copper coil solar water heater 1) Designed to accept mains pressure cold water 2) Copper coil heat exchanger can be used as part of a closed or open loop system, providing heating to a main hot water tank 3) Freezing is of minimal concern for SFD series 4) Reliable, efficient, twin-glass solar tubes 5) Superior heat preservation with 50 - 65mm polyurethane tank insulation 6) Outer tank material: stainless steel plate or powder coated color steel sheet 7) Inner tank material: a) 0.5mm thick SUS304 food grade stainless steel plate b) High purity copper for the heat exchanger coil 8) Frame material: 1.2mm thick all stainless steel 9) Collectors may be connected in series to increase water heating capacity 10) Easy plug-in installation