In a large home, the cylinder is not a background component. It is the determining factor in whether hot water supply keeps pace with demand. Specifying for this environment means focusing on three things: stored volume, heat transfer efficiency, and recovery speed.
For an indirect cylinder connected to a gas system boiler, a minimum of 250 litres is recommended for a four-bedroom property with two bathrooms.
At 300 litres, a high-performance indirect cylinder can sustain back-to-back showers and a bath draw without meaningful recovery interruption, provided the coil surface area is sufficient to transfer heat at an adequate rate.
The OSO Super Coil S2C is purpose-built for this application. Available up to 300 litres, it features a generously proportioned smooth heating coil for rapid heat transfer, all pipework and G3 safety components concealed under a single lid using OSO’s patented S-Design, and a factory-fitted INCOTEC backup immersion heater for periods when the boiler is offline.
Installation time is reduced by up to 70% compared to conventional indirect cylinders — a significant advantage in larger properties where the cylinder is often located at a distance from the boiler.
Where energy efficiency is the primary performance metric, the OSO Delta Coil (DC) takes the benchmark further. Its Vacuum Insulation Panel (VIP) technology achieves the lowest standing heat loss of any comparable indirect cylinder available, holding stored water at temperature for longer and reducing the frequency and duration of recovery cycles.
Available at 150 and 210 litres, the DC is best paired with a 250–300 litre S2C in a twincylinder configuration for very large properties with exceptional hot water demand.