Where to put the expansion tank for heating. Expansion tank for the heating system: installing an expansion tank according to the instructions

When arranging a heating system, one has to take into account many nuances associated with its individual elements, including not only radiators and a heat generator. An integral part of an efficient heating network is an expansion tank. This device seems primitive, but the quality of heating largely depends on it. When installing the tank, many errors are made that adversely affect the operation of the entire system as a whole. Let's consider in detail all the "dangerous" moments!

Where to install the expansion tank in the heating system?

The subtleties of tank installation depend on the type of heating system, which can be open or closed. The first variety is considered obsolete, but is still found in some homes. In this case, the expansion tank is a container with an open top and threaded connections at the bottom, to which pipes are connected. It is installed at the highest point, as required by the elementary laws of physics.

Closed heating systems are a modern option that requires the installation of a special container-capsule, divided into two parts by a rubber membrane. Membrane expansion tanks have the following installation requirements:

• accommodation in a boiler room near a heat generator;
• free access for operational maintenance;
• separate fixation of the eyeliner on the wall to avoid increasing the load on the tank;
• laying the eyeliner to the floor tank not across the passage;
• the presence of free space between the element and the wall.

Small containers are mounted on the wall with brackets, the main thing is that the base is sufficiently reliable. The location of the tank in space causes a lot of controversy. Some experts advise connecting pipes to the top of the element, leaving an air chamber at the bottom, which will help to easily remove air from under the membrane. However, the most correct solution would be the location of the tank with the connecting pipe down.

The bottom line is that the device will work in any position, but over time, defects will appear on the membrane. If the air chamber is at the bottom, then even if the membrane element is worn out, it will take a lot of time for air to penetrate into the coolant. When the tank is upside down, air will quickly enter the adjacent chamber, which will necessitate an urgent replacement of the device.

Where to install the expansion tank in the heating system?

When the tank is firmly fixed on the wall or installed on the floor, it is time to connect the element to the heating system. For this purpose, the shortest path to the junction is planned. Experts recommend connecting buried tanks on the "return". However, just before entering the heat generator, there is no place for the tank, the ideal option is up to the circulation pump and the shut-off valves that come with it.

The main advantages of this method are obvious:

• the membrane will last longer due to the not too high temperature of the coolant in the "return";
• there will be no problems in the operation of the circulation pump when the tank is inserted into the return pipeline;
• critical pressure does not appear in the "return", which allows you to keep the rubber elements of the container safe and sound.

However, in practice it has been proven that there is no particular difference in the functioning of a heating system with a tank on the return or supply pipeline. However, the described connection method is considered more reliable. If the choice nevertheless fell on the eyeliner, then do not forget to equip the pipe with a ball valve or fitting to block access to the tank in a timely manner and the possibility of its quick removal for repair or replacement.

How to set up an expansion tank in a heating system?

After installing and connecting the compensating tank to the heating network, it is necessary to perform the correct setting, which consists in creating the optimal pressure in the air chamber. Without proper implementation of this stage, it is impossible to avoid hydraulic shocks that occur when excess cooling coolant is pushed out by the membrane. Configuration work is carried out in the following order:

• the system is filled with cold water;
• air plugs are removed from pipes and heating batteries;
• the pressure in the network and in the air chamber is calculated using a pressure gauge;
• in the chamber, by bleeding or pumping, a pressure of 0.2 bar is achieved less than in the system.

Setting is the final stage, after which it is possible to start the heating network. Now the pressure in the tank will change smoothly both during heating and when the coolant cools down, without causing any problems. Remember that errors when installing a compensating tank are not immediately evident, but make themselves felt at the most inopportune moment - at the height of the heating season.

In fact, the installation of an expansion tank is not a very difficult operation. For its implementation, professional tools are not even required - the arsenal of a diligent home master will be enough. However, for inserting a container into the system and its subsequent configuration, it is necessary to carefully consider all the little things, ignoring which can be fatal. Only in this way the installed device will last a long time and will not cause trouble!

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 will change, 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 come in handy 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 of installation work, the air valve is 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.

The most common failure of such units is the 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 overtakes self-made open-type structures. 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 body.

• 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.

One of the advantages of an autonomous heating system is the ability to maintain a comfortable temperature in the house, regardless of the start and end of the heating season, and save on utility bills. Schematically, it consists of a heating boiler and a circuit through which the hot coolant circulates. Water is usually used as the heat carrier. An important role in heating equipment is played by the hot water circulation system, which consists of several parts. The correctness of its operation largely depends on such a structural element as an expansion tank.

