An open heating system is the simplest and most energy-independent system with natural circulation. This system is based on the laws of thermodynamics. At the outlet of the boiler, increased pressure is created, then hot water passes through pipes to an area with lower pressure, losing temperature as it passes.
Further, the cooled coolant is returned back to the heating boiler, where it is heated again. There is a natural circulation of the coolant. The system operates exclusively on water, since the use of antifreeze for heating leads to their rapid evaporation.
In an open heating system, an expansion tank is required, as the heated water expands. The expansion tank is used to receive excess water during expansion and return it to the system when it cools down, as well as to remove water in case of its excessive volume. The tank is not completely sealed, so the water evaporates as a result, it is necessary to constantly renew its level. An open heating system does not use a pump. The system is quite simple. It consists of pipes, a steel expansion tank, radiators and a boiler. Diesel engines are used gas boilers and solid fuel boilers, except for electric ones.
In an open heating system, water circulates slowly. Therefore, pipes during operation should warm up gradually to avoid damage and boiling of the coolant. This can lead to premature wear of the equipment. If heating is not used during the winter period, then the water from the system must be drained, in order to avoid pipeline freezing.
In order for the coolant to circulate at the required level, it is necessary to install the heating boiler at a lower point in the system, and install at the highest expansion tank, for example, in the attic. In winter, the expansion tank must be insulated. When installing pipelines in an open heating system, it is required to use minimal amount turns, shaped and connecting parts.
In a closed heating system, all elements of the system are sealed, there is no water evaporation. Circulation is carried out using a pump. The so-called system With forced circulation coolant includes pipes, boiler, radiators, expansion tank, circulation pump.
In a closed heating system, when the temperature rises, the expansion tank valve opens and takes away excess coolant. When the temperature drops coolant circulation pump pumps it back into the system. In this heating system, pressure is maintained within predetermined limits. Thanks to this, it is coolant deaeration function.
For stable system operation indoor heating an expansion tank made of high-strength metal is also used. This is a closed tank, consisting of two halves, rolled to each other.
Inside there is a membrane (diaphragm) made of high-strength heat-resistant rubber. Also inside there is a small gas volume(may be nitrogen that is pumped in at the manufacturing plant, or air that accumulates in the system as needed). The membrane divides the tank into parts: one part - where excess water enters when the heating system is heated, the other part contains nitrogen or air that does not come into direct contact with water. Thus, heat transfer fluid enters the expansion tank and penetrates the membrane. When the coolant cools, the gas behind the membrane begins to push it back into the system.
Differences between open and closed heating systems
There are the following distinctive features of open and closed heating systems:
- The location of the expansion tank. In an open heating system, the tank is located in highest place system, and in a closed system, the expansion tank can be installed anywhere, even next to the boiler.
- The closed heating system is isolated from atmospheric flows, which prevents air from entering. This increases service life. Due to the creation of additional pressure in the upper nodes of the system, the possibility of formation of air pockets in radiators located on top.
- Pipes are used in an open heating system with large diameter which creates inconvenience, also the installation of pipes is carried out at an angle to ensure circulation. It is not always possible to hide thick-walled pipes. To ensure all hydraulic rules it is necessary to take into account the slopes of the distribution of flows, the height of the lift, turns, narrowing, connection to radiators.
- In a closed heating system, pipes of smaller diameter are used, which makes construction cheaper.
- Also in a closed heating system it is important install the pump correctly to avoid noise.
Benefits of an open heating system
- simple maintenance of the system;
- lack of a pump ensures silent operation;
- uniform heating of the heated room;
- quick start and stop of the system;
- independence from power supply, if there is no electricity in the house, the system will be operational;
- high reliability;
- no special skills are required to install the system, first of all, a boiler is installed, the power of the boiler will depend on the area to be heated.
Disadvantages of an open heating system
- the possibility of reducing the life of the system when air enters, as heat transfer decreases, resulting in corrosion, water circulation is disturbed, and air plugs are formed;
- the air contained in an open heating system can cause cavitation, which destroys the elements of the system located in the cavitation zone, such as fittings, pipe surfaces;
- possibility of freezing coolant in the expansion tank;
- slow heating systems after switching on;
- needed constant level control coolant in the expansion tank to prevent evaporation;
- the impossibility of using antifreeze as a coolant;
- cumbersome enough;
- low efficiency.
Advantages of a closed heating system
- simple installation;
- there is no need to constantly monitor the level of the coolant;
- opportunity antifreeze applications without fear of defrosting the heating system;
- by increasing or decreasing the amount of coolant supplied to the system, it is possible to regulate the temperature in room;
- due to the lack of evaporation of water, the need to feed it from external sources is reduced;
- independent pressure regulation;
- the system is economical and technologically advanced, has more long term operation;
- possibility of connection to the closed heating system of additional sources of heating.
Disadvantages of a closed heating system
- the main disadvantage is the dependence of the system on the availability permanent power supply;
- the pump requires electricity;
- for emergency power supply, it is recommended to purchase a small generator;
- in case of violation of the tightness of the joints, air may enter the system;
- dimensions of expansion membrane tanks in enclosed spaces of a large area;
- the tank is filled with liquid by 60–30%, the smallest percentage of filling falls on large tanks, at large facilities tanks with an estimated volume of several thousand liters are used.
