How does a three-way valve work in a gas boiler

Three-way valve, which regulates the distribution of flows in hot water supply, is one of the main components of a dual-circuit boiler. Thanks to such fittings integrated into the autonomous heating system, it is possible to save fuel, increase the equipment’s service life, and protect it from malfunctions. A thermostatic mixing or distributing three-way valve of this type acts as a regulator and serves as a safety element. However, it’s essential to choose the mixing valve wisely; the first one you come across should not be installed. Such a device should match the characteristics of the heating system and have increased functionality.

How does a three-way valve work in a gas boiler

How a three-way valve works

A heated heat carrier is supplied through the inlet of the valve, while a cooled flow exits through the other. This involves mixed water heated to an optimal temperature, which is discharged through the outlet pipe. Inside the valve, directly beneath the regulating element, a thermal sensor is installed—a special container with liquid or gas. Its contents expand under heating and interact with the actuator—this is what drives the mechanism to work.

Components of a three-way valve

A mixing-type three-way valve has three pipes: two inputs and one output. It is through them that the flows of the heat carrier passing through it are regulated and mixed. As a result, it is possible to obtain the working environment with the desired parameters while maintaining the heat carrier flow rate unchanged. The technical characteristics of such equipment fittings should be specified in the technical passport. Under no circumstances should you attempt to combine a part that does not fit in size with a gas boiler. Normal operation of the three-way valve cannot be achieved in the end.

Bronze and stainless steel are used for manufacturing distributing three-way valves. There are also polymer analogs, but they are less common. It can be predicted that their number will increase further, provided that they perform well in operation and do not affect the temperature. For now, traditional solutions are used in the most popular brands such as Navien, Baxi, Protherm.

Purpose of a three-way valve in a gas boiler

It is installed to avoid supplying cold heat carrier into the boiler. Similarly, condensate formation on the internal walls of the combustion chamber is prevented. The temperature of the heat carrier is regulated using a three-way mixing valve. This necessity arises due to the complexity of the heating system and differences in temperature requirements for each specific circuit.

With a three-way valve, it is possible to ensure full control over heating the heat carrier when installing it in a warm floor circuit. For it, the optimal temperature does not exceed 50°C.

The appropriate installation scheme of the three-way valve is selected based on the characteristics of the heating system. The installation of mixing and diverting valves is carried out in the direction from the heat source into the supply pipe, at the point where the valve is connected to the bypass. Such a type of connection allows the circulation of the heat carrier to be provided through a small circle by the regulator or additionally mixed with cooled water. For separating the flows of the circuit, devices are sometimes mounted on the return pipe, at the point where it is connected to the bypass jumper. Installation of a three-way valve in each of the listed situations is carried out together with a circulation pump.

How does a three-way valve work in a gas boiler

Types of three-way valves

There are two types of three-way valves: thermostatic and thermostatic mixing.

The first is represented by a model that operates automatically with the help of a pump. It maintains the required temperature level, and no further human intervention is required. The most functional options are additionally equipped with a safety system. With its help, it is possible to block the flow of a heat carrier of a certain temperature if circulation in any of the incoming pipes suddenly stops. This prevents boiling in batteries.

The three-way mixing valve analog of distributing equipment is equipped with automatic and manual control. The main difference is the need to regularly check the condition of such a heating system, which will eliminate its overheating.

All devices of this type are classified into two major groups: mixing and distributing. The former are indispensable where it is necessary to arrange a low-temperature heating system. They provide the most accurate temperature to a tenth of a degree, and mixing the flows of the heat carrier depends directly on the selected cross-section of such equipment.

Distributing analogs are set to redistribute gases and liquids simultaneously in multiple directions. This allows for effective regulation of heat transfer in the heating system for radiators, for example, when arranging water supply systems and underfloor heating.

Three-way valves are also divided into manual and electric. The former are used quite often; externally, they practically do not differ from traditional ball valves. The difference lies in the installation of three output pipes intended for connection to mains.

Electric three-way valves feature fully automated control and are more commonly used in private homes. Heat distribution using such equipment is as even as possible, and an advanced control system allows regulating the microclimate in each individual room.

What criteria should you pay attention to when choosing a valve?

The device is selected based on specific parameters. These include:

  • Material of construction;
  • Heat carrier volume;
  • Drive modification and circuitry.

Copper and cast iron valves are considered the best. The properties of the device as a whole directly depend on the characteristics of the metals. The volume of heat carrier consumption can be determined by referring to the technical passport or design documentation of the heating system. This parameter should be correlated with the regulator’s throughput capacity. The circuitry will be more complex if a controller is additionally installed on the valve. In this case, not only a two-circuit but also a two-drive mixer will be required. The first will be installed in close proximity to the heat source. The second operates on electricity and is controlled by the controller; it is the latter that transmits signals from the sensor.

How does a three-way valve work in a gas boiler

How to check a three-way valve

If the valve of this type of regulator operates incorrectly, it adversely affects its efficiency. The durability of the boiler itself also suffers. The likelihood of overheating and shutdown increases if the heat carrier is supplied in insufficient volume. It is also necessary to identify such consequences as failure to maintain heating temperature. Checking the distributor three-way valve in a gas boiler is important to learn from the very beginning; in this case, all malfunctions can be detected at the embryonic stage.

To perform such diagnostics, the equipment should be dismantled. Next, the valve drives are checked. For example, an electric drive is diagnosed for integrity of the housing and the presence of power supply. To check the pump and the valve with a hydraulic drive, it is necessary to disassemble the unit and check for any mechanical damage.

The second stage is to check the heating flow distributor. The working elements naturally wear out during operation, and besides, the mechanism is allowed to accumulate small particles of dirt.

The third stage is to check the stem membrane. It should function correctly, with smooth movements in good condition, and minimal force required. It should return to its original position without any jamming.

The fourth stage is to check the seals. Defects manifest in the form of ruptures, deformations, and cracking. Following this diagnostic algorithm allows identifying the most common malfunctions of the three-way valve of a gas boiler.