Expansion tank for heating. Features of choice. Expansion tank for open type heating Types of expansion tanks for closed type heating

How to choose an expansion tank for heating

An expansion tank is a special container that makes it possible to compensate for the thermal expansion of the liquid circulating in the heating system. When water is heated, its volume increases, the dynamics of the increase in volume is about 0.3% for every 10°C.

The liquid is characterized by a low compressibility coefficient, so the excess volume will have nowhere to go in a completely sealed system without a special reservoir, which will lead to an accident - due to the increased pressure, connections may leak or pipes may burst. It is also impossible to replace the expansion tank with a valve for discharging “extra” heated coolant, since during cooling the liquid in the pipeline will compress, forming a vacuum - this will lead to depressurization of the system and air entering there - as a result, the heating will not function.

Types of expansion tanks

When selecting an expansion tank, you should first of all focus on the type of heating system - it can be open or closed.

1. Open tanks

This type of device is designed for operation as part of a heating system in which the coolant moves through the pipes by gravity, as a result of natural convection. The design of the expansion tank in this case is extremely simple - it is a conventional cylindrical or rectangular container. The reservoir must be installed at the highest point of the system piping. It not only compensates for the thermal expansion of the coolant, but also ensures air removal from the system.

Open tank

Since liquid evaporates from an open tank, it is necessary to regularly visually check the level and add water. To do this, you need to install an appropriate branch of the water supply with a tap or carry buckets of water to the attic of the house where the tank is usually installed.

To reduce heat loss, it is recommended to provide thermal insulation for such an expansion tank. The container is made of sheet metal, the upper part is equipped with a lid so that the water evaporates and cools less. To control the maximum liquid level, the tank is equipped with an overflow pipe, which is discharged into the sewer or outside.

The disadvantage of the design is:

• the need for regular maintenance;
• increased heat losses;
• rapid corrosion of the internal walls of the tank;
• the need to lay additional pipes.

Advantages:

• the ability to create a completely energy-independent heating system;
• simple design - the tank can be made and installed independently.

Today, open-type expansion tanks are used less and less due to the low efficiency of the gravity heating system.

2. Closed tanks

Such a device can be matched to any type of heating system - with natural and forced circulation. The use of closed containers made it possible to eliminate contact of the coolant with air - this reduced the corrosion hazard for heating system elements made of steel and extended their service life.

Closed expansion tanks with various membranes

The advantages of sealed expansion tanks also include:

• no evaporation of the coolant (there is no need to monitor the water level, add it to the system, or install an overflow outlet);
• the heating system can operate at higher pressure;
• Since the tank is mainly installed in the boiler room, it does not need to be protected from freezing, it functions reliably throughout the heating season.

A sealed closed tank must be equipped with a manual or automatic valve for air removal. If the valve is manual, it is necessary to visually monitor the filling of the system with coolant. If there is an automatic valve, control is carried out by a pressure gauge, which measures the pressure in the system.

3. Membrane type tanks

A modern, improved version of a closed, sealed tank operates automatically. The key part of the device is the internal membrane, made of an elastic polymer waterproof material that is resistant to high temperatures.

The membrane allows you to divide the cavity of the tank into water and air chambers, so that the coolant does not come into contact with the metal walls of the container and with the air. This reduces the risk of oxygen penetrating the liquid and protects the system from corrosion; the tank itself is also protected from the destructive effects of moisture.

Diaphragm expansion tank

When the coolant expands, the membrane is deformed and causes the air in the tank chamber to compress. When the liquid cools, the air pushes it back into the pipeline. This operating principle made it possible to reduce the size of the tank required for the heating system by approximately 4 times. In addition, installing a membrane tank allows you to maintain the pressure in the system at a stable level, which has a beneficial effect on the durability of all equipment used to supply heat to the house.

The expansion membrane tank also serves as a kind of fuse - if the pressure in it for some reason reaches critical values, the circulation pump will automatically turn off. The system can be restarted only after the pressure has normalized.

Operating principle of a closed expansion tank

When considering how to choose a membrane-type expansion tank, you should pay attention to the durability of the device. Over time, the membrane loses elasticity and cracks. It is recommended to purchase a model with a replaceable membrane - this makes it possible, if necessary, to quickly repair the tank instead of completely replacing it.

The list of advantages of the device includes:

• compact dimensions;
• no coolant evaporation;
• minimal heat loss;
• protection of the heating system from corrosion;
• the ability to operate the system under high pressure.

Expansion tank in section

Note! When you go to choose a membrane expansion tank, pay attention to the markings so as not to confuse it with a hydraulic accumulator for the water supply system. They are similar in shape and can be painted in the same colors. The nameplate located on the tank body indicates the operating temperature and pressure: for the expansion tank up to 120°C and 3 bar, for the hydraulic accumulator, respectively, no more than 70°C and 10 bar.

Tank volume calculation

The question of how to choose an expansion tank for a heating system is directly related to determining the required volume of the tank. This requires a number of calculations.

