Conduct village house heating pipe diameter. Thick and thin: how to calculate the diameter of a pipe for heating. All about two-pipe heating systems

The construction of a heating system for a private house should begin with a thorough study of the project. The project must take into account all parameters that can affect the energy efficiency of the future heating system.

This includes the selection of a suitable boiler, batteries, layout, selection of pipe material and connecting elements. An equally important parameter is the correct calculation of the diameter of the pipelines.

Some will think that the definition required diameter pipes for a heating system is by no means a difficult task. It would seem that what requirements can be presented to the pipe, the only task of which is to deliver the coolant to the radiators.

Meanwhile, an incorrectly selected diameter of the pipe (or collector) can adversely affect the operation of the entire heating system. The movement of fluid through a pipeline is accompanied by numerous complex processes, for the description of which there is a special branch of physics - hydrodynamics.

Without delving into the scientific jungle, it is possible, nevertheless, to determine a number of fundamental characteristics that directly depend on the diameter of the pipeline:

The rate of spread of the liquid. It affects the optimal distribution of heat over the heating radiators, preventing the coolant from cooling below the minimum temperature value. In addition, the noise level of the operating heating system will directly depend on the propagation speed.
Heat carrier volume. On the one hand, an increase in the diameter of the pipes will help reduce losses from fluid friction on the inner surface of the pipeline. On the other hand, with an increase in the cross section of the pipe, the total volume of the coolant in the system will increase, and more energy will be required to heat it.
hydraulic losses. Occur at the joints of pipes of different diameters. The more transitions there are in the heating system, the more losses of this kind will result in the end.

Comfortable existence of residents of modern country house provides a powerful network of various engineering communications, among which one of the main places is occupied by the system responsible for heat. When planning to mount it on their own, almost every owner wonders what pipe diameter to choose for heating a private house. For many, this becomes a real problem, since both the final cost and the efficiency of the heating system depend on it.

Factors affecting the choice of pipes

The choice of the diameter of pipes for heating a private house plays a really important role, since the throughput of the heating system, as well as its thermal and hydraulic losses, will depend on this parameter. In addition, it is imperative to take into account the scale of the system being installed, namely the number of radiators and rooms requiring heating. Many people think that the larger the diameter of the pipe for heating a private house, the greater its throughput, which means that the number of radiators can be increased.

However, it is unlikely that it will be possible to increase efficiency in this way. Not only will the purchase of pipes with an unreasonably large cross section entail additional costs, but there will also be a risk of a pressure drop in the system to a critical value and, as a result, a decrease in efficiency.

Thermal engineering calculation

The calculation of the diameter of heat supply pipes is carried out taking into account the material from which they are made, the length of the circuit, the wiring diagram and the principle of circulation of the coolant. It is quite difficult to independently perform the calculation correctly, especially if there is no experience in such matters. It is best to contact a specialist who can develop a competent heating project for a private house to resolve this issue.

When compiling it, the following parameters of the future heating system must be taken into account:

wiring diagram, on the basis of which the total length of the pipes is calculated;
coefficient of resistance of a pipe for a heating system to fluid flow (this indicator is affected by the size, material and smoothness of the inner surface of the product);
sections of the outlet and inlet pipes of the boiler (usually they are identical);
the inner diameter of the pipe for heating a private house (the inner section is indicated in millimeters or inches; 1 inch = 25.4 mm);
coolant cooling level;
the maximum rate of movement of the coolant;
the amount of heat that will need to be transferred from the heating boiler to all radiators.

Calculation principle

When drawing up a heating project for a private house, the specialist focuses on the optimal indicators that must be achieved when creating a new system. For example:

The speed of water movement in the system should not exceed 1.5 m/s. The best option is from 0.3 to 0.7 m / s.
The degree of cooling of the water coolant (the temperature difference in the water entering the boiler and leaving it) should be in the range of 15-20 degrees.
The amount of heat required by the system must be equal to the total power of all radiators (the maximum indicator is taken from the passport). For heating 10 sq. meters of area of the insulated room requires 1 kW plus a margin of 15-20%.

