Three-way valve on the heating system: operation, selection rules, diagram and installation

Alexey Dedyulin
Checked by a specialist: Alexey Dedyulin
Author: Lydia Korzheva
Last update: March 2019

To constantly maintain a comfortable thermal balance in the house, an element such as a three-way valve on the heating system that evenly distributes heat to all rooms is included in the heating circuit.

Despite the importance of this unit, it does not differ in complex design. Let's look at the design features and principles of operation of the three-way valve. What rules should be followed when choosing a device and what nuances are present in its installation.

Features of a three-way valve

Water entering the radiator has a certain temperature, which is often not possible to influence. The three-way valve adjusts by changing not the temperature, but the amount of liquid.

This makes it possible, without changing the area of ​​the radiator, to supply the necessary amount of heat to the rooms, but only within the boundaries of the system power.

Separation and mixing devices

Visually, a three-way valve resembles a tee, but performs completely different functions. Such a unit, equipped with a thermostat, belongs to shutoff valves and is one of its main elements.

There are two types of these devices: separation and mixing.

The first is used when the coolant needs to be fed simultaneously in several directions. In fact, the assembly is a mixer that forms a stable flow with a set temperature. Mount it in a network through which heated air is supplied, and in water supply systems.

Three way valve
The three-way valve is used both as a mixer and as a distributor of air or warm water

Products of the second type serve to combine flows and their thermoregulation. For inlet streams having different temperatures, two holes are provided, and for their exit - one.They are used when installing underfloor heating to prevent surface overheating.

A three-way valve and temperature controller are available separately. For autonomous heating systems, nevertheless, the purchase of a design with a thermostat is considered a more rational and effective solution.

The design of three-way cranes

By design, the valves are divided into seat and rotary. The principle of operation of the first is based on the rhythmic movement of the rod vertically - the "stem-saddle" adjustment scheme. This view applies to mixing valves. Often the control is carried out by an electromechanical drive.

A key element of the pivot structure is the rotating sector. During movement, the stem acts on the ball valve, and it partially or completely cuts off the flow of coolant. This adjustment pattern is called a “ball-socket”.

These devices have increased wear resistance. They are adapted to large temperature differences and are classified as valves. In private homes, where water is consumed in relatively small quantities, they can function as mixers.

A feature of the mixing valve is the presence of one outlet and two inlets. It is designed to control the temperature of the working fluid by combining high and low temperature flows. With appropriate installation, the product can also separate streams.

Three-way crane operation
Here, the operation of a three-way crane of a saddle mixing and separation type is shown schematically

The three-way valve of the separation type is used when it is necessary to supply hot coolant in several directions.

All models of such cranes differ from each other in some ways:

  • shutter mechanics - it can be either tension or stuffing box;
  • stub shape - there are L, T, S-shaped;
  • shutter type - there is a cylindrical, spherical, conical;
  • circuit connection - using a coupling, flange, by welding, etc .;
  • way of managing - automatic, semi-automatic, manual.

The mixing device is equipped with a rod located in the center, a ball valve in it alone. It closes at the right time the shutter of the inlet.

In split type devices, the stem is equipped with two valves mounted in the outlet pipes.

It functions in a slightly different way. The operation of the three-way valve after a detailed analysis of its design becomes clearer.

Detailing of a three-way crane
The components of the three-way valve are: body (1), valve insert (2), valve cone (3), polished valve stem (4), valve seat (5), discharge chamber (6), stuffing box seal (7)

The case of this type of product is cast. It is made of brass or bronze with galvanic nickel plating. It performs both protective and decorative functions. To connect to the pipeline there are threaded bends - only three pieces. The type of threaded connection depends on the model selected.

The optimum pressure in the heating system for stable valve operation is 10 kg / cm². Exceeding this value may cause problems.

There are restrictions on temperature indicators - 95º for boilers, 110º - for solar panels. Permissible temperature control of the coolant in different models is in the range of 20-60º. Productivity ranges from 1.6–2.5 m3/ h

The principle of operation of the device

By installing a three-way mixing valve, it is possible to ensure that the temperature of the liquid at the outlet has a value within the established limits.

The principle of operation for the closed heating system, and for the FGP system is the same. The only difference is that in the first case, the coolant evenly transfers heat from the source to the radiators, and in the second, it transfers warm water to household appliances.

Until the temperature-sensitive element reaches a certain temperature, the coolant is supplied from the front pipe and arrives unhindered to the right. When the working element reaches a temperature higher than the set value, it expands.

This entails moving the valve vertically downward and, as a result, blocking the entry path of the heated coolant from below. Next opens the left pipe for supplying cold liquid.

