Home Article How to replace an expansion tank in a boiler

How to replace an expansion tank in a boiler

Expansion tank of the open heating system

After the installation work on inserting the tank into the common network, it is set up. In this case, the main task is to achieve the desired pressure corresponding to the heating system. This setting concerns closed tanks and is carried out as follows:

  • After installing the expander, the system is filled with water;
  • Tight air from radiators and pipes, for this they use the valves and cranes of Maevsky;
  • measure pressure (manometer) in the air compartment of the tank and in the rest of the system;
  • According to the rules, the pressure in the tank should be 0.2 bar lower than in the rest of the circuit, such a difference is achieved by puffing and pumping up the pressure compressor in the chamber.

If, as a result of calculations, the pressure in the system should be 1.3 bar then in the air compartment of the tank it must be lowered to a value of 1 bar. This is necessary that sufficient pressure is on the rubber “pear” from the water from the water, and when the coolant is cooled, the air does not occur. After such a system adjustment, they turn on the boiler, now the pressure in the extensor will increase smoothly, regardless of whether the liquid cools or heats up.

The connection diagram of the membrane tank to the closed heating system. All parts of the structure are indicated by numbers.

Types. open tanks

Open expansion tanks are characterized by the fact that they must be installed exclusively at the highest point of the heating system. Such a place can be, for example, the attic. But the obstacle to the expansion of the coolant is not the only function of this type of device, since they also prevent boiling water in the pipes and make up for its reserves in cases where for any reason there was a leak.

The tank can be used both with natural and forced circulation.

  • If the circulation is natural, then the tank must be connected to the highway, due to which it will also be “part.time”.
  • If the coolant moves along the system forcibly, then the tank is already connected to the reverse pipe, so that the water in the system does not boil.

In general, an open tank is a tank from which four tubes come out:

The expansion tube leads to the heating system, which is located at the top of the capacity. There is also an overflow tube necessary in cases where the container is overflowing and you need to take the water to the sewer. From below, respectively, there is a signaling tube equipped with constipation, and circulation is needed so that the coolant does not freeze in the tank, and the total temperature is maintained permanently. If desired, you can take another additional measure that would “insure” the circulation pipe. to insulate the tank with a thermo.insulating material.

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Important! To date, such tanks are practically not used in heating systems due to a large number of shortcomings. Among such shortcomings, I would like to highlight the following:

Among such shortcomings, I would like to highlight the following:

  • Such systems are not adapted to high pressure.
  • Their design is very bulky and overall.
  • Due to the fact that the system is open, air also enters the pipeline along with water, which has the most negative effect on the surface of the pipes. corrosion is formed on them soon. The same applies to other metal elements.
  • Such tanks should be installed only at the highest point, and this, you see, additional costs.

Do you need an extensor tank for a wall.mounted gas boiler Baxi?

The volume of the built.in expansion tank of the Baxi boiler is indicated in the characteristics and for the Ecofour series is 6 liters to answer the question of its need in a single heating system. you need to know the total volume of this system.

It is not so difficult to calculate it: the volume of filling the boiler and radiators is in their characteristics, and the volume of filling of pipelines can be calculated, knowing their diameter and total length. Water, after heating by 80 degrees Celsius will increase by about 4-5%, therefore, the recommended volume of the expansion tank is 8% of the total volume of the heating system in case of water filling and 12%-in the case of using antifreeze as a coolant (the coefficient of thermal (thermal coefficient more antifreeze extensions). Thus, the full.time expansion tank will be enough for a heating system with a volume of about 75 liters when using water and up to 50 liters when using non.freezing liquid.

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

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

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Extending tank for heating closed type

The main advantage of the tank for a closed heating system is its compact dimensions and the possibility of installation on any section of the circuit.

When installing, according to the approved standards, there are no clear restrictions in choosing the installation site. However, in many schemes, the reservoir is located near the pump.

Due to the tightness of the tank, the pressure inside the contours can grow to a high level. To protect the design, it is important to provide for the presence of a “security group”.

