At the present time, a membrane expansion tank has gained great popularity as a compensating device for a coolant. Gravity heating systems with natural circulation are rarely used, and therefore open containers are gradually becoming a thing of the past. Such devices are needed and modern systems water supply, where pumping stations and boilers are installed indirect heating... V this material it will tell you how to choose and connect such a tank to a particular system.
Let's start with the fact that structurally devices intended for heating and water supply (hydraulic accumulators) have some differences and should not be confused with each other. At the same time, the working principle membrane tank the same regardless of its design.
The general arrangement of such tanks is as follows: inside a sealed metal case cylindrical there is a rubber membrane (popularly - "pear"). It is of two types:
Note. The second type of diaphragm must be replaced by unscrewing the pipe flange. The first type cannot be replaced, only together with the body.
The difference between vessels for different systems consists in the fact that membrane expansion tanks for heating systems are filled with a coolant that is in contact with the metal walls from the inside. In tanks for water supply, water never comes into contact with metal, and in some models even the "pear" washing is provided. These modifications are recommended for use in drinking water supply networks.
Another difference is that membranes for expansion tanks for water are manufactured:
Accordingly, the “pear” in the heating tank is adapted to operate at a higher temperature. The very principle of operation of the devices is simple: under the influence of external forces (thermal expansion or pump action), the container is filled with water and stretches the membrane to certain limits. The enlargement of the "pear" on the other hand limits the air under a certain pressure. To create this pressure, the tank device provides for a special spool.
When the external influence stops and the pressure in the pipeline network drops due to the drawdown or cooling of the coolant, the membrane gradually pushes the water back into the system.
To begin with, the membrane expansion tank for water supply cannot be used in heating networks and vice versa. The reason is that each of the systems has its own pressure and temperature, as well as requirements for water quality. Meanwhile, they look very similar, manufacturers even manage to paint the bodies of the tanks in one color (most often - in red). How can you tell?
Each product has a plate with the words - nameplate. It contains all the information that we need. When the nameplate says that the maximum working pressure is 10 bar, and the temperature is 70 ºС, then in front of you is an expansion tank for cold water supply. If the inscription says that the maximum temperature is 120 ºС, and the pressure is 3 bar, then this is a membrane tank for heating, everything is simple.
The second selection criterion is the volume of the tank, it is determined as follows:
Attention! To compensate for the thermal expansion of water in the boiler, it is necessary to take a tank intended for water supply.
Not only the performance of a particular system, but also the service life of the tank depends on how correctly the membrane-type expansion tank is installed and connected. The first thing to do is to place and fix the tank to the wall or floor in the position required by its operating instructions. If there is nothing about this in it, then below in the text we will clarify this issue.
The second point is that a shut-off valve must be installed on the supply pipe. By closing it, you can always remove the membrane pressure tank for repair or replacement. And in order not to flood the floors of the furnace room, between the shut-off valve and the container, it is worthwhile to provide a drain fitting and another tap. Then it will be possible to empty the tank before removal.
In a situation where the documentation for the tank does not prescribe how to correctly orient it in space, we advise you to always put the tank with the inlet pipe down. This will allow for some time to extend his work in the heating system in the event that a crack appears in the diaphragm. Then the air at the top will not rush to penetrate into the coolant. But when the tank is turned upside down, the lighter gas will quickly flow through the crack and enter the system.
It does not matter where to connect the tank supply - to the supply or return, especially if the heat source is a gas or diesel boiler. For solid fuel heaters, the installation of a compensating vessel on the supply is undesirable; it is better to connect it to the return. Well, at the end, adjustment is required, for which the device of the expansion membrane tank provides a special spool on top.
Fully assembled system must be filled with water and vented. Then measure the pressure around the boiler and compare it with the pressure in the air chamber of the tank. In the latter, it should be 0.2 bar less than in the network. If this is not the case, it must be ensured by deflating or pumping air into the membrane water tank through the spool.
Unlike expansion tanks for heating, hydraulic accumulators can be oriented in space as you like, this does not matter much. It will also be useful to install fittings on the inlet to the tank to isolate it from the network and empty it.