- there is a problem with the placement of such tanks, used special installations to maintain a certain pressure.
Everyone who is going to install a heating system chooses which system is simpler and more reliable for him.
Open heating system thanks to ease of use, high reliability, used for optimal heating small spaces. It can be small one-story country houses, and country houses.
The closed heating system is more modern and more sophisticated. It is used in multi-storey buildings and cottages.
When heating houses in the private sector, a closed heating circuit with forced circulation is mainly implemented.
The coolant in this scheme does not evaporate due to lack of contact with the environment. This makes it possible use special formulations other than water that increase heating efficiency.
Closed heating system: what is it, principle of operation, pros and cons
These schemes use expansion membrane tanks. Sealed container divided into two parts by an elastic membrane.
When the temperature rises, the valve opens and the excess liquid moves into the tank.
When the temperature drops, the coolant enters back into the system, due to which a stable pressure is maintained in the latter.
Non-pressure tank can be completely filled with liquid, so the pressure maintenance installation must be more compact than a conventional tank. It allows you to adjust the specified parameters in the circuit and automatically feed the structure.
closed circuit consists of the following elements:
- from a sealed membrane tank;
- from batteries (radiators);
- from the heating boiler;
- from circulation pump;
- from pipes;
- from connecting elements(valves, taps, filters).
Closed heating circuit has a number of advantages:
- the possibility of using any coolant;
- durability of the structure due to complete tightness;
- no extra noise
- opportunity self installation systems;
- high speed of movement of the liquid, providing maximum heat transfer;
- no need for thermal insulation for the highway;
- reducing the financial cost of heating the house.
The disadvantages include dependence electrical energy and the need to purchase a large membrane tank, the price of which is quite high. The problem of volatility is solved by installing blocks uninterruptible power supply or small generators providing emergency power.
Construction schemes, use in apartment buildings
Used in private homes one-pipe or two-pipe heating circuit.
Single pipe scheme used in rooms with a small area where heating is required no more than five radiators.
Photo 1. Scheme of a closed heating system with a single-pipe circuit. Each of the radiators is connected in series.
All batteries are included in the circuit in series, so the last heater will always be colder than the first. The obvious advantage of such a scheme is less pipe consumption.
If one battery fails, the rest will continue to operate normally. when using bypass. Single pipe system is horizontal and vertical. The horizontal one does not allow you to adjust the amount of coolant, therefore, when laying it, bypasses are installed. A vertical single-pipe circuit is in most cases used in high-rise buildings.
Two-pipe (two-circuit) scheme heats rooms more evenly. The liquid from the heat generator to the batteries circulates on two circuits. Radiators in this case are connected in parallel. The coolant has the same temperature in all batteries. This method is much more expensive, but it makes it possible to regulate the temperature in each room.
Calculation
In order to choose the right circulation pump and pipe diameters, carry out hydraulic calculation heating schemes. It allows you to identify hydraulic pressure losses in specific areas and minimize operating costs.
Attention! It is advisable to install a circulation pump in the return pipeline. In this case, the service life of the device will increase, since an already cooled coolant will pass through it.
Calculations are carried out by a specialized specialist using thermotechnical calculation and after selection of batteries. As a result of the calculations, the pressure value necessary for the circulation of water by the circulation pump will be obtained. After this stage, the value is calculated to determine the volume and selection of the membrane tank.
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How to start a coolant in the system?
When filling a closed circuit there should be no air pockets.
If heating circuit connected to the water supply with a tap, in order to fill it you need periodically open the valve and release the displaced air from radiators.
This process continues until all excess air is gone and the pressure reaches the required design value.
To fill a circuit that is not connected to the water supply pump and tank required from which the coolant will be pumped. Before applying it, you need to open all the taps on the radiators. The drain fitting is connected to the pipe, and the structure is filled with the help of a circulation pump.
Important! When filling the heating circuit with coolant it is necessary to close the taps in time to prevent leaks.
Setup and launch
After starting the coolant into the structure check all circuit connections. Before this, the air from the pump must be downloaded, otherwise the operation of the device may be disrupted. Next, you need to bypass all the batteries and do the same procedure, slightly opening Mayevsky cranes.
The air descends until water flows out of the radiators. After that, the pressure value is checked by the measuring device. If she below 1.5 atmospheres, then the liquid is added again, and the process of deaeration of the equipment is resumed.
Then the system is pressurized. The pump pumps the coolant into the pipes until the pressure increases in 1.5-2 times.
The heating structure is left in this state for 15 minutes, after which the pressure is measured again. If the readings of the measuring device have changed, it means that there is a leak somewhere.
Otherwise, the operating pressure is returned to the system by draining excess coolant.
Final step - starting the heat generator, which is already prepared for use and included in the network. A low temperature is set on the thermostat of the equipment ( 40-50°C), time is given to warm up the entire volume of the coolant. After that, all radiators are checked. If the upper parts of the batteries are colder, then the air is bled again.
After that increase the temperature of the liquid(up to 70-80 °C) and leave the heating circuit for a while. If in this mode the heat appliances continue to operate normally, and the temperature of the liquid in the return pipe at 20 °C colder than heated, the system functions properly and does not require additional settings.
