compact non pressure solar system 1.Certificates: CCC,ISO,CE,KEYMAEK 2.lifetime:15 years , ... . frame: aluminum alloy/galvanized steel 1.5mm5. insulation layer : polyurethane foam 55 mm 6. heat preservation: 72-80 hours 7. hail ... water automatic: with special design, feeding water automatic, and ensure the outlet water as stable temperature.3. Simple system, easy installation and ...