Solar Unvented Hot Water Cylinders

Solar indirect hot water cylinders have two heating coils-in-coil heat exchangers, with the primary coil connecting to a solar thermal system as the main heat source and the secondary coil connecting to a conventional gas, oil or electric boiler, to provide heat when there is insufficient solar energy available. The cylinders also feature a 3 kW immersion heater that can act as a secondary back-up or a boost.