Where is the expansion tank located? Expansion tank for heating of open type. Main problems and malfunction of the expansion vessel

1. Types of expansion tanks
2. Features of the installation of expansion tanks
3. Mistakes made when installing the expansion tank

Today, it is possible to equip a heat supply system in a private house as soon as possible.

The main thing that is necessary for this is sufficient financial capabilities of the property owner, and then the planned will be implemented, since the domestic building materials market offers a wide selection of heating equipment and components.

One of the highlights of creating a system is the installation of an expansion tank in the heating system.

It is on him that the performance of the heating network of a private house largely depends.

Types of expansion tanks

The place where the expansion tank of the heating system should be installed, such as in the photo, is determined based on the type of construction, which happens:

• open;
• closed.

It should be noted that open-type heating systems are rarely installed today.

They are found in buildings built about a few decades ago. The expansion tank, the device of which is made according to an open type, has the form of a container with an open upper part and a threaded connection at the bottom, at the bottom. Through it, an open-type expansion tank is connected for heating. The tank of this outdated model is located in the highest place of the system.

In a closed-type heating structure, an expansion device is used, the installation and further operation of which have their own characteristics and differences.

The tank is made in the form of a sealed capsule with two chambers separated from each other by a rubber membrane. Therefore, the product is also called a membrane expansion tank of the heating system.

The device of an expansion tank of a closed type is allowed anywhere in the heating network, with the exception of the tie-in tank after the circulation pump in its immediate vicinity.

Otherwise, pressure surges throughout the system are possible.
The principle of operation of a closed type tank is simple. After the coolant has heated up and increased in volume, its excess fills the empty space in the membrane device. As a result, the pressure in the system continues to remain at acceptable level(read: “We make the selection of an expansion tank for heating”).

The installation of an expansion tank in the heating system is carried out taking into account some points:

• installation of the device is allowed in a room where the temperature does not fall below zero;
• easy access to the air valve should be provided in order to regulate the pressure in the air part of the tank if necessary;
• when the installation of the device is completed, access to the shut-off equipment, drain cock and nameplate must be available;
• it is impossible to allow the application of a static load to the membrane tank (pressure from pipes and other devices);
• if the reducer is located after the water meter, such a measure will allow maintaining a constant initial pressure in the membrane tank.

  When the safety valve is triggered, the pressure should not exceed the level of the maximum allowable working pressure in the tank (read: “Safety valve for heating - what are there, how to use it correctly”);

• the expansion tank for heating is fastened in such a way that the safety valve is up to the flow fittings in the direction of the coolant.

The heating scheme with an expansion tank always provides that its installation is carried out only from the side from which cold water is supplied to the heating boiler.

Installing an outlet device is prohibited.

Mistakes made when installing an expansion tank

Many property owners try to do many of the work on arranging the heat supply system on their own, including mounting an expansion tank with their own hands.

At first glance, it seems that there will be no problems with such work, but in reality it has certain difficulties, which are well known to specialists.

The most common mistakes made when installing an expansion tank in a heating network occur for a number of reasons:

• lack of a complete set of necessary tools or their poor quality.

  When doing work, they often use keys - universal (gas) and adjustable.

  In addition to them, a special key is also required, which is necessary when installing a metal-plastic pipeline, and a stepped key for detachable connections;

• application for sealing materials that are not intended for these purposes. For example, instead of high-quality sealant, they use cheap products for PVC windows, which are intended for a different temperature regime.

  The first time after applying the connections look attractive, but after commissioning the heating structure, this type of sealant cannot withstand the load and high operating temperatures.

  Expansion tank for heating - installation diagram in open and closed systems

  It is good if a leak is found as a result, but often the consequences are more serious;

• the installation of an expansion tank in the heating system was made in a hard-to-reach place and the approach is almost impossible;
• the calculation of the volume that the expansion tank should have is incorrectly calculated, or the device was purchased at random.

It should be noted that the installation and fastening of the heating expansion tank must be carried out in accordance with accepted norms and rules that ensure safe operation.

Before installation, you must correctly determine the installation location of the device.

After the installation of the expansion membrane tank is completed on its own, everything seems to look great, and the inaccuracies made at the same time are invisible. The disadvantages will become apparent after the heating season has started, and most importantly, this will happen at the most inopportune moment.

For example, it is cold outside, and the heating system is out of order.
Watch a video on installing an expansion tank in a heating system:

In order not to run into problems in the future, it is necessary to familiarize yourself with the recommendations from the manufacturer for the installation of such an element of the heat supply system as an expansion tank.

This information will help to avoid unnecessary expenses: time, physical and financial.

One of the key elements of the cooling system in a modern car is the expansion tank. This is a kind of reserve reservoir for an additional amount of liquid during the operation of the system.

I'm thinking about the meaning of the reservoir looking for faults in the thermostat or the radiator itself.

However, expansion vessel problems are often caused by air overload in the cooling system, which leaves the car without heat during the cold season.

An alarming symptom for the car owner is the regular overheating of the engine. It is important to check the status of this part, but first you need to know exactly how the device works.

What is the purpose of an expansion vessel and how does it work?

The urgent need for such a reservoir was created when, instead of cooling water, special liquid, which is able to maintain its physical properties even at extremely low temperatures.

The basis of these solutions is alcohol and ethylene glycol (rarely propylene glycol).

As it heats up, the alcohol expands and starts to seep through the pressurized radiator fan valve. During the ICE cooling process, the temperature of the antifreeze or antifreeze is reduced by the formation of an empty void.

How to fill the expansion vessel for heating?

The spaces are filled with air, which, with the subsequent activation of the engine, creates plugs that prevent the free passage of fluid into the cooling system. This can lead to a general overheating of the engine.

To avoid overheating problems, an expansion vessel was supported, which was connected to the radiator by a pipe. The center of the reservoir is at the level of the top of the radiator, so that the heated fluid rises and freely flows from the radiator space into the reservoir.

The hose itself is attached to the bottom of the product, which allows excess antifreeze or antifreeze back to the radiator during cooling without air intake.

Where is the expansion tank

IN different models the tanks are located in the most suitable zones of the cooling system.

A container is needed next to the radiator.

The material for the manufacture of the container is durable and transparent plastic. In one part of the product, there are always scale marks that allow you to control the level of antifreeze in the system. The last risk on the bottom shows the minimum liquid level.

The maximum amount of cold wind antifreeze should be just over 30 mm above the upper risk level on the tank scale.

Main problems and malfunction of the expansion vessel

Most often, car owners complain about a problem such as a leaking expansion vessel.

This may be due to a violation of the integrity of the tank (for example, after a bad parking or other collision), as well as violations of the pipeline that connects the drain tank and the radiator.

The strong pressure in the container is emptied using a special release valve on the container lid. It is necessary to carefully monitor the condition of the cover, remove it from the scale and corrosion, otherwise the valve and the entire system will quickly work.

An error in the expansion vessel causes a strong drop in the liquid in the engine cooling system, which has a very negative effect on its operation.

Installation of an expansion tank for closed-type heating

Installing an expansion tank for closed-type heating allows you to equip a heat supply system in a private house in the shortest possible time.

The main thing in this business is enough finances for the implementation of the conceived idea. Today, the Russian building materials market presents a wide range of thermal equipment, as well as components for heat supply schemes.

When arranging a heating system, it is very important to install a closed type heating expansion tank.

In the future, the functionality of the entire heating network of the dwelling will depend on this detail.

Types of expansion tanks

Elements to prevent air leakage into the line are of different designs.

Based on this, a specific installation of the expansion tank of the heating system is carried out. There are closed and open heat supply schemes.

Installing an expansion tank in an open heating system is rarely used.

As a rule, it is typical for buildings of the Soviet period. The expansion tank, the design of which is made according to this type, is a container with an open top and a threaded connection at the bottom, at the bottom. Using such a connector, an open type element is connected to the heating circuit. The scheme for installing an open expansion tank for heating - provides that it must be located at the highest point of the system.

The closed-type heating structure has a special device, so the installation of an expansion tank for closed-type heating has its own characteristics.

The container is made as a sealed capsule, which has two chambers separated by a rubber membrane. Therefore, this design is also called a membrane tank of the heating system. This item can be used anywhere heating system except for the place behind the circulation pump, as well as directly next to it.

Failure to comply with this precaution may result in pressure drops within the system.

The scheme for installing an expansion tank in a closed-type heating system is simple.

The heated coolant expands, its excess squeezes air out of the membrane device, and the system pressure remains unchanged.

Features of mounting expansion tanks

The installation of a vacuum heating expansion tank must be carried out taking into account some aspects:

• installation of the structure is carried out in a room with positive temperature;
• it is necessary to provide free access to the air valve to adjust the pressure if necessary;
• upon completion of the installation of the tank, access to the drain valve and shut-off equipment is left free;
• the scheme for installing a membrane expansion tank for heating is carried out so that the safety valve is located before the flow fitting.

To be fulfilled correct installation expansion tank in the heating system, you will need the following tools:

• adjustable and stepped wrench;
• wrench for mounting PVC pipes.

First, you should do the preparatory stage, which includes disconnecting the boiler from gas supply, electricity or water supply.

Then the valve is closed, which is responsible for the circulation of the coolant, it is drained from the system.

Step-by-step steps for installing an expansion tank in a closed heating system:

Why do you need an expansion tank for a closed heating system?

Install a drain and stopcock on the supply pipe to drain and shut off the water.