But the setting for cold and hot water supply is different. The fact is that the pressure in the pipelines is created by a pump, which has an upper and lower shutdown threshold. You need to be guided by them. It is necessary to set the pressure in the membrane tank operating in the cold water supply circuit by 0.2 bar less than the lower threshold for turning off the pump. This will avoid water hammering in the system.
As for the DHW, here the air pressure in the tank should be 0.2 bar more than the upper shutdown threshold pumping station... This is necessary so that water does not stagnate in the container. More useful information you can find out by watching the video:
It would seem that such a simple unit as a water tank, but requires so much meticulousness in the little things. In fact, a serious approach is needed when installing any element of the house network, otherwise the same minor troubles will befall you very soon.
The volume of the coolant changes depending on the shift temperature regimes, which can lead to dangerous consequences. For safe and long-term operation of the coolant, it is necessary to maintain its stable characteristics. A diaphragm expansion vessel can be used for this.
In heating systems, fluids that are in the process of weak compression act as heat carriers. For safe work heating system, it is necessary to use a stabilizing device - a membrane expansion tank, which is able to receive a certain amount of liquid in the process of increasing pressure and volume, and then return it to the circulation circuit when these indicators decrease.
Diaphragm expansion vessels have a number of advantages over other devices for the same purpose, namely:
However, these devices also have disadvantages, namely:
To avoid uncontrolled loss of heat, experts advise to insulate the device.
The design of sealed expansion tanks is similar to the design of hydraulic accumulators, however, the purpose of these devices is different. The expansion vessel compensates for the expansion of the water due to heating in the heating system. The hydraulic accumulator accumulates the volume of water under pressure in a water supply system with a pressure pump in order to reduce the frequency of activation of this pump and smooth out water hammer. In addition, more often inside the accumulator there is a pear made of food-grade rubber. It is she who is pumped with water, as a result, the water does not come into contact with the tank body. The expansion tank for heating systems is made with a membrane made of technical rubber. It divides the body into two compartments, and the coolant has contact with the body.
The diaphragm tank is a hermetically sealed metal container divided into two compartments (chambers) by an elastic membrane. One such chamber is a pneumatic chamber that contains gas or air under pressure. In the second chamber - a hydrochamber, the coolant is supplied.
The device operates as follows:
With a decrease in the pressure of the coolant in the system, the opposite actions take place. The gas (air) compressed in the pneumatic chamber expands and displaces the liquid from the hydraulic chamber into the system until the pressure difference is restored. The design makes it possible to exclude the possibility of contact between the coolant and air, reducing the likelihood of rusting not only in the tank, but also in other parts of the heating system - the pipeline, the boiler. Sealed expansion tanks are equipped with safety valves to limit the maximum pressure in the heating system to an acceptable level. This also characterizes the tank as a protection device for the heating system.
To compensate for the volume of the coolant in the system during temperature changes, expansion tanks of two types are used: open and closed (sealed).
Open expansion tanks are widespread, but have the following disadvantages:
Sealed expansion tanks do not have these disadvantages. For heating systems, tanks are produced that differ in the use of a membrane. Membranes are divided into balloon and diaphragm types. A balloon membrane is a container installed inside the tank, made of high quality rubber that can withstand significant temperature fluctuations. The flange mounting of such a membrane will allow it to be replaced quickly and easily.
Balloon diaphragms have such advantages as:
The diaphragm membrane is a non-removable baffle, which is most often made of elastic polymer or thin metal. This diaphragm has a low intrinsic capacity and the ability to compensate for small pressure drops in the system. If such a tank fails, it will need to be completely replaced. One of the perks of this device is its low price. In addition, the tank with a diaphragm membrane is simple in design and reliable in operation.
Choosing the right expansion tank means ensuring the safe operation of the heating system, therefore when choosing an expansion tank, you should pay attention to the following main characteristics:
Manufacturers impose certain restrictions on the use of membrane expansion tanks, which depend on the design and materials used in the manufacture of the device. Manufacturers have clear requirements for the properties and composition of the liquid in the heating system. The content, for example, of ethylene glycol in the antifreeze solution is limited. Using a diaphragm expansion vessel when exceeding allowable norms pressure is prohibited. It is mandatory to install a safety group that controls and limits the pressure in the tank. In heating systems of apartments autonomous heating and private houses, equipment is used, the working pressure of which is at least 3 bar.
