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Three-way thermostatic valve for floor heating

The main function assigned to the three-way valve

The system of heating “water underfloor heating” is fundamentally different from the traditionally used by us, radiator heating. The thing is that for the heating circuits lying on the floor in the body of the concrete screed, a low temperature of the coolant is required. Underfloor heating is considered a low-temperature system, which is connected to the heating devices or hot water source through a mixing unit.

For heating to comply with hygiene regulations, the temperature of the water in the water circuits must be significantly reduced. It is this function that is entrusted to the mixing unit, or as it is called among professionals, the mixing unit. Stand-alone boiler in operating mode heats the water to a mark of 95 0 C. Only slightly cooler than water in the central heating system. For the normal operation of underfloor heating the optimal temperature of the heat carrier is 35-55 0 C, which is obtained at the outlet of the mixing set.

Note: do not confuse the mixing unit with the manifold. The first is a set of various assemblies and devices that provide regulation of water in the water circuit, while the second is just an integral part of the entire regulating unit.

three-way, thermostatic, valve, floor, heating

Mixing unit is a set of devices and appliances that perform their specific functions. If information about the manifold is more or less enough, but what is the three-way valve, few of us have a clue. The task of this device is to mix two different temperature streams of liquid. The cooled water coming from the return pipe and the hot water coming from the heating source are combined by this mechanism into a single flow of the required temperature. The main part of this device is a temperature-sensitive core, an element that reacts to changes in the temperature of the aqueous medium by shrinking or expanding.

It is at the expense of this design, implemented the work of the three-way valve, aimed at the automated regulation of the coolant temperature in the system.

On a note: this device is used not only in the work of water underfloor heating, but also stands on the equipment of almost all autonomous heating systems, working on the liquid coolant.

The illustration shows a diagram of the mixing unit for underfloor heating and the place occupied by the three-way valve.

Schematic diagram of the mixing unit for underfloor heating and location of three-way valve in it.

Thermostatic valve

The main difference between thermostatic valve for underfloor heating is the regulation of the intensity of hot water flow only. In this case, together with the valve sold thermal head with remote temperature sensor.

On sale you can find varieties of three-way valves that can not regulate the temperature of the coolant itself. In essence, these are standard valves that can be opened or closed to adjust the water temperature manually. Despite the simplicity of design, they are quite often used in underfloor heating systems.

Features of automatic devices

To ensure the effective work of the thermal mixing valve, the process of formation of mixed fluid flow must be continuously monitored. Better if it is done in automatic mode.

Devices with automatic control are regulated by electric or pneumatic nodes.

  • Electric actuators are relatively inexpensive and easy to connect. This largely explains their popularity and widespread use. On the other hand, dependence on electricity supply and the need for periodic maintenance make them insufficiently reliable.
  • Pneumatic actuators are more expensive, and the procedure for their connection is more complicated. However, these disadvantages are compensated by long service life and complete autonomy.

The task performed by the three-way valve underfloor heating mixes the cool return water with the hot water coming from the heating boiler. Externally, the principle of operation of all devices on the market is the same:

  • the boiler is connected to one of the inputs of the product;
  • The return is connected to the other;
  • Three-way mixing valve for floor heating connects to the manifold manifold.

Determine where certain points of the heating system are connected, you can use the diagram directly on the body of the mixing unit.

Important! On the market there are valves with two main methods of inclusion in the circulation structure. The first is called the T-form, with the outlet pointing downward and hot water and return flow on either side. The second type of connection is L-shaped, in this case the boiler is connected to the side, the return is from the bottom, and the output from the third point is on the side of the unit. When purchasing a product, make sure it fits comfortably into the piping network.

Selection criteria

Choosing a mixing valve, it is advisable to focus on several indicators.