When designing a heating system, it is taken into account that the volume of the expansion tank should be about 15% of the volume of coolant in the system.

• in a boiler unit - this parameter is indicated in the product passport;
• in all heating radiators - calculated for each radiator and summed up. The values ​​specified in the technical specifications of the relevant type of radiator should be used;
• in a pipeline - calculated based on the cross-section and length of the pipes.

The calculation of radiators depends on the type - if it is a panel model, its internal volume is indicated in the passport. For sectional models, the volume of one section is given; this value must be multiplied by the number of sections.

To calculate the amount of water in the pipes, use the formula Vtotal = π × D2 × L/4

• L – pipe length (you will need to measure all heating circuits in the house);
• D – internal diameter of the pipeline;
• π – 3.14.

Before making calculations, it is necessary to calculate the total length of the pipes in centimeters and also convert the diameter into centimeters. After calculating the volume using the formula, the result will also be expressed in centimeters. To convert the resulting value into liters, you need to divide it by 1000.

Conclusion

The question of how to choose an expansion tank for heating is important to ask during the design of the heating system and select the appropriate type of tank. But the calculation of the volume and, accordingly, the purchase of the device should be postponed to the final stage. This is due to calculations of tank volume.

If, according to the project, a water heated floor system will be installed in the house, do not forget to determine the length of the contour in each room before pouring the screed. This also applies to hidden radiator heating pipelines.

When buying an expansion tank, it is better to choose a model that is slightly larger in volume relative to the calculated value than a smaller one. A large tank will not fundamentally affect the functionality of the system.

Check out the video below, which will help you decide on the choice of tank.

But if the selected membrane tank is not spacious enough, the heated coolant will be discharged through the emergency valve. In this case, a new membrane tank of a larger volume is installed or another expansion tank is installed in the system.

The heating system is a complex engineering structure. The expansion tank is an important element of the system. Let's take a closer look at why it is used in a heating system, and also figure out how to make the calculation.

Features of a closed system

In open heating circuits that are in contact with the atmosphere, there is a problem with the expansion of the coolant. You can solve it as follows:

1. At the highest point of the house, a tank is installed.
2. If there is excess pressure, excess liquid will flow into a pre-installed container.
3. After the liquid cools, it will flow back into the system under the influence of atmospheric pressure.

The main disadvantage is the need to air the system, as water evaporates. This disadvantage can be avoided with a hermetically sealed heating system.

The expansion tank is used for closed-type heating to compensate for the expansion of the coolant. In this case, there will be no direct contact with the atmosphere.

Why install an expansion tank in a heating system?

In the heating system, pressure increases when the coolant heats up. As a result, destruction of pipelines and the boiler may occur. Even installing a simple valve that can discharge excess coolant into the atmosphere will not help solve the problem. Since when cooling the liquid will compress, and air will flow into the free space. And, consequently, air jams will form, due to which the circulation of the heating system will be disrupted.

The only way to solve this problem is to install an expansion tank. Due to its volume, the tank can ensure high-quality operation of the circuit.

Expansion tanks for closed heating differ in size and shape. They can be either cylindrical or tablet-shaped.

Design and principle of operation of the tank

Compared to open vessels, the most convenient are membrane tanks, which are completely sealed. To stabilize the pressure inside the cold water system, blue hydraulic accumulators are produced. To prevent airing of the circuit in a closed-type heating system, a red expansion tank is installed in the heating circuits. It is also installed to remove excess water when heated.

Membrane tanks are similar in structure, but have some differences:

• Expansion tank for closed type heating. It is separated by a rubber partition in the middle. It is usually cylindrical in shape. But they also produce tanks that are shaped like tablets. Such expansion tanks are used for small volumes of coolant. When water is heated, the coolant expands, so excess liquid easily flows into the tank.
• A rubber bulb is installed in the hydraulic accumulator, which easily follows the contours of the internal chamber.

You should be aware of the prohibition of installing a red membrane sealed tank after the circulation pump.

Materials from which membrane tanks are made:

In the expansion tank, technical rubber is used to make the membrane, and the inner surface is coated with anti-corrosion. In a hydraulic accumulator, the membranes are made of food-grade rubber, and the shape must not allow water to pass through. Thus, contact of the metal case with water is excluded.

If you install a red membrane tank for a cold water system, the water will not meet sanitary standards. And if you install a blue tank, which is not suitable for hot water, then the performance of the system will decrease.

Calculation of expansion tanks

In order to calculate the expansion tank, it is necessary to calculate the total volume of the entire system. It is equal to the sum of the volumes: the heating boiler, pipelines and heating appliances. In order to determine the volume of the radiator and boiler, no calculations need to be made, since the value is indicated on the equipment passport. To calculate the volume of pipelines, you need to find out the internal cross-sectional area of ​​the pipes, and then multiply it by the length. If pipelines with different diameters are installed in the heating system, then each pipe should be calculated separately and the resulting volumes added up.