2. Connect the expansion vessel to the system using screws.

If the options for installing an expansion tank in the heating system require the presence of polypropylene pipes, a soldering machine, fittings, couplings and corners should be used.

Before installing the fitting, it is necessary to wrap linen tape around the thread and apply sealing paste.

4. After draining the water system, cut the pipe with scissors and install a tee.

Before putting the system into operation, be sure to blow out the coarse filter.

Be sure to check the working pressure with the pump.

7. After connecting the expansion tank to the network, start all the coolant supply valves, turn on the boiler.

It is advisable to install a safety valve that comes with the tank; if it is not available, it should be bought separately.

Read also:
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– Private house – heating installation and pipe laying options

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In order to compensate for the thermal expansion of the coolant in the heating system, tanks of an open or closed type are arranged. They come with natural and forced circulation. The volume of the liquid tends to change, as the coolant expands and contracts during operation.

To stabilize the pressure on the internal walls of the elements in the heating system, as well as to compensate for changes in the volume of liquid, expansion tanks are used.

Types of tanks
2. Expansion tank open type
2.1 Advantages and disadvantages
2.2 How an open tank works. Installation rules
3. Expansion tank of closed type
3.1 Membraneless tanks
3.2 Diaphragm tanks
3.3 Advantages and disadvantages of a membrane tank
3.4 How to choose a membrane tank
3.5 Installing closed expanders

Types of tanks

There are two types of expansion tank:

1. Expansion tank of open type.
2. Expansion tank of the closed type.

When the temperature of the liquid in the pipeline decreases and for its natural return, an open-type tank is installed at the highest point of the heating system.

A tank of this type is a volumetric container that communicates with the atmosphere.

The expansion tank of a closed type has the form of a sealed vessel, which is filled in one half with liquid, and in the other with gas or air, which is under pressure.

After heating, the liquid moves into the expander, and the gas is compressed at this time. The liquid is returned back after cooling, and the resulting difference in volume is filled with gas.

Expansion tank open type

Let us consider in more detail all the features of an open type tank. The tank is used with a small leak to replenish water. And also for air intake from the system.

Such a tank can be cylindrical or rectangular and is usually made of steel or polymeric materials.

Since the expansion mat is installed at the top, the heating pipelines must be long. For maintenance of this device, as well as cleaning from contamination, a cover is provided on top of the tank.

You can install an open-type expansion tank in a special room on the roof of the house, in a stairway or in the attic.

If your house has high ceilings, then such a tank is well placed in a bathroom or household. room. If the containers go beyond the heated room, then they should be insulated to avoid heat loss.

Advantages and disadvantages

Advantages of open tanks:

1. Relieves pressure and removes air from the heating system.
2. Low cost device.

The disadvantages include:

1. Large heat loss and the need for insulation of some elements.
2. Before installation, it is necessary to arrange additional heating pipelines.
3. Since the system evaporates a certain amount of coolant, it is necessary to replenish it periodically.
4. Possibility of corrosion of steel elements due to contact with the atmosphere.

Due to the shortcomings of this equipment, it is used less and less, giving preference to closed tanks.

How does an open tank work?

Installation rules

To prevent stagnation of water in the tank, it is necessary to arrange circulation. A contour is arranged between the tank and the main pipeline. It should consist of a circulation and expansion pipe. The opening of the circulation pipe must be located 0.5 cm below the expansion pipe.

Due to the circulation from the heating system, air bubbles are released into the atmosphere. Such a system is suitable for forced circulation. If the system is equipped with natural circulation, then it is necessary to connect an expander at the top of the supply pipe.

Expansion tank closed type

The tank of the closed type has the form of a sealed vessel, which is made of steel. Part of the tank is filled with an inert gas, and the second part is filled with liquid. The expansion tank of the closed type is of two types: membrane and membraneless.

Membraneless tanks

In such tanks there is no internal separation of space, so the coolant is in direct contact with the gas.

A gas cylinder or compressor is installed outside to maintain pressure inside the tank. Gas supply and pressure control occur automatically.

Membrane tanks

Membrane tanks are more popular, as they are separated by a flexible membrane. Therefore, gas and liquid do not come into contact.

There are tanks with a disk-shaped membrane and with a pear-shaped (balloon) membrane.

The first membrane is attached in the middle of the tank and looks like a hemisphere.

It can become concave or convex depending on changes in water temperature.

The second membrane is similar to a vessel and is attached to different ends of the vessel. There is gas between the membrane and metal walls, so the coolant does not come into contact with the walls of the tank. Therefore, such a tank is protected from corrosion and has a long service life.

In this tank, the membrane can be replaced. Expanders are produced with butyl and ethylene propylene membranes. They are highly durable.

Advantages and disadvantages of a membrane tank

Advantages of a membrane tank:

• It is not necessary to arrange thermal insulation;
• Heat loss is minimal;
• Operates at high pressure;
• Small size;
• You can install the tank almost anywhere;
• The tank is well protected against corrosion, as it does not come into direct contact with the atmosphere.

The disadvantages include:

• Periodic pumping of air or gas;
• Great cost;
• The pressure in the system must be controlled.

How to choose a membrane tank

Membrane tanks are oval and flat with a diaphragm.

The second option is more compact, it can be installed between the wall and the interior. Thus, you will save space in your home. The main parameters of such a tank is the required volume of liquid. It is pre-calculated.

The service life of the tank depends on the quality and parameters of the membrane.

The main characteristics of the membrane:

1. The material from which the membrane is made.
2. Operating temperatures and pressure.
3. diffusion stability.

Tanks that are used for heating are painted red, and those used for the water supply system are painted blue.

Installation of closed expanders

If the tank is closed type with forced circulation, it is recommended to install it before the circulation pump.

Installation can be done in any position, but the best option would be the top fluid supply. Since the air bubbles will be discharged naturally. The tank will work even if the membrane is damaged.

Some heaters already have an expansion tank built in, in which case there is no need to install an additional one.

Do-it-yourself installation and installation of an expansion tank in a heating system

If you decide to change the water to another coolant, you may have to replace the tank with a higher volume. But you can also install an additional expander.

When installing a closed type tank with natural circulation, it is necessary to install an automatic float valve. It is arranged at the top of the system to release air when the system is full. If, when using the tank, you notice that its volume is not enough for you, instead of buying a new one, it will be more profitable to install an additional tank of the right size.

One of the mandatory elements of engineering systems in a private house is an expansion tank for closed-type heating - the installation and selection of such equipment or its analogues for open systems must be carried out in full accordance with technical specifications facility and operating conditions. Only compliance with this condition will ensure durability, correct operation and safety of individual heating.

The main purpose of the expansion tank is to level the expansions of the coolant (water) when the temperature changes, which makes it possible to avoid extrusion of gaskets and destruction of pipelines and. The volume of the tank is calculated individually, based on the parameters of the system. The principle of operation and the design of models differ for systems of various types.

Designs of various systems and their features

Open heating systems

Open heating systems usually do not have a circulation pump and are equipped with leaky tanks (with lids or completely open). The expansion tank in such a system is a reservoir into which water is added as needed. The device of such a tank is simpler, and the cost is much lower compared to closed models.

You can buy an expansion tank for open-type heating, or you can make it yourself, which, with certain skills and the availability of materials and equipment, is not so difficult

At the same time, such a device has a number of disadvantages:

• Due to the lack of tightness of the system and the frequent opening of the lid, a significant amount of oxygen enters the system with air. Its presence provokes the formation of rust on the walls of metal elements (radiators and pipes).
• Leakage of the system also contributes to the evaporation of the coolant, which becomes more intense with increasing temperature. Thus, the addition of water to the expansion system is required quite often.
• For an open system to work effectively, the expander must be mounted as high as possible (not below the highest point of the wiring). This is not always convenient, besides, such installation requires more time and effort.
• The need for thermal insulation to reduce heat loss, especially if the tank is located in an unheated room.

Note: An additional function of the open-type expansion tank is also the removal of air from the system.

Closed systems

The amount of water in a closed heating system is constant. The coolant circulates through the piping using a special pump. The expansion tank for heating of a closed type is a tank divided into two chambers by a flexible membrane. While one of them receives water from the system, expanding when heated, the air in the second is compressed.

Expansion tank for a closed heating system, the price of which is higher due to the more complex device, at the same time more practical and convenient to operate. Ensuring the integrity of the system and not causing corrosion, it quickly pays for the money spent on the acquisition. The removal of air from a closed system in this case cannot be carried out using an expander. For this, special valves are used.

The advantages of closed type expanders are:

• compactness,
• minimum heat loss in the absence of the need to provide thermal insulation,
• lack of contact of the coolant with air, which eliminates the possibility of evaporation and reduces the risk of corrosion,
• big choice installation locations (almost anywhere),
• high allowable pressure.

Expander Maintenance

When using an expansion tank for heating, the following recommendations should be followed:

• Twice a year, inspect the system, checking for mechanical damage, rust in the tank - for all types.
• Check pressure every six months - for closed systems.
• Periodic checking of diaphragm condition - for closed systems.
• At a break in use - empty the tank and dry it - for all types.
• Observe the manufacturer's instructions regarding the permissible pressure and temperature values.
• Use only branded repair parts - mainly for closed tanks.
• Preferably, an inert gas is used for the closed expander chamber.

Calculation of the volume of the expansion tank

Regardless of the type of system (open or closed), it is generally accepted that the expansion tank should increase the total volume of the entire system by 10%, that is, with 300 liters of water in pipelines and radiators, the volume of the system with a tank should be 330 liters, that is, an expander of 30 liters is needed.

