... heat pump 1.Guarantee:15years 2.Certificate:SRCC,CE,Solar Keymark,ISO 3.Deliver time:Within 3days water ... vacuum tube length:47/1500mm,58/1800.2,vacuum tubes:15pcs,18pcs,20pcs,24pcs,30pcs3,Outer tank material: ... many residentbuildings.Working principle:1,The high quality vacuum tubes ansorb the solar ultraviolet ray;then heat the cold ... close the valve automatically solar water heat pump(CE,CCC,ISO)