An expansion tank is a crucial component in HVAC systems, accommodating the expansion of system water in heating systems, while also serving the functions of maintaining pressure and replenishing water for the system.

Expansion tanks are typically made of steel plates, usually in circular or rectangular shapes. Due to the thermal expansion and contraction of water in heating systems, when hot water heats up, the water volume in the system increases. If there is no space to accommodate this expansion, the water pressure within the heating system rises, which can affect normal operation. By allowing the expansion tank to accommodate the water expansion, pressure fluctuations caused by water expansion are reduced, enhancing the safety and reliability of system operation. When the system leaks for some reason or cools down, the water level in the expansion tank drops, replenishing water for the system. The expansion tank also helps stabilize system pressure and expel air released during the water heating process.