Features of the heating circuit with a membrane expansion tank
The circulation pump in a closed circuit allows you to organize the structure according to any scheme, regardless of the hydraulic resistance index. Forced circulation gives the ability to use different options for organizing heating:
- sequential arrangement of radiators;
- collector circuit;
- warm floor.
Diaphragm expansion tank and circulation pump can be located together with the heat generator in the same room. This reduces the total length of the pipelines, so when organizing the heating circuit, it is not necessary to install pipes large diameters and pay attention to the angles of inclination.
Photo 2. Scheme of the structure of a membrane tank for a closed heating system. The arrows indicate parts of the structure.
Why does pressure drop?
Pressure drops can be caused by:
- malfunctions of the heat generator (heating boiler);
- coolant leaks;
- excess air;
- aluminum radiators.
Leakage may not be visually noticeable. To discover her use special tools: thermal imagers or ultrasonic devices. It is necessary to carefully check the sectional connections of the radiators, because their surface may be covered with corrosion. Rusty smudges indicate damage to the batteries.
To find a leak need to press the nipple located on top of the expansion tank. If, when pressed, water and air are released, then we can safely conclude that there is a leak.
Closed type heating with safety group
Safety block in the heating circuit is a set of devices that prevent the occurrence of emergencies. Any heating structure works at certain values pressure. Depending on the heating or cooling of the coolant, this value varies. The safety group monitors it and, if the maximum allowable value is exceeded, discharges a certain amount of liquid from the circuit.
Widespread now open system heating has a number of serious disadvantages. One of them is direct contact with the atmosphere. As a result, a coolant flows through the pipes, in which there is air. Air bubbles can gradually cause corrosion of the metal elements of the heating system, as well as cause the “noise” of the coolant. All this can be avoided by just making a closed heating system of a private house.
The main feature of such systems (and what does not have open circuit) - complete isolation from the influence environment. The closed heating system, which you can do with your own hands, includes the following elements:
- boiler;
- automatic air valve;
- thermostatic valve;
- heating radiators;
- expansion tank;
- balancing valve;
- ball valve;
- pump and filter;
- manometer;
- safety valve.
How does it work water heating closed type? If the temperature of the coolant rises, then excess liquid is squeezed into the expansion tank. When the temperature drops, the liquid returns to the system, i.e. pressure is maintained within a fairly narrow range.
For efficient circulation of the coolant, a pump is used (an open system may have natural circulation). True, there is also a minus here - in the absence of power supply, a closed system will not be able to function normally (lack of electricity for a country private house is a very urgent problem). But the advantages of using a “pump” more than compensate for the disadvantages - for both an apartment and a private house, installation of additional heating systems is possible. In particular, you can make a warm floor.
The circulation pump is installed on the return pipe ("return") in front of the heating boiler. An expansion tank is also mounted here. Such an arrangement of these important elements allows you to be uncritical about the diameter of the pipes used during installation and the observance of the slope, which open water heating must have.
As a result, less time and materials are spent on the installation of such a heating system (for example, it is no longer necessary to insulate the pipeline, since the expansion tank is installed next to the boiler). However, "abuse" similar benefits not worth it. This is especially true for the slope (it’s better to do it anyway) - if it is observed, the system will at least work in the event of a power outage, but it will still work, i.e. defrosting does not threaten her.
In the video below you can see a detailed example of the organization of closed-type heating using solid fuel and electric boilers.
The closed heating system is isolated from air penetration. However, its operation does not provide 100% tightness: air can fill the pipes, for example, when adding a coolant to the system. In this case, it will accumulate at the top points. You can get rid of it by means of a Mayevsky crane or float diverters operating on an "automatic". The air already dissolved in the water is removed using special separators installed directly in the pipeline.
Good results in terms of saving heat gives the use of a thermostat. It turns on the main consumer of electricity (pump) only when the temperature in the room drops below a predetermined limit.
How to choose a boiler for closed heating
The scheme of closed heat supply of a private house provides for the use of any type of fuel. It can be gas (the most efficient and profitable option), electricity, diesel or solid fuel.
It is necessary to pay attention to the power of the boiler. The approximate value for an insulated room with ceilings up to 3 meters high is 1 kW per 10 "squares" of a private house.
The figure above is very, very approximate. It all depends on many factors: the material from which the building is built, the quality of the insulation, the presence (absence) of a heated attic or attic. The efficiency of heating is affected by the number of windows and how well they were installed. Therefore, a competent thermal calculation is required, which a qualified engineer can do.
The heating boiler can be single-circuit, double-circuit or with a boiler. As practice shows, mostly country houses have small area and, consequently, a small need for hot water. From this point of view, the best choice would be a double-circuit boiler (its installation is simple), capable of heating about 10 liters of water to + 30C in half an hour. Boiler with storage boiler more comfortable - it constantly "has" ready-made several tens of liters of hot water - constant filling is not required.
Expansion tank for closed type heating
Most often, in the heating system of a private house, water plays the role of a coolant. As the temperature increases, the volume increases and the pressure increases. If a closed heat supply scheme is used, then the pressure can overcome a certain critical value and then the elements will be destroyed heating system.
To avoid such a development of events, the installation of a heating system for a private house involves the use of an expansion tank.
