Heating is the key life support system of a private home and its stable operation is very important. One of the parameters that needs to be monitored is blood pressure. If it is too low, the boiler will not work; if it is too high, the equipment will wear out too quickly. To stabilize the pressure in the system, an expansion tank for heating is required. The device is simple, but without it the heating will not work for a long time.
Why do you need an expansion tank for heating?
When the heating system operates, the coolant often changes its temperature - it either heats up or cools down. It is clear that the volume of liquid changes. It either increases or decreases. Excess coolant is forced out into the expansion tank. So the purpose of this device is to compensate for changes in the volume of coolant.
Types and device
There are two water heating systems - open and closed. In a closed system, coolant circulation 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 a closed expansion tank for 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 tank.
An open heating system does not require a circulation pump. In this case, an expansion tank for heating is simply any container - even a bucket - to which heating pipes are connected. It doesn't even require a lid, although it may have one.
In the simplest version, it is a container welded from metal, which is installed in the attic. This option has a significant drawback. Since the tank is not sealed, the coolant evaporates and it is necessary to monitor its quantity - top up all the time. This can be done manually - from a bucket. This is not very convenient - there is a risk of forgetting to replenish water supplies. This threatens to cause the system to become airy, which can lead to its breakdown.
Automated water level control is more convenient. True, then, in addition to the heating pipes, you will also have to run a water supply into the attic and also somewhere to route the overflow hose (pipe) in case the tank overflows. But there is no need to regularly check the amount of coolant.
Volume calculation
There is a very simple method for determining the volume of an expansion tank for heating: 10% of the volume of coolant in the system is calculated. You should have calculated it when developing the project. If this data is not available, you can determine the volume experimentally - drain the coolant, and then fill in a new one, measuring it at the same time (put it through a 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. From this figure we find 10%.
Formula
The second way to determine the volume of an expansion tank for heating is to calculate it using the formula. Here you will also need the system volume (indicated by the letter C), but other data will also be needed:
- the maximum pressure Pmax at which the system can operate (usually the maximum boiler pressure is taken);
- initial pressure Pmin - from which the system begins operation (this is the pressure in the expansion tank, indicated in the passport);
- coolant expansion coefficient E (for water 0.04 or 0.05, for antifreeze it is indicated on the label, but usually in the range of 0.1-0.13);
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 bothering with them? If the system is open, the answer is clear - no. The cost of the container does not depend very much on the volume, plus you can make it yourself.
Expansion tanks for closed-type heating are worth counting. Their price depends greatly on volume. But, in this case, it is better to take it with a reserve, since insufficient volume leads to rapid wear of the system or even its failure.
If the boiler has an expansion tank, but its capacity is not enough for your system, install a second one. In total, they should give the required volume (the installation is no different).
What will result from insufficient expansion tank volume?
When heated, the coolant expands, its excess ends up in the expansion tank for heating. If all the excess does not fit, it is released through the emergency pressure relief valve. That is, the coolant goes into the sewer.
Then, when the temperature drops, the volume of coolant decreases. But since there is already less of it in the system than there 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 is operational. When the lower limit is reached, the equipment is locked. If you are at home at this time, you can correct the situation by adding coolant. If you are not there, the system may unfreeze. By the way, working at the limit also does not lead to anything good - the equipment quickly breaks down. Therefore, it is better to play it safe and take a slightly larger volume.
Tank pressure
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 working one.
The heating system of a low-rise private house usually operates at 1.5-1.8 atm. Accordingly, there should be 1.2-1.6 atm in the tank. The pressure is measured with a conventional pressure gauge, which is connected to a nipple located in the upper part of the container. The nipple is hidden under a plastic cover; unscrew it and gain access to the spool. You can also relieve excess pressure through it. The principle of operation is the same as that of a car spool - you bend the plate with something thin, bleeding the air to the required levels.
You can also increase the pressure in the expansion tank. To do this, you will need a car pump with a pressure gauge. Connect it to the nipple and pump it up to the required readings.
All of the above procedures are carried out with the tank disconnected from the system. If it is already installed, there is no need to remove it. You can check the pressure in the expansion tank of the heating system 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 has been drained from the boiler. For the accuracy of measurements and tank settings, it is important that the pressure on the boiler is zero. That’s why we drain the water carefully. Then we connect the pump with a pressure gauge and adjust the parameters.