The expansion tank should provide an increase in fluid volume by approximately 10%. If the coolant volume is 400 liters, then the volume together with the expansion tank should be 440 liters. Therefore, the volume of the tank should be 40 liters. But such a calculation is approximate and may differ greatly from the real one, so it is better to make an accurate calculation. There are many calculators on the Internet that will calculate the expansion tank online. For a more accurate result, it is better to use several calculators.

Installing the tank yourself

To prevent water hammer inside the heating system, you must adhere to the following rules when installing the expansion tank:

1. It is impossible to make a tie-in after installing a circulation pump.
2. To be able to regulate pressure, it is necessary to provide access to the shut-off valves.
3. There must be no static pressure in the circuit piping.

Expansion tanks on the return line in front of the boiler are considered a profitable option. For floor-mounted installations, special stands are sold, and for wall-mounted installations, brackets should be used. There are brackets that are pre-welded to the body, and there are also separate ones that are included in the kit and need to be assembled yourself.

If you need to replace the membranes, you will need to completely disassemble the entire system. To avoid this, you can screw a ball valve onto the expansion tank pipe. This way you can remove the tank without disassembling it.

The general diagram of the device looks like this:

• First of all, the expansion tank is unpacked;
• The threaded fitting is being installed;
• Ball valve device;
• If the bracket is not pre-installed, then it is necessary to assemble it and attach it with a tape clamp;
• Installation of the tank depending on the type;
• Next, you need to drain the coolant and then relieve pressure from the heating system;
• Tie with a composite steel or polymer pipe;
• Carry out pressure testing with working pressure;
• Adjust the pressure in the air chamber if necessary. This can be done using a car pump.

For a more precise position of the expansion tank, brackets with a safety group are made, which facilitate installation.

For high-quality sealing of threaded connections, it is not recommended to use FUM tape. A better option would be Unipack winding.

The expansion tank is an indispensable part of closed-type heating.

To provide the coolant with the opportunity to expand when heated, it is necessary to install an expansion tank in the heating system. This is a very important event. It will protect pipes and radiators from unnecessary loads and significantly increase the service life of the functional elements of the autonomous heating system.

We will talk about how the expansion tank works in open and closed circuits. We'll show you how to install it correctly in both versions of the system. In our article you will find a description of the technology for connecting this backup capacity and useful recommendations.

An expansion tank is needed to compensate for the effect that an increase in the volume of coolant during heating has on the heating system. An additional container connected to the circuit becomes a storage place for the resulting excess water. When the temperature drops, part of the coolant leaves the tank and returns to the pipes.

The process is repeated with each heating and cooling cycle. If there was no such reservoir in the system, then when the water inside the pipes was heated, the pressure would increase and then decrease.

Such differences negatively affect the state of the system. They lead to leaks at the junctions of devices and pipes and can even cause equipment failure.

The expansion tank is selected depending on the characteristics of the heating system. For closed circuits, you need a special closed capsule with a membrane, and for open circuits, an unsealed container of a convenient configuration and the required size is suitable.

You should choose a membrane tank that is designed for contact with hot water. Typically, the body of such devices is painted red. You can make a container for installation in an open circuit yourself, for example, weld it from sheet metal. But it is important not only to choose the right device, but also to install it correctly.

For closed heating systems, containers with a membrane are used as an expansion tank, which allows the coolant to be stored under a certain pressure

Installation of membrane device

A hydraulic accumulator of this type is installed where there is a minimum probability of coolant turbulence, since a pump is used for normal circulation of water flow along the circuit.

Correct container position

When connecting the expansion tank to the device, you must take into account the location of the air chamber of the device.

The rubber membrane periodically stretches and then contracts. Due to this impact, microcracks appear on it over time, which gradually increase. After this, the membrane has to be replaced with a new one.

If the air chamber of such a tank remains at the bottom during installation, the pressure on the membrane will increase due to gravitational influence. Cracks will appear faster and repairs will be needed sooner.

It makes more sense to install the expansion tank in such a way that the compartment filled with air remains on top. This will extend the life of the device.

Features of choosing an installation location

There are a number of requirements that must be taken into account when installing a membrane expansion tank:

1. It cannot be placed close to the wall.
2. The device should be freely accessible for regular maintenance and necessary repairs.
3. The wall-hung tank should not be positioned too high.
4. A shut-off valve should be placed between the tank and the heating pipes, which will allow you to remove the device without completely draining the coolant from the system.
5. When installing on a wall, the pipes connected to the expansion tank must also be attached to the wall in order to remove possible additional load from the tank pipe.

For a membrane device, the most suitable connection point is the return section of the line between the circulation pump and the boiler. Theoretically, it can be installed on the supply pipe, but high water temperatures will negatively affect the integrity of the membrane and its service life.

When using solid fuel equipment, such placement is also dangerous because steam can enter the container due to overheating. This will seriously disrupt the operation of the membrane and may even damage it.

