What diameter of polypropylene pipes for heating should I choose?

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

The question of what the diameter of heating pipes should be in a private house and apartment never ceases to arise among those who plan to assemble the circuit themselves. In this article you will find a calculation of the diameter of a heating pipe. We will not dwell on the operating principle of both types of circuit; this is material for another article. Here we will simply compare the advantages and disadvantages of each of them. As a result, some myths will be debunked, and based on the facts, you will be able to draw your own conclusions.

Water supply to the boiler: natural two-pipe heating in Leningrad

Gravity supply of water to the boiler is feasible with a centralized water supply to the area.
But if the developer receives water from the well individually, a circulation pump for heating is needed to supply and circulate the water. The heating system uses a circulation pump that optimizes the speed of the coolant and ensures that the cooled liquid is returned to the boiler. The pump simultaneously solves the problem of air pockets, which are simply washed away by the constantly flowing coolant. For the heating system of a private home, it is recommended to choose a self-regulating pump with a wet rotor, which during operation comes into contact with the coolant. This pump operates silently, is able to adapt itself to changes in the operation of the boiler, it is economical and durable. Its power and efficiency are sufficient for a cottage.

Pressure gauges allow you to control pressure.

Monitoring the pressure in the heating system is mandatory, since a failure can occur at any moment and you need to really understand the operating pressure

The optimal pressure for a home heating system should be one and a half to two atm. Pressure jump up to 3 atm. Can rupture boiler, pipes or radiators. And in order to avoid a sharp increase in pressure in the heating system due to increased water pressure, an expansion tank is installed at the outlet of the boiler.

Dimensions depending on application

The good processability of cast polypropylene and simple production technology are causing the gradual displacement and replacement of polyethylene pipes with polypropylene pipes. In addition, polymers of the PPB, PPH, PPR brands are considered safer in comparison with their closest competitors - polyvinyl chloride and polyethylene.

Dimensions of polypropylene pipes for ventilation

The standard diameter of ventilation ducts is 110-200 mm. This is enough to remove polluted air through the hood in the kitchen, bathroom, or in any residential or non-residential area of ​​a house or apartment. Ventilation systems for office premises are equipped with pipes up to 250 mm.

Installation is performed by mechanical pipe-socket assembly. It will not be possible to replace ventilation based on RRV pipes with polyethylene or polyvinyl chloride.

Polyethylene air ducts are prone to electrification and the accumulation of dust plugs that clog filters and heat exchangers. PVC should not be used on air ducts for fire safety reasons.

In addition, PPV pipes have greater rigidity than blanks made of vinyl or polyethylene. For example, it is almost impossible to crush the walls of a standard 16x2.2 mm polypropylene pipe blank with your fingers. Whereas similar products made of polyethylene or vinyl wrinkle easily.

Therefore, ventilation is made of polypropylene with a diameter of up to 1200 mm with an SDR index of tens of units. Under load, the walls do not wrinkle and withstand any pulsations and fluctuations in air flow.

Dimensions of polypropylene pipes for sewerage

For waste and sewer systems, pipes made of PPH polymer are used. The material's chemical resistance is almost equal to PVC, but it has higher water resistance and, most importantly, wall rigidity.

This means that propylene sewer pipes can be manufactured with a high SDR index:

• the weight of the pipe blank is less, which means the sewage system will be cheaper;
• the joint on the rubber seal will not leak;
• locks at the joints of polypropylene pipes practically do not have such defects.

For domestic sewers, PPH blanks with a diameter of 25, 50, 110 mm are used. To drain sewage from the house, pipes measuring 300-550 mm are used.

Dimensions of polypropylene pipes for water supply and heating

For piping a boiler or distributing a centralized heating system, hot water pipes of the PPR brand, class PN20, SDR index 6-7 units are used. Dimensions – 20-40 mm.

PPR - PN10 with an SDR index of more than 10 is installed on the return line feeding the main or water supply. The cross-sectional dimensions of the pipelines are determined by the second water flow. For the hot section, pipes reinforced with fiberglass or aluminum foil are installed. Otherwise, the soldered joint between the fitting and the hot propylene wall under pressure may leak.

There are many models of PPR pipes on the market. Despite the fact that pressure polypropylene pipes of different brands are made of almost the same material, and there are differences between them in the range of sizes. Any manufacturing company has its own catalog of polypropylene pipe sizes; it will help you make a choice.

We can recommend, as an option, the following models:

1. Pipes marked PVPP-RCT UNI are easily distinguished by their characteristic green longitudinal stripe. Transverse dimensions - from 16x2.2 mm to 250x22.7. It is believed that hydraulic losses in water pipes of small cross-section are less than in analogues.
2. Pipe blanks marked PVPP-RCT FASER with an orange longitudinal stripe, cross-section 20x2.8 mm, are most popular for supplying hot water under pressure up to 25 bar. It features a coefficient of thermal expansion reduced by more than three times.
3. PVPP-RCT is designed for high temperature and pressure of the internal environment. Dimensions from 20x2.8 mm, PN index can exceed 25 units. Marked with a red stripe.
4. For main water supply, PVPP-R CT FASER pipe blanks are used. The input diameter can be 40x3.7 mm or more.
5. At the entrance to the apartment, polypropylene pipes of the PP-RCT brand, with a diameter of 25x4.2, are used. The NOT series for hot water and the CLASSIC series for cold water.

You can assemble a water supply using propylene pipes of any type and size. But it is still better to install pipe blanks of the appropriate size and cross-section. This will save money, and the water supply will not make noise or hum due to fluid fluctuations in the flow.

Special cases

Polypropylene pipes are widely used as a substitute for aluminum or steel profiles. From pipe blanks with an outer diameter of 25 mm, you can easily solder the frame of a small greenhouse with a base size of 200x400 cm. It is better to use polypropylene sections with an SDR index of at least 5; the wall thickness is 5.1 mm. This is enough to bend the arched vault and screw self-tapping screws into the wall to attach crossbars or fix the stretched film.

From the polypropylene scraps remaining after assembling the heating circuit, you can make heated floors for a loggia or balcony. The room itself will need to be thoroughly insulated along the walls, ceiling and floor. Foiled polyethylene foam is laid under the pipes. For the heating circuit we use polypropylene blanks of the PPS brand, 25 mm in size and SDR index equal to 10. Thin walls conduct heat well, and the material is not afraid of freezing down to -20 ℃.

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 come with supply and return pipes of two sizes: And ? 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.

This article tells you how to choose the pipe diameter for a metal-plastic and polypropylene pipe for a private house with an area of ​​up to 300 sq.m. But you can also choose the diameters of other pipes, taking into account the internal diameter of the other pipeline.

How to choose the correct pipe diameter is shown in the examples below.

What diameter of pipes to choose also depends on the criteria of the heating system; this is also written below (see section Criteria for choosing diameters).

More about the program

Everything is very simple and you don’t even need to do a hydraulic calculation, which is written about here: Hydraulic calculation of a heating system

You can use the formula to find the diameter, or you can cut down on the calculation time and just select the diameter from the table below.

Formula for finding pipeline diameters

Coolant velocities are selected for a head loss of 150 Pa/m; below is an explanation of why this speed is chosen.

