), with a certain error they can be equated. Using the table below you can find the type and marking for a known internal diameter. You can immediately find a corresponding pipe size made of a different material. For example, you need to calculate the diameter of metal-plastic heating pipes. You did not find a table for MP. But there is one for polypropylene. Select sizes for PPR, and then use this table to find analogues in MP. Naturally, there will be an error, but for systems with forced circulation it is acceptable.

table of correspondence different types pipes (click to enlarge)

Using this table, you can easily determine the internal diameters of the heating system pipes and their markings.

Selection of pipe diameter for heating

This method is not based on calculations, but on a pattern that can be traced in the analysis quite large quantity heating systems. This rule was developed by installers and is used by them on small systems for private houses and apartments.

The diameter of the pipes can be simply selected by following a certain rule(click to enlarge)

Most heating boilers have two sizes of supply and return pipes: ¾ and ½ inches. It is with this pipe that the pipe is routed until the first branch, and then at each branch the size is reduced by one step. In this way you can determine the diameter of the heating pipes in the apartment. The systems are usually small - from three to eight radiators in the system, maximum - two or three branches with one or two radiators on each. For such a system, the proposed method is an excellent choice. The situation is practically the same for small private houses. But if there are already two floors and a more extensive system, then you have to count and work with tables.

If the system is not very complex and branched, the diameter of the heating system pipes can be calculated independently. To do this, you need to have data on the heat loss of the room and the power of each radiator. Then, using the table, you can determine the cross-section of the pipe that will cope with supplying the required amount of heat. It is better to entrust the cutting of complex multi-element circuits to a professional. As a last resort, calculate it yourself, but try to at least get advice.

Heating system pipe diameter: calculation, formula, selection

What diameter of heating pipe should I choose? How to calculate or select it? Methods and tables for determining pipe diameters. Example of calculating diameters for

All about two-pipe heating systems

A two-pipe heating system is more complex than a single-pipe one, and the amount of materials required for installation is significantly greater. Nevertheless, it is the 2-pipe heating system that is more popular. From the name it follows that it uses two circuits. One serves to deliver hot coolant to the radiators, and the second takes the cooled coolant back. Such a device is applicable to any type of structure, as long as its layout allows for the installation of this structure.

Advantages and disadvantages

The demand for a double-circuit heating system is explained by the presence a number of significant advantages . First of all, it is preferable to a single-circuit one, since in the latter the coolant loses a noticeable part of the heat even on the way to the radiators. In addition, the double-circuit design is more versatile and suitable for houses of different floors.

Disadvantage of a two-pipe system its higher cost is considered. However, many people mistakenly believe that since the presence of 2 circuits also implies the use of twice the number of pipes, then the cost of such a system is twice as much as a single-pipe system. The fact is that for a single-pipe design it is necessary to take pipes of large diameter. This ensures normal coolant circulation in the pipeline, and therefore the efficient operation of such a design. The advantage of a two-pipe system is that for its installation, pipes of smaller diameter are used, which are significantly cheaper. Accordingly additional elements for installation (pipes, valves, etc.) are also used with a smaller diameter, which also somewhat reduces the cost of the system.

Thus, the installation budget for a two-pipe system will not be much larger than for a single-pipe system. On the other hand, the efficiency of the first will be noticeably higher, which will be a good compensation for the increased costs.

Application example

One of the places where two-pipe heating would be very practical is garage. This workroom, so it is not required here Full time job heating. In addition, a two-pipe heating system with your own hands is a very real idea. Heating in the garage is not necessary, but it will absolutely not be superfluous, since in winter time It’s very difficult to work here: it’s not easy to start the engine, the oil freezes, and just working with your hands is very uncomfortable. The two-pipe heating system provides quite acceptable conditions for working indoors.

Types of two-pipe heating systems

There are several criteria by which such heating structures can be classified.

Open and closed

Closed systems assume the use of an expansion tank with a membrane. They can work with high blood pressure. Instead of regular water closed systems coolants based on ethylene glycol, which do not freeze at low temperatures (up to 40 °C below zero). Motorists know such liquids called "antifreeze".

1. Heating boiler; 2. Security group; 3. Relief valve overpressure; 4. Radiator; 5. Return pipe; 6. Expansion tank; 7. Valve; 8. Drain valve; 9. Circulation pump; 10. Pressure gauge; 11. Make-up valve.

However, we must remember that for heating devices there are special compositions of coolants, as well as special additives and additives. The use of common substances can damage expensive heating boilers. Such cases may be regarded as non-warranty, and therefore repairs will require significant costs.

Open system characterized by the fact that the expansion tank must be installed strictly at the highest point of the device. It must be equipped with an air pipe and a drain pipe through which excess water is drained from the system. You can also take it through warm water for household needs. However, such use of the tank requires automatic replenishment of the structure and eliminates the possibility of using additives and additives.

1. Heating boiler; 2. Circulation pump; 3. Heating devices; 4. Differential valve; 5. Gate valves; 6. Expansion tank.

And yet the two-pipe heating system closed type is considered safer, which is why modern boilers are most often designed for it.

Horizontal and vertical

These types differ in the location of the main pipeline. It serves to connect all elements of the system. Both horizontal and vertical systems have their own advantages and disadvantages. However, both designs demonstrate good heat transfer and hydraulic stability.

Two-pipe horizontal heating design found in one-story buildings. Vertical It is also used in high-rise buildings. It is more complex and, accordingly, more expensive. Here vertical risers are used, to which heating elements are connected on each floor. Advantage vertical systems is that, as a rule, air jams do not occur in them, since the air flows through the pipes up to the expansion tank.

Systems with forced and natural circulation

These types differ in that, firstly, there is an electric pump that forces the coolant to move, and secondly, circulation occurs on its own, obeying physical laws. The disadvantage of pump designs is that they depend on the availability of electricity. For small rooms there is special meaning in coercive systems no, except that the house will heat up faster. For large areas, such designs will be justified.

