How to install a membrane tank. Storage tank for water supply Connect expansion tank

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

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

The main task is to perform 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 to prevent air from coming into contact with the coolant. Otherwise, airing of the network and an increased risk of corrosion of steel elements of the system cannot be avoided.

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

How to connect an expansion tank

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

The operating principle 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 flows by gravity into the heating radiators and, when cooled, returns to the boiler through the return pipeline. There is always dissolved oxygen in water, which is released through the process of convection, which means that air bubbles tend to rise.

When considering this diagram, it becomes obvious that the only possible installation 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 for a membrane tank in an open type heating system

As a tank, you can use any container of a suitable size made of heat-resistant material. A lid (not sealed) is needed only to protect it from debris getting into the system. If you don’t have a small metal barrel 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 of the house.

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

Expansion tank in a closed heating system

Equipment for the heating system is selected at the design stage, taking into account the requirements for the performance of the boiler unit, the length of pipelines and the volume of coolant involved. A diagram is being developed that indicates the installation locations of all system elements, including the expansion tank. In a closed heating system, it is necessary to use a membrane device.

Expander in a closed heating system

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

The tank should be placed in such a way as to ensure normal access for installation and further maintenance. Floor-standing models are not recommended to be installed close to the wall.
If the device 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. Typically, 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 should not be placed on the floor across the passage or suspended at human height.
The pipes connected to the expansion tank must be secured to the wall. It is important to avoid a situation where the load from them and from the shut-off valves falls on the tank pipes. Separate mounting of pipes and taps makes it easier to replace the expansion device in case of failure.

At the equipment selection stage, 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 liquid circulating in the system. It is permissible to use a larger tank. But a tank that is not large enough can become a source of problems, since it is not able to compensate for the increased pressure in the system.

Rules for placing the expansion tank

For approximate calculations of the volume of coolant in the system, you can take the thermal power of the boiler unit as a basis. On average, 15 liters of liquid are used per kilowatt. Exact calculations are made taking into account the length of pipelines, 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. There is no need to purchase a separate tank 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, thanks to which excess pressure is automatically released. If one is not provided for by the design of the device, you should buy a safety valve separately and install it in close proximity to the tank.

Where is the best place to put the tank?

The optimal place for installing a membrane tank is a straight section of the pipeline, which is characterized by laminar flow of water, that is, the absence or minimal amount of turbulence. A convenient place is the spill area near the circulation pump.

Note! The expansion tank of a closed heating system can be installed at any convenient height. There is no need to place it at the highest point, since it functions solely as a surge protector. Unlike an open-type heating system, the air accumulated in the pipeline is released 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 tank placement

If desired, the tank can be placed on the supply line; this will not affect the operational properties of the heating system. But the membrane tank itself will not last a relatively long time, since the polymer membrane will be in constant contact with the coolant that 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 not recommended if the heating 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, which is why the membrane will not be able to 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 connection. This installation principle makes it possible, if necessary, to shut off the flow of water in the system at any time, remove the faulty membrane tank and install a new one.

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

By hanging the expander upside down, if the diaphragm malfunctions, the unit will fail immediately

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

However, it is worth considering this point: if the air compartment is located at the bottom, 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 positioned with the air chamber upward, its service life is extended. Over time, from constant contact with hot water, the polymer membrane loses its tightness and cracks appear in it. If the air chamber is located at the bottom, then water will immediately begin to seep into the air compartment, which will quickly damage the expansion tank, while air will penetrate into the coolant. When the air chamber is located on top, the diffusion of water through cracks occurs many times slower, and the device can operate much longer.

Useful tips:

If you install a pressure gauge next to the expansion tank and the valve, thanks to which the heating system is fed from the water supply, it will allow you to control the pressure in the system in order to bleed off excess in time if the safety valve spool is stuck and does not operate automatically.
Frequently repeated release of pressure by the valve indicates that the capacity of the expansion tank is selected incorrectly. Instead of changing it to a larger tank, just 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 circuit of the expansion tank should be equipped with a safety group

Settings

Before connecting the tank and filling it with coolant, you need to check the pressure level in the air chamber of the tank - it must correspond to the pressure in the heating system. For this purpose, you should remove or unscrew the plastic plug that covers the spool valve (similar to those installed in car cameras). Using a pressure gauge, 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 a pump or, vice versa, it is bleed by pressing the spool rod.

