Expansion tank of the heating system: design, calculation and selection of the best option. Expansion tank for heating systems What tank is needed for heating

The heating system of private houses, in addition to the boiler itself and the heating circuit, includes several auxiliary elements.

These include the expansion tank.

This important element of the system is a necessary device that increases reliability.

The purpose of the device lies in its name.

The heating circuit is designed for a certain pressure. But the heated coolant increases in volume and therefore exerts greater pressure. It's in the end may lead to leaks in weak spots.
The element must provide compensation for the increase in pressure, which accumulates part of the liquid.

Types of expansion tanks

Depending on what type of heating system the tanks are used in, they are divided into 2 types.

Open type

Such a tank used for open heating
without the use of forced circulation. He is container without top. There is a hole at the bottom of the tank; a heating pipeline is connected to it using a thread.

In some houses you can still find a container; it copes with its function, but is quite outdated and has a number of disadvantages:

the need to place the tank at a height;
evaporation of liquid from the container;
acceleration of corrosion processes in different parts of the heating system due to contact of the coolant with air;
large tank sizes.

Due to these disadvantages, closed expansion tanks are now becoming increasingly popular.

Closed type or membrane

The following tanks are used for heating systems with forced circulation. Capacity
compensates for pressure surges not only when heating the coolant, but also when the circulation pump is turned on.

It is also called membrane type tank due to the peculiarities of the internal structure. This a spherical or flat tank, which inside is divided into two cavities by a rubber membrane:

one is filled with coolant through a threaded pipe;
the other - with inert gas or air.

The second container has a nipple that regulates gas pressure. The compartments do not connect to each other.

The principle of operation of a closed tank is simple:

excess hot coolant enters one of the chambers, the volume of which increases;
the pressure in the gas compartment increases, which makes it possible to compensate for the voltage in the heating system.

When the coolant cools down, the process in the tank follows the reverse path.

There are 2 types of closed containers depending on the membrane:

In some the membrane is made in the form of a diaphragm that cannot be replaced. Such containers are cheaper.
In the second type of closed devices the membrane is removable and has the shape of a pear.

The choice depends on the capabilities of the buyer. It should be taken into account that damage to this rubber element occurs quite rarely.

Before purchasing a tank, you need to decide on its volume.

Volume calculation

You can calculate the volume of the tank yourself using several online calculators, or by a fairly simple formula:

V tank =(V system * k)/(1-P min /P max), Where

V tank– volume of the tank;

V syst– the total volume of the heating system, including everything, boiler, etc.;

k– coefficient of expansion of the liquid; for water its values, depending on heating from 10 o to the maximum temperature of the coolant, are indicated in the table below;

P min– initial pressure in the container;

P max– the maximum possible pressure in the tank, which is calculated from the settings of the safety valve, taking into account the difference in the heights of the insertion of the tank and the valve.

Table. The coefficient of expansion of water depending on heating at an initial temperature of 10 O WITH.

Temperature from 10	k value, %
Up to 40	0,8
Up to 50	1,2
Up to 60	1,7
Up to 70	2,3
Up to 80	2,9
Up to 90	3,6
Up to 100	4,3
Up to 110	5,2

Since the quality of operation of the entire heating system depends on the correctness of the calculations, you should not spare money and contact a special organization that will take into account all the parameters, which will allow you to purchase the most suitable tank.
Here you can be given advice on choosing and installing a tank.

When purchasing and installing an expander, there are several nuances to consider.

When choosing a place to install the tank, it is necessary to take into account that it cannot be installed directly behind the circulation pump.
Commercially available tanks come in two colors: red and blue. In the first, the membrane is stronger, but made of technical rubber. Blue tanks are used for water supply; they contain food-grade rubber, but it is less strong and durable.
During installation you must use special sealant.
If you decide to stop at open system, then the tank must be placed at the highest point, and when installing the pipeline, the recommended slope must be observed.
The size of the tank should not be less than the calculated value; a slightly larger volume is allowed. When using forced circulation, the capacity cannot be less than 15 l.
Antifreeze can act as a coolant. For glycol mixture, it is better to choose an expansion tank, the volume of which is twice as large as the calculated one.

The main advice is to contact professionals, because installing a tank only seems simple. In addition, you cannot do without a special tool.

Installation

Installation diagram of a tank in a private house system

If you are confident in the calculations and your own abilities, the tank and all materials have been purchased, then you can install the container yourself.

Tools you will need:

Step and adjustable wrenches;
Soldering device for plastic pipes;
Key for installation of plastic pipes;
In some cases it is necessary welding machine and angle grinder.

Before installation, you need to turn off the power to the boiler, turn off the valves and drain the coolant if it is already in the pipes.