In the boiler branch, you can increase the coolant speed to the level of economic justification (for example, up to 1 m/sec.). Because on the boiler branch the cost of the fittings may be higher and the pressure losses may be exceeded, because this does not affect the even distribution of costs between the branched branches.

Selecting the pipeline diameter according to the table

Knowing only the power of heating devices (radiators) or the heat loss of the room, you can select the pipe diameter from the table below:

Diameters for polypropylene pipes

Diameters for metal-plastic pipes

Diagram for example of diameter selection

Description of an example of diameter selection

Each radiator is connected with an MP16 mm pipe, because the radiator power does not exceed 3200 W, indicated in the table for choosing diameters. (see table above). If the radiator exceeds the power of 3200 W, then select MP20 mm. If the radiator power is 4000 W, then choose MP20 mm.

Diameter of pipe section B-B

, marked in red letters. The section of pipe between the 2nd and 3rd radiator.

Pipe section B-B delivers coolant 3 and 4 to the radiator. The total power of these radiators is 2000 W + 2000 W = 4000 W.

For the B-B pipe section, MP20 mm is selected, because the power of the 4000 W pipe section is more than 3200 W and less than 6700 W. (see table above).

Diameter of pipe section A-B

Power of section A-B = sum of powers of 2,3 and 4 radiators = 2000 + 2000 + 2000 = 6000 W.

For pipe section A-B, MP20 mm is selected, because the power of a pipe section of 6000 W is more than 3200 W and less than 6700 W. (see table above).

Diameter of pipe section A-G

Total power of 1,2,3 and 4 radiators = 3000 + 2000 + 2000 + 2000 = 9000 W.

For the pipe section A-G, MP26 mm is selected, because the power of the 9000 W pipe section is more than 6700 W and less than 12400 W. (see table above).

Diameter of pipe section D-E

Total power of 6 and 7 radiators = 1500 + 1500 = 3000 W.

For pipe section D-E, MP16 mm is selected, because the power of a pipe section of 3000 W does not exceed 3200 W.

Diameter of the pipe section G-D

Total power of 5,6 and 7 radiators = 3000 + 1500 + 1500 = 6000 W.

For the G-D pipe section, MP20 mm is selected, because the power of the 6000 W pipe section is more than 3200 W and less than 6700 W.

Pipe diameters for boiler line

The calculation of diameters is selected based on the flow rate of the coolant, because economic calculations show that a lot of fittings are installed in the boiler line, which are more expensive than fittings of a smaller diameter. Also in the boiler circuit we can add hydraulic resistance, and this will not affect the flow rates between the radiators, because this is one main line in which flow balancing does not need to be done.

Power of all radiators = 3000 + 2000 + 2000+ 2000 + 3000 + 1500 + 1500 = 15000 W.

The power of the boiler circuit is selected at a speed of 0.7 m/sec.

We choose MP26 mm, because the power of a pipe section of 15000 W is more than 11700 W and less than 18500 W. (see table above for boiler circuit).

If it is problematic to use a large diameter, then you can limit yourself to a speed of 1 m/sec. For example, you use a metal-plastic pipe, and the diameter is 40 mm. no, then you can choose the diameter at a speed of 1 m/sec. There is also fittings with a diameter of 40 mm. may greatly exceed prices that will not pay off soon. It will be cheaper to buy a more powerful pump to compensate for these losses. It also happens that it is more profitable to spend more electricity than to buy expensive fittings that will pay for themselves for more than 20 years.

Diameter selection criteria

For which heating system are these diameters suitable:

House up to 300 sq.m. 10 x 10 meters. The perimeter of the house is 40 meters.

Heating system power up to 30 kW.

Two-pipe dead-end heating system for radiators only. No warm water floors.

The temperature difference of the radiators is 15-20 degrees.

The radiators have thermostatic (0.5 Kvs) and balancing (1.1 Kvs) valves. See Kvs in passports.

The length of the pipe from the boiler to the last radiator does not exceed 30 m.

Circulation pump wilo star 25/4 with an electric boiler with low hydraulic resistance.

With a gas wall-mounted boiler with its own pump up to 30 kW.

Explanation of the author who developed the diameter selection table

Looking through various circuits of radiator heating systems for a house of 200-300 sq.m. up to 30 kW. I realized that there is no universal approach to choosing diameters.

If you look at well-functioning circuits of heating systems and try to find features in diameters, then there is nothing particularly similar and there cannot be.

We look at the speeds, they range from 0.2 to 0.7 m/sec.

We look at the losses per meter of pipe, they also range from 20 to 250 Pa/m.

As you can see, there is nothing to grab onto. The speed and head loss ranges are too large.

On the boiler circuit from 0.7 - 1.0 m/sec. On the next distribution line from the boiler (tee, manifold) about 0.4-0.5 m/sec. This corresponds to 150 Pa/m. Of course, a forced reduction in the movement of coolant speed to 0.15 m/sec is allowed.

The radiator branch must have balancing valves up to 1.1 Kvs

You know that a 25/4 pump can charge a 30 kW radiator heating system.

If you buy a 25/6 pump, then over 10 years you will spend electricity approximately equal to 8 thousand rubles. Savings for small-diameter pipes may vary. A large diameter can pay for itself in 20 years. If you have a house of 250 sq.m. If you installed 2 25/6 pumps, then it’s clear you got something wrong with the diameters. Because you can heat a 250 sq.m. house with a 25/4 pump. m. if this applies only to the radiator heating system.

Where the branches begin, it is necessary to make a pressure loss in the pipeline of 150 Pa/m. In the boiler line, pressure losses can be neglected in favor of reducing diameters, which will not affect the uniform distribution of flow rates between the radiators. Also, a reduction in diameters leads to a significant reduction in the price of fittings on the boiler line.

In some short branches, a pressure loss of 250 Pa/m can be allowed. but in this case you need to make an accurate hydraulic calculation using a heating system simulator program

If you calculate 250 Pa/m. this may result in costs being less evenly divided between the radiators. In some cases, you may not be able to adjust the system with balancing valves. Large losses are also possible, which will lead to the selection of a more powerful pump.

Pressure loss of 150 Pa/m. predict diameters that make it possible to more evenly divide costs between radiators. Of course, with such a choice of diameters, it is necessary to install balancing valves on the radiators in order to adjust the flow rates between the radiators. It is possible to choose the diameters so as not to have to adjust the balancing valves, but in this case the diameters turn out to be very large and the heating system turns out to be expensive. The heating system simulator program will help you choose diameters to reduce the balancing setting

250 Pa/m. makes it possible to save on materials. But to save money, you need to make more accurate calculations, and this means time or money that you pay to the designer. It turns out that you can choose a large diameter, thereby saving time or money on hydraulic calculations.