An example of arranging heating with an expansion tank

Comparison of closed and open heating systems

The functioning of an open heating system is based on the laws of thermodynamics, due to which the movement of the coolant is carried out. From the area of ​​high pressure and the corresponding temperature at the boiler outlet, the water moves through pipes to the area of ​​lower pressure, and its temperature decreases. The cooled coolant is sent back to the boiler, and the process is repeated. Thus, there is a natural circulation of the liquid, according to the laws of physics.

Since when water is heated, its volume increases, an expansion tank is provided in the design of an open heating system. For efficient movement of an open-type coolant, the expansion tank is installed at the highest point of the system, and the heating boiler at the lowest. Installing an expansion tank in the attic seems to be the best option. Its device is not complicated.

Open type heating scheme

Over time, water evaporates, so its level must be replenished in a timely manner. During interruptions in the use of heating and at negative ambient temperatures, the water must be drained, otherwise it will freeze in the pipes and break them. An open heating system has the following advantages:

• independence from sources of electrical energy;
• no noise;
• ease of maintenance;
• quick start and stop.

You can choose radiators for any type of heating system based on the recommendations of the article

In a closed heating system, water evaporation does not occur, since it is hermetic. The movement of the coolant is carried out using a pressure or circulation pump, which can be found in the article. At the same time, an expansion tank made of durable metal is also required for efficient operation. The closed heating system consists of a heating boiler, a circulation pump, a pipeline network, radiators and an expansion tank. A closed heating system has the following advantages:

• no need for constant monitoring of the coolant level;
• the possibility of using antifreeze;
• adjustment of internal pressure;
• the ability to connect additional devices.

Closed heating system

With proper installation of heating equipment, both options will work perfectly. The choice between them is determined by the operating conditions and placement features. There are the following differences between the two systems:

• In an open heating system, the expansion tank is located at the highest point. In a closed heating system, it can be located almost anywhere.
• The likelihood of air locks in a closed heating system is much lower. This is due to the increased internal pressure and the lack of direct contact with the atmosphere.
• For the operation of an open heating system, pipes of large diameter are required. Installation work is complicated by the need to take into account the rules of hydraulics when distributing flows, making turns, slopes, and so on.
• Small-diameter pipes used in a closed heating system reduce its cost. Here it is important to correctly install the circulation pump so that during its operation it creates as little noise as possible.

The device and functions of the expansion tank in the heating circuit

The function of the expansion tank in an open heating circuit is to receive excess water when it expands due to heating, and return it to the system when the temperature drops. The container is not sealed, and the coolant is in direct contact with the environment, so water evaporates in an open heating system. The device is simple in design, if necessary, it can be done by hand.

Expansion tank open type

The disadvantages of an open system include the need for constant monitoring of the water level, as it evaporates, the danger of freezing the liquid in the expansion tank, and the impossibility of using antifreeze as a coolant. In addition, air entering the system causes air pockets, corrosion of internal parts and their cavitation.

In a closed heating circuit, the expansion tank is made of high-strength metal. The device consists of two halves, sealed to each other. The design includes a receiving valve and an internal membrane. When the temperature of the coolant rises, the valve opens, and the excess of the increased volume of liquid enters the expansion tank.

The diaphragm, made of heat-resistant high-strength rubber, divides it into two parts. Gas is pumped into the upper part of the sealed container, and a hot coolant enters the lower part, compressing the membrane and the gaseous medium located behind it. When the working fluid cools, due to the expansion of the gas medium, the diaphragm squeezes it back into the heating circuit.

The membrane tank can be installed horizontally or vertically in any position.

Closed type expansion tank device

The performance of a closed-type expansion tank does not depend on its orientation in space, which cannot be said about the service life. To extend the operating period of the membrane tank, it is better to position it so that the air chamber is on top. Over time, cracks appear in the diaphragm, and until their size and number reach a critical level, the system will work properly when the container is placed vertically. In a horizontal position (in the event of cracks in the diaphragm), air from its half will quickly penetrate into the coolant and vice versa, and therefore an urgent replacement of the tank will be required.