The installation is carried out taking into account certain rules.

The tank must be mounted and installed so that it can be accessed easy access for adjustment and maintenance.
The room temperature should not be below 0.
A pre-shut-off valve must be installed on the supply pipe, which will allow the expander to be removed for maintenance and repair.

After installing the tank, you need to start the entire heating system. If boiling is detected in it, then the reason lies in the incorrectly selected pipe diameter. It's not about the tank.
The installation of the expansion tank is described in the following video:

Prices for tanks for heating systems

The cost is determined by its type and volume. Small closed containers (18-24 l) cost about 1000-1200 rubles.
An expander with a volume of 100 liters can be purchased for 4-6 thousand rubles. Most of the price differences between manufacturers are small.

Installation by a professional will cost you about 2,000 rubles.

By contacting trusted companies or installing it yourself and following all the rules, you will protect the heating of your home from damage. Therefore, installing a container is necessary, and you should choose closed containers.

Over the past few years, closed heating systems have become increasingly popular. Heating equipment is becoming more and more expensive, and you want it to last longer. In closed systems, the possibility of free oxygen getting inside is practically eliminated, which extends the life of the equipment.

Closed heating system - what is it?

As you know, any heating system in a private home has an expansion tank. This is a container that contains some coolant removal. This tank is necessary to compensate for thermal expansion under various operating conditions. By design, expansion tanks are of open and closed type, respectively, and heating systems are called open and closed.

In recent years, a closed heating scheme has become increasingly popular. Firstly, it is automated and works without human intervention for a long time. Secondly, it can use any type of coolant, including antifreeze (it evaporates from open tanks). Thirdly, the pressure is maintained constant, which allows the use of any household appliances in a private home. There are several more advantages that relate to wiring and operation:

There is no direct contact of the coolant with air, therefore, there is no (or almost no) unbound oxygen, which is a powerful oxidizing agent. This means that the heating elements will not oxidize, which will increase their service life.
A closed-type expansion tank is placed anywhere, usually close to the boiler (wall-mounted gas boilers come immediately with expansion tanks). An open-type tank should be located in the attic, and this means additional pipes, as well as insulation measures so that heat does not “leak” through the roof.
The closed type system has automatic air vents, so there is no airing.

In general, a closed heating system is considered more convenient. Its main drawback is its energy dependence. The movement of the coolant is ensured by a circulation pump (forced circulation), and it does not work without electricity. It is possible to organize natural circulation in closed systems, but it is difficult - it requires regulating the flow using the thickness of the pipes. This is a rather complicated calculation, which is why it is often believed that a closed heating system only works with a pump.

To reduce energy dependence and increase heating reliability, install uninterruptible power supplies with batteries and/or small generators that will provide emergency power supply.

Components and their purpose

In general, a closed heating system consists of a certain set of elements:

Boiler with safety group. There are two options here. The first is that the safety group is built into the boiler (gas wall-mounted boilers, pellet boilers and some solid fuel gas generators). The second is that there is no safety group in the boiler, then it is installed at the outlet in the supply pipeline.
Pipes, radiators, convectors.
Circulation pump. Ensures the movement of coolant. It is installed mainly on the return pipeline (the temperature is lower here and there are fewer possibilities of overheating).
Expansion tank. Compensates for changes in coolant volume, maintaining stable pressure.

Now in more detail about each element.

Boiler - which one to choose

Since the closed heating system of a private house can operate autonomously, it makes sense to install a heating boiler with automation. In this case, having configured the parameters, you do not need to return to this. All modes are supported without human intervention.

The most convenient gas boilers in this regard. They have the ability to connect a room thermostat. The temperature set on it is maintained with an accuracy of one degree. It dropped by a degree, the boiler turned on, heating the house. As soon as the thermostat is activated (the temperature is reached), the operation stops. Comfortable, convenient, economical.

Some models have the ability to connect weather-dependent automation - these are external sensors. Based on their readings, the boiler adjusts the power of the burners. Gas boilers in closed heating systems are good equipment that can provide comfort. The only pity is that gas is not available everywhere.

Electric boilers can provide a no less degree of automation. In addition to traditional units, induction and electrode units have recently appeared on heating elements. They are distinguished by their compact size and low inertia. Many believe that they are more economical than boilers using heating elements. But even this type of heating unit cannot be used everywhere, since power outages in winter are a common occurrence in many regions of our country. And provide the boiler with electricity. 8-12 kW from the generator is a very difficult matter.

Solid or liquid fuel boilers are more versatile and independent in this regard. An important point: to install a liquid fuel boiler, a separate room is required - this is a requirement of the fire service. Solid fuel boilers can be installed in the house, but this is inconvenient, since a lot of debris falls from the fuel during combustion.