It is important to bear in mind that the need for a ten percent increase is valid only for heating using water as a heat carrier. If glycol liquid is used for this purpose, the tank volume is increased by 50% of the value calculated for the water tank. This difference is due to the different expansion coefficients of water and glycol.

Many users find it difficult to calculate the total volume of coolant in the system. It can be produced in different ways.

• The most accurate method will be the calculation of an expansion tank for heating with the measurement of the geometric parameters of all elements of the system (pipelines and radiators). After that, the volume of each of them is calculated separately, and the results obtained are summarized. Calculations will require a certain amount of time, however, carrying out such work is fully justified by the accuracy of the result and the ability to choose the optimally suitable expander model.
• More in a simple way is to track the flow of water by the meter when filling the heating system. However, this method can only be applied to open systems.
• Another option is to take the heater power as the initial parameter. According to the standards, for every kilowatt of boiler power, there are 15 liters of liquid. The method is applicable in cases where you are sure of the accuracy of the calculations for choosing a heater.

Installation work

Strict observance of the installation rules when equipping an open or closed type heating system with an expander will ensure the safety and efficiency of the equipment.

Installing an open type expansion tank

It has already been said above that the expansion tank for an open system is mounted at the highest point. This requirement is due to two factors:

• The rise of the coolant into the expander and draining it back into the heating system must be carried out by gravity, because there is usually no circulation pump in such systems.
• This arrangement of the expansion tank allows you to effectively carry out its additional function - air removal. Bubbles always rise to the top.

A feature of installing the expander in an open system is that there is no need to equip the tank with shutoff valves. As a rule, the tank is supplied with only two nozzles, through one of which the coolant enters the tank, and through the other it returns to the system. Even the presence of a lid on the tank is not essential, although its absence can lead to an increase in the loss of water volume from evaporation, as well as the ingress of debris and dust into the system.

Installation of a closed tank

Installing an expansion tank for heating in closed systems is somewhat more difficult, since it is a completely sealed device. Unlike open expanders, which users often make on their own, such units are created only at the factory, so you will have to buy an expansion tank for the heating system if you have one of this type.

There are several rules, following which you can install the heating expansion tank correctly.

You can learn about what and what to look for when buying from a separate article.

Criterias of choice storage water heaters are given. Often in private homes, preference is given to them.

What water filters will be useful in a country house, we told in this material

• It should be remembered that the installation of an expansion tank in the heating system involves the selection, purchase and installation of a model with a red body. Models painted in blue are designed for cold water supply. Structurally, the expanders do not differ from each other, but the red ones are designed for long-term high-temperature exposure.
• Despite the generally accepted practice of using a circulation pump only for closed systems, the presence of a pumping unit does not change the state of the system. That is, if you put a circulation pump on heating with an open tank, it will not become closed. Just in open systems, most often there is no need for such units.
• The boiling of the coolant in the heating system has nothing to do with the operation of the expander. Most likely, the slope of horizontal pipelines and the diameters of the pipes used should be reconsidered.
• It is not recommended to install an expander in close proximity to the pump due to possible pressure drop.
• During installation, use only special heat-resistant sealants.
• When installing the expander, take into account the need for its maintenance and possible repair, and ensure free access to the unit.
• Some models of boilers are already equipped with expansion tanks and then you will not need to buy it additionally.

The lion's share of modern private houses and city apartments are equipped with a water heating system. In order for it to function stably without creating any problems, it is very important to correctly approach its use and layout. We all know from school physics lessons that water tends to expand. To avoid unnecessary overload of the heating system, devices such as expansion tanks are used. Today we will get to know them better and learn how to install them correctly.

What it is?

Not every owner of a private house or apartment knows exactly what an expansion tank is. In this case, the name of this device speaks for itself - under conditions of a fixed mass of the heat carrier in the heating circuit and pipeline, which do not differ in elasticity, with a change in the temperature of the heat carrier, the pressure level in the entire system will necessarily change. Here it is worth considering the fact that the liquid expands when heated. The moment the force becomes stronger than the strength of the flow pipe/radiator, a serious accident will occur. Its main reason in this case will be the fact that water, when its volume changes under heating conditions, becomes almost incompressible. From this property, such a definition as water hammer comes out.

The solution to such a serious problem is quite simple. It is necessary to place a special reservoir (expansion tank) in the heating system, equipped with a substance that can be easily compressed.

Under conditions of increasing water pressure and in the presence of the specified reservoir, the pressure will, of course, increase, but not very much.

Features and Specifications

As you can see, expansion tanks play one of the most important roles in the heating system. They prolong its service life and avoid many serious problems.

These items are used for the following purposes:

• play the role of a heating system that operates with the help of heat pumps and solar collectors;
• act as an autonomous heating system;
• are an independent system connected directly to the central heating, as well as a closed loop system.

Provided that the temperature of the liquid in the heating system rises by only 15 degrees, due to the expansion, the volume of the heat carrier becomes more than half a percent. The expansion capacitance is responsible for compensating for this expansion. An excess of heat carrier liquid penetrates into the tank itself. If the coolant cools down, the design of the tank squeezes out insufficient liquid back into the general system.

In the presence of a slight leakage of fluid, so that the pressure in the system does not drop too much, the tank pushes the coolant away to compensate for the losses that have occurred.

In the event that the system is not equipped with an expansion tank, the expansion of the heat carrier provokes an increase in pressure. In addition, these processes will certainly end in severe wear of the components of the entire system, and also lead to breakage and even rupture of pipes and taps.

The expansion tank has many positive characteristics that make it literally an indispensable element of a water heating system:

• thanks to this detail, there is no water pollution;
• most expansion tanks are inexpensive;
• ensure the reliability and safety of the entire system;
• avoid unnecessary heat losses;
• have the smallest amount of air in the system;
• in the technique responsible for heating, there can be any heat carrier - an expansion tank is allowed to be used in all cases;
• faucets, pipes and radiators can last much longer if an expansion tank is used.

As for the direct volume of the expansion tank, it is worth considering that it directly depends on the specific type of heat carrier. How it can be calculated, we will consider below.

To date, there are units in stores, the size of which is:

• 5 liters;
• 10 l;
• 12 l;
• 19 l;

• 24 l;
• 35 l;
• 50 l;
• 80 l;
• 100 l.

Today there are several options for such devices. They are suitable for various heating systems and differ from each other in many ways.

Only their direct purpose remains unchanged.

Device and principle of operation

And now we should consider in detail what elements the expansion tanks consist of, and how they work. First, let's find out how such an element works.

As a rule, the design of the expansion tank as a whole is placed in a stamped steel casing. It has the shape of a cylinder. A little less often there are cases in the form of a kind of "pills". Typically, high-quality metals coated with an anti-corrosion protective compound are used for the production of these elements. The outer side of the tanks is covered with enamel.

For heating, expansion tanks with a red body are used. There are also blue options, but usually this color is worn by water batteries, which are integral parts of the water supply system.

They are not designed for high temperature parameters, and all their elements are subject to very high sanitary requirements.

On one side of the tank there is a threaded pipe. It is required to enable insertion into the heating system. There are times when the package also includes items such as fittings. They greatly simplify installation work.

On the other hand, there is a special nipple valve. This element serves to form the desired pressure level in the inside of the air chamber.

In the inner cavity, the expansion tank is divided by a membrane into 2 separate parts. Closer to the branch pipe there is a chamber designed for the heat carrier, and on the opposite side there is an air chamber. Typically, tank membranes are made of a very flexible material that has minimal diffusion values.

This part is given a special shape, which is responsible for uniform deformation in the event of a change in pressure values ​​in the chambers.

The principle of operation of the expansion tank in the heating system is very simple and straightforward. Let's analyze it in detail.

• In the initial state, at the moment the tank is connected to the system and it is filled with a heat carrier, a specific volume of water passes through the pipe into the water compartment. The pressure indicator in both compartments is gradually equalized. Further, such an uncomplicated system becomes static.
• With an increase in the temperature value, a direct expansion of the heat carrier in volumes in the heating system is carried out. This process is accompanied by an increase in pressure indicators. Excess liquid is sent to the tank itself, and then pressure bends the membrane part. At this moment, the volume of the chamber for the coolant becomes larger, and the air compartment, on the contrary, decreases (at this moment, the air pressure in it increases).
• When the temperature drops and the total volume of the heat carrier decreases, excessive pressure in the air chamber causes the membrane to move back. The heat carrier at this time returns back to the pipeline.

If the pressure parameters in the heating system reach critical levels, the valve should start, which belongs to the "safety group". In such a situation, he will be responsible for the release of excess fluid. Certain models of expansion tanks have their own individual safety valve.

Of course, it should be borne in mind that the design of the tank mainly depends on the variety of the specific model purchased. For example, they are non-separable or with the possibility of replacing the membrane element. Included with such products may be parts such as clamps for wall mounting or special stands - small legs with which it is easier to place the outdoor unit on a flat plane.

Expansion tanks with a membrane-diaphragm are usually non-separable. In many cases, they contain a balloon membrane part - it is made from pliable and elastic raw materials. At its core, this membrane is a conventional water chamber. As pressure increases, it expands and increases in volume. Such types of tanks are usually supplemented with a collapsible flange, which makes it possible to independently change the membrane if it breaks.

This fact does not affect the principle of operation.

Kinds

Do not think that all expansion tanks have identical designs and performance characteristics. In fact, there are several varieties of such units. Each of them has certain distinctive features and structural features. Let's get to know them better.