Natural circulation systems

The maximum diameter of the pipe for heating a private house equipped with a heating system with natural or combined circulation must correspond to the dimensions of the inlet and outlet pipes of the boiler (most often they are the same). Pipes of this section will be needed to complete the initial and final sections of the circuit.

If we talk about which pipe for heating a private house is better, then we must take into account the type of boiler. So for solid fuel boilers, it is recommended to use metal products. If you plan to use polymer pipes, then a metal pipe should still be used to install the first couple of meters.

The starting diameter is the largest. It is kept until the first branching. Further, the wiring is performed with a gradual decrease in the diameter of the pipes after each branch. At the last point, the diameter should correspond to ½ inch (12.7 mm) or ¾ inch (19 mm). When installing the "return" the same principle applies.

Forced circulation systems

Such systems usually operate on gas or electric boilers. The diameter of the pipes for them should be chosen as small as possible, since the forced circulation is provided by the pump. The expediency of small diameter pipes is explained by the following factors:

a smaller section (most often these are polymer or metal-plastic pipes) allows minimizing the volume of water in the system and, therefore, accelerating its heating (the inertia of the system decreases);
installation of thin pipes is much easier, especially if they need to be hidden in the walls (making strobes in the floor or walls requires less labor);
pipes of small diameters and connection fittings they are cheaper, therefore, the total cost of installing the heating system is reduced.

With all this, the size of the pipes should optimally correspond to the indicators provided for by technological calculations. If these recommendations are not followed, the efficiency of the heating system will decrease and its noise level will increase.

Connecting radiators

With a collector wiring diagram, the boiler and collectors are connected by pipes of a larger cross section (from 19 to 25 mm). Distribution from the manifolds is carried out using thin pipes, the internal diameter of which is 12.7 mm (1/2 in.).

radiators as well optional equipment, in particular, a safety unit, a pumped storage tank, etc., are also connected with half-inch pipes.

Types of radiators

Regarding what kind of heating is better for a private house, the reviews of the owners are quite diverse, but as for radiators, many prefer aluminum models. The fact is that the power of heating batteries depends on the material. They are bimetallic, cast iron and aluminum.

One section bimetal radiator has a standard power of 100-180 W, cast iron - 120-160 W, and aluminum - 180-205 W.

When buying radiators, you need to find out exactly what material they are made of, since this is the indicator that is required for the correct calculation of power.

for heating

Heated water is transported from the boiler to the radiators through pipes, so their quality directly affects the level of heat loss. On the market building materials There are currently three types of pipes:

metal;
copper;
metal-plastic.

Each species has its own characteristics, which will be discussed below.

metal pipes

This option was previously widely used in heating systems of multi-storey and private houses. Metal pipes are gradually becoming a thing of the past, as they are not characterized from the best side. Their disadvantages include:

big weight;
problematic installation (required professional equipment);
ability to accumulate static electricity;
limited service life due to inability to resist rust.

Copper pipes

Such products have a number of advantages, for example:

the ability to withstand high temperatures (within 200 degrees);
high strength (maximum pressure - 200 atmospheres);
durability (not subject to corrosion).

However, copper pipes are not popular, and the reasons for this are as follows:

complexity of installation (requires professional equipment and special skills);
for the installation of copper pipes, special brackets are required;
high price (copper is an expensive material);
high cost of work due to their labor intensity.

Metal-plastic pipes

This type of pipe is the most popular among consumers. Such products are available in a wide range of sizes and are ideal for the installation of heating systems. They have the following advantages:

increased strength and durability (aluminum or fiberglass base coated with plastic generally creates a high-strength structure that does not collapse over time and is resistant to mechanical damage);
resistance to corrosion processes (sealed outer coating does not allow air to pass through);
minimum hydraulic resistance (such pipes are ideal for heating systems with natural and forced water circulation);
have antistatic properties;
simplicity and high speed of installation (installation does not require professional knowledge, it is enough to familiarize yourself with the installation technique on the Internet and purchase a special soldering iron);
low cost of pipes of any diameters and accessories to them.