Features of the design of the tank of a closed type
Any tank of this type has two main parts: a body made of metal and an elastic membrane inside.
The scheme of its operation is quite simple - air is pumped into the upper half of the tank (in expensive modifications - inert gas), the lower part is filled with water from the pipeline.
When the coolant is heated, the pressure rises, while the membrane “bends”, condensing air or an inert gas. Safety valves are available to prevent dangerous situations. When the pipeline with water cools down, the air pressure on the membrane becomes stronger than the coolant pressure, and it fills the heating system. The expansion tank is installed next to the heating boiler. Membranes are of 2 types.
- Fixed - tightly fixed around the perimeter of the expander. Such devices can be found in the tanks of the heating system of a private house or a small enterprise.
These membranes will last a long time if you follow the recommendations for use. In the event of a rupture, it is impossible to change such a membrane - you will have to change the entire tank;
- Replaceable - they are made in the form of rubber pears, balls that must be filled with water. The installation of such a membrane is carried out on the tank flange. If a rupture occurs, then you can replace the damaged membrane with a new one with your own hands, without involving specialists.
When planning a heating scheme, it is important to first of all calculate the power of the heating boiler, take into account the number of radiators and the length of the pipeline.
Careful planning and calculation of the water heating system, and the installation carried out in accordance with the obtained data, will help you achieve productive, economical and efficient heating.
When planning the creation of a water heating system in own house, the owner is faced with a choice of several options. The list of the most important questions includes the type of system (whether it will be open or closed), and what principle the coolant will be transferred through pipes (natural circulation due to the action of gravitational forces, or forced, requiring the installation of a special pump).
Each of the schemes has its own advantages and disadvantages. But still, nowadays, more and more preference is given to a closed system with forced circulation. Such a scheme is more compact, easier and faster to install, and has a number of other operational advantages. One of the main distinctive features - This is a fully sealed expansion tank for heating of a closed type, the installation of which will be discussed in this publication.
But before you purchase an expansion tank and proceed with its installation, you need to at least get a little familiar with its device, the principle of operation, as well as which model will be optimal for a particular heating system.
IN what are the advantages of a closed heating system
Although V Lately many modern appliances and space heating systems, the principle of heat transfer through a liquid with a high heat capacity circulating through pipes - without a doubt, remains the most widespread. Water is most often used as a carrier of thermal energy, although in some circumstances other liquids with a low freezing point (antifreeze) must be used.
The heat carrier receives heat from the boiler (furnaces with water circuit) and transfers heat to heating devices (radiators, convectors, "warm floor" circuits) installed in the premises in the required quantity.
How to determine the type and number of heating radiators?
Even the most powerful boiler will not be able to create a comfortable atmosphere in the premises if the parameters of the heat exchange points do not correspond to the conditions of a particular room. As it is right - in a special publication of our portal.
But any liquid has common physical properties. First, when heated, it significantly increases in volume. And secondly, unlike gases, this is an incompressible substance, its thermal expansion must be compensated in some way, providing free volume for this. And at the same time, it is necessary to provide that, as it cools and decreases in volume, air does not enter the pipe circuits from the outside, which will create a “plug” that prevents the normal circulation of the coolant.
It is these functions that the expansion tank performs.
Still not so much in private construction, there was no special alternative - at the highest point of the system, an open expansion tank was installed, which completely coped with the tasks.
1 - heating boiler;
2 - supply riser;
3 - an open expansion tank;
4 - heating radiator;
5 - optional - circulation pump. In this case, a pumping unit with a bypass loop and a valve system is shown. If desired, or if necessary, you can switch forced circulation to natural, and vice versa.
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A closed system is completely isolated from the atmosphere. A certain pressure is maintained in it, and the thermal expansion of the liquid is compensated by the installation of a sealed tank of a special design.
The tank in the diagram is shown pos. 6, embedded in the return pipe (pos. 7).
It would seem - why "to fence the garden"? An ordinary open expansion tank, if it fully copes with its functions, is seen as simpler and inexpensive solution. It probably costs a little, and besides, with certain skills, it is easy to make it yourself - weld it from steel sheets, use an unnecessary metal container, for example, an old can, etc. Moreover, one can meet examples applications old plastic cans.
Does it make sense to spend money on a sealed expansion tank? It turns out that there is, since a closed heating system has many advantages:
- Complete tightness absolutely excludes the process of evaporation of the coolant. This opens up the possibility of using, in addition to water, special antifreezes. The measure is more than necessary if country house V winter time they do not use constantly, but "arrivals", occasionally.
- In an open heating system, the expansion tank, as already mentioned, must be mounted at the highest point. Often similar place becomes an unheated attic. And this entails additional troubles for the thermal insulation of the container, so that even in the most severe frosts the coolant in it does not freeze.
And in a closed system, an expansion tank can be installed in almost any part of it. The most appropriate place for installation is the return pipe directly in front of the boiler inlet - here the parts of the tank will be less exposed to temperature effects from the heated coolant. But this is by no means a dogma, and it can be mounted in such a way that it does not interfere and does not disharmony with its appearance with the interior of the room, if, say, the system uses a wall-mounted boiler installed in the corridor or in the kitchen.