Volume is main characteristic, by which the expansion tank is selected. Many sources advise choosing the volume of the expansion tank within 10% of the total volume of the coolant in the heating system. This method for determining the capacity of the device is based on the fact that the coefficients of thermal expansion of the coolant, even with a glycol content of up to 90% and heating +100 degrees, do not exceed 0.08. This calculation method does not take into account the pressure in the system, therefore, it can give inaccuracies. There is a more accurate method for calculating the volume of a diaphragm expansion tank. Here the ratio is used:
V = C * Bt / (1 - (Pmin / Pmax)), where
The volume of the coolant in the heating system is determined, taking into account all its nodes. This parameter is obtained from the design documentation for heating. If this is not possible, you can use an approximate calculation, which is based on the fact that the volume of the coolant in heating systems is related to the heating power - for every kW there is 15 liters of liquid. The coefficient of thermal expansion of a liquid is determined using its composition - most often, in heating systems of apartments and houses, it is possible to add glycols to the water to improve its characteristics. This coefficient may also depend on the temperature of the coolant. You can find the required values in the tables for the volume of water in the pipe.
The maximum pressure in the heating system is determined using the minimum of the values that are allowed for different nodes. The transition valve is tuned to it. The initial pressure in the heating system with cooled heat carrier corresponds to the setting (minimum) pressure. For many devices, it can be precisely controlled by common means (bleeding air from the tank or pumping it up with a pump). The pressure in the tank is monitored during the installation of a pressure gauge on it. The calculated data will give an increase in the volume of the coolant in the system during its heating. To select a tank, the fill factor is rounded up. The coefficient depends on the maximum and initial pressure and can be found using tables provided by manufacturers or in special literature.
It is not difficult to install a diaphragm expansion tank, but it is better to entrust it to a specialist. First of all, the instructions for the device must be used. When installing this device in a heating system, it is important to carefully check the tightness of the connections. The expansion vessel must not be opened or disassembled. It is simply connected to the pipeline closest to the boiler. To prevent pressure build-up, safety devices are installed.
When installing the tank, the following rules should be taken into account:
Heating is a key life support system for a private house and its stable operation is very important. One of the parameters that need to be monitored is pressure. If it is too low, the boiler will not work; if it is too low, the equipment will wear out too quickly. An expansion tank for heating is required to stabilize the pressure in the system. The device is simple, but without it the heating will not work for a long time.
When the heating system is operating, the coolant often changes its temperature - it heats up, then cools down. Understandably, the volume of the liquid changes. It increases and decreases. Excess coolant is just displaced into the expansion tank. So the purpose of this device is to compensate for changes in the volume of the coolant.
There are two hot water heating systems - open and closed. V closed system the circulation of the coolant is provided by a circulation pump. It does not create additional pressure, it simply pushes water at a given speed through the pipes. In such a heating system, there is an expansion tank for closed-type heating. It is called closed because it is a sealed container, which is divided into two parts by an elastic membrane. In one part there is air, in the other the excess coolant is displaced. Due to the presence of a membrane, the tank is also called a membrane one.
An open heating system does not provide for a circulation pump. In this case, an expansion tank for heating is just any container - even a bucket - to which the heating pipes are connected. It does not even require a cover, although it may be.
In the very simple version this is a metal-welded container that is installed in the attic. This option has a significant drawback. Since the tank is leaking, the coolant evaporates and it is necessary to monitor its amount - to top up all the time. You can do this manually - from a bucket. This is not very convenient - there is a risk of forgetting to replenish water supplies. This threatens the system with airing, which can lead to its breakdown.
Automated control of the water level is more convenient. True, then in the attic, in addition to the heating pipes, you will also have to pull the water supply and also take the overflow hose (pipe) somewhere in case the tank is overfilled. But there is no need to regularly check the amount of coolant.