Note! The tank should be adjusted so that the pressure in its air chamber is 0.2 bar less than the design pressure in the system filled with coolant. If the pear-shaped membrane is not pressed on the water injection side, the coolant, compressing during the cooling process, 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 starts up.

The adjustment step is not required if the factory pressure in the air compartment of the expansion tank corresponds to the required parameters. Manufacturers of some brands of equipment indicate the pressure level in the tank on the packaging, which makes it possible to select the optimal option when purchasing.

Conclusion

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

You have successfully selected and purchased a membrane-type tank for your heating system. The time has come to install it, and a lot of questions arise: where to put it, how to connect it, and so on. There is a lot of advice on this topic on the Internet, all of it contradictory. To clarify all controversial issues and consider in detail how to properly install an expansion tank, we bring to your attention this article.

Where to place the expansion tank in a closed heating system?

By the way, in private houses there are no open and closed systems; there are gravity and pressure (pump) systems. In the first, water moves due to the difference in specific gravity (natural circulation), and in the second, it is forced by a pump.

For reference. An open system works simultaneously for heating and hot water supply, and is used only in large centralized networks. This is why all individual systems are closed.

To correctly install the expansion tank in the heating system, the following requirements must be met:

the location of the tank is the combustion room, not far from the boiler;
the device must be placed in a place where it can be easily accessed for setup and maintenance;
if the tank is mounted to the wall on a bracket, it is recommended to maintain a height convenient for access to its air valve and shut-off valves;
The supply pipe together with the taps should not load the expansion tank with its weight. That is, the eyeliner should be attached to the wall separately;
the supply line to the floor expansion tank for heating is not allowed to be laid across the floor across the passage;
Do not place the container close to the wall; leave enough clearance for inspection.

Tanks of small capacity can be hung from the wall, provided that its load-bearing capacity is sufficient. As for the orientation of the tank in space, there is a lot of conflicting advice. Some recommend an installation method in which the pipe is connected to the container from above, and the air chamber, accordingly, is located below. Rationale - it is easier to remove air from under the membrane when filling; water will displace it.

In fact, in its original state, the rubber “bulb”, pressed on one side by air pressure, leaves no room for it on the other side, as shown in the photo above. Installation specialists advise installing the expansion tank with the connecting pipe downwards, and only this way. In some models, the fitting is initially located on the side wall, in its lower part, and it is impossible to position the vessel differently (see photo below).

It's easy to explain. The device will function in any position, even lying on its side. Another thing is that sooner or later cracks will appear in the membrane. When the membrane expansion tank is installed with the air chamber up and the pipe down, the air will penetrate through the cracks into the coolant very slowly and the tank will last for some time. If it stands upside down, then the air, being lighter than water, will quickly flow into the coolant chamber and the tank will have to be urgently changed.

Note. Some manufacturers suggest installing the expansion tank of the heating system by hanging it “head down” on a bracket. This is not prohibited, everything will work, only if the membrane malfunctions, the unit will fail immediately.

How to connect an expansion tank

After the container is securely attached to the wall or fixed to the floor, it is necessary to correctly connect the expansion tank to the heating pipelines. To do this, you need to outline a route for the pipe that runs the shortest route to the connection point. It is believed that the best connection point for closed membrane tanks is on the return pipeline. Just not just before the entrance to the boiler, but before the circulation pump (if it is not installed on the supply) and the accompanying shut-off valves. The expansion tank installation diagram is shown below:

There are several justifications for this sidebar:

in the return, the coolant temperature is much lower, which will extend the service life of the membrane;
if the installation and tapping location is on the return pipeline, then the circulation pump operates in comfortable mode;

In the supply pipeline of a solid fuel boiler, critical pressure and a steam-water mixture may occur due to overheating for various reasons. If this mixture gets into the rubber “bulb” of the container, it will stop performing its functions.