If you already have a heating system installed and it is not working well, then you can test the heating system circuit in the program. Simply put, conduct an audit of the heating system in the heating system simulator program

Some plumbers or specialists say that low flow rates of the coolant in the pipes should not be allowed because the heating system may become airborne. They are partly right. But when it comes to the speed of movement, some plumbers are mistaken if they say that the speed should be at least 0.5 m/sec. I found reference books that indicate a speed of 0.2 m/sec. In order to remove air along the coolant flow. Take, for example, a warm water floor, they indicate a minimum speed of 0.15 m/sec. In a horizontal section of a warm water floor, airing does not occur at such a rate. In my experience, air was generally removed spontaneously in the air loops if there was not so much of it that there was circulation. There are cases, only at the first start-up it is not possible to start some branches due to air loops (where the pipe rises up and then falls down). Air loops cannot be made in the heating system. If you have air loops, then you will have to buy a more powerful pump in order to create pressure to expel the air from such air loops. I mean loops with a height of 250 mm up to 1.5 m.

There is one more feature: each increase in diameter leads to a doubling of power. You can look at the table and see this. In this case, the cross-sectional area of ​​the internal diameter does not double.

I warn you that there may be errors in calculating the diameter from the tables

The table for choosing diameters has some error in choosing diameters. But the task was to give people an algorithm for choosing diameters without precise hydraulic calculations. And accurate hydraulic calculations can be performed in the simulator program.

More about the program

This article was written by a specialist in the field of calculations of heating and water supply systems with more than 10 years of experience. Developed and designed more than 100 heating system schemes. The specialist also has his own software for heating calculations: Read more about the program

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You can request services for calculating diameters for your heating system here: Submit a request for calculation

A series of video tutorials on a private house
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Part 2. Construction of a water well Part 3. Laying a pipeline from the well to the house Part 4. Automatic water supply Water supply Water
supply for a private house.
Principle of operation. Connection diagram Self-priming surface pumps. Principle of operation. Connection diagram Calculation of a self-priming pump Calculation of diameters from a central water supply Water supply pumping station How to choose a pump for a well? Setting up a pressure switch Pressure switch electrical diagram Operating principle of a hydraulic accumulator Sewage slope of 1 meter SNIP Connecting a heated towel rail DHW recirculation diagram - the best solution! Heating schemes
Hydraulic calculation of a two-pipe heating system Hydraulic calculation of a two-pipe associated heating system Tichelman loop Hydraulic calculation of a single-pipe heating system Hydraulic calculation of radial distribution of a heating system Scheme with a heat pump and a solid fuel boiler - operating logic Three-way valve from Valtec + thermal head with remote sensor Why the heating radiator does not heat well in an apartment building How to connect a boiler to a boiler?
Options and connection diagrams DHW recirculation. Principle of operation and calculation You are not correctly calculating the hydraulic needle and collectors. Manual hydraulic calculation of heating. Calculation of a warm water floor and mixing units. Three-way valve with a servo drive for DHW. Calculation of DHW, BKN. We find the volume, power of the snake, warm-up time, etc. Heating temperature conditions 90-70, 80-63, 70-55, 60-50 Water supply and heating designer
Bernoulli's equation Calculation of water supply for apartment buildings
Automation
How servo drives and three-way valves work Three-way valve for redirecting the flow of coolant
Heating
Calculation of the thermal power of heating radiators Radiator section Overgrowth and deposits in pipes worsen the performance of the water supply and heating system New pumps work differently... Calculation of infiltration Calculation of temperature in an unheated room Calculation of the floor on the ground Calculation of a heat accumulator Calculation of a heat accumulator for a solid fuel boiler Calculation of a heat accumulator for storing thermal energy Where to connect the expansion tank in the heating system?
Boiler resistance Tichelman loop pipe diameter How to choose the diameter of a pipe for heating Heat transfer of a pipe Gravity heating from a polypropylene pipe Why don’t they like single-pipe heating? How to love her? Smart selection of diameters in a heating system Balancing heating radiators - a step-by-step guide Top 5 problems in designing heating systems Heat regulators
Room thermostat - operating principle
Mixing unit
What is a mixing unit?
Types of mixing units for heating Characteristics and parameters of systems
Local hydraulic resistance.
What is KMS? Bandwidth Kvs. What it is? Boiling water under pressure - what will happen? What is hysteresis in temperatures and pressures? What is infiltration? What are DN, Du and PN? Plumbers and engineers must know these parameters! Hydraulic meanings, concepts and calculation of heating system circuits. Flow coefficient in a single-pipe heating system. Hydraulic paradox in a heating system. Riddle No. 4 Video
Heating Automatic temperature control Simple replenishment of the heating system Heat engineering.
Walling. Warm water floor Combimix pump mixing unit Why choose underfloor heating? Water heated floor VALTEC. Video seminar Pipe for heated floors - what to choose? Warm water floor - theory, advantages and disadvantages Laying warm water floor - theory and rules Warm floors in a wooden house. Dry heated floor. Warm water floor cake - theory and calculation News for plumbers and engineers Plumbers Are you still doing hack work? The first results of the development of a new program with realistic three-dimensional graphics Thermal calculation program. The second result of the development of Teplo-Raschet 3D Program for thermal calculation of a house through enclosing structures Results of the development of a new program for hydraulic calculation Primary secondary rings of the heating system One pump for radiators and underfloor heating Calculation of heat loss at home - wall orientation? Regulatory documents
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Introduction and introduction.
Part 1 Hydraulic resistance of a thermostatic valve Hydraulic resistance of a filter flask Video course Calculation programs
Technotronic8 - Program for hydraulic and thermal calculations Auto-Snab 3D - Hydraulic calculation in three-dimensional space
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Hydrostatics and hydrodynamics
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Pressure loss along a straight section of a pipe How does head loss affect flow?
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Do-it-yourself water supply for a private house Autonomous water supply Scheme of autonomous water supply Scheme of automatic water supply Scheme of water supply for a private house
Privacy Policy Answers to questions Client 1 Client 1. Boiler efficiency

Marking units

When selecting heating components, the standard unit of measurement is taken into account to determine the value and marking. The basic value that indicates the dimension is defined as a whole number or an inch. It is easy to convert inches into standard millimeters from the ratio: 1 inch equals 25.4 mm.

The size of the pipe is calculated using several indicators - the possible speed of fluid flow and some pressure loss over a one-meter section of the pipeline. Calculating the diameter based on pressure drop is economically feasible and consists of determining the balance sheet value between operating and major maintenance costs.

The larger the diameter, the higher the cost indicators, and in order to pump a certain amount of water where there is a narrowed diameter, much more energy will be required to operate the electric pump.

The procedure for calculating the heating manifold and mounting sleeves

The sleeves are installed on the heating manifold after choosing the diameter of the pipes.
An apartment or private house is equipped with a heating manifold. The device provides distribution of coolant through several branches. The calculation of the collector is carried out together with the cross-section of the pipes according to the external or internal dimensions based on the principle of “three diameters” - the pipes along the route are removed from each other by 6 radii each. The diameter of the collector is also equal to this value.

The parameters of the sleeves are calculated after establishing the cross-section of the line. Elements are selected taking into account the material of the wall and reinforcement, the degree of expansion when heated. For example, the diameter of a plastic pipe is 20 mm, the sleeve is 24 mm.

Metal-plastic pipes

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

• increased strength and durability (aluminum or fiberglass base coated with plastic generally creates a highly durable 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);
• minimal 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, just familiarize yourself with installation techniques on the Internet and purchase a special soldering iron);
• low cost of pipes of any diameters and components for them.