There is a very simple method for determining the volume of the expansion tank for heating: 10% of the volume of the coolant in the system is calculated. You had to calculate it when developing the project. If these data are not available, you can determine the volume empirically - drain the coolant, and then fill in a new one, while measuring it (put it through the meter). The second way is to calculate. Determine in the system, add the volume of radiators. This will be the volume of the heating system. Here we find 10% of this figure.
The second way to determine the volume of the expansion tank for heating is to calculate it using the formula. Here, too, the volume of the system will be required (indicated by the letter C), but other data will also be needed:
Having all these values, we calculate the exact volume of the expansion tank for the heating system using the formula:
The calculations are not very complicated, but is it worth messing around with them? If the system open type the answer is unequivocal - no. The cost of the container does not depend on the volume very much, plus everything you can do it yourself.
Expansion tanks for closed-type heating are worth counting. Their price depends on the volume. But, in this case, it is still better to take with a margin, since insufficient volume leads to rapid wear of the system or even to its failure.
If the boiler has an expansion tank, but its capacity is not enough for your system, put a second one. In total, they should give the required volume (the installation is no different).
When heated, the coolant expands, its surplus ends up in the expansion tank for heating. If all the excess does not fit, it is vented through the emergency pressure relief valve. That is, the coolant goes down the drain.
Then, when the temperature drops, the volume of the coolant decreases. But since there is already less of it in the system than it was, the pressure in the system drops. If the lack of volume is insignificant, such a decrease may not be critical, but if it is too small, the boiler may not work. This equipment has a lower pressure limit at which it will operate. When the lower limit is reached, the equipment is blocked. If you are at home at this time, you can remedy the situation by adding a coolant. If you are not there, the system may unfreeze. By the way, working at the limit does not lead to anything good either - the equipment quickly breaks down. Therefore, it is better to play it safe a little and take a slightly larger volume.
In some boilers (usually gas ones), the passport indicates what pressure must be set on the expander. If there is no such record, for normal operation of the system, the pressure in the tank should be 0.2-0.3 atm lower than the operating pressure.
The heating system of a low-rise private house usually operates at 1.5-1.8 atm. Accordingly, the tank should be 1.2-1.6 atm. The pressure is measured with a conventional manometer, which is connected to the nipple, which is located at the top of the tank. The nipple is hidden under a plastic cover, you unscrew it, you get access to the spool. Excess pressure can also be relieved through it. The principle of operation is the same as that of an automobile spool - bend the plate with something thin, releasing the air to the required values.
It is also possible to increase the pressure in the expansion vessel. This will require a car pump with a pressure gauge. Connect it to the nipple, pump it up to the required readings.
All the above procedures are carried out with the tank disconnected from the system. If it is already installed, you do not need to remove it. The pressure in the expansion vessel of the heating system can be checked on site. Just be careful! It is necessary to check and adjust the pressure in the expansion tank for heating when the system is not working and the coolant is drained from the boiler. For the accuracy of measurements and setting the tank, it is important that the pressure on the boiler is zero. Therefore, we drain the water thoroughly. Then we connect the pump with a pressure gauge and adjust the parameters.
An expansion tank in a closed system is placed after the boiler before the pump, that is, so that it creates a flow in the opposite direction. This makes the system more reliable. So the exact place of installation depends on where you have the circulation pump.
It is connected to the system through a tee. You cut a tee into the pipe, direct the perpendicular outlet upwards, the tank is screwed onto it. If the wall does not allow the container to be placed, you will have to make a knee, but the tank is turned up. Now we can assume that the expansion vessel is installed.
But for the convenience of checking, it is advisable to put another tee after the tank, on the free outlet of which a shut-off valve is installed. This makes it possible to check the membrane tank without draining the entire system - it cuts off the tank. Turn off the tap, bleed water from the boiler. Check the pressure on the disconnected branch (in the boiler). It should be zero. After that, you can carry out all the rest of the configuration work.
In a heating system, a very important element is the expansion tank for heating. Such a device serves in order to receive surplus coolant at the moment when it expands, thus preventing bursting of the pipeline and taps.
