Pipes for heating with natural circulation. Scheme of heating a private house with natural circulation of the coolant. Two-pipe heating systems with top wiring

Use of heating systems with natural circulation spans many decades. Their introduction began almost simultaneously with the advent of steam heating. There are several currently relevant natural circulation heating schemes for a private house, and each of them can be successfully applied when high efficiency in the most comfortable conditions for her.

Design features

The main difference between the heating scheme by gravity is that in the circuit along which the coolant moves, there is no circulation pump forcibly pushing water.

Popular arguments that are given in favor of a gravity heating system are the following points:

complete independence from the availability of electricity in the room;
high degree inertia, at which the impact of external factors on the redistribution of heat is minimized.

It should be borne in mind that an increase in the diameter of the heating pipes in such a situation has a positive effect on the operation of the system. However, it is worth adhering to certain restrictions in size.

Operating principle

During the operation of heating with natural circulation, physical principles are used in which a warmer liquid rises, moving from the highest point along the installation slope created for it from the main pipes.

With this scheme, it is necessary to install the boiler below the level of sections with radiators.
When moving from the top point, the water moves to the sections. The branch pipes connecting the radiators to the main line must be much smaller in diameter than the main line. This scheme of heating a private house with natural circulation will be in demand with an upper type of distribution.
For the lower distribution, it will be necessary to provide some accelerating circuit. It is formed during the installation of a pipeline going up to the expansion tank installed there. After that, the window is lowered to the horizontal, from which further wiring is carried out.

Heating systems without a pump reduce efficiency in rooms with low ceilings, since it is desirable to drain the pipe with the highest point of the system line 1.5-1.6 m above the boiler, and an expansion tank must also be mounted above it.

Due to the fact that the movement in the heating is carried out without a pump, then during the time it takes to reach the distant sections of the highway, the coolant manages to give off a sufficient amount of thermal energy. This principle of operation implies work in small areas. It is believed that for highways with a circuit length of more than 30 m, the scheme with a gravity-flow heating system for a private house loses its effectiveness.

VIDEO: Calculation of heating with natural circulation

Mounting Features

Boilers with natural circulation can have two types of mains connection:

single-pipe;
two-pipe.

I have both wiring options. individual characteristics installation, but in terms of efficiency of use with a gravitational heating system, they differ slightly. It is important to observe the slope of the heating pipes during natural circulation in order to ensure uninterrupted movement and the absence of airborne areas. AT open systems the exit of gas formations is carried out naturally through the expansion tank.

When installing natural circulation heating lines with your own hands, a slope is maintained that ensures a height drop of 5-10 mm for each meter of length.

The hydrodynamic forces developed in the conditions of the system, which determine the speed of the flow, directly depend on the level of the contour rise. It is important to install radiators above the level of the boiler, and the resistance of the pipeline depends on the diameters of the lines.

When the installation of a heating system with natural circulation is carried out with numerous branches and frequent refractions, this contributes to an increase in hydraulic resistance. In addition, an unreasonably high number of built-in shutoff valves also increases this value. Minimization of such areas plus a reasonable increase in the diameter of the lines contributes to an increase in pressure in the system.

Installation of a two-pipe system

Natural circulation in the heating system can be provided in two-pipe circuits. The first pipe (supply) directs the flow of hot coolant from the boiler, and the second pipe (cold) returns the cooled water to the boiler. During installation, the following steps are carried out:

a branch is drawn up from the heat generator, which goes to the expansion tank;
installation of the barrel can be carried out both under the ceiling and at the level of the insulated attic space;
a pipeline is mounted to the bottom of the tank, which goes into the room, dropping to a level of 2/3 of the height from the ceiling;
wiring is carried out to the nearest section of radiators;
the second branch pipe of the section is mounted to the return;
the return line is mounted parallel to the supply, but the slope is provided towards the boiler.

How to determine the volume of the expansion tank

Expansion bottle volume open type is determined very simply - 10% of the total volume of the coolant circulating through the water circuit. The definition of a tenth is considered universal way calculating the volume of the expander at which it works perfectly.