Reliable connection of the elements is ensured by special elements - fittings. If metal-plastic pipes need to be connected to metal pipes or shut-off valves, flanges or adapters for threaded connections are used.

When installing a heating system made of pipes and fittings reinforced with glass fiber, the operation of stripping these elements is not required, which significantly speeds up and simplifies the work.

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

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Which polypropylene is better for heating, based on its type

Before purchasing polypropylene heating pipes, it is better to familiarize yourself with their technical parameters, scope of application and price-quality ratio. After all the pros and cons are taken into account, you can choose the most optimal product option. Pipe products made of polypropylene according to their design characteristics are divided into:

1. Single layer;
2. Multilayer.

Products of the first type are classified by type:

PPH.

The simplest type of polypropylene pipes for installing industrial systems, ventilation and water supply systems (cold water supply).

PPV.

They are produced on the basis of a blocksomer polymer compound used to install a system of heated floors and cold water supply. This material is better suited for the manufacture of mechanically resistant joints.

PPR.

They are made from random copolymer/polypropylene, widely used in cold water supply and various heating systems.

PPs.

A separate type of plastic product that better withstands heating of the environment up to 95 degrees.

Multilayer heating pipes include reinforced polypropylene products consisting of a durable interlayer frame.

Their main advantage is the ability to reduce temperature load changes in the pipe.

In practice, for heating devices it is better to use polypropylene pipe products reinforced with foil. There are 2 types of such products:

1. Reinforced;
2. Smooth.

The main disadvantage of reinforced heating pipelines made of polypropylene is the need to strip the foil insert before soldering, since the presence of the insert reduces the reliability of the seam in the structure. At the same time, there are types of pipes with deep insert placement, in which it is better not to strip them.

But still, taking into account all the advantages of polypropylene products for heating, there are a number of significant shortcomings regarding the process of connecting elements. When installing the structure, it is better to install pipes, which can only be done efficiently by a qualified craftsman. It should also be remembered that during the welding process, layers of pipe half the wall thickness are joined.

When choosing polypropylene products and components for them for a heating system, it is necessary to take into account the scope of application, temperature limits of the working environment and installation conditions.

There are several features that are best taken into account when choosing pipes:

• When installing polypropylene heating pipelines, you should use a special soldering iron;
• The market offers a wide variety of components made from this material (fittings, couplings, adapters, tees, 45, 90 degree angles) that are required elements;
• Connecting fittings made of white and gray polypropylene work best for installing water supply systems and heating systems.

When choosing plastic pipe products, you should familiarize yourself with the features of their characteristics and the possibility of application. Only after this will it be possible to determine which pipe is best suited for heating installation. For each type of polypropylene product, the manufacturer includes detailed instructions and a description of the intended purpose.

It is better to trust the installation of heating from polymer-based pipes only to highly qualified craftsmen with experience.

Installation of a heating system with metal-plastic pipes

Metal-plastic pipes easily change shape and are quite convenient to install. An additional advantage is that there is no need for expensive tools; they have an attractive appearance, so painting the system is not required. You can even do without special scissors (replace with a hacksaw) and a pipe bender (a spring is enough).

In order to bend metal-plastic heating pipes, various pipe benders and external or internal springs (mandrels) are used. The bending radius depends on the outer diameter of the product, but cannot exceed four diameters.

Follow installation with detachable fittings

Detachable (threaded and compression) fittings are quite expensive, but without them it is impossible to create connections between pipes and devices. If necessary, these elements can be dismantled and installed again (in compression ones, the crimp ring must be replaced).

Regardless of the fitting used, you first need to cut a piece of pipe to the desired length, calibrate the end and remove the chamfer. When cutting, maintain perpendicularity to the axis. Both the presence of a chamfer and unevenness during cutting can lead to a violation of the tightness of the connection.

If the fitting is threaded (coupling, tee, cross), then it is enough to screw the pipes to its ends. If it is compression, then it is equipped with a special nut, which should be tightened with a wrench immediately after the pipe is inserted into the fitting. Both threaded and compression ones do not require the use of special tools during installation, but they must be monitored during operation, since such connections tend to relax. They are used for open installation, as well as for connecting to manifolds, installing radiators and connecting to valves.

Sequence with press fittings

If it is necessary to monolith metal-plastic pipes for heating, installation is carried out using press fittings that cannot be disassembled and do not require maintenance during operation. In this case, you cannot do without a press tool that compresses the sleeve around the fitting.

When installing a heating system, you can use fittings made of plastic, bronze and brass.

Metal-plastic heating pipes have not only advantages, but also disadvantages:

• the “layer cake” design is weakened by repeated deformations caused by temperature fluctuations;
• the cross-section of the fitting is narrower than the cross-section of the pipes;
• high-quality fittings are very expensive;
• counterfeit materials create problems during operation of the heating system;
• metal-plastic is unstable in relation to ultraviolet rays, mechanical and thermal influences.

The cost of high-quality metal-plastic cannot be less than 90 rubles per meter. This should be taken into account when purchasing. For example, metal-plastic pipes for heating rehau with a diameter of 16 mm cost 119 rubles per meter, with a diameter of 40 mm - 959 rubles per meter.

Installation of heating and water supply systems has become significantly easier with the advent of a new building material on the market - metal-plastic pipes. They have a number of advantages: they bend easily and reliably retain their given shape, are resistant to corrosion, do not require painting, have a lower noise level of liquid flow, are light in weight, and the flow area does not narrow during the entire period of operation.

Polyethylene is inert towards aggressive environments, and metal-plastic pipes are not subject to corrosion.

Regardless of what diameters of metal-plastic pipes are used in installation, the expansion coefficient of the material is always the same.

This ensures the reliability and durability of the pipeline

It is important that these products can come into contact with any materials, including concrete. They have proven themselves well in the Russian climate and can work without insulation at a temperature of -25°C

They are sold in coils and measured in linear meters. Flexible, allowing installation without the use of special tools.

What are there and which are better?

According to their structure, polypropylene pipes come in three types:

• Single layer. The walls are completely made of polypropylene.
• Three-layer: fiberglass reinforced - fiberglass threads are sealed between two layers of polypropylene;
• reinforced with foil - the design is similar.

Now briefly about why polypropylene pipes are reinforced. The fact is that this material has a high coefficient of thermal expansion. When heated by 100°C, one meter of single-layer pipe becomes 150 mm longer. This is a lot, although no one will heat them that much, but even at lower temperature deltas the increase in length is no less impressive. To neutralize this phenomenon, compensation loops are installed, but this approach does not always save.

Types of expansion joints for polypropylene pipes

Manufacturers found another solution - they began to make multilayer pipes. They lay fiberglass or aluminum foil between two layers of pure propylene. These materials are not needed for strengthening or any other purposes, but only to reduce thermal elongation. If there is a layer of fiberglass, the thermal expansion is 4-5 times less, and with a layer of foil - 2 times. Compensation loops are still needed, but they are installed less frequently.