Where to put it in the system
The 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 way the system works more reliably. So the specific installation location depends on where you have the circulation pump.
It is connected to the system via a tee. You cut a tee into the pipe, direct the perpendicular outlet upward, and screw the tank onto it. If the wall does not allow you to place a container, you will have to make an elbow, but the tank will be turned upward. Now we can assume that the expansion tank is installed.
But for the convenience of checking, it is advisable to install another tee after the tank, and install a shut-off valve on the free outlet of it. This makes it possible to check the membrane tank without draining the entire system - it cuts off the tank. Turn off the tap and bleed water from the boiler. Check the pressure on the disconnected branch (in the boiler). It must be zero. Afterwards you can carry out all other setup work.
1.Types of expansion tanks
2. Features of installation of expansion tanks
3. Mistakes made when installing an expansion tank
Today, it is possible to install a heating system in a private home in the shortest possible time.
The main thing that is necessary for this is sufficient financial capabilities of the property owner, and then the plan will be implemented, since the domestic building materials market offers a wide selection of heating equipment and components.
One of the main points of creating a system is the installation of an expansion tank in the heating system.
The performance of the heating network of a private home largely depends on it.
Types of expansion tanks
The place where the expansion tank of the heating system, such as in the photo, should be installed is determined based on the type of structure, which can be:
- open;
- closed.
It should be noted that heating systems made of an open type are installed extremely rarely today.
They are found in buildings built about several decades ago. The expansion tank, which is designed as an open type, looks like a container with an open upper part and a threaded connection at the bottom, at the bottom. It is used to connect an open type expansion tank for heating. The tank of such an outdated model is located at the highest point in the system.
In a closed-type heating structure, an expansion device is used, the installation and further operation of which has its own characteristics and differences.
The tank is made in the form of a sealed capsule having two chambers, separated from each other by a rubber membrane. Therefore, the product is also called a membrane expansion tank for the heating system.
The installation of a closed expansion tank is allowed anywhere in the heating network, with the exception of inserting a container after the circulation pump in the immediate vicinity of it.
Otherwise, pressure surges throughout the system are possible.
The operating principle of a closed tank is simple. After the coolant has heated up and increased in volume, its excess fills the empty space in the membrane device. As a result, the pressure in the system continues to remain at an acceptable level (read: “Selecting an expansion tank for heating”).
Installation of an expansion tank in a heating system is carried out taking into account some points:
- installation of the device is allowed in a room where the temperature does not fall below zero;
- easy access to the air valve should be provided in order to regulate the pressure in the air part of the tank if necessary;
- when the installation of the device is completed, there must be access to the shut-off equipment, drain tap and nameplate;
- it is impossible to allow the application of a static load to the membrane tank (pressure from pipes and other devices);
- if the reducer is located after the water meter, this measure will allow maintaining a constant initial pressure in the membrane tank.
When the safety valve is activated, the pressure should not exceed the level of the maximum permissible operating pressure in the tank (read: “Safety valve for heating - what are they, how to use it correctly”);
- The expansion tank for heating is mounted in such a way that the safety valve is located up to the flow fittings in the direction of flow of the coolant.
A heating scheme with an expansion tank always provides that it is installed only on the side from which cold water is supplied to the heating boiler.
Installation of the device at the exit is prohibited.
Mistakes made when installing an expansion tank
Many property owners try to carry out many of the work on arranging the heating system themselves, including installing an expansion tank with their own hands.
At first glance, it seems that there will be no problems with such work, but in reality it has certain difficulties, which is well known to specialists.
The most common mistakes made when installing an expansion tank in a heating network occur for a number of reasons:
- lack of a complete set of necessary tools or their poor quality.
When performing work, they often use wrenches - universal (gas) and adjustable.
In addition to them, a special wrench is also required, which is necessary when installing a metal-plastic pipeline, and a stepped wrench for detachable connections;
- use for compacting materials that are not intended for these purposes. For example, instead of high-quality sealant, they use cheap products for windows made of polyvinyl chloride, which are intended for a different temperature regime.
The first time after application, the connections look attractive, but after commissioning the heating structure, this type of sealant cannot withstand the load and high operating temperatures.