Depending on the specific mode of operation, tanks are divided into:

• heating tanks of open type;
• closed expansion vessels.

Not the most popular are open options for expansion tanks. These units are installed in systems in which fluid circulation is not carried out in forced mode (that is, without using a pump)

The open expansion tank has a lid that opens effortlessly when water needs to be added.

The main disadvantage of such a unit is that the coolant in it is associated with oxygen, and this provokes the appearance of corrosion in the heating system. If there is not sufficient tightness in the open tank, then the water evaporates many times faster, so it has to be constantly topped up. According to experts, it is necessary to mount such a unit at the highest section of the heating system. It should be noted that such work is not always available.

A closed (or membrane) expander is fixed in a system where the movement of the heat carrier occurs forcibly - using a pump. A closed vessel is usually made in the form of a steel tank (it does not have a lid). It is equipped with a partition inside in the form of a rubber membrane. One half in such a model is needed to fill it with a heat carrier, and the second is a place for air and nitrogen.

These containers are treated with powder paint in order to insure against damage to the walls of the case under the influence of high temperature indicators.

One of the sides of the tank itself is attached directly to the system using a fitting or flange. The opposite side is designed to pump air. The pressure indicator in the closed type model makes it possible to automatically change the supply of heat carrier to the system and the tank itself.

Closed tanks are divided into:

• interchangeable;
• non-replaceable.

So, tanks of a replaceable type have a higher cost, but they have significant advantages, which include:

• the ability to change the membrane if it has been damaged or torn;
• the ability to save on pipes, since there is no need to mount a closed tank in the upper part of the heating system;
• replaceable options are responsible for minimal heat loss;
• since the coolant does not “contact” with oxygen in any way, the pipes and the entire system as a whole are not subject to corrosion;
• the membrane can be located both vertically and horizontally;
• in this case, there is no connection with the wall inside the metal tank;
• membranes can be replaced very easily and quickly (this is done through the flange).

Non-replaceable varieties of containers are cheaper, but they cannot change the membrane if necessary. This element in the expander is installed as tightly as possible and is firmly pressed against the inner walls of the tank. Damage or rupture of the membrane in this case can only occur if the system was started incorrectly (the pressure rises too quickly and goes beyond the normal range).

Depending on the type of membrane part, expansion tanks are divided into models with:

• balloon membrane;
• diaphragmatic membrane.

Thus, a dilator with a balloon membrane is very durable and reliable. In addition, it has an impressive volume. At the same time, the heat carrier does not come into contact with the walls of the tank in any way, so the appearance of rust on such products is excluded.

The flat expansion heating tank is equipped with a dividing wall made in the form of a diaphragm.

If it suddenly gets damaged, then it will be possible to change it without much effort.

materials

In the manufacture of expansion tanks, various materials are used, but models with a steel case are considered the most common.

Currently, many people, in an effort to save money, design such units on their own. To do this, they often use sheet materials, which are subsequently assembled into a single structure by welding. Also, for the manufacture of an expansion tank, you can use the most unexpected items, for example, plastic barrels and canisters, or old gas cylinders. The use of such materials significantly reduces the cost of creating an expansion tank. Despite such a large selection of suitable raw materials, experts still recommend turning to stainless steel if you plan to assemble the tank yourself.

As for the baffle in such units, here most manufacturers use high quality rubber, synthetic rubber, natural butyl rubber raw materials or EPDM. Membrane elements for such units are made from various materials, which, in the course of use, seamlessly tolerate a wide variety of temperature ranges.

If we consider specific cases, then:

• for tanks up to 2 thousand liters, EPDM DIN 4807 marking membranes are most often used;
• tanks with a volume exceeding the above mark are equipped with BUTYL brand membrane elements.

How to choose?

The selection of an expansion tank must be approached very responsibly, since this product plays one of the most important roles in water heating systems.

Let's highlight a few simple tips that will allow the buyer to choose the right model of good quality.

• Experts recommend opting for membrane or closed-type containers. Despite the fact that these types of tanks are usually expensive, the heating system in which they are available can work for a very long time. This is due to the fact that in this design, the coolant and oxygen do not "meet" each other. But this is only advice - the choice, one way or another, remains with the owner of the home.
• Always pay special attention to the material from which the rubber baffle is made in closed models.

The raw materials that are usually used for their manufacture were listed above.

• If you are going to use the tank in conjunction with a central heating system, then the rubber of the membrane should be distinguished by increased strength characteristics and resistance to high temperature values. This is due to the fact that central heating in most cases does not involve significant pressure drops, but the temperature will still be quite high.
• A tank with a membrane characterized by increased elasticity can be safely bought for a private heating system, since sudden pressure surges are common for this type of heating.
• In order to use the expander not only in the heating system, but also in the system responsible for the water supply, the rubber from which the membrane is made must be food grade. This is necessary so as not to detract from the positive qualities of water.

• When choosing between non-replaceable and replaceable types of membranes, it is recommended to choose the first ones, because in case of damage to a non-replaceable part, you will have to change the entire unit instead of one element.
• Before purchasing an expansion tank, it is recommended that you carefully read its technical characteristics. Ask the seller for all the necessary quality certificates. If the goods do not have any or they do not want to present them to you, it is better to refuse the purchase.
• Do not forget to issue a warranty card.
• Please note that one of the most important parameters that you should pay attention to when choosing a tank is its resistance to diffusion, temperature fluctuations. In addition, all elements of the unit (from the body to the membrane) must be made of high quality materials.

Where to put?

If there is forced circulation in the system, then the pressure at the connection site of the device will be equal to the static pressure at this point and at a given temperature regime (note that this rule only works if there is one membrane element). If we assume that it changes, then as a result it will turn out that in a closed system a liquid that has come from nowhere is formed, which is fundamentally wrong.

An open heating system is a container of complex configuration with special convection currents. Absolutely all nodes must guarantee the fastest possible rise of the hot heat carrier to the top point. In addition, they must ensure gravity discharge into the boiler with the involvement of radiators. Also, the design of such a system should not interfere with the passage of air bubbles to the top point.

Based on the above features, one conclusion should be drawn - the expansion tank must be fixed in the upper plane of the single-pipe system (usually on top of the accelerating manifold).

Calculation

To determine the volume of the expander, you can rely on several different methods. To do this, it is advised to contact the masters in special bureaus. As a rule, to carry out all the necessary calculations, they use special programs that allow them to take into account all the features and nuances that affect the operation of the heating system. However, it should be noted that the services of such specialists in most cases are expensive.

You can also calculate the volume of the tank yourself. To do this, use the generally accepted formula. In this case, you need to be as careful as possible, since even a small mistake can lead to incorrect values. When calculating, it is important to take into account absolutely all the nuances: the volume of the heating system, and the specific type of heat carrier, and even its physical properties.

In the above formula:

• C is the total volume of the heat carrier in the system;
• Pa min - indicator of the initial absolute pressure in the tank;
• Pa max is the largest pressure parameter that can take place in the unit.

If you are afraid to make a mistake or you do not have time to carry out all the required calculations, then you should turn to the help of special online calculators. True, in this case it is recommended to double-check the results obtained on several sites so as not to encounter incorrect operation of one or another portal.

Some people make it easier - they estimate the necessary parameters by eye. In this case, the specific capacity of the heating system is equated to 15 l / kW. The result will be approximate values. But keep in mind that it is allowed to refer to this method only in the process of a feasibility study.

Before purchasing a tank, of course, only accurate calculations will be required.

DIY installation

Before proceeding with the installation of the expander, it is important to prepare:

• be sure to read the instructions before starting work;
• carry out all the necessary calculations of temperatures and pressure indicators (usually all these data are indicated in special reference books on the standards for the use of units);
• prepare tools such as a wrench, a key for installing plastic pipes;
• if the tank has a large capacity, then you will also need to buy brackets - they will be useful for mounting.

When installing and connecting such units, you should rely on some recommendations from experts:

• position the unit in such a way as to guarantee free access to it in the future;
• provide for the likely dismantling of pipes in the future;
• make sure that the diameter of the connecting pipe converges with the connected water supply;
• correctly install the necessary temperature sensors;
• calculate the connection of the shut-off valves.

Now you can proceed to the direct installation of the tank. It should be hung near the inlet of the flowing heat carrier in the direction of the heating unit.

Mark the areas for fastening. Drill the required number of holes needed to secure the bracket. To do this, it should be attached to the wall, and mark all areas of the connection. Having made all the necessary holes, you need to install anchor bolts in them, then hang the bracket and make sure that the fastening is reliable. If everything is done with high quality, then you can install the tank itself, and then fix it with clamps.

Please note that such equipment cannot be installed in sub-zero temperatures. In addition, it is important to ensure that after completion installation work the air valve was in an accessible area. This is necessary so that the owners have the opportunity to set the desired level of pressure.

Absolutely all mechanisms that require adjustment should be in the public domain, and pipes should be located so that they do not create stress on the equipment.

As for such an element as a pressure reducer, it must be installed after connecting the measuring meter so as not to encounter serious loads directed to the tank. Attach this valve to the front of the flow pipe.

After that, you need to configure the installed expansion tank. First you need to set the required pressure level. This must be done by pumping air. The pressure gauge will tell you when to stop. After that, water is pumped using a pump, the pressure is equalized, and the membrane part is brought to a floating state. Then the tank can be considered ready for use. You may need to turn on the system and make sure it works.

As you can see, the scheme for mounting and connecting the expansion tank is quite simple. Anyone can handle these events.

The main thing is to rely on the instructions and be extremely careful at each stage.

