The size of a closed-type expansion tank should be based on what?

The size of a closed-type expansion tank is primarily determined by the capacity of the hot-water heating system. This is because the expansion tank is responsible for accommodating the increase in water volume that occurs as the water is heated. The expansion tank must be adequately sized to ensure that the system can maintain proper pressure and prevent potential damage or leaks as the water expands with temperature.

By basing the size on the system's capacity, which is typically measured in gallons or BTUs, the expansion tank can effectively manage the thermal expansion and contraction of water in the heating system. This is essential for the efficient and safe operation of the system.

Considering other factors, while pressure, flow rate, and temperature may influence the overall performance of a heating system, they do not directly determine the sizing of the expansion tank as effectively as the capacity does. Hence, focusing on the hot-water heating system's capacity leads to a more reliable and effective installation of the expansion tank.