Tank Volume Determination closed type is already somewhat more difficult, but it is quite possible for a non-specialist to overcome it. To calculate, you need to know the following input data:

the percentage of increase in the volume of the coolant when heated (RH) - standard 5% for water and 10% for antifreeze;
the total amount of water or antifreeze in the water circuit (VC) - if there is no such data, the entire coolant will have to be drained and measured with buckets or other devices. The task is to determine the most accurate volume;
circuit and boiler pressure (DK) - this information is reflected in the technical passport for the boiler. If it is not there, the Internet will save;
limiting pressure in the expander (DB) - also all information is reflected in the data sheet.

We apply the formula:

OV x VK x (DK + 1) / DK - DB

The resulting value is rounded up to an integer and we get the estimated volume of the expansion tank.

This value is always greater than the "by eye - 10%" method, but this is not a violation. If the volume of the expander is larger than required for the water circuit, it must be adjusted correctly.

Installation of a one-pipe system

This type of water circulation in the heating system, unlike the two-pipe scheme, does not depend on the level of the radiator sections. The expansion barrel is selected with a volume of 25-32 liters. Its filling should be 2/3 of the volume.

The location of the boiler, as well as in a single-pipe boiler, should be below the level of the radiators in order to ensure a natural outflow. A mounting slope for highways of 5-70 is provided. The radiators are fed with pipes not less than 32 mm in diameter. The preferred wiring material is polymer pipeline. For connecting to the radiator pipes, a pipe diameter of up to 20 mm is used.

If the diameters are chosen correctly, then balancing is not required. However, it is advisable to install shut-off valves on the supply/discharge of the coolant to the radiators. This will ensure the ease of dismantling the sections for maintenance or repair work.

A two-pipe system is more expensive, since you have to use a double line. For this reason, it is often small spaces with natural heating supply, it is important to use single-pipe schemes.

VIDEO: Heating scheme with natural circulation

As predicted by engineers and builders in the eighties, the natural circulation heating system is alive and well in the twenty-first century, and even warms our homes. Pump equipment significantly increases the cost of the boiler and creates dependence on the mains, so many refuse it. The gravity system is the cheapest and simplest in its design. She, of course, has her drawbacks, the main of which is the limitation on the area of the building. Due to its small inertia, it is suitable for houses up to a hundred square meters.

How does the principle of natural circulation work?

The coolant, most often it is ordinary water, moves along the circuits from the boiler to the radiators and back due to a change in its thermodynamic characteristics. When, upon heating, the density of the liquid decreases, and the volume increases, it is squeezed out by the cold flow going through their return and rises through the pipes. As the coolant is distributed by gravity along the horizontal branches, the temperature drops and it returns to the boiler. So the cycle is closed.

Scheme of a heating system with natural circulation: 1 - solid fuel boiler, 2 - main riser, 3 - distributing lines, 4 - expansion tank, 5 - water tank to replenish the expander, 6 - pipe that discharges excess coolant into the sewer (tank), 7 - heat exchangers, 8 - Ball Valves, 9 - boiler, 10 - return, 11 - return riser

If it was chosen for the house water heating with natural circulation, then all horizontal pipe sections are laid with a slope going in the direction of the fluid. This allows you to effectively deal with "" batteries. Air is lighter than water, so it rushes up the pipes, enters the expansion tank, and then, respectively, into the atmosphere.

The tank takes in water, the volume of which increases with increasing temperature, and creates a constant pressure.

What does circulation pressure depend on?

The creation of the desired circulation pressure must be calculated when designing the heating system. It depends on how the levels of the middle of the boiler and the lowest radiator differ. How more difference heights, the better the liquid moves through the system. It is also affected by the difference in the densities of hot and cooled water.

The circulation pressure in the heating system, first of all, depends on the height difference between the boiler and the lower radiator. The greater this difference (h), the greater the pressure

Heating with natural circulation is characterized by a cyclic temperature change in the heat exchangers and in the boiler, which occurs along the central axis of the devices. Hot water located at the top, cold - at the bottom. Under the influence of gravity, the cooled coolant moves down the pipes.