- In an open expansion tank, the coolant is always in contact with the atmosphere. This leads to a constant saturation of the liquid with dissolved air, which is the reason for the activation of corrosion in the pipes of the circuit and in radiators, to increased gas formation during the heating process. Aluminum radiators are especially intolerant of this.
- A closed heating system with forced circulation is less inert - it warms up much faster at start-up, much more sensitive to adjustments. Completely unjustified losses in the area of the expansion tank are excluded open type.
- The temperature difference in the supply pipe and in the return pipe in the currents connected to the boiler is less than in an open system. This is important for the safety and durability of heating equipment.
- A closed circuit with forced circulation to create circuits will require tons of smaller diameter pipes - there is a gain both in material costs and in simplifying installation work.
- An open-type expansion tank must be controlled to prevent overflow during filling, and to prevent the liquid level in it from falling below a critical level during operation. Of course, all this can be solved by installing additional devices, for example, float valves, overflow pipes, etc., but these are unnecessary complications. In a closed heating system, such problems do not arise.
- And, finally, such a system is the most versatile, as it is suitable for any type of batteries, it allows you to connect floor heating circuits, convectors, thermal curtains. In addition, if desired, hot heat supply can also be arranged by installing an indirect heating boiler in the system.
Of the serious shortcomings, only one can be mentioned. This — mandatory "safety group", including instrumentation (pressure gauge, thermometer), safety valve and automatic air vent. However, it is rather no no prosperity, but a technological cost that ensures the safe operation of the heating system.
In a word, the advantages of a closed system clearly outweigh, and spending on a special hermetic expansion tank looks quite justified.
How is the expansion tank for closed-type heating arranged and how does it work?
The expansion tank device for a closed-type system is not very complicated:
Usually the whole structure is placed in a steel stamped case (item 1) cylindrical shape(there are tanks in the form of a "tablet"). For the manufacture of high-quality metal with an anti-corrosion coating is used. Outside the tank is covered with enamel. For heating, products with a red body are used. (There are tanks of blue color- but these are water accumulators for the water supply system. They are not designed for elevated temperatures, and all their parts are subject to increased sanitary and hygienic requirements).
On one side of the tank there is a threaded pipe (pos. 2) for tapping into the heating system. Sometimes fittings are included in the package to facilitate installation work.
On the opposite side there is a nipple valve (pos. 3), which serves to pre-create the necessary pressure in the air chamber.
Inside, the entire cavity of the tank is divided by a membrane (pos. 6) into two chambers. On the side of the branch pipe there is a chamber for the coolant (pos. 4), on the opposite side - air (pos. 5)
The membrane is made of an elastic material with a low diffusion index. It is given a special shape, which provides an "ordered" deformation when the pressure in the chambers changes.
The principle of operation is simple.
- IN home position, when the tank is connected to the system and filled with a coolant, a certain volume of liquid enters the water chamber through the pipe. The pressure in the chambers equalizes, and this closed system takes on a static position.
- With an increase in temperature, the volume of the coolant in the heating system expands, accompanied by an increase in pressure. Excess liquid enters the expansion tank (red arrow), and bends the membrane with its pressure (yellow arrow). At the same time, the volume of the chamber for the coolant increases, and the volume of the chamber for the air, respectively, decreases, and the air pressure in it increases.
- With a decrease in temperature and a decrease in the total volume of the coolant, the excess pressure in the air chamber contributes to the movement of the membrane back (green arrow), and the coolant moves back into the pipes of the heating system (blue arrow).
If the pressure in the heating system reaches a critical threshold, then the valve in the "safety group" should work, which will release excess fluid. Some models of expansion tanks have their own safety valve.
Different models of tanks may have own features designs. So, they are non-separable or with the possibility of replacing the membrane (a special flange is provided for this). The kit may include brackets or clamps for mounting the tank on the wall, or there may be stands - legs for placing it on the floor.
In addition, they may differ in the design of the membrane itself.
On the left is an expansion tank with a membrane - diaphragm (it has already been discussed above). As a rule, these are non-separable models. Often a balloon-type membrane is used (figure on the right), made of an elastic material. In fact, it is itself a water chamber. With increasing pressure, such a membrane is stretched, increasing in volume. It is these tanks that are equipped with a collapsible flange, which allows you to independently replace the membrane in the event of its failure. But the basic principle work does not change at all.
Video: device expansion tanks brand "Flexcon FLAMCO»
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How to calculate the required parameters of the expansion tank?
When choosing an expansion tank for a particular heating system, its working volume should be a fundamental point.
Calculation by formulas
You can find recommendations to install a tank, the volume of which is approximately 10% of the total volume of coolant circulating through the circuits of the system. However, it is possible to carry out a more accurate calculation - for this there is a special formula:
Vb =Vwith ×k / D
The symbols in the formula are:
Vb- the required working volume of the expansion tank;
Vс- the total volume of the coolant in the heating system;
k- coefficient taking into account the volumetric expansion of the coolant during heating;
D- coefficient of efficiency of the expansion tank.
Where to get the initial values? Let's go in order:
- The total volume of the system ( VWith) can be defined in several ways:
- It is possible to detect by the water meter what total volume will fit when the system is filled with water.
