A buffer tank is a water vessel that increases the system's hydraulic volume and can help with operational stability.
Limiting frequent starts
If the system has a small water volume or many zones that close, the heat pump may experience frequent start-stops. The buffer can reduce this phenomenon.
Hydraulic separation
In certain configurations, it helps to separate the heat pump circuit from the fan coil or underfloor heating circuits.
It is not always necessary
The need depends on the minimum required water volume, the control logic, and the manufacturer's instructions.
Correct sizing
An overly large or incorrectly connected buffer can increase losses and slow down the system's response.