On the left is a fiberglass-reinforced pipe, on the right is a regular single-layer pipe

Why is reinforcement made with both fiberglass and foil? It's a matter of operating temperature range. Those with fiberglass can withstand heat up to 90°C. This is enough for hot water supply, but not always enough for heating. Polypropylene pipes reinforced with foil have a wider temperature range - they can withstand heating of the environment up to +95°C. This is already enough for most heating systems (except those with solid fuel boilers).

Which PPR pipes are suitable for which systems?

Based on everything said above, it is clear which polypropylene pipes are better for heating - those reinforced with foil, if high-temperature operation of the system is expected (from 70 ° C and above). For low-temperature heating systems, glass fiber reinforced products can be used.

Any PPR pipes are suitable for cold water supply, but the most rational solution is ordinary single-layer pipes. They cost quite a bit, and the thermal expansion in this case is not so great, one small expansion joint for the water supply in an average private house is enough, but in an apartment, with a small length of the system, they don’t make it at all, or rather they make an “L”-shaped one.

An example of a polypropylene water pipe

To install a hot water supply system, it is best to take polypropylene pipes with a fiberglass reinforcing layer. Their qualities are optimal here, but they can also be used with a foil layer

Please note that compensators are required

Which ones are easier to install?

When deciding which polypropylene pipes are better, pay attention to such a parameter as the complexity of installation. All types are connected by welding, and for turns, branches, etc.

fittings are used. The welding process itself is identical for all types, the difference is that in the presence of aluminum foil, pre-treatment is required - it is necessary to remove the foil to the soldering depth.

This is what the external reinforcement of a polypropylene pipe with foil looks like

In general, there are two types of aluminum reinforcement - external and internal. With the outer one, the foil layer is close to the outer edge (1-2 mm), with the inner one the reinforcing layer is located approximately in the middle. It turns out that it is filled with an almost identical layer of polypropylene on both sides. In this case, preparation for welding also consists of removing the outer layer of propylene to the entire depth of welding (and the foil too). Only under these conditions can the required seam strength be achieved. All this preparation takes a lot of time, but the most unpleasant thing is that if there is an error, we get a very unreliable connection. The most dangerous option is when water seeps into the foil. In this case, the polypropylene will sooner or later collapse and the connection will leak.

Foil-reinforced pipes must be welded correctly

Based on these data, we can come to the conclusion that if conditions permit, it is better to use single-layer or fiberglass-reinforced polypropylene pipes. Proponents of aluminum reinforcement say that foil further reduces the amount of air that penetrates into the system through the walls. But the foil is often made perforated and it does not necessarily go in a continuous strip, covering the entire diameter of the pipe. Often it has a longitudinal gap. After all, its task is to reduce the amount of thermal expansion, and even strips of more stable material can cope with this task.

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Boiler and circuit power

In private houses or apartments, heating of the interior is carried out by gas or electric boilers.
The calculation of the required thermal power is carried out depending on the size of the heated area. It is believed that high-quality heating of 1 m2 will require 0.1 m kW of thermal energy. Depending on climatic conditions and gentle operating conditions, this figure increases to 1.3 kW/m2. Factors affecting the power of a heating boiler:

• Type of building material for the enclosing wall structures of a house. The high thermal conductivity of the material in combination with the insufficient thickness of the external walls greatly increases heat losses and then the operation of the boiler with the highest power will be inefficient and unsatisfactory.
• Using a second circuit to heat water. If such an option is provided in advance, a more powerful heat generator is selected.
• Type of fuel. A gas boiler is considered more economical, but it can only be used in areas where there is a gas pipeline.

Water circulation in the system is ensured by a pump designed to optimize the speed of hot water and its return. At the same time, the problem of air pockets squeezed out by a constant flow of coolant is solved.

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Air heating from a gas boiler

Relatively recently, an air heating system was developed that uses a gas boiler as a heat source. Such a system is characterized by a fairly low operating temperature and low pressure.

The operating principle is as follows:

• A gas boiler produces heat and transfers it to a metal heating element;
• Heat is transferred from the metal to the air;
• The heated air is supplied by a fan into the pipes, which ensure the transfer of thermal energy to living spaces.

Arranging such heating requires considerable effort, and the system must be designed and installed at the stage of construction of the building itself. For an air system, thin-walled metal pipes or corrugated products are best suited. Pipes can be laid in walls, but you need to take into account the fact that they will make noticeable noise during operation.

Heated air can move through the system in several ways:

• Closed circulation;
• Forward flow;
• Recirculation with external make-up.

The latter scheme is more preferable. To equip it, several additional filters are required, thanks to which the room will be filled with clean air. A properly assembled system works without radiators, has an efficiency of about 90%, is quite economical and has no visual conflicts with the interior of the building.

How to calculate the cross-section of pipes for heat supply

Before you begin to determine the diameter of the pipeline, it is worth understanding in detail the very concept of “diameter”. When applied to heating pipes, it is customary to talk about several interpretations of this term:

• External diameter. A parameter required when designing a system. It is made up of the internal diameter and wall thickness.
• Inner diameter. Determines the throughput of the pipeline.
• The nominal value of the pipe bore. An indicator used for labeling plastic products.

Quite often, pipe diameters are indicated in inches. Converting them into millimeters that are more familiar to us is simple - one inch contains 25.4 mm.

Calculation of system thermal power

For small standard heating systems it is quite possible to do without complex calculations. Here it will be enough to follow a few simple rules:

• For circuits with natural circulation, the optimal pipe diameter will be 30-40 mm.
• In systems with forced circulation of coolant, pipes of a smaller diameter should be preferred. This will ensure optimal fluid flow speed and pressure.

• Q – thermal power, kW/h,
• V – volume of heated room, m3,
• ∆t – average temperature difference indoors and outdoors, ⁰С,
• K – heat loss coefficient,
• 860 – constant correction factor for converting calculated indicators into kW/h format.

All multipliers can be easily calculated with a reasonable degree of reliability. Only the determination of the K coefficient may raise some questions.

Its value depends on the level of thermal insulation of the house or room for which calculations are being made.

The numbers could be like this:

• K=3-4. A building with a minimum level of thermal insulation.
• K=2-2.9. Facade facing with brick.
• K=1-1.9. Average level of thermal insulation.
• K=0.6-0.9. High-quality insulation with modern materials.

After determining the thermal power of the heating system, you will need to use a special table to determine the diameter of the pipes.

Tables may vary depending on the type of pipe (polypropylene, steel, cast iron, copper, etc.) and even the manufacturer. It is more correct to take these tables directly from the websites of manufacturers. Most often, the table indicates the thermal power and the expected temperature delta. At the intersection of these parameters, the required pipe diameter will be indicated.

If you cannot find a table for a specific type of pipe, you can use the table of correspondence between different types of pipelines.

Here, for each pipe diameter (meaning the internal diameter), corresponding models made from other materials are described. Of course, there will be some error, but for small heating systems it is quite acceptable.

Speed ​​of fluid movement in the system

The speed of movement of the coolant through the heating system determines the uniform distribution of thermal energy across all radiators or radiators.

The diameter of the pipe, meanwhile, has a direct impact on the speed of movement of the liquid - the smaller the cross-sectional area of ​​the pipeline, the higher the speed (all other things being equal) the coolant will move through it.