Frequent problems

Expansion tanks, like any other heating units, are subject to a number of specific problems. Let's get acquainted with them.

most frequent breakdown such aggregates is a rupture of the membrane part. As a rule, this happens due to too high pressure (above normal) or uneven loads. Please note that replaceable elements are torn much more often than compressed ones, since stronger materials are used for the latter, because they can be changed at any convenient time.

The problem of a damaged membrane can lead to many unpleasant consequences. For example, because of this, water often flows from the air valve.

If the membrane is not replaced in time, its rupture will lead to the fact that over time the tank will simply fail. This is due to the fact that the liquid enters the inner surface of the tank, after which it can become rusty and become unusable.

Please note that the old membrane should be replaced with the same part. It is advisable to contact a specialized service center for this.

Also, users quite often encounter damage to the tank body. If such a problem has happened to your equipment, it is better for you to seek help from a specialist. Do not take on the repair of damaged body elements on your own, especially if you have never encountered such work before.

There are also cases when the expander boils. Most often, this problem occurs homemade designs open type. The main essence of this problem is the lack of circulation speed (or its complete absence).

Here are the main reasons for such breakdowns.

• Reduced piping diameter. The main single-pipe heating circuit is usually installed with a pipe that is at least thinner than DN 32.
• No slope. After the heating boiler, you need to make a so-called accelerating collector. To do this, the pipe must be raised to the upper section of the circuit, where the expander is just installed. The rest of the circuit should be laid with a downward slope.

Many users are wondering how to fix such a serious problem without proceeding with the complete dismantling and reinstallation of the heating system. The answer is simple - you need to install a circulation pump. This detail functions remarkably in many systems (especially open type). The pump must be placed on the return line directly in front of the boiler.

Another problem with expansion tanks is air blockage in the heating system circuit. In order not to collide with it, you need to monitor the volume of water.

If you do not replenish it, the resulting fumes will lead to the above problems.

How to replace?

From the above information, we can conclude that the main problem with expansion tanks is a damaged membrane. Many users face this problem. Experts recommend replacing these elements in special service centers, but it is possible to carry out such work on your own.

This is done in the following way.

• First you need to disconnect the tank from the heating system.
• Next, you need to reduce (reset) the pressure indicators of the gas cavity using a nipple on top of the unit.
• Remove the diaphragm flange, which is located next to the nozzle, to connect the pipeline. Unscrewing the nut on top of the body, you need to release the holder of the membrane part.
• Remove the membrane part from the cavity at the bottom of the housing.
• Next, you need to study the surface of the insides of the hull structure. There should be no dirt or rust. If there are any, then they must be removed and the surface washed with water. Then you need to dry the case.

• It is important to take into account the fact that the membrane is not resistant to oil. For this reason, products containing oil must not be used to ensure that the internals of the unit are protected from corrosion.
• Install the membrane element holder in the cavity located at the top of the membrane itself, if such fasteners should be present in the design of a particular device.
• Screw the bolt into the retaining element, put the membrane into the housing. The holder must be inserted into the cavity located at the bottom of the housing.
• The retaining part must be fastened with a nut.
• Set the preliminary air pressure values ​​in the expander. Check the structure for leaks, after which you need to connect the expander directly to the heating system.

Please note that if the safety valve operates with a high frequency, then this may indicate that you made a mistake with the selected volume. You may have made the necessary calculations incorrectly.

In order for the piping to be installed in accordance with all the rules, close attention must be paid to the main components of the system: the area where the heat carrier enters directly into the tank, as well as the place where it leaves.

To ensure that water never boils in the expansion tank, choose contour pipes that have the correct diameter. In addition, it is important to take care of the slope of the contours.

Please note that if the vacuum expander will not function for a long time, then it must be kept only in a dry space, having previously drained the liquid from it.

At least once every six months, check the unit for damage and defects. These include dents, rust, or signs of leakage. If you suddenly discovered such things, then you will need to eliminate the cause of their occurrence as soon as possible.

Remember that it is necessary to install expansion tanks only in accordance with the drawn up plan and scheme.

If you doubt your abilities, then it is better not to take risks - contact the experts.

Due to the ease of installation, low cost and sufficient efficiency, an open heating system continues to be in demand. Having dealt with the principle of operation, equipment and installation rules, you can organize the heat supply at home on your own.

We will tell you how to draw up a workable open-type heating scheme. We will show you how to build a system, strictly following the technological requirements and standards when choosing and connecting elements. Based on our recommendations, you will build a trouble-free effective circuit.

For independent craftsmen, we suggest that you familiarize yourself with the assembly options that have been proven in practice. The information submitted for consideration has been supplemented useful diagrams, photo collections, video instructions.

1. The circuit with a built-in pump is volatile. So that the heating of the room does not stop when the electricity is turned off, the pumping equipment is placed on the bypass.
2. The pump is installed before entering the boiler on the return pipe. The distance to the boiler is 1.5 m.
3. When installing the pump, the direction of water movement is taken into account.

Two shut-off valves and a bypass elbow with a circulation pump are mounted on the return. In the presence of current in the network, the taps are closed - the movement of the coolant is carried out through the pump. If there is no voltage, then the valves must be opened - the system will be rebuilt to natural circulation.

You need to think about how to install an expansion tank in the heating system of a private house in advance, before purchasing it. This makes it easier to determine the location of the tank and the method of laying the pipeline for connection to the heating network. But situations are different, it is impossible to foresee everything in advance. It is worth studying the essence of the issue a little, and you yourself will be able to figure out where to install and how to properly connect the expansion tank, including with your own hands.

The installation location of the tank depends on the type of heating system and the purpose of the tank itself. The question is not what the expansion tank is for, but where it should compensate for the expansion of water. That is, in the heating network of a private house there may be not one such vessel, but several. Here is a list of functions that are assigned to tanks installed in different places:

• compensation of thermal expansion of water in open-type heating systems;
• the same for closed systems;
• serve as an addition to the regular expansion tank of the gas boiler;
• perceive the increasing volume of water in the hot water supply network.

An open tank, where the coolant is in contact with atmospheric air, is the hallmark of an open heating system. In this case, the expansion tank is installed at the highest point in the heating network of a private house. Often such systems are made gravity flow with increased pipeline diameters and a large amount of coolant. The capacity of the tank should be appropriate and be about 10% of the total water volume. Where, if not in the attic, to put such an overall tank.

For reference. In old one-story houses, you can often see small expansion tanks for an open heating system installed in the kitchen next to a floor-standing gas boiler. This is also correct, the container under the ceiling is easier to control. True, it does not look too good in the interior. To put it mildly.

Alternative homemade tanks

Heating systems of a closed type are distinguished by the fact that a membrane expansion tank for water can be placed anywhere. But still, the best installation option is in the boiler room, next to the rest of the equipment. Another place where it is sometimes necessary to install a closed expansion tank for heating is the kitchen in a small house, since the heat source itself is located there.

About additional containers

Following new trends, many manufacturers complete their heat generators with built-in tanks that perceive the volume of coolant that increases when heated. These vessels cannot correspond to all existing heating schemes, sometimes their capacity is not enough. In order for the coolant pressure to be within normal limits during heating, an additional expansion tank for the wall-mounted boiler is installed in accordance with the calculation.

For example, you converted an open gravity system to a closed one without changing the lines. The new heating unit was selected according to the heat load. Whatever the capacity in it, it will not be enough for such an amount of water. Another example is heating with underfloor heating in all rooms of a two- or three-story house plus a radiator network. Here, the volume of coolant will also come out impressive, a small tank will not cope with its increase and the pressure can rise greatly. That's why you need a second expansion tank for the boiler.

Note. The second tank to help the boiler is also a closed membrane tank, located in the furnace room.

When the hot water supply at home is provided by an indirect heating boiler, the question also arises - what to do with the water expanding when heated. One option is to install a relief valve, as is done on electric water heaters. But the indirect heating boiler is much larger in size and through the valve it will lose too much hot water. Where is the best place to choose and install an expansion tank for a boiler.

For reference. In buffer tanks (heat accumulators) of some manufacturers, it is also possible to connect a compensating tank. Moreover, experts recommend putting it even on large-capacity electric boilers, which is shown in the video:

How to put the tank

When installing an open tank in the attic, a number of rules should be observed:

1. The container must stand directly above the boiler and be connected to it by a vertical riser of the supply line.
2. The body of the product must be carefully insulated so as not to waste heat on heating a cold attic.
3. It is imperative to organize an emergency overflow so that in an emergency situation hot water does not flood the ceiling.
4. To simplify level control and make-up, it is recommended to bring 2 additional pipelines into the boiler room, as shown in the tank connection diagram:

Note. The emergency overflow pipe is usually directed to the sewer network. But some homeowners, in order to simplify the task, take it out through the roof straight to the street.

The installation of a membrane-type expansion tank also has its own characteristics. Given the way this product works, it can be placed vertically or horizontally in any position. It is customary to fasten small containers to the wall with a clamp or hang them from a special bracket, large ones - just put them on the floor. There is one point: the performance of a membrane tank does not depend on its orientation in space, which cannot be said about the service life.

A vessel with a closed type will last longer if it is mounted vertically with the air chamber up. The fact is that sooner or later the membrane will exhaust its resource, which will cause cracks to appear in it. The internal structure of the tank is such that, when placed horizontally, air from its half will quickly penetrate through the cracks into the coolant, and that one will take its place. We'll have to urgently put a new expansion tank for heating. The same result will quickly appear when the container is hung upside down on the bracket.