Modern solid fuel boilers, although they remain periodic equipment (they warm up during combustion and cool down when the fuel burns out), but they also have automation that allows you to maintain a given temperature in the system, regulating the intensity of combustion. Although the degree of automation is not as high as that of gas or electric boilers, it is there.

Pellet boilers are not very common in our country. In fact, this is also solid fuel, but boilers of this type operate in continuous mode. Pellets are automatically fed into the firebox (until the stock in the burner is finished). If the fuel quality is good, ash cleaning is required once every few weeks, and all operating parameters are controlled automatically. The only thing holding back the spread of this equipment is its high price: the manufacturers are mainly European, and their prices are corresponding.

A little about calculating boiler power for closed-type heating systems. It is determined according to the general principle: per 10 sq. meters of area with normal insulation take 1 kW of boiler power. It’s just not recommended to take it “back to back”. First, there are unusually cold periods during which you may not have enough rated power. Secondly, working at the power limit leads to rapid wear of the equipment. Therefore, it is advisable to take the boiler power for the system with a margin of 30-50%.

Security group

A safety group is placed on the supply pipeline at the outlet of the boiler. She must control its operation and system parameters. Consists of a pressure gauge, automatic air vent and safety valve.

The pressure gauge makes it possible to control the pressure in the system. According to recommendations, it should be in the range of 1.5-3 Bar (in one-story houses it is 1.5-2 Bar, in two-story houses it is up to 3 Bar). If you deviate from these parameters, appropriate measures must be taken. If the pressure drops below normal, you need to check if there are any leaks, and then add some coolant to the system. At increased pressure, everything is somewhat more complicated: it is necessary to check in what mode the boiler is operating, whether it has overheated the coolant. The operation of the circulation pump, the correct operation of the pressure gauge and the safety valve are also checked. It is he who must discharge excess coolant when the threshold pressure value is exceeded. A pipe/hose is connected to the free branch pipe of the safety valve, which is discharged into the sewer or drainage system. Here it is better to do it in such a way that it is possible to control whether the valve works - if water is discharged frequently, you need to look for the reasons and eliminate them.

The third element of the group is an automatic air vent. Air trapped in the system is removed through it. A very convenient device that allows you to get rid of the problem of air locks in the system.

Security groups are sold assembled (pictured above), or you can buy all the devices separately and connect them using the same pipes that were used to wire the system.

Expansion tank for closed heating system

The expansion tank is designed to compensate for changes in coolant volume depending on temperature. In closed heating systems, this is a sealed container divided into two parts by an elastic membrane. At the top there is air or inert gas (in expensive models). While the coolant temperature is low, the tank remains empty, the membrane is straightened (picture on the right).

When heated, the coolant increases in volume, its excess rises into the tank, pushing back the membrane and compressing the gas pumped into the upper part (in the picture on the left). This is displayed on the pressure gauge as an increase in pressure and can serve as a signal to reduce the combustion intensity. Some models have a safety valve that releases excess air/gas when a threshold pressure is reached.

As the coolant cools, the pressure in the upper part of the tank squeezes the coolant out of the container into the system, and the pressure gauge readings return to normal. That's the whole principle of operation of a membrane-type expansion tank. By the way, there are two types of membranes - disc-shaped and pear-shaped. The shape of the membrane does not affect the operating principle in any way.

Volume calculation

According to generally accepted standards, the volume of the expansion tank should be 10% of the total coolant volume. This means that you must calculate how much water will fit in the pipes and radiators of your system (it is in the technical data for radiators, and the volume of the pipes can be calculated). 1/10 of this figure will be the volume of the required expansion tank. But this figure is only valid if the coolant is water. If non-freezing liquid is used, the tank size is increased by 50% of the calculated volume.

Here is an example of calculating the volume of a membrane tank for a closed heating system:

the volume of the heating system is 28 liters;
expansion tank size for a system filled with water 2.8 liters;
the size of the membrane tank for a system with non-freezing liquid is 2.8 + 0.5 * 2.8 = 4.2 liters.

When purchasing, select the nearest larger volume. Don't take less - it's better to have a small supply.

What to look for when purchasing

There are red and blue cans in stores. Red tanks are suitable for heating. The blue ones are structurally the same, only they are designed for cold water and cannot tolerate high temperatures.

What else should you pay attention to? There are two types of tanks - with a replaceable membrane (they are also called flanged) and with a non-replaceable one. The second option is cheaper, and significantly, but if the membrane is damaged, you will have to buy the whole thing. For flanged models, only the membrane is purchased.