What causes the insufficient volume of the built-in boiler tank

Insufficient volume of the built-in boiler tank can lead to malfunctions in the heating system. When heated, the liquid expands, and its excess enters the expansion tank. If its volume is insufficient, the tank overflows, and the emergency pressure relief valve bleeds the coolant into the drain. The rest of the cooled coolant is returned to the heating circuit.

Pressure in the system with insufficient volume of the expansion tank

As a result of a decrease in its amount, a decrease in the internal pressure in the system occurs. If it decreases by a small amount, the boiler will function, with a significant decrease in pressure, the operation of the heating equipment will be blocked.

If the coolant level is not replenished to normal in a timely manner, the system may defrost, so such emergencies should not be allowed to occur.

Calculation of the required volume of the membrane tank

The required volume of the membrane tank is calculated using a simple formula. Its value is ten percent of the total amount of coolant circulating through the system, if water acts as this. The total volume of the coolant can be determined from the readings of the water meter when filling the heating system.

A more accurate figure is obtained by summing up the volume of all pipes, the capacity of the boiler and batteries. It is believed that fifteen liters of coolant are required for one kilowatt of boiler equipment power, that is, the total volume of liquid is determined by multiplying the nominal power of the boiler by fifteen. This value will lie within the margin of error.

Illustration of the change in volume in the tank with fluctuations in pressure in the system

For example, if three hundred liters of water are needed for the operation of heating equipment, then the volume of the membrane tank should be thirty liters. This parameter increases by fifty percent when using an antifreeze liquid as a coolant, that is, in this case, the required volume will be forty-five liters. In addition, the possibility of leaks must be taken into account and the calculated value must be increased by about three percent more. When the size of the membrane tank is correctly determined, the emergency pressure relief valve does not work.

Set the optimal pressure in the tank

Before connecting the expansion tank and filling it with coolant, it is necessary to set the optimum pressure in its air chamber corresponding to this parameter in the heating network. To perform this procedure, a plastic cover is removed from the air compartment, under which there is a nipple, the same as in automobile tires. The pressure measured by the pressure gauge is adjusted to the desired value by pumping with a pump or by bleeding when pressing the nipple stem.

Protection group monitors system pressure

The optimum pressure in the tank is obtained by adjusting the internal pressure in a closed heating system downwards. This is done so that the rubber diaphragm is pressed from the side of the coolant. Otherwise, when it cools down, air will be drawn in through automatic vents, which should never be allowed. For example, if the internal pressure in the network is 1.2 atmospheres, then its optimal value in the expansion tank will be one atmosphere. After setting this value, you can open the tap and fill the system with coolant.

At intervals of six months in a closed-type compensation tank, it is necessary to check the pressure and perform a visual inspection for mechanical damage.

With a sharp change in internal pressure and temperature in the heating network, there is a risk of damage to the membrane, and in this case it will need to be replaced. To do this, you must perform the following manipulations:

• disconnect the expansion tank from the line;
• relieve pressure in it by pressing the spool rod;
• remove the damaged membrane, drain excess water and install a new one;
• after setting the optimum pressure, attach the container in place.

Choosing the location of the expansion tank

The installation of an expansion tank depends on the type of heating system and the purpose of the tank itself. It is better to install a closed type compensation tank on the return line in front of the heating boiler and circulation pump.

Expansion tank placement and mounting options

If it is located on the supply line, the life of the membrane will decrease due to the constant exposure to a higher temperature of the coolant. In addition, in this case, in the event of an emergency, steam can penetrate into the expansion tank, as a result of which the diaphragm will no longer compensate for the coolant pressure, since the mixture of air and steam is a compressible medium.

The expansion tank is connected through a shut-off ball valve. This is done so that, if necessary, it is possible to quickly replace the compensation tank without waiting for the coolant to cool down. Installing a second tap makes it possible to pre-drain hot water from the tank.

How to install a closed expansion tank with your own hands

The connection scheme is not particularly complicated. You can correctly mount a closed expansion tank with your own hands by observing the following connection diagram. The pre-heating boiler is de-energized, the coolant supply is shut off, water is drained from the radiators.

If polypropylene pipes are used for installation, a special soldering iron is required for their installation. You will also need couplings and corners. Of the fittings, it is better to use the "American", as it makes it possible to easily remove the container for maintenance and repair. The following is a sequential diagram of the steps for installing an expansion tank.

