Each water heating system is characterized by a specific capacity. Therefore, when creating it, it is important to remember that with increasing temperature, the fluid expands, and, accordingly, the hydraulic pressure inside any confined space increases significantly. In order to avoid its excessive increase and to prevent possible accidents, an expansion tank for heating is installed in each system. It can be both open and closed type.
Capacity purpose
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, you cannot do without a special container into which excess fluid 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 indicated tank, its necessary volume in the system is restored. In addition, the tank is also designed to collect air formed during the heating of water.
Types of tanks
Specialists distinguish two types of expansion tanks: open and closed. It is immediately worth noting that the first option is now considered obsolete, but it is still still used in many houses. An open expansion tank for heating is a tank attached with its bottom to the 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 it is placed in most cases in the attics of houses. At the same time, its walls are covered with insulating material in order to prevent the loss of thermal energy. The use of open tanks leads to oxidation of the liquid with oxygen, which causes corrosion of pipes and radiators from the inside. A cover on an open expansion tank is not needed, 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 lack of contact between the liquid and the surrounding air. Due to this, the water does not evaporate. Moreover, when using a closed type of container, there is no risk that the liquid level rises so much that it can pour out of the tank and spoil the finish of the walls and floor tiles.
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 may be filled with ordinary air, a nitrogen-containing mixture, or other rarer filler. Membrane tanks are of the following types:
- made of heat-resistant natural butyl rubber, they provide the best temperature resistance;
- from ethylene-propylene rubber, are the most modern option, are used in both heating and water supply systems;
- from durable heat-resistant rubber, the cheapest type that is often found in products from China.
Also, the expansion tank for heating can be equipped with an irreplaceable, replaceable or pear-shaped membrane. The first option is equipped with a special clamp ring, which ensures the long-term use of this equipment, allowing you to maintain a constant required pressure. At the same time, the diaphragm does not stretch, but rolls along the walls of the tank, increasing the reliability of the structure.
A replaceable membrane is best used in large systems where a large filling volume is possible. In such tanks, it is located on both sides between the flanges and remains stationary when the container is filled with liquid.
The pear-shaped replaceable membrane is attached only to the upper flange. If an excessive amount of liquid gets in, it rests on the walls of the tank, evenly distributing the load.
Tank selection rules
Before purchasing a tank, it is important to find out the total system capacity. 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 large number of indicators, including not only the amount of liquid, but also the operating temperature, static and maximum pressure in the system.
Having found out the required volume of the tank, you can proceed with its selection 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 the heating system or decide that you need to replace the expansion tank, then you should find out about some features of its installation. So, a closed container can be located anywhere, but the most functional area for it is the return. The best place would be the area between the circulation pump and the boiler itself.
The tank is connected to the system using a pipe that is equipped with a ball valve. In order for the membrane to absorb excess fluids without problems, the pressure in the container must be at least 0.2 atmospheres lower than in the system itself. You should also be aware that the discharge of factory gas, whether it be air or
liquid nitrogen, is prohibited.
Cost of equipment
When choosing tanks, many do not look at the principle by which they work, not at their volume, but at the cost. But you should not save on this equipment, 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, but it is better to spend money once and never find out what is fraught with the wrong selection of capacity. The cost will depend on the volume, on the type of membrane installed. It can range from one to ten to twelve thousand rubles.