The heating system of private houses, in addition to the boiler itself and the heating circuit, includes several auxiliary elements.
They include the expansion tank.
This important element of the system is a necessary device that increases reliability.
What is the function of expansion tank for heating system?
The purpose of the device lies in its name.
The heating circuit and the boiler are designed for a certain pressure. But the heated coolant increases in volume, therefore it exerts more pressure. It’s in the end can lead to leaks at weak points.
The pressure increase must be compensated by the elementwhich accumulates in itself part of the liquid.
This is a common function, characteristic of all types of this device.
Types of expansion tanks
Depending on the type of heating system used tanks, they are divided into 2 types.
Such a tank used for outdoor heating
without forced circulation. He is container without top. At the bottom of the tank there is a hole, a heating pipeline is connected to it with a thread.
In some houses, you can still find a container, it copes with its function, while being quite outdated and has a number of disadvantages:
- the need to place the tank at a height;
- evaporation of liquid from the container;
- acceleration of corrosion processes in different parts of the heating system due to the contact of the coolant with air;
- large tank sizes.
In connection with these disadvantages, closed expansion tanks are now becoming more and more popular.
Closed type or membrane
These tanks are used for heating systems with forced circulation. Capacity compensates for the pressure surge not only when the coolant is heated, but also when the circulation pump is turned on.
It is also called membrane tank due to the nature of the internal structure. it a spherical or flat reservoir, which is divided into two cavities inside by a rubber membrane:
- one is filled with coolant through a threaded pipe;
- the other — with an inert gas or air.
The second container has a nipple that regulates gas pressure. The compartments are not connected to each other.
The principle of operation of a closed tank is simple:
- excess hot coolant enters one of the chambers, the volume of which increases;
- the pressure in the gas compartment rises, which makes it possible to compensate for the voltage in the heating system.
When the coolant cools, the process in the tank goes in the opposite direction.
There are 2 types of closed-type containers, depending on the membrane:
- In some the membrane is made in the form of a diaphragm that cannot be changed. These containers are cheaper.
- In the second type of closed devices the membrane is removable and looks like a pear.
The choice depends on the capabilities of the buyer. It should be noted that damage to this rubber element is quite rare.
Before buying a tank, you need to decide on its volume.
You can calculate the volume of the tank yourself using several online calculators, or by a fairly simple formula:
Vtank=(Vsystems *k)/(1‑Pmin /RMax)where
Vtank — tank volume;
Vsyst — the total volume of the heating system, including all radiators, underfloor heating, boiler, etc.;
k — coefficient of expansion of the liquid, for water its values depending on heating from 10about up to the maximum temperature of the coolant are indicated in the table below;
Pmin is the initial pressure in the vessel;
PMax — the maximum possible pressure in the tank, which is calculated according to the settings of the safety valve, taking into account the difference in the heights of the location of the tank tie-in and the valve.
Table. The coefficient of expansion of water depending on the heating at an initial temperature of 10aboutFROM.
|Temperature from 10
|k value, %
|Up to 40
|Up to 50
|Up to 60
|Up to 70
|Up to 80
|Up to 90
|Up to 100
|Up to 110
Since the quality of the entire heating system depends on the correct calculations, you should not spare money and contact a special organization that will take into account all the parameters, which will allow you to purchase the most suitable tank.
Here you can also get advice on the selection and installation of the tank.
Useful tips when choosing
When buying and installing an expander, it is worth considering several nuances.
- When choosing a place for mounting the tank, it must be taken into account that it can not be installed immediately after the circulation pump.
- Commercially available tanks come in two colors: red and blue. In the first, the membrane is stronger, but made of technical rubber. Blue tanks are used for water supply, they contain food-grade rubber, but it is less strong and durable..
- When installing, use special sealant.
- If you decide to stay at open systemthen the tank must be placed at the highest point, and when installing the pipeline, observe the recommended slope.
- The size of the tank should not be less than the calculated value, a slightly larger volume is allowed. When using forced circulation, the capacity cannot be less than 15 liters.
- Antifreeze can act as a coolant. For glycol mixture, it is better to choose an expansion tank, the volume of which is twice the calculated one.
The main advice is to contact the professionals, because the installation of the tank only seems simple. In addition, you can not do without a special tool.
If you are confident in the calculations and your own strengths, the tank and all materials are purchased, then you can install the container yourself.
Of the tools you will need:
- Stepped and adjustable wrenches;
- soldering device for plastic pipes;
- Key for the installation of plastic pipes;
- In some cases, you need welding machine and angle grinder.
Before installation, it is necessary to de-energize the boiler, close the valves and drain the coolant if it is already in the pipes.
Installation is carried out subject to certain rules.
- The tank must be mounted and installed so that it can be accessed easy access for adjustment and maintenance.
- The temperature in the room should not be below 0.
- On the supply pipe you need to install a pre-shut-off valve that will allow you to remove the expander for maintenance and repair.
After installing the tank, you need to start the entire heating system. If boiling is detected in it, then the reason lies in the incorrectly selected diameter of the pipes. It’s not about the tank.
The installation of the expansion tank is described in the following video:
Prices for tanks for the heating system
The cost is determined by its type and volume. Small closed containers (18–24 liters) cost about 1000–12$.
An expander with a volume of 100 liters can be purchased for 4–60 $. Between manufacturers in their majority, the price difference is small.
Installation by a professional will cost you about 20 dollars.
When contacting trusted companies or with self-assembly, subject to all the rules, you will protect the heating of your home from damage. Therefore, the installation of a container is necessary, and it is worth choosing closed containers.