Expansion tank for heating - installation diagram in open and closed systems
It’s good if a leak is discovered as a result, but often the consequences are more serious;
- the installation of the expansion tank in the heating system was carried out in a hard-to-reach place and access is almost impossible;
- The volume that the expansion tank should have was calculated incorrectly, or the device was purchased at random.
It should be noted that the installation and fastening of the heating expansion tank must be carried out in accordance with accepted standards and regulations that ensure safe operation.
Before installation, you must correctly determine the installation location of the device.
After completing the installation of the expansion membrane tank on your own, everything seems to look great, and the inaccuracies made during this process are invisible. The shortcomings will become obvious after the heating season has started, and the main thing is that this will happen at the most inopportune moment.
For example, it’s freezing outside and the heating system is out of order.
Watch a video on installing an expansion tank in a heating system:
In order to avoid problems in the future, you need to familiarize yourself with the recommendations from the manufacturer for installing such an element of the heating supply system as an expansion tank.
This information will help you avoid unnecessary expenses: time, physical and financial.
One of the key elements of the cooling system in a modern car is the expansion tank. This is a kind of reserve reservoir for additional fluid during system operation.
I'm thinking about the value of the reservoir, which looks for faults in the thermostat or the radiator itself.
However, problems with the expansion vessel are often caused by air overload in the cooling system, which leaves the car without heat during the cold season.
An alarming symptom for a car owner is regular engine overheating. It's important to check the status of this part, but first you need to know exactly how the device works.
What is the purpose of a expansion vessel and how does it work?
The urgent need for such a reservoir was created when, instead of cooling water, a special liquid was used that was able to retain its physical properties even at extremely low temperatures.
The basis of these solutions is alcohol and ethylene glycol (less commonly propylene glycol).
As it heats up, the alcohol expands and begins to leak through the radiator fan valve under pressure. During the ICE cooling process, the temperature of the antifreeze or antifreeze is reduced due to the formation of an emptied void.
How to fill a heating expansion vessel?
The spaces are filled with air, which, with the subsequent activation of the engine, creates plugs that prevent the free passage of liquid into the cooling system. This can lead to general engine overheating.
To avoid overheating problems, an expansion vessel was supported, which was connected to the radiator by a pipe. The center of the reservoir is level with the top of the radiator, so that the heated liquid rises up and freely penetrates from the radiator space into the reservoir.
The hose itself is attached to the bottom of the product, allowing excess antifreeze or antifreeze to flow back to the radiator during cooling without drawing air.
Where is the expansion tank
Depending on the model, the reservoirs are located in the most suitable areas of the cooling system.
A container is needed next to the radiator.
The material for making the container is durable and transparent plastic. In one part of the product there are always scale marks that allow you to monitor the level of antifreeze in the system. The last mark below shows the minimum fluid level.
The maximum amount of wind chill antifreeze should be just over 30mm above the top risk level on the tank scale.
Main problems and malfunction of the expansion vessel
Most often, car owners complain about a problem such as a leaking expansion vessel.
This may be due to a violation of the integrity of the tank (for example, after an unsuccessful parking or other collision), as well as to violations of the pipeline that connect the drain tank and the radiator.
The strong pressure in the container is emptied using a special release valve on the container lid. It is necessary to carefully monitor the condition of the cover, remove it from the scale and corrosion, otherwise the valve and the entire system will quickly work.
A fault in the expansion vessel causes a large drop in fluid in the engine cooling system, which has a very negative effect on its operation.
Installation of an expansion tank for closed heating
Installing an expansion tank for closed-type heating allows you to equip a heat supply system in a private house in the shortest possible time.
The main thing in this matter is that there is enough finance to implement the idea. Today, the Russian building materials market presents a large assortment of heating equipment, as well as components for heat supply schemes.
When arranging a heating system, the installation of a closed heating expansion tank is considered very important.
The functionality of the entire heating network of the home will depend on this detail in the future.
Types of expansion tanks
Elements to prevent air leaks into the line come in different designs.
Based on this, specific installation of the expansion tank of the heating system is carried out. There are closed and open heat supply schemes.
Installing an expansion tank in an open heating system is rarely used.
