What does a chilled water buffer tank do?

We often get asked, ‘What does a chilled water buffer tank do?’ A chilled water buffer tank acts as a “thermal battery or store” by adding extra water volume to a system. Its primary purpose is to prevent the chiller from rapidly turning on and off (short-cycling), stabilise fluctuating return water temperatures, and ensure consistent temperature control.

Chiller short-cycling prevention

When the cooling load of a building is low, the chiller can quickly meet the load and turn off. It will then switch back on shortly as the load increases. The rapid starting and stopping will wear out the compressor and cause spikes in energy use. The buffer tank increases the volume of water in the system and makes the chiller run and rest longer.

Stabilise water temperatures

The extra thermal mass absorbs rapid variations in the temperature of returning water. This evens out the temperature fluctuations before the water hits the chiller. And it stops the system from operating erratically.

Sizing Guidelines

Most chiller manufacturers recommend a total system volume in the region of 3.2 litres to 10.8 litres per kW of nominal cooling capacity depending on the precision of temperature control required. If the volume in the pipework and equipment does not suffice for this purpose, then a buffer tank is installed to make up the difference. Our range of buffer tanks or vessels for chilled water systems are detailed here – Chilled water buffer vessels