Reliable connection of elements is provided by special elements - fittings. If metal-plastic pipes must be connected to metal or stop valves, flanges or adapters for a threaded connection are used.

When installing a heating system from pipes and fittings reinforced with fiberglass, the operation for stripping these elements is not required, which greatly speeds up and simplifies the work.

Thus, plastic pipes are the best option for self-assembly heating system. The main thing is to choose the right number and diameter of pipes and accessories (fittings).

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

The calculation of 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 consist 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 a 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 right pipe diameter in order to prevent unpleasant moments in subsequent operation.

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

Dependence of heating efficiency on the diameter of pipelines

The full operation of the energy system depends on the criteria:

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

The incorrect statement is that the larger the pipe section, the more liquid it will let through. In this case, an increase in 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, at large diameter pipes and the increased length of the mains, its power may not be enough to provide the required pressure. In case of power outages, the use of 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 central heating, the diameter of the pipes is the same as for city apartments. In houses with steam heating, the diameter of the boiler must be carefully calculated. 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, the heating scheme (one-, two-pipe) are taken into account. Table 1 shows the approximate losses of the coolant depending on the material and the life of the pipelines.

Table 1. Coolant losses

Pipe	Consumption m3/h	Speed m/s	Head loss m/100m
Steel new 133x5	60	1,4	3,6
Steel new 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
Steel new 245х6	400	2,6	4,3
Steel old 245х6	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
Steel new 630х10	3000	2,85	1,33
Steel old 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
Steel new 820х12	4000	2,23	0,6
Steel old 820x10	4000	2,23	0,87
PE 100 800x47.4 (SDR 17)	4000	2,85	0,59
PE 80 800-58.8 (SDR 13.6)	4000	3,0	0,69

An overly small pipe diameter will inevitably lead to the formation of a high pressure, which will cause an increased load on the connecting elements of the line. In addition, the heating system will be noisy.

Heating system wiring diagram

For the correct calculation of 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 top and bottom placement of highways. 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 the pump to be included in the circuit.

Horizontal wiring provides 3 types:

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

In the single-pipe wiring scheme, it is possible to provide a bypass pipe, which will be a backup line for the circulation of liquid 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 scheme of the heating system, one can easily calculate the total length, possible delays in the coolant flow in the main (at bends, turns, at joints), and as a result, obtain a numerical value of the system resistance. According to the calculated value of losses, it is possible to select the diameter of the heating mains using the method discussed below.

Choosing 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 the mains 220 V. It turns on automatically (through a sensor) when the pressure in the system rises (that is, when the liquid is heated). The pump quickly disperses hot water through the system, which stores energy and actively transfers it through radiators to every room in the house.

Heating with forced circulation - the 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, it is important for the pump in the heating system to ensure uninterrupted power supply. Otherwise, heating simply will not work with a large area of \u200b\u200bthe house.

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

The calculation begins by determining the total area of \u200b\u200bthe room that needs to be heated in winter time, that is, this is the entire residential part of the house. The standard for heat transfer of the heating system is 1 kW for every 10 square meters. m. (with walls with insulation and a ceiling height of up to 3 m). That is, for a room of 35 sq.m. the norm will be 3.5 kW. To ensure the supply of thermal energy, we add 20%, which results in 4.2 kW. According to table 2, we determine a value close to 4200 - these are pipes with a diameter of 10 mm (heat indicator 4471 W), 8 mm (index 4496 W), 12 mm (4598 W). These numbers are characterized by the following values of the flow rate of the coolant (in this case, water): 0.7; 0.5; 1.1 m/s. Practical indicators of the normal operation of the heating system - speed hot water from 0.4 to 0.7 m/s. Taking into account this condition, we leave for 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. It is this product that will be included in the project.