Setting up the device before use

Before installation or immediately after it, it is necessary to correctly configure the expansion tank, otherwise called an expansion tank. This is not difficult to do, but first you need to find out what pressure should be in the heating system. Let's say an acceptable value is 1.5 bar.

Now you need to measure the pressure inside the air part of the membrane tank. It should be less by about 0.2-0.3 bar. Measurements are carried out with a pressure gauge with a suitable gradation through the nipple connection, which is located on the tank body. If necessary, air is pumped into the compartment or excess air is vented.

Before installing the membrane tank in the heating system, check the air pressure in the air compartment and adjust it according to the requirements

The technical documentation usually indicates the operating pressure, which is set by the manufacturer at the factory. But practice shows that this is not always true. During storage and transportation, some air may escape from the compartment. You must take your own measurements.

If the pressure in the tank is not set correctly, this can lead to air leakage through the air removal device. This phenomenon causes a gradual cooling of the coolant in the tank. There is no need to pre-fill the membrane tank with coolant; simply fill the system.

Tank as additional capacity

Modern ones are often already equipped with a built-in expansion tank. However, its characteristics do not always correspond to the requirements of a specific heating system. If the built-in tank is too small, you need to install an additional tank.

It will ensure normalcy in the system. This addition will also be relevant if the heating circuit configuration changes. For example, when a gravity system is converted into a circulation pump and the old pipes are left behind.

This is true for any systems with a significant volume of coolant, for example, in a two- or three-story cottage or where, in addition to radiators, there is a heated floor. If a boiler with a small built-in membrane tank is used, installing another tank is almost inevitable.

An expansion tank will also be appropriate when used. A relief valve, similar to that installed on electric boilers, will not be effective here; an expansomat is an adequate way out of the situation.

Connecting the expansion tank

The location for installing such a tank is chosen where the intake of excess coolant will be as efficient as possible.

When figuring out how to properly install an expansion tank in, you need to pay attention to three important points:

• select the highest point of the contour;
• place the tank directly above the heating boiler so that they can be connected by a vertical pipe;
• provide overflow in case of an accident.

The requirements are explained by the peculiarities of the functioning of gravity heating systems. The hot coolant moves from the boiler through the pipes and reaches the expansion tank, losing a significant part of the thermal energy.

The cooled water naturally flows through the pipes into the heat exchanger for new heating. The location of the tank at the highest point allows air bubbles trapped in the system to be removed from the coolant.

This is especially convenient if you need a large capacity, because a significant amount of coolant may be required for normal operation of a gravity system. A small expansion tank can even be placed in the kitchen under the ceiling, if this allows it to be connected correctly to the heating boiler.

If the device had to be placed in the attic, you need to take care of its insulation. This is especially important if the attic is not heated. Although it enters the tank already cooled, you should not neglect the opportunity to save some of the thermal energy. In the future, heating will require less time and fuel, which will significantly reduce heating costs.

To connect the expansion tank and overflow, you need to run two pipes into the boiler room. The overflow is usually connected to the sewer, but sometimes home owners decide to simply take the pipe outside, and an emergency discharge is made outside.

The configuration of the expansion tank can be any; such devices are made of sheet iron, plastic tanks and other materials that tolerate heat well

After the location has been selected and its volume calculated, you need to find and install a suitable container. Small tanks are mounted on the wall using brackets or clamps.

Large containers must be placed on the floor. There is no need to seal this tank hermetically, but you will still need a lid. It is necessary to protect the coolant from debris.

Some of the water from an open system evaporates, the lost volume must be replenished. The coolant is usually added to the open circuit through the expansion tank.

This point must be taken into account when choosing a place to install the device. It is not always convenient to carry water into the attic with a bucket. It is easier to provide in advance for the installation of a supply pipe that leads to the expansion tank.

Conclusions and useful video on the topic

Step-by-step demonstration of installing and connecting a membrane tank to a heating system:

Interesting tips for installing an expansion tank in an open system:

A regular expansion tank, like a membrane accumulator, is not too difficult to install. This does not require special skills or tools. But it is necessary to strictly comply with the requirements related to the characteristics of the heating system for which such installation is being carried out.

Would you like to talk about how you installed the expansion tank with your own hands? Do you have useful information that can help website visitors with self-installation? Please write comments, ask questions and post photos related to the topic of the article in the block below.

In a water heating system, one of the components is an expansion tank. This is a small reservoir that is responsible for stabilizing pressure. Without it, damage to pipes, radiators and other system elements is possible. Let's talk further about what an expansion tank for heating is and how it regulates pressure.

Purpose and types

In a heating system, the temperature of the coolant constantly changes, which leads to changes in its volume. It is known that liquids expand when heated and contract when cooled. The expansion tank for heating is precisely designed to absorb excess liquid during heating (expansion) and return it to the system when cooling. This way it maintains a stable .