In fact, practice shows that there is no big difference in connection between supply and return. It is simply customary to connect the expansion tank to the heating system via a return pipeline, it is more reliable. But what definitely won’t hurt is a shut-off ball valve on the inlet, or even better, a fitting for emptying and a second valve. Then at any time the tank can be cut off from the system, the water drained from it and removed for repair or replacement.

Advice. For those whose gas boiler is not equipped with a pressure gauge or a safety group, it would be useful to integrate it into the circuit of the expansion tank using the following installation diagram:

Setup Guidelines

After installation and insertion of the device into the heating network, it is required to configure it. It is to provide the necessary pressure in the air chamber to match your system. This is necessary to avoid water hammer in the network; they can be created by the membrane of the tank while the coolant cools and its excess is pushed out of the chamber. The operation is performed in the following sequence:

when the installation of a closed tank is completed, the system is filled with cold water;
using Mayevsky valves and taps, air pockets are removed from pipes and radiators;
a pressure gauge measures the pressure in the system, and then in the air chamber of the tank;
By bleeding or pumping up, the pressure in the chamber is set 0.2 Bar lower than the pressure in the system.

Now that the expansion tank has been correctly installed and then configured, you can start the boiler. The pressure in the container will increase equally smoothly as the coolant heats up and cools down.

Conclusion

In principle, installing a compensating tank is not a very complicated procedure. Any special tools or devices are also not required; a regular set, which every thrifty owner has, is enough. But in order to install the tank in the heating system and configure it, you need to be more careful and not miss any little details. Then the device will last a long time and without problems.

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 competently 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 take a closer look at them and find out 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 coolant in the heating circuit and pipeline, which are not elastic, with a change in the temperature of the coolant, the pressure level in the entire system will necessarily change. Here it is worth considering the fact that 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 comes the definition of water hammer.

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 extend its service life and avoid many serious problems.

Such items are used for the following purposes:

play the role of a heating system, which operates using 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 the temperature of the liquid in the heating system increases by only 15 degrees, due to expansion, the volume of the coolant becomes half a percent larger. The expansion tank is responsible for compensating for this expansion. An excess of coolant fluid penetrates into the tank itself. If the coolant cools down, the design of the tank squeezes out insufficient liquid back into the general system.

If there is a slight leak of liquid, so that the pressure in the system does not drop too much, the tank pushes away the coolant to compensate for the losses that have occurred.

In the case where the system is not equipped with an expansion tank, the expansion of the coolant provokes an increase in pressure. In addition, these processes certainly result in severe wear of the component elements 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 part there is no water pollution;
most expansion tanks are inexpensive;
ensure the reliability and safety of the entire system;
allow you to avoid unnecessary heat losses;
have the smallest amount of air in the system;
in equipment responsible for heating, there can be any coolant - an expansion tank is allowed to be used in all cases;
taps, pipes and radiators can last much longer if you use an expansion tank.

As for the direct volume of the expansion tank, it is worth considering that it directly depends on the specific type of coolant. We will look at how it can be calculated below.

Today in stores there are units whose size 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 respects.

Only their immediate purpose remains unchanged.

Design and principle of operation

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

Typically, the expansion tank structure as a whole is housed in a stamped steel housing. It has the shape of a cylinder. Cases in the form of peculiar “tablets” are slightly less common. Typically, high-quality metals coated with an anti-corrosion protective compound are used to produce 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 versions, but this color is usually worn by water batteries, which are components 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 connection into the heating system. There are cases when the delivery also includes items such as fittings. They greatly simplify installation work.

On the other side, there is a special nipple valve. This element serves to generate the required level of pressure in the inside of the air chamber.

In the internal cavity, the expansion tank is divided into 2 separate parts by a membrane. Closer to the pipe there is a chamber intended for the coolant, and on the opposite side there is an air chamber. Typically, tank membranes are made of a very elastic material, which has minimal diffusion values.