The circulation pressure directly depends on the installation height of the batteries. Its increase is also facilitated by the angle of inclination of the supply line directed towards the radiators, and the slope of the return line facing the boiler. This allows the coolant to more easily overcome the local resistance of the pipes.

When installing a heating system with natural circulation in a private house, the boiler is installed at the lowest point so that all radiators are higher.

In a cottage, when installing a heating system with natural circulation, the boiler is installed at the lowest point. All heat exchangers (radiators) must be above

For apartment buildings, heating schemes with natural circulation are used very rarely, since when installed in an apartment, the boiler is lowered into the "pit" - directly onto the floor slab. The floor around it is cut out, and the recess itself and the perimeter around it must be protected by fireproof materials.

Schemes of such heating systems

The scheme of the heating system, regardless of the method of circulation of the coolant, depends on several factors:

method of connecting radiators with supply risers. Here, single-pipe and two-pipe systems are distinguished;
places for laying a line supplying hot water. You need to choose between the lower and upper wiring;
line laying schemes: dead-end system or passing movement of the coolant in the lines;
the location of the risers, which can be either horizontal or vertical.

One-pipe system: how to regulate the temperature?

With parallel single-pipe wiring, the heat exchangers on the upper floors receive hot water, and the lowest ones already cooled down. Therefore, the area of the latter should be increased in order to equalize the heating of all rooms.

In the second case, the entire volume of water passes through each heat exchanger, starting from the top ones. main feature such a wiring is that the radiator on the first and basement floors receive only chilled water.

With the flow version of single-pipe wiring, it is impossible to turn off or limit the flow of coolant to a separate radiator. Blocking one of them would lead to a circulation stop in the entire system.

And if in the first case it is possible to regulate the temperature in the premises with the help of taps, then in the second case they cannot be used, as this will lead to a decrease in the supply of liquid to all subsequent heat exchangers. In addition, completely shutting off the tap would mean stopping the circulation of water in the system.

When installing a single-pipe system, it is better to dwell on the wiring, which makes it possible to adjust the water supply to each radiator. This will allow you to control the temperature in separate rooms and, of course, makes the heating system more flexible and therefore more efficient.

Since single-pipe wiring can only be upper, its installation is possible only in buildings with an attic space. This is where the supply pipe should be located. Main disadvantage is that the start of heating is possible only throughout the building at once. The system also has its advantages, of course. The main ones are simple installation and lower cost. From an aesthetic point of view, the fewer pipes, the easier it is to hide them.

How should a two-pipe system be arranged?

This version of the heating scheme assumes the presence of a supply and discharge line. A hot coolant circulates in the upper part of the system, and a cooled coolant circulates in the lower part.

A two-pipe heating system is more flexible in terms of temperature control in individual rooms. However, it requires more materials than single-pipe

A pipe extends from the boiler, connected to expansion tank. A pipe comes from the tank hotline circuit, which is then connected to the wiring. Depending on the size of the tank and the volume of water in the system, an overflow pipe may extend from the tank. Through it, excess water is drained into the sewer.

The pipes leaving the bottom of the heat exchangers are combined into a return line. Through it, the cooled coolant again enters the boiler. The return must pass through the same rooms as the supply pipeline.

Horizontal or vertical riser in the wiring?

A heating system with a vertical riser involves connecting radiators to it from different floors. Its advantage: the risk of "airing" the system is lower, the disadvantage is a higher cost.

When heat exchangers from one floor are connected to a supply pipe, this is a horizontal riser system. This option will cost homeowners a smaller amount, but will have to solve the problem of education. air locks. As a rule, it is enough to install air vents.

Pros and cons of arranging this type of heating

As for the advantages of a heating system with natural water circulation, there are several of them:

lack of difficulties during installation, start-up and operation;
thermal stability of the system. Based on the gravitational circulation of the coolant, it provides maximum heat transfer and maintains the microclimate in the premises at a given level;
economy (with proper insulation building);
quiet work. No pump - no noise and vibration;
independence from power outages. Naturally, in the case when the installed boiler can work without electricity;
long service life. With timely maintenance without overhaul the system can operate for 35 years or more.