Open type

There are two types of expansion tanks: open and closed. Open type containers are usually used in gravity flow systems (). It is called this because it is a non-sealed container. This could be a barrel, a pan, or a specially welded tank. In order for the coolant to evaporate less, a lid is installed, but the container itself is not airtight. The principle of operation of an open expansion tank is simple: it is a container into which excess coolant is forced out when the temperature rises and is supplied back when it cools.

Open type expansion tank - any container, for example, a plastic canister

When calculating open-type tanks, take a significant reserve in volume: you can add coolant and not check its level for some time. The container is not airtight, so there is constant evaporation of liquid and a supply will not hurt. If there is a lack of coolant, air will enter the system, which can stop it. The consequences can be sad - if the boiler’s automatic system works (if it has one), there is a possibility of defrosting. If there is no automation, the boiler may rupture due to overheating. In general, this is the case when the stock is really justified.

If the heating system is filled with water, you can make an automatic replenishment based on a float from the toilet cistern. The principle of operation is exactly the same: when the level drops below a certain point, the water supply opens. When the required level is reached, the supply is shut off.

The advantage of this solution is that there is no need to control the amount of coolant, the possibility of airing is minimal. The downside is that you have to pull the water pipe. Since open systems usually operate on natural circulation, the expansion tank for heating is placed at the highest point of the system. Very often this is an attic, so the route turns out to be long.

And these are not all possible emergency situations. Floats sometimes do not shut off the water supply. If this happens to the toilet, the water simply runs into the drain. In the case of heating, water will flow into the attic, flooding the house... To avoid such a situation, it is necessary to control the overflow. In the simplest case, it is a pipe welded/attached at the required level with a hose connected to it. The hose can be led into the sewer, but then you also need to come up with an overflow alarm (at the same time, the level will drop below critical). You can simply lead the hose a meter away from the house or run it into the drainage system. In this case, “traces” of overflow will be visible and it will be possible to respond in a timely manner without an alarm. So an open expansion tank for heating requires some retrofitting.

Closed type

An expansion tank for closed-type heating is installed in systems with forced movement of coolant. In them, the movement of the coolant is activated by a circulation pump. Such systems operate at elevated (relative to atmospheric) pressure. To maintain this pressure, the container must be sealed.

One of the main functions of an expansion tank for a closed heating system is to maintain stable pressure. To do this, the container is divided into two parts. One contains air or an inert gas (usually argon) pumped in at the factory. This part is sealed, there is a small diameter outlet in which a spool is installed (the operating principle is the same as that of a bicycle or car). The other chamber is empty and has an exit of some cross section. Through this outlet the expansion tank for heating is connected to the pipeline. During expansion, coolant enters this chamber.

The closed-type expansion tank is divided into chambers using an elastic rubber partition - membranes. It comes in two types: in the form of a diaphragm (disk) or a pear. There is not much difference, except that the bulb is easier to change. So bulb-type containers are more popular than diaphragm-type ones.

The operating principle of a membrane expansion tank is more complicated than an open one. A certain pressure is created in the “dry” chamber. It is selected depending on the operating pressure in the system, and the standard factory setting is 1.5 Bar. While the pressure in the system is lower than in the expansion tank, the “water” part of the tank remains empty.

When it gets higher, liquid begins to flow, the membrane stretches, increasing the pressure in the “gas” part of the tank. This process occurs until either the pressure in the system begins to drop (the coolant cools down) or the container is completely filled. The first case is normal operation of the heating system, the second is an emergency.

The second option means that the volume of the expansion tank is not enough. And this situation occurs when the size is incorrectly selected (too small) or when the boiler overheats. To maintain the functionality of the system in such situations, emergency valves are installed.

Determining the volume of the expansion tank and its selection

For normal heating operation, the expansion tank must have sufficient volume. There are two ways to determine it: you can calculate it using a formula, or you can use empirical data.

Empirical path

Let's start with the empirical method. Based on operating experience, it was concluded that if the volume of the expansion tank for heating is about 10% of the total volume of the heating system, this is sufficient. The question is how to determine the volume of the system. There are at least two ways:

• Count when filling (if it is filled with water and there is a meter, or when filling with coolant from canisters, you will know exactly how much liquid was pumped in).
• Calculate by volume of system elements. You will need to find information about how many liters fit in one meter of pipe, in one section of the radiator. With this data you can already find out the volume of the heating system.

Knowing how many liters of coolant are in your heating, it is easy to calculate the required volume of the membrane tank - it should be at least 10% of this figure. In the case of an open type tank, the actual volume can be at least doubled - there is less chance that the tank will be empty. At a minimum, you should add half - you will still underfill it by at least 1/3.

