What is a buffer tank for a chiller?

What is a buffer tank for a chiller? A buffer tank for a chiller is a water-filled vessel installed within a chilled-water system to increase the total volume of water circulating between the chiller and the cooling equipment. It is commonly used with air-cooled and water-cooled chillers serving fan-coil units, air-handling units, process equipment or other cooling circuits.

The main purpose of the buffer tank is to provide additional thermal mass. Many modern chilled-water systems contain relatively little water, particularly where short pipe runs, small coils and two-port control valves are used. Without sufficient water volume, the chiller may reach its set temperature too quickly and switch off before restarting shortly afterwards. This is known as short cycling.

Frequent short cycling can reduce system efficiency, create unstable chilled-water temperatures and increase wear on compressors, contactors and other chiller components. A properly sized buffer tank holds a certain amount of chilled water, which lets the chiller run for longer and more stable periods of time.

A buffer tank may also help maintain consistent flow and return temperatures during sudden changes in cooling demand. In some designs, a four-port buffer tank can provide hydraulic separation between the chiller’s primary circuit and the building’s secondary distribution circuit. This allows the pumps on each side to operate at different flow rates without interfering with one another.

Our full range of chilled water thermal storage tanks are detailed here – Chilled water buffer tanks

Chiller buffer tanks are normally insulated and vapour-sealed to prevent heat gain, surface condensation and water damage. The required capacity depends on the chiller output, minimum compressor run time, system temperature difference and the existing water volume in the pipework and equipment. For sizing advice for a chilled water buffer tank or vessel, please see this webpage – Chilled water buffer tank sizing guide