Place for installing a membrane type expansion tank

Usually they place an expansion tank on the return pipeline in front of the circulation pump (if you look in the direction of flow of the coolant). A tee is installed in the pipeline, a small section of pipe is connected to one part of it, and an expander is connected to it through fittings. It is better to place it at some distance from the pump so that pressure differences are not created. An important point is that the piping section of the membrane tank must be straight.

A ball valve is installed after the tee. It is necessary to be able to remove the tank without draining the coolant. It is more convenient to connect the container itself using an American nut. This again makes installation/disassembly easier.

Please note that some boilers have an expansion tank. If its volume is sufficient, installing a second one is not required.

The empty device does not weigh much, but when filled with water it has a significant mass. Therefore, it is necessary to provide a method of mounting on the wall or additional supports.

Circulation pump

The circulation pump ensures the operation of the closed heating system. Its power depends on many factors: the material and diameter of the pipes, the number and type of radiators, the presence of shut-off and thermostatic valves, the length of the pipes, the operating mode of the equipment, etc. In order not to go into the intricacies of calculating power, the circulation pump can be selected according to the table. Select the nearest larger value for the heated area or the planned thermal power of the system, and find the required characteristics in the corresponding line in the first columns.

In the second column we find the power (how much coolant it can pump in an hour), in the third - the pressure (system resistance) that it is able to overcome.

When choosing a circulation pump in a store, it is advisable not to save money. The entire system depends on its performance. Therefore, it is better not to save money and choose a trusted manufacturer. If you decide to buy unknown equipment, you need to somehow check it for noise levels. This indicator is especially critical if the heating unit is installed in a residential area.

Strapping scheme

As mentioned earlier, circulation pumps are installed mainly on the return pipeline. Previously, this requirement was mandatory, today it is only a wish. The materials used in production can withstand heating up to 90°C, but it’s still better not to take risks.

In systems that can also operate with natural circulation, during installation it is necessary to provide for the ability to remove or replace the pump without the need to drain the coolant, as well as for the possibility of operation without a pump. To do this, a bypass is installed - a workaround through which coolant can flow if necessary. The installation diagram of the circulation pump in this case is shown in the photo below.

In closed systems with forced circulation, a bypass is not needed - without a pump it is inoperative. But two ball valves on both sides and a filter at the inlet are needed. Ball valves make it possible, if necessary, to remove the device for maintenance, repair or replacement. The dirt filter prevents clogging. Sometimes, as an additional element of reliability, a check valve is also installed between the filter and the ball valve, which will prevent the coolant from moving in the opposite direction.

Connection diagram (piping) of a circulation pump to a closed-type heating system

How to fill a closed heating system

At the lowest point of the system, usually on the return pipeline, an additional tap is installed to feed/drain the system. In the simplest case, this is a tee installed in a pipeline, to which a ball valve is connected through a small section of the pipe.

In this case, when draining the system, you will need to substitute some kind of container or connect a hose. When filling the coolant, a hand pump hose is connected to the ball valve. This simple device can be rented at plumbing stores.

There is a second option - when the coolant is just tap water. In this case, the water supply is connected either to a special boiler inlet (in wall-mounted gas boilers), or to a ball valve similarly installed on the return line. But in this case, another point is needed to drain the system. In a two-pipe system, this may be one of the last radiators in a line, with a drain ball valve installed at the lower free inlet. Another option is presented in the following diagram. Shown here is a closed-type single-pipe heating system.

Diagram of a closed one-pipe heating system with a system power supply unit

Water is the most unique substance in nature. It has an abnormally high heat capacity, which in nature prevents sudden changes in temperature, because it cools slowly and heats up slowly. Reducing the specific gravity of water when heated is used in the simplest heating systems to create pressure and move it in the pipes of the circuit. In simple systems, to compensate for the increase in water volume, an expansion tank for the heating system is used, connected to the circuit pipelines.

In modern water heating systems, several types of expansion tanks are used. There are three types of tanks used for circuits: open expansion tanks, membrane closed expansion tanks and battery (storage) tanks. These tanks occupy a special position, because they are a kind of batteries in the circuit. They accumulate thermal energy in the form of heated water in a large container.

For reliable and safe operation, the heating system must maintain stable pressure.

It is known that liquids are incompressible, and if the circuit is made sealed, then when the water is heated, the pressure in the system will sharply increase. A pressure surge can lead to destruction of the boiler and heating circuit.
The task of maintaining stable pressure is assigned to a special tank for the heating system, which receives excess liquid that occurs when it is heated.