  • Safety valve with a given upper pressure threshold.
  • Air vent with automation support.
  • Manometer or manometer with the thermometer to perform control and measuring tasks.

However, the need to organize a “security group” is not a minus, since it is explained by the specifics of the system.

The disadvantages of tanks for closed types include their high cost and the need for independent purchase.

But advanced models are delivered with an already installed tank. This applies to wall.type units.

Device and principle of operation

To determine which expansion tank is needed for heating, you should study the device and principle of operation of structures for a closed heating system. The performance of such a tank is quite simple. Depending on the model, it may vary slightly, while the specificity of the work remains the same. It implies the separation of hermetically closed fluid in 2 chambers using a special elastic partition. One part is connected using the pipe to the contour of the system and is called water. The second (air) is intended for organizing optimal pressure.

The design of the tank provides for the presence of such components:

As a case, in most cases, the national.stamped design of a cylindrical shape is used (other options are available on the market).

How to replace a hot water expansion tank

The inner surface of the walls has a protective coating against corrosion and an enamel layer. The color of the case is red, since the stores also offer tanks-hydro-accumulators, which differ in blue, notifying about the impossibility of working with hot liquid.

The tank has a threaded pipe for connecting the tank to the heating circuit. Leading manufacturers are supplied with the fittings and the union-American tank, which simplifies the installation process.

On the opposite side of the case there is a nipple or spool resembling a bicycle. With its help, pressure is pumped in the air chamber.

The next important node is the membrane dividing the internal volume of the tank into 2 separate parts. In some cases, an additional membrane tank is installed, which is used when the main membrane fails. According to this principle, an expansion membrane tank is needed.

For the manufacture of this part, elastic materials with a minimum diffusion indicator are used. For a long time, their role was served by rubber, but due to fragility, he lost his popularity. In modern devices, it is customary to fix ethylene-protopylene or butyl elements.

The role of the air chamber consists in creating excess pressure, which lowers the membrane down and provides the minimum volume of the water chamber until completely filling.

Когда система заполняется жидкостью и включается в работу, контур нагнетает давление, а поверхность мембраны начинает изгибаться. This indicates an increase in the volume of the water chamber.

Depending on the intensity of heating, the degree of expansion can be of different. Excess heat carriers move into the tank of the tank, where they cool, acquire the same volume, and the membrane is squeezed down. As a result of such actions, the optimal pressure balance is ensured.

In the case of any malfunctions, due to which the coolant cannot expand more, a safety valve, which lies excess and restoring equilibrium, enter the work.

Often a membrane can have a non.traditional form. So, on sale are available tanks of the cylinder type, where it is an elastic cylinder with hermetically fixed edges.

This reservoir acts as a water chamber, and the remaining space is used as a airy chamber with a given pressure. In the case of the expansion of the liquid, the walls of the membrane begin to stretch, and it becomes weather on the pear. In this case, the volume of chambers with air decreases, and pressure values ​​continue to grow.

Such tanks are widely in demand in the water supply system, since they are easy to install and maintain. When you understand whether the expansion tanks need to be grounded, it should be taken into account the principle of their work, placement and functionality (if the knot is fixed near the furnace, grounding is required).

What volume should the expansion tank have in the closed heating system

On the market you can find entire series of tanks with different indicators of the working volume. To find the most optimal option, you need to conduct some calculations, guided by the following formula: VB = VC × K / D.

VB value indicates the minimum volume of the tank, VC. displays the total volume of the heating system, and K is an indicator of the liquid expansion coefficient.

D. The effectiveness coefficient of the tank, which can be determined using this formula: D = (1m. QB)/(qm 1).

QM is the upper indicator of the permissible pressure in the heating system and determines the valve operation force from the Security Group.

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QB indicates pre.created pressure in the air type. In the presence of built.in pumping, such an indicator will be indicated in the technical documentation. Sometimes the pressure level is regulated by a car pump with a pressure gauge.