To choose the right type of circulation, it is necessary to consider which type of pipe layout used: upper or lower.

Top wiring system involves laying a main pipeline under the ceiling of the building. This provides high pressure coolant, due to which it passes well through the radiators, which means that the use of a pump will be unnecessary. Such devices look more aesthetically pleasing; the pipes at the top can be hidden decorative elements. However, in a system with overhead wiring you need to install membrane tank, which entails additional costs. It is possible to install an open tank, but it must be at the highest point of the system, that is, in the attic. In this case, the tank must be insulated.

Bottom wiring involves installing the pipeline just below the window sill. In this case, you can install an open expansion tank anywhere in the room slightly above the pipe and radiators. But such a design cannot be done without a pump. In addition, difficulties arise if the pipe must pass past the doorway. Then you need to run it around the perimeter of the door or make 2 separate wings in the contour of the structure.

Dead-end and passing

In a dead-end system hot and cooled coolant go to different directions. In a passing system, designed according to the Tichelman scheme (loop), both flows go in the same direction. The difference between these types is the ease of balancing. If passing system when using radiators with an equal number of sections, the section itself is already balanced, then in a dead-end one you need to install on each radiator thermostatic valve or needle valve.

If the Tichelman scheme uses radiators with an unequal number of sections, the installation of valves or taps is also required here. But even in this case, this design is easier to balance. This is especially noticeable in extended heating systems.

Selection of pipes by diameter

The choice of pipe cross-section must be made based on the volume of coolant that must pass per unit of time. It, in turn, depends on the thermal power required to heat the room.

In our calculations, we will assume that the amount of heat loss is known and there is a numerical value of the heat required for heating.

Calculations begin with the final, that is, the farthest radiator of the system. To calculate the coolant flow for a room, you will need the formula:

G – water consumption for heating the room (kg/h);
Q − thermal power, required for heating (kW);
c – heat capacity of water (4.187 kJ/kg×°C);
Δt is the temperature difference between the hot and cooled coolant, taken equal to 20 °C.

For example, it is known that the thermal power for heating a room is 3 kW. Then the water consumption will be:

3600×3/(4.187×20)=129 kg/h, that is, about 0.127 cubic meters. m of water per hour.

In order for water heating to be balanced as accurately as possible, it is necessary to determine the cross-section of the pipes. To do this we use the formula:

S is the cross-sectional area of the pipe (m2);
GV – volumetric water flow (m3/h);
v is the speed of water movement, is in the range of 0.3−0.7 m/s.

If the system uses natural circulation, then the movement speed will be minimal - 0.3 m/s. But in the example under consideration, let’s take the average value - 0.5 m/s. Using the indicated formula, we calculate the cross-sectional area, and based on it, the internal diameter of the pipe. It will be 0.1 m. We select a polypropylene pipe of the nearest larger diameter. This is a pipe with an internal diameter of 15 mm. We will use it in our design.

Then we move on to the next room, calculate the coolant flow for it, sum it up with the flow rate for the calculated room and determine the diameter of the pipe. And so on all the way to the boiler.

System installation

When installing the structure, certain rules should be followed:

any two-pipe design includes 2 circuits: the upper one serves to supply hot coolant to the radiators, the lower one serves to remove cooled coolant;
the pipeline should have a slight slope towards the final radiator;
the pipes of both circuits must be parallel;
the central riser must be insulated to prevent heat losses when supplying coolant;
in reversible two-pipe systems, it is necessary to provide several taps with which it is possible to drain water from the device. This may be needed during repair work;
when designing a pipeline, it is necessary to provide for the smallest possible number of angles;
the expansion tank must be installed at the highest point of the system;
the diameters of pipes, taps, pipes, connections must match;
When installing a pipeline made of heavy steel pipes, special fasteners must be installed to support them. The maximum distance between them is 1.2 m.

How to make the correct connection of heating radiators, which will ensure the most comfortable conditions in the apartment? When installing two-pipe heating systems, you must adhere to the following sequence:

The central riser of the heating system is diverted from the heating boiler.
At the highest point, the central riser ends with an expansion tank.
Pipes run from the tank throughout the building, supplying hot coolant to the radiators.
To remove cooled coolant from heating radiators with a two-pipe design, a pipeline is laid parallel to the supply one. It must be connected to the bottom of the heating boiler.
For systems with forced circulation of coolant, an electric pump must be provided. It can be installed at any convenient point. Most often, the pump is mounted near the boiler, near the entry or exit point.

Connecting a heating radiator is not such a difficult process if you approach this issue scrupulously.

Two-pipe heating systems: do-it-yourself diagrams and installation

The use of two-pipe heating systems, pros and cons, varieties. Help in selecting pipe diameters, installing the system yourself.

Installation of a two-pipe heating system

According to statistics, over 70% of all residential buildings are heated using water heating. One of its varieties is a two-pipe heating system - this publication is dedicated to it.

Radiator on a two-pipe circuit

The article discusses the advantages and disadvantages, diagrams, drawings and recommendations for installing two-pipe wiring with your own hands.

Differences between a two-pipe heating system and a single-pipe one

Any heating system is closed loop, through which the coolant circulates. However, unlike a one-pipe network, where water is supplied to all radiators in turn through the same pipe, a two-pipe system involves dividing the wiring into two lines - supply and return.

A two-pipe heating system for a private house, in comparison with a single-pipe configuration, has the following advantages:

Minimal coolant losses. In a single-pipe system, radiators are alternately connected to the supply line, as a result of which the coolant passing through the battery loses temperature and enters the next radiator partially cooled. With two-pipe configuration, each battery is connected to the supply pipe with a separate outlet. You get the opportunity to install a thermostat on each radiator, which will allow you to regulate the temperature in different rooms houses independently of each other.
Low hydraulic losses. When installing a system with forced circulation (necessary in buildings large area) a two-pipe system requires the installation of a less efficient circulation pump, which allows for significant savings.
Versatility. A two-pipe heating system can be used in multi-apartment, one or two-story buildings.
Maintainability. Shut-off valves can be installed on each branch of the supply pipeline, which makes it possible to cut off the coolant supply and repair damaged pipes or radiators without stopping the entire system.