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

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

In the initial state, at the moment the tank is connected to the system and filled with coolant, a specific volume of water passes through the pipe into the water compartment. The pressure in both compartments gradually equalizes. Further, such a simple system becomes static.
As the temperature value increases, there is a direct expansion of the coolant in volumes in the heating system. This process occurs 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 coolant chamber 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 coolant decreases, excess pressure in the chamber with air provokes a shift of the membrane back. At this time, the coolant 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, it will be responsible for releasing excess fluid. Certain models of expansion tanks have their own individual safety valve.

Of course, it is worth considering that the design of the tank mainly depends on the type of specific model purchased. For example, they can be non-separable or with the ability to replace 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 position the floor-standing unit on a flat plane.

Expansion tanks with a diaphragm membrane 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 an ordinary water chamber. As pressure increases, it stretches and increases in volume. These types of tanks are usually complemented by a collapsible flange, which makes it possible to independently change the membrane if it breaks.

This fact does not affect the principle of operation in any way.

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 method of operation, tanks are divided into:

open type heating tanks;
closed expansion vessels.

Open options for expansion tanks are considered not the most popular. These units are installed in systems in which liquid circulation is not carried out in a forced mode (that is, without the use of a pump)

The open expansion tank has a lid that opens without any extra effort if you need to add water.

The main disadvantage of such a unit is that the coolant in it is associated with oxygen, and this provokes corrosion in the heating system. If there is not sufficient tightness in an open tank, then the water evaporates many times faster, so it has to be constantly topped up. According to experts, such a unit must be installed at the highest section of the heating system. It should be taken into account that carrying out such work is not always affordable.

A closed (or membrane) expander is fixed in a system where the movement of the coolant 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 coolant, and the second is a place for air and nitrogen.

These containers are treated with paint in powder form in order to protect against damage to the walls of the housing under the influence of high temperatures.

On one side 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 a closed-type model makes it possible to automatically change the supply of coolant to the system and the tank itself.

Closed tanks are divided into:

replaceable;
non-replaceable.

Thus, replaceable tanks have a higher cost, but have significant advantages, which include:

the ability to change the membrane if it is damaged or torn;
the opportunity to save on pipes, since there is no need to install a closed tank at the top of the heating system;
replaceable options are responsible for minimal heat losses;
since the coolant does not “come into contact” with oxygen in any way, the pipes and the entire system as a whole are not subject to corrosion;
the membrane can be positioned 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 a flange).

Non-replaceable types of containers are cheaper, but the membrane cannot be changed in them if necessary. This element in the expander is installed as tightly as possible and is securely 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 is outside the normal range).

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

balloon membrane;
diaphragm membrane.

Thus, an expander with a balloon membrane is very durable and reliable. In addition, it has an impressive volume. In this case, the coolant does not come into any contact with the walls of the tank, so the appearance of rust on such products is excluded.

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

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

Materials

Various materials are used in the manufacture of expansion tanks, but the most common are models with a steel body.

Currently, many people, in an effort to save money, construct such units on their own. To do this, they often use sheet materials, which are subsequently assembled into a single structure by welding. You can also use the most unexpected items to make an expansion tank, 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 partition in such units, most manufacturers use high-quality rubber, synthetic rubber, natural butyl rubber or EPDM raw materials. Membrane elements for such units are made from various materials, which during use can easily withstand a wide range of temperatures.

If we consider specific cases, then:

for tanks up to 2 thousand liters, membranes marked EPDM DIN 4807 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 us highlight a few simple tips that will allow the buyer to choose a suitable model of good quality.

Experts recommend choosing membrane or closed containers. Despite the fact that these types of tanks are usually expensive, the heating system that contains them can last a very long time. This is explained by 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 partition is made in closed models.

Listed above are the raw materials that are usually used for their manufacture.

If you are going to use the tank in conjunction with a central heating system, then the membrane rubber should have increased strength characteristics and resistance to high temperatures. This is because 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 purchased for a private heating system, since sudden pressure surges are common for this heating option.
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 the water.

