Is the DualSun solar station equipped with a non-return (or anti-thermosyphon) valve?

Yes, the DualSun SLL solar station is equipped with anti-thermosyphon check valves on each hydraulic line, as specified in the data sheet.

• When the pump is activated, the valves only allow the fluid to flow in the normal direction indicated by the arrows.
  The cold water rises through the blue pipe, is heated by the solar panels and returns to the hot water tank through the red pipe.
  
  
• When the pump is switched off, the heat transfer medium in the hot water tank may be warmer than in the solar panels, a thermosyphon effect may occur. 

Check valves and anti-thermosyphon check valves prevent the medium from flowing in both directions.

Note: In the normal flow direction, with the dampers in the closed position by default using springs, the minimum opening pressure is 200mmWG. As the solar station is equipped with two non-return valves, the minimum pressure required for circulation is 400mmWG.