- The most accurate method that is used in calculating the heating system is the summation of the total volume of pipes of all circuits, the capacity of the heat exchanger of the existing boiler (it is indicated in the passport data), and the volume of all heat exchange devices in the premises - radiators, convectors, etc.
- Quite acceptable error gives the simplest way. It is based on the fact that 15 liters of coolant are required to provide 1 kW of heating power. Thus, the nominal power of the boiler is simply multiplied by 15.
2. The value of the coefficient of thermal expansion ( k) is a tabular value. It varies non-linearly depending on the heating temperature of the liquid and on the percentage of antifreeze in it. ethylene glycol additives. The values are shown in the table below. The heating value line is taken from the calculation of the planned operating temperature of the heating system. For water, the value of the percentage of ethylene glycol is taken - 0. For antifreeze - based on a specific concentration.
| Heat carrier heating temperature, °C | Glycol content, % of total volume | |||||||
|---|---|---|---|---|---|---|---|---|
| 0 | 10 | 20 | 30 | 40 | 50 | 70 | 90 | |
| 0 | 0.00013 | 0.0032 | 0.0064 | 0.0096 | 0.0128 | 0.016 | 0.0224 | 0.0288 |
| 10 | 0.00027 | 0.0034 | 0.0066 | 0.0098 | 0.013 | 0.0162 | 0.0226 | 0.029 |
| 20 | 0.00177 | 0.0048 | 0.008 | 0.0112 | 0.0144 | 0.0176 | 0.024 | 0.0304 |
| 30 | 0.00435 | 0.0074 | 0.0106 | 0.0138 | 0.017 | 0.0202 | 0.0266 | 0.033 |
| 40 | 0.0078 | 0.0109 | 0.0141 | 0.0173 | 0.0205 | 0.0237 | 0.0301 | 0.0365 |
| 50 | 0.0121 | 0.0151 | 0.0183 | 0.0215 | 0.0247 | 0.0279 | 0.0343 | 0.0407 |
| 60 | 0.0171 | 0.0201 | 0.0232 | 0.0263 | 0.0294 | 0.0325 | 0.0387 | 0.0449 |
| 70 | 0.0227 | 0.0258 | 0.0288 | 0.0318 | 0.0348 | 0.0378 | 0.0438 | 0.0498 |
| 80 | 0.029 | 0.032 | 0.0349 | 0.0378 | 0.0407 | 0.0436 | 0.0494 | 0.0552 |
| 90 | 0.0359 | 0.0389 | 0.0417 | 0.0445 | 0.0473 | 0.0501 | 0.0557 | 0.0613 |
| 100 | 0.0434 | 0.0465 | 0.0491 | 0.0517 | 0.0543 | 0.0569 | 0.0621 | 0.0729 |
3. The value of the efficiency coefficient of the expansion tank ( D) will have to be calculated using a separate formula:
D = (Qm – Qb ) / (Qm + 1 )
Qm- the maximum allowable pressure in the heating system. It will be determined by the threshold of the safety valve in the "safety group", which must be indicated in the product passport.
Qb- pre-pumping pressure of the air chamber of the expansion tank. It can also be indicated on the packaging and in the product documentation. It is possible to change it - pumping with a car pump or, conversely, bleeding through a nipple. It is usually recommended to set this pressure within 1.0 - 1.5 atmospheres.
Expansion tank volume calculator
To simplify the calculation procedure for the reader, a special calculator is placed in the article, in which the indicated dependencies are included. Enter the requested values, and after pressing the "CALCULATE" button, you will receive the required volume of the expansion tank.
This guide is intended for owners of small private houses seeking to independently organize the heating of their homes in order to save money. The most rational solution for such buildings is a closed heating system (abbreviated as ZSO), which operates with an excess pressure of the coolant. Consider its principle of operation, varieties of wiring diagrams and a do-it-yourself device.
The principle of operation of closed CO
A closed (otherwise - closed) heating system is a network of pipelines and heating devices in which the coolant is completely isolated from the atmosphere and moves forcibly - from the circulation pump. Any SSO must include the following elements:
- heating unit - gas, solid fuel or electric boiler;
- safety group consisting of a pressure gauge, safety and air valve;
- heating devices - radiators or contours of underfloor heating;
- connecting pipelines;
- a pump that pumps water or non-freezing liquid through pipes and batteries;
- coarse mesh filter (mud collector);
- closed expansion tank equipped with a membrane (rubber "pear");
- stopcocks, balancing valves.
Note. Depending on the scheme, the ZSO additionally includes modern devices control of temperature and coolant flow - radiator thermal heads, check and three-way valves, thermostats and the like.
The algorithm of operation of a closed-type system with forced circulation looks like this:
- After assembly and pressure testing, the pipeline network is filled with water until the pressure gauge shows a minimum pressure of 1 bar.
- The automatic air vent of the safety group releases air from the system during filling. He is also engaged in the removal of gases that accumulate in pipes during operation.
- The next step is to turn on the pump, start the boiler and warm up the coolant.
- As a result of heating, the pressure inside the SSS increases to 1.5-2 Bar.
- The increase in the volume of hot water is compensated by a membrane expansion tank.
- If the pressure rises above the critical point (usually 3 bar), the safety valve will release excess fluid.
- Once every 1-2 years, the system must undergo an emptying and flushing procedure.
