gtc-58cc is our pressurized solar water heater,and this model is quite easy installation and well perfomance,and no any skell and no other controller system 1) High pressure with copper coil for hot water consumption 2) Solves the scale problem of bad quality water, since the water in the tank is not for consumption, but only provides heat transfer 3) Anti-freezing design 4) High performance of heat exchanger 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: 1.5mm thick stainless steel 9) Collectors may be connected in series to increase water heating capacity 10) Easy plug-in installation