A membrane expansion tank for heating is usually taken without overestimating the calculated figure. The fact is that the larger the capacity, the more expensive the expander costs. And the price increase is significant. However, you should not take a smaller one - the pressure will “jump”, which will lead to early wear of components or even shutdown of the system. It is most likely that the heating will fail in cold weather, because in cold weather the coolant is hotter, which means its volume is larger. And it is at these moments that the volume of the expansion tank may not be enough. If you notice such symptoms and the calculation confirms that your membrane tank is of insufficient size, it is not necessary to change it to a larger one. You can put a second one. It is important that their total capacity is not less than the calculated value.

If there is antifreeze in the system

Heating antifreeze has greater thermal expansion than water. Moreover, different brands have different characteristics. Therefore, for this type of coolant, it is advisable to pre-calculate the volume of the expansion tank.

There are two ways: determine how for water, make an adjustment for greater thermal expansion. It depends on the percentage of ethylene glycol (antifreeze). For every 10% glycol, add 10% volume. That is:

• 10% ethylene glycol - must add 10% of the found volume of the water tank;
• 20% ethylene glycol - add 20%, etc.

This calculation is usually justified, but more accurate figures can be found using the formula (shown in the figure).

Once you have decided on the volume, it's time to buy an expansion tank. But in the store they are in different colors. At a minimum, there are blue (cyan) and red. So, membrane expansion tank for heating is always red. Blue ones are for plumbing, and for cold water. They are much cheaper, but the membrane there is made of rubber not suitable for high temperatures. So it will not last long in the heating system.

Pressure in the membrane tank and checking it

For a closed heating system to work properly, the pressure in the expansion tank must be 0.2-0.5 Bar lower than in the system. The larger the system, the greater the pressure difference. But, as already said, at the factory they are pumped up to 1.5 Bar, so before installing the expander, it is better to check it and adjust it to your heating system.

We check the pressure with a pressure gauge by connecting it to the outlet with the spool. If the pressure is higher than you need, bleed off a little. This is not difficult to do - press the petal in the nipple with something thin. You will hear the hiss of escaping air. When the pressure reaches the desired level, release the petal.

If the membrane tank is inflated too weakly (this also happens), it can be inflated with a regular pump. But it’s more convenient to use a car one, with a pressure gauge - you can immediately control the pressure. After verification, you can install it on the system.

Installation location

An expansion tank for closed-type heating is installed in a straight section in front of the circulation pump. Before, in the sense that the pump drives water from the expansion tank, and not into it. In this case, the expander works more correctly.

To install a membrane tank, install a tee, from which comes a pipe to which the container is connected. The installation height does not matter. But it is better to install shut-off valves in front of and behind the tank. The membrane fails every few years. Even more often you have to check it and pump it up. To avoid having to stop and drain the system for maintenance, a shut-off valve is installed. It is blocked off and the tank can be removed, checked, and repaired.

In open-type systems, the installation location of the expansion tank is selected based on other considerations. It is placed at the highest point of the system. In this case, it also works as an air collector. Air bubbles tend to rise, and if there is an expansion tank at the highest point, they rise to the surface, escaping into the atmosphere. So such a tank is deliberately made leaky so that the air from the heating system can escape naturally.

Over the past few years, closed heating systems have become increasingly popular. Heating equipment is becoming more and more expensive, and you want it to last longer. In closed systems, the possibility of free oxygen getting inside is practically eliminated, which extends the life of the equipment.

Closed heating system - what is it?

As you know, any heating system in a private home has an expansion tank. This is a container that contains some coolant removal. This tank is necessary to compensate for thermal expansion under various operating conditions. By design, expansion tanks are of open and closed type, respectively, and heating systems are called open and closed.

In recent years, a closed heating scheme has become increasingly popular. Firstly, it is automated and works without human intervention for a long time. Secondly, it can use any type of coolant, including antifreeze (it evaporates from open tanks). Thirdly, the pressure is maintained constant, which allows the use of any household appliances in a private home. There are several more advantages that relate to wiring and operation:

• There is no direct contact of the coolant with air, therefore, there is no (or almost no) unbound oxygen, which is a powerful oxidizing agent. This means that the heating elements will not oxidize, which will increase their service life.
• A closed-type expansion tank is placed anywhere, usually close to the boiler (wall-mounted gas boilers come immediately with expansion tanks). An open-type tank should be located in the attic, and this means additional pipes, as well as insulation measures so that heat does not “leak” through the roof.
• The closed type system has automatic air vents, so there is no airing.

In general, a closed heating system is considered more convenient. Its main drawback is its energy dependence. The movement of the coolant is ensured by a circulation pump (forced circulation), and it does not work without electricity. It is possible to organize natural circulation in closed systems, but it is difficult - it requires regulating the flow using the thickness of the pipes. This is a rather complicated calculation, which is why it is often believed that a closed heating system only works with a pump.

To reduce energy dependence and increase heating reliability, install uninterruptible power supplies with batteries and/or small generators that will provide emergency power supply.

