Expansion valve: the working principle, structure and characteristics


2020-03-27 20:00:17




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One of the primary uses of thermostatic expansion valve is adjusting the temperature in a residential building or room. For correct use this unit must be installed on the heating radiator in the room in which it is important to maintain the desired temperature.

Device Selection

Selecting this device, it is important to consider these three parameters as:

  • View of the device;
  • Technical parameters of the valve;
  • The cost of the product and manufacturer.

expansion valve

If to speak in more detail about each of these selection criteria, it is always worth starting with a definition of the device. On this basis, products can also be divided into several groups:

  • The first group includes those devices which differ in the method of their mounting on the pipe. Among these types are: direct expansion valve, which is installed on pipe running parallel to the ground. Angle valve is designed for installation on the tubes, which appear out of the floor, the axial products are installed on the hose coming out of the wall.
  • The second group includes devices which differ on such basis as the type of heating system. Thermostatic valves for one-pipe systems are characterized by greater bandwidth than the valves for two-pipe.

expansion valve air conditioning


It is Important to say that the valves are divided into several groups not only by those systems with which they work. Different groups of these products differ such a thing as thermocouple and the working fluid. If we talk about the content, the device can run on gas, liquid or wax. Gas types considered to be most superior, the fluid occupies the middle niche, and the worst in its characteristics of steel thermocouples working with paraffin.

expansion valve price

Also there are minor differences and the method of adjustment of the fuser. Just distinguish between two categories of the adjustment element. The first category refers to those devices that are setup on the shared medium settings experts in manufacturing. Call it pre-configured item. Expansion valve open adjustment is the second category, a feature of which is that an alignment of the fuser, each user can own.

Operational characteristics

After the selection process was defined the device, you can proceed to the selection of its technical parameters. Expansion valve shall provide the following parameters:


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  • Maximum working temperature should reach 200 degrees Celsius.
  • The Pressure at which the device must withstand, from 16 to 40 bar.
  • It is Important that the valve was completely made of such materials that are not amenable to mechanical or corrosive impact. The best of these qualities are considered to be parts of bronze, brass or steel.
  • Diameter of a pipe of heating in the house and the diameter of the valve must be the same.
  • The Last key characteristic for the valve is the possibility of its installation on the desired system. For example, if the installation of the controller is carried out via a thread, the settings on the valve and the pipe must match.

valve thermostatic straight

Manufacturers and cost

It is Logical that the cost of the product is formed not only of those characteristics which were listed above. This parameter also varies depending on what the manufacturer has released one or the other valve. Currently, there are a few companies whose products are considered the best on the market:

  • The First representative is the German company Oventrop. The main advantage of their products is, of course, high quality. Price thermostatic valve from this manufacturer starting from 1 000 rubles.
  • The Second famous manufacturer is Danfoss. The company is Danish, and the cost of their product starts from 1 500 rubles. A distinctive feature of their products is that they use the latest technologies for production, which allows to increase the service life of the valve.
  • The Last of the three well-known representatives of the Italian company Luxor, which stands out against the rest of their prices - from 250 rubles, and is characterized by the fact that the products from the manufacturer are quite reliable.

expansion valve danfoss

Installation instructions

To Carry out installation of this product best adhering to the following guidelines:

  • The Most appropriate place of installation of the valve is input in the heating radiator.
  • It is Important to know that there is such parameter, as the optimal height of installation of the device. It is in the area of 40 to 60 cm from the floor. Most often, the valves are calibrated initially under a height. If you follow this rule fails, then the device will need to be reconfigured.
  • To ensure the normal operation of the sensor, it is necessary to observeanother recommendation - the head of the valve after installation shall have a horizontal position. If you place the device so that the head will be in a vertical position, the warm air coming through the pipes will interfere with the normal operation of the valve.
  • One of the rules is the arrangement of the bypass in that case, if the valve is mounted in a one-pipe system. The bypass is a pipe through which to circulate liquid, if, for any reason, its movement in the radiator will be difficult.

thermostatic radiator valve

Connection valve

Connect thermostatic radiator valve may, following this scheme:

  • The First thing you need to do is to drain the fluid from the heating system. To do this in a private home is easy, but in an apartment will have to contact the service company, as the valve for draining is located in the basement of the house.
  • Next is the process of tapping into the pipe in a pre-selected location.
  • At the ends of each of the tubes have cut threads of the required parameters.
  • If the valve threads are initially processed sealed with thread, then using a wrench you can hold the mounting device in the prepared place.
  • It is Important to note that each valve includes determining the direction of the arrows, which indicate the motion of the fluid. When installing the reverse side should the operation of the apparatus will not be provided.
  • After the components are installed it is important to check the tightness of the system.
  • The Last step is to configure the thermocouple system.

expansion valve working principle

It is Worth noting that if you have the necessary knowledge and skills to carry out the installation on their own.

Features of Danfoss products, Eagle

Expansion valve Danfoss has its own constructive and other features from other valves. In terms of design, this device includes a thermostat which is separated from the valve membrane. Besides, one of the important elements of these valves is a spring. She is in the process of regulation of overheating.

If to speak about products of the company Eagle, you can select the next controller. Thermostatic radiator valve Eagle 302-1608. Has an internal and external thread. Is characterized by such pressure as 1.6 MPa or 16 kgf/cm2. This type of controller is direct.

All products are manufacturer Danfoss is divided into several categories:

  • TE5-TE55. These devices are intended to control admission of liquid refrigerant to the evaporation devices installed in the refrigeration units.
  • TGE. This group of products is distinguished by the fact that the design of valve assemblies of the device is indispensable, and they are made specifically for the air conditioner. Expansion valve this category is intended for commercial air conditioning systems, which are characterized by high capacity.

The advantages of "Danfoss"

Individual marks deserve AKV thermostatic devices from this manufacturer. The most active use they found among refrigeration units that are placed in shopping malls. Among the major advantages of this product are the following:

  • View this collapsible design that provides the ability, when the need arises, as a replacement orifice, easy to deal with this task.
  • One of the main advantages is no need for constant adjustment of the regulator when it is operating.
  • This device at one time is not only expansion valve, but a solenoid.

Regulators AKV also differ in that they possess a functional drive. The principle of operation of the valve based on pulse width control parameters.

Working Principle

Setting the TRV is better to adjust the supply of refrigerant to the evaporator. The principle of operation of thermostatic expansion valve based on the adjustment of the flow of the refrigerant so that at the outlet of the evaporator almost all the time there is overheating. In those moments, when overheating of the evaporator increases due to the thermal load, the controller increases the flow of refrigerant as long as the superheat value falls below the setpoint. This method of adjustment allows the device to maintain the fill level of the vaporizer to a volume that is limited to the pressure setpoint.

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