... exchanger area,5 years warranty Specifactions of close loop Pre-heating solar water heater1, Main tank is non-pressure, Inter copper ... 14mm, thickness 1.0 mm, length 25~35mm7. hen water flows through the coil, it absorbs heat from the ... of this system, such as electric heater, assistant tank, controller, magnesium and etc.11.Passed EN12976 performance testing Compact pre-heated Solar Water Heater