When choosing between non-replaceable and replaceable types of membranes, it is recommended to choose the former, since if a non-replaceable part is damaged, you will have to replace 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 necessary quality certificates. If the product does not have them or they do not want to present them to you, it is better to refuse the purchase.
Don't forget to fill out the 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 and temperature changes. In addition, all elements of the unit (from the housing to the membrane) must be made of high-quality materials.

Where to put it?

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 condition (note that this rule only works if there is one membrane element). If we assume that it will change, then the result will be that in a closed system, a liquid that comes from incomprehensibly is formed, which is fundamentally wrong.

An open heating system is a container with a complex configuration that has special convection currents. Absolutely all components must guarantee the fastest possible rise of the hot coolant to the highest point. In addition, they must provide gravity drainage into the boiler involving 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 specialists 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 must be taken into account that the services of such specialists are in most cases 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 making calculations, it is important to take into account absolutely all the nuances: the volume of the heating system, the specific type of coolant, and even its physical properties.

In the given formula:

C is the total volume of coolant in the system;
Pa min – indicator of the initial absolute pressure in the tank;
Pa max is the highest pressure parameter that can occur in the unit.

If you are afraid of making 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. However, 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 simpler - they estimate the necessary parameters by eye. In this case, the specific capacity of the heating system is equal to 15 l/kW. The result will be approximate values. But keep in mind that this method is only allowed during the feasibility study process.

Before purchasing a tank, of course, you only need accurate calculations.

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 this data is indicated in special reference books on standards for the use of units);
prepare tools such as a wrench, a wrench 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 specialists:

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 matches the connected water supply;
correctly install the required temperature sensors;
calculate the connection of shut-off valves.

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

Mark areas for fastening. Drill the required number of holes needed to secure the bracket. To do this, attach it 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 secure. If everything is done efficiently, then you can install the tank itself, and then secure it with clamps.

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

Absolutely all mechanisms that require adjustment must be in the public domain, and pipes must be located so that they do not create loads 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 at the tank. This valve must be attached in front of the flow pipe.

After this, 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 indicate when you need to stop. After this, water is pumped in using a pump, the pressure is equalized, and the membrane part is brought into a floating state. Then the tank can be considered ready for use. You may need to turn on the system and make sure it is working.

As you can see, the installation and connection diagram of the expansion tank is quite simple. Anyone can cope with such events.

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

Common problems

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

The most common breakdown of such units is the rupture of the membrane part. As a rule, this occurs due to too high pressure (above normal) or uneven loads. Please note that replaceable elements break 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, this often causes water to leak 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 liquid gets on the inner surface of the tank, after which it can become covered with rust 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 occurs with your equipment, it is better for you to seek help from a specialist. Do not attempt to repair damaged cabinet elements yourself, especially if you have never encountered such work before.

There are also cases when the expander boils. Most often, this problem occurs in homemade 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 wiring diameter. The main single-pipe heating circuit is usually installed with a pipe that is no less thin than DN 32.
No slope. After the heating boiler, you need to make a so-called accelerating manifold. To do this, the pipe must be raised to the upper section of the circuit, where the expander is installed. The remaining part of the contour should be laid with a downward slope.

Many users are wondering how to fix such a serious problem without completely dismantling and reinstalling the heating system. The answer is simple - you need to install a circulation pump. This part works great in many systems (especially the 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. To avoid colliding with it, you need to monitor the volume of water.

If you do not replenish it, the resulting evaporation 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 encounter this problem. Experts recommend replacing these elements in special service centers, but it is possible to carry out such work yourself.

This is done as follows.