In a normal vertical position, air from the upper part will not rush to penetrate through the cracks into the lower part, just as the coolant will reluctantly go up. Until the size and number of cracks increase to a critical level, the heating will work properly. This process sometimes takes a long time, you will not notice the problem immediately. But no matter how you place the vessel, you should adhere to the following recommendations:

1. The product must be placed in the boiler room in such a way that it is convenient to service it. Do not install floor-standing units close to a wall.
2. When wall-mounting the expansion tank of the heating system, do not place it too high, so that when servicing it is not necessary to reach the shut-off valve or air spool.
3. The load from the supply pipelines and shut-off valves should not fall on the tank branch pipe. Fasten the pipes together with the taps separately, this will facilitate the replacement of the tank in case of breakage.
4. It is not allowed to lay the supply pipe on the floor through the passage or hang it at head height.

How to beautifully place the equipment in the boiler room

Connection methods

It is hydraulically correct to connect the device at a point located on the return line in front of the boiler and circulation pump, which allows the latter to work optimally. Although the tank can also be connected to the supply line, then the membrane will last less due to contact with a higher temperature coolant. The second moment: when working on the supply of a solid fuel boiler in an emergency, steam can penetrate into the tank. Air and steam are compressible media, and in this case, the rubber "pear" will no longer compensate for the expansion of water.

The correct connection of the expansion tank to the heating system is always carried out through a shut-off ball valve with an American. Thanks to this, the element can be taken out of service at any time and quickly changed without waiting for the coolant to cool. If you install a tee and a second tap on the connection, as shown in the connection diagram, then the container can be emptied beforehand:

Note. When installing and connecting an expansion tank for a boiler, the same rules should be followed. Only the tank itself should be designed for pressure in the water supply network, and not for heating, which is described in detail and intelligibly in the video of our expert:

How to check and pump up an expansion tank

Before connecting and filling the tank with coolant, it is necessary to check the pressure in the air chamber of the tank for compliance with the pressure in the heating network. To do this, a plastic plug is unscrewed or removed from the side of the air compartment, and under it there is a conventional spool familiar to you from car cameras. You measure the pressure with a pressure gauge and adjust it to fit your system, pumping it up with a pump or lowering it by pressing the spool rod.

For example, the design pressure in the network after filling should be 1.3 bar. Then in the air compartment of the expansion tank it is necessary to make 1 Bar, that is, 0.2 Bar less. The trick is that the rubber "pear" of the tank is pressed from the side of the water. Otherwise, when cooling, the compressed coolant will begin to draw air through automatic air vents, which is unacceptable. After setting, open the tap, fill the entire system with coolant and calmly start the boiler.

Note. Some manufacturers indicate the factory pressure in the air compartment on the packaging of their products. On it, you can choose a suitable tank and not bother with pumping.

Conclusion

All work related to the installation, connection and configuration of the expansion tank is not highly qualified and can be done by hand. Moreover, during operation, it is better for you to be able to do the pressure check yourself. Its decrease or jumps are the first reason why the automatic gas boiler turns off the burner. Therefore, in such cases, the first thing to do is to check the air chamber of the tank with a pressure gauge if there are no serious coolant leaks in other places.

The heating system, being a complex engineering structure, consists of many elements with different functional purposes. An 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 heat-carrying liquid. Given that the liquid is a practically incompressible medium, and the heating system is hermetic, this physical phenomenon can lead to the destruction of the boiler or pipelines. The problem could be solved by installing a simple valve that can bleed the excess volume of hot coolant into the external environment, if not for one important factor.

During cooling, the liquid contracts and air enters the place of the discharged coolant into the heating circuit. Air locks are a headache for any heating system, because of them, circulation in the network becomes impossible. Therefore, it is necessary. The constant addition of a new coolant to the system is very expensive, heating cold water is much more expensive than heating the heat-carrying fluid that came to the boiler through the return pipeline.

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

Types of heating systems

There are two schemes for the building's heating networks -. An open (gravity-flowing) heating system is used in centralized heating networks and allows you to directly take water for hot water 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 air separation from the system, as it has the ability to communicate with the outside atmosphere.

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

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, while air is removed from the circuit through special taps (valves) installed on the heaters and at the top of the system pipelines.

Device and principle of operation

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

The membranes are of the following types:

The gas pressure is adjusted for each system individually, which is described by the instructions attached to such devices as an expansion tank for heating a closed type. Some manufacturers in the design of their expansion tanks provide for the possibility of replacing the membrane. This approach somewhat increases the initial cost of the device, but later, 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 affect the efficiency of the devices, it should only be noted that a slightly larger volume of heat-carrying liquid can fit into a closed-type balloon expansion tank for heating.

Their principle of operation is also the same - with an increase in water pressure in the network due to expansion when heated, the membrane stretches, compressing the gas on the other side and allowing excess coolant to enter the tank. During cooling and, accordingly, a drop in pressure in the network, the process takes place in the reverse order. Thus, the regulation of constant pressure in the network occurs automatically.

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

Calculation of expansion tanks

To calculate an expansion tank for closed-type heating, you must first calculate overall volume a system consisting of the volumes of the pipelines of the circuit, the heating boiler and heating devices. 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 ​​\u200b\u200bthe pipes by their length. If there are pipelines of different diameters in the system, then their volumes should be determined separately, and then added up.

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

Vc is the 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 - indicator of the efficiency of the membrane block. Usually it is indicated by the manufacturer or it can be determined by the formula: D \u003d (Rm - Rn) / (Rm +1), where:

Pm - the maximum possible pressure in the heating network, usually it is equal to the maximum working pressure of the safety valve (for private houses it rarely exceeds 2.5 - 3 atm.)
Рн is the pressure of the initial pumping of the air chamber of the expansion tank, taken as 0.5 atm. for every 5 meters of the height of the heating 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, with a volume of heat-carrying fluid in the system of 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 the volume is very approximate and may result in unnecessary costs for the purchase of a larger expansion tank.

Currently, online calculators for calculating expansion tanks have appeared on the Internet. In the case of using such services for the selection of equipment, it is necessary to carry out calculations on at least three sites in order to determine how correct the algorithm for calculating one or another Internet calculator is.

Manufacturers and prices

At present, 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 in the financial capabilities of the buyer. There is a wide choice of models of devices of both domestic and foreign manufacturers on the market. 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 the main competitors, then it is better to refuse such an acquisition.

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 products, for a high-quality expansion tank for heating, the price will not have a significant difference of about two - three times. Conscientious manufacturers use approximately the same materials and the difference in price of models similar in parameters of about 10-15% is determined only by the location of production and pricing policy sellers.

Domestic manufacturers have proven themselves well in this market segment. By installing modern technological lines in their production, they have achieved the release of products that, in their parameters, are not inferior to the best world 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, subject to the instructions, it is possible to install it yourself. If the master still has any doubts about his knowledge, then it is best to turn to professionals to ensure the stable operation of the heating network and eliminate possible malfunctions.

Let's try to figure out why you need and how to install an expansion tank in the heating system.

We will consider options for an open system with natural circulation and for a closed heating system using a circulation pump. Let's start, however, with definitions.

Our task is to choose a tank that suits us in terms of volume and mount it correctly.

general information

What is an expansion tank and what is it for?

Its very name gives a hint: for an extension. With a fixed mass of the coolant in the heating circuit and pipes, the elasticity of which tends to zero, with a change in the temperature of the coolant, the pressure in the system will inevitably change. Thermal expansion, remember? Water or any other coolant, when heated, expands.

Once the force exceeds the tensile strength of the pipe or radiator... Boom!

The reason for a possible accident is that water, changing its volume when heated, remains practically incompressible. Hence the concept of water hammer: there are no elastic interactions in a liquid medium, to put it simply.

The obvious solution is to create in the system a reservoir with an easily compressible substance - air. With an increase in the volume of water in the presence of such a reservoir, the pressure will increase slightly.

Useful: so that oxygen from the air tank does not contribute to the corrosion of pipes, dissolving in water, in tanks for closed systems it is separated from the water by a rubber membrane.

However, we have described only one of the functions of the expansion tank.

In addition to private houses with fixed volumes and a circuit and a coolant in it, an expansion tank can be found:

• In open systems in contact with atmospheric air;
• In central heating systems with top filling. There, the expansion tank is located in the attic and is connected directly to the supply pipeline of the house heating system.

In both cases described, the installation of an expansion heating tank is needed in order to get rid of air locks. The difference between the two threads in the case of central heating is only about two meters. B is even less.

Clarification: the author can still hear the exclamations of more or less knowledgeable people who, at the height of the heating season, saw a 10 times greater drop in the elevator unit.
Typically 6 kgf / cm2 on the supply pipeline and 4 - on the return (1 atmosphere of overpressure corresponds to a water column of 10 meters).
Do not confuse warm with soft: it is not water from the supply that enters the heating system, but a mixture.
The elevator recirculates the return water in the heating system by injecting a jet of hotter water with a higher pressure from the supply pipeline into it through a nozzle.
As a result, as stated, the difference between the mixture and the return flow does not exceed 2 meters, or 0.2 kgf / cm2.

With such a difference, the water pressure will not be able to squeeze out the air plug from the upper part of the heating system. Hence a simple solution: put some kind of container for collecting air where it will accumulate, and bleed it when the system is started. In the case of an open system, of course, no active actions are needed.

All the air in the system will be pushed up and into the expansion tank. In an open system, it will immediately reunite with the atmosphere. In a closed one, it will wait until the owner of the house opens the air valve.