Two-pipe heating system

Among the disadvantages of this configuration, we note a twofold increase in the length of the pipes used, but this does not threaten a dramatic increase financial costs, since the diameter of the pipes and fittings used is smaller than when installing a single-pipe system.

Classification of two-pipe heating

The two-pipe heating system of a private house, depending on its spatial location, is classified into vertical and horizontal. The more common is the horizontal configuration, which involves connecting radiators on a building floor to a single riser, while in vertical systems radiators from different floors are connected to the riser.

The use of vertical systems is justified in a two-story building. Despite the fact that the arrangement of such a configuration is more expensive due to the need to use more pipes, with vertically located risers, the possibility of formation of air jams inside radiators, which increases the reliability of the system as a whole.

Also, a two-pipe heating system is classified according to the direction of movement of the coolant, according to which it can be direct-flow or dead-end. In dead-end systems, liquid circulates through the return and supply pipes in different directions; in direct-flow systems, their movement coincides.

Depending on the method of transporting the coolant, systems are divided into:

with natural circulation;
with forced circulation.

Heating with natural circulation can be used in one-story buildings with up to 150 square meters. It does not provide for the installation of additional pumps - the coolant moves due to its own density. Characteristic feature systems with natural circulation is laying pipes at an angle to the horizontal plane. Their advantage is independence from the availability of power supply, the disadvantage is the inability to adjust the water supply speed.

In a two-story building, a two-pipe heating system is always performed with forced circulation. In terms of efficiency, this configuration is more effective, since you get the opportunity to regulate the flow and speed of the coolant using a circulation pump, which is installed on the supply pipe leaving the boiler. In heating with forced circulation, pipes of relatively small diameters (up to 20 mm) are used, which are laid without a slope.

Which heating network layout to choose?

Depending on the location of the supply pipeline, two-pipe heating is classified into two types - with upper and lower wiring.

The diagram of a two-pipe heating system with top wiring involves installing an expansion tank and a distribution line at the highest point of the heating circuit, above the radiators. This installation cannot be done in one-story building with a flat roof, since to accommodate communications you will need an insulated attic or a specially designated room on the second floor of a two-story house.

Bottom wiring system

A two-pipe heating system with bottom wiring differs from the top one in that the distribution pipeline in it is located in the basement or in an underground niche, under the radiators. The outermost heating circuit is the return pipe, which is installed 20-30 cm lower than the supply line.

This is a more complex configuration, requiring the connection of an upper air pipe, through which excess air will be removed from the radiators. With absence basement additional problems may arise due to the need to install the boiler below the level of the radiators.

Top wiring system

Both the lower and upper circuits of a two-pipe heating system can be made in a horizontal or vertical configuration. However, vertical networks, as a rule, are made with bottom wiring. With this installation there is no need to install powerful pump for forced circulation, since due to the difference between the temperatures in the return and supply pipes, a strong pressure drop is created, increasing the speed of movement of the coolant. If, due to the specific layout of the building, such installation cannot be done, a main line with overhead routing is installed.

Selecting pipe diameters and rules for installing a two-pipe network

When installing two-pipe heating, it is extremely important to choose the correct pipe diameter, otherwise you may get uneven heating of radiators located far from the boiler. Most boilers for domestic use have a diameter of the supply and return pipes of 25 or 32 mm, which is suitable for a two-pipe configuration. If you have a boiler with 20 mm pipes, it is better to opt for a single-pipe heating system.

Size chart available on the market polymer pipes consists of diameters 16, 20, 25 and 32 mm. When installing the system yourself, you need to take into account the key rule: the first section of the distribution pipe must match the diameter of the boiler pipes, and each subsequent pipe section after the branch tee to the radiator is one size smaller.

Diagram of pipe diameters in a double-circuit system

In practice, it looks like this: a diameter of 32 mm comes out of the boiler, a radiator is connected to it through a tee with a 16 mm pipe, then after the tee the diameter of the supply line is reduced to 25 mm, at the next branch to the radiator line 16 mm after the tee the diameter is reduced to 20 mm and so on. If the number of radiators is greater than the standard sizes of pipes, it is necessary to divide the supply line into two arms.

When installing the system yourself, adhere to the following recommendations:

the supply and return lines must be parallel to each other;
each outlet to the radiator must be equipped with a shut-off valve;
the distribution tank, if installed in the attic when installing a network with overhead wiring, must be insulated;
pipe fastenings on the walls should be placed in increments of no more than 60 cm.

When setting up a system with forced circulation, it is important to correctly select the power of the circulation pump. The specific choice is made based on the size of the building:

for houses with an area of up to 250 m2, a pump with a capacity of 3.5 m3 / hour and a pressure of 0.4 MPa is sufficient;
250-350 m 2 - power from 4.5 m3/hour, pressure 0.6 MPa;
over 350 m 2 - power from 11 m 3 / hour, pressure from 0.8 MPa.

Despite the fact that it is more difficult to install two-pipe heating with your own hands than a one-pipe network, such a system, due to its high reliability and efficiency, fully justifies itself during operation.

Scheme of a two-pipe house heating system

Two-pipe heating system - diagrams, varieties. Installation technology for a two-pipe heating system.

The heating system in a private house can be forced or natural circulation. Depending on the type of system, the methods for calculating the pipe diameter and selecting other heating parameters are different.

Calculating the diameter of heating pipes is relevant in the process of individual or private construction. To correctly determine the dimensions of the system, you should know: what the lines are made of (polymer, cast iron, copper, steel), the characteristics of the coolant, its method of movement through the pipes. The introduction of a pressure pump into the heating design greatly improves the quality of heat transfer and saves fuel. The natural circulation of the coolant in the system is classic method, used in most private houses with steam (boiler) heating. In both cases, during reconstruction or new construction, it is important to choose the correct pipe diameter in order to avoid unpleasant moments in subsequent operation.

