How does a buffer vessel work?

How does a buffer vessel work? A buffer vessel or buffer tank is a water-filled vessel that is installed in a heating or cooling system to increase the amount of water in the system and to store an amount of thermal energy.

When the heat source (heat pump, electric boiler, biomass boiler or conventional boiler) is operating, it heats the water inside the buffer. This warm water can then be cycled around the heating system when required. In a cooling system, the same principle applies, but the vessel stores chilled water instead.

One of the primary purposes for having a buffer vessel is to stop the heat or chilled water source being turned on and off too often. This starting and stopping over and over is known as short cycling. Short cycling decreases efficiency, increases wear and tear on components and shortens the life of equipment such as heat pump compressors.

By increasing the amount of water in the system, the buffer vessel allows the heat or chilled water source to operate for longer, steadier periods. It also provides stored heat when the heating demand is lower than the minimum output of the heat or chilled water source.

Our full range of buffer vessels are shown on this webpage: Buffer Vessels or we talk about specific buffer vessel applications here – Buffer vessels for heat pumps and Chilled water buffer vessels 

Hydraulic separation 

A buffer vessel can also provide hydraulic separation between the heat-source circuit and the heating-distribution circuit. This means that each circuit can operate at its own flow rate without one pump interfering with another. This is particularly useful in systems with multiple heating zones, underfloor heating circuits or several circulation pumps.

Multiple pipework connections on vessels

Often buffer vessels are provided with two, four or even eight pipe connections depending on the vessel size. The connection arrangement impacts the water flow through the vessel and whether it is used mostly for additional system volume, hydraulic separation or a combination of these.

Normally, a buffer vessel does not generate heat by itself. Its function is to hold and control heated or cooled water, increase system stability, reduce cycling and allow the heating or cooling equipment to run more efficiently.