Open tank design

An open type tank is a container communicating with the atmosphere, which is connected to the heating circuit through a pipe. Water in an open tank constantly evaporates, so it is necessary to provide for the possibility of “topping up” water from the water supply. An open expansion tank is used for heating gravity-type water circulation. Such tanks do not have any shut-off valves, but to reduce evaporation the tank is equipped with a lid. You can purchase an expansion tank for heating, the price of which is low due to the simplicity of the design, in any online store.

How to calculate tank volume

Every owner should know how to calculate the volume of an expansion tank for heating of any configuration and design. There are two methods for calculating the required tank volume for a heating circuit. The first method is a simple rough method that gives good results. Using this method, the volume of the tank is determined as 10% of the amount of coolant. This value also includes the necessary margin, which ensures efficient operation of the circuit. For open systems, this method of calculation gives results sufficient in accuracy for the manufacture or selection of a tank. The second method is to calculate an expansion tank for a closed heating system, which will be discussed below.

Open tanks and their applications

Open expansion tanks are used only in simple heating circuits with natural circulation. During installation, these systems require increased attention, because to move water, it is necessary to slope the pipes along the direction of its movement, installing an expansion tank in the heating system at the top, on the supply manifold. The tank is installed at the top point of the circuit. This creates a certain pressure in the system and removes air from the circuit independently.

You can buy or order an expansion tank for open-type heating, the price of which depends on the volume and material of the housing, in many specialized stores. The tank is most often made of stainless steel.

Closed expansion tank

An open heating system, along with its positive qualities, has a lot of disadvantages. It is cumbersome, the circuit pipes cannot be hidden under the floors due to circulation problems, and it is impossible to organize a working floor system when using an open system. Modern heating systems with a circulation pump, closed from access to atmospheric air, have appeared. In them, the thermal expansion of the coolant is compensated by an expansion tank for closed-type heating, which is usually installed in the “return”. When purchasing a system element such as the price usually directly depends on its volume. It is best to buy it after making a calculation.

Calculation of the volume of a closed expansion tank

When installing it yourself, you need to know how to choose an expansion tank for heating your home. There is a calculation method that requires knowledge of certain quantities.

You can calculate the required volume using the formula:

(UOV x KVK)/100 x (Dcont + 1)/Dcont – Dbak. In this formula:

UOV - increase in the volume of water when heated - 5%, and for antifreeze 7 - 8%
KVK – volume of water in the circuit.
Dkont - maximum pressure in the circuit and boiler. These data, which influence the selection of an expansion tank for heating, are contained in the technical documentation for the boiler.
Dtank is the nominal pressure in the chamber of a closed membrane tank. The pressure value is indicated in the passport for the expansion tank. For example, the German company Reflex sets a pressure of 1.5 bar in tanks with a capacity of up to 33 liters.

There is a certain relationship between the volume of the tank and some parameters that influence the selection of an expansion tank for the home heating system. The dependence of the required tank volume on the volume of the coolant and its maximum temperature is direct. But the dependence on the permissible pressure in the system is the opposite. The higher the permissible circuit pressure, the smaller the volume can be. After calculating the volume, you can buy an expansion tank for the heating system or order it at any specialized store.

Design of closed expansion tanks

The structure of the closed expansion tank is extremely simple. It is made in the form of a sealed steel case with a membrane made of special rubber, which divides the internal compartment of the tank into two parts. A pipe is mounted at the bottom for connection to the heating circuit, and the upper part of the tank is filled with gas, usually neutral gas nitrogen is used. A nipple is installed at the top of the container. By pumping air through this nipple, the initial operating pressure is created.

For proper operation, you need to know what pressure should be set in the expansion tank of the heating system.

Typically, the value of this pressure is indicated in the passport for the tank.

Features of closed expansion tanks

It is important that atmospheric air does not come into contact with the liquid, which significantly reduces corrosion and the amount of air dissolved in water. The pressure in the tank changes synchronously with the pressure in the system. Installation usually does not cause difficulties, and the installation of an expansion tank in a closed heating system is usually horizontal or vertical.

You need to clearly understand how to connect the expansion tank to the heating system for proper and long-term operation. It would be correct to connect the expansion tank in the “return” before.

Long-term and reliable operation of a closed expansion tank is determined by the properties of the membrane. Some tank designs allow the installation of a replaceable membrane. Naturally, you will have to buy an expansion tank for heating at a high price, because if you replace the membrane, you will not need to change the tank body.

Membranes that are installed in expansion tanks can be of the following types:

Storage tank for heating

The main task that a storage tank for heating solves is the accumulation of thermal energy for reserve. Their use is relevant for solar collectors, when used for heating solid fuels and, especially if the “night tariff” for electricity is used to heat the coolant. Structurally, the tank is a tall cylindrical or parallelepiped-shaped container with several pipes. Its volume depends on the power of the boiler. Tanks with a volume of 0.2 to 3 cubic meters are produced.