Pipe diameter – the most important indicator, which limits the overall heat transfer of the system, determines the complexity and length of the pipeline, and the number of radiators. Knowing the numerical value of this parameter, you can easily calculate possible energy losses.

Dependence of heating efficiency on pipeline diameter

Full time job energy system depends on the criteria:

Properties of movable fluid (coolant).
Pipe material.
Flow rate.
Flow section or diameter of pipes.
The presence of a pump in the circuit.

It is an incorrect statement that the larger the cross-section of the pipe, the more liquid it will let through. In this case, increasing the clearance of the line will contribute to a decrease in pressure, and as a result, the flow rate of the coolant. This can lead to a complete stop of fluid circulation in the system and zero efficiency. If a pump is included in the circuit, with a large pipe diameter and increased length of lines, its power may not be enough to provide the required pressure. If there is a power outage, using a pump in the system is simply useless - heating will be completely absent, no matter how much you heat the boiler.

For individual buildings with centralized heating, the diameter of the pipes is chosen the same as for city apartments. In houses with steam heating The boiler is required to carefully calculate the diameter. The length of the mains, the age and material of the pipes, the number of plumbing fixtures and radiators included in the water supply scheme, and the heating scheme (one-, two-pipe) are taken into account. Table 1 shows approximate coolant losses depending on the material and service life of the pipelines.

Table 1. Coolant losses

Pipe	Consumption m3/hour	Speed m/s	Pressure loss m/100m
New steel 133x5	60	1,4	3,6
New steel 133x5	60	1,4	6,84
PE 100 110x6.6 (SDR 17)	60	2,26	4,1
PE 80 110x8.1 (SDR 13.6)	60	2,41	4,8
New steel 245x6	400	2,6	4,3
Old steel 245x6	400	2,6	7,0
PE 100 225x13.4 (SDR 17)	400	3,6	4,0
PE 80 110x16.6 (SDR 13.6)	400	3,85	4,8
New steel 630x10	3000	2,85	1,33
Old steel 630x10	3000	2,85	1,98
PE 100 560x33.2 (SDR 17)	3000	4,35	1,96
PE 80 560x41.2 (SDR 13.6)	3000	4,65	2,3
New steel 820x12	4000	2,23	0,6
Old steel 820x10	4000	2,23	0,87
PE 100 800x47.4 (SDR 17)	4000	2,85	0,59
PE 80 800ъ58.8 (SDR 13.6)	4000	3,0	0,69

A pipe diameter that is too small will inevitably lead to the formation of high pressure, which will cause increased load on the connecting elements of the main line. In addition, the heating system will be noisy.

Heating system wiring diagram

To correctly calculate the resistance of the pipeline, and, consequently, its diameter, the wiring diagram of the heating system should be taken into account. Options:

two-pipe vertical;
two-pipe horizontal;
single-pipe.

A two-pipe system with a vertical riser can be with upper and lower placement of lines. A single-pipe system, due to the economical use of the length of the lines, is suitable for heating with natural circulation; a two-pipe system, due to a double set of pipes, will require inclusion in the pump circuit.

Horizontal wiring provides 3 types:

dead end;
with associated (parallel) movement of water;
collector (or beam).

In a single-pipe wiring diagram, you can provide a bypass pipe, which will serve as a backup line for liquid circulation when several or all radiators are turned off. Shut-off valves are installed on each radiator, allowing you to shut off the water supply when necessary.

Knowing the diagram of the heating system, you can easily calculate the total length, possible delays coolant flow in the main (at bends, turns, in connections), and as a result - obtain a numerical value of the system resistance. Based on the calculated loss value, you can select the diameter of the heating lines using the method discussed below.

Selecting pipes for a forced circulation system

The forced circulation heating system differs from the natural one by the presence of a pressure pump, which is mounted on the outlet pipe near the boiler. The device operates from a 220 V power supply. It turns on automatically (via a sensor) when the pressure in the system increases (that is, when the liquid heats up). The pump quickly circulates hot water through the system, which stores energy and actively transfers it through radiators to every room of the house.

Heating with forced circulation - pros and cons

The main advantage of heating with forced circulation is the efficient heat transfer of the system, which is carried out at a low cost of time and money. This method does not require the use of large diameter pipes.

On the other hand, for a pump in a heating system it is important to ensure uninterruptible power supply. Otherwise, the heating simply will not work in a large area of the house.

How to determine the diameter of a heating pipe with forced circulation using the table

The calculation begins with the definition total area a room that needs to be heated in winter, that is, this is the entire residential part of the house. The heat transfer standard for the heating system is 1 kW for every 10 sq. m. (with insulated walls and ceiling heights up to 3 m). That is, for a room of 35 sq.m. the norm will be 3.5 kW. To ensure a reserve of thermal energy, we add 20%, which gives a total of 4.2 kW. From Table 2 we determine close value to 4200 - these are pipes with a diameter of 10 mm (heat index 4471 W), 8 mm (heat index 4496 W), 12 mm (4598 W). These numbers are characterized by the following values of the coolant flow rate (in this case, water): 0.7; 0.5; 1.1 m/s. Practical indicators normal operation heating systems - speed hot water from 0.4 to 0.7 m/s. Taking this condition into account, we leave the choice of pipes with a diameter of 10 and 12 mm. Considering the water consumption, it would be more economical to use a pipe with a diameter of 10 mm. This is the product that will be included in the project.

It is important to distinguish between the diameters by which the choice is made: external, internal, nominal bore. As a rule, steel pipes are selected according to the internal diameter, polypropylene pipes - according to the external one. A beginner may encounter the problem of determining the diameter marked in inches - this nuance is relevant for steel products. Conversion from inch to metric dimensions is also carried out through tables.