The principle of operation of the expansion tank for heating is as follows: when the temperature of the coolant rises by 10 degrees, then its volume increases by about 0.3%. Since the liquid is not burnt, excessive pressure appears, which must be compensated. It is for this that the expansion tank is installed.
V different systems heating, different types of expansion tanks are used. Previously, in systems without circulation pumps, an open expansion tank was used for heating. But such tanks had many drawbacks, so now they are very rarely used. Due to the fact that air enters such an expansion tank for heating, corrosion appears, and the liquid also evaporates faster and must be constantly replenished. Such a tank must be placed at the highest point of the heating system, and this is not always easy and simple to implement.
Open expansion tank for heating
In such heating systems, where the heat carrier circulates with the help of a pump, a closed expansion tank is placed for heating, the calculation here is made on the fact that it is a sealed container that has an elastic membrane inside. A membrane (balloon or diaphragm) divides the tank into two parts. Air or inert gas under pressure is pumped into one part, and the other part is intended for excess coolant. The membrane inside the tank is elastic, therefore, when the coolant enters there, the volume of the air chamber becomes smaller, the pressure in it increases, thus compensating high pressure in the heating system. During cooling, the opposite process takes place.
The device of closed expansion tanks
A closed expansion tank for heating a flat tank can be flanged (have a replaceable membrane) and with a non-replaceable membrane. The second type is in high demand due to its relatively low cost. But flanged expansion tanks are in many ways better - the pressure here can be higher, and if the membrane ruptures, then it can be replaced.
The flanged expansion tank of the heating system can be either vertical or horizontal.
Here, the liquid, when it enters the tank, has no contact with metal surface, since it is inside the membrane. If the diaphragm is damaged, it can be replaced through the flange.
Vertical and horizontal flanged tanks
Tanks in which a replaceable membrane is not provided, it is fixed rigidly along the entire perimeter. The diaphragm is pressed against the inner surface from the very beginning, since the volume of the expansion tank for heating is completely filled with gas. After that, the pressure in the expansion tank of the heating increases, and the liquid goes inside. When the system starts up, the pressure can rise sharply, so it is at this point that the membrane can be damaged.
Choosing an expansion tank for heating is a responsible business. In this case, it is imperative to pay attention not only to its type and size, but also to the membrane - such indicators are important: resistance to the diffusion process, operating temperature range, durability, compliance with sanitary requirements.
Today on the market there is a wide range of expansion tanks for the heating system.
In addition, it is necessary to determine the ratio of the limits of the pressure range, which is the maximum permissible. It is imperative to clarify before buying a tank whether it complies with existing quality and safety standards.
First of all, let us determine the dependence of the required volume and the parameters that affect it. When calculating, it must be borne in mind that the larger the capacity of the heating system and the higher the maximum temperature of the heat carrier in it, the larger the tank should be. The higher the permissible pressure in the heating expansion tank, the lower it can be. Of course, the calculation method is quite complicated, so it is better to consult with a specialist. After all, a mistake in choosing an expansion tank can cause frequent actuation of the safety valve or other troubles.
The volume is calculated using a special formula. Here, the main value is the total volume of the coolant that is present in the heating system. This value is calculated taking into account the power of the boiler, the number and types heating devices... Approximate values: radiator - 10.5 l / kW, underfloor heating system - 17 l / kW, convector - 7 l / kW.
To make a more accurate calculation of a device such as a vacuum expander for heating, the formula is applied: Tank volume = (Heating water volume * Heat carrier expansion coefficient) / Expansion tank efficiency. The expansion coefficient for water is 4% when it is heated to 95 degrees. Another formula is applied to determine the efficiency of the tank: Tank efficiency = (Highest system pressure - Initial pressure in the air chamber) / (Highest system pressure + 1).
Expansion vessel useful volume coefficients
Thus, the vacuum expansion tank for heating is selected taking into account the characteristics of strength and temperature, which should not be higher than the permissible values at the connection point. The volume of the tank can either be equal to or be greater than the result that was obtained as a result of the calculations.