To simplify the process of calculating the volume, you can use special online calculators.


If your expansion device has become unusable, for example, burst a membrane, or installation on the boiler made by your own hands is required, the question arises of how to replace or install a tank?

It’s easy to change it by installing it in its former place. Tanks for gas double.circuit boilers usually have a flat round or rectangular shape and are attached on the side wall of the heat generator inside or outside. For the installation of a new one, you should adhere to the recommendations below.

The capacity is connected to the system in the area with minimal pressure and lower water temperature, t.e. in the reverse circuit to the circulation pump, immediately after the boiler. Why exactly? The pump, as a rule, is limited to cutting taps. In case of any action with the pump, the taps close.

It may happen that after the measures taken with the pump, the taps will remain closed. This threatens the boiler explosion. Installation is carried out in places where it will least interfere, for example, in the corner, in the immediate vicinity of the boiler. The wall on which the installation will occur should be strong, concrete or made of brick.

First of all, you should reliably fix the container on the wall using brackets. The tank should not be loaded with the weight of the pipes, t.e. They are attached to the wall separately. He should not come close to the wall, there should be a gap for free access. Regarding the upper or lower eyeliner to the pipes of opinions contradictory.

Some bring pipes from above, motivating that in this position it is easier to remove air. The opinion of experts. eyeliner should only be done from below, since sooner or later cracks are formed on the rubber membrane. With the lower installation method, the air will flow through microcracks into the liquid, but not as intensively as in the opposite position, the tank will last longer.

Example installation of an expansion tank

over, on some models, the fitting is installed at the bottom and from the side, and do not connect the capacity differently. Then you should connect the fitting on the tank with the return pipe of the corresponding diameter.

If the pipes are made of polypropylene, the connection occurs through the tee, the metal.plastic pipe should be cut and connected through the tee on the fittings, the pipe with threads must be welded in the steel pipes.

Next, a cutting crane is wound on the thread, an American is installed on it and connected by a pipe to an expansion tank. Experienced craftsmen recommend installing emergency drain on the tank, which is used infrequently, but in an emergency, it will quickly drain the water from the expansion capacity. To do this, a tee is installed behind the American, the side exit of which is equipped with a tap, it is through it that drains in emergency situations.

What is an expansion tank

Recall: if we try to squeeze water (that is, in our case, to fit the increased amount of the coolant into a given volume of the heating system), the pressure is growing. So that the excess water formed during heating does not spoil the pipes and devices, you need to drain it somewhere, as in a measured container in experience.

But we cannot drain water from the heating system. So, the excess must be temporarily “put off” in some “”, so that later, when the water temperature decreases, and its density increases, it return to the system, and the water took the same volume that it was originally.

How to Install An Expansion Tank

Expansion tank in the heating system

In the heating system, such a “” taking excess water formed during thermal expansion is an expansion tank. Its task is to be a damper (compensator) of pressure in the system.

Features of installation

Preparatory events. Before starting work, the boiler is disconnected from the mains. And also overlap the water supply and drain the entire liquid from the system.

Usually, polypropylene pipes are used to connect the system parts, they are welded with a special soldering iron with additional fittings in the form of couplings and corners for fitting.

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It is preferable to take an “American”, its advantage is that it will be easy to remove the tank if necessary. The “American” consists of two parts: one is attached to the thread on the expansion tank, the second. to the first. Then the pipe is soldered to the second part. To ensure the reliability of the connection of fitting with the tank, a seal in the form of a paste or flax is applied to the thread, the fitting is fixed on the thread with a gas key.

When installing, you should adhere to some rules:

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  • Do not put the tank close to the walls or in hard.to.reach places;
  • The height of the mount is such that it is easy to reach the spool or cutting crane;
  • Pipe or reinforcement should not put pressure on the tank pipe;
  • It is impossible to place the supply pipe in the aisle on the floor or above the head;
  • If the container is in the attic, it is recommended to wrap it with insulation;
  • organize overflows, otherwise water can pour the ceiling in case of breakdown.
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Unipump. Expressive tanks

Expressive tanks for a gas or solid.fuel boiler (expansomes) with the Unipump brand are designed to compensate for increased temperature expansion of the coolant in closed heating and hot water systems (DOS). Water heaters can also be installed.