Calculation of the diameter of a heating pipe with a pump

When calculating heating pipes the most important characteristics are:

The amount (volume) of water loaded into the heating system.
Total length of highways.
Flow speed in the system (ideal 0.4-0.7 m/s).
Heat transfer of the system in kW.
Pump power.
Pressure in the system when the pump is turned off (natural rotation).
System resistance.

H = λ(L/D)(V2/2g),

where H is the height that determines the zero pressure (lack of pressure) of the water column under other conditions, m;

λ – pipe resistance coefficient;

L – length (extent) of the system;

D – internal diameter (the desired value in this case), m;

V – flow velocity, m/s;

g – constant, free acceleration. fall, g=9.81 m/s2.

The calculation is carried out for minimal losses of thermal power, that is, several values of pipe diameter are checked for minimum resistance. The complexity arises with the coefficient of hydraulic resistance - to determine it, tables or a long calculation using the formulas of Blasius and Altschul, Konakov and Nikuradze are required. The final value of losses can be considered a number less than approximately 20% of the pressure created by the injection pump.

When calculating the diameter of heating pipes, L is taken to be equal to the length of the line from the boiler to the radiators and in reverse side excluding duplicate sections located in parallel.

The whole calculation ultimately comes down to comparing the resistance value obtained by calculation with the pressure pumped by the pump. In this case, you may have to calculate the formula more than once using different meanings internal diameter. Start with a 1-inch pipe.

Simplified calculation of heating pipe diameter

For a system with forced circulation, another formula is relevant:

D = √354 (0.86 Q/∆dt)/V,

where D is the required internal diameter, m;

V – flow velocity, m/s;

∆dt - difference in water temperatures at the inlet and outlet;

Q – energy supplied by the system, kW.

For calculations, a temperature difference of approximately 20 degrees is used. That is, at the entrance to the system from the boiler, the liquid temperature is about 90 degrees; when moving through the system, the heat loss is 20-25 degrees. and on the return the water will already be cooler (65-70 degrees).

Calculation of parameters of a heating system with natural circulation

Calculation of the pipe diameter for a system without a pump is based on the difference in temperature and pressure of the coolant at the inlet from the boiler and in the return line. It is important to consider that the liquid moves through the pipes through the natural force of gravity, enhanced by the pressure of heated water. In this case, the boiler is placed below, and the radiators are located much higher than the level of the heating device. The movement of the coolant obeys the laws of physics: more dense cold water goes down, giving way to the hot one. This ensures natural circulation in the heating system.

How to choose the diameter of the pipeline for heating with natural circulation

Unlike systems with forced circulation, natural circulation of water will require a larger cross-section of the pipe. The larger the volume of liquid circulates through the pipes, the more heat energy will enter the premises per unit time due to an increase in the speed and pressure of the coolant. On the other hand, an increased volume of water in the system will require more fuel for heating.

Therefore, in private houses with natural circulation, the first task is to develop optimal scheme heating, in which the minimum length of the circuit and the distance from the boiler to the radiators are selected. For this reason, it is recommended to install a pump in houses with large living areas.
Yulia Petrichenko, expert

For a system with natural coolant movement, the optimal flow speed is 0.4-0.6 m/s. This source code corresponds to the min resistance values of fittings and pipeline bends.

Calculation of pressure in a system with natural circulation

The pressure difference between the entry point and the return point for a natural circulation system is determined by the formula:

Δpt= h g (ρot – ρpt),

where h is the height of water rise from the boiler, m;

g – fall acceleration, g=9.81 m/s2;

ρot – density of water in the return;

ρpt – liquid density in the supply pipe.

Since the main driving force in a heating system with natural circulation is the force of gravity created by the difference in the levels of water supply to and from the radiator, it is obvious that the boiler will be located much lower (for example, in the basement of a house).

It is imperative to slope from the entry point at the boiler to the end of the row of radiators. The slope is at least 0.5 ppm (or 1 cm for each linear meter of the highway).

Calculation of pipe diameter in a system with natural circulation

Calculation of the diameter of the pipeline in a heating system with natural circulation is performed using the same formula as for heating with a pump. The diameter is selected based on the obtained minimum loss values. That is, first one value of the cross section is substituted into the original formula and checked for the resistance of the system. Then the second, third and further values. This continues until the calculated diameter meets the conditions.

How do you select the cross-section of the highway? What calculation method do you use? Please share in the comments.

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Pipe diameter for heating with forced circulation, with natural circulation: what diameter to choose, calculation formula - print version

It is not difficult for a professional to calculate the optimal cross-section of the pipeline. Practical experience + special tables - all this is enough to make the right decision. But what about the average home owner? After all, many people prefer to install the heating circuit on their own, but do not have a specialized engineering education. This article will be a good hint for those who need to decide on the diameter of the pipe for heating a private home.

There are several nuances that you need to pay attention to:

Firstly, all data obtained based on calculations using formulas are approximate. Various roundings of values, averaged coefficients - all this introduces a number of amendments to the final result.
Secondly, the specific operation of any heating circuit has its own characteristics, so any calculations provide only indicative data, “for all cases.”
Thirdly, pipe products are produced in a certain range. The same applies to diameters. The corresponding quantities are located in a certain row, with gradation by value. Therefore, you will have to select a denomination that is closest to the calculated one.

Based on the above, it is advisable to use practical recommendations professionals.

All Doo are in “mm”. In brackets - for systems with natural coolant circulation.

The total line pipe is 20 (25).
Battery outlets – 15 (20).
At – diameter 25 (32).

But these are general parameters of the circuit and do not take into account its specifics. More exact values are reflected in the table.

What is taken into account when choosing pipe diameter

Heat generator power. It is taken as a basis and determined individually for each building. What does the owner focus on when purchasing a boiler? For the total area of all heated premises. This is exactly what the manager at the point of sale will definitely clarify if the buyer has questions about this item.

On a note! It is generally accepted that to ensure high-quality heating of a house, it is necessary to adhere to the following ratio - 1 m2 / 0.1 kW. But if we take into account the peculiarities of the climate and the gentle operating mode of the unit (so as not to “drive” it to the limit), then about 30% should be added. It turns out – 1/1.3.