Installation of the expansion tank of the heating system is done in accordance with the project and instructions. The best option it will be for you to be carried out by a specialist. If this is not possible, then at least consult with him. The installation of the expansion tank for heating, if it is of an open type, is carried out at the highest point of the heating system. A closed tank can be placed almost anywhere, but not directly after the pump.
One of the options for installing an expansion tank in the heating system
It is necessary to pay special attention to such an issue as fastening the expansion tank of the heating, since the mass of the tank, which is filled with water, increases significantly. Also important point- this is the possibility and convenience of servicing the tank, free access to it.
The role of such a device as an expansion tank of the heating system cannot be underestimated, the instruction of this device provides a list of rules for its maintenance. These include:
Next, how to check the heating expansion tank - its initial pressure of the gas space. To do this, disconnect the tank from the heating system, drain water from it, connect a pressure gauge to the nipple of the gas cavity. If the pressure is lower than that which was set at the same time when the expansion tank for heating was adjusted, the tank must be pumped through the same nipple with a compressor.
Pressure gauge readings at correct work expansion tank
Checking the integrity of the membrane is also an important point. If suddenly, while checking the pressure of the gas space after you have drained the water, air flows through the drain valve, and the pressure in the gas space has decreased to atmospheric, then the membrane is broken.
To replace the membrane, you need to go through several stages. First of all, the tank is disconnected from the heating system, then it needs to be drained. Further, the pressure of the gas cavity is released through the nipple. The diaphragm flange is dismantled. It is located in the area of the pipe connection. The membrane that goes into the expansion tank device for heating is removed from the hole at the bottom of the housing.
Then you need to check the inside of the case so that there is no dirt and corrosion, if any, you need to remove them and rinse with water, and then dry. To remove corrosion, do not use products that include oils! The diaphragm holder is inserted into the hole at the top of the diaphragm. The bolt is screwed into the diaphragm holder, it is inserted into the body, and the holder is retracted into the hole in the bottom of the body. Then the holder is fixed with a nut. After that, the diaphragm flange is placed on the body.
Due to temperature fluctuations, the volume of the heating system coolant may change, which can lead to accidents. Therefore, everything must be done to make it work stably and this does not happen.
For this, special devices are used, for example, a diaphragm expansion tank. It is one of the key components of the heating circuit.
When the coolant heats up, the pressure in the heating system circuit and boilers increases due to an increase in the volume of liquid. Since it is an incompressible medium, and the system itself is sealed, this can lead to breakage of pipes or boilers.
Some people believe that to solve the problem, it is enough to install a valve to squeeze out the excess volume of heated media, but this is not the case. When cooled, the liquid will be compressed, and air will enter the circuit in its place, which will become an obstacle to circulation. Therefore, the air will need to be constantly drained from the radiators, and it will be very expensive to add a new coolant and heat the water.
For this reason, it is recommended to install a membrane expansion tank for heating. It is a reservoir connected by a pipe to the system. Excessive pressure in it will be compensated for by volume, which will provide the circuit with full-fledged operation. The expander takes in a certain amount of liquid when the volume and pressure increase, and then, when these indicators decrease, returns it back. Such devices differ from similar devices of another type. a number of advantages:
But it has an expansion tank and disadvantages. Sometimes you can run into problems when installing it, because it is quite large. Heat loss increases due to the fact that the coolant gives off heat to the expansomat.
In addition, there is an increased risk of rust formation in such devices. To avoid uncontrolled heat loss, it is recommended to insulate the device.
Choosing an expansion tank for heating and water supply systems
How and where is the expansion tank installed for heating
In rooms, heating networks can have open and closed circuits. The first type is used in centralized networks, due to which it is possible to directly take water for the needs of hot water... The devices are placed in the upper part of the circuit. Expansion tanks will not only allow you to control the process of pressure drops, but will also perform the function of separating air from the system. If it belongs to the closed type, then a design with a membrane inside is used.
The expansion tank of the membrane type has a relatively simple device. It includes a water reservoir and a rubber membrane that can be balloon or diaphragm.