  • The size of the room. For small rooms. bathroom, toilet is not always recommended to buy a more expensive thermal mixing valve, as it is enough to put the usual valve. Large rooms in the arrangement of warm water floors will require the presence of mixers, automatically regulating the temperature of the heating fluid.
  • Cross-sectional dimensions. This indicator is necessarily taken into account when selecting a thermostatic valve, ensuring accurate connection to the heating system. If you can not find a device with the desired diameter in the range offered in the store, special adapters can be purchased.
  • The possibility of obtaining an automatic mode of operation.
  • Flow capacity. This parameter is calculated during the design phase of the floor heating. According to the values obtained, a mixing valve that can withstand the required load is selected.

Smaller heating areas

If you decide to install underfloor heating in a small area, there is no need to install complete mixing equipment. Alternative method of mixing can be chosen.

Purchased special simple equipment for underfloor heating, consisting of a thermostatic valve with thermostat and two shutoff valves. The device is closed with a special box. The principle of operation is as follows:

  • A special hand wheel, located at the bottom of the valve, controls the temperature counter. It regulates the optimum temperature of the substrate.
  • A jump in a given temperature threshold serves as a command for the sensor. It closes the valve.
  • The valve design includes a sensor. It is able to track any temperature fluctuations in the atmosphere. Exceeding the threshold of the set temperature allows the sensor to close the valve.

This is how the product will work when the heating area is small.

What is a mixing thermostatic valve

The process of operation of the floor heating is to supply hot water from the heater or other heating source to the mixing unit. The first device with which the hot water comes into contact is a safety thermostatic mixing valve. A 2-way or 3-way valve is used to reduce the temperature of the boiler water before it enters the manifold. The heating medium is cooled automatically by the mixing of the cold water from the return flow pipe. This process occurs continuously and continuously for as long as the heating is on.

It has already been mentioned that for this purpose two types of mixing valves are used.

Two way thermostatic mixing valve

Two way thermostatic valve, in ordinary words, is an improved version of a manual valve.

three-way, thermostatic, valve, floor, heating

Simple and straightforward design of the valve allows the temperature control of the heat carrier in automatic mode quite effectively. Usually such a device is put in the heating system, replacing manual taps. The main advantages of the two-way type of device can safely include:

Note: The disadvantage of such a device are limitations of use. This type of valves is designed for the operation of warm floors of a small area. Two-way thermostatic mixing valve is usually installed on small water heating circuits (bathroom, nursery).

This type of mixing device is used most often when it comes to the equipment of underfloor heating as an auxiliary heating system. With the help of this device correct regulation of temperature of the heat carrier, working pressure in system and intensity of water streams is carried out.

The device consists of a one-piece, cast housing (brass or bronze). The valve has a thermostatic control head with a metric scale. The head position can be changed manually and automatically. For simple and inexpensive heating systems, equipment with manual adjustment is usually used. In complex systems, it is customary to install thermostatic valves with remote temperature sensors. The main part of the design of the device. the seats, one or two. Double seat valves are capable of shutting off the entire water flow, unlike three-way devices.

The principle of operation of the device is as follows:

  • The water coming from the return circuit, is sent back to the loop of the floor heating;
  • If the waste water temperature drops below the set temperature, the device will trip. Hot water is started in the system, mixing inside the device with the cooled water;
  • when the water temperature reaches the set parameters, the thermostatic sensor is triggered, the valve automatically cuts off the supply of hot water into the system.

In other words, the plug, consisting of a seat and plunger, reacts to the mechanical action of the thermostatic head. The plunger, lowering down, closes the flow of water, reducing the pressure. Downward-flowing shutoff means complete sealing of the valve’s passageways, so no water flows into the system. The plunger is installed perpendicular to the direction of water flow and can be needle, disc or rod.

Note: if you use this type of equipment when heating large areas, the thermostat will not work properly. Water in long loops cools faster, so the valve thermostat will be triggered more often, adding hot water to the system.

In practice, three types of valves are used today:

The illustration shows the connection diagram of a two-way mixing valve in an underfloor heating system.