Coolant speed. If it is less than 0.25 m/sec, then there is a risk of airing the system and causing traffic jams on the highway. Exceeding the value of 1.5 is fraught with “noise” in the highway. This is especially noticeable when the pipes are metal, and even laid open method. But in any case, the movement of the coolant along the route will be clearly audible.

Practice has proven that for a private building (with an autonomous heating circuit) you should focus on an indicator in the range from 0.3 to 0.7. This is the optimal value for any system.

Circuit configuration. In private houses, when installing it, as a rule (regardless of the circuit), all the “threads” are connected to the collector. Each of them is “loaded” with a certain number of radiators. There is no point in purchasing pipes of the same diameter for all lines, given that the larger the cross-section of the workpiece, the higher the price of 1 running meter.

Pipe diameter. The external one does not play a special role, since products made from various materials There are differences in wall thickness. This parameter only indicates the ease of fastening the product. Inner diameter - about bandwidth tracks. It is he who is decisive.

On a note! It is customary to operate with the average value of the cross-section (the diameter of the nominal diameter). It is this parameter that is used in the calculations.

Pipe diameters are usually indicated in inches. For us, this is an unusual (non-metric) system, so you should know the rules for converting quantities. The ratio of inches to centimeters is ½.54 (or 25.4 mm). Pipe material – metal-plastic, steel, PP, PE.

Specifics of the structure. First of all, this relates to the effectiveness of its thermal insulation - what materials it is assembled from, what method is used, and so on.

The wrong choice of product diameters is fraught with many troubles: leaks (due to hydrodynamic shocks or excess pressure in the line), increased consumption of electricity (fuel) due to low efficiency of the system, and a number of others. Therefore, you should not install it according to the principle “like a neighbor (godfather, brother-in-law).”
If the circuit consists of dissimilar pipes, then special calculations will have to be made for each section (line) of the route. Separately - for plastic, metal (steel, copper), apply different coefficients and so on. Only a specialist can solve such a problem. In such situations, you should not do the calculations yourself, as the error can be quite significant. The services of a professional will cost much less than the subsequent alteration of communications, and even during the heating season.
All devices (expansion tank, battery, etc.) of the circuit are connected using pipes of the same cross-section.

To avoid the formation of air jams (in case of some errors in the calculations), so-called air vents should be installed on each line.

General heat loss of a house or apartment.
The power of heating devices (radiators) in each room.
Pipeline length.
Method of wiring the system (one-pipe, two-pipe, with forced or natural circulation).

That is, before you start calculating pipe diameters, you first calculate the total heat loss, determine and calculate. You will also need to decide on the wiring method. Using these data, you draw up a diagram and then just start calculating.

What else do you need to pay attention to? The fact is that the outer diameter of polypropylene and copper pipes is marked, and the inner diameter is calculated (subtract the wall thickness). For steel and metal-plastic ones, the internal size is indicated when marking. So don't forget this little thing.

How to choose the diameter of a heating pipe

The diameter of the heating pipes was calculated using the following formula (you can calculate it if you wish). Then the calculated values were recorded in a table.

D - required pipeline diameter, mm
∆t° - temperature delta (difference between supply and return), °C
Q - load on a given section of the system, kW - the amount of heat determined by us required to heat the room
V - coolant speed, m/s - selected from a certain range.

In individual heating systems, the coolant movement speed can be from 0.2 m/s to 1.5 m/s. Based on operating experience, it is known that the optimal speed is in the range of 0.3 m/s - 0.7 m/s. If the coolant moves more slowly, air jams occur; if it moves faster, the noise level increases significantly. The optimal speed range is selected in the table. The tables are designed for different types of pipes: metal, polypropylene, metal-plastic, copper. The values are calculated for standard operating modes: high and medium temperatures. To make the selection process more clear, let’s look at specific examples.

Calculation for a two-pipe system

There is a two-story house with heating, two wings on each floor. Polypropylene products will be used, operating mode 80/60 with a temperature delta of 20 °C. The heat loss of the house is 38 kW of thermal energy. The first floor has 20 kW, the second 18 kW. The diagram is shown below.

Two-pipe heating scheme for a two-story house. Right wing (click to enlarge)

Two-pipe heating scheme for a two-story house. Left wing (click to enlarge)

On the right is a table from which we will determine the diameter. The pinkish area is the zone of optimal coolant movement speed.

Table for calculating the diameter of polypropylene heating pipes. Operating mode 80/60 with a temperature delta of 20°C (click to enlarge)

Let's start the calculation.

We determine which pipe needs to be used in the area from the boiler to the first branch. The entire coolant passes through this section, therefore the entire heat volume of 38 kW passes through. In the table we find the corresponding line, follow it to the pink-tinted area and go up. We see that two diameters are suitable: 40 mm, 50 mm. For obvious reasons, we choose the smaller one - 40 mm.
Let's look at the diagram again. Where the flow is divided, 20 kW goes to the 1st floor, 18 kW goes to the 2nd floor. In the table we find the corresponding lines and determine the cross-section of the pipes. It turns out that we are dividing both branches with a diameter of 32 mm.
Each of the circuits is divided into two branches with equal load. On the first floor there is 10 kW each to the right and left (20 kW/2=10 kW), on the second floor 9 kW each (18 kW/2)=9 kW). Using the table, we find the corresponding values for these areas: 25 mm. This size is continued to be used until the heat load drops to 5 kW (as seen in the table). Next comes a section of 20 mm. On the first floor we go 20 mm after the second radiator (look at the load), on the second - after the third. At this point there is one amendment made by accumulated experience - it is better to switch to 20 mm at a load of 3 kW.

All. The diameters for a two-pipe system are calculated. For the return, the cross-section is not calculated, and the wiring is made with the same pipes as the supply. We hope the methodology is clear. It will not be difficult to carry out a similar calculation if all the initial data is available. If you decide to use other pipes, you will need other tables calculated for the material you need. You can practice on this system, but for an average temperature mode of 75/60 and a delta of 15°C (the table is located below).

