When planning to create a water heating system in own home, the owner is faced with a choice of several options. The list of the most important questions includes the type of system (will it be open or closed type), and what principle will be used to transfer coolant through pipes ( natural circulation due to the action of gravitational forces, or forced, requiring the installation of a special pump).

Each of the schemes has its own advantages and disadvantages. But still, nowadays preference is increasingly given to a closed system with forced circulation. This scheme is more compact, easier and faster to install, and has a number of other operational advantages. One of the main distinctive features is a completely sealed expansion tank for closed-type heating, the installation of which will be discussed in this publication.

But before purchasing an expansion tank and proceeding with its installation, you need to at least become familiar with its structure, operating principle, as well as which model will be optimal for specific system heating.

IN What are the advantages of a closed heating system

Although V Lately Many modern devices and systems for space heating have appeared; the principle of heat transfer through a liquid with high heat capacity circulating through pipes is, without a doubt, remains the most widespread. Water is most often used as a carrier of thermal energy, although in some circumstances it is necessary to use other liquids with a low freezing point (antifreeze).

The coolant receives heat from the boiler (ovens with water circuit) and transfers heat heating devices(radiators, convectors, “warm floor” circuits) installed in the premises in the required quantity.

How to decide on the type and number of heating radiators?

Even the most powerful boiler will not be able to create a comfortable atmosphere in the premises if the parameters of the heat exchange points do not correspond to the conditions of a particular room. How to do it right - in a special publication on our portal.

But any liquid has common physical properties. Firstly, when heated, it increases significantly in volume. And secondly, unlike gases, this is an incompressible substance; its thermal expansion must be compensated in some way by providing free volume for this. And at the same time, it is necessary to ensure that as it cools and decreases in volume, air does not enter the pipe contours from the outside, which will create a “plug” that prevents the normal circulation of the coolant.

These are the functions that the expansion tank performs.

Not yet in private construction, there was no particular alternative - an open expansion tank was installed at the highest point of the system, which completely coped with the tasks.

1 – heating boiler;

2 – supply riser;

3 – open expansion tank;

4 – heating radiator;

5 – optional – circulation pump. In this case, a pumping unit with a bypass loop and a valve system is shown. If desired or if the need arises, you can switch forced circulation to natural circulation, and vice versa.

A closed system is completely isolated from the atmosphere. A certain pressure is maintained in it, and the thermal expansion of the liquid is compensated by installing a sealed tank of a special design.

The tank in the diagram is shown pos. 6, embedded in the return pipe (item 7).

It would seem - why “fence the garden”? A regular open expansion tank, if it fully copes with its functions, seems to be a simpler and less expensive solution. It probably doesn’t cost much, and besides, with certain skills, it’s easy to make and weld it yourself from steel sheets, use an unnecessary metal container, for example, an old can, etc. Moreover, you can meet examples applications old plastic cans.

Does it make sense to spend money on purchasing a sealed expansion tank? It turns out that there is, since a closed heating system has many advantages:

• Complete tightness absolutely eliminates the process of evaporation of the coolant. This opens up the possibility of using, in addition to water, special antifreezes. The measure is more than necessary if country house V winter time They do not use it all the time, but only occasionally, occasionally.
• In an open heating system, the expansion tank, as already mentioned, must be mounted at the highest point. Very often such a place becomes unheated attic. And this entails additional efforts to thermally insulate the container so that even in the most severe frosts the coolant in it does not freeze.

And in a closed system, the expansion tank can be installed in almost any area. The most appropriate installation location is the return pipe directly in front of the boiler entrance - here the tank parts will be less exposed to temperature effects from the heated coolant. But this is by no means a dogma, and it can be mounted in such a way that it does not create interference and does not disharmonize its appearance with the interior of the room, if, say, the system uses a wall-mounted boiler installed in the hallway or in the kitchen.