As a rule, it is typical for buildings of the Soviet period. An expansion tank, the design of which is made according to this type, is a container with an open top and a threaded connection in the lower part, at the bottom. Using such a connector, an open type element is connected to the heating circuit. The installation diagram for an open expansion tank for heating provides that it must be located at the highest point of the system.
The closed-type heating structure has a special structure, so the installation of an expansion tank for closed-type heating has its own characteristics.
The container is made as a sealed capsule, which has two chambers separated by a rubber membrane. Therefore, this design is also called a membrane tank of a heating system. This part is used anywhere in the heating system except for the place behind the circulation pump, as well as directly next to it.
Failure to comply with this precaution may result in pressure drops within the system.
The installation diagram of an expansion tank in a closed-type heating system is simple.
The heated coolant expands, its excess squeezes air out of the membrane device, and the system pressure remains unchanged.
Features of installation of expansion tanks
The installation of a vacuum heating expansion tank must take into account certain aspects:
- installation of the structure is carried out in a room with a positive temperature;
- it is necessary to provide free access to the air valve to adjust the pressure if necessary;
- upon completion of the tank installation, access to the drain valve and shut-off equipment is left free;
- The installation diagram of a membrane expansion tank for heating is carried out so that the safety valve is located before the flow fittings.
In order to correctly install the expansion tank in the heating system, you will need the following tools:
- adjustable and stepped wrench;
- wrench for installing PVC pipes.
First you should do the preparatory stage, which includes disconnecting the boiler from the gas, electricity or water supply.
Then turn off the tap, which is responsible for the circulation of the coolant, and it is drained from the system.
Step-by-step steps for installing an expansion tank in a closed heating system:
Why do you need an expansion tank for a closed heating system?
Install a drain and shut-off valve on the supply pipe to drain and shut off the water.
2. Using screws, connect the expansion tank to the system.
If the options for installing an expansion tank in the heating system require the presence of polypropylene pipes, a soldering apparatus, fittings, couplings and angles should be used.
Before installing the fitting, it is necessary to wrap linen tape around the threads and apply sealing paste.
4. After draining the water from the system, cut the pipe with scissors and install a tee.
Before putting the system into operation, be sure to blow out the coarse filter.
Be sure to check the operating pressure using a pump.
7. After connecting the expansion tank to the network, turn on all coolant supply taps and turn on the boiler.
It is advisable to install a safety valve, which comes with the container; if it is not available, it costs to buy it separately.
Read also:
— DIY shower cabin made from tiles in the photo and manufacturing tips
— How to install a toilet on tiles with your own hands without preparation
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— Can you rearrange the wall-hung toilet after installation or not?
– Private house – heating installation and pipe laying options
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In order to compensate for the thermal expansion of the coolant, open or closed tanks are installed in the heating system. They come with natural and forced circulation. The volume of liquid tends to change as the coolant expands and contracts during operation.
To stabilize the pressure on the internal walls of the elements in the heating system, as well as to compensate for changes in the volume of liquid, expansion tanks are used.
Types of tanks
2. Open type expansion tank
2.1 Advantages and disadvantages
2.2 How an open tank works. Installation Rules
3. Closed expansion tank
3.1 Membraneless tanks
3.2 Membrane tanks
3.3 Advantages and disadvantages of a membrane tank
3.4 How to choose a membrane tank
3.5 Installation of closed expanders
Types of tanks
There are two types of expansion tank:
- Open type expansion tank.
- Closed expansion tank.
When the temperature of the liquid in the pipeline decreases and for its natural return, an open tank is installed at the highest point of the heating system.
A tank of this type is a volumetric container that communicates with the atmosphere.
A closed-type expansion tank has the form of a sealed vessel, which is filled one half with liquid, and the other half with gas or air, which is under pressure.
After heating, the liquid moves into the expansion chamber, and the gas is compressed at this time. The liquid returns back after cooling, and the resulting difference in volume is filled with gas.
Open type expansion tank
Let's take a closer look at all the features of an open tank. The tank is used when there is a small leak to replenish water. And also for taking air from the system.
Such a tank can be cylindrical or rectangular and is usually made of steel or polymer materials.
Since the expansion chamber is installed at the top, the heating pipelines must be long. To service this device, as well as to clean it from dirt, there is a lid on top of the tank.