Valve connection diagram
The diagram shows the procedure for connecting a three-way valve to an autonomous heating system. If it is absent, condensation may form in the return circuit as a result of a decrease in temperature

Mixing a cold liquid with a hot one balances the temperature. The temperature-sensitive element takes its previous shape, and the damper - its original position.

If the three-way valve is installed in the return circuit, then the process should occur in the opposite sequence. When the liquid cools, a direct path opens for hot water from the boiler.

Drive gear

The type of actuator may also be different for the valves. The drive can be either hydraulic or electromechanical, pneumatic, manual.

The electromechanical drive is divided into types, the most common of which is a simple thermostatic. It functions as a result of expansion of a liquid with a thermoactive element in its composition. The result is pressure on the stem. This is an easily removable design used in products installed in household systems.

The next option is a drive with a thermostatic head equipped with a temperature sensitive element. The device is supplemented by a remote temperature sensor located directly in the pipeline. A capillary tube connects it to the drive.

This type of adjustment is considered the most accurate. If desired, a simple thermostatic drive can easily be replaced with a thermostatic head.

Three way valve actuator
For an electrically operated valve, the triggering mechanism may include electromagnets, servos, based on low-power motors or transmission systems

There is an option for a three-way valve with an electric actuator. It is controlled by a controller equipped with temperature sensors and issuing commands to the main mechanism. A simplified version of a drive with a controller is a servo drive.

It controls the valve directly. The simplest drive is manual. Here, the adjustment is carried out by turning the plastic cap having a threaded connection. Its bottom is in contact with the end of the rod. By twisting or unscrewing the spool is moved.

The presence of an electric or servo drive allows you to program the temperature mode with the time of day orientation. Initially, a three-way valve does not include a drive mechanism. It is purchased separately based on the characteristics of a particular heating system. You can use the product in any heating system.

Where are three-way valves used?

There are valves of this type in different designs. They are included in the wiring diagram. warm floors to ensure uniform heating of all its sections and eliminate overheating of individual branches.

In the case of a solid fuel boiler, condensation is often observed in its chamber. Installing a three-way crane will help to deal with it.

Valve in the system Underfloor heating
The valve integrated in the “warm floor” system is responsible for maintaining the temperature at the desired level, mixing small portions of hot water with the coolant

A three-way device works effectively in the heating system, when there is a need to connect the DHW circuit and separate the heat fluxes.

The use of a valve in the radiator harness eliminates the need for bypass. Installing it on the return creates the conditions for a short circuit device.

The nuances of choosing a fixture

The following recommendations are common when choosing a suitable three-way valve:

  1. Preferred reputable manufacturers. Often, low-quality valves from unknown companies are found on the market.
  2. Copper or brass products have greater wear resistance.
  3. Manual control is more reliable, but less functional.

The key point is the technical parameters of the system in which it is supposed to be installed. Such characteristics are taken into account: pressure level, maximum temperature of the coolant at the installation point of the device, allowable pressure drop, volume of water passing through the valve.

Only a valve with the right throughput will work well. To do this, you need to compare the performance of your plumbing system with the bandwidth coefficient of the device. It is mandatory marked on each model.

For rooms of limited area, such as a bathroom, it is irrational to choose an expensive valve with a thermal mixer.

On large areas with underfloor heating, a device with automatic temperature control is required. A guideline for selection should also be product compliance. GOST 12894-2005.

The cost can be very different, it all depends on the manufacturer.

In country houses with installed solid fuel boiler the heating circuit is not very complex. A three-way valve of a simplified design is quite suitable here.

It operates autonomously and does not have a thermal head, sensor, or even a rod. The thermostatic element that controls its operation is tuned to a specific temperature and is located in the housing.

Three-way instrument manufacturers

There is a large assortment of three-way valves on the market from both reputable and unknown manufacturers. The model can be selected after the general parameters of the product are determined.

The first place in the ranking of sales is occupied by the valves of the Swedish company Esbe. This is a fairly well-known brand, so three-way products are reliable and durable.

Esbe Three Way Valve
Esbe three-way valve of mixing type is used both in heating and cooling systems. They can be adjusted manually or automatically.

Korean consumers are known for their quality three-way valves. Navien. They should be purchased in the presence of a boiler of the same company.

Greater adjustment accuracy is achieved by installing a Danish device Danfoss. It works completely automatically.

Valves are distinguished by good quality and affordable cost. Valtecmade jointly by specialists from Italy and Russia.

Efficient US company products Hanivel (Honeywell). These valves have a simple design, easy to install.