• In the open expansion tank The coolant is always in contact with the atmosphere. This leads to constant saturation of the liquid with dissolved air, which causes increased corrosion in the circuit pipes and radiators, and increased gas formation during the heating process. Aluminum radiators are especially intolerant of this.
• A closed heating system with forced circulation is less inert - it warms up much faster when starting up, and is much more sensitive to adjustments. Completely unjustified losses in the area of ​​the expansion tank are eliminated open type.
• The temperature difference in the supply and return pipes in the connection currents with the boiler is less than in an open system. This is important for the safety and longevity of heating equipment.
• A closed scheme with forced circulation to create circuits will require pipes of smaller diameter - there is a benefit both in the cost of materials and in simplifying installation work.
• An open-type expansion tank requires control to prevent overflow when filling, and to prevent the liquid level in it from falling below a critical level during operation. Of course, all this can be solved by installing additional devices, for example, float valves, overflow pipes, etc., but these are unnecessary complications. In a closed heating system, such problems do not arise.
• And finally, such a system is the most universal, as it is suitable for any type of battery, allows you to connect underfloor heating circuits, convectors, thermal curtains. In addition, if desired, you can organize hot heat supply by installing an indirect heating boiler into the system.

Of the serious shortcomings, only one can be mentioned. This — mandatory “safety group”, including control and measuring instruments (pressure gauge, thermometer), safety valve and automatic air vent. However, this is more likely no no wealth, and the technological cost that ensures safe operation heating systems.

In a word, the advantages of a closed system clearly outweigh, and spending on a special sealed expansion tank looks completely justified.

How does an expansion tank for closed heating work and how does it work?

The design of an expansion tank for a closed type system is not very complicated:

Usually the entire structure is housed in a stamped steel body (item 1) cylindrical(there are tanks in the form of “tablets”). For production, high-quality metal with an anti-corrosion coating is used. The outside of the tank is covered with enamel. Products with a red body are used for heating. (There are tanks of blue color– but these are water accumulators for the water supply system. They are not designed for elevated temperatures, and all their parts are subject to increased sanitary and hygienic requirements).

On one side of the tank there is a threaded pipe (item 2) for insertion into the heating system. Sometimes fittings are included in the package to facilitate installation work.

WITH opposite side there is a nipple valve (item 3), which serves for preliminary creation required pressure V air chamber.

Inside, the entire cavity of the tank is divided by a membrane (item 6) into two chambers. On the side of the pipe there is a chamber for coolant (item 4), on the opposite side there is an air chamber (item 5)

The membrane is made of elastic material with a low diffusion rate. It is given a special shape, which ensures “orderly” deformation when the pressure in the chambers changes.

The principle of operation is simple.

• In the initial position, when the tank is connected to the system and filled with coolant, a certain volume of liquid enters the water chamber through the pipe. The pressure in the chambers is equalized, and this closed system acquires a static position.
• As the temperature rises, the volume of coolant in the heating system expands, accompanied by an increase in pressure. Excess fluid enters the expansion tank (red arrow), and its pressure bends the membrane (yellow arrow). In this case, the volume of the coolant chamber increases, and the air chamber correspondingly decreases, and the air pressure in it increases.
• With a decrease in temperature and a decrease in the total volume of coolant overpressure in the air chamber helps to move the membrane back (green arrow), and the coolant moves back into the heating system pipes (blue arrow).

If the pressure in the heating system reaches a critical threshold, then the valve in the “safety group” should operate, which will release excess liquid. Some expansion tank models have their own safety valve.

Different tank models may have their own design features. So, they can be non-separable or with the ability to replace the membrane (a special flange is provided for this). The kit may include brackets or clamps for mounting the tank on the wall, or it can be provided with stands - legs for placing it on the floor.

In addition, they may differ in the design of the membrane itself.

On the left is an expansion tank with a membrane diaphragm (it has already been discussed above). As a rule, these are non-separable models. A balloon-type membrane (picture on the right), made of elastic material, is often used. In fact, it itself is a water chamber. As pressure increases, such a membrane stretches, increasing in volume. It is these tanks that are equipped with a collapsible flange, which allows you to independently replace the membrane in the event of its failure. But the basic principle This doesn't change the work at all.

Video: installation of Flexcon brand expansion tanks FLAMCO»

How to calculate the required parameters of the expansion tank?

When choosing an expansion tank for a specific heating system, the fundamental point should be its working volume.

Calculation using formulas

You can find recommendations to install a tank, the volume of which is approximately 10% of the total volume of coolant circulating through the system circuits. However, a more accurate calculation can be made - there is a special formula for this:

Vb =Vwith ×k / D

The symbols in the formula indicate:

Vb– required working volume of the expansion tank;

Vс– the total volume of coolant in the heating system;

k– coefficient taking into account the volumetric expansion of the coolant during heating;

D– efficiency coefficient of the expansion tank.