Components and their purpose

In general, a closed heating system consists of a certain set of elements:

• Boiler with safety group. There are two options here. The first is that the safety group is built into the boiler (gas wall-mounted boilers, pellet boilers and some solid fuel gas generators). The second is that there is no safety group in the boiler, then it is installed at the outlet in the supply pipeline.
• Pipes, radiators, convectors.
• Circulation pump. Ensures the movement of coolant. It is installed mainly on the return pipeline (the temperature is lower here and there are fewer possibilities of overheating).
• Expansion tank. Compensates for changes in coolant volume, maintaining stable pressure.

Now in more detail about each element.

Boiler - which one to choose

Since the closed heating system of a private house can operate autonomously, it makes sense to install a heating boiler with automation. In this case, having configured the parameters, you do not need to return to this. All modes are supported without human intervention.

The most convenient gas boilers in this regard. They have the ability to connect a room thermostat. The temperature set on it is maintained with an accuracy of one degree. It dropped by a degree, the boiler turned on, heating the house. As soon as the thermostat is activated (the temperature is reached), the operation stops. Comfortable, convenient, economical.

Some models have the ability to connect weather-dependent automation - these are external sensors. Based on their readings, the boiler adjusts the power of the burners. Gas boilers in closed heating systems are good equipment that can provide comfort. The only pity is that gas is not available everywhere.

Electric boilers can provide a no less degree of automation. In addition to traditional units, induction and electrode units have recently appeared on heating elements. They are distinguished by their compact size and low inertia. Many believe that they are more economical than boilers using heating elements. But even this type of heating unit cannot be used everywhere, since power outages in winter are a common occurrence in many regions of our country. And provide the boiler with electricity. 8-12 kW from the generator is a very difficult matter.

Solid or liquid fuel boilers are more versatile and independent in this regard. An important point: to install a liquid fuel boiler, a separate room is required - this is a requirement of the fire service. Solid fuel boilers can be installed in the house, but this is inconvenient, since a lot of debris falls from the fuel during combustion.

Modern solid fuel boilers, although they remain periodic equipment (they warm up during combustion and cool down when the fuel burns out), but they also have automation that allows you to maintain a given temperature in the system, regulating the intensity of combustion. Although the degree of automation is not as high as that of gas or electric boilers, it is there.

Pellet boilers are not very common in our country. In fact, this is also solid fuel, but boilers of this type operate in continuous mode. Pellets are automatically fed into the firebox (until the stock in the burner is finished). If the fuel quality is good, ash cleaning is required once every few weeks, and all operating parameters are controlled automatically. The only thing holding back the spread of this equipment is its high price: the manufacturers are mainly European, and their prices are corresponding.

A little about calculating boiler power for closed-type heating systems. It is determined according to the general principle: per 10 sq. meters of area with normal insulation take 1 kW of boiler power. It’s just not recommended to take it “back to back”. First, there are unusually cold periods during which you may not have enough rated power. Secondly, working at the power limit leads to rapid wear of the equipment. Therefore, it is advisable to take the boiler power for the system with a margin of 30-50%.

Security group

A safety group is placed on the supply pipeline at the outlet of the boiler. She must control its operation and system parameters. Consists of a pressure gauge, automatic air vent and safety valve.

The pressure gauge makes it possible to control the pressure in the system. According to recommendations, it should be in the range of 1.5-3 Bar (in one-story houses it is 1.5-2 Bar, in two-story houses it is up to 3 Bar). If you deviate from these parameters, appropriate measures must be taken. If the pressure drops below normal, you need to check if there are any leaks, and then add some coolant to the system. At increased pressure, everything is somewhat more complicated: it is necessary to check in what mode the boiler is operating, whether it has overheated the coolant. The operation of the circulation pump, the correct operation of the pressure gauge and the safety valve are also checked. It is he who must discharge excess coolant when the threshold pressure value is exceeded. A pipe/hose is connected to the free branch pipe of the safety valve, which is discharged into the sewer or drainage system. Here it is better to do it in such a way that it is possible to control whether the valve works - if water is discharged frequently, you need to look for the reasons and eliminate them.

The third element of the group is an automatic air vent. Air trapped in the system is removed through it. A very convenient device that allows you to get rid of the problem of air locks in the system.

Security groups are sold assembled (pictured above), or you can buy all the devices separately and connect them using the same pipes that were used to wire the system.

Expansion tank for closed heating system

The expansion tank is designed to compensate for changes in coolant volume depending on temperature. In closed heating systems, this is a sealed container divided into two parts by an elastic membrane. At the top there is air or inert gas (in expensive models). While the coolant temperature is low, the tank remains empty, the membrane is straightened (picture on the right).

When heated, the coolant increases in volume, its excess rises into the tank, pushing back the membrane and compressing the gas pumped into the upper part (in the picture on the left). This is displayed on the pressure gauge as an increase in pressure and can serve as a signal to reduce the combustion intensity. Some models have a safety valve that releases excess air/gas when a threshold pressure is reached.