The principle of operation of the ZSO apartment building absolutely identical - the movement of the coolant through pipes and radiators is provided by network pumps located in an industrial boiler room. There are also expansion tanks, the temperature is controlled by a mixing or elevator unit.
How a closed heating system works is explained in the video:
Positive qualities and disadvantages
The main differences between closed heat supply networks and outdated open systems with natural circulation are the lack of contact with the atmosphere and the use of transfer pumps. This gives rise to a number of advantages:
- the required pipe diameters are reduced by 2-3 times;
- the slopes of the highways are made minimal, since they serve to drain water for the purpose of flushing or repair;
- the coolant is not lost by evaporation from an open tank, respectively, you can safely fill pipelines and batteries with antifreeze;
- ZSO is more economical in terms of heating efficiency and cost of materials;
- closed heating lends itself better to regulation and automation, can operate in conjunction with solar collectors;
- forced flow of the coolant allows you to organize floor heating with pipes embedded inside the screed or in the furrows of the walls.
The gravitational (gravity-flowing) open system outperforms the ZSO in terms of energy independence - the latter is unable to operate normally without a circulation pump. Moment two: a closed network contains much less water and in case of overheating, for example, a TT boiler, there is a high probability of boiling and the formation of a vapor lock.
Reference. A wood-burning boiler saves from boiling, plus a buffer tank that absorbs excess heat.
Types of closed systems
Before buying heating equipment, pipe fittings and materials, you need to choose the preferred option of a closed water system. Master plumbers practice the installation of four main schemes:
- Single-pipe with vertical and horizontal wiring (Leningradka).
- Collector, otherwise - beam.
- Two-pipe dead-end with shoulders of the same or different lengths.
- Tichelman's loop - ring wiring with associated water movement.
Additional Information. Closed heating systems also include water heated floors. much harder to assemble radiator heating, beginners take on similar installation Not recommended.
We propose to consider each scheme separately, analyzing the pros and cons. As an example, let's take a project of a one-story private house with an area of 100 m² with an attached boiler room, whose layout is shown in the drawing. The value of the heat load for heating has already been calculated, the required amount of heat is indicated for each room.
Installation of wiring elements and connection to a heat source is approximately the same. The installation of a circulation pump is usually provided in the return line, a sump is mounted in front of it, a make-up pipe with a tap and (if you look downstream). A typical piping of a solid fuel and gas boiler is shown in the diagrams.
Expansion tank not shown in the figure 
Read more about installation and connection methods for heating units using various energy carriers in separate manuals:
Single pipe wiring
The popular horizontal scheme "Leningradka" is one ring main of increased diameter, where all heating devices are connected. Passing through the pipe, the heated coolant flow is divided at each tee and flows into the battery, as shown in the sketch below.
Having reached the branch, the flow is divided into 2 parts, about a third flows into the radiator, where it cools and returns to the main line again Having transferred heat to the room, the cooled water returns to the main, mixes with the main flow and moves to the next radiator. Accordingly, the second heater receives water cooled by 1-3 degrees, and again takes away the required amount of heat from it.
Leningrad horizontal wiring - one ring line bypasses all heating devices Result: more and more cold water. This imposes certain restrictions on a closed one-pipe system:
- The heat transfer of the third, fourth and subsequent batteries must be calculated with a margin of 10-30% by adding additional sections.
- The minimum line diameter is DN20 (internal). Outer size PPR pipes will be 32 mm, metal-plastic and cross-linked polyethylene - 26 mm.
- The section of the inlet pipes to the heaters is DN10, the outer diameter is 20 and 16 mm for PPR and PEX, respectively.
- The maximum number of heaters in one Leningradka ring is 6 pcs. If you take more, there will be problems with increasing the number of sections of the last radiators and increasing the diameter of the distribution pipe.
- The cross section of the ring pipeline does not decrease throughout its entire length.
Reference. Single-pipe wiring is vertical - with lower or upper distribution of the coolant through the risers. Similar systems are used to organize gravity flow in two-story private cottages or work under pressure in apartment buildings old building.
A closed-type single-pipe heating system will be inexpensive if it is soldered from polypropylene. In other cases, it will decently hit your pocket due to the price. main pipe and fittings (tees) large sizes. What does Leningradka look like in our one-story house shown in the drawing. 
Since the total number of heaters exceeds 6, the system is divided into 2 rings with a common return manifold. The inconvenience of installing single-pipe wiring is noticeable - you have to cross doorways. A decrease in the flow in one radiator causes a change in the water flow in the remaining batteries, so the balancing of the "Leningrad" is to coordinate the operation of all heaters.
Advantages of the beam scheme
Why collector system received such a name, it is clearly seen in the presented diagram. From the comb installed in the center of the building, individual coolant supply lines diverge to each heating device. Eyeliners are laid in the form of rays along the shortest path - under the floors.
The collector of a closed beam system is fed directly from the boiler, circulation in all circuits is provided by a single pump located in the furnace. In order to protect the branches from airing during the filling process, automatic valves - air vents are installed on the comb.