Where to get the initial values? Let's look at it one by one:

1. Total system volume ( VWith) can be determined in several ways:

• You can determine from the water meter which overall volume will fit when filling the system with water.
• Most exact way, which is used when calculating the heating system, is the summation total volume pipes of all circuits, the capacity of the heat exchanger of the existing boiler (it is indicated in the passport data), and the volume of all heat exchange devices in the premises - radiators, convectors, etc.
• The simplest method gives a completely acceptable error. It is based on the fact that to provide 1 kW of heating power, 15 liters of coolant are required. Thus, the rated power of the boiler is simply multiplied by 15.

2. The value of the coefficient of thermal expansion ( k) is a tabular value. It varies nonlinearly depending on the heating temperature of the liquid and the percentage of antifreeze in it ethylene glycol additives The values ​​are shown in the table below. The heating value line is taken from the calculation of the planned operating temperature of the heating system. For water, the percentage value of ethylene glycol is taken as 0. For antifreeze - based on the specific concentration.

Coolant heating temperature, °C	Glycol content, % of total volume
	0	10	20	30	40	50	70	90
0	0.00013	0.0032	0.0064	0.0096	0.0128	0.016	0.0224	0.0288
10	0.00027	0.0034	0.0066	0.0098	0.013	0.0162	0.0226	0.029
20	0.00177	0.0048	0.008	0.0112	0.0144	0.0176	0.024	0.0304
30	0.00435	0.0074	0.0106	0.0138	0.017	0.0202	0.0266	0.033
40	0.0078	0.0109	0.0141	0.0173	0.0205	0.0237	0.0301	0.0365
50	0.0121	0.0151	0.0183	0.0215	0.0247	0.0279	0.0343	0.0407
60	0.0171	0.0201	0.0232	0.0263	0.0294	0.0325	0.0387	0.0449
70	0.0227	0.0258	0.0288	0.0318	0.0348	0.0378	0.0438	0.0498
80	0.029	0.032	0.0349	0.0378	0.0407	0.0436	0.0494	0.0552
90	0.0359	0.0389	0.0417	0.0445	0.0473	0.0501	0.0557	0.0613
100	0.0434	0.0465	0.0491	0.0517	0.0543	0.0569	0.0621	0.0729

3. Expansion tank efficiency coefficient value ( D) will have to be calculated using a separate formula:

D = (Qm – Qb)/(Qm + 1 )

Qm— maximum permissible pressure in the heating system. It will be determined by the response threshold of the safety valve in the “safety group”, which must be indicated in the product passport.

Qb— pre-pumping pressure of the air chamber of the expansion tank. It may also be indicated on the packaging and in the product documentation. It is possible to change it - paging using car pump or, conversely, bleeding through the nipple. It is usually recommended to set this pressure within 1.0 – 1.5 atmospheres.

Calculator for calculating the required volume of the expansion tank

To simplify the calculation procedure for the reader, the article contains a special calculator in which the indicated dependencies are included. Enter the requested values, and after pressing the “CALCULATE” button you will receive the required volume of the expansion tank.

Enter the requested values ​​and then click the "CALCULATE" button

Specify the nameplate power of the heating boiler, kW

Liters per kilowatt

Select from the table and indicate the value of the coefficient of thermal expansion of the coolant (rounded to thousandths)

Specify the maximum pressure in the heating system (safety valve response threshold) Bar (atm.)

Specify the pre-injection pressure of the air chamber of the expansion tank, Bar (atm.)

Just one

The obtained value is minimal - a model with the closest indicators is selected based on it. In this case, rounding is carried out only upward - additional volume will not be superfluous.

And finally, from the model range of calculated volumes presented for sale, you can choose the most optimal option, based on the intended location of the expansion tank - mounted to the wall or placed on the floor.

There is one more nuance. Some heating boilers have their own built-in expansion tank. This does not mean that there is no need to carry out calculations - it happens that the volume of the built-in tank is clearly not enough. In this case, you will have to purchase and install an additional one, with a working volume equal to the difference in the calculated indicators for the entire system and the parameters in the built-in tank.

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

Do-it-yourself expansion tank for closed-type heating

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

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

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

From the tap is coming connecting section of the pipe (item 9) to the tee. Its length and configuration (number of bends or turns) of great importance they don’t - but it’s usually done along the shortest and most convenient path from the installation site of the tank to the return pipe.