The main disadvantage of the gravitational heating system is the restrictions on the area of the building and the radius of action. It is installed in houses, the area of \u200b\u200bwhich usually does not exceed 100 square meters. Due to the low circulation pressure, the range of the system is limited to thirty meters horizontally. A mandatory requirement is the presence of an attic in the building in which the expansion tank will be installed.

A significant drawback is the slow heating of the entire house. With a system with natural circulation, it is necessary to insulate pipes passing into unheated premises as there is a risk of water freezing.

Usually, few materials are used for such wiring, but when the local resistance of the pipeline needs to be reduced, the costs increase due to the need to use larger diameter pipes.

An important point in calculating the heating system is the choice of pipe diameter. A number of factors are taken into account, depending on the type of connection of heating elements, the required system power, boiler parameters, etc. It is necessary to start calculating the diameter of pipes for heating with natural circulation by choosing a specific method for connecting the system and its main parameters. In the course of calculations, it will already be possible to draw conclusions about the appropriateness of using one or another diameter, or to adjust the system parameters based on economic, technological, or even aesthetic considerations.

What is taken into account when calculating

Key criteria to consider:

the volume of coolant sufficient to fill the system;
heating circuit length;
rated coolant flow rate;
required productivity, kW;
circulation pressure;
resistance of pipes and fittings in the heating circuit.

There is a range of acceptable values for each parameter. In this case, the calculation should give the size of the pipe of the heating system that meets all the requirements and provides optimal parameters.

The calculations refer to the inner diameter. Already after receiving right size a suitable denomination is selected, which is commercially available, then the material is selected. The wall thickness, outer diameter and appearance depend on this.

Heating parameters used to calculate the pipe diameter

the volume of the heating circuit;
speed of movement of the coolant;
heat capacity;
pressure drop of hot and cooled coolant;
outline height.

The volume of liquid in a natural circulation system, by itself, does not play a key role. The more coolant, the more fuel is spent for heating, however, due to the increased volume, the circulation pressure increases, which contributes to an increase in the heating efficiency.

The diameter of pipes for heating with natural circulation is chosen as large as possible. Especially when there is no way to increase the overall height of the outline.

It is necessary to distribute pipes and radiators in such a way as to shorten the path from the boiler to the radiator. Too long supply lines, although they will provide more pressure in the system, however, will reduce the heating efficiency at its far points. In this case, only the height of the plot has an effect.

The fluid velocity is limited within 0.4-0.6 m/s, which will minimize the resistance in the pipes. It is desirable to maintain a transitional type of water movement in pipes between laminar (uniform) and turbulent (with eddies).

The required power is calculated by the formula:

Qt \u003d V * dt * k / 860,

where V is the volume of the room in cubic meters, dt is the temperature difference in the street and in the room, k is the heat loss coefficient for the enclosing structures of the room. This is an approximate calculation formula.

With natural circulation, the pressure of the circulation is important. Fluid moves solely under the influence of gravitational forces. Hot coolant enters pipes located above the boiler, for example under the ceiling or in the attic. In radiators, the heat is transferred to the indoor air of the room. Cold water has a greater density and is heavier than hot water, therefore it descends, creating a natural flow, flowing into the boiler, where it is heated again, forming an unbreakable cycle.

The basic formula for natural circulation pressure is:

Δpt= h*g*(ρfrom – ρpt),

where h is the height in meters, g is the acceleration of free fall, ρpt and ρot are the average density of water in the supply pipeline and in the opposite direction.

Scheme for calculating the height of the water level

The main parameter affecting the heating efficiency is the height of the water level in the system, the difference between the levels of water supply and discharge from the radiator. It is she who sets the necessary circulation pressure under the action of gravity. For a two-pipe horizontal connection, the height is calculated between the center line of the radiator and the center line of the boiler, therefore it is logical that the boiler should be located much lower. For one-story house this means the location of the boiler in basement.