Connecting the storage tank to the circuit

The accumulator storage tank in the heating system is connected with the upper part to the supply pipeline, and the lower part to the “return” pipe. Several layers of water with different temperatures are formed in the tank, which can be directed to the desired consumers through additional pipes.

Popular expansion tanks from the German company Reflex

Due to their highest quality and widest range, products from the German company Reflex occupy a leading position on the market. The company produces expansion tanks of various types and volumes. The tanks are produced in three series, from which it is easy to select a membrane expansion tank for the Reflex heating system of a suitable volume.

The Reflex company occupies a leading position in the market in the production of tanks of the following series:

The heating system, being a complex engineering structure, consists of many elements that have different functional purposes. The expansion tank for heating is one of the most important parts of the heating system circuit.

When the coolant is heated, the pressure in the boiler and the heating system circuit increases significantly due to the temperature increase in the volume of the coolant fluid. Considering that the liquid is a practically incompressible medium and the heating system is sealed, this physical phenomenon can lead to the destruction of the boiler or pipelines. The problem could be solved by installing a simple valve that could release the excess volume of hot coolant into the external environment, if not for one important factor.

When cooling, the liquid contracts and air enters the heating circuit in place of the discharged coolant. Air jams are a headache for any heating system; they make circulation in the network impossible. Therefore it is necessary. Constantly adding new coolant to the system is very expensive; heating cold water is much more expensive than heating the coolant that came into the boiler through the return pipeline.

This problem is solved by installing a so-called expansion tank, which is a reservoir connected to the system by one pipe. Excess pressure in the heating expansion tank is compensated by its volume and allows for stable operation of the circuit. Externally, expansion tanks for the heating system, based on the calculation results and the type of heating circuit, are different in shape and size. Currently, tanks are produced in various shapes, from classic cylindrical tanks to so-called “tablets”.

Types of heating systems

There are two schemes for building heating networks -. An open (gravity) heating system is used in centralized heating networks and allows water to be directly withdrawn for hot water supply needs, which is impossible in private housing construction. Such a device is located at the top point of the heating system circuit. In addition to leveling pressure drops, the heating expansion tank performs the function of natural separation of air from the system, since it has the ability to communicate with the outside atmosphere.

Thus, structurally, such a device is a compensation tank of the heating system, not under pressure. Sometimes a system with gravitational (natural) circulation of a heat-carrying fluid may be mistakenly called open, which is fundamentally incorrect.

With a more modern closed circuit, an expansion tank of a closed-type heating system with a built-in internal membrane is used.

Sometimes such a device can be called a vacuum expansion tank for heating, which is also true. Such a system provides for forced circulation of the coolant; air is removed from the circuit through special taps (valves) installed on the heating devices and at the top of the system pipelines.

Device and principle of operation

A structurally closed expansion tank in a heating system is a cylindrical tank with a rubber membrane installed inside, which divides the internal volume of the vessel into air and liquid chambers.

Membranes are of the following types:

Gas pressure is adjusted individually for each system, which is described in the instructions supplied with devices such as an expansion tank for closed-type heating. Some manufacturers provide the possibility of replacing the membrane in the design of their expansion tanks. This approach slightly increases the initial cost of the device, but subsequently, if the membrane is destroyed or damaged, the cost of replacing it will be lower than the price of a new expansion tank.

From a practical point of view, the shape of the membrane does not in any way affect the operating efficiency of the devices; it should only be noted that a closed-type balloon expansion tank for heating holds a slightly larger volume of heat-carrying liquid.

The principle of their operation is also the same - when the water pressure in the network increases due to expansion when heated, the membrane stretches, compressing the gas on the other side and allows excess coolant to enter the tank. When it cools down and, accordingly, the pressure in the network drops, the process occurs in the reverse order. Thus, regulation of constant pressure in the network occurs automatically.

It is necessary to focus on the fact that if you buy an expansion tank for the heating system at random, without the necessary calculations, then it will be very difficult to achieve stable operation of the heating network. If the tank size is significantly larger than necessary, the pressure required for the system will not be created. If the tank is smaller than the required size, it will not be able to accommodate the excess volume of heat-carrying liquid, which may result in an emergency situation.

Calculation of expansion tanks

To calculate an expansion tank for closed-type heating, you first need to calculate the total volume of the system, consisting of the volumes of the circuit pipelines, heating boiler and heating appliances. The volumes of the boiler and heating radiators are indicated in their passports, and the volume of pipelines is determined by multiplying the internal cross-sectional area of the pipes by their length. If the system contains pipelines of different diameters, then their volumes should be determined separately and then added together.