Product Installation Features

During the installation of three-way valves there are many nuances. Uninterrupted functioning of the heating system depends on their consideration. The manufacturer attaches instructions to each valve, the observance of which will subsequently avoid many troubles.

General installation recommendations

The main thing is to initially install the valve in the correct position, guided by prompts indicated by arrows on the body. Pointers indicate the trajectory of the water flow.

A symbol indicates a forward stroke, B - a perpendicular or bypass direction, AB - a combined input or output.

Based on the direction, there are two models of valves:

  • with a symmetric or T-shaped circuit;
  • with asymmetric or L-shaped.

When mounting along the first of them, fluid enters the valve through the end holes. It leaves through the center after mixing.

In the second embodiment, a warm stream enters from the end, and a cold stream enters from below.The output after mixing the multi-temperature fluid occurs through the second end.

Installation diagram of valve No. 1
The valve installation diagram shown in the photo is used in heating systems powered by a pressure manifold

The second important point when installing the mixing valve is that you cannot position it with the actuator or thermostatic head down. Before starting work, preparation is required: water is blocked in front of the installation point. Next, check the pipeline for the presence of residues in it, which can cause the valve gasket to fail.

The main thing is to choose a place for installation so that the valve has access. You may need to check or dismantle it later. All of this requires free space.

Mixing valve insert

When inserting a three-way mixing valve into the district heating system, there may be several options. The choice of scheme depends on the nature of the connection of the heating system.

When, under the conditions of operation of the boiler, such a phenomenon as overheating of the coolant in the return is permissible, overpressure necessarily occurs. In this case, mount a jumper throttling the excess pressure. It is installed in parallel with the valve mix.

Connection diagram for valve No. 2
This scheme is used when the heating system is connected to a pressureless collector. It is important to choose the right installation option based on the characteristics of your pipeline

The diagram in the photo is a guarantee of quality control of the system parameters. If a three-way valve is connected directly to the boiler, which is most often the case in autonomous heating systems, a balancing valve insert is required.

If we neglect the recommendation regarding the installation of a balancing device, significant changes in the flow rate of the working fluid, depending on the position of the stem, can occur in port AB.

Connection according to the above diagram does not guarantee the absence of coolant circulation through the source. To achieve this, it is necessary to additionally connect a hydraulic isolator and a circulation pump in its circuit.

The mixing valve is also mounted in order to separate the flows. The need for this arises when it is unacceptable to completely isolate the source circuit, but bypassing the liquid into the return is possible. Most often, this option is used in the presence of an autonomous boiler room.

Connection diagram No. 3
The balancing valve is mounted in the pipeline section of the three-way valve connected to the port indicated by B. Its hydraulic resistance must be identical to the boiler resistance

You must be aware that some models may cause vibration and noise. This is due to inconsistent flow directions in the pipeline and the mixing product. Because of this, the pressure on the valve may drop below the permissible value.

Mounting the separation device

When the temperature of the source is higher than the consumer needs, a flow separating valve is included in the circuit. In this case, at a constant flow rate both in the boiler circuit and by the consumer, the superheated liquid will not come to the latter.

For the circuit to work, the presence of both circuits is required the pump.

Based on the foregoing, we can summarize the general recommendations:

  1. When installing any three-way valve, pressure gauges are installed before and after it.
  2. To avoid any impurities, a filter is mounted in front of the product.
  3. The body of the device must not be subjected to any load.
  4. Good regulation must be ensured by inserting in front of the valve devices that restrict the overpressure.
  5. During installation, the valve should not be above the actuator.

It is also necessary to withstand straight sections recommended by the manufacturer before and after the product. Failure to comply with this rule will entail a change in the declared specifications.The warranty on the device will not be valid.

Conclusions and useful video on the topic

Nuances of installation, accounting of which guarantees the correct operation of the valve:

Details of the installation of the valve when installing a warm floor:

A node in the heating system, such as a thermostatic three-way valve, is necessary, but not in all cases. Its presence is a guarantee of rational use of the coolant, which allows to consume fuel economically. Additionally, it also acts as a device that ensures the safe operation of the boiler TT.

Nevertheless, before purchasing such a device, you must first consult about the feasibility of its installation.

If you have the necessary experience or knowledge on the topic of the article and you can share it with visitors to our site, please leave your comments, ask questions in the block below.

Was the article helpful?
Thanks for your feedback!
No (15)
Thanks for your feedback!
Yes (71)
Visitors Comments
  1. Alexander

    Guys, the time in the video is 9:25. Where will he take cold water to dilute the temperature of the coolant in the warm floor to the desired value, if you have a check valve there (he must take the water from the return for dilution)