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

Illustration	Brief description of the operation performed
	The tank was taken out of the factory packaging and prepared for work. necessary tools and accessories.
	If necessary, an adapter is packed onto the threaded pipe of the expansion tank. It is important to achieve extremely reliable sealing of the connections. It is best to pack tow using Unipack paste or using a special thread-sealing thread (cord) impregnated with a sealing compound (as shown in the figure)..
	The adapter is tightened, and you can proceed to installing the tap. It is worth noting right away that in the example shown there was a flaw - the master did not install a detachable connection - “American” between the tap and the tank. That is, if it is necessary to dismantle the tank with the tap closed, this will be very difficult to do. A recommendation to all installers is not to forget about this point.
	The thread is wound to wrap the tap,...
	... the tap is put in place and tightened tightly. You should immediately ensure that the “lamb” is in a position convenient for use after placing the tank on the wall.
	A transition is mounted from the tap to a pipe of the required configuration, in accordance with the drawn up diagram general installation expansion tank. Essentially, this part of the work is finished.
	Now you can check the pressure in the air chamber of the expansion tank. On its opposite side there is a nipple - almost exactly the same as on car wheels. In many models it is covered with a special plastic cap, which, if necessary, access to the valve is simply unscrewed.
	You can check the pressure with a car pressure gauge. If it exceeds the values ​​that were used when calculating the system, then it can be released to the required level by pressing the valve stem. If there is insufficient supply, you will have to pump it up - a car pump is quite suitable for this.
	In the variant under consideration, the tank already has devices for its placement, even in two versions - legs for installation on a horizontal surface (blue arrows) and a mounting panel for hanging on the wall (yellow arrow). The tank is mounted in the chosen location, and then connected by a section of pipe to a tee embedded in the return line. At this point the installation can be considered complete.
	Another version of the tank, which is not on the body structural elements for fastening at the installation site. But they are usually included as separate parts in the delivery kit.
	Usually this is a bracket - a mounting pad for fastening to the wall, and a long screw band clamp.
	The collar of the clamp is straightened and threaded through the slots of the mounting area.
	All this is done in such a way that the protruding side of the tank falls into a special groove in the mounting platform (shown by arrows), and the clamp is higher than the side.
	After installing the tank in the mounting area, the ends of the clamp are connected, first tightened by hand...
	.. and then - all the way, using a screwdriver or wrench.
	In this form, the tank will be ready to hang on the wall.
	Installation of plumbing fittings to the cistern pipe is carried out in the same order as mentioned above.
	The nipple can be located openly, only with a dustproof plastic cap. Checking the pressure and pumping, if necessary, is no different from the previously considered option.
	By the way, tanks usually come from the factory with a preset pressure in the air chamber, and you can immediately select the required parameter. It is indicated on the packaging and in the technical documentation of the product. Further installation of the tank is carried out in the already known order - installation on the wall in the selected location and connection with a pipe with a tee.

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

Video: inserting an expansion tank into the contour of polypropylene pipes

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

A very popular series among all others in the BAXI line. The 4th generation boiler with a capacity of 24 kilowatts is available in various versions: open and closed camera combustion. Boilers with a closed combustion chamber and forced smoke removal are designated by the letter “F” in the name. Turbocharged Baxi boilers are the most popular and are often used in organizing apartment heating Therefore, we will consider the issues of using an expansion tank in the heating system using the example of this boiler model.

When organizing heating systems can be used various options, but recently closed systems have become more popular, in which the coolant moves due to the operation of a circulation pump. Gas-burner heats water (or antifreeze) in the primary heat exchanger, and the pump pumps it through a radiator system, transferring heat to the rooms.

At the same time, for normal circulation of the coolant, the system must be completely filled with water, and since the liquid tends to expand when heated, it is necessary to somehow compensate for the increase in volume. This is why expansion tanks are provided in heating systems.

The diagram shows a system in which the boiler acts exclusively as a heater. In household wall-mounted boilers ECOFOUR expansion tank and circulation pump are already built-in, which is why such boilers are convenient to use in small apartments.

Design and location of the BAXI expansion tank

Expansion tank baxi eco four 24 – a round red tank, which is located on back wall boiler The built-in expansion tank baxi with a volume of 6 liters is divided into two parts by an elastic membrane, one part is connected to the heating system, the second is pumped with air. Therefore, when the heating system heats up, the increasing volume of liquid overcomes the resistance of the membrane and fills the vacated volume of the tank, and when it cools, the membrane tends to move to its original position and pushes the liquid back into the heating system. Thus, the pressure in the heating system remains practically unchanged during operation.