1. A sealing thread is wound on the threaded part of the tank fitting.
2. An adapter is screwed onto the fitting for installing a tap.
3. A sealing thread is wound on the threaded part of the adapter.
4. A shut-off valve is installed on the adapter.
5. A sealing thread is wound on the threaded part of the "American". "American" is wrapped in a tap with the help of pliers and an adjustable wrench.
6. A sealing thread is wound on the threaded part of the corner. The corner is wrapped in an "American".
7. A collar for fastening the tank, which is included in the delivery set, is put on the tank body.
8. On the opposite side of the tank there is a nipple for air injection, on which a plastic cap is screwed.

After placing the expansion tank in the selected location, the quality of all connections is checked, and the coolant is supplied to the system. After the internal pressure in the batteries reaches the calculated values, air pockets are bled from them, and the heating system starts up at full capacity. The compensation tank is installed so that it is convenient to maintain, that is, free space is left between it and the wall.

Seal all joints with sealants that are resistant to high temperatures, otherwise leakage is inevitable. The membrane expansion tank in a closed heating system is installed on the side of the cold water supply. When performing all manipulations, safety requirements must be observed.

The volume of the coolant changes depending on the change in temperature conditions, which can lead to dangerous consequences. For safe and long-term operation of the coolant, it is necessary to maintain its stable characteristics. A diaphragm expansion tank can be used for this.

Purpose and design features

In heating systems, the heat carriers are liquids that are in the process of weak compression. For the safe operation of the heating system, it is necessary to use a stabilizing device - a membrane expansion tank, which is capable of receiving a certain amount of liquid in the process of increasing pressure and volume, and then returning it to the circulation circuit when these indicators decrease.

Membrane expansion tanks have a number of advantages over other devices of the same purpose, namely:

• suitable for any water, even if it contains a large amount of calcium;
• safe to use for drinking water;
• have a larger useful volume to be displaced than a pressure tank without a membrane;
• minimal air intake is required;
• economical and fast installation;
• low operating costs.

However, these devices also have disadvantages, namely:

• the large size of the expansion tank makes the installation process quite problematic;
• due to the release of heat by the coolant to the expansion mat, heat losses increase;
• increased risk of rust formation.

To avoid uncontrolled heat loss, experts advise insulating the device.

Differences from the accumulator

The design of sealed expansion tanks is similar to the design of hydraulic accumulators, however, the purpose of these devices is different. The expansion tank compensates for the expansion of water due to heating in the heating system. The hydraulic accumulator accumulates the volume of water under pressure in the water supply system that has a pressure pump in order to reduce the frequency of switching on this pump and smooth out water hammer. In addition, more often inside the accumulator there is a pear made of food grade rubber. It is she who is pumped with water, as a result, water does not come into contact with the tank body. Expansion tank for heating systems is made with a membrane made of technical rubber. It divides the body into two compartments, and the coolant has contact with the body.

Device and principle of operation

A membrane tank is a hermetically sealed metal container divided into two compartments (chambers) by an elastic membrane. One of these chambers is the pneumatic chamber, which contains pressurized gas or air. The coolant enters the second chamber - the hydro-chamber.

The device works as follows:

• the air pressure, which is in a state of equilibrium, in the pneumatic chamber compensates for the fluid pressure in the heating system, the volume of the coolant and the hydrochamber is minimized;
• when the pressure of the liquid rises in the system, including when heated, there is an increase in pressure in the hydrochamber, where the excess coolant enters;
• due to the elasticity of the membrane, the volume of the pneumatic chamber decreases, which is accompanied by an increase in gas pressure;
• when the pressure in the pneumatic chamber increases, the increase in pressure in the hydraulic chamber is compensated, and the system returns to a state of equilibrium.

With a decrease in the pressure of the coolant in the system, opposite actions occur. The gas (air) compressed in the pneumatic chamber expands and displaces the liquid from the hydraulic chamber into the system until the pressure difference is restored. The design eliminates the possibility of contact between the coolant and air, reducing the likelihood of rust not only in the tank, but also in other parts of the heating system - pipelines, boilers. Sealed expansion tanks are equipped with safety valves to limit the maximum pressure in the heating system to an acceptable level. This also characterizes the tank as a protection device for the heating system.

Types and selection criteria

To compensate for the volume of coolant in the system during temperature changes, two types of expansion tanks are used: open and closed (sealed).