It is important to distinguish between the diameters by which the choice is made: external, internal, conditional passage. As a rule, steel pipes are selected according to the inner diameter, polypropylene pipes - according to the outer diameter. A beginner may encounter the problem of determining the diameter marked in inches - this nuance is relevant for steel products. Translation of inch dimension into metric is also carried out through tables.

Calculation of pipe diameter for heating with a pump

When calculating heating pipes the most important characteristics are:

The amount (volume) of water loaded into the heating system.
The length of the highways is total.
Flow velocity 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 off (natural circulation).
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 is the resistance coefficient of pipes;

L is the length (length) of the system;

D is the inner diameter (the desired value in this case), m;

V is the flow velocity, m/s;

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

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

When calculating the diameter of pipes for heating, L is taken equal to the length of the pipeline from the boiler to the radiators and in the opposite direction, without taking into account duplicate sections placed in parallel.

The whole calculation ultimately boils down to comparing the calculated resistance value with the pressure pumped by the pump. In this case, you may have to calculate the formula more than once using different values of the inner diameter. Start with a 1" pipe.

Simplified calculation of the diameter of the heating pipe

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

D = √354 (0.86 Q/∆dt)/V,

where D is the desired inner diameter, m;

V is the flow velocity, m/s;

∆dt - temperature difference between inlet and outlet water;

Q is the energy given off by the system, kW.

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

Calculation of parameters of a heating system with natural circulation

The 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 by means of the natural force of gravity, enhanced by the pressure of heated water. In this case, the boiler is placed below, and the radiators are much higher than the level of the heater. The movement of the coolant obeys the laws of physics: denser cold water goes down, giving way to hot. This is how natural circulation in the heating system is carried out.

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

Unlike systems with forced circulation, the natural circulation of water will require an overall cross-section of the pipe. The larger the volume of liquid will circulate 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 to heat up.

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

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

Pressure Calculation in a Natural Circulation System

The pressure difference between the entry point and the return 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 is the density of water in the return;

ρpt is the density of the liquid 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. Slope - not less than 0.5 ppm (or 1 cm per linear meter of the highway).

Calculation of the pipe diameter in a natural circulation system

The calculation of the diameter of the pipeline in a heating system with natural circulation is carried out according to the same formula as for heating with a pump. The diameter is selected based on the obtained minimum loss values. That is, one value of the cross section is first substituted into the original formula, and the resistance of the system is checked. Then the second, third and further values. So until the moment when the calculated diameter does not satisfy the conditions.

And how do you choose the section of the highway? What calculation method do you use? Please share in the comments.

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The diameter of the pipe for heating with forced circulation, with natural circulation: which diameter to choose, the calculation formula is print version

D - DN (outer diameter); d1 - nominal bore (inner diameter)

The question of what should be the diameter of the pipes for heating in a private house and in an apartment does not cease to arise for those who plan to independently assemble the circuit. In this article you will find the calculation of the diameter of the pipe for heating. We will not dwell on the principle of operation of both types of contour, this is material for another article. Here we simply compare the advantages and disadvantages of each of them. Based on the results, some myths will be debunked, and based on the facts, you will be able to draw your own conclusions.

Two-pipe circuit in a high-rise apartment

In order to properly make heating in an apartment of a multi-storey building, you need to plan everything from the very beginning. One of the key points in planning is the calculation of the diameter of the pipe for heating. The technical part of the case is called hydraulic calculation. At the same time, the following factors influence the choice of the diameter of pipes for heating:

the length of the system;
supply coolant temperature;
return temperature;
materials and accessories;
area of the room;
the degree of fatigue in the room.

In other words, before calculating the diameter of the pipe for heating, it is necessary to determine the hydraulic performance of the system. You can only make approximate calculations on your own, which can also be used in practice.