What should be the pressure in the expansion tank of a BAXI double-circuit boiler?

If you open the instructions, it indicates the pressure in the expansion tank is 0.5 bar, but this is the minimum value, correct - the pressure should be about 20% less than the pressure in the heating circuit at room temperature coolant.

Based on the fact that for most systems the recommended filling pressure is in the range of 1.2 to 1.5 bar, we obtain the required pressure in the air cavity of the expansion tank equal to 0.8-1 bar. Experts usually recommend setting the pressure in the expansion tank BAXI tank equal to 1 bar.

Do I need an expansion tank for a baxi wall-mounted gas boiler?

The volume of the built-in expansion tank of the baxi boiler is indicated in the characteristics and for the ECOFOUR series it is 6 liters. To answer the question of its necessity in a separate heating system, you need to know the total volume of this system.

Calculating it is not so difficult: the filling volume of the boiler and radiators is in their characteristics, and the filling volume of pipelines can be calculated by knowing their diameter and total length. Water, after heating by 80 degrees Celsius, will increase in volume by approximately 4-5%, therefore, the recommended volume of the expansion tank is 8% of the total volume of the heating system if filled with water and 12% if antifreeze is used as a coolant (thermal coefficient antifreeze expansion is greater). Thus, a standard expansion tank will be sufficient for a heating system with a volume of up to approximately 75 liters when using water and a volume of up to 50 liters when using antifreeze liquid.

These figures are conditional (with a margin) and when selecting the capacity of the expansion tank, you must be guided by the design calculations of a specific heating system, or the manufacturer’s recommendations.

In most cases, the built-in boiler tank is quite sufficient and the decision to use a separate additional tank is made by specialists at the design stage.

How to pump air into the expansion tank of a Baxi gas boiler?

Pumping up the expansion tank should only be done when the boiler is empty!

Therefore you need to do the following:

Turn off the heating system taps

Drain the water from the boiler through the drain valve

Inflate the tank to the required pressure

Close the drain valve

Feed the heating system through the make-up tap

Open the heating circuit taps

The air cavity of the expansion tank is equipped with a valve for carrying out technical

service. The valve design is a regular car nipple, so the easiest way to pump the expansion tank of a baxi boiler is to use a tire pump - manual or electric car. The latter is convenient because it has a pressure gauge to control the pressure, but often the boiler is located in cabinets or niches and it is not always convenient to get to it, so it is preferable to pump it up with a hand bicycle pump, and then check the pressure with a car pressure gauge and, if necessary, bleed off excess.

Malfunctions of expansion tanks

Checking the pressure of the expansion tank is included in the list of annual procedures Maintenance and if it is followed there will be no problems, but if neglected, it can give the owner unpleasant surprises:

the pressure in the air chamber gradually decreases and with each refill of the boiler the tank fills more and more with water and gradually ceases to perform its function. In this case, the membrane is so pressed against the wall of the air part of the tank that it can be damaged by the valve spool and the tank will have to be replaced.

The heating circuit pressure is at the permissible limit, the expansion tank has not been serviced - there is no pressure in it. When the heating system cools down, the volume of liquid decreases, the pressure drop is not compensated for by anything - the boiler stops due to an emergency. This situation may arise, for example, when long work boiler in DHW mode or power outage.

the owner of the boiler often has to top up the boiler for no apparent reason, for example, while hot water is being used - the pressure on the pressure gauge drops and the boiler stops by mistake - the owner tops up. Since thermal expansion is not compensated by anything, with further heating of the coolant, excess pressure is released through the safety valve. Some users set the reset and simply do not notice this situation. Frequently refilling the boiler with untreated water is detrimental to the heat exchanger!

Baxi boiler pressure drops when hot water is turned on

Sometimes, users encounter a problem when the pressure drops when turned on hot water in a baxi boiler. This problem It may just be due to insufficient pressure in the expansion tank. The fact is that when the boiler switches to the hot water preparation mode, the circulation pump pumps the liquid in a small circle, i.e. only inside the boiler itself - through a secondary plate heat exchanger. In this case, the heating circuit actually does not heat up and the coolant begins to cool, the volume decreases and in the absence of compensating pressure in the expansion tank, the pressure of the heating system may drop and the boiler will be.

In such a situation, you can also consider the possibility of a breakdown of the heat exchanger itself (a gap between the plates) and water entering from the heating circuit into DHW system, but this is easy to check. To check you need to turn off the supply cold water into the boiler and open any drain valve. If under such conditions from the tap water is coming- it is obvious that this is coolant from the heating circuit and the heat exchanger needs to be replaced.