You can install an open-type expansion tank in a special room on the roof of the house, a staircase or in the attic.
If your house has high ceilings, then such a tank will fit well in a bathroom or utility room. indoors. If containers extend beyond the heated premises, they should be insulated to avoid heat loss.
Advantages and disadvantages
Advantages of open tanks:
- Relieves pressure and removes air from the heating system.
- Low cost of the device.
Disadvantages include:
- Large heat losses and the need to insulate some elements.
- Before installation, it is necessary to arrange additional heating pipelines.
- Since the system evaporates a certain amount of coolant, it needs to be replenished periodically.
- Possibility of corrosion of steel elements due to contact with the atmosphere.
Due to the shortcomings of this equipment, it is used less and less, giving preference to closed tanks.
How does an open tank work? Installation Rules
To prevent water from stagnating in the tank, it is necessary to arrange circulation. A circuit is installed between the tank and the pipeline. It should consist of a circulation and expansion pipe. The opening of the circulation pipe must be located 0.5 cm below the expansion pipe.
Due to circulation from the heating system, air bubbles are released into the atmosphere. This system is suitable for forced circulation. If the system is equipped with natural circulation, then it is necessary to connect an expander at the top of the supply pipeline.
Closed expansion tank
A closed tank has the appearance of a sealed vessel made of steel. Part of the tank is filled with inert gas, and the second part is filled with liquid. There are two types of closed expansion tank: membrane and membraneless.
Membraneless tanks
In such tanks there is no internal separation of space, so the coolant is in direct contact with the gas.
A gas cylinder or compressor is installed outside to maintain pressure inside the tank. Gas supply and pressure control occur automatically.
Membrane tanks
Membrane tanks are more popular because they are separated using a flexible membrane. Therefore, gas and liquid do not come into contact.
There are tanks with a disc-shaped membrane and with a pear-shaped (balloon) membrane.
The first membrane is attached in the middle of the tank and looks like a hemisphere.
It can become concave or convex depending on changes in water temperature.
The second membrane is similar to a vessel and is attached to different ends of the container. There is gas between the membrane and metal walls, so the coolant does not come into contact with the walls of the tank. Consequently, such a tank is protected from corrosion and has a long service life.
The membrane in this tank can be replaced. Expanders are produced with butyl and ethylene propylene membranes. They are highly durable.
Advantages and disadvantages of a membrane tank
Advantages of a membrane tank:
- It is not necessary to install thermal insulation;
- Heat loss is minimal;
- Works at high pressure;
- Small sizes;
- The tank can be installed almost anywhere;
- The tank is well protected from corrosion, as it does not come into direct contact with the atmosphere.
The disadvantages include:
- Periodic pumping of air or gas;
- Great cost;
- The pressure in the system must be controlled.
How to choose a membrane tank
Membrane tanks come in oval shapes and flat ones with a diaphragm.
The second option is more compact; it can be installed between the wall and the interior decoration. This way you will save space in your home. The main parameters of such a tank are the required volume of liquid. It is pre-calculated.
The service life of the tank depends on the quality and parameters of the membrane.
Main characteristics of the membrane:
- The material from which the membrane is made.
- Operating temperatures and pressure.
- Diffusion stability.
Tanks that are used for heating are painted red, and those that are used for the water supply system are painted blue.
Installation of closed expanders
If the tank is a closed type with forced circulation, then it is recommended to install it in front of the circulation pump.
Installation can be done in any position, but the best option would be the top liquid supply. Since air bubbles will be removed naturally. The tank will work even if the membrane is damaged.
Some heating devices already have an expansion tank built-in, in which case there is no need to install an additional one.
Do-it-yourself installation and installation of an expansion tank in a heating system
If you decide to change the water to another coolant, you may have to replace a tank with a higher volume. But you can also install an additional expander.
When installing a closed tank with natural circulation, it is necessary to install an automatic float valve. It is installed at the top of the system to vent air when the system is full. If, while using the tank, you notice that its volume is not enough for you, instead of buying a new one, it will be more profitable to install an additional tank of the required size.
A correctly selected and correctly installed expansion tank of the heating system will prevent its failure and will maintain the pressure at the required level. It is needed as a reserve for water expanding when heated. Depending on the type of system, the built-in expander can be open or closed.
