What is the function of a pressure relief valve on a closed loop hydronic heating system?

The function of a pressure relief valve on a closed loop hydronic heating system is to protect the system from over-pressurization, which can damage components and create a safety hazard. A closed loop hydronic heating system circulates water or a water-glycol mixture through a closed piping network to distribute heat. As the water is heated, it expands, increasing the pressure within the system. A pressure relief valve is a safety device that automatically opens and releases fluid when the system pressure exceeds a pre-set limit. This prevents the pressure from building up to dangerous levels. The released fluid is typically discharged to a drain. Common causes of over-pressurization include thermal expansion, malfunctioning expansion tanks, and overfilling of the system. The pressure relief valve is a critical safety component that prevents catastrophic failures, such as burst pipes or damaged equipment. The relief valve's set point should be below the maximum pressure rating of the weakest component in the system.