First you need to disconnect the tank from the heating system.
Next, you need to reduce (reset) the pressure of the gas cavity using the nipple on top of the unit.
Remove the diaphragm flange located next to the nozzle to connect the pipeline. By unscrewing the nut on top of the housing, you need to release the membrane part holder.
Remove the membrane part from the cavity at the bottom of the housing.
Next, you need to examine the surface of the interior of the hull structure. There should be no dirt or rust. If there are any, they must be removed and the surfaces 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 should not be used to ensure that the insides of the unit are protected from corrosion.
Install the membrane element holder into the cavity located at the top of the membrane itself, if such fasteners must be present in the design of a particular device.
Screw the bolt into the retaining element and place the membrane in the housing. The holder must be inserted into the cavity located at the bottom of the housing.
The retaining part must be secured with a nut.
Set the preliminary values for the air pressure 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, this may indicate that you have made a mistake with the selected volume. You may have made the necessary calculations incorrectly.

In order for the pipework to be installed according to all the rules, you need to pay close attention to the main components of the system: the area where the coolant enters directly into the container, as well as the place where it leaves.

To ensure that the water in the expansion tank never boils, choose loop 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 drained the liquid from it in advance.

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

Remember that expansion tanks must be installed exclusively in accordance with the drawn up plan and diagram.

If you doubt your abilities, then it’s better not to take risks - turn to specialists.

The main parameter of the tank is its useful volume, which must exceed the change in the volume of the system liquid as a result of the maximum change in its temperature.

The volume of liquid in the heating system is not constant, since the coolant can expand and contract during operation. Heating of the coolant, and accordingly an increase in its volume at a constant size of the internal space of the heating system, leads to an increase in pressure on the walls of pipelines and heating equipment, which can cause their destruction.

To compensate for changes in the volume of liquid and stabilize the pressure on the internal walls of the components of the heating system, an expansion tank (also known as an expansomat, from the English verb “expanse”, which means “to expand”) is introduced into its circuit. When the coolant expands, its quantity, exceeding the volume of the internal space of the system, enters the expander, and after the temperature drops, it returns back.

How to determine the required expander volume?

The volume of the expander must exceed the value of the required volume, which represents the maximum amount of coolant entering the tank as a result of its heating.

First of all, the total volume of coolant in the system is determined. By summing the internal volume of pipes and cavities of all system elements (boiler, heating radiators, shut-off valves), we obtain the total volume. The amount of liquid in pipelines can be calculated depending on the size of the pipe, using the data in Table 1. The volume of equipment cavities is indicated in the documentation (passport or manufacturer’s catalog) for the product.

Next, knowing the total amount of liquid, determine the required volume of the expander using the data in Table 2. This value is selected depending on the pressure in the system. If the previously calculated value is between two tabular ones, the required tank volume is determined by the larger of the values.

The data in Table 2 is valid if water is used as a coolant. For liquids with a coefficient of thermal expansion different from water, the tabulated value of the total volume is multiplied by a correction factor equal to the ratio of the density of water and the liquid used.

Main types of tanks

There are two main types of expander that are used in the heating system:

open type;
closed type.

Open type expansion tanks They are a single-volume container communicating with the atmosphere. Such a tank is installed at the highest point of the heating system, which is necessary to ensure the natural return of liquid to the pipeline when its temperature decreases.

Open type expander.

Closed expanders made in the form of a sealed vessel, part of which is filled with liquid, and part with air or gas under a certain pressure. When heated, the liquid enters the expansion chamber, and the gas is compressed. When the liquid cools, it returns to the system, and the difference in volume is filled with gas.

Open type expansion tank

In addition to the main functions (volume compensation, pressure stabilization), an open-type expanzomat serves to replenish water if there is a slight leak in the system and to remove air from the system.

Open expanders have a rectangular or cylindrical shape and are made of sheet steel or polymer materials. The installation of an open type expansion tank in a heating system is carried out at its highest point, which requires an increase in the total length of the heating pipelines. The tank is equipped with a lid to protect the coolant from contamination and provide access inside during maintenance.

The place to place the open expander can be an attic, a stairwell, or a specially equipped box installed on the roof of the house. If the height of the house allows you to install the expander inside the residential part of the building, it can be placed in a bathroom or utility room. Containers located outside the heated part of the house must be insulated to reduce heat loss in the system.