Sealed two-pipe system

The diameter of the pipes for a two-pipe heating system directly determines how quickly the heat from the boiler will reach the end point of the circuit. The smaller the conditional passage, the higher the coolant velocity. Based on this, we can conclude that if the diameter of the heating pipe in the apartment is incorrectly chosen upwards, the coolant speed will drop, and with it the temperature in the last radiator will be lower. After all, water over a longer amount of time will have time to give off a greater amount of heat.

by the most simple solution how to calculate the diameter of a pipe for heating is to adhere to the same conditional passage as in the branch pipe that goes into your apartment from the central riser. This will save you time and nerves, because it was no coincidence that the developer installed a circuit with just such a section. Before the object began to build, all calculations were carried out, including hydraulic. If you want to calculate everything according to the formula, then use the information from the next block.

The optimal diameter of a pipe for heating in an apartment and in a private house up to 100 sq m is 25 mm. This applies to products made of polypropylene.

Two-pipe circuit in a private house

First, let's generalize a bit. Take for example the calculation of the diameter of pipes made of polypropylene for heating in a private house. Basically, products with a cross section of 25 mm are used for the circuit, and 20 mm are placed to the radiators. Due to the fact that the size of pipes for heating in a private house, used as branch pipes to batteries, is smaller, the following processes occur:

coolant speed increases;
improves circulation in;
the battery warms up evenly, which is important when connecting at the bottom.

Combinations of 20 mm main loop diameter and 16 mm elbows are also possible.

To verify the above data, you can calculate the diameter of the pipes for heating a private house on your own. This will require the following values:

square footage of the room.

Knowing the number of heated square meters, we can calculate the power of the boiler and what pipe diameter to choose for heating. The more powerful the heater, the larger the section of the product can be used in tandem with it. For heating one square meter the premises will require 0.1 kW of boiler power. The data is valid if the ceilings are standard 2.5 m;

heat loss.

The indicator depends on the region and. The bottom line is that the greater the heat loss, the more powerful the heater should be. To get around complicated calculations that are inappropriate in the approximate calculation, you just need to add 20% to the boiler power calculated above;

the speed of the water in the circuit.

The coolant velocity is allowed in the range from 0.2 to 1.5 m/s. At the same time, in most calculations of the diameter of pipes for heating with forced circulation, it is customary to take an average value of 0.6 m / s. At this speed, the appearance of noise from the friction of the coolant against the walls is excluded;

how cool the coolant is.

To do this, the return temperature is subtracted from the supply temperature. Naturally, you cannot know the exact data, especially since you are at the design stage. Therefore, operate with average data, which are 80 and 60 degrees, respectively. Based on this, heat loss is 20 degrees.

Now the calculation itself is how to choose the diameter of the pipe for heating. To do this, take a formula in which initially there are two constants, the sum of which is 304.44.

Nominal passage of the circuit, squared = 304.44 x (squaring of the room x 0.1 kW + 20%) / heat loss of the coolant / flow rate.

The last action is the extraction of the square root of the result. For clarity, let's calculate what pipe diameter to use for heating a private house with one floor with an area of 120 m 2:

304.44 x (120 x 0.1 + 20%) / 20 / 0.6 = 368.328

Now we calculate the square root of 368.328, which is equal to 19.11 mm. Before choosing the diameter of the pipe for heating, we once again emphasize that this is the so-called conditional passage. Products made of different materials have different wall thicknesses. So, for example, polypropylene has thicker walls than metal-plastic. Since we have used a polypropylene contour as a sample, we will continue to consider this material. The marking of these products indicates the outer section and wall thickness. Using the subtraction method, we find out the value we need and select it in the store.

The ratio of outer and inner diameter polypropylene pipes

For convenience, we use a table.

Based on the results of the table, we can conclude:

if a nominal pressure of 10 atmospheres is sufficient, then the outer section of the pipe for heating is 25 mm;
if a nominal pressure of 20 or 25 atmospheres is required, then 32 mm.