Strengths of the collector system:
- the scheme is energy efficient, since it allows you to clearly dose the amount of coolant sent to each radiator;
- the heating network is easy to fit into any interior - the supply pipes can be hidden in the floor, walls or behind a suspended (stretch) ceiling;
- hydraulic balancing of the branches is carried out using manual valves and flow meters (rotameters) installed on the manifold;
- all batteries are supplied with water of the same temperature;
- the operation of the circuit is easy to automate - the manifold control valves are equipped with servo drives that close the flow at the signal of the temperature controllers;
- ZSO of this type is suitable for cottages of any size and number of storeys - a separate collector is installed at each level of the building, distributing heat to groups of batteries.
In terms of financial investments, closed beam system not too expensive. A lot of pipes are consumed, but their diameter is minimal - 16 x 2 mm (DN10). Instead of a factory comb, it is quite allowed to use soldered from polypropylene tees or twisted from steel fittings. True, without rotameters, the adjustment of the heating network will have to be done using radiator balancing valves.
The distribution manifold is placed in the center of the building, the radiator lines are laid directly There are few cons of beam wiring, but they are worth attention:
- Concealed installation and testing of pipelines is carried out only at the stage of new construction or overhaul. Laying radiator hoses in the floors of a lived-in house or apartment is unrealistic.
- The collector is highly desirable to be located in the center of the building, as shown in the drawing one-story house. The goal is to make the leads to the batteries approximately the same length.
- In the event of a leak in a pipe embedded in a floor screed, it is quite difficult to find the defect without a thermal imager. Do not make connections in the screed, otherwise you risk running into the problem shown in the photo.
Joint leak inside concrete monolith Two-pipe options
On device autonomous heating apartments and country houses 2 types of such schemes are used:
- Dead end (another name is shoulder). Heated water is distributed to heating devices through one line, and is collected and flows back to the boiler through the second line.
- The Tichelman loop (associated wiring) is a ring two-pipe network, where the heated and cooled coolant moves in the same direction. The principle of operation is similar - batteries receive hot water from one line, and the cooled one is discharged into the second pipeline - the return line.
Note. In a closed passing system, the return line starts from the first radiator, and the supply line ends at the last one. The diagram below will help you figure it out.
What is good dead-end closed heating system of a private house:
- the number of "shoulders" - dead-end branches - is limited only by the capacity of the boiler plant, so two-pipe wiring is suitable for any building;
- pipes are laid in an open or closed way inside building structures - at the request of the homeowner;
- as in the beam scheme, equally hot water comes to all batteries;
- ZSO lends itself perfectly to regulation, automation and balancing;
- correctly laid out "shoulders" do not cross doorways;
- at the cost of materials and installation, a dead-end wiring will cost less than a single-pipe one if the assembly is carried out with metal-plastic or polyethylene pipes.
The best option battery connections - two separate branches go around the premises on both sides Designing a closed shoulder system for a country or residential building with an area of up to 200 square meters is not particularly difficult. Even if you make branches of different lengths, the circuit can be balanced by deep balancing. An example of wiring in a one-story building of 100 m² with two "shoulders" is shown above in the drawing.
Advice. When choosing the length of the branches, the heating load must be taken into account. The optimal number of batteries on each "shoulder" is from 4 to 6 pcs.
Connection of heaters with passing movement of the heat carrier Tichelman's loop is Alternative option closed two-pipe network, involving the association a large number heating appliances (over 6 pcs.) in a single ring. Take a look at the associated wiring diagram and pay attention: no matter what radiator the coolant flows through, the total length of the route will not change.
From here, an almost ideal hydraulic balance of the system arises - the resistance of all sections of the network is the same. This significant advantage of the Tichelman loop over other closed wiring also entails the main drawback - 2 highways will inevitably cross the doorway. Bypass options - under the floors and above the door jamb with the installation of automatic air vents.
Disadvantage - the ring loop passes through the opening of the front door Choosing a heating scheme for a country house
- Dead-end two-pipe.
- Collector.
- Two-pipe passing.
- Single pipe.
Hence the advice: you will not be mistaken if you choose the first option for a house up to 200 m² - a dead-end scheme, it will work in any case. Beam wiring is inferior to it in two respects - the price and the possibility of installation in rooms with a finished finish.
A single-pipe version of the heating network is perfect for small house with a square of each floor up to 70 m². The Tichelman loop is appropriate for long branches that do not cross doors, for example, heating the upper floors of a building. How to choose the right system for houses various shapes and number of storeys, look at the video:
Regarding the selection of pipe diameters and installation, we will give a few recommendations:
- If the area of \u200b\u200bthe dwelling does not exceed 200 m², it is not necessary to make calculations - use the advice of an expert on the video or take the cross section of pipelines according to the diagrams above.
- When you need to “hang” more than six radiators on a dead-end wiring branch, increase the pipe diameter by 1 standard size - instead of DN15 (20 x 2 mm), take DN20 (25 x 2.5 mm) and lay up to the fifth battery. Then lead the lines with a smaller section indicated initially (DN15).
- In a building under construction, it is better to do beam wiring and choose radiators with bottom connection. Underground highways must be insulated and protected with plastic corrugation at the intersection of the walls.
- If you don’t know how to properly solder polypropylene, then it’s better not to mess with PPR pipes. Mount heating from cross-linked polyethylene or metal-plastic on compression or press fittings.
- Do not lay pipe joints in walls or screed, so as not to have problems with leaks in the future.
