... is make it natural circulation between the water tank and the collector pipe.2. After the ... natural convect into the water tank, meanwhile cold water in the tank flows down to the vacuum tubes ... is natural to run continuously to heat the water tank. (Solar tube Water heater, unpressurized solar water ... Temperature SiliconElectric heating1.5KW-3.0KWAssistant tank capacity2L,5L,10L,30L,50L,100L,150L etc ...