Table for calculating the diameter of polypropylene heating pipes. Operating mode 75/60 and delta 15 °C (click to enlarge)

Determination of pipe diameter for a single-pipe system with forced circulation

Using this table we calculate interior pipe diameter for a single floor and six radiators connected in series. Let's start the calculation:

Please note again that the table above defines internal diameters. Using them you can then find the markings of pipes made of the desired material.

Features of calculating the cross-section of metal pipes

For large heating systems with metal pipes, heat loss through the walls must be taken into account. The losses are not that great, but over a long distance they can lead to the fact that the temperature on the last radiators will be very low due to the wrong choice of diameter.

Let's calculate the losses for a 40 mm steel pipe with a wall thickness of 1.4 mm. Losses are calculated using the formula:

q = k*3.14*(tв-tп)

q is the heat loss per meter of pipe,

k is the linear heat transfer coefficient (for this pipe it is 0.272 W*m/s);

tw - water temperature in the pipe - 80°C;

tп - room temperature - 22°C.

Substituting the values we get:

q = 0.272*3.15*(80-22)=49 W/s

Determining the diameter of heating system pipes is not an easy task

Despite the fact that different values (internal or external) are indicated when marking different pipes, they can be equated with a certain error. Using the table below you can find the type and marking for a known internal diameter. You can immediately find a corresponding pipe size made of a different material. For example, you need to calculate the diameter of metal-plastic heating pipes. You did not find a table for MP. But there is one for polypropylene. Select sizes for PPR, and then use this table to find analogues in MP. Naturally, there will be an error, but for systems with forced circulation it is acceptable.

Correspondence table for different types of pipes (click to enlarge size)

Using this table, you can easily determine the internal diameters of the heating system pipes and their markings.

Selection of pipe diameter for heating

This method is not based on calculations, but on a pattern that can be traced when analyzing a fairly large number of heating systems. This rule was developed by installers and is used by them on small systems for private houses and apartments.

The diameter of the pipes can be simply selected following a certain rule (click to enlarge size)

Most heating boilers have two sizes of supply and return pipes: ¾ and ½ inches. It is with this pipe that the pipe is routed until the first branch, and then at each branch the size is reduced by one step. In this way you can determine the diameter of the heating pipes in the apartment. Systems are usually small - from three to eight radiators in the system, maximum - two or three branches with one or two radiators on each. For such a system, the proposed method is an excellent choice. The situation is practically the same for small private houses. But if there are already two floors and a more extensive system, then you have to count and work with tables.

Results

For systems with forced circulation great value has a properly selected pipeline. If errors are made in calculating the diameter of heating pipes, this will affect the efficiency of heating the house.

What is needed for this

Total heat loss of the home.
What power do heating radiators have separately in each room.
The total length of the circuit pipes.
How is the system wired?

To be able to calculate the diameter of the pipes, it is necessary to determine in advance the total heat loss, the power of the boiler equipment and batteries for each room. It is also important which method will be chosen for pipe routing. Having all these parameters in hand, a future calculation scheme is drawn up.

It is also important to remember some specifics of labeling various pipes. Thus, on polypropylene pipes for heating a private house, the outer diameter is indicated (the same applies to copper products). To calculate the internal parameter, the wall thickness is subtracted from this indicator. Steel and metal-plastic pipes are marked by their internal cross-section.

Selecting the appropriate pipe diameter for heating

It is almost impossible to accurately calculate the pipeline cross-section. For these purposes, several methods are used, with approximately the same final result. As you know, the main task of the system is to deliver the required amount of heat to the batteries in order to achieve maximum uniform heating of the heating device.

In forced circuits, a pipeline, coolant and circulation pump are used for these purposes. Using this set of devices, it is necessary to supply the required portion of the coolant in a fixed time. There are two ways to achieve this task - using smaller diameter pipes in combination with a higher speed of water movement, or using a system with a larger cross-section in which the traffic intensity will be lower.

Reasons for the popularity of the first option:

Lower price for thinner pipes.
Great ease of installation.
On open areas such systems are less noticeable. If they are placed on the floor or walls, seats smaller ones are required for installation.
Narrow pipes contain less liquid. This leads to a decrease in system inertia and fuel savings.

Thanks to a set of standard diameters and a fixed amount of heat transported through them, there is no need to carry out the same type of calculations. For these purposes, special tables have been compiled: they allow, having on hand data on the required amount of heat, water supply speed and operating temperature of the heating circuit, to calculate required sizes. To determine what pipe diameters there are for heating, you need to find the necessary table.

To calculate the diameter heating pipes the following formula is used: D = √354х(0.86х Q/∆t)/V, where D is the required pipeline diameter (mm), ∆t° is the temperature delta (the difference between supply and return), Q is the load on this section of the system, kW - a certain amount of heat required to heat the room, V - coolant speed (m/s).

Autonomous systems usually have a coolant movement speed of 0.2 - 1.5 m/s. As practical experience shows, the most optimal speed in such cases is 0.3 m/s - 0.7 m/s. When this indicator decreases, there is a real threat of air jams; when it increases, the coolant begins to make a lot of noise when moving.

There are tables to select the optimal value. They contain data for pipes made of different materials - metal, polypropylene, metal-plastic, copper. When determining the diameter of heating pipes, as a rule, the emphasis was placed on standard operating conditions with high and medium temperatures. Some examples will help you understand the essence of the procedure.

Calculation of two-pipe systems

It's about two-story house with a two-pipe heating system, two wings on each floor. Polypropylene pipes are used to construct the system. Operating mode - 80/60, temperature delta - 20 degrees. The level of heat loss is 38 kW of thermal energy (first floor - 20 kW, second - 18 kW).