Single pipe system

Scheme of a single-pipe heating system

Before determining the diameter of the heating pipe, consider two types of single-pipe circuits:

gravity;
with forced circulation.

The difference is that in open system the coolant circulates by gravity, and in a sealed one with the help of pumps. Expansion and their location also differ.

In order for the water in the open circuit to be able to circulate, it is necessary that the conditional passage be large. So much so that the system is very striking. This type of circuit is applicable only in private houses, while in apartments it is possible to install only hermetic systems.

Pipe diameter for a single-pipe heating system closed type may differ in different parts of it so that the contour is balanced.

For small housing, nozzles with the same conditional passage are used. In principle, in order to determine what diameter of pipes for heating with natural circulation is needed, you can use the formula already known to us. It should be borne in mind that polypropylene products smaller than 32 mm are not used, even for small rooms.

Comparison of one-pipe and two-pipe systems

We have already figured out how to calculate pipes for heating, and what diameter is needed for both types of systems. For closed circuits, with a room area of 120 m 2, this figure is 32 mm for polypropylene. In this case, the conditional passage for products with a nominal pressure of 20 and 25 atmospheres is 21.2 mm. For products with a nominal pressure of 10 atmospheres, the nominal bore is 20.4 mm, and the outer diameter is 25 mm.

Efficiency - unequivocally, "rides" heat the room more efficiently than single-pipe ones;
cost savings - all that can be saved at Leningradka is some section of the contour and that's it.

The number of tees will be the same, the taps too, but more adapters may be required. Imagine a circuit from which two branch pipes leave with a small gap. One of them goes to the radiator inlet, and the second returns the coolant back to the system. It turns out that the segment between the nozzles is a bypass. In order for the circulation in the battery to be better, the bypass must be made of a smaller diameter than the main heating circuit. From this it follows that a couple more pieces of fittings will be required. It turns out that we spend less money on pipes and more on fittings, as a result, there is no savings, while the efficiency is lower.

As a result, from this we can conclude that the stories about what a good and cheap one-pipe heating system are simply untenable.

For systems with forced circulation, a properly selected pipeline is of great importance. If errors are made in the calculation of the diameter of pipes for heating, this will affect the efficiency of heating the house.

What is needed for this

The total heat loss of the dwelling.
What power do the heating radiators have separately in each room.
The total length of the pipes of the circuit.
How the system is divorced.

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. Of considerable importance is also what method will be chosen for piping. With all these parameters in hand, a scheme for the future calculation is drawn up.

It is also important to remember some specifics of marking various pipes. So, 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 with an internal section.

Choosing the right pipe diameter for heating

It is almost impossible to accurately calculate the cross section of the pipeline. For these purposes, several methods are used, with an approximate identity of the 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 uniformity of heating of the heater.

In forced circuits for these purposes, a pipeline, coolant and circulation pump. 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 accomplish this task - using pipes of a smaller diameter in combination with a higher speed of water movement, or using a system with a larger section, in which the movement will be less.

Reasons for the popularity of the first option:

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

Thanks to a set of typical 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 were compiled: they allow, having on hand data on the required amount of heat, water supply rate and operating temperature of heating the circuit, to calculate the right dimensions. To determine what pipe diameters are for heating, you need to find the desired table.

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

Autonomous systems usually have a coolant velocity 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. With a decrease in this indicator, there is a real threat of air congestion, with an increase, the coolant begins to make a lot of noise during movement.

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

Calculation of two-pipe systems

It will be about two-story house with a two-pipe heating system, two wings on each floor. Polypropylene pipes are used to equip 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 floor - 18 kW).