We will tell you how to select a reserve capacity depending on the heating scheme being created. The article we presented describes the design features and specifics of installing expanders. Recommendations are given that, if followed, will ensure ideal operation of any type of heating circuit.
A design feature of open type expanders is the contact of the coolant with the atmosphere. The circulation in systems with an expander of this type is convection. When heated, the volume of liquid increases, its excess is absorbed by the reservoir of the container.
When the temperature drops, the liquid returns by gravity, under the influence of gravity.
Due to zero pressure in the tank, the device does not require a durable metal structure, therefore:
- any metal is used in the manufacture of the case;
- a ready-made container made of heat-resistant plastic can be used;
- The shape of the tank is not important.
In country houses, such equipment can be assembled from available materials. As a container, you can use a plastic canister or barrel equipped with an inlet pipe and an outlet for overflow.
Open type expanders can be made in the form of a rectangular tank with a leak-proof lid on the top plane
Externally, it is an ordinary metal tank, the upper plane of which is equipped with a hole for servicing and adding liquid. The leak-proof lid provides protection against clogging. Fastening units are provided at the bottom or on the side plane.
Image gallery
The expander itself can be installed at any point in the system, but when performing installation work it is advisable to take into account the following recommendations:
- the best place for installation is the return line, to the pump insertion point;
- It is better to supply coolant from above, which will reduce air penetration and maintain functionality if the membrane is damaged;
- the lack of main volume can be compensated by installing an additional expander with a smaller capacity.
When installing, it is not forbidden to take into account the interior of the room, if necessary. To control the level, the expander must be equipped with a pressure gauge.
A closed expander is usually placed in front of the boiler, before the circulation pump is installed
The possibility of placement close to the boiler eliminates the question of the need to insulate the tank. The equipment is located in a warm room, which ensures ease of use.
Which design is better?
Systems, depending on the design and material of the expansion tank, differ in the list of pros and cons. But, according to experts and experienced users, the advantages in functionality are on the side of closed options.
Pros and cons of an open tank
A self-flowing system requires larger diameter pipes, which in turn directly increases costs. The budget for installations with a leaky expander increases slightly, although it remains relatively small.
The main advantages of this option are simplicity, plus the low cost of components and installation work. Another positive feature is that there is no need to control the pressure level.
An open type expander for small systems can be assembled from available materials, and its installation will not be difficult
However, there are much more disadvantages:
- the use of anti-freeze is dangerous due to toxic fumes;
- installation possibilities are limited only by the top point of the system;
- constant contact with the atmosphere increases the risk of air locks and corrosion;
- slow warm-up;
- temperature changes accompanying convection circulation accelerate equipment wear;
- used in heating low-rise buildings, maximum two floors;
- large heat losses and energy consumption for heating.
Another disadvantage of an open system is losses from evaporation and overflows. Therefore, when installing the tank, care should be taken to ensure that the filler hole is accessible.
Image gallery
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 marking 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.
One of the advantages of an autonomous heating system is the ability to maintain a comfortable temperature in the house, regardless of the start and end of the heating season, and save on utility bills. Schematically, it consists of a heating boiler and a circuit through which hot coolant circulates. Water is usually used as a coolant. An important role in heating equipment is played by the hot water circulation system, which consists of several parts. The correctness of its operation largely depends on such a design element as the expansion tank.
An example of a heating system with an expansion tankLet's compare closed and open heating systems
The operation of an open heating system is based on the laws of thermodynamics, due to which the coolant moves. From an area of high pressure and corresponding temperature at the boiler outlet, water moves through pipes to an area of lower pressure, and its temperature decreases. The cooled coolant is sent back to the boiler and the process is repeated. Thus, natural circulation of liquid occurs, according to the laws of physics.
Since when water is heated, its volume increases, an expansion tank is provided in the design of an open heating system. For efficient movement of open-type coolant, the expansion tank is installed at the highest point of the system, and the heating boiler at the lowest. Installing an expansion tank in the attic seems to be the best option. Its device is not complicated.
Open type heating scheme Over time, water evaporates, so its level must be replenished in a timely manner. During breaks in the use of heating and at negative ambient temperatures, the water must be drained, otherwise it will freeze in the pipes and burst them. An open heating system has the following advantages:
- independence from electrical energy sources;
- no noise;
- ease of maintenance;
- quick start and stop.