There is carbon steel in the manufacture of an expansion tank for a heating system, including for a warm floor, and the outer shell of the tank for a gas boiler or a flowing, storage water heater (household boiler, including indirect heating) is painted with enamel. Inside the case is an EPDM membrane (synthetic ethylene/propylene elastic rubber). Air is pumped into the cavity between the tank body and the outer surface of the membrane.

You can get acquainted with the instructions for the installation and operation of different models that are filled with the directory, you can here.

With an increase in temperature, the coolant expands and the internal elastic membrane is stretched, and when cooling, it is squeezed out of this membrane.

  • The operating temperature range is from 0 to 90 ° C;
  • The pressure of compressed air inside the expansion tank is 1.5 bar;
  • connecting size. 1 inch (25 mm);
  • UNIPUMP expansion tanks are 5, 8, 12, 19, 24, 36, 50, 80 and 100 liters. The equipment is installed in a vertical and horizontal position. Expressive tanks for a gas boiler or water heater with automation with a volume of up to 500 liters can be made to order.
Volume, ldiameter, mint, mm permission. Size working pressure, max
5 l vertical 152 305 one” 6 bar
8 l vertical 202 310 one” 6 bar
12 l vertical 260 290 one” 6 bar
19 l vertical 265 395 one” 6 bar
24 l vertical 265 435 one” 6 bar
35 l vertical 375 460 one” 6 bar
50 l horizontal 350 380 one” 6 bar
50 l vertical 375 560 one” 6 bar
80 l vertical 375 720 one” 6 bar
100 l horizontal 440 470 one” 6 bar
100 l vertical 440 730 one” 6 bar

With the generality of the main function, the design of expansion tanks for the heating system may vary. And the main difference lies in the features of the heating system itself, which can be open or closed type. The latter are similar to the accumulators.

DIY expansion tank

All types of work related to the installation, connection and commissioning of an expansion tank do not belong to particularly difficult and can be performed by home masters on their own.

over, for them this experience will be useful, because during the operation of the expander the expander will need to know how to adjust the pressure in it. In addition, the for such work are quite high.

In order to perform a hydro-accumulating capacity of a small heating object, a vessel of 10-12 liters is suitable, depending on the obtained calculated result in volume.

The expander can be made of sheet steel. Mark the steel sheet, having previously completed the card cutting out of paper. This method will help cut out parts with less metal losses. When connecting sheets, without fail, take into account the thickness of the circle of a grinder of a machine that can “eat” a couple of millimeters. All operations are performed scrupulously with further cleansing of the edges.

The vessel body consists of 5 or 6 rectangles, based on the need to make a lid. If necessary, you can divide the upper part of the cover into 2 parts in this way, weld one part to the base, and the second. on the veil.

Cut parts are set at 90 degrees and welded. Welding method: gas welding is well suited for 2 mm steel, and 4 mm must be connected with electric welding.

In the bottom of the case, a hole is made for the supply pipe of the heat carrier. Settings are installed in the design of the container for the recharge of the system and emergency drainage, higher than the maximum permissible level of filling the collection, in order to avoid water overflow.

After the welding work and strapping with heating pipes, the container is insulated so that the water does not freeze.

Through the lumen in the lid, water from the collection evaporates and air enters the heating system. This can lead to overheating of pipes and low circulation rate in the heating system.

In order to solve this problem, experts advise pouring a small amount of oil into the tank. The fat film will protect the coolant from air penetration.

Thus, summarizing the result, it can be emphasized that the expansion tank in the heating system of private houses is a compulsory protective device to stabilize pressure on the network during its launch from the cold state.

To ensure reliable protection, you will need to calculate the required volume of capacity, and make a choice of model by catalogs on the Internet or in the retail network.



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