The height with vertical distribution indicates the difference between the levels of the inlet line and the return line, provided that the boiler is exactly at the level of the outlet line or slightly lower. However, it is often technically impossible to distribute the boiler and radiators at a sufficient height difference, therefore, the resistance of the circuit should be reduced, including increasing the diameter of the pipes.

Sometimes it is enough to install an accelerating collector, an “L”-shaped section of pipes, which additionally increases the height of the heating circuit. It should be formed directly from the boiler up and from the top point along a gentle path to the first radiator in the circuit.

Calculation of resistance selection of the optimal pipe diameter

Having all the above data on hand, the selection of the section begins, often not in one go. After marking the gasket in accordance with the connection diagram, it is taken conditional size in cross section, for example 1 inch. After that, the resistance of the system is calculated and compared with the pressure created by gravity at the nominal value of heating the coolant and the temperature of the cooled return.

If there is not enough pressure, then the cross section increases, and the calculations are repeated.
If the water velocity is too low or the volume of the coolant is too large, then the cross section is reduced and the calculation is repeated again.

Pipeline resistance is more easily expressed as head loss in meters of water column. A simple formula is used:

H = λ(Lk/Dt)(V2/2g),

where H is the nominal height equal to the resistance of the loop, λ is the roughness coefficient, Lк is the length of the loop, Dt is the inner diameter of the channel, V is the velocity of the fluid, g is the free fall acceleration.

Everything is in the formula. key parameters, such as flow velocity, pipe diameters in the heating system and their length. The difficulty arises with the coefficient λ (hydraulic friction), which is easiest to find out from the reference data for the type of pipe that is chosen as the main one during the design. Otherwise, a voluminous and complex calculation method will be required using the Reynolds number, the formulas of Blasius and Konakov, Altshul and Nikuradze.

The task is to ensure that during natural circulation the resistance of the circuit is less than or equal to the head, created by the difference levels.

To determine which pipe size to choose for heating with natural circulation, you need to take the longest circuit from the boiler to the farthest radiator and compare the calculated pressure loss, provided that the pressure is also the smallest. This means that when distributing routes in heating with natural circulation, all supply lines are located with a slight obligatory slope from the place closest to the boiler and to the far supply of the last radiator. It is a slope of approximately 1 cm per meter or at least 0.5%.

Having received the results

In the course of calculations, it is determined optimal size pipes. However, it should be borne in mind that the final design should be carried out by professionals and using much more complex formulas and schemes. The number of elbows, the connection method, cost optimization, economic feasibility and even aesthetic appearance are also taken into account. When choosing a diameter, the division of pipes into main and supply pipes, the presence of shut-off valves and control devices are taken into account, with the help of which heating is adjusted in individual rooms.

Did you manage to independently select the diameter of the pipe for heating? Alternatively, you can try to recalculate the parameters of your existing heating and determine its effectiveness. It may be worth reconsidering some points to achieve better performance, especially in savings. Leave your results, as well as your opinion on this instruction, in the comments below the article.

A common mistake in old natural circulation heating systems is related to piping. The knees were formed too angular and with a narrowing of the section, which leads to a significant increase in hydrodynamic resistance. To reduce resistance, it is necessary to maintain the correct turning radius (for steel pipes it is 2-2.5D) and use a pipe bender to keep the profile of the pipes.

Heating systems (CO) of private houses are carried out according to two main schemes of work: heating a one-story house with natural circulation (EC) and forced circulation (PC) of the coolant.
Despite the fact that the second one is more efficient, the EC system is still quite often used in private housing construction, especially in small one-story houses.

Speaking of how it works this system, without use technical terms, it looks like this.

AT heating boiler a certain volume of water is heated, as a result of which it increases in volume, its density decreases. Due to this, coming from below cold water pushes it into upper part heating system. From here, water begins to move by gravity along the CO, gradually cooling down and giving off heat to radiators and heating pipes. After completing a full circle, it returns to the bottom of the cauldron. Then this cycle is repeated.