Open expansion tanks are widespread, but have the following disadvantages:

• high installation costs, since such tanks are mounted at the top of the system to create the required level of increased pressure;
• it is necessary to constantly monitor the level of the liquid;
• there is a risk of rust in the system due to prolonged contact of the heated coolant with air.

Sealed expansion tanks do not have such disadvantages. For heating systems, tanks are produced that differ in the use of the membrane. Membranes are divided into balloon and diaphragm types. The balloon membrane is a container installed inside the tank, made of high quality rubber that can withstand significant temperature fluctuations. Flanged fastening of such a membrane will allow you to replace it quickly and easily.

Balloon-type membranes have such advantages as:

• a wide range of operating pressures, making it possible to use a hermetic expansion tank;
• the possibility of changing the membrane, which helps to make the repair of this device cheaper and faster;
• simple setting of the minimum pressure for any systems.

The diaphragmatic membrane is a non-removable septum, which, most often, is made of an elastic polymer or thin metal. This membrane is characterized by low self-capacitance and the ability to compensate for small pressure drops in the system. If such a tank fails, it will need to be completely replaced. One of the privileges of this device is its low price. In addition, the diaphragm tank is simple in design and reliable in operation.

Choosing the right expansion tank means ensuring the safety of the heating system, therefore When choosing an expansion tank, you should pay attention to the following main characteristics:

• membrane material, its resistance to high absolute values ​​of temperatures, pressures and differences in these indicators;
• body material and coating, rust resistance;
• compliance with sanitary and hygienic standards;
• execution (mounting method).

Restrictions

Manufacturers impose certain restrictions on the use of membrane expansion tanks, which depend on the design and materials used in the manufacture of the device. Manufacturers impose clear requirements on the properties and composition of the fluid in the heating system. The content, for example, of ethylene glycol in the antifreeze solution is limited. The use of a diaphragm expansion tank at pressures exceeding the permissible limits is prohibited. It is mandatory to install a safety group that controls and limits the pressure in the tank. The heating systems of independent heating apartments and private houses use equipment with a working pressure of at least 3 bar.

Volume calculation

Volume is the main characteristic by which an expansion tank is selected. Many sources advise choosing the volume of the expansion tank within 10% of the total volume of coolant in the heating system. This method of determining the capacity of the device is based on the fact that the coefficients of thermal expansion of the coolant, even with a glycol content of up to 90% and heating of +100 degrees, do not exceed 0.08. This calculation method does not take into account the pressure in the system, so it may give inaccuracies. There is a more accurate method for calculating the volume of a membrane expansion tank. The ratio is used here:

V = C*Bt / (1 - (Pmin / Pmax)), where

• C is the volume of the coolant in the system;
• Bt is the coefficient of thermal expansion of the coolant;
• Pmin is the initial pressure in the tank;
• Pmax - allowable pressure in the system.

The volume of coolant in the heating system is determined, taking into account all its nodes. This parameter is obtained from the design documentation for heating. If this is not possible, you can use an approximate calculation, which is based on the fact that the volume of coolant in heating systems is related to the heating power - for every kW there is 15 liters of liquid. The coefficient of thermal expansion of a liquid is determined using its composition - most often, in the heating systems of apartments and houses, it is possible to add glycols to water to improve its characteristics. This coefficient may also depend on the temperature of the coolant. You can find the required values ​​​​in the tables of the volume of water in the pipe.

The maximum pressure in the heating system is determined using the minimum of the values ​​\u200b\u200bthat are allowed for different nodes. The transfer valve is adjusted exactly to it. The initial pressure in the heating system with a cooled coolant corresponds to the setting (minimum) pressure. For many devices, it is possible to accurately regulate it by common means (bleeding air from the tank or pumping it up with a pump). The pressure in the tank is controlled during the installation of a pressure gauge on it. The calculated data will give an increase in the volume of the coolant in the system during its heating. To select a tank, the fill factor is rounded up. The coefficient depends on the maximum and initial pressure and can be found using tables provided by manufacturers or in specialized literature.

Installation

Installing a membrane expansion tank is not difficult, but it is better to entrust it to a specialist. First of all, the instructions for the device must be used. When installing this device in a heating system, it is important to carefully check the tightness of the connections. The expansion tank must not be opened or dismantled. It is simply connected to the pipeline closest to the boiler. Safety devices are installed to prevent pressure build-up.

