3rd Class Power Engineering (3A2) 2026 – 400 Free Practice Questions to Pass the Exam

A mixing valve is designed to blend two or more different fluid streams to achieve a desired temperature or pressure. In most heating and cooling systems, a common configuration for a mixing valve includes two inlets—one for a hot fluid and another for a cold fluid. These inlets allow the valve to control the flow rate of each fluid, effectively mixing them to obtain the appropriate output temperature.

When water, for example, is cooled or heated, it's essential for efficient system operation that these two inlets work together to produce the required temperature for a downstream application, such as in radiant heating or domestic hot water systems. Thus, the standard design of a mixing valve includes typically two inlets, making this the correct answer.