The Vaillant 40 Litre Stackable Buffer (VP R 40/5 PPS) is a purpose-built accessory for the uniSTOR pure and uniSTOR plus standard diameter cylinder range, designed to be installed either above or below the cylinder as part of a heat pump system. Adding 40 litres of open system volume, this compact buffer provides hydraulic separation, stores additional heating capacity for use at peak demand, and helps de-ice the evaporator without relying on back-up heating – all while adding only 415mm to the overall installed height. 40L Nominal Capacity 415mm Height, Insulated 580mm Outer Diameter, Insulated 16kg Net Weight 3 bar Max Operating Pressure 85°C Max Operating Temperature Stackable Above or Below the Cylinder The buffer's compact design allows it to sit either above or below a compatible uniSTOR pure or uniSTOR plus standard diameter cylinder, maximising space efficiency without increasing the system's overall footprint. Standard Diameter Range Only This 40L buffer (VP R 40/5 PPS) is sized for the uniSTOR pure and uniSTOR plus standard diameter cylinders (150–300L). For the slimline cylinder range, use the 30L buffer (VP R 30/5 SLPPS, 8000011534) instead – the two are not interchangeable due to differing outer diameters. Hydraulic Decoupling & Peak Demand Support As well as adding open system volume, the buffer provides hydraulic decoupling between the heat pump and heating circuit, storing heating capacity to smooth out peak demand and supporting evaporator de-icing without requiring back-up electric heating. Maximises Peak Efficiency The additional 40 litres of open system volume helps heat pumps run at their peak efficiency, reducing short-cycling and supporting more stable operation. De-Ices the Evaporator Without Back-Up Heat Stored heating capacity in the buffer can be used to de-ice the evaporator during defrost cycles, removing the need for an electric back-up heater to perform this function. Compact Stackable Footprint Matching the diameter of the standard uniSTOR range and adding only 415mm to the installed height, the buffer is designed to maximise space efficiency within the customer's home. Low-GWP Insulation Insulated with polyurethane foam using a low Global Warming Potential propellant (GWP