You can select radiators for any type of heating system based on the recommendations of the article
In a closed heating system, water does not evaporate because it is sealed. The movement of the coolant is carried out using a pressure or circulation pump, which can be found in the article. In this case, for effective operation, an expansion tank made of durable metal is also required. A closed heating system consists of a heating boiler, a circulation pump, a pipeline network, radiators and an expansion tank. A closed heating system has the following advantages:
- no need to constantly monitor the coolant level;
- possibility of using antifreeze;
- internal pressure adjustment;
- possibility of connecting additional devices.
Closed heating system With proper installation of heating equipment, both options will work perfectly. The choice between them is determined by operating conditions and placement features. The differences between the two systems are as follows:
- In an open heating system, the expansion tank is located at the highest point. In a closed heating system it can be located almost anywhere.
- The likelihood of air locks forming in a closed heating system is much lower. This is due to increased internal pressure and lack of direct contact with the atmosphere.
- To operate an open heating system, large diameter pipes are required. Installation work is complicated by the need to take into account hydraulic rules when distributing flows, making turns, slopes, and so on.
- Small diameter pipes used in a closed heating system reduce its cost. Here it is important to correctly install the circulation pump so that during its operation it creates as little noise as possible.
Design and functions of the expansion tank in the heating circuit
The function of the expansion tank in an open heating circuit is to receive excess water when it expands due to heating, and return it to the system when the temperature drops. The container is not sealed, and the coolant is in direct contact with the environment, so water evaporates in an open heating system. The device has a simple design; if necessary, you can make it yourself.
Open type expansion tank The disadvantages of an open system include the need to constantly monitor the water level as it evaporates, the danger of freezing the liquid in the expansion tank, and the inability to use antifreeze as a coolant. In addition, air entering the system causes the formation of air locks, corrosion of internal parts and their cavitation.
In a closed heating circuit, the expansion tank is made of high-strength metal. The device consists of two halves, hermetically sealed to each other. The design includes a foot valve and an internal membrane. As the coolant temperature rises, the valve opens and excess liquid from the increased volume enters the expansion tank.
A diaphragm made of heat-resistant high-strength rubber divides it into two parts. Gas is pumped into the upper part of the sealed container, and a hot coolant enters the lower part, compressing the membrane and the gas environment located behind it. When the working fluid cools, due to the expansion of the gaseous medium, the diaphragm squeezes it back into the heating circuit.
The membrane tank can be installed horizontally or vertically in any position.
Closed type expansion tank device The performance of a closed expansion tank does not depend on its orientation in space, which cannot be said about its service life. To extend the service life of the membrane tank, it is better to position it so that the air chamber is on top. Over time, cracks appear in the diaphragm, and until their size and number reaches a critical level, the system will work properly when the container is placed vertically. In a horizontal position (if cracks appear in the diaphragm), air from its half will quickly penetrate into the coolant and vice versa, which will require an urgent replacement of the tank.
What does insufficient volume of the boiler’s built-in tank lead to?
Insufficient volume of the built-in boiler tank can lead to malfunctions of the heating system. When heated, the liquid expands and its excess enters the expansion tank. If its volume is insufficient, the tank overflows and the emergency pressure relief valve releases the coolant into the drain. The remaining cooled coolant is returned to the heating circuit.
Pressure in the system when the volume of the expansion tank is insufficient As a result of a decrease in its quantity, the internal pressure in the system decreases. If it decreases by a small amount, the boiler will function; if the pressure decreases significantly, the operation of the heating equipment will be blocked.
If the coolant level is not promptly replenished to normal, the system may defrost, so such emergency situations should not be allowed to occur.
Calculation of the required volume of the membrane tank
The required volume of the membrane tank is calculated using a simple formula. Its value is ten percent of the total amount of coolant circulating through the system, if water acts in this capacity. The total volume of coolant can be determined by the readings of the water meter when filling the heating system.
A more accurate figure is obtained by summing the volume of all pipes, the capacity of the boiler and batteries. It is believed that fifteen liters of coolant are required per kilowatt of boiler equipment power, that is, the total volume of liquid is determined by multiplying the nameplate power of the boiler by fifteen. This value will be within the permissible error.