When installing the tank, the following rules should be considered:

• the tank is installed before branching;
• the temperature in the room must be constantly above 0;
• you need to double-check all calculations before installation;
• a tank with a volume of more than 30 liters is not attached to the walls, but is placed on legs;
• to control the pressure at the outlet of the tank, a pressure gauge is installed, at the inlet - a check valve (if there is no pump);

• the device must be in a place comfortable for maintenance and adjustment;
• when attaching the tank to the wall, it is necessary to maintain a height on the bracket that will be convenient for access to the shutoff valves and to the airspace;
• the underwater pipe and the crane should not overload the expansion tank with their weight, the liner must be strengthened separately;
• to a membrane tank located on the floor, it is impossible to lay an eyeliner across the floor across the passage;
• there must be a distance between the wall and the tank for inspection.

The use of an expansion tank is necessary in every closed heating system, and even in some systems connected to central heating. The process of installing an expansion tank is quite complicated, but if you carefully study the instructions to do it yourself, without the involvement of specialists, it is quite possible.

The principle of operation of the expansion tank

The expansion tank is a metal tank that is connected to the heating system. The main function of this device is to eliminate the increase in pressure in the pipeline, as a result of the expansion of the coolant.

Expansion tanks are of two types: open and closed. The principle of operation of each of these tanks is different from each other.

The open expansion tank has a metal cover that opens to add coolant to the system.

The closed expansion tank consists of a metal container that has no openings other than to connect to the system. The container is separated by an internal membrane made of rubber. When the pressure rises, the rubber bends and the coolant enters the tank, when the pressure decreases or the coolant leaks, the rubber presses on half of the tank in which the gas is placed and the coolant enters the system. Thus, the expansion tank is a pressure regulator that prevents high voltage surges from occurring in the system. If you do not use an expansion tank, the heating system will not function normally, and the taps, pipes and boiler will quickly fail.

Expansion tanks are used in a private heating system, and in some cases in a system connected to a central heating system.

Varieties of expansion tanks for heating

Expansion tanks are divided into:

• open,
• closed.

An open expansion tank has a number of disadvantages, therefore it is rarely used, mainly in cases where the system is not connected to a pump and water circulates freely.

Disadvantages of an open expansion tank:

• due to the frequent opening of the lid, the components of the heating system come into contact with oxygen, which causes rust to form on the walls of pipes and radiators;
• when the water temperature rises, the liquid evaporates, so the coolant should be added to the system periodically;
• an open expansion tank is installed at the highest point compared to the heating system, so the installation of such a device takes a lot of time.

The only advantage of an open expansion tank is its low cost compared to a closed one.

A closed expansion tank is called a membrane tank, depending on the type of membrane, there are:

• expansion tanks of replaceable type,
• expansion tanks of non-replaceable type.

Replaceable expansion tanks involve the replacement of the membrane, if damaged. To replace the membrane, it is enough to unscrew the flange.

Non-replaceable expansion tanks imply the replacement of the entire tank if the membrane is damaged. Such tanks are more resistant to pressure drops, and the membrane fits perfectly and hermetically to the outer wall of the tank.

Expansion tanks come in two forms:

• balloon,
• flat.

The balloon shape resembles a large container in which a membrane or a lid is located, depending on the type of tank.

Flat expansion tanks have a flattened shape and a membrane in the form of a diaphragm. The advantage of flat expansion tanks is that they take up little space and are easy to install.

Calculation of an expansion tank for heating

The size and volume of the expansion tank is affected by:

• system type;
• capacity of the system;
• maximum allowable pressure;
• location of the expansion tank.

The easiest way to determine the volume of an expansion tank is to find out the capacity of the heating system and divide this amount by 10%. For example, if the heating system contains 400 liters of coolant, then the volume of the expansion tank will be 40 liters, if the coolant is water. If glycol liquid is used as a heat carrier, then another 50% must be added to this amount.

Please note that 3% of the coolant in the closed expansion tank comes to compensate for possible leaks. In any case, the tank volume obtained as a result of the calculation should be slightly increased.

To get an accurate calculation in large or complex heating systems, it is better to trust the experts or use an online calculator.

The correct calculation of the expansion tank is indicated by the failure of the safety valve.

Installation of an expansion tank for open heating

An open expansion tank is a place for water to come into contact with oxygen. An open container is used when water is free, without using a pump, moves through the system or when the system is connected to central heating.

Since air is in contact with water, the entire heating system is designed with a slope so that excess oxygen is forced out of the radiators.