How and where is the expansion tank placed

So, we are going to design and assemble a heating system with our own hands. If she also earns - our joy will not be the limit. Are there any instructions for installing the expansion tank?

open system

In this case, simple common sense will prompt the answer.

An open heating system is, in essence, one large vessel of complex shape with specific convection currents in it.

The installation of the boiler and heating appliances in it, as well as the installation of pipelines, must ensure two things:

1. Rapid rise of the water heated by the boiler to the upper point of the heating system and its discharge through the heating devices by gravity;
2. The unhindered movement of air bubbles to wherever they rush in any vessel with any liquid. Up.

The conclusions are clear:

1. The installation of a heating expansion tank in an open system is always carried out at its highest point.
   Most often - at the top of the accelerating manifold of a single-pipe system. In the case of top filling houses (although you hardly have to design them) - at the top filling point in the attic.
2. The tank itself for an open system does not need shutoff valves, a rubber membrane, and even a lid (except to protect it from debris).
   This is a simple water tank open on top, into which you can always add a bucket of water to replace the evaporated one.
   The price of such a product is equal to the cost of several welding electrodes and a square meter of steel sheet 3-4 mm thick.

closed system

Here, both the choice of the tank and its installation will have to be taken quite seriously.

Let's collect and systematize the basic information available on thematic resources.

• The installation of the expansion tank of the heating system is optimal in the place where the water flow is closest to laminar, where there is a minimum of turbulence in the heating system.
  The most obvious solution is to place it in a straight dispensing area in front of the circulation pump.
  At the same time, the height relative to the floor or the boiler does not matter: the purpose of the tank is to compensate for thermal expansion and dampen water hammer, and we perfectly bleed air through air valves.

A typical tank setup. Its location in a single-pipe system will be the same - in front of the pump along the water course.

• Tanks in the factory are sometimes supplied with a safety valve that relieves excess pressure.
  However, it is better to play it safe and make sure that your product has it. If not, buy and mount next to the tank.
• Electric and gas boilers with electronic thermostats often come with built-in thermostats. Before you go shopping, make sure you need them.
• The fundamental difference between membrane expansion tanks and those used in open systems is their orientation in space.
  Ideally, the coolant should enter the tank from above. This subtlety of installation is designed to completely remove air from the compartment of the tank that is intended for liquid.
• The minimum volume of the expansion tank for a water heating system is taken approximately equal to 1/10 of the volume of the coolant in the system. More is acceptable. Less is dangerous. The volume of water in the heating system can be roughly calculated based on the heat output of the boiler: as a rule, 15 liters of coolant per kilowatt are taken.
• A pressure gauge mounted next to the expansion tank and the make-up valve (connecting the heating to the water supply) can provide you with an invaluable service. The situation with a stuck spool of the safety valve, alas, is not so rare.
• If the valve releases pressure too often, this is a clear sign that you miscalculated with the volume of the expansion tank. It is not necessary to change it at all. It is enough to purchase another one and connect it in parallel.
• Water has a relatively low coefficient of thermal expansion. If you switch from it to a non-freezing coolant (for example, ethylene glycol), you will again need to increase the volume of the expansion tank or install an additional one.

Conclusion

As usual, additional information on the selection and installation of expansion tanks in systems different types you will find in the video at the end of the article. Warm winters!

Installing an expansion tank in the heating system ensures its performance and reliability. Devices of this type are used in open and closed systems, with gravity or forced circulation of the coolant.

Expansion tank functions

What is the purpose of the expansion tank? The heating system is filled with a fixed amount of fluid (water or antifreeze) that is prone to thermal expansion. This means that an increase in the temperature of the coolant inevitably leads to an increase in pressure in the system. Since pipes, radiators and other elements of an engineering structure are inelastic, increased pressure will lead to depressurization of the system - in the very weak spot a breakthrough will occur.

Water is characterized by low compressibility, so a special device is built into the system - a membrane or open tank. Its function is that when the pressure rises, air will be compressed. This makes it possible to provide protection against water hammer. The installed expansion tank protects the system from excessive pressure increase.

The main task is to perform a reliable installation of the tank

Membrane tanks are designed for a closed-type heating system - they are a container with an elastic waterproof membrane inside, which divides the internal volume into two parts. The membrane is needed so that air does not come into contact with the coolant. Otherwise, airing the network and increasing the risk of corrosion of the steel elements of the system cannot be avoided.

In an open type system, the tank communicates with the atmosphere, due to which air is bled from the pipes. For this reason, the installation location of an open tank is strictly regulated - it must be located at the highest point in the system.

How to connect an expansion tank

How to make a reliable connection of the expansion tank in an open system!? An open-type heating system is characterized by the fact that the movement of the coolant in it is ensured by convection.

The principle of operation is as follows: the coolant heated by the boiler unit is delivered directly to the highest point of the system, as a result of which it enters the heating radiators by gravity and, having cooled down, returns to the boiler through the “return” pipeline. There is always dissolved oxygen in water, which is released during convection, which means that air bubbles tend to rise up.

When considering this diagram, it becomes obvious that the only possible location for the expansion tank is the top point of the system. For a single-pipe system, this is the upper part of the accelerating manifold.

Connection diagram of a membrane tank in an open-type heating system

As a tank, you can use any container of a suitable size made of a heat-resistant material. A cover (not sealed) is needed for it only to protect against debris entering the system. If a small metal barrel was not at hand, the tank is welded from sheet steel 3-4 mm thick.

The tank must be installed in compliance with certain rules, in particular:

• the tank must be placed above the boiler unit and connected by a vertical riser through which heated water is supplied;
• it is recommended to insulate the body of the tank to reduce heat loss, especially if the tank is located in an uninsulated attic at home.

Over time, the water from the tank evaporates and periodically it needs to be topped up. This can be done using an ordinary bucket. If the tank is installed in the attic, which is difficult to reach, a water supply pipe is brought to the tank installation site, and an emergency overflow is organized to avoid flooding the house with hot water in case of an emergency. The emergency overflow pipe is usually connected to the sewer network, but owners of private houses often simplify the task by bringing it outside through a wall or roof.

Expansion tank in a closed heating system

Equipment for the heating system is selected at the stage of its design, taking into account the requirements for the performance of the boiler unit, the length of the pipelines and the volume of the heat carrier involved. A scheme is being developed that indicates the installation locations of all elements of the system, including the expansion tank. In a closed type heating system, a membrane device must be used.

Expander in a closed heating system

When linking a project to an existing boiler house, it is important to take into account the following points:

• The tank should be placed in such a way as to provide normal access for installation and further maintenance. Floor models are not recommended to be installed close to the wall.
• If the unit is mounted on a wall, it is advisable to place it at such a level that you can easily reach the air spool and shut-off valve. Usually the tank is placed under the ceiling of the room, only if it is not possible to mount it at a convenient height.
• The supply pipe must not be placed on the floor across the passage or suspended at human height.
• Pipelines connected to the expansion tank must be fixed to the wall. It is important to avoid a situation where the load from them and from the valves falls on the tank nozzles. Fixing pipes and taps separately makes it easy to replace the expansion device in case of failure.

At the stage of equipment selection, it is necessary to calculate the required volume of the expansion tank. The minimum value of this parameter is 1/10 of the total volume of fluid circulating in the system. It is acceptable to use a larger tank. But an insufficiently capacious tank can become a source of problems, as it is not able to compensate for the increased pressure in the system.

Expansion tank placement rules

For approximate calculations of the volume of coolant in the system, the thermal power of the boiler unit can be taken as a basis. On average, 15 liters of liquid per kilowatt are used. Accurate calculations are made taking into account the length of pipelines, the volume of radiators, etc.

Important! Many models of gas and electric boilers are mini-boiler rooms, that is, they are immediately equipped with a pump for forced circulation of the coolant, as well as an expansion tank. A separate tank does not need to be purchased if the parameters of the built-in membrane tank are sufficient to ensure the functionality and safety of the existing heating system.

When purchasing a membrane expansion tank, pay attention to whether the selected model has a safety valve, due to which excess pressure is automatically released. If this is not provided for by the design of the device, you should buy a safety valve separately and install it in the immediate vicinity of the tank.

Where is the best place to put the tank

The optimal place for mounting a membrane tank is a straight section of the pipeline, which is characterized by a laminar flow of water, that is, the absence or minimum number of turbulences. A good location is the spill area near the circulation pump.

Note! Installation of an expansion tank of a closed-type heating system can be carried out at any convenient height. There is no need to place it at the highest point as it functions solely as a water hammer protector. Unlike an open-type heating system, the air accumulated in the pipeline is vented using special valves - air taps.

From a hydraulic point of view, it is best to install the membrane tank on the return line so that the circulation pump is located between it and the boiler. In this case, the pumping equipment will function optimally.

Scheme of possible placement of the tank

If desired, the tank can also be placed on the supply line, this will not affect the performance of the heating system. But the membrane tank itself will last for a relatively short time, since the polymer membrane will constantly be in contact with the coolant, which has just been heated to 90 degrees, and not with water that has cooled to 45-60 degrees and returned through the pipeline.

Attention! Installing a membrane tank on the supply line is highly discouraged if the boiler is solid fuel. There is a risk that due to an emergency, the water in the boiler will begin to boil and steam will enter the tank. Water vapor, like air, is a compressible medium, due to which the membrane cannot compensate for the thermal expansion of water.