Operating principle and installation features

To prevent water from stagnating in an open tank, it is necessary to ensure its circulation. To do this, a circuit consisting of an expansion and circulation pipe is installed between it and the main heat pipeline, the hole of the latter being located slightly lower in the tank (about 50 mm). For effective water circulation, the circuit is cut in before entering the pump (if the system operates with forced circulation), installed on the return line. Circulation allows air bubbles to be removed from the system into the atmosphere.

It should be noted that the above is true when installing an expander in a heating system with forced circulation of coolant!

In a system with natural circulation, to ensure unimpeded escape of air bubbles, the expander is connected at the highest point of the supply pipeline.

In the area of the minimum coolant level mark, a control pipe comes out of the tank, and at the maximum level there is an overflow pipe, designed to drain excess liquid. Checking the level can be done by simply opening the tap on the control pipe. If water comes from the tap, it means that its level in the tank exceeds the minimum mark. For this purpose, lower and upper level relays can be installed, giving a light or sound signal when there is a danger of the water level decreasing to a minimum value or approaching the overflow point.

The useful volume of the expander, equal to the area of its base multiplied by the height between the minimum and maximum levels, is equal to the increase in the amount of water as a result of thermal expansion. It must be equal to or exceed the required value calculated using tables 1 and 2.

Advantages and disadvantages

The main advantages of an open type expander:

simplicity of design, which implies relatively low cost;
performs the function of relieving pressure and removing air from the heating system.

Disadvantages of open expansion tanks:

special installation conditions that require the installation of additional pipelines;
high heat losses and the need for thermal insulation;
direct contact with the atmosphere, which can cause corrosion of steel elements of the system;
due to the possibility of evaporation, the system requires periodic replenishment of the coolant.

It should be noted that, due to the above disadvantages, open tanks are used less and less in heating systems of residential buildings, being inferior in popularity to closed expanders.

Closed expansion tank

Unlike open expansion tanks, a closed expansion tank is not connected to the atmosphere. It is a sealed steel vessel, partially filled with liquid, and partially filled with inert gas pumped through a special valve. Depending on the method of dividing the internal volume, closed tanks are divided into:

membraneless;
membrane

Membraneless

In membraneless expanders, the coolant is in direct contact with the gas, since they do not have a mechanical separation of the internal space. To maintain a given pressure, a compressor or a gas cylinder located outside is used. Pressure control and gas supply are carried out automatically.

Membraneless tanks were widely used at a time when rubber membranes had low service life and required frequent replacement. They could work without a membrane, but the need for a compressor or cylinder complicated the design. Currently, closed tanks with a separating membrane are widely used.

Membrane

In modern expander designs, liquid and gas are separated using a flexible membrane. There are extenders with:

disc membrane (diaphragm);
pear-shaped (balloon) membrane.

The disc-shaped one is mounted in the middle part of the tank and has a shape close to a hemisphere. Depending on the temperature of the water, it takes a convex or concave shape.

The pear-shaped one follows the shape of the vessel and is fixed at opposite ends of the container. A feature of these cylinders is the absence of contact of the coolant with the walls, since the liquid fills a flexible membrane, and gas is pumped between it and the metal walls. This protects the structure from corrosion and increases service life. This design allows for replacement of the membrane, while the design of diaphragm tanks does not allow this.

Modern expanders use butyl and ethylene propylene membranes, which are characterized by increased durability. Previously, rubber was used for these purposes, which has a shorter service life and is currently not used.

Advantages and disadvantages of membrane tanks

The disadvantages of membrane expanders are:

high price;
the need for periodic pumping of gas or air;
the need to control pressure in the system.

Among the advantages are:

compact dimensions;
minimal heat loss, no need for thermal insulation;
absence of direct contact of the coolant with the atmosphere (evaporation), which reduces the risk of formation and spread of corrosion and the need to recharge the system;
ability to work at high pressure;
Possibility of installation almost anywhere.

