The thermostatic three-way valve for the boiler, installed in an autonomous heating system, allows you to save fuel, increase the life of the equipment, protecting it from malfunctions. It plays the role of a regulator and a safety element. But it is impossible to install the first thermo mixer that comes into the system; you must choose a device that meets its characteristics and the requirements for it regarding functionality.
The device and principle of operation of the three-way valve for the boiler
The design device of a thermo-mixing valve for a solid fuel boiler or other may differ significantly depending on the purpose of the element and the manufacturer, but the principle of operation remains unchanged. The thermostat has three outputs: one of them is always open, while the others overlap completely or partially during operation. According to the number of outlets, the valve is called 3-way. It is used to mix or separate flows of liquid or gas, whereby the temperature of the coolant is regulated, switching from one circuit to another.
It looks like a tee. The internal device is represented by a locking mechanism and a rod that ensures its movement - these are the main elements. Some designs have two seat rings to secure the valve. Supplementation with other elements is possible.
Varieties of valves
The functionality of the valves is different. On this basis, three-way valves are divided into switching, mixing and separating.
Mixing
A cold stream is fed to one inlet, a hot stream to the other. At the outlet, they mix, forming one stream of a given temperature. Thus, thanks to the thermo mixer, the temperature of the coolant is regulated, in particular, the return flow is mixed into the coolant at the outlet of the boiler. For this, the valve is installed on the return pipe of the heating pipe.
Dividing
Isolation valves are also called control valves. They split one stream into two. They are used in the hot water supply system, piping of air heaters.
Switching
Changeover or changeover switches are used for switching from one circuit to another, for example from heating to hot water supply. Switching is carried out using an electric drive.
Three-way valve control methods
Three-way valves according to the control method are:
- autonomous;
- manual;
- thermostatic;
- with an electric drive.
If there is no control possibility, the thermal valve is of a self-contained type. It is preset by the manufacturer to a certain temperature of the heat carrier, i.e. the temperature in the system will always be constant. The main advantages of such devices are low cost and the ability to maintain the same temperature. But it is impossible to change the preset settings, so the characteristics of the valve must meet the requirements of the system, it will have to be selected more carefully.
The manually operated 3-way valve is equipped with a manual adjustment device such as a control panel, rotary knob or valve. Control of adjustment is carried out using special marks - a scale. Compared to a stand-alone regulator, the manual three-way thermal valve is more functional: it allows you to change the temperature mode depending on specific needs and will maintain the temperature at a given level. However, this valve "does not know how" by changing the temperature of the coolant to the transformation of the surrounding conditions.
The design of the product with a thermostat includes a thermostat. The gaseous or liquid medium inside it reacts to changes in the temperature of the coolant. When it heats up to the preset temperature, the hot water pipe is closed off. By the type of power supply, this type of valve can be mechanical and electronic. Mechanical ones work autonomously, while electronic ones require a power supply or periodic battery replacement. Although this inconvenience is fully offset by the benefits.
The inclusion of a thermostatic valve for a solid fuel boiler into the system allows you to automate the process of changing the temperature regime according to the time of day, days of the week. The cost of a three-way element with a thermostat is higher than the cost of simpler analogs.
The most advanced models are electrically actuated thermal valves. In order for their work to be constant, it is necessary to install an uninterruptible power supply unit. The flow of cold or hot heat carrier is regulated by a controller, which registers temperature deviations from the set values, and a servo drive. The outlets do not completely overlap, but the volume of the coolant changes. Thanks to the operation of the automation, the heating circuit is always evenly heated, and the temperature of the coolant always exactly matches the set one. The possibility of changing the mode is also present, but you need to be prepared for a high consumption of resources: coolant and electricity. You will have to pay more for the thermal valve itself. A fully automatic device is more expensive.
Purpose and functions
The three-way valve is installed for the following purposes:
- So that the cold coolant does not succumb to the boiler and condensate does not fall out on the inner walls of the furnace. In addition, if a cast iron heat exchanger is used in a hot water boiler, it may crack from temperature changes.
- To regulate the temperature of the coolant in the circuits. This need may be due to the complexity of the system, where the temperature requirements for each circuit are different. When connected to a heat accumulator, as well as when the heat carrier is used in the heat exchanger of the air handling unit, which is part of the air heating system.
