Buffer, Expansion, and TES Vessels in Data Center Plants: Roles Compared A chilled-water plant has several vessels that are easy to confuse: the buffer tank, the expansion tank, and the TES vessel. They solve different problems and are sized by different rules. Mixing them up leads to wrong volumes and wrong specs. This article compares the three so you can specify each correctly. In a data center chilled-water plant, the buffer tank prevents chiller short-cycling, the