What is the primary function of a three-way valve in HVAC systems?

The primary function of a three-way valve in HVAC systems is to regulate temperature by controlling the flow of fluid in response to varying demands within different sections of the system. This valve is designed to either mix hot and cold fluids to achieve a desired temperature or redirect the fluid flow within the system to maintain optimal conditions.

In scenarios where maintaining a specific temperature is crucial, the three-way valve adjusts how much of each fluid is sent into the heating or cooling coil, thus influencing the temperature of the air or water that circulates through the system. For instance, if the demand for heating increases, the valve can allow more hot fluid to mix or redirect flow, ensuring proper temperature regulation throughout the space being conditioned.

The other options do not accurately capture the primary function of the three-way valve. While controlling fluid pressure may be a part of the overall system, and isolating sections of the system is more typical of shut-off valves, the main role of a three-way valve focuses on temperature management through fluid flow modulation.