When determining the diameter of the pipes, it is worth choosing the speed value so that it falls within the range:

• On the one hand, the water flow rate should not be too high. This, of course, will increase the efficiency of the system, but will invariably be accompanied by additional noise.
• On the other hand, at speeds below 0.3 m/s there will be large heat losses. In addition, low pressure will make air vents and Mayevsky taps useless, since air pockets simply will not reach these elements.
• The optimal speed value is considered to be in the range of 0.36-0.7 m/s.

Pipe material

Before determining which pipe diameter is best suited for heating a private home, it is necessary to decide what material the pipeline itself will be made of. This allows you to determine the installation method, the cost of the project and predict in advance possible heat losses. First of all, pipes are divided into metal and polymer.

Metal

• Steel (black, stainless, galvanized).

They are characterized by excellent strength and resistance to mechanical damage. Service life – at least 15 years (with anti-corrosion treatment up to 50 years).

Operating temperature - 130⁰C. The maximum pressure in the pipe is up to 30 atmospheres. Not flammable. However, they are heavy, difficult to install (special equipment and significant time costs are required), and are susceptible to corrosion. A high heat transfer coefficient increases heat loss even at the stage of transporting the coolant to the radiators. Post-installation painting is required. The internal surface is rough, which provokes the accumulation of deposits inside the system.

Stainless steel does not require painting and is not subject to corrosive processes, which significantly extends the life of the pipes themselves and the heating circuit as a whole.

• Copper.

The maximum temperature of the working environment is 250⁰C. Working pressure – 30 atmospheres or more. Service life – more than 100 years. High resistance to media freezing and corrosion.

The latter imposes restrictions on the combined use of copper with other materials (aluminum, steel, stainless steel); Copper is only compatible with brass. The smoothness of the internal walls prevents the formation of plaque and does not impair the throughput of the pipeline, which reduces hydraulic resistance and makes it possible to use pipes of smaller diameter. Plasticity, light weight and simple connection technology (soldering, fittings). The small thickness of the walls and connecting fittings eliminates hydraulic losses.

The most significant drawback is the extremely high cost; the price of copper pipes is 5-7 times higher than the price of plastic analogues. In addition, the softness of the material makes it vulnerable to mechanical particles (impurities) in the heating system, which, as a result of abrasive friction, lead to wear of the pipes from the inside. To extend the life of copper pipes, it is recommended to equip the system with special filters.

The high thermal conductivity of copper requires the installation of insulating sleeves to prevent heat loss, but it also makes it an indispensable material for underfloor heating systems.

Polymer

They can be polyethylene, polypropylene, metal-plastic. Each modification has its own technical characteristics depending on the production technology, additives used and the specific structure.

Service life – 30 years. Carrier temperature - 95⁰C (short-term - 130⁰C); Excessive heating leads to pipe deformation, reducing service life. They are characterized by insufficient resistance to freezing of the coolant, as a result of which they rupture. The smoothness of the internal coating prevents the formation of plaque, thereby improving the hydrodynamic performance of the pipeline.

The plasticity of the material allows pipes to be laid without cutting, thereby reducing the number of fittings. Plastic does not react with concrete and does not rust, which allows you to hide the heating pipe in the floor and install “warm floors”. A special advantage of plastic pipes is their good sound insulation properties.

When exposed to high temperatures, polyethylene pipes are prone to significant linear expansion, which requires the installation of additional compensation loops and attachment points.

Polypropylene analogues must contain an “anti-diffusion layer” in their structure to prevent airing of the circuit.

The pressure level in the circuit determines not only the diameter of the polymer pipes, but also the wall thickness, which varies in the range from 1.8 to 3 mm. Fitting connections simplify installation of the circuit, but increase hydraulic losses.

When deciding which diameter to choose, you should take into account the specific markings of various pipes:

• plastic and copper are marked by external section;
• steel and metal-plastic - internally;
• often the cross section is indicated in inches; to carry out the calculation they need to be converted into millimeters. 1 inch = 25.4 mm.

To determine the internal diameter of the pipe, knowing the dimensions of the external section and wall thickness, you should subtract twice the wall thickness from the external diameter.

Example of heating system calculation

As a rule, a simplified calculation is performed based on such parameters as the volume of the room, the level of its insulation, the flow rate of the coolant and the temperature difference in the inlet and outlet pipelines.

The diameter of the heating pipe with forced circulation is determined in the following sequence:

the total amount of heat that needs to be supplied to the room is determined (thermal power, kW), you can also rely on tabular data;

Thermal power value depending on the temperature difference and pump power

Having set the speed of water movement, the optimal D is determined.

Calculation of thermal power

As an example, a standard room with dimensions of 4.8x5.0x3.0m will be used. The heating circuit is with forced circulation; it is necessary to calculate the diameters of the heating pipes for distribution throughout the apartment. The basic calculation formula looks like this:

The following notations are used in the formula:

• V is the volume of the room. In the example, it is equal to 3.8∙4.0∙3.0 = 45.6m 3 ;
• Δt is the difference between the temperature outside and inside. In the example, 53ᵒС is taken;

Minimum temperatures by month for some cities

K is a special coefficient that determines the degree of insulation of the building. In general, its value ranges from 0.6-0.9 (effective thermal insulation is used, the floor and roof are insulated, at least double-glazed windows are installed) to 3-4 (buildings without thermal insulation, for example, change houses). In the example, an intermediate option is used - the apartment has standard thermal insulation (K = 1.0 - 1.9), K = 1.1 is accepted.

The total thermal power should be 45.6∙53∙1.1/860 = 3.09 kW.

You can use tabular data.

Table for calculating heat flow

Diameter determination

The diameter of the heating pipes is determined by the formula

Where notations are used:

• Δt – difference in coolant temperatures in the supply and discharge pipelines. Considering that water is supplied at a temperature of about 90-95ᵒС, and it has time to cool down to 65-70ᵒС, the temperature difference can be taken equal to 20ᵒС;
• v is the speed of water movement. It is undesirable for it to exceed 1.5 m/s, and the minimum acceptable threshold is 0.25 m/s. It is recommended to stay at an intermediate speed value of 0.8 - 1.3 m/s.

Note! An incorrect choice of pipe diameter for heating can lead to a drop in speed below the minimum threshold, which in turn will cause the formation of air locks. As a result, work efficiency will become zero.

The value of Din in the example will be √354∙(0.86∙3.09/20)/1.3 = 36.18 mm

If you pay attention to the standard sizes, for example, of a PP pipeline, you will see that there is simply no such Din. In this case, simply select the closest diameter of propylene pipes for heating

In this example, you can choose PN25 with a diameter of 33.2 mm, this will lead to a slight increase in the coolant flow rate, but it will still remain within acceptable limits.

Features of heating systems with natural circulation

Their main difference is that they do not use a circulation pump to create pressure. The liquid moves by gravity, after heating it is forced upward, then passes through the radiators, cools and returns to the boiler.

The diagram shows the principle of circulation pressure

Compared to systems with forced circulation, the diameter of pipes for heating with natural circulation must be larger. The basis of the calculation in this case is that the circulation pressure exceeds friction losses and local resistance.