- To be able to control the heating of the coolant in the underfloor heating circuit. The optimum temperature for underfloor heating is no more than 50 ° C. The temperature of the coolant coming from the boiler can exceed this figure by 10-35 ° C. The cooled water that has passed through the underfloor heating circuit will mix with the coolant from the boiler, a three-way valve installed on the distribution manifold will mix the return flow.
The regulator should not be installed if several heating sources operate in the system one by one; if the length of each loop of the water floor is no more than 50-60 m (then RTL heads are installed instead of a three-way valve); if the heating is organized according to a gravity system.
Basic parameters when choosing valves
The three-way valve should correspond to the features of the system as much as possible, therefore, when choosing, all parameters should be checked: design device, technical characteristics.
- First of all, it is necessary to cut off options that are made of unsuitable metal. Silumin low-cost three-way valves are eliminated immediately because the aluminum-silicon alloy is of low strength. Such thermal valves crack and literally crumble during operation.
- Cast iron 3-way valves do not corrode and are strong enough under static loads, but a point mechanical impact or a sharp temperature drop can cause it to break. Such devices cannot be repaired.
- Steel devices are inexpensive and durable at the same time, but they rust over time. In order to protect against corrosion, the products are coated with nickel and chromium.
- Thermal valves made of stainless steel are more expensive, the metal is not subject to oxidation and corrosion, so they will serve for a long time.
- Brass and bronze 3-way valves are preferred because the material best meets the requirements for durability and corrosion resistance. Brass products cannot be installed in a system where the coolant is heated to temperatures exceeding 200 degrees. Bronze devices are built into a heating circuit made of copper.
The internal locking mechanism in some products may be ceramic. If the operating conditions are observed, ceramics perform in the best possible way: they do not rust and serve for a long time. But the coolant in the system must be of high quality. In the presence of mechanical impurities, ceramic elements will quickly fail.
The type of valve is selected taking into account the features of the system:
- To protect the boiler from condensation, a valve with an internal thermostat set to a constant temperature of the heating medium is sufficient.
- If the system consists of several branches and it is necessary to control the heating of each, a regulator with a thermal head and a remote sensor is installed.
- For self-assembly of the system, a mixing valve is recommended for installation. It is easier for a beginner to understand the scheme of its work, how to put it, remove it.
- Saddle types, in contrast to rotary ones, more accurately allow you to regulate the temperature of the coolant and the pressure.
- For underfloor heating, electric models with a servo drive are recommended.
- For DHW - dividing valves, for heating - mixing valves.
As for the technical characteristics, it is necessary to take into account:
- connection method - it can be threaded and flanged;
- inner diameter of pipes - must match the diameter of the pipes at the installation site;
- maximum working pressure;
- the maximum temperature of the coolant at the installation site;
- average water consumption per hour - conditional throughput;
- dynamic range of regulation (30: 1, 50: 1, 100: 1) - indicates the difference in throughput when the valve is fully closed and half open.
Valves with a range of 100: 1 offer a wider range of adjustments.
The data is indicated in the passport for the product. In order to correctly select the valve according to the parameters of the system, it is also necessary to calculate the flow rate of the coolant in the installation line, because the valve must pass the required volume of water at different positions of the stem.
Last but not least, the parameter is manufacturer. Popular:
- Esbe (Sweden);
- Danfoss (Denmark);
- Honeywell (USA);
- Herz Armaturen (Austria);
- Caleffi (Italy);
- Icma (Italy);
- Valtec (Russia).
It is recommended to choose products of well-known brands, then you can be sure that the marking and the declared characteristics correspond to the real parameters of the three-way valve.
Simplified budget items
Three-way valves of a stand-alone type are considered to be simplified. Their internal structure is really simplified, since neither a thermal head with a controller nor a stem is provided in them. The thermostatic element is installed inside and designed for a specific temperature (often 50 ° C or 60 ° C). It will not be possible to change the settings, the flow temperature at the outlet from the valve will always correspond to the set ± 2 ° С. This option is for those who install the valve in simple heating systems and want to save money. The cost of simplified elements is about 30% lower than the average cost of the bulk of regulators.
The thermostatic three-way valve is necessary in complex systems that include several circuits: hot water supply, heating, underfloor heating. It allows you to save fuel by using the heat energy generated by the boiler more efficiently. Despite the many advantages, the installation of the valve is not always justified, therefore, you should consult with a specialist regarding the advisability of installing it.
