What is the main purpose of a mixing valve in a hydronic heating system?

The main purpose of a mixing valve in a hydronic heating system is to blend hot and cold water temperatures. This blending is crucial for maintaining a consistent and safe water temperature throughout the system. By mixing the water, the valve ensures that the water supplied to the heating fixtures, such as radiators or underfloor heating, reaches the desired temperature without risking scalding or overheating, which could damage the system or lead to discomfort for occupants.

Mixing valves also enhance energy efficiency within the system by enabling precise control of water temperatures. This can help prevent boiler cycling and optimize overall system performance, contributing to better fuel economy and increased comfort levels in the heated space.

In this context, while the regulation of boiler pressure, filtering impurities, and controlling the water flow rate are important functions in hydronic systems, they are not the primary function of a mixing valve.