How to choose an expansion tank for heating system

Each heating system includes a number of elements, without which it is impossible for its normal functioning. One of these elements is an expansion capacity, its assignment and the device will be told in this article. We also consider how to choose an expansion tank for the heating of a private house.

Why do you need an expansion tank?

From the school year of physics, everyone is well known that any body is expanding when heated, and the liquid and gas increase in volume. Unlike the gas, the liquid - the medium is incompressible and if it is heated in a closed vessel, which is the tank for the boiler, it will lead to an increase in pressure inside it, since it has nowhere to expand. As a result, the reservoir walls can happen.

Imagine a coolant heated in pipelines from a temperature of 20 ºС to 80 ºС. If you do not put an expansion tank in the heating system, then when heating the liquid medium, the pressure in the network will increase and water can break through the fortune in the lowest place. Well, when there is a safety valve. Through it and the excess water will go, because there is nowhere to go to her. In the absence of a valve, the coolant simply breaks out on some of the compounds.

The expansion tank is needed to place the growing coolant when it is heated. At the same time, during cooling, it returns back to the system.

In the case when the water resets the safety valve, then after cooling, it cannot return it back and starts the air on the released place. This will lead to the formation of an air traffic jam, and it will not give the system to work normally.

Types of expansion Bachkov

Externally, expansion tanks for heating may differ in the form and size determined by the calculation. This is usually a reservoir connected to the heating system by means of one pipe. However, different types of containers have constructive differences, and they are used in different cases. To choose the right tank, you need to understand these differences, so first introduce the list of existing species:

• open type;
• closed, equipped with membrane.

Note. There are still closed expansion vessels without a membrane, but it is not categorically recommended to apply them. Below we will explain why.

Open tanks

These tanks are used for an open heating system (otherwise - gravitational, samotane) and are a metal reservoir with an open top of an arbitrary shape. To the top of the side wall, the nozzle for connecting the hose or pouring pipe is welded, the coolant to the Baku is suspected from below. The element is installed above the entire system on the feed pipe, as a rule, in the attic of the house.

Note. Speaking with the right technical language, the open system is the one from which water is directly selected for the needs of DHW. In private houses, it is not used, only in centralized networks. The open erroneously call the scheme with the natural circulation of the coolant.

Any expansion tank for open-type heating performs 2 functions:

• serves to compensate for the extension of the coolant;
• remove air from the system, since its top is reported to the atmosphere.

This is its advantage, but it is not the only one. Open container can also be successfully serviced in systems with forced circulation, since the tank device is very simple, there is nothing to break. However, it has a lot of flaws:

• the tank installed in the attic requires good insulation;
• during the season, it is necessary to constantly observe the water level in the tank and to replenish it in a timely manner;
• the coolant is constantly saturated with oxygen from the atmosphere, which is why the metal parts of the boiler are faster;
• additional consumption of materials and complexity during installation.

Closed membrane tank

A more modern closed expansion tank is a cylindrical vessel with a built-in rubber membrane. Used in circuits with forced circulation of the coolant and is installed in the indoor room. The production of the coolant is also carried out from below, a service spool is installed on top of the air for air injection.

Rubber membrane (in commoner - "pear"), which is equipped with a closed expansion tank of the heating system, there are 2 types:

• in the form of a diaphragm;
• balloon type.

Note. The capacitances of some manufacturers have a removable "pear", which makes it possible to change it when cracking.

The form of the membrane of a special influence on the work of the device does not have, although a little more water is placed in a tag of a second type. On the other hand, the air (sometimes - nitrogen) is injected from the "pear) under certain pressure, it must be configured for each system individually. All closed expansion tanks act equally simply: when the heat carrier is heated, the pressure in the network grows, the membrane is stretched and starts water inside the tank. When cooled, everything flows in the reverse order.

The hermetic expansion tank for the wall-mounted gas gas boiler is often built into the inside of the heat generator, as it has small dimensions. In addition, the device is not reported to the atmosphere and diffusion of oxygen into the coolant completely excluded. The weak point of such tanks - the membrane, its service life very rarely reaches up to 10 years, and it is not always possible to replace it.

There is also a third type of compensation devices - a vacuum expansion tank for heating a closed type without a "pear". It's hard to sell them, and it makes no sense, since such a design is the most unsuccessful. The role of the membrane in the container plays itself air, which leads to its active diffusion into the water, and this is unacceptable. And then, the level in the tank will be increased all the time, as a result, it will immediately be compensated for expansion.

If the house is planned or already mounted a scheme with natural circulation, the expansion tank of an open type is just for you. You should not wise with a vacuum tank here, remember that water in such a system moves only due to the difference in specific weight and the device may not play their role. An open vessel can be bought, but you can make it yourself, most importantly, it is correct to calculate the volume of the expansion tank, which we will negone below.

With vacuum membrane vessels, the situation is more complicated. There is one caution: Once in the store among many similar products, do not confuse the heating tank with the water supply hydroaccumulator. Externally, they are very similar, even the color may be the same, so that the tank selection on this feature is excluded. The label tanks differ in the signboard, the operating temperature is indicated to 120 ºС and pressure up to 3 bar. On the hydroaccumulator, respectively, up to 70 ºС and pressure up to 10 bar.

By choosing, it is also worth paying attention to the possibility of replacing the "pears" in case of its failure. The size of the apparatus is selected according to the calculation of the closed tank.

Calculation of expansion tank

In the technical literature and on the Internet, there are many techniques for which the expansion tank is calculated for the heating system with natural and coercive coolant circulation. But for the most part, they contain a mass of complex formulas with binding to boiler power and other parameters. You are not mistaken if we use a simpler way to determine the volume of the tank.

The method is based on the statement that the amount of water in the system with maximum heating will increase no more than 5%. That is, first calculate the volume of water as follows:

• the number of heat carrier in the boiler tank - on the passport;
• the volume of water in pipelines - by the formula of the area of \u200b\u200bthe circle, find the cross-sectional area of \u200b\u200beach pipe and multiplies it for a length;
• capacity of radiators - also on the passport on the product.

Having summed up the results, select and calculate the expansion tank with a reserve, taking not 5, and 10% of the resulting amount. This will be its capacity.

Conclusion

Calculate the volume and choose a closed type tank is simple enough, it will only remain correctly installed. This can also be performed independently, guided by the instructions attached to the product.