... and spare parts for free Compact Non-pressure Solar Water HeaterWorking principle:The non-pressure thermosiphon systems rely ... 80 hours 7. hail resistance: 25mm8. Optional: heat exchanger (red copper), electric heater (1.5kw, 2kw, 2.5kw, 3kw), ... water automatic, and ensure the outlet water as stable temperature.3. Simple system, easy installation and low price. compact non-pressure solar water heater ...