As the coolant cools, the pressure in the upper part of the tank squeezes the coolant out of the container into the system, and the pressure gauge readings return to normal. That's the whole principle of operation of a membrane-type expansion tank. By the way, there are two types of membranes - disc-shaped and pear-shaped. The shape of the membrane does not affect the operating principle in any way.

Volume calculation

According to generally accepted standards, the volume of the expansion tank should be 10% of the total coolant volume. This means that you must calculate how much water will fit in the pipes and radiators of your system (it is in the technical data for radiators, and the volume of the pipes can be calculated). 1/10 of this figure will be the volume of the required expansion tank. But this figure is only valid if the coolant is water. If non-freezing liquid is used, the tank size is increased by 50% of the calculated volume.

Here is an example of calculating the volume of a membrane tank for a closed heating system:

• the volume of the heating system is 28 liters;
• expansion tank size for a system filled with water 2.8 liters;
• the size of the membrane tank for a system with non-freezing liquid is 2.8 + 0.5 * 2.8 = 4.2 liters.

When purchasing, select the nearest larger volume. Don't take less - it's better to have a small supply.

What to look for when purchasing

There are red and blue cans in stores. Red tanks are suitable for heating. The blue ones are structurally the same, only they are designed for cold water and cannot tolerate high temperatures.

What else should you pay attention to? There are two types of tanks - with a replaceable membrane (they are also called flanged) and with a non-replaceable one. The second option is cheaper, and significantly, but if the membrane is damaged, you will have to buy the whole thing. For flanged models, only the membrane is purchased.

Place for installing a membrane type expansion tank

Usually they place an expansion tank on the return pipeline in front of the circulation pump (if you look in the direction of flow of the coolant). A tee is installed in the pipeline, a small section of pipe is connected to one part of it, and an expander is connected to it through fittings. It is better to place it at some distance from the pump so that pressure differences are not created. An important point is that the piping section of the membrane tank must be straight.

A ball valve is installed after the tee. It is necessary to be able to remove the tank without draining the coolant. It is more convenient to connect the container itself using an American nut. This again makes installation/disassembly easier.

Please note that some boilers have an expansion tank. If its volume is sufficient, installing a second one is not required.

The empty device does not weigh much, but when filled with water it has a significant mass. Therefore, it is necessary to provide a method of mounting on the wall or additional supports.

Circulation pump

The circulation pump ensures the operation of the closed heating system. Its power depends on many factors: the material and diameter of the pipes, the number and type of radiators, the presence of shut-off and thermostatic valves, the length of the pipes, the operating mode of the equipment, etc. In order not to go into the intricacies of calculating power, the circulation pump can be selected according to the table. Select the nearest larger value for the heated area or the planned thermal power of the system, and find the required characteristics in the corresponding line in the first columns.

In the second column we find the power (how much coolant it can pump in an hour), in the third - the pressure (system resistance) that it is able to overcome.

When choosing a circulation pump in a store, it is advisable not to save money. The entire system depends on its performance. Therefore, it is better not to save money and choose a trusted manufacturer. If you decide to buy unknown equipment, you need to somehow check it for noise levels. This indicator is especially critical if the heating unit is installed in a residential area.

Strapping scheme

As mentioned earlier, circulation pumps are installed mainly on the return pipeline. Previously, this requirement was mandatory, today it is only a wish. The materials used in production can withstand heating up to 90°C, but it’s still better not to take risks.

In systems that can also operate with natural circulation, during installation it is necessary to provide for the ability to remove or replace the pump without the need to drain the coolant, as well as for the possibility of operation without a pump. To do this, a bypass is installed - a workaround through which coolant can flow if necessary. The installation diagram of the circulation pump in this case is shown in the photo below.

In closed systems with forced circulation, a bypass is not needed - without a pump it is inoperative. But two ball valves on both sides and a filter at the inlet are needed. Ball valves make it possible, if necessary, to remove the device for maintenance, repair or replacement. The dirt filter prevents clogging. Sometimes, as an additional element of reliability, a check valve is also installed between the filter and the ball valve, which will prevent the coolant from moving in the opposite direction.

Connection diagram (piping) of a circulation pump to a closed-type heating system

How to fill a closed heating system

At the lowest point of the system, usually on the return pipeline, an additional tap is installed to feed/drain the system. In the simplest case, this is a tee installed in a pipeline, to which a ball valve is connected through a small section of the pipe.

In this case, when draining the system, you will need to substitute some kind of container or connect a hose. When filling the coolant, a hand pump hose is connected to the ball valve. This simple device can be rented at plumbing stores.

There is a second option - when the coolant is just tap water. In this case, the water supply is connected either to a special boiler inlet (in wall-mounted gas boilers), or to a ball valve similarly installed on the return line. But in this case, another point is needed to drain the system. In a two-pipe system, this may be one of the last radiators in a line, with a drain ball valve installed at the lower free inlet. Another option is presented in the following diagram. Shown here is a closed-type single-pipe heating system.

Diagram of a closed one-pipe heating system with a system power supply unit