The heating system with natural circulation of a one-story house has functional features that are often used to back up the operation of the system with the HRC. The pump installed in it operates normally, and in the event of a power failure, the system switches to operation according to the option with the EC.

General information.

The fact that the heating circuit of a one-story house with natural circulation has practically no moving elements allows it to be operated without major repairs. long time. If the distribution of CO is carried out using galvanized or polymer pipes, then the terms can reach fifty years.

The EC automatically assumes a low inlet and outlet pressure drop. Naturally, the coolant experiences a certain resistance to its movement, passing through heating devices and pipes. With this in mind, the optimal radius for the normal operation of the CO with the EC was determined, thirty meters. But we must understand that the figure is rather conditional and may fluctuate.

Due to the design features, the heating system with natural circulation of a one-story house has a high inertia. From the moment the boiler is ignited until the temperature in the premises of the building stabilizes, at least several hours pass. The reason is simple. First, the boiler heat exchanger warms up and only then does the slow movement of the coolant begin.

It is important that in those places where the CO pipes are laid horizontally, they have a mandatory slope in the direction of the coolant flow. This achieves the movement of water in the system without stagnation and the automatic removal of air from the system to its highest point, which is located in the expansion tank. It is performed in one of three options: open, with built-in air vent or sealed.

Wiring diagrams

Water heating of a one-story house with natural circulation can be performed according to several different schemes.

Work, regardless of the chosen scheme, begins with the creation of a heating plan for a one-story house with natural circulation.

The mentioned scheme provides for the laying of two pipelines along the perimeter of the structure. Used when sufficient heating is required large areas. The upper one is used to supply hot water to the CO, the lower one is used to return the cooled coolant to the boiler. Radiators are mounted between them. If possible, the boiler is mounted below the latter. Pipes are laid in compliance with the slope of the water flow of at least 5 degrees.

Fillings, especially in places where several radiators are fed at once, must be carried out using a pipe with a diameter of ≥ 32 mm. Best suited metal-plastic, or polymer pipe. The connection directly to each radiator should be made with a pipe with a diameter of 20 mm.

If the pipe diameters are chosen correctly, such a CO does not need balancing. Despite this, chokes should be installed on the connections to the radiators.

Heating a one-story house with natural circulation, made according to a two-pipe scheme, is the most an expensive option in terms of its execution (materials, work), therefore it is used quite rarely.

The simplest system that allows you to provide heating for a one-story private house with your own hands, made according to the indicated scheme, is Leningradka.
Installation conditions (inclination angle and pipe diameters) are similar to the previous version.

The specificity lies in the fact that the radiators, in this case, cut into the main heating ring (parallel to the main pipe).

In addition to the expansion tank, air bleed valves, in without fail, are placed on each of the radiators. On the radiators closest to the boiler, and on the radiators farthest from it, thermal heads or chokes are placed, which helps to equalize the temperature in them.

When choosing this option, the scheme for heating a one-story house with natural circulation is as follows.

On the sections of the pipe that supply hot water to the CO and return cold water to the boiler, special collectors are installed, which are combs, on each outlet of which a throttle is installed. Two pipes go to each of the radiators, one from the supply and one from the return.

This version, from the point of view of the possibilities for making adjustments, is the most convenient. But its installation is quite complicated, there are too many pipes, which, in order to save acceptable design premises, will have to be cleaned into the floors or behind false walls, which automatically leads to a significant increase in the cost of work and purchased materials. It is easy to make sure of this, just look at the pre-compiled heating plan for a one-story house with natural circulation.

Advantages and disadvantages

The main advantages of CO, which use natural circulation for operation, are ease of installation and long service life.

However, there are no pros without cons. The main disadvantages of these COs include:

Short working distance (radius). Acceptable characteristics are only achieved when the length of the pipelines ≤ 30 running meters.
It is not technically possible to regulate the temperature in each of the rooms of the house separately.
Water circulates in the CO under slight pressure, which results in different temperatures in different rooms(the lower, the farther from the boiler).
A long period of time that is required for the system to enter the operating mode and completely warm up all the premises of the house.