Calculation procedure:

First you need to decide which pipe to arrange the section between the boiler and the first branch. The entire volume of the coolant is transported here, transferring heat in the amount of 38 kW. Reference data indicate two suitable parameters - 40 and 50 mm. It is more profitable to stop 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 handbook, 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 equivalent load. On the first floor, 10 kW diverges in both directions (20 kW / 2 \u003d 10 kW), on the second floor - 9 kW (18 kW / 2) \u003d 9 kW). Suitable values for these branches would be 25 mm. This parameter it is more reasonable to use it until the load drops to 5 kW. After that, 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 fixture. As practice shows, this transition is best done at a load of 3 kW.

Thus, the calculation of the diameter of polypropylene pipes for a two-pipe system is carried out. It makes no sense to determine 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 all the initial data. If the organization of the system involves the use of pipes of a different type, you need to use data for a specific material of manufacture. The calculation of the diameter of pipes for heating with natural circulation is somewhat different.

Calculation of a one-pipe forced type system

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

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

The boiler transfers 15 kW of heat to the beginning of the system. According to 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 heat load is reduced to 12 kW. This does not affect the cross section of the outgoing pipe in any way: it remains at the same value of 20 mm.
The third radiator reduces the load to 10.5 kW. At the same time, the cross section remains the same - all 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.
To the fifth device, the coolant is transported through a 15 mm pipe, and after it there is a transition to 12 mm.

At first glance, it may seem that the calculation of pipe diameters for a heating system is easy and simple. Indeed, when polypropylene or metal-plastic products are used to organize the contour, there are usually no difficulties. This is due to their low thermal conductivity and small heat leakage through the walls (they can be ignored). The situation is completely different with metal products. If a steel, copper or stainless pipeline has a decent length, a lot of heat energy will flow through its surface.

How to calculate metal pipes

Large heating systems equipped with metal pipes, require taking into account heat losses through the walls. Although on average these figures are quite low, however, on very long branches, the total value of the 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 for this - the diameter of the pipes was chosen incorrectly.

An example is the definition of losses steel pipe 40 mm, with a wall thickness of 1.4 mm. For the calculation, the formula q \u003d kx3.14x (tw-tp) is used, where q is the heat loss of a pipe meter, k is the linear heat transfer coefficient (in this case it corresponds to 0.272 W * m / s), tw is the water temperature inside (+80 degrees), tp - air temperature in the room (+22 degrees).

To get the result, you need to substitute the necessary values \u200b\u200binto the formula:

q \u003d 0.272x3.15x (80-22) \u003d 49 W / s

Such a picture emerges that each meter of the pipe loses heat in the amount of almost 50 watts. On very long pipelines, the total losses can be simply catastrophic. In this case, the volume of leaks directly depends on the section of the circuit. To take into account such losses, it is necessary to add a similar indicator for the pipeline to the indicator for reducing the thermal load on the battery. The determination of the optimal diameter of the pipeline 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 the heat loss and power of boilers, the data obtained are usually rounded up. This creates a safety margin that frees you from complex calculations.

Finding relevant data

As for the search for optimal reference data, almost all websites of manufacturers of heating system components provide this information. In cases where suitable values have not been found, there is a special system for selecting diameters. This technique is based on calculations, and not on average patterns based on the processing of data on a huge number of heating systems. The calculation of the coolant according to the pipe section was developed by plumbers with practical experience in carrying out installation work, and is used for arranging small contours inside dwellings.

In the vast majority of cases heating boilers Available with two sizes of inlet and return fittings: ¾" and ½". This dimension is taken as the basis for wiring up to the first branch. In the future, each new branch serves as a reason for reducing 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 from different materials are marked with different values (internal or external), in some cases their equalization is allowed. This applies to situations where it is not possible to find data on a specific pipe: in such a situation, information on a similar section of a product made of another material can be used.

Suppose you want to calculate what diameter metal-plastic pipe needed for heating, but the necessary information on this material was not found. As an alternative, a heat carrier velocity table 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 do without inaccuracies, however, in forced-type circuits, they are not critical.

Conclusion

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

If applicable complex schemes 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 deal with an expensive reconstruction of the entire circuit.