Remember timely service gas boiler will help avoid such situations and increase the service life of the unit.

When performing work on designing heat supply systems and selecting functional elements heating circuit It is important to agree on the parameters of the equipment being installed. The stable and trouble-free operation of the heating circuit is influenced by the pressure in the closed-type heating expansion tank, the correct adjustment of which allows you to compensate for temperature changes. The expander, which regulates the volume of coolant and ensures the integrity of lines and equipment, should be correctly selected and professionally installed.

How pressure in the heating expansion tank stabilizes the operation of the heating system

When thinking about creating an efficient heating system, not everyone has an idea what the pressure is in the expansion tank of a gas boiler and how the expansion tank works.

The principle of operation of the compensation tank is quite simple:

1. An increase in coolant temperature causes an increase in volume.
2. At the same time, the fluid pressure in the closed circuit increases.
3. The expansion tank accepts excess liquid.
4. Pipe pressure and heating equipment quickly stabilizes.
5. The water in the boiler expansion tank is gradually cooled and returned through the pipes.

The device is a mandatory element for maintaining a constant temperature in a private house, apartment or industrial facility. The tank performs the following functions:

• compensates for the volumetric expansion of the liquid. As the temperature increases, the volume of liquid filling the closed loop, - the excess is absorbed by the expansion tank;
• smoothes out surges caused by the cyclic operation of the feed pump. The device reduces the impact of water hammer on equipment and lines and ensures stable operation.

The working capacity of the expansion chamber performs the function of a heating circuit damper and allows:

• ensure long service life of heating equipment;
• compensate for the effects of temperature changes;
• guarantee the safe operation of the elements and ensure their high reliability.

Thanks to the ability to pump air into the working capacity of the expander, stable and trouble-free heating operation is maintained. The device is a mandatory element of the heating circuit.

Types of units

Damper tanks are a necessary element of various heating circuits:

• open. The coolant circulates naturally without the use of special pumps. The design of the expander allows, if necessary, to add evaporating water manually or using the supply line into an open container. The constant process of evaporation requires regular renewal of the liquid;
• closed. Sealed heating circuits are equipped with closed tanks, which are a sealed container with an elastic membrane located in the middle. Part is occupied by the air. The other part is filled with coolant, which, as the volume increases, acts on the membrane, reducing the capacity of the air chamber.

Previously popular open tanks, used in systems with gravity circulation, were distinguished by their simplicity of design, low cost and ease of manufacture. The tank was a steel tank, equipped with a lid, as well as fittings for connection to the heating pipes and drain line.

Today, open-type devices are rarely used, which is associated with certain disadvantages. Weak spots:

• direct contact of water with air, which causes accelerated destruction of the housing as a result of corrosion processes;
• the need for installation only in the highest part of the circuit, which is often located in a cold room;
• the need for constant renewal and control of the volume of coolant that regularly evaporates during operation;
• reduced efficiency of the damper unit, which requires reliable thermal insulation.

Sealed structures used in closed systems heat supply, superior in operational characteristics open tanks. Peculiarities:

• increased resistance to corrosion;
• no need for constant level monitoring;
• stable operation without regular addition of water;
• impossibility of contact of the coolant with the air;
• ease of self-installation.

Let us dwell in more detail on closed-type expansion tanks that have proven themselves with positive side in heat supply systems with forced liquid supply. They effectively compensate for pressure differences that occur as the volume of liquid increases.

The following types of tanks are used:

• membraneless. The design of the device is characterized by the absence of an elastic membrane. For the tank to function, it is necessary to connect a cylinder or equipment that pumps air;
• membrane Home design feature is the presence of a rubber damper that separates the coolant from the air, as well as the possibility of replacing the elastic element.

Membraneless devices were common before the development of the production of reliable rubber membranes, characterized by durability and an increased safety margin. Membraneless devices are characterized by:

• the absence of a rubber gasket that prevents contact of antifreeze or water with the gaseous environment;
• stability of operation only with constant monitoring of the air supply and ensuring its constant pressure.

Membrane units are quickly replacing membrane-free devices, which cannot compete in terms of performance. The elastic membrane separating liquid and gas differs in shape and is made:

• in the form of a hemisphere. The disc-shaped element is permanently fixed and under load takes the radius shape of a sphere;
• in the form of a balloon. A pear-shaped membrane mounted on a flange, when loaded, tries to replicate the shape of the vessel. If necessary, it can be easily dismantled.