Example of wiring with natural circulation

In order not to calculate the value of the circulation pressure each time, there are special tables compiled for different temperature differences. For example, if the length of the pipeline from the boiler to the radiator is 4.0 m, and the temperature difference is 20°C (70°C in the outlet and 90°C in the supply), then the circulation pressure will be 488 Pa. Based on this, the coolant speed is selected by changing D.

When performing calculations yourself, a verification calculation is also required. That is, the calculations are carried out in the reverse order, the purpose of the check is to determine whether friction losses and local resistance do not exceed the circulation pressure.

Features of calculating the cross-section of metal pipes

Heating systems made of metal pipes must take into account the coefficient of heat loss through the walls. This is especially important with a significant pipeline length, when heat loss on each linear meter can have catastrophic consequences for the final radiators.

By adding a power reserve to the power system and choosing the correct pipe diameter, it is possible to prevent significant heat leaks.

Calculation of the diameter of heating pipes

Then, when the material for the heating system is selected, it is the turn to calculate the diameter of the pipe. You can do this yourself or trust the professionals. Moreover, you need to take as a basis the following characteristics, which can help you correctly calculate the diameter of the pipeline:

• drag coefficient;
• heating system wiring system;
• amount of heat given off;
• speed mode of coolant movement;
• internal section of the pipe;
• diameter of inlet and outlet openings in the boiler system;
• calculation of coolant cooling in the radiator.

If your heating system is highly complex (many radiators) or a mixed option (warm floors and radiators), then it is advisable to use the help of specialists and entrust them with making a design calculation of the diameter of the pipeline, because it will be quite difficult to calculate everything correctly on your own.

If you perform the calculation incorrectly, you may need a lot of effort and material costs in the future to correct all the shortcomings.

Rules for calculating diameter

The following indicators are considered standard:

• calculation of coolant cooling (T), the difference can be 15-20 degrees when leaving the boiler and returning back;
• the coolant movement speed (V) cannot be more than 1.5 m/s;
• the diameter of the inlet and outlet openings of the boiler is indicated by the manufacturer;
• the resistance coefficient is indicated by the manufacturer;
• water consumption C=0.86Q/T;
• the amount of heat released (Q) is the total power of the heated floor or radiators.

The heating system is calculated in this way. The boiler inlet and outlet is the main point. The initial pipe of the heating system, even when choosing polymer pipes, is made of metal (approximately 1.5 meters from the outlet), the corresponding section is attached to the first branch of the system. Afterwards, the pipeline branches are laid out. In this case, the diameter of the pipeline depends on the length, but, as a rule, each subsequent branch is installed an order of magnitude smaller than the previous one. The calculation for connecting the cold water pipeline system is the same, only it is connected to the inlet of the boiler system.

Heating pipe slope

When organizing an autonomous water heating system, do not forget that it must be on a slight slope, which helps its proper operation. This is especially true for a heating system where the coolant naturally moves through the pipeline. How to choose the slope of heating pipes?

To preliminary calculate the angle of inclination of heating pipes, you can use a water level - a hydraulic level or a spirit level.

In systems that use forced movement of coolant using a pump, a slope is not necessary. As a rule, in these systems the pipes are laid horizontally or with a slight slope towards the outlet shut-off valves of a few millimeters. This helps to drain the coolant from the pipes during repair work or to prevent pipe rupture if the system has not been used for a very long time in the winter.

A horizontal outlet for connecting to heating radiators from vertical pipe systems with a length of more than 50 centimeters is installed with a slope of 10 millimeters in the direction of movement of the coolant. If this bend is smaller, it is not necessary to make a slope.

Calculating the heating system in an apartment or country house is quite difficult, since the result depends on various factors. They all need to be taken into account and calculated. The efficiency and even normal performance of the entire heating system will depend on the correct calculation of indicators. This is one of those basic elements that make up the entire system in general. Therefore, the determination of this parameter must be taken very seriously. And only in this case will your apartment or private house be cozy and warm in winter.

If all the questions seem incomprehensible and quite complicated to you, then you should not waste time, and, probably, energy, and immediately turn to professionals for help. Their knowledge and experience are often enough to calculate and completely install a heating system at the highest level in a short period of time, taking into account all the necessary standards and indicators. And you can enjoy the results of professional installation.

Materials and characteristics

Knowing the diameter is only half the battle, but when you come to the store, you will be faced with a variety of materials. Polypropylene pipes for heating comply with GOST R 52134–2003. They are made from three types of plastic, two of which can be used for hot water supply and heating systems:

• consisting of identical structural units. Their molecular bonds do not withstand heating and, accordingly, are not applicable for systems with high operating temperatures;
• consisting of different structural units. The heterogeneity of bonds between molecules makes them resistant to heat, while the material does not lose its natural elasticity;
• consisting of crystals. They have the most durable and temperature-resistant structure, but at the same time they lose elasticity.

The marking of polypropylene heating pipes indicates their outer diameter. Pay attention to this when you need to connect the outline of the apartment to the central riser. With an equal outer cross-section, metal and polypropylene pipes have different internal bores; for metal it is wider.

Be sure to choose reinforced products. Aluminum and fiberglass are used as reinforcement materials. It is better to give preference to the latter, since during installation there is no need to remove the reinforcement layer to the depth of the connection of the circuit with couplings and fittings. Aluminum reinforcement is carried out:

• monolithic layer;
• layer with multiple holes.

Reinforcement of polypropylene with perforated aluminum

Both aluminum and fiberglass reinforcement layers are sandwiched between two layers of plastic. Reinforcement is needed only to compensate for the increase in length of the contour when heated. There is no question of strengthening the product, since the plastic is already very durable. Non-reinforced products are not suitable because they have a too high coefficient of linear expansion, which is 0.15 mm/m. For comparison, for reinforced products it is 0.02 mm/m. Polypropylene pipes for heating have standard sizes. They are sold in lengths of four meters.

For clarity, let's carry out the calculation. Let's take one meter of circuit in which water heated to 80 degrees circulates. Multiply the temperature by the coefficient of linear expansion and get the following values:

• for reinforced products – extension by 1.6 mm;
• for non-reinforced products - extension by 12 mm.

The marking also indicates the nominal pressure. Denoted by the Latin letters PN. For example, a product marked PN16 can withstand 16 atmospheres, but this is not the maximum of its capabilities. It can withstand larger short-term increases. The nominal pressure is the indicator at which the service life of polypropylene pipes will be half a century. The calculation was performed using special programs, where the water temperature is set to 20 degrees. This is important; as the temperature increases, the service life will naturally be shorter, since when the plastic heats up, it changes its mechanical characteristics.

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 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)

1. 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.
2. 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.
3. 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)

Pressure classification

Since a certain pressure is created in the pipeline to transport the medium, polypropylene pipes have this classification. There are four categories:

• PN10. Working pressure 10 Bar (1 MPa), maximum temperature +45°C. For cold water and low pressure systems.
• PN16. Withstands pressure up to 15 Bar (1.5 MPa), temperature up to +60°C. Also for cold water, but can also be installed in high-rise buildings.
• PN20. Pressure 20 Bar (2 MPa) and heating up to +75°C. Usually these are reinforced pipes, but with a small wall thickness. Used for hot water supply.
• PN25. The most durable pipes. Working pressure 25 Bar or 2.5 MPa, long-term heating up to +95°C. These are exclusively reinforced, and with a thick wall. They are used for hot water supply with unstable pressure (in high-rise buildings) and for heating distribution.