Expansion tank installation process

Now let's figure out how to install an expansion tank in the heating system. There is an important rule for connecting the device: the tank must be connected to the heating system mains using a shut-off ball valve with an American. This principle of installation makes it possible, if necessary, to block the movement of water in the system at any time, remove the faulty membrane tank and install a new one.

Otherwise, it would be necessary to wait for the coolant to cool down and dismantle part of the piping. Ideally, a tee is installed on the liner, as well as a second tap - in this case, before removing the expansion tank, it can be emptied into a substituted container.

Hanging the expander upside down, if the membrane malfunctions, the unit will fail immediately

How to correctly orient the membrane expansion tank in space? The tank is installed with the air chamber up or down, the tank is placed “on its side”. From the point of view of performance, this does not really matter, since in any case the device will perform its functions properly.

However, it is worth considering such a moment: if the air compartment is located below, then the coolant is supplied from above, and the bubbles of air dissolved in it will rise into the pipeline and be removed using an air valve. Otherwise, an air bubble will form in the "water" compartment of the membrane tank over time.

In turn, when the tank is located with the air chamber up, its service life is extended. Over time, from constant contact with hot water, the polymer membrane loses its tightness, cracks appear in it. If the air chamber is located below, then water immediately begins to seep into the air compartment, which will quickly disable the expansion tank, while air will penetrate into the coolant. When the air chamber is located on top, the diffusion of water through the cracks is many times slower, and the device is able to work much longer.

Helpful Hints:

• If next to expansion tank and a valve, thanks to which the heating system is fed from the water supply, mount a pressure gauge, it will allow you to control the pressure in the system in order to bleed the excess in time if the safety valve spool is stuck and does not work automatically.
• The frequently repeated release of pressure by the valve indicates that the capacity of the expansion tank has been selected incorrectly. Instead of changing it to a larger tank, it is enough to connect a second tank in parallel.
• Replacing the existing expansion tank with a larger one or connecting a second one will also be required if it is decided to replace the water in the system with antifreeze. This is due to the fact that non-freezing coolants have a higher coefficient of thermal expansion.

If there is no pressure gauge, the expansion tank circuit should be equipped with a safety group

Setting

Before connecting the tank and filling it with coolant, it is required to check the pressure level in the air chamber of the tank - it must correspond to the pressure in the heating system. To do this, remove or unscrew the plastic plug that closes the spool (similar to those installed in car chambers). Using a manometer, it is necessary to measure the pressure and adjust it to the indicators of the heating system. To do this, air is pumped up by the pump or vice versa, it is bled by pressing the spool rod.

Note! The tank should be set in such a way that the pressure in its air chamber is 0.2 bar less than the calculated pressure in the system filled with coolant. If the pear-shaped membrane is not pressed from the water injection side, the coolant, shrinking during cooling, will be able to draw air through.

After completing the settings, open the tap and fill the entire system with coolant. Then the boiler unit is started.

The adjustment step is not required if the factory pressure in the air compartment of the expansion vessel is correct. Manufacturers of some brands of equipment indicate the level of pressure in the tank on the packaging, which makes it possible to choose the option that will be optimal when buying.

Conclusion

You can correctly install the expansion tank, prepare a customizable membrane tank for work yourself, without the help of a specialist. The experience gained can be useful in the future if you need to quickly identify the source of problems associated with a decrease or pressure surges in the system, due to which the burner flame goes out. In such cases, it is recommended first of all to carefully inspect the system for coolant leaks and measure the pressure in the air chamber of the membrane tank.

When planning to create a water heating system in your own home, 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 ones is a fully sealed expansion tank for closed-type heating, 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

Despite the fact that recently a lot of modern devices and systems for space heating have appeared, 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.

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"? A conventional open expansion tank, if it fully copes with its functions, seems to be a simpler and more 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, you can find examples of the use of old plastic canisters.

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 the country house in winter is not used constantly, but “arrivals”, occasionally.
• In an open heating system, the expansion tank, as already mentioned, must be mounted at the highest point. Very often, an unheated attic becomes such a place. 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 disharmonize 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 open expansion tank are excluded.
• 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 battery, it allows you to connect underfloor heating circuits, convectors, and 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 is an obligatory "safety group", including instrumentation (pressure gauge, thermometer), safety valve and automatic air vent. However, this, rather, is not not a wealth, 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 (pos. 1) of a 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 blue tanks - but these are water batteries 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 - an air chamber (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 the initial position, when the tank is connected to the system and filled with 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 their own design features. 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. As the pressure increases, such a membrane stretches, 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"

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;

Vc- 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:

1. 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.

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 – Indicate the nameplate power of the heating boiler, kW, based on the intended location of the expansion tank - with fastening to the wall or with placement on the floor.

There is one more nuance. Some heating boilers have their own built-in expansion tank. This does not mean at all that it is not necessary to carry out calculations - it happens that the volume of the built-in tank is clearly not enough. In this case, you will have to purchase and install an additional one, with a working volume equal to the difference between the calculated indicators for the entire system and the parameters in the built-in tank.

And one more note. If the heating system works on the principle of forced circulation, then, even with small volumes of coolant, an expansion tank with a capacity of at least 15 liters should be installed.

Expansion tank for closed-type heating do-it-yourself installation

For a person with plumbing skills, installing an expansion tank on their own will not be difficult. The principle of its insertion into the system is shown in the diagram:

On the return pipe (pos. 1), in the area as close as possible to the entrance to the heating boiler (pos. 2), but usually in front of the circulation pump (pos. 3), a cut is made into which the tee is packed (pos. 4). The installation method can be different - it all depends on the type of pipes used - metal, polypropylene or metollaplast.

A ball valve (pos. 7) is packed on the branch pipe (pos. 6) of the expansion tank itself (pos. 5). It is necessary in order to provide the ability to turn off the expansion tank in case of need for repair or maintenance work. For the same purposes, it makes sense to place a connection with a union nut - “American” (pos. 8) between the tap and the tank. In working position, the valve must be constantly open.

From the tap there is a connecting section of the pipe (pos. 9) to the tee. Its length and configuration (number of bends or turns) of great importance do not have - but it is usually done along the shortest and most convenient path from the installation site of the tank to the return pipe.

Now let's see what needs to be done on the tank itself.

Illustration	Brief description of the operation to be performed
	The tank was taken out of the factory packaging, the necessary tools and accessories were prepared for work.
	If necessary, an adapter is packed on the threaded pipe of the expansion tank. It is important to achieve exceptionally reliable sealing of the joints. It is best to pack on tow using Unipack paste or using a special thread sealing thread (cord) impregnated with a sealing compound (as shown in the figure).
	The adapter is tightened, and you can proceed to the installation of the crane. It should be noted right away that in the example shown, a flaw was made - the master does not establish a detachable connection - "American" between the tap and the tank. That is, if it is necessary to dismantle the tank with the tap closed, this will be very difficult to do. Recommendation to all installers - do not forget about this moment.
	A thread is being wound for packing the crane, ...
	... the valve is put in place and tightened tightly. It should immediately be provided that the “lamb” is in a position convenient for use after placing the tank on the wall.
	From the tap, a transition is mounted to the pipe of the required configuration, in accordance with the drawn up scheme for the general installation of the expansion tank. In fact, this part of the work is finished.
	Now you can check the pressure in the air chamber of the expansion tank. On its opposite side there is a nipple - almost exactly the same as on car wheels. In many models, it is covered with a special plastic cap, which, if necessary, access to the valve is simply unscrewed.
	You can check the pressure with a car pressure gauge. If it exceeds the indicators that were used in the calculation of the system, then it can be bled to required level pressing on the valve stem. In case of insufficiency, you will have to pump up - an automobile pump is quite suitable for this.
	In the considered version, the tank already has devices for its placement, even in two versions - legs for installation on a horizontal surface (blue arrows) and a mounting plate for hanging on a wall (yellow arrow). The tank is mounted in the selected location, and then connected by a pipe section to a tee embedded in the return line. On this installation can be considered complete.
	Another version of the tank, on the body of which there are no structural elements for fastening at the installation site. But they, as a rule, are included in separate parts in the package.
	Usually this is a bracket - a mounting platform for attaching to the wall, and a long screw band clamp.
	The summer of the clamp is straightened and threaded into the slots of the mounting platform.
	All this is done in such a way that the protruding side of the tank falls into a special groove of the mounting platform (shown by arrows), and the clamp is higher than the side.
	After installing the tank in the mounting area, the ends of the clamp are connected, first tightened manually ...
	.. and then - until it stops, using a screwdriver or wrench.
	In this form, the tank will be ready for hanging on the wall.
	Installation of plumbing fittings to the tank pipe is carried out in the same order as already mentioned above.
	The nipple is located openly, only with a dustproof plastic cap. Checking pressure and pumping, if necessary, is no different from the previously considered option.
	By the way, tanks usually come from the factory with a pre-set pressure in the air chamber, and you can immediately select the desired parameter. It is indicated on the packaging and in the technical documentation of the product. Further installation of the tank is carried out in the already known order - mounting on the wall in the selected place and connecting the pipe with a tee.

After the final installation, be sure to open the tap and fill the system with coolant. If no leaks are found in the connecting nodes, the installation of the expansion tank can be considered complete.

Video: inserting an expansion tank into a polypropylene pipe circuit

At the end of the article, it must be emphasized once again that a closed heating system with a sealed expansion tank must necessarily have a reliable “safety group”. If it is located in a place that is not very convenient for regular visual control, it makes sense to install an additional pressure gauge in the immediate vicinity of the expansion tank - it will be much easier to monitor the condition of the entire system.