Components of disc tanks:

• a vertical housing made of two hermetically connected parts;
• a rubber plate permanently installed between the housing elements;
• lower fitting intended for connection with heating pipes;
• top nipple that allows you to fill the top of the tank with air.

As the volume increases, the coolant fills the container and acts on the air through a disc-shaped membrane. When the heating temperature decreases, the volume of liquid that is squeezed out by air decreases accordingly. Adjustment is carried out by pumping air through the nipple or opening it.

Pear-shaped membrane reservoirs include the following elements:

• a container with a flange mount for fixing the rubber membrane;
• a spherical coolant chamber fixed on the flange;
• a fitting that allows you to connect the damper element to the lines;
• valve that regulates air supply.

Water fills the rubber container, which protects the housing from corrosion. This has a positive effect on its durability.

The main differences between this type of tank:

• lack of contact of the coolant with the metal of the housing;
• possibility of dismantling the rubber chamber;
• small dimensions;
• operation without recharge;
• functioning under increased load;
• minimal amount of heat loss;
• tightness.

To ensure stable operation, you should monitor the pressure gauge readings and periodically pump in air.

How to choose an expressomat

Choosing an expansion tank is a serious task, the solution of which must be approached with a high degree of responsibility. When choosing a compensator, it is important to consider the following points:

• design;
• body material;
• product size;
• lifetime.

In specialized stores, experienced consultants will help you purchase the necessary expander and tell you what pressure in the expansion tank of the heating system needs to be maintained.

How does the pressure in the expansion tank of the heating system affect the volume - calculation method

The main characteristic of the unit is the capacity of the tank. The working volume is directly proportional to the pressure and must exceed the amount of coolant displaced during thermal expansion.

The capacity of the tank depends on the type of liquid used as a coolant. To determine the capacity of the damper, the following data is taken into account:

• the volume of the tank is equal to the amount of water in the heating system multiplied by a factor of 1.15;
• the use of antifreeze requires an increased volume of the reservoir, calculated taking into account a factor of 1.2.

The total volume of coolant circulating in the circuit is determined by adding the capacity of the constituent elements:

• pipes;
• batteries;
• boiler

Having calculated the total volume of the coolant, it is necessary to multiply the resulting value by the coefficient corresponding to the specific liquid. So, for a heating system with a total volume of 100 liters, a compensating tank with a working capacity of 15 liters is needed for water and 20 liters when using antifreeze.

For the increased load created by the excess coolant volume, an increased working volume of the tank is required.

Installation and configuration of an expansion tank in a heating system

When installing and connecting the expansion tank, you must follow the manufacturer’s recommendations and take into account the following factors:

• using open system the container is installed at the maximum elevation;
• in a closed circuit, the reservoir is connected after the circulation pump.

Sequence of actions for installing a tank for a closed circuit:

1. Define comfortable spot installation on the supply line.
2. Check the operating pressure in the tank.
3. Carry out installation, taking into account the increase in weight when filled with liquid.
4. Connect the damper device to the heating pipes.

When installing, you need to consider the following nuances:

• distance from the boiler room;
• ease of access for maintenance;
• strength of container fastening.

Check the capacity as follows:

1. Run heating system with the tank valve closed.
2. Supply coolant to the working chamber of the tank at 1 atm.
3. Check the pressure drop, which should be 0.1-0.2 atm.

This indicates the absence of problems and stable functioning of the system. Correct placement and adjusting the tank promotes normal operation and facilitates maintenance activities.

How to adjust the pressure in the heating expansion tank - maintenance features

When servicing the device, it is necessary to ensure that the pressure in the tank is 0.2 atm less than the total load in the circuit.

Perform adjustment operations according to the following algorithm:

1. Disconnect the device from the system.
2. Drain the water from it.
3. Connect the pressure gauge to the nipple.
4. Check the pressure gauge readings.
5. If necessary, inflate the container using a compressor.

During maintenance, also check:

• presence of damage to the body;
• integrity of the elastic membrane.

Let's sum it up

By monitoring the degree of air filling of the working compartment with a pressure gauge, you can find out what pressure is in the expansion tank of the boiler. This will ensure the efficient operation of the device and extend its service life. If adjusted incorrectly, the service life is significantly reduced. The work is easy to do on your own, following the recommendations.