Modern homeowners often choose to operate through natural circulation. Modern pumps are expensive and gravity is cheap driving force, due to which the natural occurs and the water moves through the pipeline. Gravity flow circuits are used where there is no electricity to power the pump. Sometimes the pump is still present, and when it occurs emergency and disconnection under the influence of gravity. That is, even when electrical equipment does not work, the natural circulation heating continues to function.

This version of the heating system is perfect for cottages, the area of \u200b\u200bwhich does not exceed 100 sq.m.

The disadvantage of the design is the inability to use it in rooms with a large quadrature. But for cottages with an area of less than a hundred square meters. m, this option is perfect. For this reason, many homeowners decide to make heating with natural circulation without the involvement of outside help.

The principle of operation of a gravity heating system

The principle of operation of heating looks simple: water moves through the pipeline, driven by hydrostatic pressure, which appeared due to the different masses of heated and cooled water. Another such design is called gravity or gravity. Circulation is the movement of liquid that has cooled down in batteries and has grown heavier under pressure. own weight down to the heating element, and expelling the light heated water into the supply pipe. The system functions when the natural circulation boiler is located below the radiators.

Natural circulation is possible in closed system heating, if it is equipped with an expansion tank with a membrane. Sometimes open-type structures are converted into closed ones. Closed circuits are more stable in operation, the coolant does not evaporate in them, but they are also independent of electricity.
What influences

The circulation of water in the boiler depends on the difference in density between the hot and cold liquids and on the magnitude of the height difference between the boiler and the lowest radiator. These parameters are calculated before the start. Natural circulation occurs because return temperature in . The coolant has time to cool down, moving through the radiators, it becomes heavier and with its mass pushes the heated liquid out of the boiler, forcing it to move through the pipes.

Scheme of water circulation in the boiler

The height of the battery level above the boiler increases the pressure, helping the water to overcome the resistance of the pipes more easily. The higher the radiators are located in relation to the boiler, the greater the height of the cooled return column and with the greater pressure it pushes the heated water up when it reaches the boiler.

The density also regulates the pressure: the more the water warms up, the less its density becomes in comparison with the return. As a result, it is pushed out with more force and the pressure increases. For this reason, gravity heating structures are considered self-regulating, because if you change the temperature of the water heating, the pressure on the coolant will also change, which means that its consumption will change.

During installation, the boiler should be placed at the very bottom, below all other elements, in order to ensure sufficient pressure of the coolant.

Scheme of installation of gravity heating systems

Since the circulation of water in the heating system occurs without the participation of a pump, for the unhindered flow of fluid through the lines, they must have a diameter larger than in the scheme where water circulation is forced. The gravity system functions by reducing the resistance that water has to overcome: the farther the pipe from the boiler, the wider it is.

Water heating with natural circulation can have an upper or lower wiring. When the wiring is designed as two-pipe, heated water enters directly into each battery, and does not pass through them one by one, as in a single-pipe scheme.

Upper wiring, in which the coolant first rises to the ceiling, and from there it descends to the batteries, the best way suitable for mounting such a structure. If the wiring, then an accelerating circuit is being built: a height difference, at which water from the boiler first goes up, where in top point the pipeline enters the expansion tank, and then descends to the heating radiators.

The higher is heating device, the higher the pressure inside the pipeline. Therefore, the batteries of the upper floors often warm up better than those on the lower ones. Accordingly, if the natural circulation is two-pipe, the batteries placed at the same level with the boiler or below do not warm up enough.

To avoid such a situation, the boiler room is thoroughly buried, providing enough high pressure for the passage of the coolant through the pipes at the required speed. The boiler is placed in the basement, approximately 3 meters below the center of the lowest heating element. Pipes with hot water, on the contrary, they raise it as high as possible, placing an expansion tank at the highest point of the structure, and then the water from the supply pipe descends to the radiators.

