... ,ISO certification high efficient,stable performance, it is widely used flat plate solar water heaterWorking principle:There have three parts of ... color steel or Stainless steel.3.Insulation: 55--60mm imported PU.4.Copper coil:15m-20m each, diameter 12mm,thickness 1mm ... -freeze:-35C6.Capacity:100L,150L,200L,250L,300L,400L,500L flat plate solar water heater