What is a heat pump volumiser?
What is a heat pump volumiser? A heat pump volumiser is a small water-filled vessel installed within a heat pump heating system to increase the total volume of water available in the circuit. It is commonly used where the existing pipework, radiators, underfloor heating loops or fan-coil units do not contain enough water to meet the heat pump manufacturer’s minimum system volume requirement and ensures the heat pump has enough water energy to complete its outdoor defrost cycles.
The main purpose of a volumiser is to provide additional thermal mass. This helps the heat pump run for longer, steadier periods and reduces frequent switching on and off, known as short cycling. Short cycling can lower efficiency, increase electrical consumption and cause unnecessary wear on the compressor and other components.
A volumiser can also provide stored heat during an air-source heat pump’s defrost cycle. During cold weather, the heat pump may temporarily reverse its operation to remove ice from the outdoor unit. The additional water volume helps supply the energy required for defrosting without causing a significant drop in the indoor heating temperature.
Volumiser versus a Buffer Tank
Volumiser:
Unlike a four-port buffer vessel, a volumiser is usually a two-port vessel connected in series within the heating circuit, generally on the return pipework to the heat pump. Water flows directly through it, and it does not normally provide hydraulic separation between the heat pump circuit and the heating distribution system.
A volumiser may be installed in either the flow or return pipe, although the correct position depends on the heat pump manufacturer’s instructions and the system design. It should be properly insulated and located where it remains in circulation during normal operation.
The required volumiser capacity must be calculated from the heat pump output, minimum run time, temperature difference and the existing water volume within the system.
Buffer Tank:
Conclusion
Our most popular demand we have for household/domestic-size heat pumps is our 50-litre volumiser/buffer tank – this unit has its own dedicated webpage here – 50 litre buffer tank – wall or floor-mounted in stainless steel