Further calculations for devices such as an expansion tank for closed-type heating are carried out using the formula V = (Vc x k) / D, where:

Vс – volume of heat-carrying fluid in the heating system,
k – coefficient volumetric thermal expansion, taken for water 4%, for 10% ethylene glycol - 4.4%, for 20% ethylene glycol - 4.8%;
D is an indicator of the efficiency of the membrane unit. It is usually indicated by the manufacturer or can be determined by the formula: D = (Рм – Рн) / (Рм +1), where:

Рм – the maximum possible pressure in the heating network, usually it is equal to the maximum operating pressure of the safety valve (for private houses it rarely exceeds 2.5 - 3 atm.)
Рн – initial pumping pressure of the air chamber of the expansion tank, taken as 0.5 atm. for every 5 meters of height of the heating system circuit.

In any case, it should be assumed that expansion tanks for heating should provide an increase in the volume of coolant in the network within 10%, that is, if the volume of coolant in the system is 500 liters, the volume together with the tank should be 550 liters. Accordingly, an expansion tank of the heating system with a volume of at least 50 liters is required. This method of determining volume is very approximate and can result in unnecessary costs for purchasing a larger expansion tank.

Currently, online calculators for calculating expansion tanks have appeared on the Internet. If such services are used to select equipment, it is necessary to carry out calculations on at least three sites to determine how correct the calculation algorithm of a particular Internet calculator is.

Manufacturers and prices

Currently, the problem of buying an expansion tank for heating lies only in the correct selection of the type and volume of the device, as well as the financial capabilities of the buyer. The market offers a wide selection of instrument models from both domestic and foreign manufacturers. However, it should be noted that if the purchase price for such devices as a closed-type expansion tank for heating is much lower than that of its main competitors, then it is better to refuse such a purchase.

The low cost indicates the unreliability of the manufacturer and the low quality of the materials used in its manufacture. Often these are products from China. As with all other goods, the price for a high-quality expansion tank for heating will not have a significant difference of about two to three times. Conscientious manufacturers use approximately the same materials, and the difference in price of models with similar parameters of about 10-15% is determined only by the location of production and the pricing policy of sellers.

Domestic manufacturers have proven themselves well in this market segment. By installing modern technological lines in their production, they achieved the production of products whose parameters are not inferior to the best global brands at a lower cost.

It should be borne in mind that it is important not only to buy an expansion tank for closed-type heating, it also requires its correct installation.

Having the necessary skills and following the instructions, you can install it yourself. If the technician still has any doubts about his knowledge, then it is best to turn to professionals to guarantee stable operation of the heating network and eliminate possible malfunctions.

In a heating system, a very important element is the heating expansion tank. Such a device serves to accept excess coolant at the moment when it expands, thus preventing rupture of the pipeline and taps.

The principle of operation of an expansion tank for heating is as follows: when the temperature of the coolant rises by 10 degrees, its volume increases by about 0.3%. Since the liquid is not burned, excess pressure appears that needs to be compensated. This is precisely why an expansion tank is installed.

Types of expansion tanks

Different types of expansion tanks are used in different heating systems. Previously, systems without circulation pumps used an open expansion tank for heating. But such tanks had many disadvantages, so nowadays they are used very rarely. Due to the fact that air gets into such an expansion tank for heating, corrosion appears, and the liquid evaporates faster and must be constantly replenished. Such a tank must be placed at the highest point of the heating system, and this is not always easy to implement.

Open expansion tank for heating

In such heating systems, where the coolant circulates using a pump, a closed expansion tank for heating is installed; the calculation here is that it is a sealed container that has an elastic membrane inside. A membrane (balloon or diaphragm) divides the tank into two parts. Air or inert gas under pressure is pumped into one part, and the other part is intended for excess coolant. The membrane inside the tank is elastic, so when the coolant enters there, the volume of the air chamber becomes smaller, the pressure in it increases, thus compensating for the high pressure in the heating system. When cooling, the reverse process occurs.

Construction of closed expansion tanks

A closed expansion tank for heating, a flat tank can be flanged (have a replaceable membrane) or with a non-replaceable membrane. The second type is in quite high demand due to its relatively low cost. But flanged expansion tanks are better in many ways - the pressure here can be higher, and if the membrane ruptures, it can be replaced.

The flanged expansion tank of the heating system can be either vertical or horizontal.

Here, the liquid, when it enters the tank, has no contact with the metal surface, since it is located inside the membrane. If the membrane is damaged, it can be replaced through the flange.