The presence of reinforcement is visible on the cut.
To make the fiberglass visible, it is tinted. Color - any If we talk about which PPR pipes can withstand what pressure, then single-layer pipes (without reinforcement) can be used up to PN20. The difference is in the wall thickness and this can be seen in the table. The outer diameters of polypropylene pipes do not mean anything (first column). The same external dimension can be designed for different pressures. It depends on the wall thickness and the presence/absence of reinforcement. So pipe marking is mandatory. The pressure class is indicated there.

Please note that the wall thickness in the third column - PN25 - is less than in the previous ones, although the pipes are designed for higher pressure. It's not a mistake. It's just that the pipes here are only reinforced. And in the previous two categories the wall thickness and diameters of polypropylene pipes without a reinforcing layer are indicated.

Problems in choosing heating pipes

Some may find that determining the required diameter of pipes for a heating system is not at all a difficult task. It would seem, what requirements can be presented to a pipe, the only task of which is to deliver coolant to the radiators.

Meanwhile, an incorrectly selected pipe (or collector) diameter can negatively affect the operation of the entire heating system. The movement of liquid 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 nevertheless possible to determine a number of fundamental characteristics that directly depend on the diameter of the pipeline:

• Velocity of fluid propagation. Affects the optimal distribution of heat across 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 speed of propagation.
• Coolant volume. On the one hand, increasing the diameter of the pipes will help reduce losses from friction of the liquid on the inner surface of the pipeline. On the other hand, as the cross-section of the pipe increases, the total volume of coolant in the system will increase, and its heating will require more energy.
• Hydraulic losses. Occurs at the joints of pipes of various diameters. The more transitions there are in the thermal system, the more losses of this kind will result in the end.

Types of polypropylene pipes and their purpose

Today we offer a huge range of these products. Before purchasing, you should pay special attention to the type of material. It could be as follows:

• reinforced;
• whole.

Based on the technical characteristics, we can safely say that they have a fairly wide range of applications. They are often used for:

• sewerage structures;
• transportation of toxic substances;
• water supply in the building;
• installation of the ventilation system.

Their service life is long, with proper operation it is 50 years. The age of the riser does not affect the functionality and technical characteristics; they are completely preserved.

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 ​​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 processing data on a huge number of heating systems. Calculation of the coolant by pipe cross-section was developed by plumbers with practical experience in installation work, and is used for arranging small circuits 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.

Single pipe system

A similar circuit diagram is mounted from series-connected heating devices. The liquid passes through each element of the system in turn, heating them a little at a time; because of this, it reaches the outer section with a slightly lower temperature. If the last radiator in the circuit has more sections, this will not have a negative impact on the indoor temperature.

Now there are technologies that help improve the functioning of a single-pipe heating circuit, these are the presence of:

• on batteries of special regulators;
• valves for balancing the incoming liquid;
• thermostatic or ball valves.

Such equipment is used to maintain the required temperature in the room.

Separate heating is often installed; its installation is carried out according to the following schemes:

• horizontal, with a pump, it distils the coolant using the injection method, ensuring its circulation;
• vertical - liquid flows naturally in it;
• vertical, using the injection method, with natural distillation or a combined type.

A horizontal system, so that hot water flows naturally, is constructed at a slight slope. Radiators are installed at the same level. Radiators must be equipped with air bleed valves. A pump is not installed in this line, because the coolant flows naturally.

The main task of choosing heating system elements

Usually, when choosing heating pipes, the following questions most often arise: which pipes are best to choose, what material to choose, what diameter is needed and how to calculate it correctly? To get the correct answer, you first need to decide what is most preferable for you: the total cost of the entire heating system or compliance with the standards that apply to the diameter of the pipeline? First, let's decide on the material. All pipes that are used in heating systems are divided into several types:

• polymer (metal-plastic, polyethylene, polypropylene, PVC);
• metal (stainless steel, ferrous metal, brass, copper, bronze).

Even professionals will not tell you the best heating material, because each of the above has its own advantages and disadvantages. The only material that absolutely cannot be used as a heating pipeline is PVC, because it cannot withstand elevated temperatures in the heating system. Polypropylene is less susceptible to elevated temperatures, however, it is not recommended for installation in heating. That is, you need to select one of the following materials. In order to calculate the length or weight of the pipe depending on the material of manufacture, you can use a calculator.

Copper pipes

are in no way inferior to metal-plastic products

Experts say that copper is an ideal material for heating; the service life of this heating system is more than 100 years. But the disadvantages include high thermal conductivity (which is not a disadvantage when installing a heated floor system), as well as a rather high price.

What determines the dimensions of polypropylene pipes?

Polypropylene pipe blanks were designed for a specific use case. Polypropylene pipes have never been universal - they were not combined into a single range, as in the case of steel ones. At best, you can find a size chart for the recommended type of communications. Therefore, it is not enough to know the optimal dimensions of polypropylene pipes in mm for a specific liquid or gas flow.

When choosing sizes you need to consider:

• material, a type of polymer based on a polypropylene matrix;
• pressure and temperature of the working environment;
• type of environment being moved;
• method of connecting pipe blanks. As the transverse size increases, the number of technical problems increases proportionally.

There is one more nuance. The throughput and diameter of the pipeline obtained during the calculation for the project will always differ from the internal size of polypropylene pipes. The latter are produced with a certain diameter pitch. Therefore, you need to select a workpiece with the closest, most suitable transverse size. For example, select from a table.

This is necessary so that the throughput does not decrease below critical, and not to spend money on purchasing more expensive large-diameter polypropylene pipes.

Conformity between metric and inch sizes

Knowing the dimensions of a steel plumbing system, you can understand what sizes of plastic elements should be used instead of metal ones. To do this, you need to multiply the inch size by 25.4 (1 inch = 25.4 mm). This will give you the inner diameter of the plastic pipe. Then you should select the type of pipe that is closest in value. In this case, you should choose the size in the upward direction. For example, for a 3/4″ size, when converted to mm, we get 19.05 mm. From the table we see that 2 sizes are located closely: 16.6 mm and 21.2 mm. We choose a larger one, that is, a pipe with an outer diameter of 32 mm.

When going to the store, you don’t have to stock up on calipers or a ruler to select the required size of products. Just read the labeling of plastic water pipes. At first glance, the inscription looks like a meaningless collection of letters and numbers, but it is not so. The markings indicate:

• manufacturer (graphic logo);
• product type;
• nominal pressure (alphanumeric designation starting with PN);
• pipe dimensions in mm (outer Ø x wall thickness);
• operating class;
• maximum operating pressure in MPa;
• regulatory document, for example TU or GOST.

To determine the correspondence between metric and inch sizes, you can use the table:

Only the diameter is specified in inches. To indicate the lengths of sections, slopes, center distances, etc., the value in millimeters is used.