Calculation procedure:

First you need to decide which pipe to decorate the area between the boiler and the first branch. The entire volume of coolant is transported here, transferring heat to 38 kW. The reference data indicates two suitable parameters - 40 and 50 mm. It is more profitable to stay at a smaller diameter of 40 mm.
At the point of flow separation, 20 kW is sent to the first floor, and 18 kW to the second. According to the reference book, the section is determined. In this case, for each direction the optimal diameter is 32 mm.
In turn, each circuit includes two lines with an equal load. On the first floor, 10 kW is distributed in both directions (20 kW/2 = 10 kW), on the second floor - 9 kW (18 kW/2) = 9 kW). A suitable value for these branches would be 25mm. It is more reasonable to use this parameter until the load is reduced to 5 kW. After this, they switch to a diameter of 20 mm. The first floor is translated by 20 mm immediately behind the second radiator. The second floor usually passes after the third device. As practice shows, this transition is best carried out at a load of 3 kW.

In this way, the diameter of polypropylene pipes for a two-pipe system is calculated. There is no point in determining the dimensions of the return pipe: they are taken the same as for the supply. This procedure is simple: the main thing is to have everyone’s initial data. If you plan to use a different type of pipe to organize the system, you need to use data for a specific material of manufacture. Calculating the diameter of heating pipes with natural circulation is somewhat different.

Calculation of a single-pipe forced-type system

The principle applied is the same as in the previous case, but the algorithm of actions changes. For example, you can take the calculation of the internal diameter of a simple single-pipe heating system in a one-story house. The circuit has six radiators connected in series.

The procedure for calculating the diameter of the heating pipeline based on thermal power:

The boiler transfers 15 kW of heat to the beginning of the system. According to the reference data, this section can be equipped with 25 mm and 20 mm pipes. As in the first example, it is better to choose 20 mm.
Inside the first battery, the thermal load is reduced to 12 kW. This does not affect the cross-section of the outgoing pipe in any way: it remains the same value of 20 mm.
The third radiator reduces the load to 10.5 kW. In this case, the cross-section remains the same - the same 20 mm.
The transition to a smaller diameter of 15 mm occurs after the fourth battery, as the load is reduced to 8.5 kW.
The coolant is transported to the fifth device through a 15 mm pipe, and after it there is a transition to 12 mm.

At first glance, it may seem that calculating pipe diameters for a heating system is easy and simple. Indeed, when polypropylene or metal-plastic products are used to organize the circuit, difficulties usually do not arise. This is explained by their low thermal conductivity and small heat leaks through the walls (they can be ignored). The situation is completely different with metal products. If the steel, copper or stainless steel pipeline is of considerable length, quite a lot of thermal energy will flow through its surface.

How to calculate metal pipes

Large heating systems equipped with metal pipes, require taking into account heat loss through the walls. Although on average these figures are quite low, on very long branches the total value of lost energy is quite high. Often because of this, the last batteries in the heating circuit do not heat up well enough. There is only one reason - the diameter of the pipes was chosen incorrectly.

An example would be the determination of losses of a 40 mm steel pipe with a wall thickness of 1.4 mm. For the calculation, the formula is used q = kх3.14х(tв-tп), where q is the heat loss of a meter of pipe, k is the linear heat transfer coefficient (in this case it corresponds to 0.272 W*m/s), tв is the temperature of the water inside (+80 degrees), tп - air temperature in the room (+22 degrees).

To get the result, you need to substitute the required values into the formula:

q = 0.272x3.15x(80-22) = 49 W/s

The picture that emerges is that every meter of pipe loses heat in an amount of almost 50 W. On very long pipelines, the total losses can be simply catastrophic. In this case, the volume of leaks directly depends on the cross-section of the circuit. To take into account such losses, a similar indicator on the pipeline must be added to the indicator for reducing the thermal load on the battery. Definition optimal diameter pipeline inspection is carried out taking into account the total value of leaks.

Usually in autonomous systems heating, these indicators are not critical. In addition, during the procedure for determining heat loss and boiler power, the data obtained is usually rounded up. Thanks to this, a safety stock is created, freeing from complex calculations.

Finding relevant data

As for finding the optimal reference data, almost all websites of manufacturers of heating system components provide this information. In cases where suitable values were not found, exists special system selection of diameters. This technique is based on calculations, and not on average patterns based on processing data on a huge number of heating systems. Calculation of coolant by pipe cross-section was developed by plumbers with practical experience carrying out installation work, and is used for arranging small contours inside homes.

In the vast majority of cases heating boilers are equipped with two sizes of supply and return pipes: ¾ and ½ inches. This size is taken as the basis for wiring up to the first branch. In the future, each new branch serves as a reason to reduce the diameter by one position. This method allows you to calculate the cross-section of pipes in an apartment. We are talking about small systems with 3-8 radiators. Typically such circuits consist of two or three lines with 1-2 batteries. Small private cottages can be calculated in a similar way. If there are two or more floors, you have to use reference data.

Equation method

Although pipes made of different materials are marked different meanings(internal or external), in some cases their equation is allowed. This applies to situations where it is not possible to find data on a specific pipe: in such a situation, you can use information on a similar cross-section of a product made of a different material.

Let's say you need to calculate what diameter of a metal-plastic pipe is needed for heating, but the necessary information on this material has not been found. As an alternative, a table of coolant speed in the heating system for polypropylene products is used. Using the appropriate dimensions, the appropriate parameters for the metal-plastic pipe are selected. In this case, it is impossible to avoid inaccuracies, but in the contours forced type they are not critical.

Conclusion

Using a not very complex and branched scheme to organize the heating of your home, you can calculate the optimal pipeline diameter on your own. To do this, you need to arm yourself with information about the heat loss of your home and the power of each battery. Next, using special tables and reference books, the optimal value of the pipe cross-section is selected, which can ensure the transportation of the required volume of thermal energy to each of the rooms.

If applicable complex circuits with many elements, it is advisable to invite a professional plumber to calculate them. If you have confidence in your own abilities, it is still recommended to consult with a specialist. There are cases when, due to mistakes made, it is necessary to undertake an expensive reconstruction of the entire circuit.