Single-pipe system for the house: calculation of pipe diameter

One-pipe heating system is popular because it is very simple

To distinctive features, which a single-pipe heating system with natural circulation possesses, can be attributed to:

Absence of a return line: the cooled return flows back to a heating element through the same pipe.
Radiators of the lower floors warm up worse, because. the water coming down has already been cooled in the radiators above. Therefore, the further the battery is from the boiler, the large quantity sections, it must have to ensure uniform heating of all rooms.
Water circulates through pipes driven by temperature differences. A tap can be installed on each radiator, which will vary the amount of incoming water, sending the rest to other radiators and regulating the heating of the room.
If water flows sequentially from one radiator to another, cooling along the way, you should not place shut-off valves on the radiators, because. this can lead to a slowdown in the movement of the coolant through the pipes.

Natural circulation heating systems with serial connection radiators are mounted using the top wiring. Accordingly, a single-circuit scheme can only be used in a house with an attic, where the supply line will be located. Despite this, such a heating scheme with natural circulation is popular, because. it is easy to mount it, and less pipes are required than for a two-pipe one.

How to regulate the temperature in a forced closed heating water supply system

To control the microclimate in the room, closing sections can be placed on the radiators. The heated coolant, reaching the radiator, will be divided into two streams. One passes through the radiator, heating the room, and the second flows through the bypass pipe, which directs part of the coolant flow past the radiator further in the direction of travel. When adding bypass circuits to the heating circuit, it should be remembered that they should not be of the same diameter as the supply pipe, otherwise the radiator will not receive enough water for heating. Usually, the diameter of the bypass section is made one size smaller than the diameter of the supply pipe to avoid this problem. A valve is placed between the bypass circuit and the radiator inlet, which regulates the flow of water into the battery, thereby changing temperature regime. A single-pipe natural circulation heating system can heat your home without problems.

In addition to the manual valve, radiator thermostats can be used to control the temperature. With their help, the desired temperature in the room is set, and the thermostat maintains it independently, without outside interference, weakening or increasing the flow of the coolant. Temperature controllers come with built-in and remote sensors. The former are located directly on the heating battery, and remote or, as they are also called, remote ones are placed outside heater and are connected to it by means of a capillary. Plus remote sensors– accurate measurement room temperature, while built-in ones can give false readings under the influence external factors: location of the battery in a niche, the influence of the temperature of the battery itself, decorative elements covering the radiator.

How to design a sloped two-pipe system in a private one-story house with polypropylene pipes

In a two-pipe scheme, there is a supply and return line. Hot water enters the radiators from the upper pipeline, and then, after cooling, flows into the boiler through the lower one. The expansion tank is mounted immediately after the boiler, it is connected to the circuit by a vertical pipe. Install it in such a way that it is at the highest point of the structure. Everyone heating element system is connected to the return pipeline, through which the cold coolant enters the boiler.
Pros and cons of the type

Heating by gravity with a vertical riser means heating a building with several floors. This option is more expensive, but protected from the formation of air congestion.

Horizontal riser - economical option, but when moving, the coolant is mixed with air. This nuance is easy to eliminate: when installing heating with natural circulation with your own hands, you need to add air vents to the system.

Benefits of a natural circulation heating system

Advantages of natural circulation:

Ease of installation and use
High thermal stability of the circuit
No noise during operation (because there is no loud running pump)
Economical energy consumption (with proper insulation of pipes and buildings)
Autonomy: the system can easily work without electricity
Durability and wear resistance: with proper care, the gravity heating system of a private house can work without requiring repair for 30 years.

Cons of single-pipe natural circulation with a pump

Weaknesses of the gravitational heating scheme:

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The area of the building, which is heated by a one- or two-pipe heating system with natural circulation, should not exceed 100 sq.m.
The length of the contour in the horizontal plane is within 30 m (otherwise there will not be enough pressure)
It is impossible to install heating of a one-story house with natural circulation in a building without an attic, because. an expansion tank is located in the attic.
There is a high probability of water freezing, due to which pipes outside the living quarters have to be carefully insulated.

The natural circulation heating system is simple and very reliable.

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