Each water heating system is characterized by a certain capacity. Therefore, when creating it, it is important to remember that as the temperature rises, the liquid expands, and, accordingly, the hydraulic pressure inside any enclosed space increases significantly. To avoid its excessive increase and prevent possible accidents, an expansion tank for heating is installed in each system. It can be either open or closed type.
Purpose of capacity
To understand all the functions that the tank performs, you need to know that the water circulating in the heating system cannot be compressed. When heated, its actual density decreases, which leads to an increase in the occupied volume. Therefore, it is impossible to do without a special container into which excess liquid will go. And the expansion tank of the heating system performs several functions at once. It accepts the excess volume of water released during the heating process, allowing you to maintain a constant hydraulic pressure. With a decrease in temperature or a slight leakage of liquid from the specified container, the required volume in the system is restored. In addition, the tank is also designed to collect air generated during the heating of water.
Types of containers
Specialists distinguish between two types of expansion tanks: open and closed. It should be noted right away that the first option is now considered obsolete, but it is still used in many homes. An open expansion tank for heating is a container connected with its bottom to a pipe. The hotter the water in the system, the higher the level rises. Such a tank is installed, as a rule, above the upper part of the heating system, and in most cases it is located in the attics of houses. At the same time, its walls are covered with insulating material in order to prevent loss of thermal energy. The use of open tanks leads to the oxidation of the liquid with oxygen, which causes corrosion from the inside of pipes and radiators. A cap is not needed on the open-type expansion tank, but it can be installed to protect it from debris.
The closed type of containers is considered more modern. Such tanks are a sealed capsule, they can be made in the form of an oval or a ball. Their main advantage is the absence of contact between the liquid and the surrounding air. As a result, water does not evaporate. Moreover, when using a closed type of container, there is no risk that the liquid level will rise so much that it can spill out of the tank andspoil the decoration of the walls and the ceiling of the room.
Classification of closed containers
When choosing expansion tanks, it is important to remember that they differ depending on the gas filler, on the composition of the membrane and the principle of its location. The purchased container can be filled with ordinary air, a nitrogen-containing mixture or other rarer filler. Tank membranes are of the following types:
- made of natural heat-resistant butyl rubber, they provide the best temperature resistance;
- made of ethylene propylene rubber, are the most modern option, used in both heating and water supply systems;
- made of durable heat-resistant rubber, the cheapest type, which is often found in products from China.
Also, the expansion tank for heating can be equipped with a non-replaceable, replaceable or pear-shaped membrane. The first option is supplied with a special clamping ring, which ensures the long-term use of this equipment, allowing you to maintain a constant required pressure. In this case, the diaphragm does not stretch, but rolls along the walls of the tank, increasing the reliability of the structure.
Replaceable diaphragm is best used in large systems where high fill volume is possible. In such tanks, it is located on both sides between the flanges and remains motionless when filling the container with liquid.
The pear-shaped replaceable diaphragm is only attached to the top flange. When ingested in excessliquid, it rests on the walls of the tank, evenly distributing the load.
Rules for choosing a tank
Before purchasing capacity, it is important to find out the total capacity of the system. The expansion tank for heating must contain at least 10% of the coolant. In this case, it is worth considering the volume of radiators, pipes and the boiler itself. When choosing the best option, specialists take into account a larger number of indicators, including not only the amount of liquid, but also the operating temperature, static and maximum pressure in the system.
Once you figure out the required volume of the tank, you can start choosing it and pay attention to other indicators, such as gas filler, membrane material and its location.
Installation or replacement
If you are just starting to install a heating system or decide that you need to replace the expansion tank, then you should learn about some of the features of its installation. So, a closed container can be placed anywhere, but the return line is the most functional area for it. The best place is the area between the circulation pump and the boiler itself.
The container is connected to the system using a pipe, which is equipped with a ball valve. In order for the membrane to accept excess fluid without problems, the pressure in the tank must be at least 0.2 atmospheres lower than in the system itself. You should also be aware that venting factory gas, whether air or liquid nitrogen, is prohibited.
Equipment cost
When choosing tanks, many people look not at the principle on which they work, not at their volume, but at the cost. But saving on this equipment is not worth it, because the safety and reliability of the heat supply system will also depend on which expansion tank is installed. The price of the desired option, of course, may seem overpriced to you, but it’s better to spend money once and never know what the wrong choice of capacity is fraught with. The cost will depend on the volume, on the type of membrane installed. It can range from one to ten or twelve thousand rubles.