Selecting a membrane expander

The main parameter of the membrane tank is the required volume of liquid in the system, which must be pre-calculated using tables 1 and 2. The tank must have a volume equal to or greater than the obtained value.

In addition to the traditional oval shape, many manufacturers produce flat expanders with a diaphragm. This tank is more compact and can be installed in the space between the wall and the interior decoration of the room without taking up useful space.

The main working part of a modern closed tank is the membrane, the parameters and quality of which determine its service life. The main characteristics of the membrane are:

operating temperature and pressure range;
material;
diffusion stability.

Membrane tanks for heating systems are painted red, while those used in water supply systems are painted blue. The membranes of heating system expanders are subject to lower sanitary and hygienic requirements.

Rules for installing closed expanders

Installed heating expander.

The installation of a closed expansion tank in a heating system can be carried out at any point in the circuit, but the optimal installation is in front of the circulation pump (for a heating system with forced circulation of coolant).
Installation is allowed in any position, but the option with a top liquid supply is preferable, as it allows air bubbles to escape naturally. This installation will ensure the tank remains operational even if the membrane ruptures.
If during operation of the heating system it turns out that the volume of the installed tank is not enough, instead of replacing it, it is more rational to install an additional one of the required size.
When switching from water to another coolant, you may need to replace the expansion tank with a larger one. It is possible to install an additional expander.
Some models of heating boilers have a built-in expansion tank; in this case, installation of an additional one is not required.
Installing a closed expander in a heating system with natural circulation requires the installation of an “auto-vent” (automatic float valve) at the highest point of the system to automatically release air when the system is filling and during boiler operation.

Expander operation

Maintaining a membrane-type expansion tank in working condition includes:

regular visual inspection for corrosion;
checking the integrity of the membrane;
checking air (gas) pressure.

Maintenance of open-type tanks involves an external inspection of the condition of the body and thermal insulation, as well as checking the liquid level, which should not fall below the minimum level.

Expansion tank on bracket.

The correct selection and installation of an expansion tank in the heating system is one of the components of reliable, uninterrupted and safe operation of the entire heating system of a residential building. Today, a closed-type expansion tank with a membrane-diaphragm is more often installed, combining an affordable price and a high level of ease of use.

When arranging a heating system, you have to take into account many nuances associated with its individual elements, including not only radiators and a heat generator. An integral part of an effective heating network is the expansion tank. This device seems primitive, but the quality of heating largely depends on it. When installing a tank, many mistakes are made that negatively 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 installing the tank 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 the 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 capsule container, divided into two parts by a rubber membrane. Diaphragm expansion tanks have the following installation requirements:

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

Small containers are mounted on the wall using 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 the pipes to the top of the element, leaving the air chamber at the bottom, which will help to easily remove air from under the membrane. However, the most correct solution would be to position 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 located at the bottom, then even if the membrane element wears out, it will take a lot of time for the air to penetrate the coolant. If the tank is positioned 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 to 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 connection point is outlined. Experts recommend connecting buried tanks on the return line. However, there is no place for the container just before the entrance to the heat generator; the ideal option is before 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 liner, then do not forget to equip the pipe with a ball valve or fitting to timely block access to the container and allow it to be quickly removed 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 adjustment, which consists of creating optimal pressure in the air chamber. Without proper implementation of this stage, it is impossible to avoid hydraulic shocks that occur when the membrane pushes out excess cooling coolant. Setup work is performed in the following order:

the system is filled with cold water;
Air pockets 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.

Setup is the final stage, after which the heating network can be launched. Now the pressure in the tank will change smoothly both when heating and cooling the coolant, without causing any problems. Remember that errors when installing a compensating tank are not immediately apparent, but make themselves felt at the most inopportune moment - at the height of the heating season.

In fact, installing an expansion tank is not a very complicated operation. To carry it out, you don’t even need professional tools - the arsenal of a thrifty home craftsman will be enough. However, to insert a container into the system and its subsequent configuration, you need to pay attention to all the little details, ignoring which can be fatal. Only in this way will the installed device last a long time and not cause any trouble!