The control of the useful power delivered by the terminal units to the premises is carried out by regulating the flow rate supplied to the unit. Three-way valves modify this flow by diverting part through another path (bypass). There are two types of three-way valves:
- Three-way diverter valves: They have one input (AB) and two outputs (A) and (B). Its mission in the hydraulic circuit is to divide and direct the flow of water that enters through (AB) in such a way that part of the flow will exit through (A) and the other will exit through (B).
- Three-way mixing valves: They have two inputs (A) and (B) and one output (AB). Its mission in the hydraulic circuit is to mix the water flows that enter through (A) and through (B) in different proportions to give an output flow through (AB).