Three-way mixing valve

As for the three-way mixing valve, its operation is in principle different from the two-way device. Here we are talking about mixing to the hot water coming from the boiler to the collector, the cool water coming from the return. Pros and cons of this device are similar to the two-way faucet, except for one detail:

When the device is in operation, the intensity of the coolant flow does not change in any way. Due to this, an even change in the temperature of the water flowing into the water loop loops is achieved.

The main features of this device should include the most convenient adjustment of the temperature mode of water floor heating. This type of mixing device is designed to work with large-scale heating systems (rooms over 250 m 2 ). However, despite the obvious advantages, the three-way valve has a number of disadvantages.

Important! When the thermostat is triggered, the valve opens fully, giving access to the underfloor heating system hot coolant. This can cause overheating of the heating circuit in the best case, and in the worst case, the rupture of the pipe.

In contrast to the two-way type, the three-way subflow device has a low flow capacity.

The product is made of brass or bronze. Equipped with a thermostatic head or a thermostat. The pattern of operation of this device is as follows:

Hot water flows through the right and front connections until the water temperature corresponds to the set parameters. When the fluid temperature decreases or increases, the thermostat starts operating, driving the piston rod. The movement of the piston rod causes the hot or cold liquid from the other lines to be drawn in. The front opening opens fully when the water temperature has reached the desired temperature again.

Depending on the actuator, three-way valves can be of the following design:

Each model has its own differences and features specifically designed for use in different hydraulic communication systems.

Connect the three-way valve as follows.

MixCal 3-way Thermostatic Mixing Valves


If the area of the room is less than 10 m2, you can adjust the temperature with simple valves. You need only two devices. on the supply and return. If you need to increase the temperature, just unscrew the valve more, and vice versa, screwing the valve can reduce the temperature of the coolant. However, unlike a thermostatic three-way mixing valve for underfloor heating, the valve must be closed manually. And the exact data is rather difficult to obtain. everything is determined only by experiment.

The thermostatic valve can be bought not only three-way, but also two-way. Such device is installed in addition to the usual valve on one side. In this case, there will be no need for manual control. it will be done automatically.

In cases where you need to cover a large area with underfloor heating, you need a sub-assemblies. It is a set of thermostatic valve, circulation pump, manifold supply and return flow.

How to choose a valve for underfloor heating?

The popularity of water floors, which are increasingly used for heating private houses and country cottages, gave impetus to the appearance on the market a huge selection of models. But here comes the question of what kind of three-way valve to install on the warm floor, which manufacturer to prefer. Because the abundance of products makes the purchase difficult. When selecting a device experts recommend that you decide in advance what type of device is needed. two-way or three-way. Then choose a manufacturer:

  • Valtec. The company represents in the market of the goods of russian-Italian manufacture. Their main advantage. the budget price and excellent physical and technical qualities. The manufacturer gives a 7-year warranty on the purchased three-way valve for underfloor heating with a thermostat. The products come with quality certificates, technical data sheet, installation recommendation list and warranty card.
  • Esbe. The Swedish company offers a high-quality taps for underfloor heating made of innovative materials. The devices are as resistant to operating conditions as possible, reliable and visually appealing. When buying Swedish products, it is recommended to pay attention to the technical characteristics of the equipment. There is a small possibility of parameter mismatch. Valves are delivered with certificates and warranty certificates, service life is more than 5 years.
  • Honeywell. High technology and excellent design distinguishes thermostatic mixing valve for underfloor heating of the American company Honeywell. The main advantages of its products. practicality and simplified installation. The design is developed in such a way as to maximally facilitate the installation of equipment. No errors. The company is proud of its innovative developments, which it implements in the manufacture of devices. So they become more efficient and reliable, but also more expensive.

From these manufacturers, consumers buy three-way valves for underfloor heating, which have already been tested over time. But do not rely only on the quality of equipment, because even the most stable and reliable device will not be able to protect the system if it is installed incorrectly. In doing so, the choice must also be based on the flow capacity of the unit. This parameter should be specified in the technical documentation to the equipment. When designing a system for auxiliary heating of the air masses from below the room, its output, flow capacity, heat loss, etc. must be calculated.д.



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