The purpose of a 3-way control valve is to shut off water flow in one pipe while opening water flow in another pipe, to mix water from two different pipes into one pipe, or to separate water from one pipe into two different pipes.
The 3-way valve is characterized by three ports A, B and C. The valve is normally defined by its kvs [m3/h] value, which expresses the volume of water that passes through the fully open valve in 1 hour with a pressure differential of 1 bar.
In a mixing loop, a 3-way control valve can be used to control and regulate heating or cooling surfaces, radiator systems, floor heating/cooling, etc.. This can work in several ways: 1.) The fluid flows in through port A and flows out through port B and C or through port B or C. 2.) The fluid flows in through port B and C or B or C and out through port A.
A 3-way valve is normally provided with an electrical, pneumatic or thermal actuator.