What is the function of a thermal expansion tank in a hydronic system?

The function of a thermal expansion tank in a hydronic system is to absorb excess pressure that results from the expansion of water when it is heated. As water is heated, it expands; this increase in volume can create pressure within a closed system. Without a means to relieve that pressure, it could lead to potential failures in the system components, such as pipes or valves.

The thermal expansion tank is designed specifically to accommodate this expanded volume of water. It typically includes a bladder or diaphragm that separates the water from a cushion of air, allowing the extra volume to push into this air-filled space when the water expands. This action helps maintain a consistent pressure within the system, ensuring safe and efficient operation.

In a hydronic heating system, managing pressure is crucial for preventing damage and ensuring that the system functions correctly over time. By effectively absorbing excess pressure, the thermal expansion tank plays a vital role in the overall integrity and longevity of the heating system.