Illustration of the change in volume in the tank due to pressure fluctuations in the systemFor example, if heating equipment requires three hundred liters of water to operate, then the volume of the membrane tank should be thirty liters. This parameter increases by fifty percent when using non-freezing liquid as a coolant, that is, in this case, the required volume will be forty-five liters. In addition, it is necessary to take into account the possibility of leaks and increase the calculated value by approximately three percent. If the size of the membrane tank is correctly determined, the emergency pressure relief valve does not operate.
Setting the optimal pressure in the tank
Before connecting the expansion tank and filling it with coolant, it is necessary to set the optimal pressure in its air chamber corresponding to this parameter in the heating network. To perform this procedure, a plastic cover is removed from the air compartment, under which there is a nipple, the same as in car tires. The pressure measured by the pressure gauge is adjusted to the desired value by pumping it up using a pump or by bleeding it by pressing the nipple rod.
The protection group controls the pressure in the system The optimal pressure in the tank is obtained by adjusting the internal pressure in a closed heating system downward. This is done so that the rubber diaphragm is pressed on the coolant side. Otherwise, when it cools down, air will be drawn through the automatic vents, which should not be allowed under any circumstances. For example, if the internal pressure in the network is 1.2 atmospheres, then its optimal value in the expansion tank will be one atmosphere. After setting this value, you can open the tap and fill the system with coolant.
At intervals of six months, it is necessary to check the pressure in a closed compensation tank and carry out a visual inspection for mechanical damage.
If there is a sudden change in internal pressure and temperature in the heating network, there is a risk of damage to the membrane, in which case it will need to be replaced. To do this, you need to perform the following manipulations:
- Disconnect the expansion tank from the main line;
- release the pressure in it by pressing the spool rod;
- remove the damaged membrane, drain excess water and install a new one;
- Having established the optimal pressure, attach the container in place.
Selecting the location for installing the expansion tank
Installation of the expansion tank depends on the type of heating system and the purpose of the tank itself. It is better to install a closed compensation tank on the return line in front of the heating boiler and circulation pump.
Options for placement and installation of the expansion tank If it is located on the supply line, the service life of the membrane will decrease due to constant exposure to a higher coolant temperature. In addition, in this case, if an emergency occurs, steam may penetrate into the expansion tank, as a result of which the diaphragm will no longer compensate for the coolant pressure, since the mixture of air and steam is a compressible medium.
The expansion tank is connected through a shut-off ball valve. This is done so that, if necessary, the compensation tank can be quickly replaced without waiting for the coolant to cool down. Installing a second tap makes it possible to pre-drain hot water from the tank.
How to properly install a closed expansion tank with your own hands
The connection diagram is not particularly complicated. You can correctly install a closed expansion tank with your own hands by following the following connection diagram. The preheating boiler is de-energized, the coolant supply is shut off, and the water from the radiators is drained.
If polypropylene pipes are used for installation, you will need a special soldering iron for their installation. You will also need couplings and corners. It is better to use “American” fittings, as it makes it possible to easily remove the container for maintenance and repairs. Below is a sequential diagram of actions for installing an expansion tank.
- A sealing thread is wound onto the threaded part of the tank fitting.
- An adapter is screwed onto the fitting to install the tap.
- A sealing thread is wound onto the threaded part of the adapter.
- A shut-off valve is installed on the adapter.
- A sealing thread is wound onto the threaded part of the “American”. The “American” is screwed into the tap using pliers and an adjustable wrench.
- A sealing thread is wound onto the threaded part of the angle. The corner is wrapped in “American”.
- A clamp is placed on the tank body to secure the tank, which is included in the delivery set.
- On the opposite side of the tank there is an air injection nipple onto which a plastic cap is screwed.
After placing the expansion tank in the selected location, the quality of all connections is checked, and coolant is supplied to the system. After the internal pressure in the batteries reaches the calculated values, the air pockets are released from them, and the heating system starts at full power. The compensation tank is installed so that it is convenient to service, that is, free space is left between it and the wall.
All connections must be sealed with sealants that are resistant to high temperatures, otherwise leaks will inevitably occur. The membrane expansion tank in a closed heating system is installed on the cold water supply side. When performing all manipulations, it is necessary to comply with safety requirements.
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