Expansion tank installation location: the highest point, in relation to the heating system. The installation height of the expansion tank must exceed the installation height of the heating system.

Expansion tank installation diagram:

Installation of an additional expansion tank is carried out if it is impossible to mount the heating system at an angle. The installation level of the main and additional expansion tank must be the same.

The open expansion vessel includes branch pipes:

• expansion,
• signal,
• circulation,
• overflow.

Using an expansion pipe, the tank is connected to the heating system.

In most cases, an open expansion tank is mounted near the boiler and connected to the water supply system using a signal pipe that controls the level of the coolant.

An overflow pipe connects the tank to the sewer; when the tank overflows, the liquid is automatically drained into the sewer.

The circulation pipe provides the supply of coolant if the expansion tank is located in an unheated room.

Installation of a closed expansion tank

Before studying the rules for installing a closed-type expansion tank, consider the advantages of this device over an open expansion tank:

• minimal heat loss;
• do not need isolation;
• work at high pressure surges;
• installation anywhere, without reference to the highest point;
• closed-type devices are more compact and easier to install;
• no rust formation on the inner walls of the heating system;
• ease of maintenance.

Tools for work:

• wrench;
• key for installing plastic pipes;
• step key.

The preparatory stage includes:

• disconnecting the boiler from electricity, gas supply or water supply;
• shutting off the valve responsible for the circulation of the coolant;
• draining the coolant from the heating section on which the expansion tank is installed.

Expansion tank installation instructions:

1. Install a shut-off and drain valve on the supply pipe to shut off and drain water.

2. Use screws or flanges to connect the expansion vessel to the system. If the pipes of the heating system are polypropylene, you need to use a soldering machine, couplings, corners and fittings.

3. A fitting called "American" will help in the future to easily remove the tank for replacement or repair. Before installing the fitting on the expansion tank, wrap linen tape around the threads and apply sealing paste.

4. When the water is drained from the system, cut the pipe with special scissors and install a tee.

5. Install relief valve and pressure gauge.

6. Before starting the system, clean the coarse filter.

7. Before connecting the expansion tank to the system, you need to create a working pressure. To do this, use a pump.

8. When the expansion tank is connected to the network - start all the coolant supply valves and turn on the boiler.

1. Install the expansion tank in such a way that the coolant enters from above.

2. In the absence of data on the exact volume of the heating system, the capacity of the expansion tank is calculated based on the boiler power: 15 liters of liquid are calculated for 1 kW of power.

3. Before buying and installing an expansion tank, inspect the heating boiler. Many modern boilers have a hidden expansion tank located in the middle of the boiler.

4. Do not mount a closed type expansion vessel near the circulation pump, due to the occurrence of large pressure drops.

5. Installation of a vacuum expansion tank is carried out only at a positive temperature.

6. Installation of a closed-type membrane expansion tank is carried out from the side of the cold water supply to the boiler.

7. As a sealant, use only those sealants that are resistant to high temperatures, otherwise leakage is inevitable.

8. When determining the location and installation of the expansion tank, you should think about the further approach or maintenance of the device. Do not install the expansion tank in hard-to-reach places.

9. When installing the expansion tank, follow the safety rules and generally accepted instructions.

10. Be sure to read the manufacturer's instructions for installing the expansion tank.

11. Be sure to install a safety valve, which sometimes comes with the tank, if there is no valve, buy it separately.

Maintenance of expansion tank for heating

1. Once every 6-7 months, the expansion tank should be inspected for mechanical damage or rust. If they are, you need to fix the problem.

2. Expansion vessels of closed type should be checked for pressure once every six months.

3. In devices with a replaceable diaphragm, periodically check the diaphragm for integrity or damage.

4. If the expansion tank is not used for a long time, store the tank in a dry place, be sure to drain all the water and dry the appliance.

6. It is best to use an inert gas such as nitrogen to fill the air chamber.

7. Proper operation of the expansion tank depends on the pressure and temperature of the heating system.

8. With a sharp drop in pressure, there is a risk of damage to the membrane. To replace the membrane, you need to perform a number of actions:

• disconnect the expansion tank from the system;
• relieve the pressure in the tank using the valve, which is located at the top of the tank;
• remove the flange located at the point where the tank is connected to the system;
• remove the membrane and drain excess water;
• insert the membrane and install the flange;
• attach the tank, after setting the desired pressure.