How does a three-way valve work

The principle of operation of a three-way valve involves splitting the circulation loop into a circuit with a constant and variable hydraulic regime. Consumers requiring high-quality regulation are connected to the port with a constant hydraulic regime, while branches with quantitative regulation are connected to ports with a variable regime.

The main difference in the operation of three-way valves compared to two-way valves is that the flow rate through the port with a constant hydraulic regime practically does not change at any position of the stem - the valve cannot stop the supply of the heat transfer fluid. The port with a constant hydraulic regime is indicated by the letters AB on the diagrams, while the ports with a variable regime are indicated by the letters A and B.

To simplify the understanding of the principle of operation of a three-way valve, it can be replaced by two two-way valves that work reversibly, that is, opening one valve leads to the closing of the other. In the diagram, the mixing three-way valve is replaced by two two-way valves.

All three-way valves are divided into those that mix two flows and those that separate the flow based on their principle of operation.

Mixing three-way valve - has two inputs and one output. It is used for high-quality regulation in heating systems by mixing two flows of the heat transfer fluid with different temperatures. High-quality regulation with maintaining the specified temperature of the heat transfer fluid exiting from port AB is achieved by changing the proportion between the heat transfer fluid supplied from ports A and B. Some types of mixing three-way valves, with the corresponding installation scheme, provide for flow separation.

Separating three-way valve - has one input and two outputs. It is usually used for quantitative regulation by distributing the flow of the heat transfer fluid in schemes for heating water in hot water supply systems, as well as in nodes for connecting air heaters and coolers. The input of the separating valve is indicated by the letters AB, and the outputs - A and B.

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