The isolation valves are widely used in the units to control the flow of heating medium through the heating coils.
The used three-way valves can be divided into:
isolation valves (on/off) with the connection with internal thread DN20, DN25 and external thread DN32, DN40. The valves shall be installed only in the supply line, the flow is allowed only in the marked direction AB->A or AB->B.
mixing valves with the connection with external thread V20, V25, V32, V40 and V50. The valves shall be installed in the return line, the flow is allowed only in the marked direction A and B->AB.