If the membrane belongs to the first type, then the coolant is located inside the rubber cylinder, and outside there is nitrogen or air. If necessary, such a part can be replaced, which will save on repairs and not change the entire device.
The diaphragm diaphragm for the expansion tank is a non-removable partition based on a thin metal or elastic polymer.
It has a small capacity and compensates for small pressure drops. If it breaks down, it is impossible to replace it, so you will have to change the tank completely. But compared to a balloon membrane, it is cheaper.
Expansion tank. Operating principle, selection, pumping pressure
For each system, the gas pressure is adjusted according to the instructions for the device. The type of membrane does not affect the efficiency of the device. But if it belongs to the balloon type, more heat-transfer fluid can be placed in the tank. The principle of operation of the diaphragm expansion tank of the heating system at constructions different kind is not different:
Constant pressure is automatically regulated. For the system to work stably, you need to choose the right tank and make calculations. The required pressure will not be able to form if the tank turns out to be larger than necessary, and if it is smaller, it may not hold the excess liquid. This can cause an accident.
In order for a product to work fully, it is necessary not only to correctly select it in terms of volume, but also to take into account its other characteristics. You should pay special attention to the following nuances:
Now on the market you can see a large number of models of Russian and foreign production. They differ in cost, while the suspiciously low price should alert you. It may be due to the fact that low-quality materials of Chinese origin were used in the production. Domestic models are much better in quality, they are cheaper than foreign counterparts from well-known brands, but they are not inferior to them in terms of characteristics.
As already mentioned, the main characteristic that you need to focus on when buying a tank is its volume. Some experts recommend choosing products whose size is within 10% of the total volume of the coolant in the heating system. The fact is that the coefficients of thermal expansion, even at high heating, cannot be higher than 0.08. Therefore, calculations should be carried out as accurately as possible, taking into account indicators such as:
When selecting the volume, you need to take into account all the nodes of the heating system. You can find out by examining project documentation... If it is absent, then the calculation is allowed to be performed approximately, being guided by the fact that 15 liters of water will fall on 1 kW. The thermal expansion coefficient of the coolant is determined using the composition of the liquid. In apartment buildings it often contains glycols to enhance its performance.
Also, the coefficient can be calculated from the temperature of the coolant. The ultimate pressure of the system is determined using the minimum value allowed for the components. The transition valve is adjusted to it. The initial pressure in the system, provided the coolant is cooled, corresponds to the minimum pressure. On some devices, it is regulated by inflating or bleeding air. The pressure in the tank is controlled by installing a pressure gauge.
The use of a membrane tank for heating has a number of restrictions depending on the manufacturer, design and material of manufacture. In some cases, the requirements for the composition of the coolant are very strict. In particular, this concerns the limitation of the amount of antifreeze and ethylene glycol in its composition.
In addition, expansion vessels cannot be used when the pressure limits are exceeded. Also, it is imperative that a security group be established that limits and controls it.
It is not so difficult to install a membrane tank with your own hands; it is not necessary to involve a specialist for the work. Installation requirements are as follows:
If the container has a volume of 30 liters or more, it is forbidden to attach it to supporting structures... Most often it is equipped with special legs and is placed on the floor. When installing, it is recommended to observe such tips:
If the system is closed, then every time it is turned on, a high pressure is applied to the diaphragm. Therefore, you should check its condition at least once every 2 years and, if necessary, replace it. In some cases, everything changes completely.
During installation, gross mistakes must not be made, otherwise the equipment will not function normally. The most common miscalculation is the incorrect indication of the maximum pressure in the gas compartment, which is about 90% of the critical one. If this is allowed, the membrane will not expand towards the compartment. As a result, the pipe will burst, because of which the heating batteries will not be able to work. To correct the error, you need to install a certified pressure gauge. You also need to make sure that there is no tank in the boiler itself. If, after calculations, it is established that its volume is small, then additional capacity will be required.
The expansion tank in the heating system is very important. It depends on him how correctly it will work. It is not difficult to install it, but you need to pay special attention to this process, since even a small oversight can cause an emergency in the future.