Vertical and horizontal flanged tanks

Tanks that do not have a replaceable membrane are fixed rigidly around the entire perimeter. From the very beginning, the diaphragm is pressed against the inner surface, since the volume of the expansion tank for heating is completely filled with gas. After this, the pressure in the heating expansion tank increases, and the liquid goes inside. When the system starts up, the pressure can rise sharply, so this is when the membrane can be damaged.

Selection of expansion tank

Choosing an expansion tank for heating is a responsible matter. In this case, you should definitely pay attention not only to its type and size, but also to the membrane - the following indicators are important: resistance to the diffusion process, operating temperature range, durability, compliance with sanitary requirements.

Today there is a wide range of expansion tanks for heating systems on the market.

In addition, it is necessary to determine the ratio of the boundaries of the pressure range, which is extremely permissible. Before purchasing a tank, be sure to check whether it meets existing quality and safety standards.

Calculation of tank volume

First of all, let’s determine the relationship between the required volume and the parameters that influence it. When making calculations, it must be taken into account that the larger the capacity of the heating system and the higher the maximum temperature of the coolant in it, the larger the tank should be. The higher the permissible pressure in the heating expansion tank, the lower it can be. Of course, the calculation method is quite complex, so it is better to consult a specialist. After all, a mistake in choosing an expansion tank can cause frequent operation of the safety valve or other troubles.

The volume is calculated using a special formula. Here the main quantity is the total volume of coolant that is present in the heating system. This value is calculated taking into account the power of the boiler, the number and types of heating devices. Approximate values: radiator – 10.5 l/kW, floor heating system – 17 l/kW, convector – 7 l/kW.

To make a more accurate calculation of a device such as a vacuum expander for heating, the formula is used: Tank volume = (Volume of water in the heating system * Expansion coefficient of the coolant) / Efficiency of the expansion tank. The expansion coefficient for water is 4% when it is heated to 95 degrees. To determine the efficiency of the tank, another formula is used: Tank efficiency = (Highest pressure in the system - Initial pressure in the air chamber) / (Highest pressure in the system + 1).

Expansion tank useful volume coefficients

Thus, the vacuum expansion heating tank is selected taking into account the strength and temperature characteristics, which should not exceed the permissible values at the connection point. The volume of the tank can either be equal to or greater than the result obtained as a result of the calculations.

Installation of expansion tank

Installation of the expansion tank of the heating system is done in accordance with the project and instructions. Your best option would be to have a specialist do this. If this is not possible, then at least consult with him. The installation of an expansion tank for heating, if it is an open type, is carried out at the highest point of the heating system. A closed tank can be placed almost anywhere, but not directly after the pump.

One of the options for installing an expansion tank in the heating system

It is necessary to pay special attention to such an issue as fastening the heating expansion tank, since the mass of the tank, which is filled with water, increases significantly. Another important point is the possibility and convenience of servicing the tank and free access to it.

Expansion tank maintenance

The role of such a device as the expansion tank of the heating system cannot be underestimated; the instructions for this device provide a list of rules for its maintenance. These include:

Once every six months it is necessary to check the tank for external damage - corrosion, dents, leaks. If suddenly such damage is found, then it is imperative to eliminate its cause.
Once every six months, you need to check the initial pressure of the gas space for compliance with the calculated indicator.
The integrity of the membrane is checked once every six months. If a violation is detected, it must be replaced (if such a possibility is provided).
If the tank will not be used for a long time, then you need to keep it in a dry place and drain the water from it.

Next is how to check the heating expansion tank - its initial pressure of the gas space. To do this, disconnect the tank from the heating system, drain water from it, and connect a pressure gauge to the nipple of the gas cavity. If the pressure is lower than what was set at the same time when the expansion tank for heating was set up, the tank must be inflated with a compressor through the same nipple.

Pressure gauge readings for correct operation of the expansion tank

Checking the integrity of the membrane is also an important point. If suddenly, while checking the pressure of the gas space after you have drained the water, air flows through the drain valve, and the pressure in the gas space has decreased to atmospheric pressure, then the membrane is broken.

To replace the membrane, you need to go through several steps. First of all, the tank is disconnected from the heating system, then it needs to be drained. Next, the pressure of the gas cavity is released through the nipple. The membrane flange is dismantled. It is located in the area of the pipe connection to the pipes. The membrane included in the expansion tank device for heating is removed from the hole at the bottom of the housing.

Then you need to check the inside of the case to make sure there is no dirt or corrosion; if there is any, you need to remove them and rinse them with water, and then dry them. To remove corrosion, do not use products containing oils! The membrane holder is inserted into the hole at the top of the membrane. The bolt is screwed into the membrane holder, it is placed in the housing, and the holder is retracted into the hole in the bottom of the housing. The holder is then secured with a nut. After this, a membrane flange is placed on the body.